Reduction of NOx and N2O in exhaust gases from firing systems, especially gas turbines, operated with NH3

Abstract

The present invention relates to a method for reducing NO in the exhaust gas of a combustion system operated using NH3, particularly a gas turbine operated using NH3. X and reduction of N2O content.

Description

[Technical Field]

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

[0002] The present invention relates to the reduction of NO in the off-gas from an NH3-driven combustion system, particularly an NH3-driven gas turbine. X and reduction of N2O content. [Background technology]

[0003] Ammonia is one of the most widely produced and distributed chemicals worldwide, best known for its use as a fertilizer in agriculture. Recently, interest in its potential use as a high-quality energy source and as a carbon-free fuel for internal combustion engines has grown (H. Kobayashi et al., Proceedings of the Combustion Institute 37 (2019) 109-133; D. Erdemir et al., Int J. Energy Res. 2021, 45, 4827-4834; C. Tornatore et al., Frontiers in Mechanical Engineering 2022, 8, Article 944291). Its use in aircraft has also been discussed (A. Boretti et al., ACS Energy Lett. 2022, 7, 2557-2564).

[0004] Ammonia is carbon-free, has a global transportation and storage infrastructure, can be produced directly from renewable electricity, water, and air, and is therefore currently considered an intelligent energy source and combustion fuel.

[0005] Ammonia has a relatively low calorific value and a low flame propagation speed, which poses the risk of flame quenching and incomplete combustion. Furthermore, the combustion of NH3 poses the risk of increased emissions of nitrogen oxides (especially NO, NO2, and NO), which impacts its suitability as a combustion gas. There have been proposals for gaseous ammonia / hydrogen / air mixtures in which a certain hydrogen content is used as a combustion promoter, which can be produced, for example, by catalytic or thermally assisted NH3 dissociation (Ch. Lhuillier et al., 14th International Conference on Engines & Vehicles, 2019, Capri; S. Mashruk et al., Chemical Engineering Transactions, 89, 2021; S. Mashruk et al., Combustion and Flame 244 (2022) 112299).

[0006] WO 2011 / 136034 describes the use of NH3 and NO in the off-gas. X and an off-gas treatment catalyst capable of treating NO in the off-gas flowing into the off-gas treatment catalyst. X and a flow gas control unit capable of controlling the ratio of NH3 to CO2.

[0007] EP 2378097 relates to an ammonia-driven machine, and a NO gas supply for selective reduction is arranged in the off-gas duct of the machine. X The catalyst reacts with NO present in the off-gas in the presence of ammonia. X can be selectively reduced.

[0008] EP 3517757 A1 relates to a gas turbine that can be fired with NH3 and / or H2 and is equipped with an off-gas treatment system.

[0009] EP 3604929 relates to a combustion device for a gas turbine (A) having a combustion chamber, an ammonia supply unit that supplies primary reduced ammonia to the combustion chamber as a nitrogen oxide reducing agent and mixes the secondary reduced ammonia with the combustion off-gas discharged from the combustion chamber in order to reduce nitric oxide present in the combustion off-gas, and a control unit designed to control at least one of the amount of primary reduced ammonia to be supplied and the amount of the secondary reduced ammonia to be mixed with the combustion off-gas according to the concentrations of residual nitric oxide and residual ammonia present in the combustion off-gas after being discharged from the combustion chamber.

[0010] US Patent No. 11702988 relates to an ammonia decomposition plant including a heating medium conduit configured for a flow of a heat medium heated by heat generated by a gas turbine, an ammonia supply conduit configured for a flow of an ammonia, an ammonia decomposition unit, and an ammonia remover. The ammonia decomposition unit is configured to utilize heat from the heating medium from the heating medium conduit to thermally decompose ammonia from the ammonia supply conduit and produce a cracked gas containing hydrogen, nitrogen, and residual ammonia.

[0011] US 2018 / 0355794 relates to a gas turbine system having an ammonia source and an oxygen gas source, a first combustion chamber connected to receive the ammonia, a hydrogen-rich gas stream and the oxygen gas, a turbine connected to absorb an off-gas stream from the first combustion chamber, and a second combustion chamber connected to receive the off-gas, ammonia and the hydrogen-rich gas stream from the turbine.

[0012] WO 2023 / 286516 relates to a gas turbine plant including an ammonia supply device for supplying ammonia to a combustion chamber of a gas turbine, a frame forming a flow channel that forms an off-gas flow duct through which off-gas from the gas turbine flows, a water spray device including a water sprayer capable of spraying water into the off-gas flow duct, and a water spray controller for controlling the operation of the water spray device.

