Reduction of NOx and N2O contents in off-gas from calcination plants operated with NH3

Abstract

The present invention relates to the catalytic decomposition of NH3 into N2 and H2 by catalytic decomposition of NO3 in the off-gas (flue gas) from a calcination plant operated with NH3. X and N2O content. For this purpose, the calcination plant preferably comprises combustion means for burning NH3 to generate combustion heat, and NH3 decomposition means for catalytically decomposing NH3 to produce N2 and H2 in heat exchange with the combustion means. The heat required for catalytic decomposition of NH3 in the NH3 decomposition means is provided by the combustion of NH3 in the combustion means. The combustion means preferably comprises at least one burner and a combustion space. The calcination plant is preferably configured similarly to a primary reformer.

Description

[Technical Field]

[0001] Priority is claimed from European Patent Application No. 22216421.2, filed December 23, 2022, European Patent Application No. 23165192.8, filed March 29, 2023, and German Patent Application No. 102023118563.2, filed July 13, 2023.

[0002] The present invention relates to the detection of NO in the off-gas (flue gas) of an NH3-operated calcination system incorporated into a system for catalytic decomposition of NH3 into N2 and H2. X and reduction of N2O content. [Background technology]

[0003] For this purpose, the calcination system preferably comprises a combustion device in which NH is combusted to generate combustion heat, and an NH decomposition device in heat exchange with the combustion device, in which NH is catalytically decomposed into N and H. The heat required for the catalytic decomposition of NH in the NH decomposition device is provided by the combustion of NH in the combustion device. The combustion device preferably comprises at least a burner and a combustion chamber. The calcination system is preferably configured similarly to a primary reformer.

[0004] H2 can be obtained from H2O using renewable energy and then converted to NH3 using N2. NH3 can be stored and transported much more safely than H2. NH3 can then be decomposed again into H2 and N2. H2, after being separated from N2, finds a wide range of industrial uses.

[0005] The decomposition of NH3 into N2 and H2 is an endothermic reaction (ΔH° = 45.9 kJ mol) in which the molar amount doubles (2NH3 ⇔ N2 + 3H2). -1), the reaction is generally favored at high temperatures and low pressures. The higher the pressure, the higher the temperature must be to achieve a satisfactory reaction yield. Numerous materials have been proposed as catalysts for the decomposition of NH3, and these materials are active at different temperatures (see, for example, Il. Lucentini et al., Ind. Eng. Chem. Res. 2021, 60, 18560-18611).

[0006] The catalytic decomposition of NH3 yields a product gas containing H2 in a mixture with N2 and possibly other gaseous components, such as undecomposed NH3. However, many industrial applications require high purity H2, so purification of the product gas is necessary before the H2 can be delivered to the industrial application. Although H2 scrubbing is possible in principle by various methods, for example by cryogenic membrane methods, scrubbing by pressure swing adsorption is particularly economically feasible on an industrial scale.

[0007] The catalytic decomposition of NH3 to N2 and H2 occurs in the gas phase at high temperatures and moderate pressures. Stored NH3 is in liquid form in a refrigerated tank at atmospheric pressure and -32.8°C. A pump is used to supply NH3 to the system at system pressure. With increasing system pressure, the boiling point of NH3 increases, for example, to about 62.2°C at 27.8 bara. To convert NH3 to the gas phase, evaporation of NH3 requires the supply of heat.

[0008] Conventional processes for the catalytic decomposition of NH3 generate a significant amount of heat that can be used to vaporize the NH3.

[0009] U.S. Patent No. 4,704,267 relates to the production of high-purity H2 from liquid anhydrous NH3. NH3 is vaporized and then split into its components. The resulting dissociated gas stream is fed to an adiabatic metal hydride scrubbing unit to absorb the H2 present in the stream. The adsorbed H2 is then recovered as a high-purity product.

[0010] FR 1 469 045 A1 relates to an apparatus consisting of a preheater supplied with NH3, a shell-and-tube system enclosing a catalyst for cracking NH3, and optionally a cell for scrubbing with H2 by diffusion, connected to one another and present in a single housing containing heating means.

[0011] Chinese Patent No. 111957270 relates to an NH3 decomposition apparatus comprising an NH3 decomposition unit and a combustion unit operating on the NH3 decomposition unit. NH3 enters the NH3 decomposition unit through a first inlet for purified gas to carry out the NH3 decomposition reaction. The resulting mixed gas is discharged through a second outlet for purified gas and then enters the combustion unit through a second inlet for purified gas. The mixed gas contains N2, H2, and undecomposed NH3. The mixed gas enters the combustion unit to provide heat for the NH3 decomposition reaction in the NH3 decomposition unit, achieving self-sufficiency in heat in the H2 production system through NH3 decomposition. No additional fuel is required for energy supply, reducing the cost of the H2 production system through NH3 decomposition.

[0012] Chinese Patent No. 113896168 relates to a process for producing H2 or reducing gas by cracking NH3 through a two-stage process, including the following steps: liquid NH3 in the feedstock is fully gasified and heated by a heat exchange gasification system, and then enters a heat exchange NH3 cracking reaction system in the first stage to cause partial NH3 cracking reaction; the reaction gas from the first stage heat exchange NH3 cracking reaction system enters a high-temperature NH3 cracking reaction system in the second stage to carry out residual NH3 cracking reaction; and the high-temperature NH3 cracking reaction gas from the second stage successively enters the heat exchange NH3 cracking reaction system and the heat exchange gasification system from the first stage to gradually recover heat so as to obtain reducing gas.

[0013] WO 2001 / 087770 relates to the autothermal decomposition of NH3 for the production of high purity H2.

[0014] WO 2011 / 107279 relates to an NH3-based H2-producing reactor comprising an NH3 cracking chamber with an NH3 cracking catalyst, an internal combustion chamber with a combustion or oxidation catalyst in thermal contact with the NH3 cracking chamber, an NH3 gas preheating chamber, and an outer shell ring for recovering heat from combustion products exiting the combustion chamber, wherein the cracking chamber, internal combustion chamber, preheating chamber, and heat recovery shell ring are in a concentric arrangement.

[0015] WO 2017 / 160154 relates to a method for generating energy in a gas turbine, the method comprising the steps of: (i) evaporating and preheating liquid NH to produce preheated NH gas; (ii) introducing the preheated NH to an NH cracking unit suitable for converting the NH gas to a mixture of H and N; (iii) converting the preheated NH in the unit to a mixture of H and N; (iv) cooling the mixture of H and N to obtain a cooled mixture of H and N; (v) introducing the cooled mixture of H and N into a gas turbine; and (vi) combusting the cooled mixture of H and N in the gas turbine to produce energy.

[0016] WO 2019 / 038251 relates to a method for producing an N2- and H2-containing product gas from NH3, the method comprising the steps of non-catalytic partial oxidation of NH3 with an O2-containing gas to give a process gas containing N2, water, a certain amount of nitrogen oxides, and a residual amount of NH3, cracking at least a portion of the residual amount of NH3 in the process gas to H2 and N2 by contacting the process gas with a nickel-containing catalyst while simultaneously reducing a certain amount of nitrogen oxides to N2 and water by reaction with a portion of the H2 formed during cracking of the process gas by contacting the process gas with the nickel-containing catalyst, and withdrawing the H2- and N2-containing product gas.

[0017] WO 2012 / 039183 relates to an NH3 decomposition unit that produces H2 as a combustion improver, and an NH3 oxidizer that reacts a portion of the introduced NH3 with O2 using an oxidation catalyst, resulting in combustion to provide the heat required for the NH3 decomposition reaction.

[0018] WO 2012 / 090739 relates to an H2 generator including a decomposition device that decomposes a compound containing hydrogen atoms and nitrogen atoms to generate H2, a compound supply device that supplies the compound to the decomposition device, and an O2 supply device that supplies O2 to the decomposition device.

[0019] WO 2020 / 095467 relates to an apparatus for producing H2 gas, including an NH3 evaporation device that heats liquid NH3 to produce NH3 gas; a main apparatus for thermal decomposition that results in combustion of a fuel gas, in which the NH3 gas produced by the NH3 evaporation device is heated and decomposed into N2 gas and H2 gas; a cooler that cools gas produced by the decomposition, including N2 gas and H2 gas, produced by the decomposition in the main apparatus for thermal decomposition; and a separator that separates H2 gas from the cooled gas produced by the decomposition.

[0020] WO 2021 / 257944 relates to the recovery of H from an NH cracking process in which the cracking gas is scrubbed in a PSA unit. The use of a membrane separator for the PSA off-gas improves recovery.

[0021] WO 2022 / 096529 relates to a method for cracking NH3 for the production of H2 and electric current, which includes electrolysis of water in a supply of NH3, evaporation, preheating, and cracking of NH3 using an NH3 synthesis catalyst at low temperature.

[0022] WO 2022 / 243410 relates to a method for synthesizing H2 by catalytic cracking of NH3, in which an NH3-containing stream is subjected to a catalytic cracking step in the presence of heat, with or without water, to obtain combustion gases and a thermally cracked stream containing N2, H2 and possibly residual NH3, and the thermally cracked stream is subjected to an H2 recovery step to obtain a high-purity H2 stream.

[0023] WO 2022 / 265647 relates to the recovery of a renewable H2 product from an NH3 cracking process in which the cracked gas is purified in a first PSA unit to reduce the carbon intensity of the renewable H2 product, and at least a portion of the first PSA tail gas is recycled as fuel.

[0024] WO 2022 / 265648 discloses the selective catalytic reduction (SCR) of NO from flue gas produced in an NH3 cracking process using an aqueous NH3 solution produced by cooling compressed off-gas from an H2PSA unit to scrub the cracked gas. X Regarding the removal of impurities.

[0025] WO 2022 / 265649 relates to reducing the water content of NH3 used in NH3 cracking processes, which allows the use of water-immiscible cracking catalysts. The water removal process can also be used to recover and reuse NH3 from the cracking gas.

[0026] WO 2022 / 265650 relates to an NH3 cracking process in which cracked gas is purified in a PSA system. Residual NH3 in the first cracked gas is converted to additional H2 and N2 by feeding the PSA tail gas or the resulting gas to a secondary cracking reactor and further processing the second cracked gas.

[0027] WO 2022 / 265651 relates to a process in which residual NH3 in an H2PSA system is removed from NH3 cracking gas using a non-zeolitic adsorbent such as activated carbon, activated alumina or silica gel.

[0028] U.S. Patent Application Publication Nos. 2003 / 0143142 and 2017 / 0334722 disclose a method for producing tail gas NO from nitric acid production. X This paper describes methods to reduce N2O concentrations.

[0029] CN Patent No. 114412668 relates to an ammonia-fueled engine, in particular an ammonia-hydrogen fusion hybrid energy system and engine.

[0030] Japanese Patent Application Laid-Open Publication No. 2023-026798, published on March 1, 2023, relates to an off-gas treatment system for an ammonia engine, which includes an oxidation catalyst including a catalyst layer containing Pt and zeolite as a first catalyst, and a denitrification catalyst including a catalyst layer containing zeolite ion-exchanged with Cu, Co, or Fe ions as a second catalyst.

[0031] YK Park, Chemical Engineering Journal, Volume 461, Issue 141958, Published April 1, 2023, is a review article on the catalytic removal of nitrogen oxides (NO, NO2, N2O) from off-gases formed when ammonia is used as a fuel.

[0032] Korean Patent No. 2023-095308, published on June 29, 2023, describes a plant having a catalytic reactor, a liquid ammonia storage tank, and a first distributor that supplies at least a portion of the ammonia supplied from the storage tank to the catalytic reactor as cracked ammonia, and the ammonia supplied to the catalytic reactor is contacted with an ammonia cleavage catalyst to produce nitrogen and hydrogen. A second distributor supplies the residual ammonia that has passed through the first distributor to a denitrification reactor and a mixer.

[0033] NH3 has a relatively low calorific value and a low flame propagation speed, which carries the risk of flame quenching and resulting in incomplete combustion. Furthermore, the combustion of NH3 carries the risk of increased emissions of nitrogen oxides (especially NO, NO2, and NO), which affects its suitability as a combustion gas. For example, gaseous ammonia / hydrogen / air mixtures have been proposed in which a certain hydrogen content, which can be produced by catalytic or thermally assisted NH3 dissociation, is used as a combustion promoter.

[0034] The focus of research to date has been on optimizing the combustion of ammonia itself, particularly with regard to energy yield and economic viability, but also with regard to the formation of undesirable nitrogen oxides. However, the NOx reduction in the combustion process X (i.e., NO and NO2) and N2O production cannot be sufficiently suppressed.

[0035] However, NO that may be present in the combustion gases (e.g., CO, HCN, or even NH3) X Emissions of CO, N2O, and possibly other components should be avoided or at least reduced as far as possible to protect health, the environment, and the climate. Many developed countries have therefore imposed corresponding regulations.

[0036] Furthermore, combustion of hydrocarbons (CH4, natural gas, etc.) in the presence of NH3 produces off-gases that can contain hydrogen cyanide (HCN, hydrocyanic acid). Even small amounts of HCN are problematic because they are classified as highly toxic and correspondingly low limits for HCN emissions into the environment must be monitored. HCN-contaminated off-gases can, in principle, be purified by various means. Alkaline scrubbing operations can form and separate cyanides, but these must be disposed of as highly toxic compounds. Using specific oxidation catalysts based on precious metals, HCN can be converted to CO2, HO, N2, and various nitrogen oxides. However, this implies considerable procedural complexity and cost. For example, the formed nitrogen oxides must be decomposed in a further process step, for example by selective catalytic reduction (SCR). The hydrolysis of HCN through specific catalysts, for example based on TiO2, is also described as follows: HCN + HO → CO + NH3. Subsequent further oxidation over a corresponding separate oxidation catalyst is also required in this case. Therefore, there is a need for a scrubbing process for HCN-contaminated off-gas that features a simple and inexpensive mode of operation and low equipment costs. Furthermore, these processes should convert HCN into non-toxic substances that do not require further treatment.

[0037] A further problem is the incomplete combustion of ammonia, which has the effect that the off-gas from a firing system operating on ammonia as fuel may contain a significant amount of unburned ammonia (called NH3 slip, NH3 breakthrough). The permissible limits for ammonia released into the atmosphere are relatively strict. Therefore, in such cases, it is necessary to ensure that the ammonia is oxidized to nitrogen before the off-gas can be released into the atmosphere. For this purpose, so-called ammonia slip catalysts (ASC) have been developed, which are typically based on precious metals from the platinum group (i.e., Ru, Rh, Pd, Os, Ir, Pt). Such catalysts are not only expensive but also not very selective (i.e., they only convert NH3 to NO Xor N2O), and are susceptible to chlorine and chlorine compounds.

[0038] Therefore, there is no need to worry about the presence in the off-gas of an NH3-operated calcination system for combustion-related reasons so that the off-gas can be discharged into the ambient air in accordance with all environmental regulations. - Nitrogen oxides (especially NO and NO X (i.e., NO and NO2) -excess NH3, and -Other environmentally harmful components of the off-gas (e.g. CO or HCN) Therefore, a means is needed to at least partially remove the

[0039] These calcination systems preferably include a combustion device in which NH3 is combusted to produce heat of combustion, and an NH3 decomposition device in heat exchange with the combustion device in which NH3 is catalytically decomposed into N2 and H2.

[0040] Here, with regard to the operation of a calcination system preferably comprising a combustion device for the combustion of NH3 and an NH3 decomposition device for cracking NH3 into N2 and H2, it is necessary to take into account the specific circumstances resulting from the maximum efficiency of the combustion of NH3. Important parameters are not only the different compositions of the off-gas, but also in particular the pressure and temperature of the off-gas. These parameters affect the NO X and N2O removal strategies have been developed so far that may differ significantly from other off-gas parameters.

[0041] For example, in the industrial production of nitric acid (NH3), NO is reacted with water in an absorption tower to obtain nitric acid from it. X The oxidation is carried out intentionally up to NO. Special catalysts made from noble metals are used for the oxidation, and the reaction is often carried out at high pressure. The purpose of the combustion of NH3 here is to produce NO X The goal is to achieve a maximum yield of 1000 kJ / kg, and the typical water content in the off-gas ranges from about 1% to 3% by volume.

[0042] In contrast, in the operation of a calcination system preferably comprising a combustion device for the combustion of NH and an NH decomposition device for cracking NH to N and H, NH is preferably oxidized only to the N stage in the combustion; in this case, a catalyst is generally not required, and the reaction is usually carried out at atmospheric pressure. The typical water content in the off-gas is well above 3% by volume. For example, the combustion of pure NH in air with a residual oxygen content of 3 mol% results in more than 28 mol% water. The main purpose of the combustion of NH is to generate the energy required for the catalytic decomposition reaction of NH to N and H. A low level of nitrogen oxides in the off-gas formed in the combustion is advantageous in this case because it reduces the level of nitrogen oxides in the flue gas and therefore requires a relatively small off-gas treatment system to meet regulatory requirements for allowable emissions, or because sufficiently low residual concentrations can be achieved using known methods for nitrogen oxide reduction.

[0043] In contrast to conventional off-gas treatment systems, which are used, for example, in the case of off-gas from plants for the production of HNO3, the inventive combustion of NH3, preferably in a mixture with H2, combined with catalytic decomposition of NH3 to H2 and N2, gives special features accompanied by special measures.

[0044] The essential features are, firstly, ambient pressure conditions and, secondly, a very high water content. By "ambient pressure" we mean that the pressure drop may be too high when using conventional catalyst beds, such as those based on beds of particulate matter. Especially in the case of zeolitic materials, the high water content at high temperatures can lead to a gradual deactivation of the catalyst due to the hydrothermal load on the catalyst in the off-gas treatment system. Therefore, the maximum temperature should be limited. Apart from degradation, NO X The chemical reduction of N2O is little impaired by high water content, but the decomposition of N2O by decomposition and / or chemical reduction is severely impaired by high water content.

[0045] A further difference in the off-gas treated according to the present invention compared to the production of HNO3 is the relatively high NO2 content, which can be several thousand ppmv. X Content. NO X The content depends on the conditions in the combustion of NH3, in particular the NH3 content, any other combustible gases present (H2 and / or CH4 (natural gas)) and the air ratio λ. Due to the high temperatures in combustion up to 1000 °C or more, NO X also initially exists almost exclusively as NO, i.e., a very high proportion of NO and a very low proportion of NO2. Even as a result of favorable cooling in downstream heat exchangers, only a small portion of the NO is converted to NO2 due to the slow rate of NO2 formation at high temperatures. This means that when the off-gas enters the off-gas treatment system, NO X The degree of oxidation (β), i.e., the total NO X This means that the molar fraction of NO in the catalyst (β = n(NO) / (n(NO) + n(NO)) is small, typically less than 5 vol.%. This is because the desired selective catalytic NO X This means that reduction may proceed very poorly or slowly, in accordance with normal SCR, which in practice occurs at a slow rate.

[0046] These are the NO and NO absorbers that are released after leaving the "cold" state. X This is a fundamental difference from established off-gas cleaning in HNO3 systems, where the tail gas containing gas is heated stepwise under positive pressure, typically between 4 and 10 bar (thermodynamic NO X (The equilibrium is practically entirely on the side of NO2.) For example, the NO2 tail gas in HNO3 production before entering the corresponding off-gas treatment system X Oxidation levels are typically between 30% and 70% by volume, i.e., NO in very fast SCR. X This is close to the ideal stoichiometric ratio for reduction.

[0047] Therefore, high NO X Very low NO content XThe oxidation level and high water content coupled with the simultaneous low operating pressure (close to atmospheric pressure) pose particular challenges in this case to the effectiveness of the off-gas treatment system of the present invention. Additionally, there is the challenge or need to remove N2O, which is also present in the off-gas and cannot be reduced by conventional SCR processes based on V2O5 / TiO2 catalysts.

[0048] Therefore, the goals and resulting reaction products in the combustion of NH3 can be very different from one another.

[0049] In conventional plants for producing nitric acid, the off-gas is frequently, at relatively high pressure, -Relatively low NO X Content of; -Relatively high percentage of NO2; - relatively high N2O content; -Relatively low water content; and -0% unburned NH3 (NH3 slip) It has.

[0050] In contrast, in a firing system preferably equipped with a combustion device and an NH decomposition device for cracking NH to N and H, the off-gas is frequently generated at relatively low pressures. -Relatively high NO X Content of; -Relatively small proportion of NO2; -Relatively low N2O content; -Significantly high water content; - possibly a non-negligible proportion of unburned NH3 (NH3 slip); and -If NH3 is combusted with CH4 (natural gas), a possibly non-negligible proportion of HCN It has.

[0051] These special circumstances can cause NO from the off-gassing X and N2O removal, which constitutes a particular challenge. [Prior art documents] [Patent documents]

[0052] [Patent Document 1] U.S. Patent No. 4,704,267 [Patent Document 2] French Patent Application Publication No. 1469045 [Patent Document 3] Chinese Patent No. 111957270 [Patent Document 4] Chinese Patent No. 113896168 [Patent Document 5] International Publication No. 2001 / 087770 [Patent Document 6] International Publication No. 2011 / 107279 [Patent Document 7] International Publication No. 2017 / 160154 [Patent Document 8] International Publication No. 2019 / 038251 [Patent Document 9] International Publication No. 2012 / 039183 [Patent Document 10] International Publication No. 2012 / 090739 [Patent Document 11] International Publication No. 2020 / 095467 [Patent Document 12] International Publication No. 2021 / 257944 [Patent Document 13] International Publication No. 2022 / 096529 [Patent Document 14] International Publication No. 2022 / 243410 [Patent Document 15] International Publication No. 2022 / 265647 [Patent Document 16] International Publication No. 2022 / 265648 [Patent Document 17] International Publication No. 2022 / 265649 [Patent Document 18] International Publication No. 2022 / 265650 [Patent Document 19] International Publication No. 2022 / 265651 [Patent Document 20] US Patent Application Publication No. 2003 / 0143142 [Patent Document 21] US Patent Application Publication No. 2017 / 0334722 [Patent Document 22] Chinese Patent No. 114412668 [Patent Document 23] Japanese Patent Publication No. 2023-026798 [Patent Document 24] Korean Patent No. 2023-095308 [Non-patent literature]

[0053] [Non-Patent Document 1] Il. Lucentini et al.,Ind.Eng.Chem.Res.2021,60,18560-18611 [Non-patent document 2] Y.K. Park, Chemical Engineering Journal, Vol. 461, 141958 Summary of the Invention

[0054] The object of the present invention is to provide a method for reducing NO in the off-gas obtained in an NH3-operated calcination system, preferably comprising a combustion device for combusting NH3 and an NH3 decomposition device for cracking NH3 into N2 and H2. X (i.e., NO and NO), N2O, and, if necessary, NH3, CO, and / or HCN. Here, if necessary, a very large amount of NO X And it should be possible to decompose N2O further.

[0055] This object is achieved by the subject matter of the claims.

[0056] A first aspect of the present invention is directed to a method for reducing NO in the off-gas of an NH3-powered calcination system, preferably comprising a combustion device for combusting NH3 and an NH3 decomposition device for cracking NH3 into N2 and H2. X and a method for reducing the content of N2O, the method comprising: (a) Combusting NH3 (which may be mixed with one or more other combustible gases, e.g., H2, CH4, etc.) to preferably operate a calcination system (preferably comprising at least one burner and a combustion chamber) that preferably comprises a combustion device for the combustion of NH3 and an NH3 decomposition device for cracking NH3 into N2 and H2, and producing N2, H2O, NO2, with or without HCN. X generating an off-gas exiting the calcination system comprising NO and N2O; (b) optionally and preferably cooling the off-gas in at least one heat exchanger located downstream of the calcination system in the flow direction of the off-gas; (c) optionally transporting the cooled off-gas to an off-gas treatment system; (d) The NO content in the off-gas is (d1) Decomposing N2O via an N2O decomposition catalyst, and / or (d2) chemically reducing N2O with a reducing agent via an N2O reduction catalyst; and reducing by (e)NO X NO by reducing agents via reduction catalysts X NO in the off-gas by chemical reduction of X Reducing the content; (f) optionally and preferably cooling the off-gas in at least one heat exchanger arranged downstream of the off-gas treatment system in the flow direction of the off-gas; Includes:

[0057] The order of steps (d) and (e) may be as desired, and in accordance with the present invention all options are included, from sequential in time in any order to simultaneous, or a mixture thereof.

[0058] The present invention preferably provides a method for reducing NO in the off-gas of an NH3 and H2 operated firing system, which preferably includes a combustion device for combusting NH3 and an NH3 decomposition device for cracking NH3 into N2 and H2. X and a method for reducing the content of N2O, the method comprising: (a) Combusting NH3 and H2, preferably operating a combustion system comprising a combustion device for combusting NH3 (preferably comprising at least one burner and a combustion chamber) and an NH3 decomposition device for cracking NH3 into N2 and H2, to produce N2, H2O, NO2, and X generating an off-gas exiting the calcination system comprising NO and N2O; (b) optionally and preferably cooling the off-gas in at least one heat exchanger located downstream of the calcination system in the flow direction of the off-gas; (c) optionally transferring the cooled off-gas to an off-gas treatment system arranged downstream of the calcination system in the off-gas flow direction and, if appropriate, downstream of at least one heat exchanger; (d) The NO content in the off-gas is (d1) Decomposing N2O via an N2O decomposition catalyst, and / or (d2) chemically reducing N2O with a reducing agent via an N2O reduction catalyst; and reducing by (e)NO X NO by reducing agents via reduction catalysts X NO in the off-gas by chemical reduction of X Reducing the content; (f) optionally and preferably cooling the off-gas in at least one heat exchanger arranged downstream of the off-gas treatment system in the flow direction of the off-gas; Includes:

[0059] NO in flue gas X Therefore, in the off-gas treatment system, NO is preferably added with a reducing agent, preferably NH3. X The chemical reduction of NH3 generates a significant amount of heat that can be released to a suitable heat transfer medium using one or more heat exchangers. The heat transfer medium used here is preferably water or steam, which has advantages, among other things, in terms of safety. The heat absorbed by the heat transfer medium is then preferably used to heat NH3, which is fed as a feed stream to the NH3 decomposition device. Alternatively or additionally, the heat can also be used to preheat the combustion air.

[0060] Experimental results or simulation calculations show that NO is reduced by a reducing agent, preferably NH3. X It indicates that the heat released in the chemical reduction of heats the off-gas by up to 70 K, preferably 50 K, relatively, i.e. the temperature of the gas leaving the off-gas treatment system is up to 70 K, preferably 50 K, higher than when it enters the off-gas treatment system.

[0061] It was also found that the amount of nitrogen oxides formed from the combustion of NH3 in the off-gas can depend on many factors, including the H2:NH3 mixture ratio, the air ratio λ, preheating of the combustion air, and burner design.

[0062] The catalytic decomposition of NH3 serves to form H2 as a product. Accordingly, a further aspect of the present invention is to provide a method for reducing NO2 in the off-gas of an NH3-powered calcination system, preferably comprising a combustion device for combusting NH3 and an NH3 decomposition device for cracking NH3 into N2 and H2. Xand a method for producing H2 by catalytic decomposition of NH3, including the method of the present invention for reducing the content of N2O and N2O in the off-gas of an NH3 and H2 operated firing system, preferably comprising a combustion device for combusting NH3 and an NH3 decomposition device for cracking NH3 into N2 and H2. X and a method for producing H2 by catalytic decomposition of NH3, including the method of the present invention for reducing the content of N2O.

[0063] The off-gas treatment systems of the present invention may be the same or different according to a given functionality or multi-functionality, and may be present in a common or separate reaction zone (catalyst bed); - N2O reduction catalyst and / or N2O decomposition catalyst, and -NO X reduction catalyst, At least includes.

[0064] In a preferred embodiment, the off-gas treatment devices of the present invention may be the same or different, and may be present in a common or separate reaction zone (catalyst bed), according to a given functionality or multifunctionality. -N2O reduction catalyst, -N2O decomposition catalyst, and -NO X reduction catalyst, Includes:

[0065] In a preferred embodiment, the off-gas treatment system of the present invention further comprises at least one additional catalyst or a catalyst selected from the group consisting of N2O reduction, N2O decomposition or NO2O decomposition catalysts. X One of the reduction catalysts is -NH3 oxidation catalyst, -HCN decomposition catalyst, and -CO oxidation catalyst The at least one further functionality selected from the following is satisfied:

[0066] The NH3 oxidation catalyst preferably has a ratio of unburned NH3 in the off-gas (NH3 slip) to NO in the off-gas treatment system. Xand / or when the demand for NH as a reducing agent for N2O is greater than the demand for NH3, so that the off-gas, after passing through steps (d1) and / or (d2) and (e), still contains residual amounts of NH3 that should not or should not be released to the environment. These residual amounts of NH3 can then be destroyed by oxidation of NH3 using a downstream NH3 oxidation catalyst.

[0067] The HCN decomposition catalyst is preferably used when the fuel contains hydrocarbons (CH, natural gas, etc.) in addition to NH3, and the off-gas formed during combustion contains a certain amount of HCN. The obtained HCN is then decomposed (removed) with the help of the HCN decomposition catalyst by hydrolysis of HCN and oxidation of the produced hydrolysis products (hydrolysates), i.e., NH3 and CO, and preferably NO present in the exhaust gas. X and is decomposed (removed) by N2O.

[0068] Surprisingly, each of them contains more molar amounts of NO than the molar amount of HCN. X It has been found that HCN in a water-containing off-gas, which simultaneously contains HCN and N2O, can be decomposed to N2, HO and CO2 by passing the off-gas over a package of catalyst pellets containing a transition metal-containing zeolite catalyst, for example, an iron-containing zeolite material of the BEA structure type, at a temperature of 300 to 600°C (preferably 350 to 550°C).

[0069] Thus, in contrast to known methods, the complete removal of HCN, i.e., its conversion into non-toxic substances, can be achieved in a single process step, i.e., without the use of expensive noble metal catalysts. X and NO to eliminate N2O X and NH3 for the reduction of N2O, and HCN, NO for N2O X It is further possible to add CO or hydrocarbons, such as CH or propane, for reduction to the N2O- and N2O-containing off-gas. In this case, the amount of reducing agent is determined by the ratio of N2O and NO XIn each case, the molar starting amount of NO should be reduced by the molar amount of HCN present in the off-gas. If an excess amount of NO is present in the off-gas and is reduced with NH or CO or hydrocarbons, the NO X The content should in any case be reduced to 0 (or close to 0) by NH3. If CO or hydrocarbons are used as additional reductants, CO emissions can be eliminated by using an additional CO oxidation catalyst downstream of the zeolite catalyst.

[0070] A CO oxidation catalyst is preferably used when (i) hydrocarbons (CH, natural gas, etc.) are used as a reductant for NO, and / or (ii) an HCN decomposition catalyst is used to decompose HCN and CO is present in the decomposition products. Any CO obtained in each case can then be decomposed by oxidation to CO using a downstream CO oxidation catalyst.

[0071] If the off-gas treatment system of the present invention includes an NH3 oxidation catalyst, it may be preferred according to the present invention to first cool the off-gas in a heat exchanger within the off-gas treatment system to a lower temperature than when it enters the off-gas treatment system, so that the NH3 oxidation catalyst can demonstrate its effectiveness in an optimized manner. Therefore, in a preferred embodiment, the off-gas treatment system of the present invention further comprises one or more heat exchangers.

[0072] For purposes of explanation, "and / or" means either "or" or "and," e.g., "A and / or B" has three meanings: (i) only A but not B, (ii) only B but not A, and (iii) both A and B.

[0073] For purposes of illustration, "NO X " includes nitric oxide (NO) and nitrogen dioxide (NO2), but does not include nitrous oxide (N2O).

[0074] Catalysts speed up certain chemical reactions by lowering their activation energy.

[0075] Unless otherwise stated, all numbers in ppm are by volume, i.e., ppmv. All percentages are by volume, i.e., vol. % with respect to the gas composition, unless otherwise stated. All other percentages are by weight, i.e., wt. % unless otherwise stated.

[0076] Steps (b) and (f) of the method of the present invention are independently optional and preferred.

[0077] Steps (a), optionally (b), and (c) of the method of the present invention are carried out consecutively in alphabetical order, followed by steps (d) and (e) in essentially any order. Thus, step (d) can be carried out before, after, or simultaneously with step (e). A partially simultaneous mixed form is also possible. This may be particularly relevant when one and the same catalytic material can catalyze multiple reactions. Such an embodiment is particularly preferred according to the present invention. According to the present invention, these reactions may occur simultaneously, but the kinetics of each reaction may vary, so that a first reaction may finish earlier or achieve a higher conversion rate than a second reaction proceeding in parallel. An optional step (f) follows steps (d) and (e).

[0078] Steps (d1) and (d2) are considered separately for purposes of explanation, but both serve a common purpose of reducing the N2O content in the off-gas.

[0079] Steps (d1), (d2) and (e) may likewise be performed in any order, although partial simultaneity and hybridization are also possible in this regard.

[0080] In a preferred embodiment, the method of the present invention comprises the steps (a), optionally (b), (c), (d1), (e) and optionally (f); steps (a), optionally (b), (c), (d2), (e) and optionally (f); or steps (a), optionally (b), (c), (d1), (d2), (e) and optionally (f).

[0081] In a preferred embodiment, the off-gas undergoes the steps of the method of the present invention in one of the following orders:

[0082] (i)(a) →(c) →(d1) →(e); (ii) (a) → (c) → (e) → (d2); (iii)(a)→(c)→(e)→(d2)→(d1); (iv)(a)→(c)→(e)→(d1+d2);or (v)(a) →(c) →(e) →(d1). In a preferred embodiment, the off-gas undergoes the steps of the method of the present invention in one of the following orders:

[0083] (vi)(a)→(b)→(c)→(d1)→(e); (vii)(a)→(b)→(c)→(e)→(d2); (viii)(a)→(b)→(c)→(e)→(d2)→(d1); (ix)(a)→(b)→(c)→(e)→(d1+d2);or (x)(a)→(b)→(c)→(e)→(d1). In a preferred embodiment, the off-gas undergoes the steps of the method of the present invention in one of the following orders:

[0084] (xi)(a)→(b)→(c)→(d1)→(e)→(f); (xii)(a)→(b)→(c)→(e)→(d2)→(f); (xiii)(a)→(b)→(c)→(e)→(d2)→(d1)→(f); (xiv)(a)→(b)→(c)→(e)→(d1+d2)→(f);or (xv)(a)→(b)→(c)→(e)→(d1)→(f). What is meant by (d1+d2) is that both step (d1) and step (d2) are performed, but the execution of these two steps (d1) and (d2) is at least partially simultaneous, i.e., both steps proceed in parallel.

[0085] Between these steps there may be further steps not explicitly specified.