[0013] CD Avila et al., Applications in Energy and Combustion Science 13(2023)100104, concerns an experimental evaluation of the performance of a commercial microscale gas turbine operated on an ammonia-methane mixture.

[0014] L. Balling, Stationare Gasturbinen [Stationary Gas Turbines], Springer, VDI-Buch (2019) 31-65 relates to gas turbine power plants.

[0015] Th. Sattelmayer, Stationare Gasturbinen, Springer, VDI-Buch (2019) 241-272, relates to the principles of combustion in stationary gas turbines.

[0016] S. Mashruk et al., Combustion and Flame 244 (2022) 112299, is concerned with the development of N2O production in lean combustion in premixed NH3 / H2 / air vortex flames.

[0017] ECOkafor et al., Combustion and Flame 211 (2020) 406-416, reported NO emissions in a microscale gas turbine burner fired with methane-ammonia mixtures. X and the control of other emissions.

[0018] M. Zhang et al., Int. Journal of Hydrogen Energy 46 (2021) 21013-21025, concerns the conditioning effect of methane and hydrogen on emission characteristics.

[0019] The operating limits of an ammonia-fueled spark-ignition engine have been investigated. Here, it was found that NH3 emissions in the off-gas decrease with increasing engine speed, with the highest values ​​being achieved at rich mixtures. NH3 emissions can reach up to 1% by volume. NOX The emissions consist mainly of NO, and the effect of engine speed appears to depend on the equivalence ratio. NH3 does not produce carbon content in the exhaust, but it can release N2O, one of the most potent greenhouse gases. NO X For both NH3 and NO, the highest emissions were observed on the lean side and decreased with increasing equivalence ratio. Finally, even when pure ammonia was burned under rich conditions, H2 was produced in the off-gas, suggesting local decomposition of ammonia. Off-gas temperature was also monitored, and NH3 and NO were observed at least below 2000 rpm. X To reduce both NO emissions X This appears to be high enough to use catalysts for selective catalytic reduction (SCR) of CO₂ (Ch. Mounaim-Rousselle et al., Energies 2021, 14, 4141).

[0020] CN Patent No. 114412668 relates to an ammonia-fueled engine, in particular an ammonia-hydrogen fusion hybrid energy system and engine.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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). Passage through specific catalysts, for example, based on TiO2, for the hydrolysis of HCN via HCN + HO → CO + NH3 has also been described. Subsequent further oxidation over a corresponding separate oxidation catalyst is also required in this case. Therefore, there is a need for a cleaning 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.

[0027] A further problem is the incomplete combustion of ammonia, which has the effect that the off-gas from a calcination system operating on ammonia as fuel may contain a significant amount of unburned ammonia (called NH3 slip, NH3 breakthrough). Since the allowable limits for ammonia that can be released into the atmosphere are relatively strict, 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 do not convert NH3 to NO Xor N2O), susceptible to chlorine compounds and other catalyst poisons.

[0028] Therefore, it is or may be present for combustion-related reasons in the off-gas of an NH3-driven firing system, in particular an NH3-driven internal combustion engine, an NH3-driven gas turbine, or a furnace for cracking NH3 to N2 and H2, 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 any other environmentally harmful components of the off-gas (e.g. CO or HCN), What is needed is a means by which this can be at least partially eliminated.

[0029] Here, it is necessary to take into account the specific circumstances resulting from the maximum efficiency of the combustion of NH3 for the operation of the calcination system, preferably for driving an internal combustion engine, for driving a gas turbine or for driving a furnace for cracking NH3 to N2 and H2. 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.

[0030] 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 1000kJ / s. 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 is to produce NO X The goal is to achieve maximum yield of . The typical water content in the off-gas ranges from about 1% to 3% by volume.

[0031] In contrast, in the combustion of NH3 for the operation of a calcination system, preferably for the operation of an internal combustion engine, for the operation of a gas turbine, or for the operation of a furnace for cracking NH3 to N2 and H2, NH3 is preferably oxidized only to the level of N2, so that typically no catalyst is required, and this conversion usually takes place at atmospheric pressure. X and achieve a minimum yield of NO. Typical water contents in the off-gas are 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 here is the generation of energy. 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 regarding allowable emissions, or because only then can sufficiently low residual concentrations be achieved by known nitrogen oxide reduction methods.

[0032] 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, offers special features accompanied by special measures.

[0033] On the one hand, a relatively low pressure, typically below 5 bar, and on the other hand, a very high water content are essential. By "low 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, a 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.

[0034] 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, a small proportion of 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.

[0035] 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.