[0086] Material flow: For the purposes of the description, the following material flows are distinguished inter alia: - NH3 (reactant), used as starting material for catalytic decomposition and preferably fed into an NH3 decomposition device; In the case of series-connected NH3 decomposition devices, intermediate product gases exit the upstream NH3 decomposition device (pre-reactor) and are fed to the downstream NH3 decomposition device (main reactor); in the case of several pre-reactors, several intermediate product gases can be distinguished, which contain partial catalytic decomposition products of NH3, typically H2, N2, and relatively large amounts of undecomposed NH3; - a product gas obtained by catalytic decomposition of NH3, typically H2, N2 and a relatively small amount of undecomposed NH3; in the case of multiple series-connected NH3 decomposition devices, the product gas is the gas mixture exiting the last of the series-connected NH3 decomposition devices; - a combustion gas that is combusted in the firing system of the present invention, preferably in a combustion device, to generate combustion heat; the combustion gas comprises NH3 and H2, and optionally additionally N2; - Combustion air is supplied to the firing system of the present invention, preferably to the combustion device, so that the combustion gas can be burned in a mixture with the combustion air; the combustion air comprises O2 and N2; - Offgases formed during combustion of combustion gases in a mixture with combustion air; offgases include N2, H2O, NO X and N2O.

[0087] The main object of the present invention is to reduce NO in this off-gas. X and reducing the content of N2O.

[0088] Step (a): In step (a) of the method of the present invention, combustion of NH3 is carried out for the operation of a calcination system. Preferably, in step (a) of the method of the present invention, NH3 may be combusted in a mixture with other components (e.g., H2 or CH4). These calcination systems preferably include a combustion device in which NH3 is combusted to generate combustion heat, and an NH3 decomposition device in heat exchange with the combustion device, where NH3 is catalytically decomposed into N2 and H2. Combustion produces N2, H2O, NO X and NO. Residues of unburned NH may be present as well. The off-gas exits the firing system, preferably a combustion device, and is then fed directly to any step (b) or step (c) of the method of the present invention.

[0089] A "calcination system" in the context of the present invention generates heat through a combustion process. The calcination system preferably comprises a combustion device for combusting NH3 and an NH3 decomposition device for cracking NH3 into N2 and H2. Combustion of the combustion gas generates heat. In the context of the present invention, the "calcination system" or "combustion device" encompassed therein is any plant in which NH3 or an NH3-containing fuel is oxidized with O2 (preferably from combustion air) in order to produce, in particular, N2 and H2O as the main products. The use of NH3 in a higher oxidation number (e.g., NO2), as in the case of the production of nitric acid, is also possible. X A system in which NH3 is oxidized with O2 to produce nitrogen compounds having an oxidation number higher than that of the main product as the main product is not a calcination system or a combustion device in the context of the present invention. The production of such nitrogen compounds having an oxidation number higher than that of the main product typically requires a catalyst. Preferably, according to the present invention, the calcination system of the present invention is not equipped with a catalyst, i.e., preferably, the inventive combustion of NH3 and H2 according to the present invention is not catalyzed.

[0090] Combustion of NH3 refers to the oxidation of NH3 with O2; according to the present invention, this reaction does not have to be complete, so that the off-gas may contain residual unburned (unoxidized, unconverted) NH3 (NH3 slip, NH3 breakthrough). The same is true when NH3 is not in pure form but is burned together with other combustible gases, in particular H2 and / or CH4 (natural gas). The O2 used for combustion can be used in the form of combustion air, which may be enriched with O2.

[0091] In a preferred embodiment, in step (a) of the method of the present invention, NH3 is combusted in a firing system comprising a combustion device for combusting NH3 and an NH3 decomposition device for cracking NH3 into N2 and H2. The combustion of NH3 in the combustion device serves to heat an NH3 decomposition device, preferably a catalyst-filled reactor, for cracking NH3 into N2 and H2. According to the present invention, the cracking of NH3 into N2 and H2 is carried out as catalytic decomposition of NH3 by an NH3 decomposition catalyst.

[0092] According to the present invention, catalytic decomposition of NH3 refers to the formation of N2 and H2, which is sometimes referred to in the art as "cracking." The terms "catalytic decomposition," "decomposition," "catalytic cracking," and "cracking" of NH3 are used interchangeably and synonymously for purposes of description. Preferably, according to the present invention, catalytic decomposition of NH3 is preferably carried out in the absence of O2.

[0093] The calcination system of the present invention preferably comprises a combustion device and an NH decomposition device, which exchange heat with each other. In this combustion device, combustion gas containing NH, preferably H, is combusted with combustion air containing O to generate combustion heat. The combustion heat thus generated is at least partially supplied to (or transferred to) the NH decomposition device as a heat flow to provide the heat necessary for the endothermic catalytic decomposition of NH into H and N. Furthermore, according to the present invention, the combustion heat is preferably utilized to preheat the NH to be decomposed, the combustion gas, and the combustion air to a high temperature.

[0094] "Combustion device" and "furnace" are used interchangeably and synonymously for purposes of discussion.

[0095] The NH decomposition device is preferably a tubular reactor configured similarly to a primary reformer for producing synthesis gas or hydrogen from natural gas. The basic structure of such a combustion tubular reactor, configured similarly to a primary reformer, comprises one or more tubes containing an NH decomposition catalyst arranged in a combustion chamber and projecting into the flame of a burner. Radiant and convective heat from the flame and the hot off-gas transfer heat to the NH (process gas) flowing through the NH decomposition catalyst. Therefore, the combustion device preferably comprises a combustion chamber and one or more burners, preferably several burners. The NH decomposition device (tubes arranged in parallel) is then placed in the combustion device (combustion chamber, incineration chamber). To ensure uniform energy input and to enable the flame shape to be defined, the off-gas is removed from the combustion device by an imposed pressure gradient, for example, by using a compressor in the supply of combustion air or in the removal of the off-gas. To ensure sufficient heat transfer across the length of the NH decomposition catalyst bed within the tube, the off-gas must still have a sufficiently high temperature at the end of the NH decomposition catalyst bed, i.e., the end of the tube, to allow for significant release of radiant heat. Therefore, the off-gas exits the combustion device (combustion chamber, incineration chamber) at a high temperature that can exceed 1000 °C for a tubular reactor configured similarly to a primary reformer. Typically, the proportion of heat transferred to the endothermic catalytic decomposition of NH is approximately 40–60% of the total energy generated by the combustion of the combustion gas. The remaining heat can be used for other purposes.

[0096] After being drawn off from the combustion device (combustion chamber, incineration chamber), the off-gas preferably passes through an off-gas duct, which preferably fulfills three main tasks:

[0097] 1. Utilization of unused heat from the endothermic catalytic decomposition of NH3 to N2 and H2 from the combustion of NH3 to avoid energy waste or improve energy efficiency; 2. Preheating of material streams (e.g., NH3, combustion gases, combustion air) for improved energy integration and increased hydrogen yield; and 3. Reduction of the content of nitrogen oxides (especially NO, NO2 and N2O) through appropriate reaction regimes in order to minimize emissions or comply with regulations.

[0098] Step (a) of the method of the present invention, i.e., the combustion of NH3 and preferably H2 to operate the calcination system while producing off-gases that exit the calcination system, preferably comprises: (a1) optionally and preferably, the component step of heating and evaporating (liquid) NH3; (a2) optionally and preferably, the component step of heating combustion air (preferably containing N2 and O2); (a3) A firing system, preferably a combustion device, in which combustion gas (containing NH and preferably H) and combustion air (containing O) are combusted to produce off-gases (N, H, O, NO) X and N2O) and releasing at least a portion of the heat of combustion by flowing to an NH3 decomposition device; (a4) the component step of catalytically decomposing NH in an NH decomposition device via an NH decomposition catalyst, with absorption of combustion heat from component step (a3) ​​and generation of product gases (comprising H and N); Includes:

[0099] Combustion of combustion gases and air: In a preferred embodiment, NH3 is burned as the only fuel, which means that preferably no other gases are burned other than NH3. In another preferred embodiment, NH3 is burned in a mixture with H2. In a further preferred embodiment, NH3 is burned in a mixture with CH4 (natural gas). These gases or mixtures are also referred to as "combustion gases" for purposes of description. Besides NH3 and optionally H2 and / or CH4, the combustion gas may optionally contain further components, such as N2.

[0100] According to the invention, heat is provided by combustion of combustion gases in a firing system, preferably a combustion device, which for this purpose preferably comprises one or more burners, preferably at least two burners, more preferably at least three burners.

[0101] One reason for the combustion gas to contain a mixture of H2 and NH3 is that this mixture produces a moderate flame temperature and has better combustion characteristics than pure NH3. The appropriate mixture ratio of H2 and NH3 can also affect the nitrogen oxide content.

[0102] The combustion of NH3, i.e., the oxidation of NH3 with O2 (or a mixture of NH3 with another combustible gas, e.g., H2, CH4, etc.), is preferably not carried out via a catalyst, i.e., the combustion is not carried out in the presence of a heterogeneous catalyst.

[0103] More preferably, the H2 present in the combustion gases in a mixture with the combusted NH3 is formed by thermal and / or catalytic decomposition of NH3 (component step (a4)). The integrated combustion of NH3 and O2 preferably provides the energy for the catalytic decomposition (cracking). Preferably, therefore, in step (a), the combustion of NH3 is preferably integrated into a process for the thermal and / or catalytic decomposition of NH3 to N2 and H2.

[0104] The composition of the off-gas formed during combustion depends on the combustion gas used. In a preferred embodiment, sufficient H2 is added to NH3 to change the combustion characteristics of the combustion gas so that nearly quantitative conversion is achieved during combustion. In another preferred embodiment, the combustion gas used is a mixture of the output from a separation unit, preferably a pressure swing adsorption off-gas, or a membrane unit, preferably a pressure swing adsorption retentate, for the purification of H2, with a proportion of NH3 or H2 produced as product.

[0105] If the catalytic decomposition of NH3 does not proceed to completion, the product gas (i.e., the product of the catalytic decomposition) still contains residual unconverted NH3 in addition to N2 and H2. Preferably, the H2 present in the combustion gas in a mixture with the combusted NH3 is formed by the catalytic decomposition of NH3 and is then separated, optionally in a mixture with the residual NH3 and / or N2, from the product gas formed in the catalytic decomposition of NH3, preferably by pressure swing adsorption (PSA). Thus, preferably, the product gas obtained in the catalytic decomposition of NH3 and the NH3 decomposition catalyst according to the present invention is separated by pressure swing adsorption. -On the one hand, high-purity H2 (produced hydrogen), and on the other hand, a gas mixture (off-gas from pressure swing adsorption), is separated into

[0106] The gas mixture separated from H (off-gas from pressure swing adsorption) may contain, in addition to N, residual NH that was not catalytically decomposed and a certain amount of H. Therefore, the separation efficiency of the device for purifying H determines how much H is present in the off-gas of the pressure swing adsorption device or in the retentate of the membrane unit, and thus likewise affects the composition of the off-gas formed therefrom in combustion. Quantitative separation of the total amount of H is not feasible for production reasons or is not economically feasible, and therefore the separated gas mixture (off-gas from pressure swing adsorption) often contains a certain amount of H. In this way, a mixture of NH and H is already obtained, which can be directly combusted as is or first enriched with additional NH (or H).

[0107] Therefore, this gas mixture separated from the product gas by pressure swing adsorption is preferably used as combustion gas according to the present invention. Depending on the content of NH3 and H2, the separated gas mixture can be used as combustion gas as it is, or an appropriate amount of NH3 or H2 is metered in to set the desired ratio of NH3 to H2. If the catalytic decomposition proceeds to completion or substantially completion, the NH3 content in the separated gas mixture (off-gas of pressure swing adsorption) may still be too low, and it may be necessary to add a required amount of NH3.

[0108] The exact composition of the off-gas formed in the combustion of the flue gas depends on the composition of the flue gas and the combustion air. An essential parameter in describing the combustion characteristics of the flue gas, the pollutant emissions, and the composition of the off-gas is the mixture ratio of NH3 and H2.

[0109] The following table shows the compositions of the combustion gases and off-gases formed for the same composition of combustion air based on simulation calculations for five different process regimes #1-#5. The molar flows are normalized to a 1 MW calorific value flow rate so that they are equivalent. In process regimes #1-#3 (comparative examples), pure CH4, pure NH3, and pure H2 are used as combustion gases. For process regimes #4 and #5 (inventive examples), a mixture of H2 and NH3 (process regime #4) or H2, NH3, N2, and H2O are used as combustion gases (process regime #5; pressure swing adsorption (PSA) off-gas): [Table 1] As the data in the table above show, in the inventive process regime #5 (PSA off-gas), almost twice as much off-gas flows through the off-gas duct as in the hydrogen-fired reformer (process regime #3), and slightly less than twice as much as in the methane-fired reformer (process regime #1).

[0110] Thus, inventive process regime #5 has a much flatter temperature profile in the off-gas duct than the other process regimes and can therefore include more steps for heat integration, including those possible at lower flue gas temperatures. This allows for (near) complete energy integration, as demonstrated by process regimes #5-#7.

[0111] In the case of hydrogen or methane combustion reformers, the temperature profile in the off-gas duct must be much steeper due to the small amount of off-gas available. Because the heat exchanger in the off-gas duct requires a minimum temperature difference to be economically designed, a steep temperature profile due to the required temperature difference significantly increases the risk of leaving unusable residual heat. In either case, the off-gas entering the off-gas duct is much hotter in these cases, requiring the use of more expensive materials.

[0112] It is preferred to establish a mixture ratio of NH3 and H2 in the combustion gas, which is optimized for subsequent combustion. The proportion of H2 is preferably at most 80 mol%, more preferably at most 70 mol%, even more preferably at most 60 mol%, most preferably at most 50 mol%, and in particular at most 40 mol%. The proportion of H2 is preferably at most 30 mol%, more preferably at most 20 mol%, even more preferably at most 15 mol%, most preferably at most 10 mol%, and in particular at most 5 mol%.

[0113] The proportion of H2 is preferably at least 1 mol%, more preferably at least 2 mol%, even more preferably at least 3 mol%, most preferably at least 4 mol%, in particular at least 5 mol%. The proportion of H2 is preferably at least 10 mol%, more preferably at least 20 mol%, even more preferably at least 30 mol%, most preferably at least 40 mol%, in particular at least 50 mol%.

[0114] In particularly preferred embodiments, the molar ratio of H2:NH3 in the mixture is in the range of 45:55 to 90:10, preferably 50:50 to 85:15, more preferably 55:45 to 80:20, even more preferably 60:40 to 75:25, and most preferably 65:35 to 70:30 or 70:30 to 75:25. Preferably, according to the present invention, the combustion gas used is a gas mixture separated from a gas swing adsorption system, so the molar ratio of H2:NH3 depends primarily on the hydrogen yield and can be as high as about 15:1 in extreme cases.

[0115] In the combustion of the mixture of combustion gas and combustion air, the air ratio λ for combustion is preferably in the range of 0.9 to 1.7, more preferably 1.0 to 1.6, even more preferably 1.1 to 1.5, and most preferably 1.2 to 1.4. A further very particularly preferred range for the air ratio λ is between 1.0 and 1.2.

[0116] In a particularly preferred embodiment, the air ratio is in the range 1.06±0.06, preferably 1.06±0.05, more preferably 1.06±0.04, even more preferably 1.06±0.03, most preferably 1.06±0.02, especially 1.06±0.01.

[0117] The air ratio λ (i.e., combustion air ratio) indicates the mass ratio of combustion air to combustion gas relative to the stoichiometrically ideal ratio for a theoretically complete combustion process. It is defined as the ratio of air to fuel containing a sufficient mass of oxygen to achieve complete combustion of a given mass of fuel (see, for example, K. Soman, Thermal Engineering, PHI, 2011, page 224, no. 5.4.2). In principle, the ratio can be expressed in mass or molar amounts (see, for example, P. Majumdar, Design of Thermal Energy Systems, Wiley 2021, page 66, no. 2.13.5.2). For purposes of explanation, the ratio is based on mass. If another oxygen-containing gas is used in the combustion operation instead of air, "air" should, strictly speaking, be replaced by "oxygen carrier." However, the λ parameter is still used in the above definition.

[0118] In a preferred embodiment, the equivalence ratio NH3 / H2 (Φ) (not to be confused with the reciprocal of the air ratio 1 / λ) ranges from 0.55 to 1.40, more preferably from 1.05 to 1.20. The formation of nitrogen oxides depends on factors including the residual oxygen content in the off-gas, which can be, for example, 3 mol% or 1 mol%. For example, a residual oxygen content of 1 mol% requires an air ratio of about 1.1.

[0119] The concentration of nitrogen oxides (especially NO, NO2 and NO) and the dew point of the condensable components are two parameters of great importance for the technical implementation and adaptation of the off-gas duct. These parameters are in turn determined to a very important extent by the composition of the off-gas. The off-gas from tubular reactors of similar design to primary reformers contains nitrogen oxides formed in the combustion reaction. In many countries, nitrogen oxide emissions are regulated and, if they exceed permissible limits, must be reduced by using appropriate technologies.

[0120] Nitrogen oxides (especially NO, NO2, and NO) are formed by various mechanisms in combustion reactions. In tubular reactors with a design similar to that of primary reformers, NH3-free combustion gases produce only so-called "thermal nitrogen oxides" through the recombination of nitrogen radicals with oxygen, the formation of which is favored at high temperatures. NH3-containing combustion gases can form nitrogen oxides through various reaction pathways in the complex kinetics of the combustion of NH3, called "kinetic nitrogen oxides."

[0121] In plants for the production of H2 from NH3, both thermal and kinetic nitrogen oxides can be formed. The presence of H2 in the combustion gases increases the flame temperature and the tendency for kinetic nitrogen oxides to form due to the mixing of NH3. The literature describes many cases where the combustion of a mixture of NH3 and H2 results in significantly higher nitrogen oxide emissions than in conventional primary reformers. The nitrogen oxide emissions depend not only on the composition of the combustion gases, in particular the mixing ratio of NH3 and H2, but also on various other parameters, in particular - preheating temperatures of combustion air and combustion gases; - Excess combustion air in combustion, and - the design and geometry of the burners used, Depends on.

[0122] Therefore, the exact amount of nitrogen oxide emissions depends much more on the individual case than in conventional primary reformers. X Typical emissions of nitrogen oxides (i.e., NO and NO2) range from 100 to 10,000 ppmv. An example of an off-gas with a relatively low nitrogen oxide content includes 500 ppmv NO, 10 ppmv NO2, and 10 ppmv N2O (Case A). An example of an off-gas with a relatively high nitrogen oxide content includes 5,000 ppmv NO, 10 ppmv NO2, and 50 ppmv N2O (Case B).

[0123] During start-up of a system using NH3-rich combustion gas, NO emissions will be relatively low, but NO emissions will be relatively high, which must be taken into account in the fitment design, even though this is not of great importance to the plant mass balance during normal operation, i.e., after the end of start-up.

[0124] Furthermore, in the off-gas duct study of a system that produces H2 from NH3, two dew points are important: the H2O dew point and the NH4NO3 dew point.

[0125] The dew point of HO depends on the partial pressure of HO in the off-gas. In process variations where the off-gas of a pressure swing adsorption (PSA) unit or the retentate of a membrane unit is fed to a combustion gas system, the off-gas contains primarily N and only a relatively small amount of HO, which generally results in a relatively low dew point.

[0126] The table below shows the moisture content of the off-gas and the water dew point of the process variants already implemented. [Table 2] When this H2O dew point is reached during system operation, droplet formation occurs. Temperature changes in the off-gas result from heat loss in the heat exchanger, which can lead to condensed water depositing on the tube surfaces and impairing heat transfer. If droplets enter the off-gas fan, they can damage the rotor. Therefore, condensation of liquid H2O is undesirable. To avoid adverse effects on system operation and damage, a minimum off-gas temperature margin from the 25 K dew point should be observed in the off-gas duct. Therefore, according to the present invention, the off-gas is preferably not cooled below approximately 81-88 °C in the off-gas duct, depending on the specific conditions. This temperature is therefore the technically achievable minimum, and the internal energy of the off-gas cannot be further utilized. This is therefore an unavoidable energy loss.

[0127] The NH4NO3 dew point is important because devices used to remove nitrogen oxides from off-gas (off-gas treatment systems) can have a slippage of incompletely decomposed nitrogen oxides, usually NO. NH3, metered into off-gas treatment systems as a reducing agent, is also often incompletely converted, resulting in a small amount of NO and NH3 slippage. Cooling of the off-gas in the off-gas duct can cause the temperature to fall below the NH4NO3 dew point, which can precipitate on the heat exchanger tubes. This precipitate is shock-sensitive and potentially explosive, posing a risk to the safe operation of the system. The table below shows the NH4NO3 dew point for various typical residual contents of NO and NH3 in the off-gas. [Table 3] To achieve the critical temperature for NH4NO3 deposition, the gas stream does not necessarily have to reach or fall below this temperature; even the wall temperature of the heat exchanger tubes may be sufficient and may result in NH4NO3 deposition. Because combustion devices typically require combustion air to be drawn in at ambient temperature, there is a risk of NH4NO3 deposition on the heat exchanger tubes used to preheat the combustion air under conventional operating conditions.

[0128] Therefore, observing the minimum temperature of the off-gas, as opposed to the dew point of H2O, is not an adequate solution. To avoid the risk of NH4NO3 precipitation, the equipment for removing nitrogen oxides (off-gas treatment system) must be able to remove NO X The system should be operated in accordance with the present invention so that the slip of either NO or NH3, or ideally both, is reduced to a maximum of 1 ppmv. This is because, according to the present invention, the NO slip due to NH3 is X This can be achieved by a suitable reaction scheme in the chemical reduction of NH3, preferably by a reactor for post-oxidation of NH3 with residual oxygen from the off-gas.

[0129] Catalytic decomposition of NH3 to H2 and N2: The catalytic decomposition of NH3 is primarily thermally driven, but is enhanced by the use of NH3 decomposition catalysts. According to the present invention, the catalytic decomposition of NH3 can be carried out under a variety of conditions using a variety of NH3 decomposition catalysts and with a variety of interconnections to different reactor types.

[0130] According to the present invention, the catalytic decomposition of NH3 is preferably carried out by supplying heat in the presence of an NH3 decomposition catalyst. The important parameters for the catalytic decomposition of NH3 are the type of NH3 decomposition catalyst, reaction temperature and reaction pressure.

[0131] NH3 decomposition catalysts useful according to the present invention include a variety of materials. The reaction temperature at which the catalytic decomposition of NH3 proceeds is determined, inter alia, by the choice of NH3 decomposition catalyst.

[0132] Suitable methods for the thermal and / or catalytic decomposition of NH to N and H are known to those skilled in the art. Suitable catalysts for the catalytic decomposition of NH to N and H are, for example, AlO or SiO-supported Ru, MgAlO-supported Fe, Co, Ni, Cu or Ru, or CoMoN (A. Boisen et al., Journal of Catalysis 230 (2005) 309-312; I. Lucentini et al., Ind. Eng. Chem. Res. 2021, 60, 18560-18611; HJ Lee et al., Catalysts 2022, 12, 1203).

[0133] In a preferred embodiment of the present invention, a nickel-based NH decomposition catalyst is used. The reaction temperature and pressure determine the equilibrium conversion. At 900°C and 20 bar pressure, the decomposition of NH proceeds almost quantitatively. At 650°C, the conversion of NH is about 98.5%, and at 500°C, it is only about 95%.

[0134] In a preferred embodiment, a reaction temperature in the range of about 550° C. to about 900° C., preferably about 550° C. to about 700° C., is established to achieve high conversion rates.

[0135] In another preferred embodiment, a reaction temperature in the range of about 600° C. to about 900° C., preferably about 600° C. to about 700° C., is established to achieve high conversion rates.

[0136] In terms of energy balance and conversion, the optimum reaction temperature is in the range of approximately 630°C to 640°C. Nickel-based NH3 decomposition catalysts are advantageous despite the relatively high reaction temperature. Because of the high conversion rate, the residual content of undecomposed NH3 in the product gas is relatively low, so it is preferable to omit the separation of undecomposed NH3 for recovery. Instead, combined separation of N2 and undecomposed NH3 from the product gas is combined with pressure swing adsorption in the process of H2 purification.

[0137] The NH decomposition catalyst preferably comprises supported nickel. Preferred support materials include Al2O3, MgO, SiO2, mesoporous SiO2 (e.g., MCF-17, MCM-41, SBA-15), zeolites (e.g., HY, H-ZSM-5), BaMnO3, BaTiO3, BaZrO3, CaMnO3, CaTiO3, CaZrO3, CeO2, Gd2O3, GdAlO3, KNbO3, La2O3, LaAlO3, MnO2, Selected from the group consisting of NaNbO3, Nb2O5, Sm2O3, SmAlO3, SrMnO3, SrTiO3, SrZrO3, TiO2, Y2O3, ZrO2, carbon (e.g., CNT, SWCNT, AX-21, MSC-30, MESO-C, GNP, activated carbon, graphene, graphene oxide), attapulgite, hydrocalumite, sepiolite, and mixtures thereof.

[0138] In another preferred embodiment of the present invention, a ruthenium-based NH decomposition catalyst is used. For this purpose, according to the present invention, reaction temperatures in the range of about 450°C to about 500°C are preferred, although somewhat lower conversions, for example about 95%, can be achieved so as to result in a higher residual content of undecomposed NH in the product gas.

[0139] Alternatively, other NH decomposition catalysts can be used optionally at even lower reaction temperatures. The lower the reaction temperature, the lower the conversion rate and the more undecomposed NH must be separated from the product gas and recycled.

[0140] According to the present invention, the reaction pressure is preferably about 15 bara to about 25 bara. Because the reaction stoichiometry (2 NH3 → N2 + 3 H2) increases the volume, increasing the reaction pressure has a fundamentally negative effect on the conversion. On the other hand, to limit the vessel volume and therefore capital costs, it is desirable to operate the entire process at higher pressures. At reaction pressures of only 1 bar, conversions of over 99% may be achievable at reaction temperatures above 400°C. However, because a reaction pressure of 1 bar is only useful for the smallest systems, the system of the present invention is preferably operated at higher reaction pressures, even if a certain loss of conversion must be accepted as a result.

[0141] The reaction pressure is dictated, inter alia, by the implementation of H purification. The preferred pressure swing absorption (PSA) for H purification according to the present invention can be effectively operated in accordance with the present invention at pressures preferably in the range of about 15 bar to about 25 bar. The pressure of the product gas leaving the NH decomposition device is preferably in the range of about 15 to about 25 bara, more preferably about 18 bara to about 22 bara, and even more preferably about 19 bara to about 21 bara. In this way, a good balance is found between the requirements of pressure swing adsorption on the one hand and the conversion achieved on the other hand.

[0142] The catalytic decomposition of NH3 can in principle proceed in different reactor types.

[0143] In the adiabatic reaction regime, the internal heat of the reaction gas is used as the energy source for the reaction. Suitable reactors for this purpose are autothermal reformers and secondary reformers, which operate with internal energy generation. Combustion air is added to the process gas, and a portion of the reaction gas is burned to raise the reactor outlet temperature to the desired level. A drawback is the presence of water formed during combustion in the process gas, which must be removed by condensation. A portion of the undecomposed NH3 dissolves in the condensed water and disappears. Furthermore, high temperatures lead to the formation of significant amounts of nitrogen oxides.

[0144] According to the present invention, these drawbacks are avoided in that the product gas is preferably physically separated from the combustion gas and the off-gas formed from the combustion gas. The product gas is formed in the NH decomposition device of the present invention in the calcination system by the decomposition of NH and preferably exits the NH decomposition device through a dedicated outlet. The combustion gas is combusted with combustion air in the combustion device of the calcination system, and the formed off-gas exits the combustion device preferably through a dedicated outlet and preferably enters an off-gas duct. The product gas and off-gas are preferably not mixed with each other and remain physically separated from each other. The heat of combustion formed in the combustion of the combustion gas flows into the NH decomposition device as a heat flow, thereby providing the heat necessary to sustain the endothermic catalytic decomposition of NH.

[0145] Preferably, the catalytic decomposition of NH3 is carried out in an isothermal, quasi-isothermal, or mixed isothermal and adiabatic process regime. In the isothermal reaction regime, the temperature of the gas remains almost unchanged.

[0146] In a preferred embodiment of the present invention, the catalytic decomposition of NH3 is carried out in a reactor similar to the primary reformer, and to this end, the reactor contains both the NH3 decomposition device of the present invention and the combustion device of the present invention.

[0147] For this purpose, an NH3 decomposition catalyst is preferably disposed in at least one tube through which NH3 flows, more preferably at least two tubes, and even more preferably at least three tubes. At least one tube contains an NH3 decomposition catalyst. NH3 preferably passes through at least one tube from top to bottom. In a physically separated combustion chamber, the combustion gas to be burned is preferably a mixture of NH3 and H2 together with combustion air (combustion device). N2 formed in addition to H2 in the catalytic decomposition of NH3 is inert and serves as an additional heat carrier. The combustion heat generated by the combustion process in the combustion chamber of the combustion device is used to heat the NH3 decomposition device, preferably the tube(s) through which the NH3 to be decomposed passes. For this purpose, a heat flow is directed from the combustion device to the NH3 decomposition device.

[0148] In a particularly preferred embodiment of the present invention, NH3 is preheated before entering the NH3 decomposition device of the present invention. As a result of this preheating, the temperature of NH3 before entering the NH3 decomposition device of the present invention is preferably at least about 600°C, preferably at least about 630°C. The temperature of NH3 is preferably about 850°C or less, preferably about 820°C or less. More preferably, the temperature of NH3 entering the NH3 decomposition device of the present invention is about 780°C to 820°C, preferably about 800°C. In this case, the NH3 decomposition device of the present invention and the combustion device of the present invention preferably form a reactor designed similarly to a primary reformer. The NH3 decomposition catalyst is preferably nickel-based. In a preferred embodiment, the reaction temperature in the NH3 decomposition device, preferably at least one tube containing the NH3 decomposition catalyst and through which NH3 is conducted, is preferably about 630°C to about 670°C, preferably about 650°C. In another preferred embodiment, this temperature is about 660°C to 700°C, preferably about 680°C. The product gas preferably exits the reactor (NH3 decomposition device) at a pressure of about 15 bara to about 25 bara, preferably about 20 bara.

[0149] In a further particularly preferred embodiment of the present invention, the decomposition of NH3 is carried out in two stages in two NH3 decomposition devices through which the flow passes successively. In a pre-reactor (first NH3 decomposition device), first only a portion of the NH3 is decomposed. The decomposition of the remainder of the NH3 up to the maximum conversion obtained then takes place in the second NH3 decomposition device. Preferably, for this purpose, the second NH3 decomposition device together with the combustion device of the present invention forms a reactor of similar design to the primary reformer and as described in detail above.

[0150] The NH3 is preferably preheated before being introduced into the prereactor (first NH3 decomposition device). The temperature of the NH3 after heating and upon entering the prereactor (first NH3 decomposition device) is about 620°C to about 680°C, preferably about 650°C. The preheated NH3 then enters the prereactor, which contains an NH3 decomposition catalyst and where some catalytic decomposition of NH3 to N2 and H2 occurs. An intermediate product gas is formed, which still contains significant residual amounts of undecomposed NH3, but also contains already formed N2 and H2. As a result of the endothermic decomposition of NH3, the intermediate product gas is preferably cooled.

[0151] Preferably, the conversion of the cracked NH3 in the pre-reactor is at most 30%, more preferably at most 25%, even more preferably at most 20% of the total conversion achieved.

[0152] Preferably, the conversion of the cracked NH3 in the pre-reactor is at least 10%, more preferably at least 15% of the total conversion achieved.

[0153] After exiting the pre-reactor, the intermediate product gas is preferably reheated before entering the downstream second NH3 decomposition device.

[0154] In a preferred embodiment, the temperature of the intermediate product gas after reheating and entering the second NH3 decomposition device is between about 550°C and about 680°C, more preferably about 580°C.

[0155] In another preferred embodiment, the temperature of the intermediate product gas after reheating and upon entering the second NH3 decomposition device is from about 620°C to about 680°C, more preferably about 650°C.

[0156] Then, in the second NH3 decomposition device, the residual decomposition of NH3 proceeds until total conversion is achieved.

[0157] In this preferred embodiment of the present invention, for the same overall conversion, the temperatures of the intermediate product gases entering the pre-reactor (first NH decomposition device) and the second NH decomposition device may each be lower than the temperature of NH in the case of a single-stage decomposition of NH, i.e., passing through only a single NH decomposition device. The lower temperatures result in a lower degree of nitriding of the pipeline and a longer service life for the steel in contact with NH.

[0158] The NH3 decomposition catalyst in the first NH3 decomposition device (pre-reactor) is preferably the same as that in the second NH3 decomposition device.

[0159] Characteristics of off-gas from the firing system: Combustion of the combustion gas and combustion air produces off-gases in the firing system, preferably a combustion device, which exit the firing system, preferably in an off-gas duct.

[0160] In a preferred embodiment, the off-gas exiting the firing system, preferably the combustion device, and entering the off-gas duct has one or more of the following characteristics:

[0161] In a preferred embodiment, the off-gas has a NO content greater than N2O content. X Contains NO X The content is preferably at least 2 times, more preferably at least 3 times, even more preferably at least 4 times, most preferably at least 7 times, especially at least 10 times the NO content. XThe molar ratio of N2O to N2O is preferably greater than 10:1, more preferably at least 20:1, even more preferably at least 30:1, most preferably at least 40:1, especially at least 50:1.

[0162] In a preferred embodiment, the off-gas has a NO content that is greater than the NO content, preferably at least 2 times, more preferably at least 3 times, even more preferably at least 4 times, most preferably at least 7 times, especially at least 10 times higher than the NO content.

[0163] In a preferred embodiment, the off-gas has a NO content that is greater than the N2O content, with the NO content preferably being at least 2 times, more preferably at least 3 times, even more preferably at least 4 times, most preferably at least 7 times, especially at least 10 times higher than the N2O content.

[0164] Preferably, the off-gas contains at least 10 ppmv, preferably at least 20 ppmv, more preferably at least 30 ppmv, even more preferably at least 40 ppmv, especially at least 50 ppmv NO X It has a content.

[0165] Preferably, the off-gas contains at least 75 ppmv, preferably at least 100 ppmv, more preferably at least 150 ppmv, even more preferably at least 200 ppmv, especially at least 250 ppmv NO X It has a content.

[0166] Preferably, the off-gas contains at least 500 ppmv, preferably at least 1000 ppmv, more preferably at least 2000 ppmv, even more preferably at least 3000 ppmv, especially at least 3500 ppmv NO X It has a content.

[0167] Preferably the off-gas has an N2O content of at least 10 ppmv, preferably at least 20 ppmv, more preferably at least 30 ppmv, even more preferably at least 40 ppmv, especially at least 50 ppmv.

[0168] Preferably the off-gas has an N2O content of at least 75 ppmv, preferably at least 100 ppmv, more preferably at least 150 ppmv, even more preferably at least 200 ppmv, especially at least 250 ppmv.

[0169] The preferred off-gas is NO in the range of 1500 to 3000 ppmv, preferably 2000 to 3000 ppmv. X content, and N2O content in the range of 20 to 100 ppmv.

[0170] In a preferred embodiment, the off-gas has an HO content of more than 4.0 vol.%, preferably at least 5.0 vol.%, more preferably at least 6.0 vol.%, even more preferably at least 7.0 vol.%, most preferably at least 8.0 vol.%, especially at least 9.0 vol.%.

[0171] In a further preferred embodiment the off-gas has an HO content of at least 10% by volume, preferably at least 12% by volume, more preferably at least 14% by volume, even more preferably at least 16% by volume, most preferably at least 18% by volume, in particular at least 20% by volume.

[0172] In a preferred embodiment, the off-gas has an HO content in the range of 10±8% by volume, preferably in the range of 10±7% by volume, more preferably in the range of 10±6% by volume, even more preferably in the range of 10±5% by volume, most preferably in the range of 10±4% by volume, and especially in the range of 10±3% by volume.

[0173] In a preferred embodiment, the off-gas has an HO content in the range of 15±8% by volume, preferably in the range of 15±7% by volume, more preferably in the range of 15±6% by volume, even more preferably in the range of 15±5% by volume, most preferably in the range of 15±4% by volume, and especially in the range of 15±3% by volume.

[0174] In a preferred embodiment, the off-gas has an HO content in the range of 20±8% by volume, preferably in the range of 20±7% by volume, more preferably in the range of 20±6% by volume, even more preferably in the range of 20±5% by volume, most preferably in the range of 20±4% by volume, and especially in the range of 20±3% by volume.

[0175] In a preferred embodiment, the off-gas has an HO content in the range of 25±8% by volume, preferably in the range of 25±7% by volume, more preferably in the range of 25±6% by volume, even more preferably in the range of 25±5% by volume, most preferably in the range of 25±4% by volume, and especially in the range of 25±3% by volume.

[0176] In a preferred embodiment, the off-gas has an HO content in the range of 30±8% by volume, preferably in the range of 30±7% by volume, more preferably in the range of 30±6% by volume, even more preferably in the range of 30±5% by volume, most preferably in the range of 30±4% by volume, and especially in the range of 30±3% by volume.

[0177] Preferably, the off-gas has an N2 content of at most 95% by volume, preferably at most 90% by volume, more preferably at most 85% by volume, even more preferably at most 80% by volume, most preferably at most 75% by volume, especially at most 70% by volume.

[0178] Preferably, the off-gas has an N content of at least 40% by volume, preferably at least 50% by volume, more preferably at least 60% by volume, even more preferably at least 70% by volume, most preferably at least 80% by volume, especially at least 90% by volume.

[0179] Preferably, the off-gas leaving the calcination system, preferably the combustion device, is at a temperature T1 of at least 500°C, more preferably at least 600°C, even more preferably at least 700°C, most preferably at least 800°C, especially at least 900°C.

[0180] Preferably, the off-gas leaving the calcination system, preferably the combustion device, has a temperature T1 of at most 1100°C, more preferably at most 1000°C, even more preferably at most 900°C, most preferably at most 800°C, especially at most 700°C.

[0181] Preferably, the off-gas leaving the calcination system, preferably the combustion device, is at a pressure of up to 1.5 bar, preferably atmospheric pressure.

[0182] Preferably, the off-gas leaving the calcination system, preferably the combustion device, contains at least 10%, more preferably at least 20%, even more preferably at least 30%, most preferably at least 40%, especially at least 50% NO X has an oxidation degree of

[0183] Preferably, the off-gas leaving the calcination system, preferably the combustion device, contains up to 90%, more preferably up to 80%, even more preferably up to 70%, most preferably up to 60%, especially up to 50% NO X has an oxidation degree of

[0184] Preferably, the off-gas exiting the calcination system, preferably the combustion device, has an O2 content of less than 2.0% by volume.

[0185] Step (b): In any preferred step (b) of the method of the present invention, the temperature T1 of the off-gas is preferably measured as it leaves the firing system, preferably a combustion device, and modified with a suitable device so that the off-gas entering the off-gas treatment system is at a temperature T2 that is optimized under given conditions for the performance of steps (d) and (e) of the method of the present invention within the off-gas treatment system. The optimized temperature is determined by the selected configuration of steps (d) and (e), i.e., NO reduction and NO reduction. X The type and sequence of the individual process steps for reduction, in particular the N2O decomposition catalyst and / or N2O reduction catalyst and NO X It depends on the type of catalytic material used in the reduction catalyst.

[0186] Suitable devices for modifying the temperature of the off-gas are known to those skilled in the art and include in particular heat exchangers which may be configured, for example, as plate or tube heat exchangers.

[0187] In the optional and preferred step (b) of the method of the present invention, the off-gas is cooled in at least one heat exchanger, preferably arranged downstream of the calcination system in the flow direction of the off-gas.

[0188] The off-gas from a tubular reactor of similar design to a primary reformer contains a significant amount of internal energy. The process of producing H from NH requires the supply of process streams at high temperatures. In accordance with the present invention, the off-gas is cooled and used to preheat these process streams. This has the advantages of reducing the plant's demand for combustion gases and increasing the yield of hydrogen product.

[0189] The effectiveness of different variations of the process regime can be measured by the hydrogen yield, which is defined as:

number

[0190] To absorb heat from the off-gas, several process streams, namely: - Preheating and evaporation of NH3 (also possible indirectly); - Further heating of evaporated NH3 and intermediate product gases; - Combustion air heating; - Preheating of boiler feed water; -Water heating; - Heating of combustion gases; - Evaporation of boiler feed water to produce steam; -Superheating of steam; - auxiliary stream (heat transfer medium for preheating NH3 or for the evaporator of the NH3 desorption unit); can be used.

[0191] The target temperatures of the process streams to be heated generally dictate the order in which they are heated. A high temperature difference between the off-gas and the heat absorbing process stream reduces the required size of the heat exchanger.

[0192] However, it is advantageous to maintain a minimum temperature difference across all components. This prevents an increase in the temperature difference within the heat exchanger, and therefore its reduction in size is "paid for" with an increase in the size of all other heat exchangers. To allow an economical design of the heat exchanger in the off-gas duct, preferably according to the invention there is a minimum temperature difference of 45 K between the inlet of the hot stream and the outlet of the cold stream, or between the inlet of the cold stream and the outlet of the hot stream, depending on which pair of values ​​is smaller.

[0193] A further essential factor in the development of an effective solution for the off-gas duct of a tubular reactor of similar design to the primary reformer is the setting of the temperature required for the unit to remove nitrogen oxides from the off-gas.

[0194] It is theoretically possible to use the heat of the off-gas in many different configurations. In a plant for producing H2 from NH3, a further significant source of heat is available along with the product gas stream produced in the NH3 decomposition device. According to the invention, the following means for heat integration are available: - generation of water vapor, -NH3 preheating, - preheating H2O to produce water vapor, and / or - cooling the product gas with subsequent heat integration of cooling water; In this respect, it is advantageous and preferred to use the heat present in the product gas.

[0195] According to the invention, the following means for heat integration are provided: - preheating NH3 to the inlet temperature of the NH3 decomposition device; - Preheating of boiler feed water, and / or - Preheating of combustion air, In this respect, it is also advantageous and preferred to use the heat present in the off-gas.

[0196] Due to the mechanical constraints of the heat exchangers used in the off-gas duct, the required energy and temperature profiles of the off-gas and process streams to be heated, residual heat that is available but not integrable often remains in the off-gas in such configurations. This is manifested as a high inlet temperature of the off-gas to the off-gas duct stack. The internal energy present in this stream is lost to the process, ultimately reducing the H2 yield.

[0197] According to the invention, in order to reduce the heat loss via the off-gas and increase the yield of H2, the following further integration steps in the off-gas duct are possible and preferred:

[0198] - preheating of NH3 to the inlet temperature of the first pre-reactor (preferably an adiabatic fixed-bed reactor); - preheating of NH3 to the inlet temperature of the second pre-reactor (preferably an adiabatic fixed-bed reactor); - Two-stage preheating of combustion air; - Preheating of combustion gases (preferably the output from a purification plant for H2, more preferably the off-gas from a pressure swing adsorption unit or the retentate from a membrane unit); and / or - Preheating of auxiliary streams to integrate available residual heat.

[0199] The heat exchanger of the present invention is useful for transferring heat from one medium to another without mixing the media. For the purpose of explanation, in an "A / B heat exchanger," the heat release medium A is mentioned first, followed by the heat absorption medium B. Thus, for example, an "off-gas / NH3 heat exchanger" is used to release the heat present in the off-gas to NH3. For this purpose, the off-gas / NH3 heat exchangers are correspondingly interconnected, i.e., the off-gas flows through its hotter side and the NH3 flows through its colder side. For simplicity, the nomenclature "NH3" is used for the starting material and any intermediate product gas that still contains a significant amount of NH3. Heat exchangers of the same function may be numbered for distinguishability, but a specific number does not necessarily mean that all heat exchangers of the same function with lower numbers must necessarily be present at the same time. Thus, for example, it is possible for a second off-gas / combustion air heat exchanger to be present and the first off-gas / combustion air heat exchanger not to be present.

[0200] Each heat exchanger of the present invention may exist independently as a single heat exchanger of the possibly described design or interconnection, or as part of a plurality of the same function, for example, two or three heat exchangers connected in series, possibly of the described design or interconnection. The heat release medium and heat absorption medium are then the same in each of the plurality of heat exchangers of the same function. Dividing a single heat exchanger into, for example, two heat exchangers connected in series of the same function may have structural and / or design advantages.

[0201] The off-gas leaves the firing system, preferably the combustion device, at a temperature T1 and is preferably cooled to a temperature T2 at which the off-gas is then transferred to an off-gas treatment system in step (b). Preferably, both the at least one heat exchanger and the off-gas treatment system are located within the off-gas duct.

[0202] In a preferred embodiment, the off-gas is cooled in a single heat exchanger located downstream of the calcination system in the off-gas flow direction (see Figure 2).

[0203] In another preferred embodiment, the off-gas is cooled successively in at least two heat exchangers located downstream of the calcination system in the off-gas flow direction (see Figures 3, 5 and 6).

[0204] In a further preferred embodiment, the off-gas is cooled successively in at least three heat exchangers arranged downstream of the calcination system in the flow direction of the off-gas (see Figure 4).

[0205] The off-gas is cooled in at least one heat exchanger by the release of heat from the off-gas to a heat transfer medium.

[0206] Preferably, according to the present invention, the heat transfer medium used is NH3, which is then fed to catalytic decomposition in the NH3 decomposition device via an NH3 decomposition catalyst.

[0207] In a preferred embodiment, in step (b) of the method of the present invention, the off-gas is cooled in at least one first off-gas / NH3 heat exchanger arranged downstream of the calcination system in the flow direction of the off-gas. In an NH3 decomposition device, preferably arranged downstream of the first off-gas / NH3 heat exchanger in the flow direction of the NH3, catalytic decomposition of the heated NH3 is carried out over an NH3 decomposition catalyst to produce product gas. NH3 is heated in the first off-gas / NH3 heat exchanger (see Figure 2) by absorbing heat from the off-gas.

[0208] In another preferred embodiment, the off-gas is treated in step (b) of the method of the present invention by a first off-gas / NH3 heat exchanger arranged downstream of the calcination system in the flow direction of the off-gas, a second off-gas / NH3 heat exchanger arranged downstream of the first off-gas / NH3 heat exchanger in the flow direction of the off-gas, It is cooled.

[0209] In a first NH decomposition device (pre-reactor), preferably located downstream of the first off-gas / NH heat exchanger in the flow direction of NH, partial catalytic decomposition of the heated NH is carried out over an NH decomposition catalyst to produce an intermediate product gas. The second off-gas / NH heat exchanger is preferably located downstream of the first NH decomposition device (pre-reactor) in the flow direction of NH.

[0210] In a second NH3 decomposition device (primary reactor), preferably located downstream of the second off-gas / NH3 heat exchanger in the NH3 flow direction, catalytic decomposition of the heated NH3 is carried out over an NH3 decomposition catalyst to produce product gases.

[0211] The NH3 (or intermediate product gas) is heated by absorbing heat from the off-gas in the first off-gas / NH3 heat exchanger and in the second off-gas / NH3 heat exchanger.

[0212] The off-gas flows first through a first off-gas / NH3 heat exchanger and then through a second off-gas / NH3 heat exchanger.

[0213] The NH3 (or intermediate product gas) first flows through a first off-gas / NH3 heat exchanger, absorbing heat from the off-gas therein. The heated NH3 then flows into a first NH3 decomposition device, where partial catalytic decomposition of the heated NH3 occurs over an NH3 decomposition catalyst to produce an intermediate product gas. The intermediate product gas thus formed, still containing a significant amount of undecomposed NH3, then flows through a second off-gas / NH3 heat exchanger, where it again absorbs heat from the off-gas. Finally, the heated intermediate product gas flows into a second NH3 decomposition device, where catalytic decomposition of the heated NH3 occurs over an NH3 decomposition catalyst to produce a product gas (see Figures 3, 5, and 6).

[0214] In a further preferred embodiment, the off-gas is treated in step (b) of the method of the present invention with a first off-gas / NH3 heat exchanger arranged downstream of the calcination system in the flow direction of the off-gas, a second off-gas / NH3 heat exchanger arranged downstream of the first off-gas / NH3 heat exchanger in the flow direction of the off-gas, a third off-gas / NH3 heat exchanger arranged downstream of the second off-gas / NH3 heat exchanger in the flow direction of the off-gas, It is cooled.

[0215] In a first NH decomposition device (first pre-reactor), preferably arranged downstream of the first off-gas / NH heat exchanger in the flow direction of NH, partial catalytic decomposition of the heated NH is carried out over an NH decomposition catalyst to produce a first intermediate product gas. The second off-gas / NH heat exchanger is preferably arranged downstream of the first NH decomposition device (first pre-reactor) in the flow direction of NH.

[0216] In a second NH decomposition device (second pre-reactor), preferably arranged downstream of the second off-gas / NH heat exchanger in the flow direction of NH, further partial catalytic decomposition of the heated NH (first intermediate product gas) is carried out over an NH decomposition catalyst to produce a second intermediate product gas. The third off-gas / NH heat exchanger is preferably arranged downstream of the second NH decomposition device (second pre-reactor) in the flow direction of NH.

[0217] In a third NH3 decomposition device (main reactor), preferably located downstream of the third off-gas / NH3 heat exchanger in the NH3 flow direction, catalytic decomposition of the heated NH3 (second intermediate product gas) is carried out over an NH3 decomposition catalyst to produce a product gas.

[0218] The NH3 (or the first intermediate product gas or the second intermediate product gas) is heated by absorbing heat from the off-gas in the first off-gas / NH3 heat exchanger, the second off-gas / NH3 heat exchanger, and the third off-gas / NH3 heat exchanger.

[0219] The off-gas flows first through a first off-gas / NH3 heat exchanger, then through a second off-gas / NH3 heat exchanger, and then through a third off-gas / NH3 heat exchanger.

[0220] The NH3 (or first intermediate product gas or second intermediate product gas) first flows through a first off-gas / NH3 heat exchanger, absorbing heat from the off-gas therein. The heated NH3 then flows into a first NH3 decomposition device, where partial catalytic decomposition of the heated NH3 occurs over an NH3 decomposition catalyst to produce a first intermediate product gas. The first intermediate product gas thus formed, still containing a significant amount of undecomposed NH3, then flows through a second off-gas / NH3 heat exchanger, where it again absorbs heat from the off-gas. The heated first intermediate product gas then flows into a second NH3 decomposition device, where further partial catalytic decomposition of the heated NH3 occurs over an NH3 decomposition catalyst to produce a second intermediate product gas. The second intermediate product gas thus formed, still containing a significant amount of undecomposed NH3, then flows through a third off-gas / NH3 heat exchanger, where it again absorbs heat from the off-gas. Finally, the heated second intermediate product gas flows into a third NH3 decomposition device where catalytic decomposition of the heated NH3 occurs over an NH3 decomposition catalyst to produce product gas (see Figure 4).

[0221] The off-gas is preferably cooled in step (b) to a temperature T2 at which the off-gas is then transferred to an off-gas treatment system.

[0222] Preferably, the temperature T2 is at least 360°C, more preferably at least 370°C, even more preferably at least 380°C, most preferably at least 390°C, especially at least 400°C.

[0223] Preferably, the temperature T2 is at most 500°C, more preferably at most 480°C, even more preferably at most 460°C, most preferably at most 440°C, in particular at most 420°C.

[0224] The temperature T2 is preferably in the range of 400 to 450° C., more preferably 400 to 420° C. The ideal temperature T2 is X Dependent on inlet concentration and associated exothermicity. 1000 ppmv NOX For each 1000 ppm of NO off-gas, a ΔT of approximately 12K is expected. X This corresponds to approximately 80-90 K. The outlet temperature must not be too high, since catalyst stability in the off-gas treatment system is an important factor due to the high water content of the off-gas.

[0225] Very high NO X In the case of high concentration, it is preferable to provide a multi-stage arrangement of catalyst beds with multi-stage NH3 feed and intermediate heat exchangers according to the present invention. In this way, excessive temperatures are avoided. Furthermore, this allows for a higher NO2 (for the same catalyst volume) X and a significantly higher decomposition of N2O is possible.

[0226] Preferably, the off-gas entering the off-gas treatment system is at a temperature T2 that is relatively at least 20°C, preferably at least 40°C, more preferably at least 60°C, even more preferably at least 80°C, most preferably at least 100°C, especially at least 120°C lower than the temperature T1 of the off-gas leaving the calcination system, preferably the combustion device.

[0227] Preferably, the temperature T2 is relatively lower than the temperature T1 by at least 50°C, more preferably at least 100°C, even more preferably at least 150°C, most preferably at least 200°C, especially at least 250°C.

[0228] Step (c): In step (c) of the method of the present invention, the cooled off-gas may be transferred to an off-gas treatment system, i.e., from the calcination system from step (a) or from at least one heat exchanger from optional, preferred step (b).

[0229] In step (c) of the method of the present invention, the off-gas exiting the calcination system, preferably the combustion device, and optionally cooled in step (b), is transferred to an off-gas treatment system.

[0230] This can be done, for example, by a pipeline connecting the outlet of the calcination system, preferably the combustion device, to the inlet of the off-gas treatment system. This connection is preferably established via an off-gas duct. Since the method of the invention is preferably carried out at atmospheric pressure, no special requirements are usually imposed on the walls of such pipelines or off-gas ducts with regard to possible compressive stresses.

[0231] However, the pipeline or walls of the off-gas duct must be able to withstand the temperature of the off-gas exiting the firing system, preferably the combustion device, or entering the off-gas treatment system.

[0232] Steps (d) and (e) of the method of the present invention are carried out in the off-gas treatment system of the present invention. To this end, the off-gas treatment system comprises an N2O decomposition catalyst for step (d1) and / or an N2O reduction catalyst for step (d2), and an NO2O reduction catalyst for step (e). X and a reduction catalyst.

[0233] The off-gas treatment system of the present invention may further comprise at least one additional catalyst, or may further comprise at least one additional catalyst for the aforementioned N2O reduction, N2O decomposition or NO X If one of the reduction catalysts fulfills at least one additional functionality, the following steps (g1) to (g4) are carried out: (g1) cooling the off-gas preferably in an off-gas treatment system, preferably in at least one heat exchanger arranged upstream of the NH3 oxidation catalyst in the flow direction of the off-gas; (g2) reducing the NH content in the off-gas by oxidation with an oxidizing agent via an NH oxidation catalyst, the oxidizing agent preferably comprising O; (g3) reducing the HCN content in the off-gas by hydrolysis and oxidation of the hydrolysate with an oxidizing agent via an HCN decomposition catalyst; the oxidizing agent is preferably NO X and / or N2O, and (g4) reducing the CO content in the off-gas by chemical oxidation with an oxidant via a CO oxidation catalyst, the oxidant preferably comprising O; At least one of the following is preferably further performed in the off-gas treatment system of the present invention.

[0234] Step (d): In step (d) of the method of the present invention, the NO content in the off-gas is reduced, which can be achieved by (d1) decomposing NO via an NO decomposition catalyst and / or (d2) chemically reducing NO with a reducing agent via an NO reduction catalyst.

[0235] The decomposition of N2O forms N2 and O2 according to the following empirical reaction:

[0236] 2N2O → 2N2 + O2 Therefore, decomposition of N2O means decomposition into N2 and O2. An "N2O decomposition catalyst" in the context of the present invention catalyzes the decomposition of N2O. The achievable decomposition of N2O by catalytic decomposition depends not only on the type of N2O decomposition catalyst, i.e., its chemical nature and physical composition, and the existing pressure and temperature conditions, but also, in particular, on the selected space velocity, i.e., the ratio of the off-gas volumetric flow rate to the catalyst volume. However, the catalytic activity of an N2O decomposition catalyst need not be limited to this reaction only. For example, according to the present invention, an N2O decomposition catalyst may be used for, for example, chemical reduction of N2O and / or NO2. X It is quite possible, and indeed preferred, that further reactions, such as the chemical reduction of , can also be catalyzed. Whether such further reactions actually occur depends on the conditions of the individual case, in particular the type of catalyst, and the kinetics of any parallel processes, such as the presence or amount of reducing agent and the presence or amount of other co-reactants.

[0237] Chemical reduction of N2O by reducing agents forms different reaction products depending on the reducing agent.

[0238] In the case of the NH3 reducing agent preferred according to the invention, the chemical reduction of N2O forms, inter alia, N2 and H2O, for example as follows:

[0239] 3 N2O + 2 NH3 → 4 N2 + 3 H2O or 4 N2O + 4 NH3 + O2 → 6 N2 + 6 H2O Or else in co-reduction with NO as follows: 2 NO + N2O + 2 NH3 → 3 N2 + 3 H2O In the case of hydrocarbons, which are likewise preferred as reducing agents according to the invention, the chemical reduction of N2O forms, inter alia, CO and H2O, for example as follows:

[0240] (2n+1)N2O+C n H 2n+2 →(2n+1)N2+nCO+(n+1)H2O Or else the following CO2 and H2O: 4n NO+C n H 2n+2 →4n N2 + n CO2 + 2n H2O CO is also preferred as a reducing agent according to the invention, which can further react with N2O to give CO2, for example according to the following:

[0241] N2O+CO→N2+CO2.

[0242] An "N2O reduction catalyst" in the context of the present invention catalyzes the chemical reduction of N2O by a reducing agent. However, the catalytic activity of an N2O reduction catalyst need not be limited to this reaction alone. For example, according to the present invention, an N2O reduction catalyst may be used to, for example, decompose N2O and / or reduce NO X It is quite possible, and indeed preferred, that further reactions, such as the chemical reduction of , can also be catalyzed. Whether such further reactions actually occur depends on the conditions of the individual case, in particular the type of catalyst, and the kinetics of any parallel processes, such as the presence or amount of reducing agent and the presence or amount of other co-reactants.

[0243] Step (e): In step (e) of the method of the present invention, NO in the off-gas X The content is NO X NO by reducing agents via reduction catalysts X is reduced by chemical reduction of

[0244] Here, nitrogen oxides present in the off-gas, especially NO X Selective catalytic reduction (SCR) of NO X A reduction catalyst is preferred, which means that NO X The reduction catalyst mainly X This means that the catalyst catalyzes the oxidation of NH3 by the NH3 catalyst and does not, or only secondarily, catalyzes the oxidation of NH3 by any free oxygen (O2) present in the off-gas.

[0245] NO by reducing agents X The chemical reduction of forms different reaction products depending on the reducing agent. In the case of NH3 reducing agent preferred according to the present invention, NO X The chemical reduction of, in particular, NO X Depending on the type of reduction catalyst and the ratio of NO to NO2, N2 and H2O are formed, for example:

[0246] 4 NH3+2 NO+2 NO2→4 N2+6 H2O (high speed SCR) 4 NH3+4 NO+O2→4 N2+6 H2O (normal SCR) 8 NH3+6 NO2→7 N2+12 H2O(NO2SCR). A typical selective catalytic reduction is called fast SCR and is much faster than regular SCR or NO2 SCR.

[0247] In the context of the present invention, "NO X "Reduction catalyst" is a reducing agent that reduces NO X However, NO X The catalytic activity of the reduction catalyst is not necessarily limited to this reaction. For example, according to the present invention, NO X The reduction catalyst may be, for example, a catalyst for decomposing NO, chemically reducing NO, and / or reducing NO.X It is quite possible, and indeed preferred, that further reactions, such as the establishment of an equilibrium or the selective oxidation of excess NH by free O, can also be catalyzed. Whether such further reactions actually occur depends on the conditions of the individual case and the kinetics of any parallel processes, such as the presence or amount of reducing agent and the presence or amount of other co-reactants.

[0248] catalyst N2O decomposition catalysts are known per se and a wide variety of substance classes can be used. For decomposing N2O into N2 and O2, N2O decomposition catalysts with high catalytic activity in the temperature range of, for example, 350 to 600°C are preferred.

[0249] Examples of NO decomposition catalysts preferred according to the present invention are metal-containing zeolite catalysts, such as copper or cobalt, or especially iron-containing zeolite catalysts, noble metal catalysts, or transition metal oxide catalysts, such as cobalt oxide-containing catalysts. Examples of suitable catalysts are described, inter alia, by Kapteijn et al. in Appl. Cat. B: Environmental 9 (1996), 25-64, in US-A-5,171,553, in Actes du 2ieme Congres International sur la Catalyse, Technip, Paris 1961, 1937-1953, and in WO-A-01 / 58,570. When an iron-containing zeolite catalyst is used in the first catalyst bed, the NO still present in the gas is decomposed. X As expected, Kogel et al. in Catal. Comm. 2 (2001) 273-276 reported that the N2O / NO X The ratio described accelerates the desired NO decomposition through an activation effect (co-catalytic effect).

[0250] Further examples of N2O decomposition catalysts preferred according to the present invention are X Such an N2O decomposition catalyst is referred to for the purposes of this description as "NO XThese catalysts contain one or more catalytically active compounds of elements selected from groups 5 to 11 of the Periodic Table of the Elements (PTE). Compounds of elements from groups 9 to 11 of the PTE are particularly preferred. Among these, compounds of the elements Co, Pt, Pd, Ir, Rh, Ni and / or Cu are preferred, preferably Co, Rh, Ni and / or Cu, and here especially Co or Rh. Preference is given to catalysts for the decomposition of NO which are based on noble metals, preferably supported on refractory oxides, or on mixtures of transition metal oxides, in particular mixed oxides or simple transition metal oxides, in both cases in supported form or, preferably, as unsupported catalysts.

[0251] The catalytically active compounds themselves may be metal and / or oxide compounds, the latter either in the form of a single oxide or in the form of binary, ternary, or multi-component mixed oxides of different structural types, such as perovskites or spinels. These are described, for example, in Catalysis Letters 35 (1995) 372-382, Applied Catalysis 73 (1991) 165-171, Catal. Rev.-Sci. Eng.; 34 (4), 409-425 (1992) or Actes du 2ieme Congres International sur la Catalyse 97 (1961) 1937-1953. Mixtures of different catalytically active compounds may also be used. Particularly preferred examples of catalytically active compounds are metallic rhodium, rhodium oxides such as RhO2 or Rh2O3, CoO, Co2O3, Co-containing spinels such as Co3O4, CuCo, etc. 3-x O4, or Co-containing perovskites such as LaCoO3 or Co-containing perovskites substituted at the A and B sites.

[0252] The catalytically active compounds may be present in the catalyst in pure form or may be applied to or mixed with a suitable support material, in the former case these are so-called unsupported catalysts which may contain, in addition to the active compounds, binders or other production-related additives known to those skilled in the art, such as plasticizers, pore formers, fiber reinforcing agents or compaction aids.

[0253] Methods for producing such catalysts are known to those skilled in the art. In the case of "supported catalysts," the catalytically active compound is applied to a support material. As a result, the catalytically active compound is dispersed and stabilized against both mechanical and thermal stresses. Methods for producing such catalysts are also known to those skilled in the art. The support material is preferably a material that itself has a certain catalytic activity for N2O decomposition, such as a refractory oxide such as SiO2, TiO2, ZrO2, or Al2O3, or a mixture of two or more of these, or MgO, zeolite, hydrotalcite, or a mixture of two or more of these. It is preferable to use a catalyst that is essentially free of zeolite, preferably containing less than 15% (by weight) of zeolite, especially less than 5% (by weight) of zeolite.

[0254] Preferred support materials for Rh-containing compounds are ZrO2, TiO2, Al2O3, hydrotalcite, or zeolites, such as those of the MFI structure type. These are described, for example, in Chemical Engineering and Technology 24 (2001) 281-285 or Catalysis Today 35 (1997) 113-120. Particularly preferred supports for Rh-containing compounds are ZrO2, TiO2, and hydrotalcite. The Rh content of these catalysts is preferably 0.1% to 10% by weight, more preferably 0.5% to 5% by weight. In addition to Rh, the Rh-containing catalyst more preferably also contains CeO2. The proportion of CeO2 is preferably 5% to 50% by weight, particularly 10% to 30% by weight.

[0255] A preferred support for the Co-containing compound is a zeolite, or a preferred support comprises magnesium oxide. In the case of zeolites, Si-rich structural types such as MFI, BEA, FER, MEL, or MOR are particularly preferred. The preparation of such Co-doped zeolites is known to those skilled in the art. The magnesium oxide support can be pure MgO or an MgO-containing compound, such as hydrotalcite. Such catalysts are described, for example, in Appl. Catal. B: Environmental 7 (1996) 397-406 or Appl. Catal. B: Environmental 13 (1997) 69-79.

[0256] Particularly preferred are catalysts consisting essentially of at least one magnesium oxide compound and at least one cobalt oxide compound, where the content of the cobalt oxide compound is in the range of 0.1% to 50% by weight, and the content of the magnesium oxide compound is in the range of 50% to 99.9% by weight, in each case based on the total mass of the catalyst, and at least 30% of the Co atoms present in the catalyst are chemically trivalent. Such catalysts and their preparation are described in EP 1 257 347. Also particularly preferred when an oxidic Co compound is used as the active component are catalysts having a support consisting of at least 50% (by weight) MgO or a mixed oxide consisting of at least 50% by weight MgO, with a cerium oxide functional layer applied to the support. Such catalysts and their preparation are described in DE 10 2007 038 711 A1.

[0257] The NO decomposition catalysts can be in the form of shaped bodies of any size and geometry, preferably a geometry with a high surface area to volume ratio, which generates a minimum pressure drop when traversed. All geometries known in catalysis are typical, such as cylinders, hollow cylinders, multi-hole cylinders, rings, crushed granules, trilobes, or honeycomb structures.

[0258] NO reduction catalyst and NO XReduction catalysts are likewise known per se and a wide variety of substance classes can likewise be used, examples of which are metal-containing zeolite catalysts, such as copper- or cobalt-containing zeolite catalysts, or in particular iron-containing zeolite catalysts, or noble metal catalysts, or catalysts used in the known SCR (selective catalytic reduction) processes.

[0259] Preferably, an N2O decomposition catalyst and / or an N2O reduction catalyst and / or an NO X The reduction catalysts independently comprise a zeolitic material, preferably a zeolite comprising a transition metal (including a lanthanide), particularly iron, cobalt, or copper, more preferably an iron-containing zeolite, even more preferably an iron-containing zeolite, independently of the MFI, BEA, FER, MOR, FAU, and / or MEL structural types.

[0260] Preferably, an N2O decomposition catalyst and / or an N2O reduction catalyst and an NO X Both of the reduction catalysts independently comprise a zeolitic material, preferably a zeolite comprising a transition metal (including a lanthanide), particularly iron, cobalt, or copper, more preferably an iron-containing zeolite, even more preferably an iron-containing zeolite, independently of the MFI, BEA, FER, MOR, FAU, and / or MEL structural types.

[0261] These may be different catalysts or the same catalyst. The iron-containing zeolite catalyst particularly preferably used according to the present invention essentially contains one or more iron-containing zeolites, preferably more than 50 wt.%, in particular more than 70 wt.%. For example, in addition to Fe-ZSM-5 zeolite, further iron-containing zeolites, such as iron-containing zeolites of the FER type, may be present in the catalyst used according to the present invention.

[0262] Furthermore, the catalysts used according to the invention may contain further additives known to those skilled in the art, such as binders.

[0263] The iron content of the zeolites preferably used can be up to 25% based on the mass of the zeolite, but is preferably between 0.1% and 10%.

[0264] The method of the present invention also includes the use of zeolites in which the lattice aluminum is partially isomorphously substituted with one or more elements, for example, one or more elements selected from B, Be, Ga, Fe, Cr, V, As, Sb, and Bi. The use of zeolites in which the lattice silicon is isomorphously substituted with one or more elements, for example, one or more elements selected from Ge, Ti, Zr, and Hf, is also included. The precise details of the formation or structure of zeolites preferably used according to the present invention are described in Atlas of Zeolite Structure Types, Elsevier, 4th revised edition 1996, which is expressly incorporated herein by reference.

[0265] In the process of the present invention, zeolite catalysts treated with water vapor ("steamed" catalysts) are very particularly preferred. Such a treatment dealuminates the zeolite lattice. This procedure is known per se to those skilled in the art. These hydrothermally treated zeolite catalysts are notable for their particularly high activity in the process of the present invention. It is preferable to use hydrothermally treated zeolite catalysts which are supported with iron and have an extra-lattice to lattice aluminum ratio of at least 1:2, preferably between 1:2 and 20:1.

[0266] N2O decomposition catalyst and / or N2O reduction catalyst and NO X The reduction catalysts preferably each independently comprise a transition metal-containing zeolite, preferably each an iron-containing zeolite (Fe-zeolite), even more preferably each iron-containing zeolite having the same structural type, and most preferably the same external shape (e.g., honeycomb or pellet).

[0267] In a preferred embodiment, the N2O decomposition catalyst and the N2O reduction catalyst are formed from the same material.

[0268] In a preferred embodiment, the NO decomposition catalyst and NO X The reduction catalyst is formed from the same material.

[0269] In a preferred embodiment, an N2O reduction catalyst and an NOX The reduction catalyst is formed from the same material.

[0270] In a preferred embodiment, an N2O decomposition catalyst, an N2O reduction catalyst, and an NO X The reduction catalyst is formed from the same material.

[0271] The off-gas is preferably cooled after leaving the calcination system, preferably a combustion device, during optional and preferred step (b) of the method of the present invention, and steps (d1) and / or (d2) and / or (e) can introduce new heat.

[0272] NO and NO X Preferred catalyst for the decomposition of The N2O decomposition catalyst, N2O reduction catalyst, and NO X The reduction catalyst preferably comprises a zeolitic material ("zeolite") that independently comprises at least one transition metal (atomic numbers 21-30, 39-48, 57-80, 89-112) and / or at least one lanthanoid (also referred to as a "lanthanide"; atomic numbers 57-71). For purposes of description, transition metals and lanthanoids are collectively referred to as "transition metals" for simplicity. Preferred transition metals are iron ("Fe zeolites"), copper ("Cu zeolites"), and cobalt ("Co zeolites"). Iron-containing zeolitic materials (i.e., Fe zeolites) are particularly preferred and may comprise or contain not only iron but also other transition metals, such as manganese, vanadium, chromium, nickel, or mixtures.