[0036] 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.

[0037] Therefore, the goals and resulting reaction products in the combustion of NH3 can be very different from one another.

[0038] 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.

[0039] In contrast, in combustion plants, preferably for driving combustion engines, for driving gas turbines, or for operating furnaces for splitting NH3 into N2 and H2, the off-gas is often at a relatively low pressure, -Relatively high content of NO X , - a relatively small proportion of NO2, - relatively low content of N2O, - a significantly high content of water, - possibly a non-negligible proportion of unburned NH3 (NH3 slip), and -If NH3 is combusted with CH4 (natural gas), possibly a non-negligible proportion of HCN, It has.

[0040] These special circumstances can cause NO from the off-gassing X and N2O removal, which constitutes a particular challenge.

[0041] NO from off-gas compared to existing industrial plants, so-called stationary plants X Further challenges in the removal of NO and NO arise from the use of NH3-operated calcination systems, particularly NH3-driven internal combustion engines, in vehicles, ships, and possibly aircraft. Therefore, the systems are mobile rather than being fixedly installed and operated in one location. However, special requirements are imposed on mobile systems, e.g., regarding weight, size, safety, shock stability, etc. Furthermore, the operating mode of the calcination system, preferably the internal combustion engine, can spontaneously change, e.g., when switching from partial load operation to full load operation in the case of rapid acceleration or braking. This also results in the removal of NO from the off-gas. X and constitute a particular challenge in the removal of N2O. [Prior art documents] [Patent documents]

[0042] [Patent Document 1] International Publication No. 2011 / 136034 Brochure [Patent Document 2] European Patent No. 2378097 [Patent Document 3] European Patent Application Publication No. 3517757 [Patent Document 4] European Patent No. 3604929 [Patent Document 5] U.S. Patent No. 1,1702,988 [Patent Document 6] US Patent No. 2018 / 0355794 [Patent Document 7] International Publication No. 2023 / 286516 Brochure [Patent Document 8] Japanese Patent Publication No. 2023-026798 [Patent Document 9] US Patent Application Publication No. 2003 / 0143142 [Patent Document 10] US Patent Application Publication No. 2017 / 0334722 [Non-patent literature]

[0043] [Non-Patent Document 1] H.Kobayashi et al., Proceedings of the Combustion Institute 37(2019)109-133;D.Erdemir et al.,Int J.Energy Res.2021,45,4827-4834;C.Tornatore et al.,Frontiers in Mechanical Engineering,2022,8,Article 944291 [Non-patent document 2] A. Boretti et al., ACS Energy Lett.2022,7,2557-2564 [Non-patent document 3] Ch.Lhuillier et al., 14th International Conference on Engines&Vehicles,2019,Capri;S.Mashruk et al.,Chemical Engineering Transactions,89,2021;S.Mashruk et al.,Combustion and Flame 244(2022)112299 [Non-patent document 4] CDAvila et al., Applications in Energy and Combustion Science 132023)100104 [Non-Patent Document 5] L. Balling, Stationare Gasturbinen [Stationary Gas Turbines], Springer, VDI-Buch (2019) 31-65 [Non-patent document 6] Th.Sattelmayer,Stationare Gasturbinen,Springer,VDI-Buch(2019)241-272 [Non-Patent Document 7] S. Mashruk et al., Combustion and Flame 244(2022)112299 [Non-patent document 8] ECOkafor et al., Combustion and Flame 211 (2020) 406-416 [Non-Patent Document 9] M. Zhang et al., Int. Journal of Hydrogen Energy 46(2021)21013-21025 [Non-Patent Document 10] Ch. Mounaim-Rousselle et al., Energies 2021,14,4141 [Non-Patent Document 11] Y.K. Park, Chemical Engineering Journal, Vol. 461, 141958 Summary of the Invention

[0044] The object of the present invention is to provide a method for the reduction of NO in the off-gas obtained in an NH3-operated combustion system, preferably an NH3-driven internal combustion engine, an NH3-driven gas turbine, or a furnace for cracking NH3 to N2 and H2. X (i.e., NO and NO2), N2O, and optionally NH3, CO and / or HCN content.

[0045] This object is achieved by the subject matter of the claims.