[0273] The zeolitic material of the present invention preferably has high hydrothermal stability. Particularly preferred are SiO2-rich zeolites, referred to as "high silica zeolites," which have a high ratio of [SiO2] to [AlO2 - ] units and thus a molar Si / Al ratio of at least 8, preferably at least 9, more preferably at least 10, even more preferably at least 11, most preferably at least 12, especially at least 13.

[0274] The zeolitic materials preferred according to the present invention essentially have a zeolitic structure of the BEA, MFI, MOR, MEL or FER structure type, more preferably the MFI and BEA structure type, even more preferably the BEA structure type. In the case of the MFI structure type, the ZSM-5 type is particularly preferred. Further details of the structure types of zeolitic materials and their structural nomenclature can be found in Atlas of Zeolite Structure Types, Elsevier, 4th revised edition 1996.

[0275] Particularly preferred N2O decomposition catalysts, N2O reduction catalysts or NO X The reduction catalyst independently contains at least 50 wt. % Fe zeolite, preferably at least 70 wt. % Fe zeolite, based on the total weight of the zeolitic material, and a single structure type or several structure types may be present. In a preferred embodiment, in addition to the Fe-BEA zeolite, another Fe zeolite of a different structure type, preferably an Fe-MOR zeolite, is present.

[0276] The loading (doping) of the zeolite material with a transition metal / lanthanide can be carried out by related methods for loading or doping zeolites with transition metals / lanthanides known to those skilled in the art. The loading preferably proceeds from commercially available zeolite material in H form or, preferably, NH form, by ion exchange, aqueous phase, or solid-state reaction with a suitable transition metal salt. The supported zeolite material thus obtained is then calcined, preferably in air, in a furnace at a temperature ranging from 400 to 650°C. After calcination, the supported zeolite material is vigorously washed in distilled water, filtered, and then dried. A suitable binder, such as an aluminosilicate, boehmite, or silica sol, and optionally an auxiliary agent for plasticization or slip production, are preferably added to and mixed with the hydrous zeolite material thus obtained. In a preferred embodiment, the mixture thus obtained is extruded into a catalyst body (unsupported catalyst) and finally calcined. In another preferred embodiment, the mixture thus obtained is applied to a catalyst support (supported catalyst) and finally calcined. These methods are also well known to those skilled in the art and are established in many technical applications.

[0277] The present invention's N2O decomposition, N2O reduction, and NO X The reduction, NH3 oxidation, HCN decomposition, and CO oxidation catalysts can independently take the form of shaped bodies of any size and geometry, preferably with a large surface-to-volume ratio and a geometry that generates minimal pressure drop when the stream flows through them. Typical geometries are all those known in catalysis, such as cylinders, hollow cylinders, multi-hole cylinders, rings, trilobes, or star-shaped extrudates. Particularly preferred are monolithic catalyst elements infiltrated with parallel channels, such as monolithic honeycombs known as "catalytic honeycombs," known, for example, from the purification or detoxification of power plant off-gases or automobile exhaust gases.

[0278] Catalyst honeycomb, honeycomb body, and honeycomb body module The off-gas treatment system of the present invention or the catalyst bed contained therein preferably comprises a catalytic honeycomb, preferably a plurality of catalytic honeycombs, arranged parallel to one another with the honeycomb channels in the off-gas duct aligned longitudinally in the flow direction of the off-gas. The shape of the cross-sectional area of ​​the catalytic honeycomb (perpendicular to the flow direction of the off-gas) can in principle be freely selected. The catalytic honeycomb preferably has a rectangular or, in particular, square cross-sectional area, although other cross-sectional areas are also possible, in particular hexagonal, triangular, trapezoidal, etc. Suitable shapes are known to those skilled in the art. Therefore, the term "honeycomb" according to the present invention is not limited to rectangular or square cross-sectional areas.

[0279] When the inventive off-gas treatment system comprises a first reaction zone (first catalyst bed) and a second reaction zone (second catalyst bed) downstream in the flow direction of the off-gas, which is preferred according to the invention, the first and second reaction zones (first and second catalyst beds) preferably have several catalytic honeycombs arranged parallel to one another in honeycomb channels in an off-gas duct that are aligned longitudinally with respect to the flow direction of the off-gas.

[0280] In a preferred embodiment, several catalytic honeycombs, i.e., several monolithic honeycomb bodies, are combined to form a honeycomb body module, preferably by means of a metal frame open in the off-gas flow direction. Preferably, two, four or six honeycomb bodies, preferably monolithic honeycomb bodies, are combined in each case to form a honeycomb body module. This modular structure allows for good utilization of the available cross-sectional area of ​​the off-gas duct and for easy replacement of defective or deactivated honeycomb bodies.

[0281] The honeycomb body preferably has a rectangular cross section. The rectangular cross section preferably has a first edge length (perpendicular to the off-gas flow direction) in the range of 5 to 20 cm, more preferably 10 to 15 cm, and a second edge length (also perpendicular to the off-gas flow direction) in the range of 5 to 20 cm, preferably 10 to 15 cm. The height of the honeycomb body (in the off-gas flow direction) is preferably in the range of 5 to 25 cm, and more preferably in the range of 7.5 to 15 cm.

[0282] The so-called cell density, i.e., the density of a single catalyst honeycomb channel, is preferably 150 to 500 cpsi, preferably 180 to 450 cpsi (cells per square inch). 100 cpsi, i.e., 100 cells or honeycomb channels per square inch, is 1 cm 2 This corresponds to approximately 15.5 catalytic channels per nanotube.

[0283] Preferably, the individual honeycomb body modules are stacked one on top of the other in the flow direction and fixed by suitable mounting devices to achieve maximum utilization of the inlet area, i.e., the cross-sectional area of ​​the off-gas duct. Bypass flows between the individual honeycomb body modules or in the peripheral area between the outer edge of the honeycomb body module and the inner wall of the off-gas duct should be avoided. For this purpose, suitable seals are preferably applied between the individual honeycomb body modules and between the outer honeycomb body module and the inner wall. In the case of larger wall separations, cover plates are used that are attached to the inner wall of the off-gas duct in the flow direction in front of and / or behind the packing of the honeycomb body modules. The cover plates are preferably covered with seals at their contact points with the honeycomb body modules. The honeycomb body modules are preferably arranged and selected in terms of size so that the usable inlet area of ​​the catalyst is preferably at least 60%, more preferably at least 70%, and even more preferably at least 80% of the internal cross-sectional area of ​​the off-gas duct.

[0284] In the case of a circular off-gas duct or off-gas pipeline, gaps occurring in the edge regions of the packing of the honeycomb body modules are preferably not filled with specially adjusted honeycomb bodies but are closed by blind plates, unless they can be easily occupied by rectangular honeycomb body modules, which has the advantage that when replacing used honeycomb bodies, only standardized honeycomb bodies need to be replaced and no special adjustments are required.

[0285] When using an off-gas pipeline, it is also possible to use individual larger honeycomb bodies, preferably adapted to the pipeline cross section with a circular inlet cross section, several of which may be arranged successively in the flow direction in a preferred configuration, without the need to combine several honeycomb bodies parallel to one another to form a honeycomb body module.

[0286] In a preferred embodiment, the honeycomb bodies or honeycomb body modules are arranged in several layers offset along their longitudinal axes in the flow direction of the off-gas. The honeycomb bodies or honeycomb body modules are preferably arranged in 2 to 5 layers, more preferably in 2 to 3 layers. Between the layers, i.e., between the end faces of the honeycomb bodies or honeycomb body modules, a margin of preferably 3 to 30 mm, more preferably 4 to 20 mm, is preferably provided. The margin allows for intermediate, especially radial, mixing of the gas flow leaving the first layer of honeycomb bodies or honeycomb body modules. Furthermore, any possible slippage of unreacted reducing agent and / or its reaction products that have not yet been fully oxidized can be prevented from propagating from the first layer of honeycomb bodies to the subsequent second layer of honeycomb bodies.

[0287] NO X and optionally a reducing agent for NO, is preferably supplied and distributed via a manifold pipeline system having multiple openings or nozzles arranged in the off-gas duct or off-gas conduit upstream of each catalyst bed in the flow direction, preferably upstream of a packing of catalyst honeycombs as a honeycomb body or honeycomb body module.

[0288] The distribution pipes are preferably designed in the form of a grid or in the form of concentrically connected circles that extend as far as possible over the cross-sectional area of ​​the off-gas duct or the inlet area of ​​the catalyst bed.

[0289] The specific design and dimensions of these distributors, including appropriate outlet nozzles, are part of the expertise of catalytic off-gas scrubbing technology and are widely used, for example, in coal-fired power plant off-gas treatment.

[0290] NH3 oxidation catalyst NH3 oxidation catalysts are known to those skilled in the art.

[0291] The NH3 oxidation catalyst is preferably free of platinum group metals, and preferably free of precious metals.

[0292] For purposes of description, what is meant by "platinum group metal-free" is the essential absence of platinum group (i.e., Ru, Rh, Pd, Os, Ir, Pt) metals, although analytically detectable trace amounts of platinum group metals are possible. For purposes of description, what is meant by "noble metal-free" is the essential absence of noble metals, although analytically detectable trace amounts of noble metals are possible.

[0293] The NH3 oxidation catalyst is preferably an iron or copper containing zeolite, preferably an iron or copper containing zeolite of MFI, BEA, FER, MOR, FAU, AEI and / or MEL structure type (hereinafter referred to as NH3 oxidation active iron or copper containing zeolite catalyst).

[0294] Preferred platinum group metal-free NH3 oxidation catalysts are selected from transition metal oxides (e.g., Fe, Mn, Cu, Cr, Co, Ni...), metal-containing zeolites, as described, for example, in Handbook of Heterogeneous Catalysis, Wiley-VCH, edited by Ertl, Knotzinger, Schuth, Weitkamp, ​​2nd Ed. 2008, Volume 5, Chapter 11.5 "Solid Catalysts for the Oxidation of Volatile Organic Compounds".

[0295] Preferred NH3 oxidation catalysts are Cobalt catalysts; in particular Co3O4; mixed oxides derived from Co3O4, which preferably crystallize as Co3O4 in a spinel structure (Co3O4), where M is preferably selected from Zn, Cu, Fe, Mn and V 3-y M y O4); cobalt-containing zeolites preferably of the MFI, BEA, FER, MOR, FAU, CHA or AFI structural type; -Manganese catalyst; especially MnO with x=1-2 X ;MnO X Derived mixed oxide (Mn x-y M y O x ), where M is preferably selected from Zn, Cu, Fe and Mn; manganese-containing zeolites preferably of MFI, BEA, FER, MOR, FAU, CHA or AFI structural type; - Copper catalyst; especially CuO with x=0.5-1 X CuO, where M is preferably selected from Zn, Co, Fe and Mn; X Derived mixed oxide (Cu x-y M y O x ); copper-containing zeolites, preferably of the MFI, BEA, FER, MOR, FAU, CHA, AFI structural type; - catalysts, in particular in supported form silver, preferably supported on Al2O3, TiO2 or SiO2; more preferably, for example, X% Ag / TiO2, X% Ag / Al2O3 or X% Ag / SiO2, where X=1 to 10 in each case; Includes:

[0296] In a preferred embodiment, the device of the present invention does not contain any additional NH3 oxidation catalyst other than the iron or copper containing zeolite.

[0297] In a preferred embodiment, the NH3 oxidation catalyst, preferably the NH3 oxidation active iron-containing zeolite catalyst, has an iron to zeolite aluminum molar ratio n(Fe) / n(Al) of less than 0.50 and greater than 0.05, preferably less than 0.40 and greater than 0.05, more preferably less than 0.25 and greater than 0.05, and even more preferably less than 0.15 and greater than 0.05.

[0298] In a preferred embodiment, the NH3 oxidation catalyst, preferably the NH3 oxidation active copper-containing zeolite catalyst, has a copper to zeolite aluminum molar ratio n(Cu) / n(Al) of less than 1.00 to greater than 0.10, preferably less than 0.80 to greater than 0.10, more preferably less than 0.50 to greater than 0.10, and even more preferably less than 0.30 to greater than 0.10.

[0299] It has therefore been surprisingly found that iron- or copper-containing zeolites in which only a portion of the potentially available cation sites are occupied by Fe or Cu ions, such that the remaining cation sites are essentially filled by protons, have significantly increased activity for the oxidation of NH3 with free oxygen.

[0300] The ratio of iron or copper to zeolite aluminum can be adjusted by choosing the Al content in the synthesis of the zeolitic material, particularly via the proportions of Si and Al starting materials selected, and by subsequent loading with iron or copper ions.

[0301] In the synthesis of zeolites, selected Si and Al starting materials are typically heated in alkaline solution, often under high pressure, to induce crystallization and produce three-dimensionally categorised AlO2. - and SiO2 units, a microporous aluminosilicate, zeolite, is obtained. By controlled selection of synthesis conditions, for example by adding structure-directing agents, such as organic cations, it is possible to specifically adjust or control not only the Si / Al ratio and thus the Al content, but also the structure type of the zeolite. The synthesis method is industrially established. Zeolites of different structure types with different Si / Al ratios and containing different cations, for example in the form of Na or NH4, are commercially available.

[0302] Suitable methods known to those skilled in the art, such as liquid phase or solid state ion exchange, can be used to remove cations present in the zeolite, such as NH4 + This can result in controlled exchange of AlO2 with other cations, such as iron or copper ions (J. Weitkamp, ​​L. Puppe, Catalysis and Zeolites - Fundamentals and Applications, Springer-Verlag Berlin Heidelberg New York, 1999 or Kucherov, A.V., Linkin, AA: Solid state reactions as a method of introducing transition metal cations into high-silica zeolites, Russ. Chem. Rev. 1992, vol. 61, no. 9, pp. 925-943). If all the negative charges generated by the AlO2 units are compensated by cations, the so-called exchange level is 100%.

[0303] The exact Al content of the zeolitic material of the invention or of the shaped catalyst bodies produced therefrom, and the equally well-known Fe content, can be determined by X-ray fluorescence analysis (XRF), suitably in accordance with DIN EN 169-2 (section 5), after measuring the loss on ignition and after lithium tetraborate digestion.

[0304] If it is intended to determine the Al content of the parent zeolitic material subsequent to the finished compact, it should be noted that the compact may also contain Al-based binder components that are indistinguishable from zeolitic Al by XRF, e.g., allowing for the distinction between Al bound to the zeolitic structure and extra-lattice Al. 27 Further investigation of compacts by Al solid-state NMR is required. Those skilled in the art are familiar with the details of the basis, conduct, and evaluation of such studies (J. Weitkamp, ​​L. Puppe, Catalysis and Zeolites - Fundamentals and Applications, Springer-Verlag Berlin Heidelberg New York, 1999, Chapter 4.2 (NMR Spectroscopy; especially sections 4.2.4.1 ( 29 Si MAS NMR Spectroscopy of SiO4Tetrahedra in the Zeolite Framework)and 4.3.4.2( 27 Al NMR Spectroscopy of Framework and Non-Framework Aluminum in Zeolites)).

[0305] The NH3 oxidation catalyst, preferably the NH3 oxidation active iron-containing zeolite catalyst, preferably has a total iron content (reported as mass content of Fe2O3) of less than 10.0 wt% to more than 2.0 wt%, preferably less than 7.0 wt% to more than 2.0 wt%, more preferably less than 5.0 wt% to more than 2.0 wt%, and even more preferably less than 4.0 wt% to more than 2.0 wt%.

[0306] The NH3 oxidation catalyst, preferably the NH3 oxidation active copper-containing zeolite catalyst, preferably has a total copper content (reported as the mass content of Cu2O) of less than 9.0 wt% to more than 1.5 wt%, preferably less than 6.5 wt% to more than 1.5 wt%, more preferably less than 4.5 wt% to more than 1.5 wt%, and even more preferably less than 3.5 wt% to more than 1.5 wt%.

[0307] In a preferred embodiment, the NH3 oxidation catalyst, preferably an NH3 oxidation active iron or copper containing zeolite catalyst, configured to selectively oxidize NH3 with O2 to N2 and HO, is introduced in the form of a particulate bed, the particles having an equivalent diameter, defined as the diameter of a spherical particle of equivalent volume, of 3.5 to 5.5 mm, and the ratio of the geometrically detectable outer surface area of ​​the particles to the volume of the particulate bed is 10000±500 h -1 The reactor was operated isothermally in an axial flow tubular reactor with an internal diameter of 20 ± 3 mm, in which a volume of 8.0 ± 0.5 ml was added to 1000 m3 of the reactor, which was contacted with a volumetric flow of a gas mixture consisting of 500 ± 50 ppmv NH3, 2.5 ± 0.1 vol.% O2, and 0.30 ± 0.05 vol.% H2O in N2 at a space velocity based on standard conditions (0 °C; 1.01325 bara). 2 / m 3 1500m from 2 / m 3 and a total pressure of 6±1500 bara and a temperature of 380° C.±5 K results in an NH conversion of at least 50%, preferably at least 60%, more preferably at least 70%, even more preferably at least 80%, especially at least 90%.

[0308] In a preferred embodiment, an N2O decomposition catalyst and / or an N2O reduction catalyst and / or an NO X The reduction catalyst and / or the NH3 oxidation catalyst independently have a honeycomb monolithic structure.

[0309] In a preferred embodiment, an N2O decomposition catalyst and / or an N2O reduction catalyst and / or an NO X The reduction catalyst and / or the NH3 oxidation catalyst independently have a honeycomb monolithic structure.

[0310] In a preferred embodiment, the NH3 oxidation catalyst and the N2O decomposition catalyst are formed from the same material.

[0311] In a preferred embodiment, the NH3 oxidation catalyst and the N2O reduction catalyst are formed from the same material.

[0312] In a preferred embodiment, an NH3 oxidation catalyst and NO X The reduction catalyst is formed from the same material.

[0313] In a preferred embodiment, NH3 oxidation catalyst, NO X The reduction catalyst and the N2O decomposition catalyst are formed from the same material.

[0314] Preferred variant of the combination of steps (d) and (e): In a preferred embodiment, steps (d1) and / or (d2) and / or (e) of the method of the present invention are carried out at different temperatures, i.e. at different temperature levels, with the steps carried out before or upstream in the flow direction of the off-gas preferably proceeding at a higher temperature than the steps carried out after or downstream in the flow direction of the off-gas.

[0315] However, depending on the nature of the catalyst used, the steps may not be completely separable from one another locally or in time. If the catalyst used is simultaneously suitable for catalyzing two or more of steps (d1), (d2) and (e), these steps may proceed simultaneously and / or sequentially. For this purpose, in the flow direction of the off-gas, it is possible to consider individual segments of one and the same catalyst through which the off-gas flows continuously and in which different reactions may prevail. Which reaction prevails in which section depends, in particular, on the respective reaction kinetics, the local temperature, the local concentrations of the reactants, which may include the concentration of the reducing agent and / or the concentration of the cocatalytic active species.

[0316] The off-gas treatment system of the present invention is particularly used to carry out steps (d) and (e) of the method of the present invention, however, in addition to steps (d) and (e), further steps and chemical reactions may also be carried out within the off-gas treatment system.

[0317] This preferably relates to the installation of a catalyst bed arranged downstream in the flow direction of the off-gas for the oxidation of the incompletely converted reducing agent or its still incompletely oxidized reaction products, i.e., for example, the oxidation of NH (NH oxidation catalyst) or CO (CO oxidation catalyst; if hydrocarbons are used as reducing agents). In such an embodiment, the off-gas is preferably cooled before being introduced into the downstream catalyst bed, i.e., the oxidation of NH and / or CO is preferably carried out at a lower temperature than in steps (d) and (e).

[0318] In carrying out steps (d) and (e) of the process of the invention, there are, according to the invention, different preferred variants of the process regime which may differ from one another with regard to the order of reactions proceeding, the catalysts used, the reducing agents used, the space velocity and other reaction conditions.

[0319] In a preferred embodiment, these reactions take place in a common reaction zone (catalyst bed) with an upstream device for metering a reducing agent into the off-gas.

[0320] In another preferred embodiment, these reactions are carried out in two separate reaction zones (catalyst beds) arranged in series, of which preferably at least one reaction zone, and preferably both reaction zones, is independently equipped upstream with a device for metering a reducing agent into the off-gas, in which case the off-gas flows first through the first reaction zone and subsequently through the second reaction zone.

[0321] Particularly preferred variants / embodiments are: [a] (d2) Chemical reduction of N2O with NH3 and (e) NO with NH3, preferably together in one reaction zone. X Chemical reduction of; [b] (d2) Chemical reduction of N2O with hydrocarbons (CH4, natural gas, etc.) and (e) NO with NH3, preferably together in one reaction zone. X Chemical reduction of; [c] (d1) decomposition of N2O and (e) decomposition of NO with NH3, preferably together in one reaction zoneX Chemical reduction of; [d] (d1) decomposition of N2O and (d2) chemical reduction of N2O with NH3 and (e) decomposition of NO with NH3, preferably together in one reaction zone X Chemical reduction of; [e] (d1) decomposition of N2O and (d2) chemical reduction of N2O with hydrocarbons (CH4, natural gas, etc.) and (e) NO with NH3, preferably together in one reaction zone. X Chemical reduction of; [f] (d1) decomposition of N2O, preferably in a first reaction zone; then (e) decomposition of NO with NH3, preferably in a second reaction zone. X Chemical reduction of; [g] (d1) preferably incomplete decomposition of N2O in a first reaction zone; then (d2) chemical reduction of residual N2O with NH3 and (e) preferably decomposition of NO2O with NH3 in a second reaction zone. X Chemical reduction of; [h] (d1) preferably incomplete decomposition of N2O in a first reaction zone; then (d2) chemical reduction of the residual N2O with hydrocarbons (CH4, natural gas, etc.) and (e) preferably decomposition of NO with NH3 in a second reaction zone. X Chemical reduction of; [i] (d1) preferably incomplete decomposition of N2O in the first reaction zone; then (d1*) decomposition of residual N2O and (e) preferably decomposition of NO with NH3 in the second reaction zone. X Chemical reduction of; [j] (d1) preferably incomplete decomposition of N2O in a first reaction zone; then (d1*) decomposition of residual N2O, and (d2) chemical reduction of residual N2O with NH3, and (e) preferably reduction of NO2O with NH3 in a second reaction zone. X Chemical reduction of; [k] (d1) preferably incomplete decomposition of N2O in a first reaction zone; then (d1*) decomposition of residual N2O, and (d2) chemical reduction of residual N2O with hydrocarbons (CH4, natural gas, etc.), and (e) preferably reduction of NO2O with NH3 in a second reaction zone. X Chemical reduction of; [l](e) Preferably NO in the first reaction zone X incomplete chemical reduction of NO; ​​then (d1) decomposition of NO and (e*) preferably residual NO with NH in a second reaction zone. X Chemical reduction of; [m](e) preferably NO in the first reaction zone X incomplete chemical reduction of NO; ​​then (d1) decomposition of NO, and (d2) chemical reduction of NO with NH, and (e*) decomposition of residual NO preferably with NH in a second reaction zone. X chemical reduction of [n](e) preferably NO in the first reaction zone X incomplete chemical reduction of NO; ​​then (d1) decomposition of NO and (d2) chemical reduction of NO with hydrocarbons (CH, natural gas, etc.) and (e*) removal of residual NO preferably with NH in a second reaction zone. X Chemical reduction of Includes:

[0322] However, this does not mean that the explicitly mentioned reactions must be the only reactions occurring in the respective reaction zones. Depending on the catalyst used, further reactions, not explicitly mentioned but which may proceed in parallel, may also preferably occur simultaneously according to the present invention. The explicitly mentioned reactions are therefore the only reactions which at least occur in each variant / embodiment.

[0323] NO X , N2O and NH3 are present in the mixture, and the catalyst used is the conversion of NO by NH3 X and the chemical reduction of N2O by NH3, X The chemical reduction of NO is typically much faster than the chemical reduction of NO by NH. If the catalyst used also catalyzes the decomposition of NO, the decomposition of NO typically overlaps with the chemical reduction of NO by NH, and the extent of chemical reduction of NO can be increased by increasing the amount of NH metered in.

[0324] For purposes of illustration, an "*" indicates a component process step that has previously been performed only partially in the same type of component process step; the component process step identified by the "*" then continues the previously performed component process step only partially, but possibly in a different reaction zone or a different catalyst bed. As with all other process steps, unless otherwise specified, the results achieved at the end of all component process steps are not quantified. For example, in the first component process step (e), NO X If is incompletely chemically reduced, the fact that component method step (e*) is subsequently carried out means that at the end of component method step (e*), NO X This does not necessarily mean that the total amount of NO must be completely chemically reduced, i.e., to 0.0 ppmv. Instead, at the end of component method step (e*), the residual amount of NO X It is entirely possible that still exists.

[0325] The off-gas treatment system comprises at least one injection site for the reducing agent. The off-gas treatment system may comprise several injection sites for the reducing agent.

[0326] The mode of introduction of the reducing agent into the off-gas stream to be treated can be freely configured according to the invention, provided that it is not introduced into the N2O reduction catalyst or the NO2O reduction catalyst in the flow direction. X It is carried out upstream of the reduction catalyst. The reducing agent can be introduced in the form of a gas that evaporates in the off-gas stream to be treated, or in the form of a liquid or aqueous solution. The supply is carried out by a suitable device, for example a suitable pressure valve or a suitably designed nozzle, leading to a mixer for the off-gas stream to be treated and the supply of reducing agent. NO X If different reducing agents for N2O and N2O are used, the feed and introduction into the off-gas can be done separately or together.

[0327] In the case of a catalyst bed configuration as a packing of a catalyst honeycomb or honeycomb body module, NO is introduced into one or more reaction zones (catalyst beds).X The supply and distribution of the reducing agent for the NO and optionally the N2O is preferably carried out via a manifold pipeline system having multiple openings or nozzles arranged upstream of the respective reaction zone (catalyst bed) in the flow direction of the off-gas, i.e., upstream of the packing of the catalytic honeycomb or honeycomb module.

[0328] The distributor is preferably designed in the form of a grid or concentrically connected circles extending as far as possible over the cross-sectional area of ​​the off-gas duct or the inlet area of ​​the reaction zone (catalyst bed).

[0329] The specific design and dimensions of these distributors, including appropriate outlet nozzles, are part of the expertise of catalytic off-gas scrubbing technology and are widely used, for example, in coal-fired power plant off-gas treatment.

[0330] The off-gas treatment system of the present invention may include a single reaction zone, in which case the catalyst used in the single reaction zone may serve as an N2O decomposition catalyst and / or an N2O reduction catalyst, and as a NO X In this case, steps (d) and (e) of the method of the present invention are carried out essentially simultaneously in this reaction zone. However, it should be noted that the reaction rates of the individual conversions may vary considerably. For example, the reduction of NO with NH3 as a reducing agent may be significantly different depending on the catalyst material used. X The chemical reduction of NO by NH3 can proceed much more rapidly than the chemical reduction of NO by NH3. X When NO and N2O are in the mixture and NH3 is supplied as a reducing agent, a different reaction occurs in the front section of a single reaction zone than in the rear section of a single reaction zone. In the front section, due to faster kinetics, NO X The chemical reduction of NO proceeds mainly in the posterior section. X Once most of the N2O is decomposed, the chemical reduction of N2O proceeds.

[0331] Alternatively, the off-gas treatment system may comprise several reaction zones, which is preferred according to the invention. If several reaction zones are included, they are preferably in series, so that the off-gas flows through them one after the other, first the first reaction zone, then the second reaction zone and, if appropriate, the third reaction zone.

[0332] In a preferred embodiment, the reaction zones are each spatially separated catalyst beds.

[0333] In a preferred embodiment, the off-gas undergoes the steps of the method of the present invention in one of the following orders:

[0334] (i) (a) → (b) → (c) → (d1) → (e); step (d1) preferably proceeds in the first reaction zone; and step (e) proceeds in the second reaction zone.

[0335] (ii) (a)→(b)→(c)→(e)→(d2); step (e) preferably proceeds in the first reaction zone; and step (d2) proceeds in the second reaction zone; (iii) (a) → (b) → (c) → (e) → (d2) → (d1); step (e) preferably proceeds in the first reaction zone; step (d2) proceeds in the second reaction zone; step (d1) proceeds in the third reaction zone; (iv) (a) → (b) → (c) → (e) → (d1) + (d2); step (e) preferably proceeds in a first reaction zone; step (d1) and step (d2) proceed in a second reaction zone.

[0336] (v) (a)→(b)→(c)→(e)→(d1); step (e) preferably proceeds in the first reaction zone; step (d1) proceeds in the second reaction zone; (vi) (a) → (b) → (c) → (d1) + (e) → (e*); preferably, step (d1) and step (e) (incompletely) proceed in the first reaction zone; the remainder of step (e*) proceeds in the second reaction zone; (vii) (a) → (b) → (c) → (d1) + (e) → (e*) + (d2); step (d1) and step (e) (incompletely) preferably proceed in the first reaction zone; step (d2) and the remainder of step (e*) proceed in the second reaction zone; (viii) (a) → (b) → (c) → (d1) + (d2) + (e) → (d1*) + (d2*) + (e*); step (d1) (incomplete) and step (d2) (incomplete) and step (e) (incomplete) preferably proceed in a first reaction zone that does not contain a zeolitic material as a catalyst; and the remainder of step (d2*) and the remainder of step (d2*) and the remainder of step (e*) preferably proceed in a second reaction zone that contains a zeolitic material as a catalyst; (ix) (a) → (b) → (c) → (d1) + (d2) + (e) → (d1*) + (d2*) + (e*); step (d1) (incomplete) and step (d2) (incomplete) and step (e) (incomplete) preferably proceed in a first reaction zone which preferably contains a zeolitic material as a catalyst; and the remainder of step (d1*) and the remainder of step (d2*) and the remainder of step (e*) preferably contain NO as a catalyst. X proceeds in a second reaction zone containing a sensitive N2O decomposition catalyst; (x) (a) → (b) → (c) → (d1) → (d1*) + (d2) + (e); step (d1) (incompletely) preferably proceeds in a first reaction zone which preferably comprises a zeolitic material as a catalyst; and step (d1*) and step (d2) and the remainder of step (e) preferably proceed in a second reaction zone which preferably comprises a zeolitic material as a catalyst; (xi) (a) → (b) → (c) → (d1) → (d1*) + (d2) + (e); step (d1) is (incompletely), preferably with NO as catalyst. Xand step (d1*), step (d2), and the remainder of step (e) preferably proceed in a second reaction zone containing a zeolite material as a catalyst.

[0337] However, it is also possible for two or more reaction zones to be implemented by a single catalyst bed. Two reaction zones on a shared catalyst bed can be formed by supplying a reducing agent, particularly to the center of the catalyst bed (or another location along the longitudinal extent). In this case, since there is no reducing agent upstream of the feed point, steps (d2) and (e) of the method of the present invention cannot be carried out due to the absence of a reducing agent. What then occurs upstream is essentially the decomposition of NO in step (d1) (first reaction zone). Since there is a reducing agent downstream of the feed point, steps (d2) and (e) of the method of the present invention can be carried out, possibly overlapping with step (d1) (second reaction zone) of the method of the present invention. Again, due to different reaction rates, different reactions may occur in the front section of each reaction zone than in the rear section of each reaction zone, but in both cases, the first and second reaction zones are identical, since the absence of a reducing agent prevents the chemical reduction of NO in the first reaction zone and the decomposition of NO. X They differ from each other in that no chemical reduction of

[0338] In a particularly preferred embodiment, the off-gas treatment system comprises a first reaction zone and a second reaction zone. Additional reaction zones may be present.

[0339] In a preferred embodiment, the first and second reaction zones are spatially separated from one another. In this case, they are preferably separate catalyst beds. In the case of spatial separation of catalyst beds, the temperature of the second catalyst bed or the gas stream entering it can be adjusted by removing or adding heat so that it is lower or higher than the temperature of the first catalyst bed. The temperature of a single catalyst bed can be suitably determined as the arithmetic mean of the temperatures of the gas streams at the inlet and outlet from the catalyst bed.

[0340] In a preferred embodiment, the temperature in the first reaction zone (within the first catalyst bed) is greater than the temperature in the second reaction zone (within the second catalyst bed).

[0341] Preferably the temperature in the first reaction zone is at least 450°C, more preferably at least 500°C, even more preferably at least 550°C, most preferably at least 600°C, especially at least 650°C.

[0342] Preferably, the temperature in the second reaction zone (within the second catalyst bed) is at most 600°C, more preferably at most 550°C, even more preferably at most 500°C, most preferably at most 450°C, especially at most 400°C.

[0343] In a preferred embodiment, the temperature in the first reaction zone (within the first catalyst bed) is relatively higher than the temperature in the second reaction zone (within the second catalyst bed) by at least 20°C, more preferably at least 40°C, even more preferably at least 60°C, most preferably at least 80°C, and especially at least 100°C.

[0344] In another preferred embodiment, the temperature of the second reaction zone (within the second catalyst bed) is relatively higher than the temperature of the first reaction zone (within the first catalyst bed) by at least 20°C, more preferably at least 40°C, even more preferably at least 60°C, most preferably at least 80°C, especially at least 100°C.

[0345] In a preferred embodiment, the temperature in the first reaction zone (within the first catalyst bed) is relatively higher than the temperature in the second reaction zone (within the second catalyst bed) by at least 120°C, more preferably at least 140°C, even more preferably at least 160°C, most preferably at least 180°C, especially at least 200°C.

[0346] In another preferred embodiment, the temperature in the second reaction zone (within the second catalyst bed) is relatively higher than the temperature in the first reaction zone (within the first catalyst bed) by at least 120°C, more preferably at least 140°C, even more preferably at least 160°C, most preferably at least 180°C, especially at least 200°C.

[0347] Preferably, the temperature of the off-gas entering the first reaction zone (first catalyst bed) is at least 400°C, more preferably at least 425°C, even more preferably at least 450°C, and most preferably at least 500°C.

[0348] Preferably, the temperature of the off-gas leaving the second reaction zone (from the second catalyst bed) is at most 600°C, more preferably at most 550°C, even more preferably at most 500°C.

[0349] In a preferred embodiment, the temperature of the off-gas entering the first reaction zone (first catalyst bed) is relatively at least 20 K, more preferably at least 40 K, even more preferably at least 60 K, most preferably at least 80 K, especially at least 100 K higher than the temperature of the off-gas entering the second reaction zone (second catalyst bed).

[0350] In a preferred embodiment, the temperature of the off-gas entering the second reaction zone (second catalyst bed) is relatively at least 10 K, more preferably at least 20 K, even more preferably at least 30 K, most preferably at least 40 K, especially at least 50 K higher than the temperature of the off-gas entering the first reaction zone (first catalyst bed).