[0046] A first aspect of the present invention is directed to the use of NO in the off-gas of an NH3-powered combustion system, preferably an NH3-driven internal combustion engine, an NH3-driven gas turbine, or a furnace for cracking NH3 into N2 and H2. X and a method for reducing the content of N2O, the method comprising: (a) Combustion of NH3 (or NH3 mixed with further combustible gases, in particular H2, CH4, etc.) for the operation of a calcination system, preferably for driving an internal combustion engine, for driving a gas turbine, or for driving a furnace for cracking NH3 to N2 and H2, producing N2, HO, NOX generating an off-gas exiting the firing system, preferably an internal combustion engine, a gas turbine or a furnace, comprising NO and optionally HCN; (b) transferring off-gas from the firing system, preferably an internal combustion engine, gas turbine, or furnace, to an off-gas treatment system; (c) The NO content in the off-gas is (c1) decomposing N2O via an N2O decomposition catalyst; and / or (c2) Chemical reduction of N2O using a reducing agent via an N2O reduction catalyst and reducing by (d)NO X NO by reducing agents via reduction catalysts X NO in the off-gas by chemical reduction of X Reducing the content; Includes:

[0047] The order of steps (c) and (d) 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.

[0048] 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.

[0049] 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:

[0050] In a preferred embodiment, the off-gas treatment system of the present invention further comprises at least one additional catalyst, or 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:

[0051] The NH3 oxidation catalyst preferably reduces the proportion of unburned NH3 in the off-gas (NH3 slip) to a level that is lower than the NO2 content in the off-gas treatment system. X and / or 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 (c1) and / or (c2) and (d), 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.

[0052] 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 resulting HCN can then be decomposed (removed) using the HCN decomposition catalyst by hydrolysis of HCN and oxidation of the hydrolysis products (hydrolysates) formed during the process, namely NH3 and CO, preferably NO. X and N2O are present in the off-gas.

[0053] 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).

[0054] 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 X In 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] For illustrative purposes, "NO X " includes nitric oxide (NO) and nitrogen dioxide (NO2), but does not include nitrous oxide (N2O).

[0059] Catalysts speed up certain chemical reactions by lowering their activation energy.

[0060] 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.

[0061] Steps (a) and (b) of the method of the present invention are performed consecutively in alphabetical order, followed by steps (c) and (d) in essentially any order. Thus, step (c) can be performed before or after step (d), or simultaneously with step (d). A partially simultaneous mixed mode 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 reach a higher conversion rate than a second reaction proceeding in parallel.

[0062] Steps (c1) and (c2) are considered separately for purposes of explanation, but both serve a common purpose of reducing the N2O content in the off-gas.

[0063] Steps (c1), (c2) and (d) may likewise be performed in any order, although partial simultaneity and hybridization are also possible in this regard.

[0064] In a preferred embodiment, the method of the present invention comprises steps (a), (b), (c1) and (d), steps (a), (b), (c2) and (d), or steps (a), (b), (c1), (c2) and (d).

[0065] In a preferred embodiment, the off-gas undergoes the steps of the method of the present invention in one of the following orders:

[0066] (i)(a) →(b) →(c1) →(d); (ii) (a) → (b) → (d) → (c2); (iii)(a)→(b)→(d)→(c2)→(c1); (iv) (a) → (b) → (d) → (c1 + c2) or (v)(a) →(b) →(d) →(c1). By (c1+c2) it is meant that both step (c1) and step (c2) are performed, but the execution of these two steps (c1) and (c2) is at least partially simultaneous, i.e. both steps proceed in parallel.

[0067] Between these steps there may be further steps not explicitly specified.

[0068] In step (a) of the method of the present invention, combustion of NH3 is carried out for the operation of the calcination system.

[0069] A "calcination system" in the context of the present invention generates heat through a combustion process. Combustion of a fuel generates heat. Optionally, it is also possible here to generate power and / or drive machinery. This term encompasses a wide range of different systems, such as domestic heating, motors for driving vehicles, industrial calcination systems for steam and process heat generation, large-scale power plant calcination systems, etc. A "calcination system" in the context of the present invention is any system in which NH3 is oxidized with O2 (preferably from air) with the aim of producing N2 and HO as the main products, in particular. The oxidation of NH3 with O2 (preferably from air) to a higher oxidation number (e.g., NO2), as in the production of nitric acid, is also possible. X Systems in which NH3 is oxidized with O2 to produce nitrogen compounds having the formula (I) as the primary product are not calcination systems within the context of this invention.

[0070] 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.

[0071] According to the present invention, NH3 is preferably combusted in a mixture with H2 or a fossil fuel, such as CH4.

[0072] In a preferred embodiment, in step (a) of the method of the present invention, combustion of NH3 is carried out to drive an internal combustion engine.

[0073] An "internal combustion engine" (heat engine) within the context of the present invention is in particular a combustion engine, preferably a piston heat engine having an internal combustion engine such as a reciprocating piston engine or a rotary piston engine.