[0351] In a preferred embodiment, the temperature of the first reaction zone (within the first catalyst bed) is relatively higher than the temperature of the second reaction zone (within the first catalyst bed) by at least 120 K, more preferably at least 140 K, even more preferably at least 160 K, most preferably at least 180 K, especially at least 200 K.

[0352] In a preferred embodiment, the temperature of the second reaction zone (within the second catalyst bed) is relatively higher than the temperature of the first reaction zone (within the first catalyst bed) by at least 120 K, more preferably at least 140 K, even more preferably at least 160 K, most preferably at least 180 K, especially at least 200 K.

[0353] In another preferred embodiment, the first and second reaction zones are spatially connected to one another, in which case the catalyst bed, preferably a shared catalyst bed, is divided into reaction zones by external influences, in particular by injection sites of the reducing agent, and the reducing agent is not uniformly present throughout the catalyst bed.

[0354] Preferably, the first reaction zone and the second reaction zone are located within a common vessel.

[0355] Preferably, the off-gas temperature of the first reaction zone and the second reaction zone is in each case independently up to 500°C, preferably in each case independently in the range from 350 to 450°C.

[0356] In a preferred embodiment, the space velocity in the first reaction zone is greater than the space velocity in the second reaction zone, preferably at least 1.2 times, more preferably at least 1.4 times, even more preferably at least 1.6 times, most preferably at least 1.8 times, and especially at least 2.0 times greater than the space velocity in the second reaction zone.

[0357] In another preferred embodiment, the space velocity in the second reaction zone is greater than the space velocity in the first reaction zone. Preferably, the space velocity in the second reaction zone is at least 1.5 times greater than the space velocity in the first reaction zone, more preferably at least 2.0 times greater, even more preferably at least 3.0 times greater, most preferably at least 5.0 times greater, and especially at least 10.0 times greater.

[0358] In the context of the present invention, "space velocity" refers to the quotient of the volumetric flow rate of a gas mixture conducted through a catalyst bed based on the volume of the catalyst or catalyst bed (measured at 0°C and 1.014 bara, typically standard m 3 h -1 The space velocity can therefore be adjusted by the volumetric flow rate of the gas and / or the amount of catalyst.

[0359] Preferably, the off-gas entering the off-gas treatment system is at a temperature of at least 300°C, more preferably at least 350°C, even more preferably at least 400°C, most preferably at least 425°C, especially at least 450°C.

[0360] Preferably, the off-gas entering the off-gas treatment system is at a temperature of at least 500°C, more preferably at least 550°C, even more preferably at least 600°C, most preferably at least 625°C, especially at least 650°C.

[0361] Preferably, the off-gas entering the off-gas treatment system is at a temperature of at most 825°C, more preferably at most 800°C, even more preferably at most 775°C, most preferably at most 750°C, especially at most 725°C.

[0362] Preferably, the off-gas entering the off-gas treatment system is at a temperature of at most 700°C, more preferably at most 650°C, even more preferably at most 600°C, most preferably at most 550°C, especially at most 500°C.

[0363] In a preferred embodiment, the off-gas entering the off-gas treatment system is at a pressure of up to 1.4 bara, preferably up to 1.3 bara, more preferably up to 1.2 bara.

[0364] In another preferred embodiment, the off-gas is under reduced pressure, preferably about -5 mbar, when it enters the off-gas treatment system, which has the advantage that no gas is released into the environment in the event of a possible leak.

[0365] Preferably, the off-gas entering the off-gas treatment system contains at least 10%, more preferably at least 20%, even more preferably at least 30%, most preferably at least 40%, especially at least 50% NO X has an oxidation degree of

[0366] Preferably, the off-gas entering the off-gas treatment system contains up to 90%, more preferably up to 80%, even more preferably up to 70%, most preferably up to 60%, especially up to 50% NO X has an oxidation degree of

[0367] Depending on the combustion temperature, the degree of oxidation may also be significantly lower, with the degree of oxidation decreasing with increasing combustion temperature. Preferably, the off-gas entering the off-gas treatment system contains at most 15%, more preferably at most 12.5%, even more preferably at most 10%, most preferably at most 7.5%, especially at most 5.0% NO X has an oxidation degree of

[0368] Preferably, the off-gas entering the off-gas treatment system has an O2 content of less than 2.0% by volume.

[0369] Preferably, the off-gas entering the off-gas treatment system has an O2 content greater than 4.0% by volume.

[0370] In step (d) of the method of the present invention, the NO content in the off-gas is reduced. This can be achieved in various ways, namely (d1) decomposition of NO via an NO decomposition catalyst and / or (d2) chemical reduction of NO with a reducing agent via an NO reduction catalyst. Step (d) of the method of the present invention is carried out in an off-gas treatment system.

[0371] In a preferred embodiment, step (d) comprises reducing the N2O content in the off-gas by (d1) decomposition of N2O over an N2O decomposition catalyst.

[0372] In a preferred embodiment, the NO decomposition catalyst comprises a zeolitic material, preferably a zeolite comprising a transition metal (including lanthanides), in particular iron, cobalt or copper, more preferably an iron-containing zeolite, even more preferably an iron-containing zeolite of the MFI, BEA, FER, MOR, FAU and / or MEL structural type.

[0373] In another preferred embodiment, the NO decomposition catalyst is a catalyst for decomposing NO within the context of the present invention. X The catalyst is a sensitive NO decomposition catalyst, which has already been described in detail above. In this case, the off-gas is preferably first passed through step (e), i.e., the NO in the off-gas is X The content is followed by off-gas NO X Preferably quantitatively, NO is decomposed before contact with a sensitive NO decomposition catalyst. X NO by reducing agents via reduction catalysts X It is first reduced by chemical reduction of

[0374] Preferably, the N2O decomposition catalyst is disposed in a radial basket through which the flow passes axially.

[0375] The N2O decomposition catalyst is preferably in particulate form and comprises at least 50 particles.

[0376] In a preferred embodiment, step (d) comprises (d2) reducing the NO content in the off-gas by chemical reduction of NO with a reducing agent via an NO reduction catalyst, preferably the NO reduction catalyst comprises a zeolitic material, preferably a zeolite comprising a transition metal (including lanthanides), in particular iron, cobalt or copper, more preferably an iron-containing zeolite, even more preferably an iron-containing zeolite of the MFI, BEA, FER, MOR, FAU and / or MEL structural type.

[0377] Preferably, the N2O reduction catalyst is disposed in a radial basket through which the flow passes axially.

[0378] The N2O reduction catalyst is preferably in particulate form and comprises at least 50 particles.

[0379] In a preferred embodiment, step (d) comprises determining the NO content in the off-gas by: - (d1) decomposing N2O via an N2O decomposition catalyst, preferably the N2O decomposition catalyst being a zeolitic material, preferably a zeolite containing a transition metal (including lanthanides), in particular iron, cobalt or copper, more preferably an iron-containing zeolite, even more preferably an iron-containing zeolite of the MFI, BEA, FER, MOR, FAU and / or MEL structural type; and - (d2) chemical reduction of N2O with a reducing agent via an N2O reduction catalyst, preferably wherein the N2O reduction catalyst comprises a zeolitic material, preferably a zeolite containing a transition metal (including lanthanides), in particular iron, cobalt or copper, more preferably an iron-containing zeolite, even more preferably an iron-containing zeolite of the MFI, BEA, FER, MOR, FAU and / or MEL structural type, This includes reducing the amount of

[0380] Preferably, the reducing agent in step (d2) is selected from NH3, hydrocarbons, CO, H2 and mixtures thereof, preferably NH3; In a preferred embodiment, the reducing agent in step (d2) is NH, preferably used in an amount of 0.5 to 2.0 molar parts, preferably 0.8 to 1.8 molar parts, based on the molar proportion of NO to be chemically reduced, i.e., based on the amount of NO at the inlet to the catalyst bed of the NO reduction catalyst.

[0381] In a preferred embodiment, the reducing agent in step (d2) is NH3, preferably used in an amount of 0.5 to 2.0 molar parts, more preferably 0.8 to 1.8 molar parts, based on the molar amount of NO in the off-gas at the inlet to the catalyst bed of the NO reduction catalyst. If step (e) similarly proceeds with a catalyst bed of the NO reduction catalyst, this amount is X Any required amount of NH3 is added for reduction.

[0382] In another preferred embodiment, the reducing agent is a hydrocarbon or a mixture of two or more hydrocarbons, preferably used in an amount of 0.2 to 1.0 molar part, more preferably 0.2 to 0.7 molar part, based on the molar amount of NO in the off-gas at the inlet to the catalyst bed of the NO reduction catalyst. If step (e) also proceeds with a catalyst bed of the NO reduction catalyst, this amount is X Any required amount of NH3 for reduction is added as well.

[0383] The reducing agent may also already be present in the off-gas, for example in the form of residual combustion gases and / or their oxidation products. In that case, the method of the present invention can be used to reduce nitrogen oxides (NO X and N2O), but also reduces the content of these impurities (residual combustion gases and / or their oxidation products).

[0384] In step (e) of the method of the present invention, NO in the off-gas X (i.e., NO and NO2) content is reduced. X NO by reducing agents via reduction catalysts X Step (e) of the method of the present invention is also carried out in an off-gas treatment system.

[0385] NO X The reduction catalyst is preferably a zeolitic material, preferably a zeolite comprising a transition metal (including lanthanides), in particular iron, cobalt or copper, more preferably an iron-containing zeolite; even more preferably an iron-containing zeolite of the MFI, BEA, FER, MOR, FAU and / or MEL structural type.

[0386] Preferably, NO X The reduction catalyst is placed in a radial basket through which the flow passes axially.

[0387] Preferably, NO X The reduction catalyst is in particulate form and comprises at least 50 particles.

[0388] Preferably, the reducing agent in step (e) is selected from NH3, hydrocarbons, CO, H2 and mixtures thereof, preferably NH3.

[0389] Preferably, the reducing agent in step (e) is chemically reduced NO X NH3 used in an amount of 0.9 to 2.5 molar parts, preferably 1.0 to 1.4 molar parts, preferably 1.0 to 1.2 molar parts based on the molar ratio of

[0390] In a preferred embodiment, the reducing agent in step (d2) is the same as the reducing agent in step (e), preferably NH3.

[0391] In addition to NH3, other nitrogen-containing reducing agents, such as hydrogen compounds of nitrogen, such as azanes, hydroxyl derivatives of azanes, and amines, oximes, carbamates, urea, or urea derivatives, are also suitable in principle in step (d2) and / or (e) of the method of the present invention. Examples of azanes include hydrazine and, very particularly, ammonia. Examples of hydroxyl derivatives of azanes include hydroxylamine. Examples of amines include primary aliphatic amines such as methylamine. Examples of carbamates include ammonium carbamate. Examples of urea derivatives include N,N'-substituted ureas such as N,N'-dimethylurea. Urea and urea derivatives are preferably used in the form of an aqueous solution. Ammonia or substances that release ammonia upon introduction, such as urea or ammonium carbamate, are particularly preferred.

[0392] A particularly preferred process regime of the present invention is described in detail below.

[0393] DeNO X -deN2O- Variation 1 In a preferred embodiment, the off-gas treatment system comprises a first reaction zone and a second reaction zone, and the off-gas is passed through the first reaction zone and the second reaction zone in succession over the first reaction zone and the second reaction zone; a reducing agent is added to the off-gas upstream of the first reaction zone; In the first reaction zone, NO in the off-gas X The content is first, NO X NO by reducing agents via reduction catalysts X (step (e)) (de-NO X step (d1), the N2O content in the off-gas may be further reduced by decomposition of N2O via an N2O decomposition catalyst (step (d1)) and / or chemical reduction of N2O with a reducing agent via an N2O reduction catalyst (step (d2)); Additional reducing agent may be added to the off-gas upstream of the second reaction zone; and Then, in the second reaction zone, the N2O content in the off-gas is subsequently reduced by decomposition of N2O via an N2O decomposition catalyst (step (d1)) and / or chemical reduction of N2O with a reducing agent via an N2O reduction catalyst (step (d2)) (N2O removal stage), and the NO in the off-gas is X The content is NO X NO via reduction catalyst X may be further reduced by chemical reduction of (step (e)).

[0394] Preferably, the NO in the first reaction zone X The reduction catalyst comprises a conventional, preferably non-zeolitic SCR catalyst, for example based on V2O5-WO3- / TiO2.

[0395] Preferably, the temperature of the off-gas entering the first reaction zone is at most 400°C, preferably at most 350°C.

[0396] Preferably, the NO decomposition catalyst in the second reaction zone comprises a zeolitic material, preferably a zeolite comprising a transition metal (including lanthanides), in particular iron, cobalt or copper, more preferably an iron-containing zeolite, even more preferably an iron-containing zeolite of the MFI, BEA, FER, MOR, FAU and / or MEL structural type.

[0397] Preferably, the temperature of the off-gas entering the second reaction zone is in the range of from 300 to 550°C, preferably from 350 to 500°C.

[0398] Preferably, the off-gas after leaving the first reaction zone and before entering the second reaction zone has a NO concentration in the range of 0 to 200 ppmv, preferably 1 to 200 ppmv. X content and N2O content in the range of 200 to 2000 ppmv.

[0399] DeNO X -deN2O- Variation 2 In another preferred embodiment, the off-gas treatment system also comprises a first reaction zone and a second reaction zone, through which the off-gas is passed sequentially; a reducing agent is added to the off-gas upstream of the first reaction zone; In the first reaction zone, NO in the off-gas X The content is first, NO X NO by reducing agents via reduction catalysts X (step (e)) (de-NO X step (d1), the N2O content in the off-gas may be further reduced by decomposition of N2O via an N2O decomposition catalyst (step (d1)) and / or chemical reduction of N2O with a reducing agent via an N2O reduction catalyst (step (d2)); Additional reducing agent may be added to the off-gas upstream of the second reaction zone; and Then, in the second reaction zone, the N2O content in the off-gas is reduced by decomposition of N2O via an N2O decomposition catalyst (step (d1)) and / or chemical reduction of N2O with a reducing agent via an N2O reduction catalyst (step (d2)) (N2O removal stage), and the NO in the off-gas is X The content is NO X NO via reduction catalyst X may be further reduced by chemical reduction of (step (e)).

[0400] Preferably, the NO in the first reaction zone XThe reduction catalyst comprises a zeolitic material, preferably a zeolite comprising a transition metal (including lanthanides), in particular iron, cobalt or copper, more preferably an iron-containing zeolite, even more preferably an iron-containing zeolite of the MFI, BEA, FER, MOR, FAU and / or MEL structural type.

[0401] Preferably, the temperature of the off-gas entering the first reaction zone is at least 300° C., more preferably at least 350° C., even more preferably at least 400° C. Preferably, the temperature of the off-gas entering the first reaction zone is at most 600° C., more preferably at most 550° C.

[0402] Preferably, the N2O decomposition catalyst in the second reaction zone is a catalyst for decomposing N2O within the context of the present invention. X The catalyst comprises a sensitive N2O decomposition catalyst, which has already been described in detail above.

[0403] Preferably, the temperature of the off-gas entering the second reaction zone is at least 300° C., more preferably at least 350° C., even more preferably at least 400° C. Preferably, the temperature of the off-gas entering the second reaction zone is at most 600° C., more preferably at most 550° C.

[0404] Preferably, the off-gas after leaving the first reaction zone and before entering the second reaction zone contains at most 20 ppmv, more preferably at most 10 ppmv, and even more preferably at most 5 ppmv NO. X content, and N2O content in the range of 200 to 2000 ppmv.

[0405] Particularly preferred embodiments of deNO X -deN2O- Variation 2 In a particularly preferred embodiment, the off-gas treatment system of the present invention comprises a first catalyst bed and a spatially separated second catalyst bed, the first catalyst bed being arranged upstream of the second catalyst bed in the flow direction of the off-gas, a first device with a first control valve for metered addition of NH to the off-gas being arranged optionally and preferably upstream of the first catalyst bed, and a second device with a second control valve for metered addition of NH to the off-gas being arranged downstream of the first catalyst bed and upstream of the second catalyst bed, whereby further NH is metered into the off-gas, both the first catalyst bed and the second catalyst bed each comprising an iron-containing zeolite catalyst, and (i) in the first catalyst bed (d1), NO is decomposed, and (e) NO is decomposed. X is incompletely chemically reduced with NH3, at least a portion of which optionally and preferably results from the incomplete combustion of NH3 in step (a) (NH3 slip), and (ii) in a second catalyst bed (d2), residual N2O is chemically reduced with NH3, (d1*) residual N2O may be decomposed, and (e*) residual NO X is chemically reduced with NH3.

[0406] Preferably, the catalytic decomposition of NO in the first catalyst bed is carried out by decomposing NO present in the off-gas. X Co-catalyzed by

[0407] Preferably, NO with NH in the first catalyst bed X The incomplete chemical reduction of NO in the first catalyst bed results in a given residual NO sufficient to provide a co-catalytic effect on the decomposition of NO in the first catalyst bed. X The NO content is obtained by NH3 in the first catalyst bed. X The chemical reduction of NO typically proceeds much more rapidly than the chemical reduction of NO with NH, and the NO chemically reduced in the first catalyst bed X Since the amount of N2O in the first catalyst bed is not total, the extent of any concurrent chemical reduction of N2O by NH3 in the first catalyst bed is typically negligible.

[0408] Preferably, NO XAdditional NH3 for reduction is metered into the off-gas by the first device, preferably under feedback control, i.e., NO3 leaving the first catalyst bed. X A specific value of the concentration of NO is defined as the target value (setpoint), and the NO X The actual concentration of NO is measured (actual value), and if there is a difference between the setpoint and the actual value (control difference), the output of the first control valve is changed to minimize the difference. Preferably, the NO leaving the first catalyst bed X The setpoint concentration of NO, and therefore the amount of additional NH3, is determined by the NO leaving the first catalyst bed. X Preferably, the NO 2 concentration leaving the first catalyst bed is selected to be at most 1000 ppmv, preferably at most 500 ppmv, more preferably at most 100 ppmv. X The setpoint concentration of NO, and therefore the amount of additional NH3, is determined by the NO leaving the first catalyst bed. X The residual concentration of NO in the first catalyst bed is selected to be at least 10 ppmv, preferably at least 20 ppmv, and more preferably at least 40 ppmv. X The expected specific consumption of NH for the chemical reduction of reduced NO is typically X is in the range of 0.9 to 1.1 moles of NH3 per mole and is therefore significantly less than the expected specific consumption of NH3 (mol / mol) in the second catalyst bed.

[0409] Preferably, the temperature of the off-gas leaving the first catalyst bed is in the range of 400 to 550°C.

[0410] Preferably, the off-gas leaving the first catalyst bed is at a pressure above atmospheric pressure, ie ≧1.0 bara, but up to 1.2 bara, more preferably up to 1.1 bara.

[0411] Preferably, the off-gas leaving the first catalyst bed contains at least 5.0%, preferably at least 7.5%, more preferably at least 10%, even more preferably at least 12.5%, most preferably at least 15%, especially at least 17.5% NO Xhas an oxidation degree of

[0412] In a preferred embodiment, the off-gas exiting the first catalyst bed contains NO in the range of 30% to 50%. X has an oxidation degree of

[0413] In another preferred embodiment, the off-gas leaving the first catalyst bed contains NO in the range of 15% to 35%, preferably 15% to 30%. X has an oxidation degree of

[0414] In a more preferred embodiment, the off-gas from the first catalyst bed contains NO in the range of 10% to 20%. X has an oxidation degree of

[0415] In another preferred embodiment, the off-gas exiting the first catalyst bed contains NO in the range of 5% to 15%. X has an oxidation degree of

[0416] Preferably, the residual N2O is decomposed in the second catalyst bed to a residual concentration of N2O exiting the second catalyst bed of at most 20 ppmv, more preferably at most 10 ppmv, even more preferably at most 5 ppmv, and most preferably at most 2 ppmv.

[0417] Preferably, residual NO X is a NO 2 leaving the second catalyst bed of at most 20 ppmv, more preferably at most 10 ppmv, even more preferably at most 5 ppmv, and most preferably at most 2 ppmv. X The toluene is decomposed in the second catalyst bed to a residual concentration of 0.1%.

[0418] Preferably, the additional NH3 is metered by a second device under feedforward control, i.e., NO X and optionally preferably the concentration of N2O is measured in each case upon exiting the first catalyst bed or, optionally, upon entering the second catalyst bed, and the amount of off-gas entering the second catalyst bed is determined by the stored ratio, i.e., for example, NH3 / NO Xand optionally preferably using the molar ratio of NH3 / N2O (mol / mol) or the coefficient resulting therefrom, NO X The amount of NH3 required for reduction, and optionally preferably NO X The total amount of NH3 required for reduction and N2O reduction is taken into account, and the calculated result (manipulated variable) is used to change the output of the second control valve to meter the required amount of NH3.

[0419] Preferably, according to the invention, the molar NH3 concentration [NH3] of the off-gas entering the second catalyst bed is 0.7x[N2O] and 1.0x[NO X ] from the sum of 4.0x[N2O] and 2.0x[NO X ], more preferably in the range of 1.0x[NO] and 1.1x[NO X ] from the sum of 3.0x[N2O] and 1.6x[NO X ], and even more preferably in the range of 1.5x[NO] and 1.2x[NO X ] to the sum of 2.5x[N2O] and 1.4x[NO X ], where [NO] is the molar concentration of NO and [NO X ] is the respective NO in the off-gas entering the second catalyst bed X is the molar concentration of

[0420] Preferably, NO X For feed-forward control of the metered addition of NH3 to the second catalyst bed for reduction, a NH3 / NO ratio in the range of 1.0 to 2.0, preferably 1.1 to 1.6, more preferably 1.2 to 1.4 is used. X The molar ratio is selected as follows:

[0421] Preferably, for feed-forward control of the metered addition of NH3 to the second catalyst bed for N2O reduction, a molar ratio of NH3 / N2O in the range of 0.7 to 4.0, preferably 1.0 to 3.0, more preferably 1.5 to 2.5 is selected.

[0422] Preferably, the additional NH3 is used to replace NO in the second catalyst bed.X This would limit the usefulness of the results as a control variable, since NO is the largest chemical reduction of NO. X and that there is only zero or very small residual concentration of N2O, which is not metered by a second device under feedback control.

[0423] Preferably, the amount of catalyst, i.e., the space velocity (= ratio of off-gas volumetric flow rate to catalyst volume under standard conditions), is selected so that the decomposition of NO in the first catalyst bed is at least 50%, preferably at least 70%, more preferably at least 80%, based on the concentration of NO entering the first catalyst bed.

[0424] Preferably, the amount of catalyst and the amount of additional NH3 are such that NO X / N2O molar ratio is selected to be at least 5, more preferably at least 10, even more preferably at least 20.

[0425] The space velocity of the first catalyst bed is preferably 5000 h -1 ~100000h -1 , more preferably 10,000h -1 ~50,000h -1 , and even more preferably 15,000h -1 ~45000h -1 The range is.

[0426] NO leaving the first catalyst bed X When the molar ratio of NH3 / N2O is at least 10, the metered addition of NH3 to the second catalyst bed via the second device X Preferably, this can be done only with respect to the amount of

[0427] Preferably, the temperature of the off-gas entering the first catalyst bed is at least 400° C., more preferably at least 425° C., even more preferably at least 450° C. Preferably, the temperature of the off-gas entering the first catalyst bed is at most 550° C., more preferably at most 525° C., even more preferably at most 500° C. The temperature can be adjusted by means known to those skilled in the art, in particular the design of the heat exchanger and the combustion conditions of NH3.

[0428] Depending on the exothermicity of the chemical reactions taking place in the first and second catalyst beds, the inlet temperature of the off-gas to the first catalyst bed is preferably selected so that the temperature of the off-gas leaving the second catalyst bed is at most 600°C, more preferably at most 550°C, even more preferably at most 520°C.

[0429] The space velocity of the second catalyst bed is preferably 5000 h -1 ~100000h -1 , more preferably 10,000h -1 ~50,000h -1 , and even more preferably 15 000h -1 ~45000h -1 The range is.

[0430] Preferably, the catalyst volume V1 of the first catalyst bed cat Catalyst volume V2 of the second catalyst bed cat catalyst volume ratio (V1 cat / V2 cat ) is in the range of 1 / 2 to 20 / 1, preferably 1 / 2 to 10 / 1, and more preferably 1 / 1 to 4 / 1.

[0431] In a preferred embodiment, the following conditions are met: the pressure of the off-gas entering the first catalyst bed is at most 5 bara, preferably at most 4 bara, more preferably at most 1.3 bara, most preferably at most 1.2 bara, in particular at most 1.1 bara; the HO content in the off-gas entering the first catalyst bed is at least 5% by volume, preferably at least 10% by volume, more preferably at least 15% by volume, most preferably at least 20% by volume, in particular at least 25% by volume; NO in the off-gas entering the first catalyst bed X the content is at least 500 ppmv, more preferably at least 1000 ppmv, even more preferably at least 1500 ppmv, most preferably at least 2000 ppmv, in particular at least 2500 ppmv; the N2O content in the off-gas entering the first catalyst bed is less than maximum 500 ppmv, more preferably maximum 200 ppmv, even more preferably maximum 100 ppmv, but is at least 5 ppmv, preferably at least 10 ppmv, more preferably at least 50 ppmv; The off-gas entering the first catalyst bed contains unburned residues of NH3 from the combustion of NH3; The N2O decomposition catalyst and / or the N2O reduction catalyst are in the form of a honeycomb body; NO X The reduction catalyst takes the form of a honeycomb body; The first catalyst bed contains Fe zeolite; The second catalyst bed contains Fe zeolite; The off-gas passes through a heat exchanger in which it is heated before entering the first catalyst bed; NO on exit from the first catalyst bed X the content is at most 1000 ppmv, preferably at most 500 ppmv, more preferably at most 300 ppmv, most preferably at most 100 ppmv, but preferably at least 10 ppmv, more preferably at least 20 ppmv, more preferably at least 40 ppmv, most preferably at least 100 ppmv, in particular at least 250 ppmv; the N2O content leaving the first catalyst bed is at most 20 ppmv, more preferably at most 15 ppmv, even more preferably at most 10 ppmv, most preferably at most 5 ppmv, in particular at most 2 ppmv; · There is no intermediate cooling of the off-gas between leaving the first catalyst bed and entering the second catalyst bed; N2O:NO upon entering the first catalyst bed X is at most 0.5, more preferably at most 0.2, even more preferably at most 0.1; N2O:NO leaving the first catalyst bed X is at most 0.20, more preferably at most 0.1, even more preferably at most 0.05; The supply of NH3 to the off-gas upstream of the first catalyst bed in the flow direction of the off-gas is optional, and if there is a supply, it is preferably to reduce the NO2 content as it enters the first catalyst bed. X Substoichiometric to content; The supply of NH3 to the off-gas downstream of the first catalyst bed and upstream of the second catalyst bed in the flow direction of the off-gas reduces the NO entering the second catalyst bed. X and N2O content is essential and preferably superstoichiometric with respect to the total content, At least one, two or more, or all of the following are satisfied.

[0432] The above method, which uses Fe zeolite catalyst in two catalyst beds, is different from the conventional deNOx method, which uses V2O5 / TiO2 catalyst. X Compared to the law, -Large amounts of NO without the risk of NH3 slip X and - Allows simultaneous complete or substantially complete decomposition of N2O at a relatively low catalyst volume, i.e., at a relatively high space velocity.

[0433] Apart from the operating method of the present invention, this is achieved by the oxidation properties of the Fe zeolite catalyst used according to the present invention. Therefore, in the first catalyst bed, the molar ratio of NO to NO2 is brought as close as possible to the thermodynamic equilibrium position according to the present invention. For example, before entering the first catalyst bed, the NO XThe degree of oxidation (molar ratio of NO2 / (NO+NO2)) of NO2 is less than 5%, as expected, due to the combustion of upstream NH3 at very high temperatures and only slow establishment of equilibrium in the gas phase as the off-gas is cooled in any downstream heat exchanger(s), and is therefore far below the thermodynamic equilibrium applicable to the inlet temperature to the first catalyst bed. However, this results in a significant increase in the NO2 present in the off-gas. X Only a small portion of the NO can be decomposed by fast SCR. X or NO because most of the remaining NO must be destroyed by conventional SCR, which is significantly slower. X This is highly unfavorable for the efficient chemical reduction of

[0434] The selected operating mode of limited metering of NH3 in the first catalyst bed and the ability of the Fe zeolite catalyst to oxidize NO or catalytically accelerate the establishment of equilibrium results in a significantly faster, i.e., more efficient NO X At the same time, residual NO is excreted. X NO in X This results in the establishment of the maximum possible degree of oxidation of NO in the second catalyst bed from the very beginning. X can be chemically reduced.

[0435] Therefore, similar to water, high concentrations of NO X The large amount of NH3 required for the complete chemical reduction of NO over an Fe zeolite catalyst X It was found to inhibit the establishment of equilibrium.

[0436] Furthermore, NO X The chemical reduction of NO is similarly inhibited by NH itself at correspondingly high doses of NH. As a result, the temperature, amount of catalyst, and NO X Depending on the content, adding NH3 above and below a certain amount of NH3 will not produce NO X Further increase in decomposition does not occur. If NH3 addition is further increased, under some circumstances, NO XA decrease in the degradation of α-tocopherol may even be observed.

[0437] First, NO in the first catalyst bed X The chemical reduction of NO in the second catalyst bed X This significantly reduces the amount of NH3 required for the chemical reduction of

[0438] In this way, NO X With the above-mentioned establishment or permanent readjustment of the equilibrium, even the superstoichiometric metering of NH3 according to the present invention does not result in NO in the second catalyst bed. X A highly efficient chemical reduction of

[0439] The fact that this is further achieved according to the invention with zero or little NH3 slip, preferably at most 10 ppmv, more preferably at most 5 ppmv, even more preferably at most 3 ppmv, is due to the oxidizing properties of the Fe-zeolite catalyst used according to the invention. If the inlet temperature of the off-gas to the second catalyst bed is preferably at least 400°C, more preferably at least 425°C, even more preferably at least 450°C, then NH3 metered in excess within the scope of the invention will be selectively oxidized to N2 and HO by the residual oxygen content of the off-gas present.

[0440] All of these benefits cannot be achieved in single or multi-stage configurations when using conventional V2O5 / TiO2-based SCR catalysts, which are also typically used to detoxify offgas from natural gas-fired reformers. Therefore, for stability reasons, these conventional SCR catalysts typically cannot operate at temperatures above 400°C, which limits the achievable rate of the decomposition reaction. Also, conventional SCR catalysts have very limited oxidation activity, resulting in a low NO X The establishment or permanent readjustment of the equilibrium is not possible, and these catalysts do not allow an efficient and N2-selective oxidation of overdosed NH3, instead there is even a risk of the undesired formation of N2O.

[0441] In a variant of the above-described embodiment that is preferred according to the present invention, the first catalyst bed and the second catalyst bed contain the same catalyst. In a preferred embodiment, the second device with a second control valve for metering NH3 into the off-gas is omitted, but it is preferred to omit the spatial separation of the first catalyst bed from the second catalyst bed, in which case there is actually only a single shared catalyst bed, and the first device with a first control valve for metering NH3 into the off-gas is preferably located upstream of this shared catalyst bed. Additional NH3 is preferably metered into the off-gas via the first device, preferably under feed-forward control, i.e., by controlling the NO in the off-gas upstream of the shared catalyst bed. X The concentrations of NO and NH are measured, the amount of off-gas entering the shared catalyst bed is taken into account to calculate the additional amount of NH still required, and the calculated result (manipulated variable) is used to change the output of the first control valve to meter the amount of additional NH still required. Preferably, in such an embodiment, an NH oxidation catalyst is placed downstream of the shared catalyst bed to reduce possible NH slip.

[0442] Co-firing of NH3 and CH4 - reducing hydrogen cyanide content In a preferred embodiment, in step (a), a mixture of CH4 and NH3 with air and / or oxygen is combusted to produce CO2, CO and HCN, and NO X and produces an off-gas that further contains N2O.

[0443] In these cases, the first catalyst bed preferably performs the additional function of catalytic cracking of HCN by hydrolysis with water present in the off-gas to give CO and NH3 products as follows: HCN + HO ⇔ CO + NH3. The CO and NH3 products formed are then preferably converted into NO in the first catalyst bed, as for NH3. X For reduction, and with respect to CO, preferably for N2O reduction in the second catalyst bed, N2O and NO in the off-gas X It can be used as a reducing agent for the removal of

[0444] The content of HCN in the off-gas as a pollutant and greenhouse gas must be limited or eliminated due to its toxicity and longevity in the atmosphere and its absorption in infrared light. When HCN is decomposed in accordance with the present invention over a zeolite catalyst in the first catalyst bed containing CO and NH3, NO in the second catalyst bed is decomposed. X The fact that cracking products are formed that are suitable as reducing agents for further off-gas post-treatment of NO and NO completes the uniqueness of the inventive off-gas treatment on a zeolite catalyst. Conventional SCR catalysts based on vanadium oxide are virtually inactive for HCN hydrolysis and are therefore not suitable for HCN removal from off-gas. In this case, a downstream oxidation catalyst must be used.

[0445] DeN2O-deNO X. In a further preferred embodiment, the off-gas treatment system comprises a first reaction zone and a second reaction zone, and the off-gas passes through the first reaction zone and the second reaction zone in succession over the first reaction zone and the second reaction zone; a reducing agent is added to the off-gas between the first reaction zone and the second reaction zone; In the first reaction zone, the N2O content in the off-gas is first reduced by decomposition of N2O (deN2O stage) over an N2O decomposition catalyst (step (d1)), and Then, in the second reaction zone, NO in the off-gas X The content is NO X NO by reducing agents via reduction catalysts X (step (e)) (de-NO X After the decomposition of N2O via an N2O decomposition catalyst (step (d1)), the N2O content in the off-gas is optionally further reduced by further decomposition of N2O via an N2O decomposition catalyst (step (d1)) and / or chemical reduction of N2O with a reducing agent via an N2O reduction catalyst (step (d2)).

[0446] Preferably, no reducing agent is added to the off-gas upstream of the first reaction zone.

[0447] Such a process regime is particularly preferred according to the present invention, as it allows firstly to produce NO without consuming a reducing agent. X This allows for the adjustment of the relative content of NO and NO in the first reaction zone. X The NO content in the off-gas is selectively reduced by decomposition, while the NO content remains substantially unchanged. X and to the extent necessary to establish the desired relative content of N2O. For economic reasons, it is preferred that the selected amount of N2O decomposition catalyst is not so large as to achieve a quantitatively complete reduction (0 ppmv) of the N2O content in the off-gas by decomposition; instead, a compromise is found between the rate of decomposition and the size of the N2O decomposition catalyst.

[0448] In a preferred embodiment, the NO decomposition catalyst in the first reaction zone comprises a zeolitic material, preferably a zeolite comprising a transition metal (including lanthanides), in particular iron, cobalt or copper, more preferably an iron-containing zeolite, even more preferably an iron-containing zeolite of the MFI, BEA, FER, MOR, FAU and / or MEL structural type.