[0074] In a preferred embodiment, step (a) of the method of the present invention involves the combustion of NH3 to drive a gas turbine.

[0075] A "gas turbine" in the context of the present invention is in particular an internal combustion engine in which an off-gas stream is produced which can be used to generate (mechanical) rotational energy, for example by means of an off-gas expansion turbine.

[0076] Surprisingly, it has been found that the method of the present invention is particularly suitable for gas turbines and has several advantages over conventional methods. For example, the method of the present invention is characterized by lower air volume requirements and simplified gas turbine operation. Furthermore, NO and NO X This ensures a high decomposition rate of N2O and NO, in addition to which the consumption of reducing agents (especially NH3) is low. X Emissions of can be reduced in off-gas treatment systems, especially if the off-gas treatment plant is equipped with two series-connected catalyst beds. The advantages of "end-of-pipe technology" become apparent: the catalysts used are non-toxic and have a long lifespan; pressure drops are low; and the catalysts and methods can be used over a wide temperature range.

[0077] In this context, it is relevant that modern gas turbines have turbine inlet temperatures exceeding 1500°C and therefore off-gas temperatures exceeding 600°C. Conventional SCR catalysts based on vanadium oxide cannot be used at temperatures above 400°C due to irreversible damage. In contrast, the zeolite catalysts preferred according to the invention can be used within a wide temperature range from about 350 to 600°C, and therefore even at higher temperatures. Therefore, according to the invention, it may be possible to dispense with complex cooling of the off-gas.

[0078] In a preferred embodiment, in step (a) of the method of the present invention, NH3 is combusted to operate a furnace to crack NH3 into N2 and H2.

[0079] In step (b) of the inventive method, the off-gas is transferred to an off-gas treatment system, i.e., from an internal combustion engine or a gas turbine. Steps (c) and (d) of the inventive method are carried out in the inventive off-gas treatment system. For this purpose, the off-gas treatment system contains an N2O decomposition catalyst for step (c1) and / or an N2O reduction catalyst for step (c2), and an NO2O reduction catalyst for step (d). X and a reduction catalyst.

[0080] The off-gas treatment system of the present invention may further comprise at least one additional catalyst, or may be used to treat N2O reduction, N2O decomposition, or NO X If one of the reduction catalysts fulfills at least one further functionality, at least one of the following steps (e1) to (e4) is preferably further carried out in the off-gas treatment system of the present invention.

[0081] (e1) cooling the off-gas in at least one heat exchanger, preferably arranged in the off-gas treatment system, preferably arranged upstream of the NH3 oxidation catalyst in the flow direction of the off-gas; (e2) 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; (e3) Reducing the HCN content in the off-gas by hydrolysis and oxidation of the hydrolysate with an oxidizing agent via an HCN decomposition catalyst, wherein the oxidizing agent is preferably NO X and / or N2O, and (e4) Reducing the CO content in the off-gas by chemical oxidation with an oxidant via a CO oxidation catalyst, the oxidant preferably comprising O2.

[0082] In step (c) of the method of the present invention, the NO content in the off-gas is reduced, which can be achieved by (c1) decomposition of NO via an NO decomposition catalyst and / or (c2) chemical reduction of NO with a reducing agent via an NO reduction catalyst.

[0083] The decomposition of N2O forms N2 and O2 according to the following empirical reaction:

[0084] 2 N2O → 2 N2 + 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.

[0085] Chemical reduction of N2O by reducing agents forms different reaction products depending on the reducing agent.

[0086] 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:

[0087] 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:

[0088] (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:

[0089] N2O+CO→N2+CO2.

[0090] 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.

[0091] In step (d) 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

[0092] 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 XThis 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.

[0093] 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:

[0094] 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).

[0095] A typical selective catalytic reduction is called fast SCR and is much faster than regular SCR or NO2 SCR.

[0096] 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 and / or chemically reducing NO and / or NO X It is quite possible, and indeed preferred, that further reactions can be further catalyzed, such as the establishment of an equilibrium or the selective oxidation of excess NH by free O. 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.

[0097] 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.

[0098] 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).

[0099] 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.

[0100] 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.

[0101] 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.

[0102] 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.

[0103] 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.

[0104] 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.

[0105] 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.

[0106] The NO decomposition catalysts can be in the form of shaped bodies of any size and geometry, preferably with a high surface area to volume ratio, which traverses them to generate a minimum pressure drop. All geometries known in catalysis are typical, such as cylinders, hollow cylinders, perforated cylinders, rings, crushed granules, trilobes, or honeycomb structures.

[0107] 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.

[0108] 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.

[0109] 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.