[0449] In another preferred embodiment, the NO decomposition catalyst in the first reaction zone is a NO decomposition catalyst within the context of the present invention already described above. X Contains a sensitive N2O decomposition catalyst.

[0450] In a preferred embodiment, NO in the second reaction zone X The reduction catalyst comprises a zeolitic material, preferably a zeolite comprising a transition metal (including lanthanides), in particular iron, cobalt or copper, more preferably an iron-containing zeolite, even more preferably an iron-containing zeolite of the MFI, BEA, FER, MOR, FAU and / or MEL structural type.

[0451] Preferably, the first reaction zone and the second reaction zone are operated at different temperature levels here.

[0452] Preferably, The NO decomposition catalyst in the first reaction zone X the off-gas temperature of the first reaction zone is preferably at least 450°C, more preferably at least 500°C, even more preferably at least 550°C, and most preferably at least 600°C; and -NO in the second reaction zone X The reduction catalyst is a zeolite material, preferably a zeolite containing a transition metal (including lanthanides), in particular iron, cobalt or copper, more preferably an iron-containing zeolite, even more preferably an iron-containing zeolite of MFI, BEA, FER, MOR, FAU and / or MEL structural type, the off-gas temperature of the second reaction zone is preferably 550°C or less, more preferably 500°C or less, even more preferably 450°C or less, most preferably 400°C or less, and NO X In addition to the chemical reduction of N2O, the (residual) N2O content is preferably further reduced in a second reaction zone by decomposition and / or chemical reduction.

[0453] Preferably, in the first reaction zone, the space velocity is set so that the N2O content in the off-gas is reduced in the first reaction zone by at most 95%, preferably at most 90%, preferably at most 85%, based on the N2O content in the off-gas entering the first reaction zone.

[0454] In a preferred embodiment, the NO content in the off-gas after leaving the first reaction zone and before entering the second reaction zone is at least 20 ppmv, more preferably at least 40 ppmv, even more preferably at least 60 ppmv, most preferably at least 80 ppmv, especially at least 100 ppmv.

[0455] In a preferred embodiment, the NO content in the off-gas after leaving the first reaction zone and before entering the second reaction zone is at most 400 ppmv, more preferably at most 300 ppmv, even more preferably at most 200 ppmv, most preferably at most 100 ppmv, especially at most 50 ppmv.

[0456] Preferably, in the second reaction zone, the space velocity is set so that the N2O content in the off-gas is further reduced in the second reaction zone by at least 30%, preferably at least 40%, more preferably at least 50%, based on the N2O content in the off-gas entering the second reaction zone. Because a reducing agent is present in the second reaction zone, further reduction of the N2O content in the second reaction zone can be achieved both by decomposition with an N2O decomposition catalyst (step (d1)) and by chemical reduction with a reducing agent via an N2O reduction catalyst (step (d2)).

[0457] Preferably, in the second reaction zone, the N2O content in the off-gas is further reduced by chemical reduction of N2O with a reducing agent via an N2O reduction catalyst (step (d2)).

[0458] In the second reaction zone, NO X NO is chemically reduced by a reducing agent via a reduction catalyst. X This reduction typically has fast kinetics and preferably proceeds substantially quantitatively in accordance with the present invention.

[0459] Step (f): In an optional preferred step (f) of the method of the present invention, the off-gas is cooled in at least one heat exchanger arranged downstream of the off-gas treatment system in the flow direction of the off-gas.

[0460] In a preferred embodiment, the off-gas is cooled in a single heat exchanger located downstream of the off-gas treatment system in the flow direction of the off-gas.

[0461] In another preferred embodiment, the off-gas is cooled successively in at least two heat exchangers arranged downstream of the off-gas treatment system in the flow direction of the off-gas (see Figures 2, 3 and 4).

[0462] In a further preferred embodiment, the off-gas is cooled successively in at least three heat exchangers arranged downstream of the off-gas treatment system in the off-gas flow direction (see FIG. 5).

[0463] In another preferred embodiment, the off-gas is cooled successively in at least four heat exchangers arranged downstream of the off-gas treatment system in the flow direction of the off-gas.

[0464] In a further preferred embodiment, the off-gas is cooled successively in at least five heat exchangers arranged downstream of the off-gas treatment system in the off-gas flow direction (see FIG. 6).

[0465] The off-gas is cooled in at least one heat exchanger by the release of heat from the off-gas to a heat transfer medium.

[0466] Preferably, according to the present invention, the heat transfer medium used is selected from the group consisting of water, steam, combustion air, NH3 and combinations thereof. Notably for safety reasons, water or steam is particularly preferred as heat transfer medium.

[0467] In a preferred embodiment, in step (f) of the method of the present invention, the off-gas is cooled in a first off-gas / H2O heat exchanger arranged downstream of the off-gas treatment system in the flow direction of the off-gas. H2O is heated in the first off-gas / H2O heat exchanger by absorbing heat from the off-gas. Preferably, the heated H2O, which may be in liquid form and / or in the form of steam, is used to heat NH3. Preferably, for this purpose, a H2O / NH3 heat exchanger is arranged downstream of the first off-gas / H2O heat exchanger in the flow direction of the H2O, and NH3 is heated by absorbing heat from H2O (see Figures 2 to 6).

[0468] In a preferred embodiment, in step (f) of the method of the present invention, the off-gas is cooled in a first off-gas / combustion air heat exchanger arranged downstream of the off-gas treatment system in the flow direction of the off-gas. The combustion air is heated in the first off-gas / combustion air heat exchanger by absorbing heat from the off-gas. Preferably, the heated combustion air is used for the combustion of NH3 and H2 in a combustion device, which for this purpose is arranged downstream of the first off-gas / combustion air heat exchanger in the flow direction of the combustion air (see Figures 2 to 6).

[0469] In another preferred embodiment, the off-gas is in said first off-gas / H2O heat exchanger arranged downstream of the off-gas treatment system in the flow direction of the off-gas, in said first offgas / combustion air heat exchanger, which is arranged downstream of the offgas treatment system in the flow direction of the offgas, preferably downstream of the first offgas / H2O heat exchanger (see Figures 2 to 6), In step (f) of the method of the present invention, cooling is performed.

[0470] In a further preferred embodiment, the off-gas is in a first offgas / combustion air heat exchanger arranged downstream of the offgas treatment system in the flow direction of the offgas, in a second off-gas / combustion air heat exchanger arranged downstream of the first off-gas / combustion air heat exchanger in the flow direction of the off-gas, In step (f) of the method of the present invention, cooling is performed.

[0471] The combustion air is heated in the first and second off-gas / combustion air heat exchangers by absorbing heat from the off-gas in each case. Preferably, the off-gas flows first through the first off-gas / combustion air heat exchanger and then through the second off-gas / combustion air heat exchanger. Preferably, the combustion air flows first through the second off-gas / combustion air heat exchanger and then through the first off-gas / combustion air heat exchanger, which is why the first off-gas / combustion air heat exchanger is preferably arranged downstream of the second off-gas / combustion air heat exchanger in the flow direction of the combustion gas. Preferably, the heated combustion air is used for the combustion of NH3 and H2 in a combustion device, which for this purpose is arranged downstream of the first off-gas / combustion air heat exchanger in the flow direction of the combustion air (see Figures 5 and 6).

[0472] In another preferred embodiment, the off-gas is in said first off-gas / combustion air heat exchanger, which is arranged downstream of the off-gas treatment system in the flow direction of the off-gas, in a first off-gas / H2O heat exchanger arranged downstream of the first off-gas / combustion air heat exchanger in the flow direction of the off-gas, in the aforementioned second off-gas / combustion air heat exchanger arranged downstream of the first off-gas / H2O heat exchanger in the flow direction of the off-gas (see Figures 4 to 6).

[0473] In step (f) of the method of the present invention, cooling is performed.

[0474] The off-gas then preferably flows first through a first off-gas / combustion air heat exchanger, then through a first off-gas / H2O heat exchanger, and subsequently through a second off-gas / combustion air heat exchanger.

[0475] In a preferred embodiment, in step (f) of the method of the present invention, the off-gas is cooled in at least one off-gas / combustion gas heat exchanger arranged downstream of the off-gas treatment system in the flow direction of the off-gas, preferably downstream of the first off-gas / combustion air heat exchanger, the first off-gas / H2O heat exchanger, and / or the second off-gas / combustion air heat exchanger. The combustion gas is heated in the off-gas / combustion gas heat exchanger by absorbing heat from the off-gas. Preferably, the heated combustion gas is used for combustion in a combustion device, which for this purpose is arranged downstream of the off-gas / combustion gas heat exchanger in the flow direction of the combustion gas (see Figure 6).

[0476] In a preferred embodiment, in step (f) of the inventive method, the off-gas is cooled in at least one second off-gas / H2O heat exchanger located downstream of the off-gas treatment system in the flow direction of the off-gas, preferably downstream of the first off-gas / combustion air heat exchanger, the first off-gas / H2O heat exchanger, and / or the second off-gas / combustion air heat exchanger. The H2O is heated in the second off-gas / H2O heat exchanger (see Figure 6) by absorbing heat from the off-gas.

[0477] In another preferred embodiment, the off-gas is in said first off-gas / combustion air heat exchanger, which is arranged downstream of the off-gas treatment system in the flow direction of the off-gas, in a first off-gas / H2O heat exchanger arranged downstream of the first off-gas / combustion air heat exchanger in the flow direction of the off-gas, in a second off-gas / combustion air heat exchanger arranged downstream of the first off-gas / H2O heat exchanger in the flow direction of the off-gas, in the aforementioned off-gas / combustion air heat exchanger, which is arranged downstream of the second off-gas / combustion air heat exchanger in the flow direction of the off-gas (see FIG. 6 ), In step (f) of the method of the present invention, cooling is performed.

[0478] In a further preferred embodiment, the off-gas is in said first off-gas / combustion air heat exchanger, which is arranged downstream of the off-gas treatment system in the flow direction of the off-gas, in a first off-gas / H2O heat exchanger arranged downstream of the first off-gas / combustion air heat exchanger in the flow direction of the off-gas, in a second off-gas / combustion air heat exchanger arranged downstream of the first off-gas / H2O heat exchanger in the flow direction of the off-gas, in said second off-gas / H2O heat exchanger arranged downstream of the second off-gas / combustion air heat exchanger in the flow direction of the off-gas (see FIG. 6 ), In step (f) of the method of the present invention, cooling is performed.

[0479] In another preferred embodiment, the off-gas is in said first off-gas / combustion air heat exchanger, which is arranged downstream of the off-gas treatment system in the flow direction of the off-gas, in a first off-gas / H2O heat exchanger arranged downstream of the first off-gas / combustion air heat exchanger in the flow direction of the off-gas, in a second off-gas / combustion air heat exchanger arranged downstream of the first off-gas / H2O heat exchanger in the flow direction of the off-gas, in the aforementioned off-gas / combustion gas heat exchanger, which is arranged downstream of the second off-gas / combustion air heat exchanger in the flow direction of the off-gas, in said second off-gas / H2O heat exchanger arranged downstream of the off-gas / combustion gas heat exchanger in the flow direction of the off-gas (see FIG. 6 ), In step (f) of the method of the present invention, cooling is performed.

[0480] High off-gas temperatures can cause significant stress on the materials used, resulting in high wall temperatures at least in the upstream heat exchangers in the off-gas duct in the direction of off-gas flow, potentially shortening their service life or replacing them with more complex and expensive materials. Therefore, one factor in considering the effectiveness of the off-gas duct configuration is the inlet temperature of the off-gas to the duct. NH3 must be preheated to a temperature dictated by the process requirements. On the other hand, the preheat temperature of, for example, combustion air constitutes a degree of design freedom, since it is not subject to any direct requirements other than efficient energy integration. Therefore, the inlet temperature of the off-gas to the off-gas duct is limited at the lower end by the preheat temperature imposed by the process requirements in a tubular reactor of similar design to the primary reformer or possible pre-reactor (preferably an adiabatic fixed-bed reactor).

[0481] Heterogeneous catalysts achieve higher reaction rates at higher temperatures due to accelerated diffusion and reaction rates. However, their operation is often limited by their resistance to deactivation at high temperatures. Therefore, an off-gas treatment system has an optimal operating window in which it achieves high reaction rates, which manifests itself in a high allowable space velocity of the supplied gas, which reduces the required catalyst volume. However, this window lies below the region where operation results in deactivation and loss of catalyst effectiveness. Therefore, a further criterion for evaluating efficient energy integration is whether the inlet temperature of the off-gas to the off-gas treatment system is within this optimal window.

[0482] The third factor in assessing the effectiveness of an off-gas duct configuration is the inlet temperature of the off-gas to the chimney. Together with the mass flow rate of the off-gas, this determines the energy loss through the flow compared to the theoretical optimum achieved with a required safety margin of 25K above the water dew point.

[0483] The H2 yield must be as high as possible to increase the economic viability of plant operation. A high yield is typically directly related to a low inlet temperature of the off-gas to the stack. However, if this objective cannot be achieved without minimizing the required inlet temperature of the off-gas to the stack or providing an inlet temperature suitable for the off-gas treatment system, the selected design of the off-gas duct will be less successful.

[0484] Closed-Loop Control Regardless of the respective process regime, the method of the present invention is preferably under closed-loop control.

[0485] In a preferred embodiment, depending on the configuration of the calcination system, preferably the combustion device, for the closed-loop control of the method of the present invention, the first measured variable is at least one parameter characteristic of the current operating state of the calcination system, preferably the combustion device. Preferably, this first measured variable or parameter is selected from the group consisting of the combustion temperature and the NH3 consumption of the calcination system, preferably the combustion device.

[0486] NO in off-gas X To achieve an efficient and economically viable reduction of the NO content, the characteristics of the off-gas leaving the firing system, preferably the combustion device, in particular: -NO in off-gas X Content; -NO in off-gas X degree of oxidation; - N2O content in off-gas; the content of other components in the off-gas, such as H2O, O2, and N2; - Off-gas temperature; -offgas pressure; and - Off-gas volume flow rate; The process conditions can be optimized accordingly.

[0487] Thus, in a preferred embodiment, for the control of the method of the present invention, at least one parameter characteristic of the current state of the off-gas before it enters the off-gas treatment system is measured on exit from the firing system, preferably a combustion device, and / or on entry into the off-gas treatment system as a second measurement variable in addition to or instead of the first measurement variable. Preferably, this second measurement variable or parameter is the NO 2 in the off-gas. X Content, NO in off-gas X the degree of oxidation of the off-gas; the N2O content in the off-gas; the content of other components in the off-gas, such as H2O, O2, and N2; the off-gas temperature; the off-gas pressure; and the volumetric flow rate of the off-gas.

[0488] Thus, in a preferred embodiment, in order to control the method of the present invention, at least one parameter characteristic of the current state of the off-gas exiting the off-gas treatment system is measured as it leaves the off-gas treatment system as a third measurement variable in addition to or instead of the first measurement variable, and in addition to or instead of the second measurement variable. Preferably, this third measurement variable or parameter is NO 2 in the off-gas. X Content, NO in off-gas X the degree of oxidation of the off-gas; the N2O content in the off-gas; the content of other components in the off-gas, such as H2O, O2, and N2; the off-gas temperature; the off-gas pressure; and the volumetric flow rate of the off-gas.

[0489] In a preferred embodiment, particularly when the off-gas treatment system comprises a first reaction zone and a second reaction zone through which the off-gas passes successively and a reducing agent is supplied between the first and second reaction zones, for the control of the method of the invention, at least one parameter characteristic of the current state of the off-gas after it leaves the first reaction zone and before it enters the second reaction zone is measured as a fourth measurement variable starting from the first reaction zone and before it enters the second reaction zone in addition to or instead of the first measurement variable, in addition to or instead of the second measurement variable, and in addition to or instead of the third measurement variable. Preferably, this fourth measurement variable or parameter is NO in the off-gas. X Content, NO in off-gas X the degree of oxidation of the off-gas; the N2O content in the off-gas; the content of other components in the off-gas, such as H2O, O2, and N2; the off-gas temperature; the off-gas pressure; and the volumetric flow rate of the off-gas.

[0490] Depending on the first and / or second and / or third and / or fourth measured variable, at least one manipulated variable is preferably modified for open-loop or closed-loop control of the method according to the invention. Preferably, the open-loop or closed-loop control of the method is therefore based on the first and / or second and / or third and / or fourth measured variable by controlled changes of the manipulated variables (control variables), preferably by controlled changes of the amount of reducing agent metered.

[0491] Regarding the preferred instrumental variables, - process conditions that can be changed quickly, if at all, only with a relatively high level of equipment complexity; process conditions that can be changed at short notice and are therefore more suitable for controlling the process; A distinction needs to be made between

[0492] Preferably, according to the present invention, - Dimensions of the off-gas treatment equipment; the nature, amount and flow direction of the N2O decomposition catalyst and / or N2O reduction catalyst; NO X the nature, amount and flow direction of the reduction catalyst; Type of reducing agent; - Off-gas pressure; the location of the reducing agent supply; and The relative locations of the first and second reaction zones are not manipulated variables, ie, these parameters preferably remain constant during the practice of the process of the present invention.

[0493] However, these parameters can be selected or adjusted in the planning and design of the off-gas treatment system so that the control of the method of the present invention is possible within wide limits. In this way, it is also possible to react to changes in the off-gas being treated, for example, in the short term. X and an efficient and economically viable reduction of the content of N2O remains guaranteed without undesired breakthrough of the reducing agent (called slip).

[0494] The preferred manipulated variables (control variables) according to the present invention are as follows:

[0495] - amount of reducing agent; - Off-gas temperature, if appropriate; and - Catalyst temperature, if appropriate.

[0496] Preferably, the off-gas leaving the off-gas treatment system has a residual NO of at most 20 ppmv, preferably at most 15 ppmv, more preferably at most 10 ppmv, even more preferably at most 7.5 ppmv, most preferably at most 5.0 ppmv, especially at most 2.5 ppmv. X It has a content.

[0497] Preferably, the off-gas leaving the off-gas treatment system has a residual N2O content of at most 20 ppmv, preferably at most 15 ppmv, more preferably at most 10 ppmv, even more preferably at most 7.5 ppmv, most preferably at most 5.0 ppmv, especially at most 2.5 ppmv.

[0498] A further aspect of the present invention is (i) an NH3 calcination system preferably comprising a combustion device for combusting NH3 and an NH3 decomposition device for cracking NH3 into N2 and H2; (ii) Off-gas treatment systems; In a device comprising: The device is configured to carry out the aforementioned method of the present invention.

[0499] The device of the present invention preferably comprises: - one or more NH3 decomposition devices, preferably catalyst-filled reactors, for catalytic decomposition of NH3 into N2 and H2; - a combustion device for directly or indirectly heating the NH3 decomposition device(s), preferably comprising a combustion chamber and at least one burner for burning a fuel with (air) oxygen, the fuel containing NH3 or consisting essentially of NH3; - a device for purifying the product stream from the NH3 decomposition device, preferably by PSA; - an off-gas treatment system for cleaning off-gases from a combustion device, optionally for NO reduction and / or NO decomposition, and preferably for oxidation of unconverted reducing agents and / or their incompletely oxidized reaction products, X an off-gas treatment system comprising one or more catalyst beds (preferably a downstream catalyst bed having an NH3 oxidation catalyst) for reducing 1. An industrial plant complex for producing pure hydrogen comprising:

[0500] A preferred embodiment of the present invention is summarized as a sentence below.

[0501] Satz1: NO in the offgas of NH3-operated firing systems X1. A method for reducing the content of NH3 and N2O, the process comprising: (a) operating a calcination system, preferably comprising a combustion device and an NH3 decomposition device, to combust NH3 to catalytically decompose the NH3 into N2 and H2, and X and N2O and exiting the calcination system; (b) optionally and preferably cooling the off-gas in at least one heat exchanger located downstream of the calcination system in a flow direction of the off-gas; (c) optionally transporting the cooled off-gas to an off-gas treatment system; (d) reducing the N2O content in the off-gas by (d1) decomposing N2O via an N2O decomposition catalyst and / or (d2) chemically reducing N2O with a reducing agent via an N2O reduction catalyst; and (e) treating the off-gas with N2O. X NO by reducing agents over reduction catalysts X NO in the off-gas by chemical reduction of X and (f) optionally and preferably cooling the off-gas in at least one heat exchanger located downstream of the off-gas treatment system in the flow direction of the off-gas.

[0502] Satz2: NO in the off-gas of an NH3- and H2-operated calcination system incorporated into a system for catalytic decomposition of NH3 to N2 and H2 X 1. A method for reducing the content of NH3 and H2 in a combustion system (preferably in a combustion device) to produce N2, HO, NO3, and N2O. X and NO, and exiting the calcination system; (b) optionally and preferably cooling the off-gas in at least one heat exchanger located downstream of the calcination system in the flow direction of the off-gas; and (c) transferring the optionally cooled off-gas to an off-gas treatment system located downstream of the calcination system in the flow direction of the off-gas, if appropriate downstream of the at least one heat exchanger; (d) reducing the N2O content in the off-gas by (d1) decomposing N2O via an N2O decomposition catalyst and / or (d2) chemically reducing N2O with a reducing agent via an N2O reduction catalyst; and (e) reducing the N2O content in the off-gas by (d1) decomposing N2O via an N2O decomposition catalyst and / or (d2) chemically reducing N2O with a reducing agent via an N2O reduction catalyst. X NO by reducing agents over reduction catalysts X NO in the off-gas by chemical reduction of X and (f) optionally and preferably cooling the off-gas in at least one heat exchanger located downstream of the off-gas treatment system in the flow direction of the off-gas.

[0503] Satz3: The method according to any of the preceding sentences, wherein the off-gas is cooled in a single heat exchanger arranged downstream of the calcination system in the flow direction of the off-gas.

[0504] Satz4: A method according to any of the preceding sentences, wherein the off-gas is cooled continuously in at least two heat exchangers arranged downstream of the calcination system in the flow direction of the off-gas.

[0505] Satz5: The method according to any of the preceding sentences, wherein the off-gas is cooled successively in at least three heat exchangers arranged downstream of the calcination system in the flow direction of the off-gas.

[0506] Satz6: The method according to any of the preceding sentences, wherein in step (b) the off-gas is cooled in at least one heat exchanger by releasing heat from the off-gas to a heat transfer medium, the heat transfer medium used being preferably NH3, which is then supplied to catalytic decomposition in an NH3 decomposition device via an NH3 decomposition catalyst.

[0507] Satz7: A method according to any of the preceding sentences, wherein in step (b) the off-gas is cooled in at least one first off-gas / NH3 heat exchanger arranged downstream of the calcination system in the flow direction of the off-gas.

[0508] Satz8: A method according to any of the preceding sentences, wherein the off-gas is cooled in step (b) in a first off-gas / NH3 heat exchanger arranged downstream of the calcination system in the flow direction of the off-gas, and in a second off-gas / NH3 heat exchanger arranged downstream of the first off-gas / NH3 heat exchanger in the flow direction of the off-gas.

[0509] Satz9: A method according to any of the preceding sentences, wherein in step (b) the off-gas is cooled in: - a first off-gas / NH3 heat exchanger arranged downstream of the calcination system in the flow direction of the off-gas, - a second off-gas / NH3 heat exchanger arranged downstream of the first off-gas / NH3 heat exchanger in the flow direction of the off-gas, and - a third off-gas / NH3 heat exchanger arranged downstream of the second off-gas / NH3 heat exchanger in the flow direction of the off-gas.

[0510] Satz10: A method according to any of the preceding sentences, wherein the off-gas is cooled in step (b) to a temperature T2 in the range of 400 to 450°C, more preferably 400 to 420°C.

[0511] Satz11: N2O decomposition catalyst and / or N2O reduction catalyst and / or NO X The method of any of the preceding sentences, wherein the reduction catalyst independently comprises a zeolitic material, preferably a zeolite comprising a transition metal (including lanthanides), in particular iron, cobalt, or copper, more preferably an iron-containing zeolite, even more preferably an iron-containing zeolite of structural type MFI, BEA, FER, MOR, FAU, and / or MEL.

[0512] Satz12: The method of any of the preceding sentences, wherein the N2O decomposition catalyst and the N2O reduction catalyst are formed from the same material.

[0513] Satz13: N2O decomposition catalyst and NO X The method of any of the preceding sentences, wherein the reduction catalysts are formed from the same material.

[0514] Satz14: NO reduction catalyst and NO X The method of any of the preceding sentences, wherein the reduction catalysts are formed from the same material.

[0515] Satz15: N2O decomposition catalyst, N2O reduction catalyst and NO X The method of any of the preceding sentences, wherein the reduction catalysts are formed from the same material.

[0516] Satz16: The method of any of the preceding sentences, wherein the combustion of NH3 in step (a) is not via a catalyst.

[0517] A method according to any of the preceding sentences, wherein the proportion of H2 in the mixture with Satz17:NH3 is at most 80 mol%, more preferably at most 70 mol%, even more preferably at most 60 mol%, most preferably at most 50 mol%, in particular at most 40 mol%.

[0518] A method according to any of the preceding sentences, wherein the proportion of H2 in the mixture with Satz18:NH3 is at least 10 mol%, more preferably at least 20 mol%, even more preferably at least 30 mol%, most preferably at least 40 mol%, in particular at least 50 mol%.

[0519] Satz19: The method of any of the preceding sentences, wherein the molar ratio of H2:NH3 in the mixture ranges from 45:55 to 90:10, preferably from 50:50 to 85:15, more preferably from 55:45 to 80:20, even more preferably from 60:40 to 75:25, and most preferably from 65:35 to 70:30.

[0520] The method of any of the preceding sentences, wherein the Satz20:air ratio λ is in the range of 0.9 to 1.7, preferably 1.0 to 1.6, even more preferably 1.1 to 1.5, and most preferably 1.2 to 1.4.

[0521] Satz21: A method according to any of the preceding sentences, wherein the calcination system, preferably a furnace (preferably comprising a combustion device and an NH3 decomposition device), is incorporated into a system for thermal and / or catalytic decomposition of NH3 to N2 and H2.

[0522] Satz22: Offgas contains more NO than N2O X content, preferably NO X 10. The method according to any of the preceding sentences, wherein the content is at least 2 times, more preferably at least 3 times, even more preferably at least 4 times, most preferably at least 7 times, especially at least 10 times higher than the N2O content.

[0523] Satz23: The method according to any of the preceding sentences, wherein the off-gas has a NO content that is higher than the NO content, preferably the NO content is at least 2 times, more preferably at least 3 times, even more preferably at least 4 times, most preferably at least 7 times, especially at least 10 times higher than the NO content.

[0524] Satz24: A method according to any of the preceding sentences, wherein the off-gas has a NO2 content that is higher than the N2O content, preferably the NO2 content is at least 2 times, more preferably at least 3 times, even more preferably at least 4 times, most preferably at least 7 times, especially at least 10 times higher than the N2O content.

[0525] Satz25: No off-gassing X The NO content is preferably greater than the NO content. X The method according to any of the preceding sentences, wherein the amount of the compound is at least 2 times, more preferably at least 3 times, even more preferably at least 4 times, most preferably at least 7 times, especially at least 10 times the amount of the compound.

[0526] Satz26: The method of any of the preceding sentences, wherein the off-gas has an NO content that is greater than the NO content, preferably the NO content is at least 2 times, more preferably at least 3 times, even more preferably at least 4 times, most preferably at least 7 times, especially at least 10 times higher than the NO content.

[0527] Satz27: A method according to any of the preceding sentences, wherein the off-gas has an N2O content that is higher than the NO2 content, preferably the N2O content is at least 2 times, more preferably at least 3 times, even more preferably at least 4 times, most preferably at least 7 times, especially at least 10 times higher than the NO2 content.

[0528] Satz28: Off-gassing of at least 10 ppmv, preferably at least 20 ppmv, more preferably at least 30 ppmv, even more preferably at least 40 ppmv, especially at least 50 ppmv NO X A method according to any of the preceding sentences having the content.

[0529] Satz 29: Off-gassing of at least 75 ppmv, preferably at least 100 ppmv, more preferably at least 150 ppmv, even more preferably at least 200 ppmv, especially at least 250 ppmv NO X A method according to any of the preceding sentences having the content.

[0530] Satz 30: Off-gas contains at least 500 ppmv, preferably at least 1000 ppmv, more preferably at least 2000 ppmv, even more preferably at least 3000 ppmv, especially at least 3500 ppmv NO X A method according to any of the preceding sentences having the content.

[0531] Satz31: The method according to any of the preceding sentences, wherein the off-gas has an N2O content of at least 10 ppmv, preferably at least 20 ppmv, more preferably at least 30 ppmv, even more preferably at least 40 ppmv, especially at least 50 ppmv.

[0532] Satz32: The method according to any of the preceding sentences, wherein the off-gas has an N2O content of at least 75 ppmv, preferably at least 100 ppmv, more preferably at least 150 ppmv, even more preferably at least 200 ppmv, especially at least 250 ppmv.

[0533] Satz 33: The method according to any of the preceding sentences, wherein the off-gas has an N2O content of at least 500 ppmv, preferably at least 1000 ppmv, more preferably at least 2000 ppmv, even more preferably at least 3000 ppmv, especially at least 3500 ppmv.

[0534] Satz34: The method of any of the preceding sentences, wherein the off-gas has an H2O content of less than 2.0% by volume.

[0535] Satz 35: The method according to any of the preceding sentences, wherein the off-gas has an HO content of more than 4.0 vol.%, preferably at least 5.0 vol.%, more preferably at least 6.0 vol.%, even more preferably at least 7.0 vol.%, most preferably at least 8.0 vol.%, especially at least 9.0 vol.%.

[0536] Satz 36: The method according to any of the preceding sentences, wherein the off-gas has an HO content of at least 10% by volume, preferably at least 12% by volume, more preferably at least 14% by volume, even more preferably at least 16% by volume, most preferably at least 18% by volume, in particular at least 20% by volume.

[0537] Satz 37: The method according to any of the preceding sentences, wherein the off-gas has an HO content in the range of 10±8% by volume, preferably in the range of 10±7% by volume, more preferably in the range of 10±6% by volume, even more preferably in the range of 10±5% by volume, most preferably in the range of 10±4% by volume, in particular in the range of 10±3% by volume.

[0538] Satz 38: The method according to any of the preceding sentences, wherein the off-gas has an HO content in the range of 15±8% by volume, preferably in the range of 15±7% by volume, more preferably in the range of 15±6% by volume, even more preferably in the range of 15±5% by volume, most preferably in the range of 15±4% by volume, in particular in the range of 15±3% by volume.

[0539] Satz 39: The method according to any of the preceding sentences, wherein the off-gas has an HO content in the range of 20±8% by volume, preferably in the range of 20±7% by volume, more preferably in the range of 20±6% by volume, even more preferably in the range of 20±5% by volume, most preferably in the range of 20±4% by volume, in particular in the range of 20±3% by volume.

[0540] Satz40: The method according to any of the preceding sentences, wherein the off-gas has an HO content in the range of 25±8% by volume, preferably in the range of 25±7% by volume, more preferably in the range of 25±6% by volume, even more preferably in the range of 25±5% by volume, most preferably in the range of 25±4% by volume, especially in the range of 25±3% by volume.

[0541] Satz41: The method according to any of the preceding sentences, wherein the off-gas has an HO content in the range of 30±8% by volume, preferably in the range of 30±7% by volume, more preferably in the range of 30±6% by volume, even more preferably in the range of 30±5% by volume, most preferably in the range of 30±4% by volume, in particular in the range of 30±3% by volume.

[0542] Satz 42: The method according to any of the preceding sentences, wherein the off-gas has an N2 content of at most 95% by volume, preferably at most 90% by volume, more preferably at most 85% by volume, even more preferably at most 80% by volume, most preferably at most 75% by volume, in particular at most 70% by volume.

[0543] Satz 43: The method according to any of the preceding sentences, wherein the off-gas has an N2 content of at least 40% by volume, preferably at least 50% by volume, more preferably at least 60% by volume, even more preferably at least 70% by volume, most preferably at least 80% by volume, in particular at least 90% by volume.

[0544] Satz44: The method of any of the preceding sentences, wherein the off-gas preferably comprises further gaseous components selected from the group consisting of O2, CO, CO2, NH3, CH4 and mixtures thereof.

[0545] Satz45: The method according to any of the preceding sentences, wherein the off-gas leaving the calcination system, preferably the furnace, more preferably the combustion device, has a temperature of at least 500°C, more preferably at least 600°C, even more preferably at least 700°C, most preferably at least 800°C, especially at least 900°C.

[0546] Satz46: The method according to any of the preceding sentences, wherein the off-gas leaving the calcination system, preferably the furnace, more preferably the combustion device, has a temperature of at most 1100°C, more preferably at most 1000°C, even more preferably at most 900°C, most preferably at most 800°C, especially at most 700°C.

[0547] Satz47: A method according to any of the preceding sentences, wherein the off-gas leaving the calcination system, preferably the furnace, more preferably the combustion device, is at a pressure of up to 1.5 bar, preferably atmospheric pressure.

[0548] Satz 48: The off-gas from the calcination system, preferably the furnace, more preferably the combustion device, is at least 10%, more preferably at least 20%, even more preferably at least 30%, most preferably at least 40%, especially at least 50% NO X The method of any of the preceding sentences, wherein the oxidation degree is

[0549] Satz 49: The off-gas from the calcination system, preferably the furnace, more preferably the combustion device, is at most 90%, more preferably at most 80%, even more preferably at most 70%, most preferably at most 60%, especially at most 50% NO X The method of any of the preceding sentences, wherein the oxidation degree is

[0550] Satz50: The method of any of the preceding sentences, wherein the off-gas exiting the calcination system, preferably the furnace, more preferably the combustion device, has an O2 content of less than 2.0% by volume.

[0551] Satz51: The method of any of the preceding sentences, wherein the off-gas leaving the calcination system, preferably the furnace, more preferably the combustion device, has an O2 content of more than 4.0% by volume.

[0552] Satz52: The method of any of the preceding sentences, wherein the off-gas entering the off-gas treatment system is at a temperature of at least 300°C, more preferably at least 350°C, even more preferably at least 400°C, most preferably at least 425°C, especially at least 450°C.

[0553] Satz53: A method according to any of the preceding sentences, wherein the off-gas entering the off-gas treatment system is at a temperature of at least 500°C, more preferably at least 550°C, even more preferably at least 600°C, most preferably at least 625°C, especially at least 650°C.

[0554] Satz54: A method according to any of the preceding sentences, wherein the off-gas entering the off-gas treatment system is at a temperature of at most 825°C, more preferably at most 800°C, even more preferably at most 775°C, most preferably at most 750°C, especially at most 725°C.

[0555] Satz55: A method according to any of the preceding sentences, wherein the off-gas entering the off-gas treatment system is at a temperature of at most 700°C, more preferably at most 650°C, even more preferably at most 600°C, most preferably at most 550°C, especially at most 500°C.

[0556] Satz56: The method according to any of the preceding sentences, wherein the off-gas entering the off-gas treatment system is at a temperature that is relatively at least 20°C, preferably at least 40°C, more preferably at least 60°C, even more preferably at least 80°C, most preferably at least 100°C, especially at least 120°C lower than the temperature of the off-gas exiting the calcination system, preferably a furnace, more preferably a combustion device.

[0557] Satz57: A method according to any of the preceding sentences, wherein the off-gas entering the off-gas treatment system is at a pressure of up to 1.2 bar, preferably atmospheric pressure.

[0558] Satz 58: The off-gas entering the off-gas treatment system is at least 10%, more preferably at least 20%, even more preferably at least 30%, most preferably at least 40%, especially at least 50% NO X The method of any of the preceding sentences, wherein the oxidation degree is

[0559] Satz 59: The off-gas entering the off-gas treatment system is at most 90%, more preferably at most 80%, even more preferably at most 70%, most preferably at most 60%, especially at most 50% NO X The method of any of the preceding sentences, wherein the oxidation degree is

[0560] Satz60: The method of any of the preceding sentences, wherein the off-gas entering the off-gas treatment system has an O2 content of less than 2.0% by volume.

[0561] Satz61: The method of any of the preceding sentences, wherein the off-gas entering the off-gas treatment system has an O2 content greater than 4.0% by volume.

[0562] Satz62: A method according to any of the preceding sentences, wherein step (d) comprises (d1) reducing the N2O content in the off-gas by decomposition of N2O via an N2O decomposition catalyst, preferably wherein the N2O decomposition catalyst comprises a zeolitic material, preferably a zeolite comprising a transition metal (including lanthanides), in particular iron, cobalt or copper, more preferably an iron-containing zeolite, even more preferably an iron-containing zeolite of the MFI, BEA, FER, MOR, FAU and / or MEL structural type.

[0563] Satz63: The method of any of the preceding sentences, wherein step (d) comprises (d2) reducing the NO content in the off-gas by chemical reduction of NO with a reducing agent via an NO reduction catalyst, preferably wherein the NO reduction catalyst comprises a zeolitic material, preferably a zeolite comprising a transition metal (including lanthanides), in particular iron, cobalt or copper, more preferably an iron-containing zeolite, even more preferably an iron-containing zeolite of the MFI, BEA, FER, MOR, FAU and / or MEL structural type.

[0564] Satz64: The method of any of the preceding sentences, wherein the reducing agent in step (d2) is selected from NH3, hydrocarbons, CO, H2, and mixtures thereof, preferably NH3.

[0565] Satz65: The method of any of the preceding sentences, wherein the reducing agent in step (d2) is NH3 used in an amount of 0.5 to 2.0 molar parts, preferably 0.8 to 1.8 molar parts, based on the molar ratio of N2O to be chemically reduced.

[0566] Satz66: The method according to any of the preceding sentences, wherein the reducing agent in step (d2) is a hydrocarbon or a mixture of several hydrocarbons, preferably used in an amount of 0.2 to 1.0 molar parts, more preferably 0.2 to 0.7 molar parts, based on the molar ratio of the N2O to be decomposed.

[0567] Satz67:NO X The method of any of the preceding sentences, wherein the reduction catalyst comprises a zeolitic material, preferably a zeolite comprising a transition metal (including lanthanides), in particular iron, cobalt or copper, more preferably an iron-containing zeolite, even more preferably an iron-containing zeolite of the MFI, BEA, FER, MOR, FAU and / or MEL structural type.

[0568] Satz68: The method of any of the preceding sentences, wherein the reducing agent in step (e) is selected from NH3, hydrocarbons, CO, H2 and mixtures thereof, preferably NH3.

[0569] Satz69: The reducing agent in step (e) is NO that is chemically reduced. X. The method of any of the preceding sentences, wherein NH3 is used in an amount of 0.9 to 2.5 molar parts, preferably 1.0 to 1.4 molar parts, more preferably 1.0 to 1.2 molar parts based on a molar ratio of

[0570] Satz70: The method of any of the preceding sentences, wherein the reducing agent in step (d2) is the same as the reducing agent in step (e), preferably NH3.

[0571] Satz71: An off-gas treatment system includes a first reaction zone and a second reaction zone, and the off-gas passes through the first reaction zone and the second reaction zone successively. A reducing agent is added to the off-gas upstream of the first reaction zone, and NO in the off-gas is removed in the first reaction zone. X The content is first, NO X NO by reducing agents via reduction catalysts X(step (e)), the N2O content in the off-gas is optionally further reduced by decomposition of N2O via an N2O decomposition catalyst (step (d1)) and / or chemical reduction of N2O with a reducing agent via an N2O reduction catalyst (step (d2)), and a further reducing agent is optionally added to the off-gas upstream of the second reaction zone, and then in the second reaction zone, the N2O content in the off-gas is reduced by decomposition of N2O via an N2O decomposition catalyst (step (d1)) and / or chemical reduction of N2O with a reducing agent via an N2O reduction catalyst (step (d2)), and the N2O content in the off-gas is optionally further reduced by decomposition of N2O via an N2O decomposition catalyst (step (d1)) and / or chemical reduction of N2O with a reducing agent via an N2O reduction catalyst (step (d2)), and the N2O content in the off-gas is optionally added to the off-gas upstream of the second reaction zone, and then in the second reaction zone, the N2O content in the off-gas is optionally reduced by decomposition of N2O via an N2O decomposition catalyst (step (d1)) and / or chemical reduction of N2O with a reducing agent via an N2O reduction catalyst (step (d2)), and the N2O content in the off-gas is optionally added to the off-gas upstream of the second reaction zone, and X The content may optionally be NO X NO via reduction catalyst X is further reduced by chemical reduction of (step (e)).

[0572] Satz72: NO in the first reaction zone X The method of sentence 71, wherein the reduction catalyst comprises a conventional SCR catalyst, preferably based on V2O5-WO3- / TiO2.

[0573] Satz73: The method of sentence 71 or 72, wherein the temperature of the off-gas entering the first reaction zone is 400°C or less, more preferably 350°C or less.

[0574] Satz74: The method of any of sentences 71 to 73, wherein the N2O decomposition catalyst in the second reaction zone comprises a zeolitic material, preferably a zeolite containing a transition metal (including a lanthanide), in particular iron, cobalt or copper, more preferably an iron-containing zeolite, even more preferably an iron-containing zeolite of the MFI, BEA, FER, MOR, FAU and / or MEL type.

[0575] Satz75: A method according to any of sentences 71 to 74, wherein the temperature of the off-gas entering the second reaction zone is in the range of 300 to 550°C, preferably 350 to 500°C.

[0576] Satz76: NO in the first reaction zoneX 76. The method of any of sentences 71 to 75, wherein the reduction catalyst comprises a zeolite material, preferably a zeolite containing a transition metal (including lanthanides), in particular iron, cobalt or copper, more preferably an iron-containing zeolite, even more preferably an iron-containing zeolite of the MFI, BEA, FER, MOR, FAU and / or MEL type.

[0577] Satz77: A method according to any of sentences 71 to 76, wherein the temperature of the off-gas entering the first reaction zone is at least 300°C, more preferably at least 350°C, and even more preferably at least 400°C.

[0578] Satz78: A method according to any of sentences 71 to 77, wherein the temperature of the off-gas entering the first reaction zone is at most 600°C, preferably at most 550°C.

[0579] Satz79: The N2O decomposition catalyst in the second reaction zone X 79. The method of any of sentences 71 to 78, comprising a sensitive N2O decomposition catalyst.

[0580] Satz80: A method according to any of sentences 71 to 79, wherein the temperature of the off-gas entering the second reaction zone is at least 300°C, more preferably at least 350°C, and even more preferably at least 400°C.

[0581] Satz81: The method of any of sentences 71 to 80, wherein the temperature of the off-gas entering the second reaction zone is at most 600°C, preferably at most 550°C.

[0582] Satz 82: The off-gas after leaving the first reaction zone and before entering the second reaction zone has a NO concentration in the range of 0 to 200 ppmv, preferably 1 to 200 ppmv. X 82. The method of any of sentences 71 to 81, having a N2O content in the range of 200 to 2000 ppmv.

[0583] Satz 83: The off-gas after leaving the first reaction zone and before entering the second reaction zone has a NO concentration of up to 20 ppmv, more preferably up to 10 ppmv, and even more preferably up to 5 ppmv. X 83. The method of any of sentences 71 to 82, having a N2O content in the range of 200 to 2000 ppmv.

[0584] Satz84: The off-gas treatment system also includes a first reaction zone and a second reaction zone, and the off-gas passes through the first reaction zone and the second reaction zone successively. A reducing agent is added to the off-gas between the first reaction zone and the second reaction zone. In the first reaction zone, the NO content in the off-gas is first reduced by decomposition of NO via an NO decomposition catalyst (step (d1)). Then, in the second reaction zone, the NO in the off-gas is reduced. X The content is NO X NO by reducing agents via reduction catalysts X (step (e)), the N2O content in the off-gas is optionally further reduced by further decomposition of N2O via an N2O decomposition catalyst (step (d1)) and / or chemical reduction of N2O with a reducing agent via an N2O reduction catalyst (step (d2)).

[0585] Satz85: The method of sentence 84, wherein no reducing agent is added to the off-gas upstream of the first reaction zone.

[0586] Satz 86: The method of sentence 84 or 85, wherein the N2O decomposition catalyst in the first reaction zone comprises a zeolitic material, preferably a zeolite containing a transition metal (including lanthanides), in particular iron, cobalt or copper, more preferably an iron-containing zeolite, even more preferably an iron-containing zeolite of the MFI, BEA, FER, MOR, FAU and / or MEL type.

[0587] Satz 87: The N2O decomposition catalyst in the first reaction zone X87. The method of any of sentences 84 to 86, comprising a sensitive N2O decomposition catalyst.

[0588] Satz88: NO in the second reaction zone X A method according to any of sentences 84 to 87, wherein the reduction catalyst comprises a zeolite material, preferably a zeolite containing a transition metal (including lanthanides), in particular iron, cobalt or copper; more preferably an iron-containing zeolite; even more preferably an iron-containing zeolite of the MFI, BEA, FER, MOR, FAU and / or MEL type.

[0589] Satz89: A method according to any of sentences 84 to 88, wherein in the first reaction zone and the second reaction zone, the space velocity is set so that the N2O content in the off-gas is reduced by up to 95%, preferably up to 90%, in the first reaction zone, based on the N2O content in the off-gas entering the first reaction zone.

[0590] Satz90: The method of any of sentences 84 to 89, wherein in the second reaction zone, the N2O content in the off-gas is further reduced by at least 30%, preferably at least 40%, more preferably at least 50%, based on the N2O content in the off-gas entering the second reaction zone.

[0591] Satz91: A method according to any of sentences 84 to 90, wherein in the second reaction zone, the N2O content in the off-gas is further reduced by chemical reduction of N2O with a reducing agent via an N2O reduction catalyst (step (d2)).

[0592] Satz92: The method of any of sentences 71 to 91, wherein the first reaction zone and the second reaction zone are spatially separated.

[0593] Satz93: The method of any of sentences 71 to 92, wherein the first reaction zone and the second reaction zone are spatially connected to each other.

[0594] Satz94: The method of any of sentences 71 to 93, wherein the first reaction zone and the second reaction zone are disposed within a common vessel.

[0595] Satz95: A method according to any of sentences 71 to 94, wherein the off-gas temperature of the first reaction zone and the second reaction zone is up to 500°C, preferably in the range of 350 to 450°C.

[0596] Satz96: The method of any of sentences 71 to 95, wherein the space velocity in the first reaction zone is greater than the space velocity in the second reaction zone, preferably at least 1.2 times, more preferably at least 1.4 times, even more preferably at least 1.6 times, most preferably at least 1.8 times, and especially at least 2.0 times greater.

[0597] Satz97: The method of any of sentences 71 to 96, wherein the space velocity in the first reaction zone is less than the space velocity in the second reaction zone, preferably at least 1.5 times, more preferably at least 2.0 times, even more preferably at least 3.0 times, most preferably at least 5.0 times, and especially at least 10.0 times less.

[0598] Satz98: A method according to any of sentences 71 to 97, wherein the temperature of the first reaction zone is at least 450°C, more preferably at least 500°C, even more preferably at least 550°C, most preferably at least 600°C, especially at least 650°C.

[0599] Satz99: A method according to any of sentences 71 to 98, wherein the temperature of the second reaction zone is at most 600°C, more preferably at most 550°C, even more preferably at most 500°C, most preferably at most 450°C, especially at most 400°C.

[0600] Satz100: The method of any of sentences 71 to 99, wherein the temperature of the first reaction zone is at least 20°C, more preferably at least 40°C, even more preferably at least 60°C, most preferably at least 80°C, especially at least 100°C higher relative to the temperature of the second reaction zone.

[0601] Satz101: The method of any of sentences 71 to 100, wherein the temperature of the first reaction zone is relatively at least 120°C, more preferably at least 140°C, even more preferably at least 160°C, most preferably at least 180°C, especially at least 200°C higher than the temperature of the second reaction zone.

[0602] Satz102: Off-gas exits the off-gas treatment system with a residual NO of at most 20 ppmv, preferably at most 15 ppmv, more preferably at most 10 ppmv, even more preferably at most 7.5 ppmv, most preferably at most 5.0 ppmv, especially at most 2.5 ppmv. X A method according to any of the preceding sentences having the content.

[0603] Satz103: The method of any of the preceding sentences, wherein the off-gas leaves the off-gas treatment system and has a residual N2O content of at most 20 ppmv, preferably at most 15 ppmv, more preferably at most 10 ppmv, even more preferably at most 7.5 ppmv, most preferably at most 5.0 ppmv, especially at most 2.5 ppmv.

[0604] Satz104: The method of any of the preceding sentences, wherein the N2O decomposition catalyst is disposed in a radial basket through which the flow passes axially.

[0605] Satz105: The method of any of the preceding sentences, wherein the N2O decomposition catalyst is in particulate form and comprises at least 50 particles.

[0606] Satz106: The method of any of the preceding sentences, wherein the N2O reduction catalyst is disposed in a radial basket through which the flow passes axially.

[0607] Satz107: The method of any of the preceding sentences, wherein the N2O reduction catalyst is in particulate form and comprises at least 50 particles.

[0608] Satz108:NO X The method of any of the preceding sentences, wherein the reduction catalyst is disposed in a radial basket through which the flow passes axially.

[0609] Satz109:NO X The method of any of the preceding sentences, wherein the reduction catalyst is in particulate form and comprises at least 50 particles.

[0610] Satz110: A method according to any of the preceding sentences, wherein at least one parameter characteristic of a current operating state of the baking system is measured as a first measurement variable in the baking system.

[0611] Satz111: The method of sentence 110, wherein the first measurement variable is selected from the group consisting of combustion temperature, NH3 consumption, suitable rotation speed, and volume of the calcination system.

[0612] Satz112: A method according to any of the preceding sentences, wherein at least one parameter characteristic of the current state of the off-gas before it enters the off-gas treatment system is measured as a second measurement variable before it enters the off-gas treatment system.

[0613] Satz113: The second measured variable is NO in the off-gas. X Content, NO in off-gas X the degree of oxidation of the off-gas, the N2O content in the off-gas, the content of other components in the off-gas, such as H2O, O2, and N2, the off-gas temperature, the off-gas pressure, and the volumetric flow rate of the off-gas.

[0614] Satz114: A method according to any of the preceding sentences, in which at least one parameter characteristic of the current state of the off-gas leaving the exhaust gas treatment system is measured as a third measurement variable as it leaves the exhaust gas treatment system.

[0615] Satz115: The third measured variable is NO in the off-gas X Content, NO in off-gas X the degree of oxidation of the off-gas, the N2O content in the off-gas, the content of other components in the off-gas, such as H2O, O2, and N2, the off-gas temperature, the off-gas pressure, and the volumetric flow rate of the off-gas.

[0616] Satz116: A method according to any of the preceding sentences, wherein the off-gas treatment system comprises a first reaction zone and a second reaction zone, the off-gas continuously flows through the first reaction zone and the second reaction zone, a reducing agent is supplied between the first reaction zone and the second reaction zone, and at least one parameter characteristic of the current state of the off-gas after exiting the first reaction zone and before entering the second reaction zone is measured as the fourth measurement variable after exiting the first reaction zone and before entering the second reaction zone.

[0617] Satz117: The fourth measured variable is NO in the off-gas. X Content, NO in off-gas X the degree of oxidation of the off-gas, the N2O content in the off-gas, the content of other components in the off-gas, such as H2O, O2, and N2, the off-gas temperature, the off-gas pressure, and the volumetric flow rate of the off-gas.

[0618] Satz118: A method according to any of sentences 110 to 117, wherein the control of the method is based on the first measured variable and / or the second measured variable and / or the third measured variable and / or the fourth measured variable by controlled variation of the manipulated variable.

[0619] Satz119: The method of sentence 118, wherein the manipulated variable is the amount of metered reducing agent.

[0620] Satz120: A method according to any of the preceding sentences, wherein the off-gas is cooled in a single heat exchanger arranged downstream of the off-gas treatment system in the flow direction of the off-gas.

[0621] Satz121: A method according to any of the preceding sentences, in which the off-gas is cooled successively in at least two heat exchangers arranged downstream of the off-gas treatment system in the flow direction of the off-gas.

[0622] Satz122: A method according to any of the preceding sentences, in which the off-gas is cooled successively in at least three heat exchangers arranged downstream of the off-gas treatment system in the flow direction of the off-gas.

[0623] Satz123: A method according to any of the preceding sentences, in which the off-gas is cooled successively in at least four heat exchangers arranged downstream of the off-gas treatment system in the flow direction of the off-gas.

[0624] Satz124: A method according to any of the preceding sentences, in which the off-gas is cooled successively in at least five heat exchangers arranged downstream of the off-gas treatment system in the flow direction of the off-gas.

[0625] Satz125: A method according to any of the preceding sentences, wherein the off-gas is cooled in at least one heat exchanger in step (f) by release of heat from the off-gas to a heat transfer medium, the heat transfer medium preferably being selected from the group consisting of water, steam, combustion air, NH3 and combinations thereof.

[0626] Satz126: A method according to any of the preceding sentences, wherein in step (f) the off-gas is cooled in a first off-gas / H2O heat exchanger arranged downstream of the off-gas treatment system in the flow direction of the off-gas.

[0627] Satz127: A method according to any of the preceding sentences, wherein in step (f) the off-gas is cooled in a first off-gas / combustion air heat exchanger arranged downstream of the off-gas treatment system in the flow direction of the off-gas.

[0628] Satz128: A method according to any of the preceding sentences, in which the off-gas is cooled in step (f) in a first off-gas / H2O heat exchanger arranged downstream of the off-gas treatment system in the flow direction of the off-gas, and in a first off-gas / combustion air heat exchanger also arranged downstream of the off-gas treatment system in the flow direction of the off-gas, preferably arranged downstream of the first off-gas / H2O heat exchanger.

[0629] Satz129: A method according to any of the preceding sentences, in which the off-gas is cooled in step (f) in: - a first off-gas / combustion air heat exchanger arranged downstream of the off-gas treatment system in the flow direction of the off-gas, and - a second off-gas / combustion air heat exchanger arranged downstream of the first off-gas / combustion air heat exchanger in the flow direction of the off-gas.

[0630] Satz130: A method according to any of the preceding sentences, wherein the off-gas is cooled in step (f) in: - a first off-gas / combustion air heat exchanger arranged downstream of the off-gas treatment system in the flow direction of the off-gas, - a first off-gas / H2O heat exchanger arranged downstream of the first off-gas / combustion air heat exchanger in the flow direction of the off-gas, and - a second off-gas / combustion air heat exchanger arranged downstream of the first off-gas / H2O heat exchanger in the flow direction of the off-gas.

[0631] Satz131: The method of any of the preceding sentences, wherein in step (f) the off-gas is cooled in at least one off-gas / combustion gas heat exchanger arranged downstream of the off-gas treatment system in the flow direction of the off-gas, preferably downstream of the first off-gas / combustion air heat exchanger, the first off-gas / H2O heat exchanger, and / or the second off-gas / combustion air heat exchanger.

[0632] Satz132: The method of any of the preceding sentences, wherein in step (f) the off-gas is cooled in at least one off-gas / combustion gas heat exchanger arranged downstream of the off-gas treatment system in the flow direction of the off-gas, preferably downstream of the first off-gas / combustion air heat exchanger, the first off-gas / H2O heat exchanger, and / or the second off-gas / combustion air heat exchanger.

[0633] Satz133: The method of any of the preceding sentences, wherein in step (f) the off-gas is cooled in at least one second off-gas / H2O heat exchanger arranged downstream of the off-gas treatment system in the flow direction of the off-gas, preferably downstream of the first off-gas / combustion air heat exchanger, the first off-gas / H2O heat exchanger, and / or the second off-gas / combustion air heat exchanger.

[0634] Satz134: A method according to any of the preceding sentences, wherein in the method of step (f), the off-gas is cooled - in a first off-gas / combustion air heat exchanger arranged downstream of the off-gas treatment system in the flow direction of the off-gas, - in a first off-gas / H2O heat exchanger arranged downstream of the first off-gas / combustion air heat exchanger in the flow direction of the off-gas, - in a second off-gas / combustion air heat exchanger arranged downstream of the first off-gas / H2O heat exchanger in the flow direction of the off-gas, and - in an off-gas / combustion gas heat exchanger arranged downstream of the second off-gas / combustion air heat exchanger in the flow direction of the off-gas.

[0635] Satz135: A method according to any of the preceding sentences, wherein the off-gas is cooled in step (f) in: - a first off-gas / combustion air heat exchanger arranged downstream of the off-gas treatment system in the flow direction of the off-gas, - a first off-gas / H2O heat exchanger arranged downstream of the first off-gas / combustion air heat exchanger in the flow direction of the off-gas, - a second off-gas / combustion air heat exchanger arranged downstream of the first off-gas / H2O heat exchanger in the flow direction of the off-gas, and - a second off-gas / H2O heat exchanger arranged downstream of the second off-gas / combustion air heat exchanger in the flow direction of the off-gas.

[0636] Satz136: A method according to any of the preceding sentences, wherein in step (f) the off-gas is cooled - in a first off-gas / combustion air heat exchanger arranged downstream of the off-gas treatment system in the flow direction of the off-gas, - in a first off-gas / H2O heat exchanger arranged downstream of the first off-gas / combustion air heat exchanger in the flow direction of the off-gas, - in a second off-gas / combustion air heat exchanger arranged downstream of the first off-gas / H2O heat exchanger in the flow direction of the off-gas, - in an off-gas / combustion gas heat exchanger arranged downstream of the second off-gas / combustion air heat exchanger in the flow direction of the off-gas, and - in a second off-gas / H2O heat exchanger arranged downstream of the off-gas / combustion gas heat exchanger in the flow direction of the off-gas.

[0637] Satz137: An apparatus comprising: (i) an NH3-powered calcination system, preferably a furnace for catalytic decomposition of NH3 into N2 and H2 (preferably including a combustion device and an NH3 decomposition device), and (ii) an off-gas treatment system, and configured to carry out a method as described in any of the preceding sentences. [Brief explanation of the drawings]

[0638] [Figure 1] 1 shows a schematic diagram of a preferred embodiment of the present invention; [Figure 2] 1 shows a schematic diagram of a preferred embodiment of the present invention (Process Variant #1). [Figure 3]1 shows a schematic diagram of a preferred embodiment of the present invention (Process Variant #2). [Figure 4] 1 shows a schematic diagram of a preferred embodiment of the present invention (process variant #3). [Figure 5] 1 shows a schematic diagram of a preferred embodiment of the present invention (process variant #4). [Figure 6] Schematic diagrams of three preferred embodiments of the present invention that are similar to each other are shown (process variants #5, #6 and #7). [Figure 7] 1 shows a schematic diagram of a preferred embodiment of the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0639] Particularly preferred embodiments of the present invention are described below with reference to the drawings, in all of which the NH3 is preferably preheated, if necessary exclusively or additionally, with water vapor and water vapor condensate.

[0640] Figure 1 shows a schematic diagram of a preferred embodiment of the present invention. NH3 is supplied to an NH3 decomposition device (1) with a configuration similar to that of a primary reformer, where it is catalytically decomposed through an NH3 decomposition catalyst into a product gas containing H2 + N2 + NH3. In parallel, a combustion gas containing NH3 + N2 + H2 is mixed with combustion air containing N2 + O2 in a combustion device (2) and combusted. The combustion heat generated therein burns the NH3 decomposition device (1). N2 + H2O + NO X The off-gas produced by combustion containing +N2O enters the off-gas duct (3) and X The off-gas is fed to an off-gas treatment system (4), where its N and H O content is substantially completely removed. The off-gas containing N and H O leaving the off-gas treatment system passes through a ventilation system (5) and leaves the system through a chimney (6). The product gas formed by catalytic decomposition containing H, N, and NH is separated in a pressure swing adsorption system (7) into H as product and an off-gas containing NH, N, and H, which can be used as combustion gas if necessary after metered addition of additional NH.

[0641] 2 shows a schematic diagram of a preferred embodiment of the present invention (Process Variant #1). The off-gas duct includes, in the off-gas flow direction, a first off-gas / NH heat exchanger (Q1), through which NH absorbs heat from the off-gas and is supplied to an NH decomposition device. An off-gas treatment system is arranged downstream of the first off-gas / NH heat exchanger (Q1) in the off-gas flow direction. Downstream of the off-gas treatment system in the off-gas flow direction is arranged a first off-gas / H2O heat exchanger (Q5), through which water absorbs heat from the off-gas. Downstream of the first off-gas / H2O heat exchanger (Q5) in the off-gas flow direction is arranged a second off-gas / combustion air heat exchanger (Q6), through which combustion air absorbs heat from the off-gas and is then supplied to a combustion device.

[0642] 3 shows a schematic diagram of a preferred embodiment of the present invention (Process Variant #2). The off-gas duct includes, in the off-gas flow direction, a first off-gas / NH heat exchanger (Q1), in which NH absorbs heat from the off-gas and is then fed to a first pre-reactor (NH decomposition device) for partial catalytic decomposition of NH. This preferably cools the intermediate product gas, for example, from 650°C at the inlet of the first pre-reactor to 360°C upon exiting the first pre-reactor. Downstream of the first off-gas / NH heat exchanger (Q1) in the off-gas flow direction is a second off-gas / NH heat exchanger (Q2), in which the intermediate product gas absorbs heat from the off-gas and is then fed to an NH decomposition device for catalytic decomposition of NH. An off-gas treatment system is located downstream of the second off-gas / NH heat exchanger (Q2) in the off-gas flow direction. In the first off-gas / H2O heat exchanger (Q5), which is arranged downstream of the off-gas treatment system in the flow direction of the off-gas, water absorbs heat from the off-gas. Downstream of the first off-gas / H2O heat exchanger (Q5), in the flow direction of the off-gas, there is arranged a second off-gas / combustion air heat exchanger (Q6), in which combustion air absorbs heat from the off-gas and is then supplied to the combustion device.

[0643] 4 shows a schematic diagram of a preferred embodiment of the present invention (Process Variant #3). The off-gas duct includes, in the flow direction of the off-gas, a first off-gas / NH heat exchanger (Q1), through which NH absorbs heat from the off-gas and is then fed to a first pre-reactor (NH decomposition device) for partial catalytic decomposition of NH. This preferably cools the first intermediate product gas, for example, from 650°C at the inlet of the first pre-reactor to 480°C upon exiting the first pre-reactor. Downstream of the first off-gas / NH heat exchanger (Q1) in the flow direction of the off-gas, is a second off-gas / NH heat exchanger (Q2), through which the intermediate product gas absorbs heat from the off-gas and is then fed to a second pre-reactor (NH decomposition device) for partial catalytic decomposition of NH. This preferably cools the second intermediate product gas, for example, from 630°C at the inlet of the second pre-reactor to 510°C upon exiting the second pre-reactor. A third off-gas / NH3 heat exchanger (Q3) is disposed downstream of the second off-gas / NH3 heat exchanger (Q2) in the off-gas flow direction, and the intermediate product gas absorbs heat from the off-gas and is then supplied to an NH3 decomposition device for catalytic decomposition of NH3. An off-gas treatment system is disposed downstream of the third off-gas / NH3 heat exchanger (Q3) in the off-gas flow direction. In a first off-gas / H2O heat exchanger (Q5) disposed downstream of the off-gas treatment system in the off-gas flow direction, water absorbs heat from the off-gas. A second off-gas / combustion air heat exchanger (Q6) is disposed downstream of the first off-gas / H2O heat exchanger (Q5) in the off-gas flow direction, and combustion air absorbs heat from the off-gas and is then supplied to a combustion device.

[0644] Figure 5 shows a schematic diagram of a preferred embodiment of the present invention (Process Variant #4). The off-gas duct includes, in the flow direction of the off-gas, a first off-gas / NH heat exchanger (Q1), in which NH absorbs heat from the off-gas and is then fed to a first pre-reactor (NH decomposition device) for partial catalytic decomposition of NH. This preferably cools the intermediate product gas, for example, from 650 °C at the inlet of the first pre-reactor to 360 °C upon exiting the first pre-reactor. Downstream of the first off-gas / NH heat exchanger (Q1) in the flow direction of the off-gas is a second off-gas / NH heat exchanger (Q2), in which the intermediate product gas absorbs heat from the off-gas and is then fed to an NH decomposition device for catalytic decomposition of NH. An off-gas treatment system is located downstream of the second off-gas / NH heat exchanger (Q2) in the flow direction of the off-gas. A first off-gas / combustion air heat exchanger (Q4), in which combustion air absorbs heat from the off-gas, is located downstream of the off-gas treatment system in the off-gas flow direction. A first off-gas / H2O heat exchanger (Q5), in which water absorbs heat from the off-gas, is located downstream of the first off-gas / combustion air heat exchanger (Q4). A second off-gas / combustion air heat exchanger (Q6), in which combustion air absorbs heat from the off-gas and is then supplied to the first off-gas / combustion air heat exchanger (Q4) and then to the combustion device, is located downstream of the first off-gas / combustion air heat exchanger (Q4). Thus, the combustion air is heated in two stages: first in the second off-gas / combustion air heat exchanger (Q6) and then in the first off-gas / combustion air heat exchanger (Q4).

[0645] FIG. 6 shows schematic diagrams of three similar preferred embodiments of the present invention (Process Variants #5, #6, and #7). In all three process variants, the off-gas duct includes a first off-gas / NH heat exchanger (Q1) in the off-gas flow direction, where NH absorbs heat from the off-gas and is then fed to a first pre-reactor (NH decomposition device) for partial catalytic decomposition of NH. This preferably cools the intermediate product gas, for example, from 650° C. at the inlet of the first pre-reactor to 360° C. upon exiting the first pre-reactor. Downstream of the first off-gas / NH heat exchanger (Q1) in the off-gas flow direction is a second off-gas / NH heat exchanger (Q2), where the intermediate product gas absorbs heat from the off-gas and is then fed to an NH decomposition device for catalytic decomposition of NH. An off-gas treatment system is located downstream of the second off-gas / NH heat exchanger (Q2) in the off-gas flow direction. A first off-gas / combustion air heat exchanger (Q4), in which combustion air absorbs heat from the off-gas, is located downstream of the off-gas treatment system in the off-gas flow direction. A first off-gas / H2O heat exchanger (Q5), in which water absorbs heat from the off-gas, is located downstream of the first off-gas / combustion air heat exchanger (Q4). A second off-gas / combustion air heat exchanger (Q6), in which combustion air absorbs heat from the off-gas and is then supplied to the first off-gas / combustion air heat exchanger (Q4) and then to the combustion device, is located downstream of the first off-gas / combustion air heat exchanger (Q4). Thus, the combustion air is heated in two stages: first in the second off-gas / combustion air heat exchanger (Q6) and then in the first off-gas / combustion air heat exchanger (Q4). Downstream of the second offgas / combustion air heat exchanger (Q6) in the offgas flow direction is an offgas / combustion gas heat exchanger (Q7), where combustion gas, i.e., offgas from the pressure swing adsorption device, absorbs heat from the offgas and is then supplied to a combustion device. In the second offgas / H2O heat exchanger (Q8), located downstream of the first offgas / combustion gas heat exchanger (Q7) in the offgas flow direction, water absorbs heat from the offgas.

[0646] In process variant #5, the residual heat remaining in the off-gas is removed by water in the second off-gas / H2O heat exchanger (Q8) and released to NH3, thus preheating it from a liquid state (storage temperature -33.5°C) to, for example, -8°C.

[0647] In process variant #6, heat is removed with water in the first off-gas / H2O heat exchanger (Q5) and released to NH3, which is thereby preheated from the liquid state to, for example, 30° C. Residual heat remaining in the off-gas is removed with water in the second off-gas / H2O heat exchanger (Q8) and also released to NH3, which is thereby heated to, for example, 45° C.

[0648] In process variant #7, heat is removed by water in the first off-gas / H2O heat exchanger (Q5) and released to NH3, thus preheating it from the liquid state to, for example, 30°C. Residual heat remaining in the off-gas is removed by water in the second off-gas / H2O heat exchanger (Q8) and also released to NH3, thereby heating it to, for example, 39°C. The amount of preheated boiler feed water is increased compared to the amount required for steam generation. Excess boiler feed water is fed to the steam condensate stream below the NH3 evaporator and serves as an additional heat transfer medium.

[0649] The mass balances and temperature profiles for process variants #1 through #7 are summarized in the table below. All data are scaled to a plant capacity of 1000 mtpd of NH3. The bold numbers 1 through 28 refer to the corresponding labeled locations in Figure 7. We distinguish two cases, A and B, in which the off-gas contains different nitrogen oxide contents in each case. In case A, the off-gas in both cases contains a relatively low nitrogen oxide content of 500 ppmv NO, 10 ppmv NO2, and 10 ppmv NO2. In case B, the off-gas in both cases contains a relatively high nitrogen oxide content of 5000 ppmv NO, 10 ppmv NO2, and 50 ppmv NO2. [Table 4] [Table 5] [Table 6] [Table 7] [Table 8] [Table 9] [Table 10] [Table 11] [Table 12] [Table 13] [Table 14] [Table 15] [Table 16] [Table 17] [Table 18] By selecting the right heat exchanger in the off-gas duct with the right placement, the present invention makes it possible to recover heat from the off-gas duct up to the theoretical maximum of the water dew point plus a safety margin. There is a clear correlation between heat recovery rate and H2 yield. A highly integrated heat recovery system can increase H2 yield by more than 4%.