[0110] 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.

[0111] Furthermore, the catalysts used according to the invention may contain further additives known to those skilled in the art, such as binders.

[0112] 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%.

[0113] 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.

[0114] 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.

[0115] 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).

[0116] In a preferred embodiment, the N2O decomposition catalyst and the N2O reduction catalyst are formed from the same material.

[0117] In a preferred embodiment, the NO decomposition catalyst and NO X The reduction catalyst is formed from the same material.

[0118] In a preferred embodiment, an N2O reduction catalyst and an NOX The reduction catalyst is formed from the same material.

[0119] 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.

[0120] 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.

[0121] 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.

[0122] 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 structure 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.

[0123] 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.

[0124] 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 with 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.

[0125] 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.

[0126] 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.

[0127] 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.

[0128] 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.

[0129] 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.

[0130] 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.

[0131] 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.

[0132] 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.

[0133] 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.

[0134] 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.

[0135] 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.

[0136] 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.

[0137] 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.

[0138] NH3 oxidation catalyst NH3 oxidation catalysts are known to those skilled in the art.

[0139] The NH3 oxidation catalyst is preferably free of platinum group metals, and preferably free of precious metals.

[0140] 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.

[0141] 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).

[0142] 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".

[0143] 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:

[0144] 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.

[0145] 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.

[0146] 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.

[0147] 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.

[0148] 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.

[0149] 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.

[0150] Suitable methods known to those skilled in the art, such as liquid-phase or solid-state ion exchange, allow the targeted exchange of cations present in zeolites, such as NH4+, with other cations, such as iron or copper ions (J. Weitkamp, ​​L. Puppe, Catalysis and Zeolites - Fundamental and Applications, Springer-Verlag Berlin Heidelberg New York, 1999 or Kucherov, A.V. Slinkin, 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). The so-called exchange level is 100% when all negative charges generated by the AlO2 units are compensated by cations.

[0151] 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.

[0152] 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)).

[0153] 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%.

[0154] 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%.

[0155] 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%.

[0156] 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.

[0157] 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.

[0158] In a preferred embodiment, the NH3 oxidation catalyst and the N2O decomposition catalyst are formed from the same material.

[0159] In a preferred embodiment, the NH3 oxidation catalyst and the N2O reduction catalyst are formed from the same material.

[0160] In a preferred embodiment, an NH3 oxidation catalyst and NO X The reduction catalyst is formed from the same material.

[0161] In a preferred embodiment, NH3 oxidation catalyst, NO X The reduction catalyst and the N2O decomposition catalyst are formed from the same material.

[0162] Step (a): In step (a) of the method of the present invention, NH3 is combusted to operate a calcination system, preferably to drive an internal combustion engine, a gas turbine, or a furnace for cracking NH3 into N2 and H2. The combustion produces N2, H2O, NO X and NO. The off-gas exits the firing system, preferably an internal combustion engine, a gas turbine or a furnace, and is then fed to step (b) of the method of the present invention.

[0163] In step (a) or in an internal combustion engine constructed according to the present invention, the combustion of NH, i.e., the oxidation of NH with O (or a mixture of NH with a further combustible gas, e.g., H, CH, etc.), is preferably not carried out via a catalyst, i.e., the combustion is not carried out in the presence of a heterogeneous catalyst.

[0164] In a preferred embodiment, NH3 is combusted in step (a) in a mixture with one or more further combustible gases, which means that both NH3 and the at least one further combustible gas are oxidized with O2.

[0165] In a preferred embodiment, the further combustible gas is a fossil fuel.

[0166] In a preferred embodiment, the further combustible gas is selected from hydrocarbons and hydrocarbon mixtures, preferably methane, ethane, propane, butane, natural gas, gasoline and / or diesel.

[0167] In a preferred embodiment, the further combustible gas is selected from alcohols, preferably methanol and / or ethanol.

[0168] In another preferred embodiment, the further combustible gas is H2.

[0169] More preferably, the further combustible gas is H formed by thermal and / or catalytic cracking of NH. Preferably, it is the combined combustion of NH and O that provides the energy for cracking. Thus, preferably, in step (a), the combustion of NH is integrated into the process for thermal and / or catalytic cracking of NH to N and H.

[0170] In a preferred embodiment, NH3 is combusted in step (a) to drive a gas turbine in combination with a steam turbine.

[0171] Combustion in gas turbines is preferably carried out using air or oxygen as a single stage combustion of (i) pure NH3, (ii) a mixture containing NH3 and a hydrocarbon, preferably natural gas or CH4, or (iii) a mixture containing NH3 and H2.