[0650] The flat temperature profile, which allows for significant heat integration, also reduces the required inlet temperature of the off-gas to the off-gas duct, which in turn reduces the surface temperatures of the upstream heat exchangers and allows for the use of simpler materials. [Explanation of symbols]

[0651] (Q1) First off-gas / NH3 heat exchanger (Q2) Second off-gas / NH3 heat exchanger (Q3) Third Offgas / NH3 Heat Exchanger (Q4) First off-gas / combustion air heat exchanger (Q5) First off-gas / H2O heat exchanger (Q6) Second exhaust / combustion air heat exchanger (Q7) Offgas / Fuel Gas Heat Exchanger (Q8) Second Offgas / H2O Heat Exchanger (1) NH3 decomposition device (2) Combustion devices (3) Off-gas duct (4) Off-gas treatment system (5) Ventilation equipment (6) Chimney (7) Pressure Swing Adsorption Device

Claims

1. NH ３ NO in the off-gas of the operating firing system Ｘ and N ２ 1. A method for reducing the content of O, comprising the steps of: (a) NH ３ N ２ and H ２ for catalytic decomposition into ３ is combusted, preferably with a combustion device and NH ３ Operate the calcination system including a decomposition device, and ２ , H ２ O, NO Ｘ and N ２ generating an off-gas comprising O and exiting the calcination system; (b) optionally and preferably cooling the off-gas in at least one heat exchanger arranged downstream of the calcination system in the flow direction of the off-gas; (c) transferring the optionally cooled off-gas to an off-gas treatment system; (d) N in the off-gas ２ The O content is (d1) N ２ N via O decomposition catalyst ２ by decomposing O, and / or (d2) N ２ O reduction catalyst using a reducing agent ２ By chemically reducing O reducing the (e) NO Ｘ NO by reducing agent over reduction catalyst Ｘ NO in the off-gas by chemical reduction of Ｘ Reducing the content; (f) optionally and preferably cooling the off-gas in at least one heat exchanger arranged downstream of the off-gas treatment system in a flow direction of the off-gas; A method comprising:

2. NH ３ N ２ and H ２ NH ３ and H ２ NO in the off-gas of the operating firing system Ｘ and N ２ 10. The method of claim 1 for reducing the content of O, comprising: (a) NH (preferably in a combustion device) for operation of the calcination system ３ and H ２ is burned, and N ２ , H ２ O, NO Ｘ and N ２ generating an off-gas comprising O and exiting the calcination system; (b) optionally and preferably cooling the off-gas in at least one heat exchanger arranged downstream of the calcination system in the flow direction of the off-gas; (c) transferring the optionally cooled off-gas to an off-gas treatment system located downstream of the calcination system in the flow direction of the off-gas, if appropriate downstream of at least one heat exchanger; (d) N in the off-gas ２ The O content is (d1) N ２ N via O decomposition catalyst ２ by decomposing O, and / or (d2) N ２ O reduction catalyst using a reducing agent ２ By chemically reducing O reducing the (e) NO Ｘ NO by reducing agent over reduction catalyst Ｘ NO in the off-gas by chemical reduction of Ｘ Reducing the content; (f) optionally and preferably cooling the off-gas in at least one heat exchanger arranged downstream of the off-gas treatment system in a flow direction of the off-gas; A method comprising:

3. The off-gas is cooled in step (b) in the at least one heat exchanger by releasing heat from the off-gas to a heat transfer medium, the heat transfer medium used preferably being NH ３ and then NH ３ NH via decomposition catalyst ３ 3. The method of claim 1 or 2, wherein the mixture is fed to catalytic cracking in a cracking device.

4. The off-gas is fed to at least one first off-gas / NH3 feedstream located downstream of the calcination system in the flow direction of the off-gas. ３ 4. The method of claim 1, wherein the cooling in step (b) is performed in a heat exchanger.

5. The off-gas is subjected in step (b) to a first offgas / NH3 arranged downstream of the calcination system in the flow direction of the offgas; ３ in the heat exchanger, and - in the flow direction of the off-gas, the first off-gas / NH ３ A second off-gas / NH disposed downstream of the heat exchanger ３ In the heat exchanger, 5. The method of claim 1, wherein the process is cooled.

6. The off-gas is subjected in step (b) to a first offgas / NH3 arranged downstream of the calcination system in the flow direction of the offgas; ３ In the heat exchanger, - in the flow direction of the off-gas, the first off-gas / NH ３ A second off-gas / NH disposed downstream of the heat exchanger ３ In the heat exchanger, - in the flow direction of the off-gas, the second off-gas / NH ３ A third off-gas / NH3 located downstream of the heat exchanger ３ In the heat exchanger, 6. The method of claim 1, wherein the process is cooled.

7. The off-gas is heated in step (b) to a temperature T in the range of 400 to 450°C, more preferably 400 to 420°C. ２ 7. The method of claim 1, wherein the mixture is cooled to 100°C.

8. The N ２ O decomposition catalyst and / or the N ２ O reduction catalyst and / or the NO Ｘ 8. The method of any one of claims 1 to 7, wherein the reduction catalyst independently comprises a zeolite material, preferably a zeolite comprising a transition metal (including lanthanides), in particular iron, cobalt or copper, more preferably an iron-containing zeolite, even more preferably an iron-containing zeolite of the MFI, BEA, FER, MOR, FAU and / or MEL structural type.

9. The N ２ O decomposition catalyst and / or the N ２ O reduction catalyst and the NO Ｘ 9. The method of any one of claims 1 to 8, wherein the reduction catalysts each independently comprise a transition metal-containing zeolite, more preferably each comprises an iron-containing zeolite (Fe-zeolite), even more preferably comprising iron-containing zeolites of the same structural type, most preferably with the same external shape.

10. The N ２ O decomposition catalyst and the N ２ 10. The method of claim 1, wherein the O reduction catalysts are formed from the same material.

11. The N ２ O decomposition catalyst and the NO Ｘ 11. The method of any one of claims 1 to 10, wherein the reduction catalysts are formed from the same material.

12. The N ２ O reduction catalyst and the NO Ｘ 12. The method of any one of claims 1 to 11, wherein the reduction catalysts are formed from the same material.

13. The N ２ O decomposition catalyst, ２ O reduction catalyst, and the NO Ｘ 13. The method of any one of claims 1 to 12, wherein the reduction catalysts are formed from the same material.

14. NH in step (a) ３ 14. The method of claim 1, wherein the combustion of is not carried out over a catalyst.

15. NH ３ is H in step (a) ２ is burned in a mixture with NH ３ H in said mixture with ２ 15. The method according to claim 1 , wherein the proportion of is at most 80 mol %, more preferably at most 70 mol %, even more preferably at most 60 mol %, most preferably at most 50 mol %, in particular at most 40 mol %.

16. NH ３ is H in step (a) ２ is burned in a mixture with NH ３ H in said mixture with ２ is at least 10 mol%, more preferably at least 20 mol%, even more preferably at least 30 mol%, most preferably at least 40 mol%, in particular at least 50 mol%.

17. H in the mixture ２ :NH ３ 17. The process according to claim 15 or 16, wherein the molar ratio of is in the range of from 45:55 to 90:10, preferably from 50:50 to 85:15, more preferably from 55:45 to 80:20, even more preferably from 60:40 to 75:25, and most preferably from 65:35 to 70:

30.

18. 18. The method of any one of claims 1 to 17, wherein the air ratio λ is in the range of from 0.9 to 1.7, more preferably from 1.0 to 1.6, even more preferably from 1.1 to 1.5, and most preferably from 1.2 to 1.

4.

19. The firing system is ３ a combustion device for combusting NH ３ N ２ and H ２ NH for cracking ３ A method according to any one of claims 1 to 18, comprising:

20. The off-gas is the N ２ NO content greater than O content Ｘ Preferably, the NO Ｘ The content is the above-mentioned N ２ O content is at least 2 times, more preferably at least 3 times, even more preferably at least 4 times, most preferably at least 7 times, especially at least 10 times higher, preferably at least 2 times, more preferably at least 3 times, even more preferably at least 4 times, most preferably at least 7 times, especially at least 10 times higher than NO content. Ｘ :N ２ 20. The method of any one of claims 1 to 19, wherein the molar ratio of O to HCl is greater than 10:1, more preferably at least 20:1, even more preferably at least 30:1, most preferably at least 40:1, especially at least 50:

1.

21. The off-gas is the N ２ The NO content is greater than the O content, and preferably the NO content is greater than the N ２ 21. The method according to any one of claims 1 to 20, wherein the O content is at least 2 times, more preferably at least 3 times, even more preferably at least 4 times, most preferably at least 7 times, especially at least 10 times higher.

22. The off-gas is the N ２ NO content greater than O content ２ Preferably, the NO ２ The content is the above-mentioned N ２ 22. The method of any one of claims 1 to 21, wherein the O content is at least 2 times, more preferably at least 3 times, even more preferably at least 4 times, most preferably at least 7 times, especially at least 10 times higher.

23. The off-gas contains at least 10 ppmv, preferably at least 20 ppmv, more preferably at least 30 ppmv, even more preferably at least 40 ppmv, especially at least 50 ppmv of NO Ｘ 23. The method of any one of claims 1 to 22, having a content of

24. The off-gas contains at least 7 ppmv, preferably at least 100 ppmv, more preferably at least 150 ppmv, even more preferably at least 200 ppmv, especially at least 250 ppmv of NO Ｘ 24. The method of any one of claims 1 to 23, having a content of

25. The off-gas contains at least 500 ppmv, preferably at least 1000 ppmv, more preferably at least 2000 ppmv, even more preferably at least 3000 ppmv, especially at least 3500 ppmv of NO Ｘ 25. The method of any one of claims 1 to 24, having a content of

26. The off-gas contains at least 10 ppmv, preferably at least 20 ppmv, more preferably at least 30 ppmv, even more preferably at least 40 ppmv, especially at least 50 ppmv of N ２ 26. The method of any one of claims 1 to 25, having an O content.

27. The off-gas contains at least 75 ppmv, preferably at least 100 ppmv, more preferably at least 150 ppmv, even more preferably at least 200 ppmv, especially at least 250 ppmv of N ２ 27. The method of any one of claims 1 to 26, having an O content.

28. The off-gas contains more than 4.0 vol.%, preferably at least 5.0 vol.%, more preferably at least 6.0 vol.%, even more preferably at least 7.0 vol.%, most preferably at least 8.0 vol.%, especially at least 9.0 vol.% H ２ 28. The method of any one of claims 1 to 27, having an O content.

29. The off-gas contains at least 10% by volume, preferably at least 12% by volume, more preferably at least 14% by volume, even more preferably at least 16% by volume, most preferably at least 18% by volume, especially at least 20% by volume of H ２ 29. The method of any one of claims 1 to 28, having an O content.

30. The off-gas has a H content in the range of 10±8% by volume, preferably in the range of 10±7% by volume, more preferably in the range of 10±6% by volume, even more preferably in the range of 10±5% by volume, most preferably in the range of 10±4% by volume, especially in the range of 10±3% by volume. ２ 30. The method of any one of claims 1 to 29, having an O content.

31. The off-gas has a H content in the range of 15±8% by volume, preferably in the range of 15±7% by volume, more preferably in the range of 15±6% by volume, even more preferably in the range of 15±5% by volume, most preferably in the range of 15±4% by volume, especially in the range of 15±3% by volume. ２ 31. The method of any one of claims 1 to 30, having an O content.

32. The off-gas has a H content in the range of 20±8% by volume, preferably in the range of 20±7% by volume, more preferably in the range of 20±6% by volume, even more preferably in the range of 20±5% by volume, most preferably in the range of 20±4% by volume, and especially in the range of 20±3% by volume. ２ 32. The method of any one of claims 1 to 31, having an O content.

33. The off-gas has a H content in the range of 25±8% by volume, preferably in the range of 25±7% by volume, more preferably in the range of 25±6% by volume, even more preferably in the range of 25±5% by volume, most preferably in the range of 25±4% by volume, especially in the range of 25±3% by volume. ２ 33. The method of any one of claims 1 to 32, having an O content.

34. The off-gas has a H content in the range of 30±8% by volume, preferably in the range of 30±7% by volume, more preferably in the range of 30±6% by volume, even more preferably in the range of 30±5% by volume, most preferably in the range of 30±4% by volume, and especially in the range of 30±3% by volume. ２ 34. The method of any one of claims 1 to 33, having an O content.

35. The off-gas contains up to 95% by volume, preferably up to 90% by volume, more preferably up to 85% by volume, even more preferably up to 80% by volume, most preferably up to 75% by volume, especially up to 70% by volume of N ２ 35. The method of any one of claims 1 to 34, having a content of

36. The off-gas contains at least 40% by volume, preferably at least 50% by volume, more preferably at least 60% by volume, even more preferably at least 70% by volume, most preferably at least 80% by volume, especially at least 90% by volume of N ２ 36. The method of any one of claims 1 to 35, having a content of

37. The off-gas is preferably O ２ , CO, CO ２ , N.H. ３ , C.H. ４ 37. The method of any one of claims 1 to 36, comprising a further gaseous component selected from the group consisting of: and mixtures thereof.

38. 38. The method of any one of claims 1 to 37, wherein the off-gas exiting the calcination system, preferably the combustion device, is at a temperature of at least 500°C, more preferably at least 600°C, even more preferably at least 700°C, most preferably at least 800°C, especially at least 900°C.

39. 39. The method according to any one of claims 1 to 38, wherein the off-gas leaving the calcination system, preferably the combustion device, is at a temperature of at most 1100°C, more preferably at most 1000°C, even more preferably at most 900°C, most preferably at most 800°C, especially at most 700°C.

40. 40. The method of any one of claims 1 to 39, wherein the off-gas leaving the calcination system, preferably the combustion device, is at a pressure of up to 1.5 bar, preferably atmospheric pressure.

41. The off-gas leaving the calcination system, preferably the combustion device, contains at least 10%, more preferably at least 20%, even more preferably at least 30%, most preferably at least 40%, especially at least 50% NO Ｘ 41. The method of any one of claims 1 to 40, wherein the oxidation degree is

42. The off-gas leaving the calcination system, preferably the combustion device, contains up to 90%, more preferably up to 80%, even more preferably up to 70%, most preferably up to 60%, especially up to 50% NO Ｘ 42. The method of any one of claims 1 to 41, wherein the oxidation degree is

43. The off-gas exiting the calcination system, preferably the combustion device, is less than 2.0% by volume O ２ 43. The method of any one of claims 1 to 42, having a content of

44. The off-gas from the calcination system, preferably the combustion device, is greater than 4.0% by volume O ２ 44. The method of any one of claims 1 to 43, having a content of

45. 45. The method of any one of claims 1 to 44, wherein the off-gas entering the off-gas treatment system is at a temperature of at least 300°C, more preferably at least 350°C, even more preferably at least 400°C, most preferably at least 425°C, especially at least 450°C.

46. 46. ​​The method of any one of claims 1 to 45, wherein the off-gas entering the off-gas treatment system is at a temperature of at least 500°C, more preferably at least 550°C, even more preferably at least 600°C, most preferably at least 625°C, especially at least 650°C.

47. 47. The method of any one of claims 1 to 46, wherein the off-gas entering the off-gas treatment system is at a temperature of at most 825°C, more preferably at most 800°C, even more preferably at most 775°C, most preferably at most 750°C, especially at most 725°C.

48. 48. The method of any one of claims 1 to 47, wherein the off-gas entering the off-gas treatment system is at a temperature of at most 700°C, more preferably at most 650°C, even more preferably at most 600°C, most preferably at most 550°C, especially at most 500°C.

49. 49. The method of any one of claims 1 to 48, wherein the off-gas entering the off-gas treatment system is at a relatively lower temperature by at least 20°C, preferably at least 40°C, more preferably at least 60°C, even more preferably at least 80°C, most preferably at least 100°C, especially at least 120°C, than the temperature of the off-gas exiting the calcination system, preferably the combustion device.

50. 50. The method of any one of claims 1 to 49, wherein the off-gas entering the off-gas treatment system has a pressure of at most 1.4 bara, preferably at most 1.3 bara, more preferably at most 1.2 bara.

51. The off-gas entering the off-gas treatment system may contain up to 15%, more preferably up to 12.5%, even more preferably up to 10%, most preferably up to 7.5%, especially up to 5.0% NO Ｘ 51. The method of any one of claims 1 to 50, wherein the oxidation degree is

52. The off-gas entering the off-gas treatment system has less than 2.0% O ２ 52. The method of any one of claims 1 to 51, having a content of

53. The off-gas entering the off-gas treatment system has greater than 4.0% by volume O ２ 53. The method of any one of claims 1 to 52, having a content of

54. Step (d) is (d1) N ２ N via O decomposition catalyst ２ The N in the off-gas is removed by decomposition of O. ２ The present invention also includes reducing the O content, and preferably reducing the N ２ 54. The method of any one of claims 1 to 53, wherein the O decomposition catalyst comprises a zeolitic material, preferably a zeolite comprising a transition metal (including lanthanides), in particular iron, cobalt or copper, more preferably an iron-containing zeolite, even more preferably an iron-containing zeolite of the MFI, BEA, FER, MOR, FAU and / or MEL structural type.

55. Step (d) is ２ ) N ２ N by reducing agent via O reduction catalyst ２ The N in the off-gas is removed by chemical reduction of O. ２ The present invention also includes reducing the O content, and preferably reducing the N ２ 55. The method of any one of claims 1 to 54, wherein the O reduction catalyst comprises a zeolitic material, preferably a zeolite comprising a transition metal (including lanthanides), in particular iron, cobalt or copper, more preferably an iron-containing zeolite, even more preferably an iron-containing zeolite of structural type MFI, BEA, FER, MOR, FAU and / or MEL.

56. Step (d ２ ) wherein the reducing agent is NH ３ , hydrocarbons, CO, H ２ and mixtures thereof, preferably NH ３ 56. The method of any one of claims 1 to 55, wherein

57. Step (d ２ The reducing agent in ２ NH used in an amount of 0.5 to 2.0 molar parts, preferably 0.8 to 1.8 molar parts, based on the molar ratio of O ３ 57. The method of any one of claims 1 to 56, wherein

58. Step (d ２ The reducing agent in ２ 58. The method according to any one of claims 1 to 57, wherein the hydrocarbon or mixture of several hydrocarbons is preferably used in an amount of 0.2 to 1.0 molar part, more preferably 0.2 to 0.7 molar part, based on the molar ratio of O.

59. The above NO Ｘ 59. The method of any one of claims 1 to 58, wherein the reduction catalyst comprises a zeolitic material, preferably a zeolite comprising a transition metal (including lanthanides), in particular iron, cobalt or copper, more preferably an iron-containing zeolite, even more preferably an iron-containing zeolite of structural type MFI, BEA, FER, MOR, FAU and / or MEL.

60. The reducing agent in step (e) is NH ３ , hydrocarbons, CO, H ２ and mixtures thereof, preferably NH ３ 60. The method of any one of claims 1 to 59, wherein

61. The reducing agent in step (e) is NO to be chemically reduced. Ｘ NH used in an amount of 0.9 to 2.5 molar parts, preferably 1.0 to 1.4 molar parts, preferably 1.0 to 1.2 molar parts, based on the molar ratio of ３ 61. The method of any one of claims 1 to 60, wherein

62. Step (d ２ The reducing agent in step (e) is the same as the reducing agent in step (f), preferably NH ３ 62. The method of any one of claims 1 to 61, wherein

63. the off-gas treatment system comprising a first catalyst bed and a spatially separated second catalyst bed; the first catalyst bed is disposed upstream of the second catalyst bed in a flow direction of the off-gas; Optionally, NH ３ a first device with a first control valve for the metered addition of downstream of the first catalyst bed and upstream of the second catalyst bed, ３ A second device with a second control valve for the metered addition of further NH ３ is metered into the off-gas, both the first catalyst bed and the second catalyst bed each comprise an iron-containing zeolite catalyst; (i) in the first catalyst bed: (d １ ) N in the off-gas ２ The O content is ２ reduced by catalytic decomposition of O, and (e) NO in the off-gas Ｘ The content is NH ３ No by Ｘ is incompletely reduced by catalytic chemical reduction of NH ３ At least a part of the NH ３ caused by the incomplete combustion of (NH ３ slip) (ii) in the second catalyst bed: (d ２ ) residual N ２ O content is NH ３ by N ２ reduced by catalytic chemical reduction of O, (d1*) Residual N ２ The O content is ２ Optionally reduced by catalytic decomposition of O, and (e*) Residual NO Ｘ The content is NH ３ No by Ｘ is reduced by catalytic chemical reduction of 63. The method of any one of claims 1 to 62.

64. N in the first catalyst bed ２ The catalytic decomposition of NO present in the off-gas Ｘ 64. The method of claim 63, wherein the method is co-catalyzed by

65. NH in the first catalyst bed ３ No by Ｘ The incomplete chemical reduction of N in the first catalyst bed ２ A predetermined residual NO sufficient to provide a co-catalytic effect on the decomposition of O Ｘ 65. The method of claim 63 or 64, resulting in a content.

66. Additional NH ３ is metered into the off-gas by the first device, preferably under feedback control, to regulate NO 2 leaving the first catalyst bed. Ｘ A specific value in the concentration of NO is preferably defined as a target value (set value), and the NO leaving the first catalyst bed Ｘ 66. The method of any one of claims 63 to 65, wherein an actual concentration of is measured (actual value), and if there is a difference between a set value and the actual value (control difference), the output of the first control valve is changed to minimize said difference.

67. The additional NH ３ is the amount of NO leaving the first catalyst bed Ｘ 67. The method of claim 66, wherein the residual concentration of is selected to be at most 1000 ppmv, preferably at most 500 ppmv, more preferably at most 100 ppmv.

68. The additional NH ３ is the amount of NO leaving the first catalyst bed Ｘ 68. The method of claim 66 or 67, wherein the residual concentration of is selected to be at least 10 ppmv, preferably at least 20 ppmv, more preferably at least 40 ppmv.

69. residual N ２ and N O leaving said second catalyst bed of at most 20 ppmv, more preferably at most 10 ppmv, even more preferably at most 5 ppmv, and most preferably at most 2 ppmv. ２ 69. The method of any one of claims 63 to 68, wherein O is decomposed in the second catalyst bed to a residual concentration of O.

70. Residual NO Ｘ but NO leaving said second catalyst bed is at most 20 ppmv, more preferably at most 10 ppmv, even more preferably at most 5 ppmv, and most preferably at most 2 ppmv. Ｘ 70. The method of any one of claims 63 to 69, wherein the carbon monoxide is decomposed in the second catalyst bed to a residual concentration of

71. The further NH ３ is dispensed by the second device under feedforward control, and NO Ｘ and N ２ The concentration of O is preferably measured upon exiting the first catalyst bed, and NH ３ The amount of off-gas entering the second catalyst bed is taken into account to calculate the required amount of NH ３ 71. The method of any one of claims 63 to 70, wherein the method is used to vary the output of the second control valve to meter the required amount of

72. NH entering the second catalyst bed ３ / (NO Ｘ +N ２ 72. The process according to any one of claims 63 to 71, wherein the molar ratio of α- and β-hydroxybenzoates to α- and β-hydroxybenzoates is in the range of from 1.7 to 6.0, preferably from 2.1 to 4.6, more preferably from 2.7 to 3.

9.

73. NH entering the second catalyst bed ３ / NO Ｘ 73. The process according to any one of claims 63 to 72, wherein the molar ratio of is in the range of from 1.0 to 2.0, preferably from 1.1 to 1.6, more preferably from 1.2 to 1.

4.

74. NH entering the second catalyst bed ３ / N ２ 74. The method of any one of claims 63 to 73, wherein the molar ratio of O is in the range of from 0.7 to 4.0, preferably from 1.0 to 3.0, more preferably from 1.5 to 2.

5.

75. The further NH ３ 75. The method of any one of claims 63 to 74, wherein the first and second electrodes are not dispensed under feedback control by the second device.

76. The amount of catalyst is determined by the N ２ Based on the concentration of O, ２ 76. The process of any one of claims 63 to 75, wherein the decomposition of O is selected to be at least 50%, more preferably at least 70%, and even more preferably at least 80% in the first catalyst bed.

77. The amount of the catalyst and the additional NH ３ is the amount of NO upon exiting the first catalyst bed. Ｘ / N ２ 77. The method of any one of claims 63 to 76, wherein the molar ratio of O is selected to be at least 5, more preferably at least 10, even more preferably at least 20.

78. The space velocity of the first catalyst bed is 5000 h －１ From 100000h －１ , more preferably 10,000 h －１ From 50,000 hours －１ , and even more preferably 15000h －１ From 45,000 hours －１ 78. The method of any one of claims 63 to 77, wherein

79. NO exiting the first catalyst bed Ｘ / N ２ O molar ratio of at least 10, and further NH ３ The metered addition of Ｘ 79. The method of any one of claims 63 to 78, wherein the method is carried out only with respect to the amount of

80. 80. The method of any one of claims 63 to 79, wherein the temperature of the off-gas entering the first catalyst bed is at least 400°C, more preferably at least 425°C, even more preferably at least 450°C.

81. 81. The method of any one of claims 63 to 80, wherein the temperature of the off-gas entering the first catalyst bed is at most 550°C, more preferably at most 525°C, even more preferably at most 500°C.

82. 82. The method of any one of claims 63 to 81, wherein depending on the exothermicity of the chemical reactions taking place in the first and second catalyst beds, the inlet temperature of the off-gas to the first catalyst bed is selected such that the temperature of the off-gas leaving the second catalyst bed is at most 600°C, more preferably at most 550°C, even more preferably at most 520°C.

83. The space velocity of the second catalyst bed is 5000 h －１ From 100000h －１ , more preferably 10,000 h-1 to 50,000 h-1, and even more preferably 15,000 h －１ From 45,000 hours －１ 83. The method of any one of claims 63 to 82, wherein

84. the catalyst volume V of the second catalyst bed ２ｃａｔ the catalyst volume V1 of the first catalyst bed relative to ｃａｔ Catalyst volume ratio (V1 ｃａｔ / V2 ｃａｔ 84. The method of any one of claims 63 to 83, wherein the ratio of the hydroxyl group to the total weight of the polymer is in the range of 1 / 2 to 20 / 1, more preferably 1 / 2 to 10 / 1, and even more preferably 1 / 1 to 4 / 1.

85. The following conditions are met: the pressure of the off-gas entering the first catalyst bed is at most 5 bara, preferably at most 4 bara, more preferably at most 1.3 bara, most preferably at most 1.2 bara, in particular at most 1.1 bara; - H in the off-gas entering the first catalyst bed ２ the O content is at least 5% by volume, preferably at least 10% by volume, more preferably at least 15% by volume, most preferably at least 20% by volume, in particular at least 25% by volume; NO in the off-gas entering the first catalyst bed Ｘ the content is at least 500 ppmv, more preferably at least 1000 ppmv, even more preferably at least 1500 ppmv, most preferably at least 2000 ppmv, in particular at least 2500 ppmv; - N in the off-gas entering the first catalyst bed ２ the O content is less than maximum 500 ppmv, more preferably maximum 200 ppmv, even more preferably maximum 100 ppmv, but is at least 5 ppmv, preferably at least 10 ppmv, more preferably at least 50 ppmv; The off-gas entering the first catalyst bed is NH ３ NH from the combustion of ３ Contains unburned residue of; - the N ２ O decomposition catalyst and / or N ２ The O reduction catalyst is in the form of a honeycomb body; - the above NO Ｘ The reduction catalyst is in the form of a honeycomb body; - said first catalyst bed comprises an Fe zeolite; - the second catalyst bed comprises an Fe zeolite; - the off-gas passes through a heat exchanger in which it is heated before entering the first catalyst bed; - NO leaving the first catalyst bed Ｘ the content of which is at most 1000 ppmv, preferably at most 500 ppmv, more preferably at most 300 ppmv, most preferably at most 100 ppmv, but preferably at least 10 ppmv, more preferably at least 20 ppmv, more preferably at least 40 ppmv, most preferably at least 100 ppmv, in particular at least 250 ppmv; - N leaving the first catalyst bed ２ the content of O is at most 20 ppmv, more preferably at most 15 ppmv, even more preferably at most 10 ppmv, most preferably at most 5 ppmv, in particular at most 2 ppmv; - there is no intermediate cooling of the off-gas between leaving the first catalyst bed and entering the second catalyst bed; - N upon entering the first catalyst bed ２ O: NO Ｘ is at most 0.5, more preferably at most 0.2, even more preferably at most 0.1; N on exit from the first catalyst bed ２ O: NO Ｘ is at most 0.20, more preferably at most 0.1, even more preferably at most 0.05; NH into the off-gas upstream of the first catalyst bed in the flow direction of the off-gas ３ is optionally present, and if present, the feed is preferably NO entering said first catalyst bed. Ｘ and / or NH into the off-gas downstream of the first catalyst bed and upstream of the second catalyst bed in the flow direction of the off-gas ３ The feed of NO entering the second catalyst bed Ｘ and N ２ essential to the total content of O, and preferably superstoichiometric; 85. The method of any one of claims 63 to 84, wherein at least one, more than one, or all of the following are satisfied:

86. The N ２ O decomposition catalyst and / or the N ２ O reduction catalyst and the NO Ｘ 86. A method according to any one of claims 1 to 85, wherein the reduction catalyst is in the form of individual monolithic catalytic elements permeated with parallel channels, preferably in the form of a monolithic honeycomb body.

87. The off-gas exits the off-gas treatment system with a residual NO of at most 20 ppmv, preferably at most 15 ppmv, more preferably at most 10 ppmv, even more preferably at most 7.5 ppmv, most preferably at most 5.0 ppmv, especially at most 2.5 ppmv. Ｘ 87. The method of any one of claims 1 to 86, having a content of

88. The off-gas exits the off-gas treatment system with a residual N content of at most 20 ppmv, preferably at most 15 ppmv, more preferably at most 10 ppmv, even more preferably at most 7.5 ppmv, most preferably at most 5.0 ppmv, especially at most 2.5 ppmv. ２ 88. The method of any one of claims 1 to 87, having an O content.

89. The off-gas is cooled in the at least one heat exchanger in step (f) by the release of heat from the off-gas to a heat transfer medium, preferably water, steam, combustion air, NH ３ and combinations thereof.

90. In step (f), the off-gas is treated by a first off-gas / H 2 treatment system disposed downstream of the off-gas treatment system in the flow direction of the off-gas. ２ 90. The method of any one of claims 1 to 89, wherein the mixture is cooled in a heat exchanger.

91. 91. The method of any one of claims 1 to 90, wherein in step (f) the off-gas is cooled in a first off-gas / combustion air heat exchanger positioned downstream of the off-gas treatment system in a flow direction of the off-gas.

92. The off-gas is subjected in step (f) to a first off-gas / H 2 treatment system disposed downstream of the off-gas treatment system in the flow direction of the off-gas; ２ In the heat exchanger, and Also downstream of the off-gas treatment system in the flow direction of the off-gas, preferably the first off-gas / H ２ in a first off-gas / combustion air heat exchanger disposed downstream of the O heat exchanger, 92. The method of any one of claims 1 to 91, wherein the process is cooled.

93. The off-gas is subjected in step (f) to in a first off-gas / combustion air heat exchanger arranged downstream of the off-gas treatment system in the flow direction of the off-gas, and in a second off-gas / combustion air heat exchanger arranged downstream of the first off-gas / combustion air heat exchanger in the flow direction of the off-gas, 93. The method of any one of claims 1 to 92, wherein the process is cooled.

94. The off-gas is subjected in step (f) to in a first off-gas / combustion air heat exchanger arranged downstream of the off-gas treatment system in the flow direction of the off-gas, a first offgas / H 2 exchanger arranged downstream of the first offgas / combustion air heat exchanger in the flow direction of the offgas; ２ In the heat exchanger, and - the first off-gas / H in the flow direction of the off-gas ２ in a second off-gas / combustion air heat exchanger located downstream of the O heat exchanger, 5. The method of claim 1, wherein the process is cooled.

95. In step (f), the off-gas is passed through a heat exchanger downstream of the off-gas treatment system in the flow direction of the off-gas, preferably the first off-gas / combustion air heat exchanger, the first off-gas / H ２ 95. The method of any one of claims 1 to 94, wherein the off-gas is cooled in an O heat exchanger, and / or at least one off-gas / combustion gas heat exchanger located downstream of the second off-gas / combustion air heat exchanger.

96. In step (f), the off-gas is passed through a heat exchanger downstream of the off-gas treatment system in the flow direction of the off-gas, preferably the first off-gas / combustion air heat exchanger, the first off-gas / H ２ 96. The method of any one of claims 1 to 95, wherein the off-gas is cooled in an O heat exchanger, and / or at least one off-gas / combustion gas heat exchanger located downstream of the second off-gas / combustion air heat exchanger.

97. In step (f), the off-gas is passed through a heat exchanger downstream of the off-gas treatment system in the flow direction of the off-gas, preferably the first off-gas / combustion air heat exchanger, the first off-gas / H ２ and / or at least one second off-gas / H O heat exchanger arranged downstream of the second off-gas / combustion air heat exchanger. ２ 97. The method of any one of claims 1 to 96, wherein the mixture is cooled in a heat exchanger.

98. The off-gas is then passed through step (f) of the method. in a first off-gas / combustion air heat exchanger arranged downstream of the off-gas treatment system in the flow direction of the off-gas, a first offgas / H 2 exchanger arranged downstream of the first offgas / combustion air heat exchanger in the flow direction of the offgas; ２ In the heat exchanger, - the first off-gas / H in the flow direction of the off-gas ２ in a second off-gas / combustion air heat exchanger located downstream of the O heat exchanger; and in an off-gas / combustion gas heat exchanger arranged downstream of the second off-gas / combustion air heat exchanger in the flow direction of the off-gas, 5. The method of claim 1, wherein the process is cooled.

99. The off-gas is subjected in step (f) to in a first off-gas / combustion air heat exchanger arranged downstream of the off-gas treatment system in the flow direction of the off-gas, a first offgas / H 2 exchanger arranged downstream of the first offgas / combustion air heat exchanger in the flow direction of the offgas; ２ In the heat exchanger, - the first off-gas / H in the flow direction of the off-gas ２ in a second off-gas / combustion air heat exchanger located downstream of the O heat exchanger, a second off-gas / H 2 exchanger arranged downstream of the second off-gas / combustion air heat exchanger in the flow direction of the off-gas; ２ In the heat exchanger, 5. The method of claim 1, wherein the process is cooled.

100. The off-gas is subjected in step (f) to in a first off-gas / combustion air heat exchanger arranged downstream of the off-gas treatment system in the flow direction of the off-gas, a first offgas / H 2 exchanger arranged downstream of the first offgas / combustion air heat exchanger in the flow direction of the offgas; ２ In the heat exchanger, - the first off-gas / H in the flow direction of the off-gas ２ in a second off-gas / combustion air heat exchanger located downstream of the O heat exchanger, in an off-gas / combustion gas heat exchanger arranged downstream of the second off-gas / combustion air heat exchanger in the flow direction of the off-gas, a second offgas / H 2 exchanger arranged downstream of the offgas / combustion gas heat exchanger in the flow direction of the offgas; ２ In the heat exchanger, 5. The method of claim 1, wherein the process is cooled.

101. (i) Preferably, NH ３ a combustion device for the combustion of NH ３ N ２ and H ２ NH for cracking ３ and a decomposition device. ３ an actuated firing system; (ii) an off-gas treatment system; and An apparatus comprising: The apparatus is configured to perform the method of any one of claims 1 to 100. Device.

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