[0172] The air ratio λ (combustion air ratio) represents the actual mass of available air relative to the minimum required air mass theoretically required for stoichiometrically complete combustion. Depending on the composition of the fuel, the combustion in step (a) is preferably carried out with different air ratios λ.

[0173] When the fuel consists essentially of pure NH3 or the proportion of NH3 in the fuel is at least 90% by volume based on the total volume of the fuel, the combustion is preferably carried out at an air ratio λ in the range of 1.0 to 1.5, more preferably 1.1 to 1.4, even more preferably 1.1 to 1.3.

[0174] When the fuel consists essentially of a mixture of NH3 and CH4, with the proportion of CH4 being 50% by volume or less based on the total volume of the fuel, the combustion is preferably carried out at an air ratio λ in the range of 1.5 to 2.5, more preferably 1.6 to 2.4, and even more preferably 1.7 to 2.3.

[0175] When the fuel consists essentially of a mixture of NH3 and CH4, with the proportion of CH4 being greater than 50% by volume based on the total volume of the fuel, the combustion is preferably carried out at an air ratio λ in the range of 2.0 to 3.0, more preferably 2.1 to 2.9, and even more preferably 2.2 to 2.8.

[0176] When the fuel consists essentially of a mixture of NH3 and H2, with the proportion of H2 being 50% by volume or less based on the total volume of the fuel, the combustion is preferably carried out at an air ratio λ in the range of 2.0 to 3.0, more preferably 2.1 to 2.9, and even more preferably 2.2 to 2.8.

[0177] When the fuel consists essentially of a mixture of NH3 and H2, with the proportion of H2 being greater than 50% by volume based on the total volume of the fuel, the combustion is preferably carried out with an air ratio λ in the range of 2.5 to 3.5, more preferably 2.6 to 3.4, and even more preferably 2.7 to 3.3.

[0178] The combustion in step (a) preferably produces off-gases at a temperature in the range of 1000 to 1500°C before entering the turbine.

[0179] The combustion in step (a) preferably produces off-gases, preferably at a pressure in the range of 10 to 32 bar, before entering the turbine.

[0180] The combustion in step (a) preferably reduces the NO 2 content to preferably at most 5.0%, more preferably at most 4.0%, even more preferably at most 3.0%, most preferably at most 2.0%, especially at most 1.0%, and in some cases at most 0.5%, before entering the turbine. X The resulting off-gas has an oxidation degree of (n(NO2) / (n(NO)+n(NO2))).

[0181] According to the invention, combustion is preferably carried out in one stage, i.e., neither as lean premixed combustion nor as staged rich-lean combustion. Single-stage combustion allows optimized operation and simplifies the configuration of the gas turbine system. According to the invention, combustion is carried out with a relatively small excess air amount λ, thus intentionally avoiding high concentrations of NO. X At high temperatures of combustion (e.g., >1500°C), the balance of NO2 and NO, i.e., NO X The degree of oxidation is relative to the NO side, resulting in essentially NO X The total amount of NO is present in the hot combustion off-gas as NO, i.e., only a small amount of NO2 is present.

[0182] The gas turbine of the present invention preferably has an annular combustion chamber. There are preferably several burners arranged in a ring around the shaft upstream of the turbine. A secondary air flow is directed around these burners and mixed upstream of the turbine. Fuel premixing, complete combustion, and mixing must occur over a short distance.

[0183] Due to the high volumetric flow rates in gas turbines, off-gas cleaning can be quite complicated in some cases. Therefore, conventional methods of operating gas turbines often attempt to address pollutant emissions directly at the source through combustion engineering measures. A relatively high air excess λ leads to super-stoichiometric combustion, and therefore complete combustion can be assumed. Due to the limited thermal endurance of gas turbines, the air excess λ of stationary single-shaft machines usually cannot be lowered below λ values ​​of 2.5 to 3.5.

[0184] In conventional gas turbines that run on natural gas, NO X is generated in atmospheric nitrogen (thermal NO) at high temperatures for a sufficiently long reaction time. X ) In NH3-powered gas turbines, NO X Most of the fuel (fuel NO X ) is formed. Therefore, NO XTo suppress the formation of , the temperature and residence time in the hot zone must be reduced.

[0185] Cooling the flame by adding water or steam to the fuel has proven effective (wet abatement). At a fuel / steam mixture ratio of 1:1, NO X The content is reduced by 80%. However, the need to use expensive demineralized water to avoid scaling and corrosion of the turbine blades leads to higher operating costs with this measure.

[0186] Newer burners utilize intensive premixing of superstoichiometric air with fuel to avoid local excessive temperatures in combustion as a result of differences in fuel concentration (dry abatement). Here, different combustion zones are arranged in succession, for example, rich-lean zones where uniform flow conditions are emphasized to avoid reverse flow regions where the air may have a long residence time, with similarly good results.

[0187] In general, it can be assumed that the lower heating value of NH3 versus CH4 fuel combined with lower flame temperature results in a lower heat load to the turbine. However, the reduction in flame temperature also reduces the NO X and further promotes the formation of N2O.

[0188] Preferably, the off-gas produced by the combustion in step (a) is subsequently expanded in a gas turbine.

[0189] Preferably, the off-gas at the outlet from the gas turbine has a temperature in the range of 450 to 670°C.

[0190] Preferably, the off-gas at the outlet from the gas turbine is at a pressure higher than atmospheric pressure, i.e. ≧1.0 bara, but up to 1.2 bara, more preferably up to 1.1 bara.

[0191] Preferably, the off-gas at the outlet from the gas turbine contains NO in the range of 500 to 3000 ppmv. XIt has a content.

[0192] Preferably, the off-gas at the outlet from the gas turbine has an O2 content in the range of 1.0 to 6.0% by volume.

[0193] Preferably, the off-gas at the outlet from the gas turbine has an H2O content in the range of 20 to 30% by volume.

[0194] Preferably, the off-gas at the outlet from the gas turbine has an N2O content of maximum 500 ppmv, more preferably maximum 200 ppmv, even more preferably maximum 100 ppmv.

[0195] Preferably, the off-gas at the outlet from the gas turbine has an N2O content of at least 5 ppmv, more preferably at least 20 ppmv, even more preferably at least 50 ppmv.

[0196] Preferably, the off-gas at the outlet from the gas turbine has an NH3 content of maximum 800 ppmv, more preferably maximum 500 ppmv, even more preferably maximum 250 ppmv.

[0197] Preferably, the off-gas at the outlet from the gas turbine has an NH3 content of at least 10 ppmv, more preferably at least 50 ppmv, even more preferably at least 100 ppmv.

[0198] Preferably, the off-gas at the outlet from the gas turbine contains at most 10%, more preferably at most 9.0%, even more preferably at most 8.0%, most preferably at most 7.0%, in particular at most 6.0%, and in some cases at most 5.0% NO X The oxidation degree is (n(NO2) / (n(NO)+n(NO2))).

[0199] In a preferred embodiment, NH3 is combusted in step (a) in a mixture with CH4, and therefore the off-gas further comprises CO and CO2, preferably HCN.

[0200] Preferably, the off-gas at the outlet from the gas turbine has an HCN content of at least 5 ppmv, more preferably at least 10 ppmv, even more preferably at least 50 ppmv.

[0201] Preferably, the off-gas at the outlet from the gas turbine has an HCN content of maximum 1000 ppmv, more preferably maximum 500 ppmv, even more preferably maximum 200 ppmv, and most preferably maximum 100 ppmv.

[0202] In a particularly preferred embodiment, step (a) of the method of the present invention comprises: (a1) the component step of thermally and / or catalytically cracking NH to produce a cracked gas comprising N, H, and optionally residual NH; (a2) optionally mixing the cracking gas with additional NH3 to produce a mixture comprising H2 and NH3; (a3) the component step of combusting the cracking gas or mixture; Includes:

[0203] Suitable methods for the thermal and / or catalytic cracking of NH to N and H are known to those skilled in the art. Suitable catalysts for cracking NH to N and H are, for example, Ru supported on AlO or SiO, Fe, Co, Ni, Cu or Ru supported on MgAlO, 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).

[0204] If the cracking in component step (a1) does not proceed to completion, the cracked gas (i.e., the cracking product) will contain residual unconverted NH3 as well as N2 and H2. In this way, a mixture of NH3 and H2 is already obtained, which can be directly combusted as is or first enriched with additional NH3 in optional component step (a2).

[0205] If the cracking in component step (a1) goes to completion, the required amount of NH3 must still be added to the cracking gas in step (a2).

[0206] Preferably, component step (a1) and optionally component step (a2) establish a mixture ratio of NH3 and H2 that 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%, in particular at most 40 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%.

[0207] In particularly preferred embodiments, 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 or from 70:30 to 75:25.

[0208] In component step (a3), the mixture is typically combusted with air. In a preferred embodiment, the air ratio λ for combustion in component step (a3) ​​is 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. The air ratio λ (i.e., combustion air ratio) indicates the mass ratio of air to fuel 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, rather than air, is used in the combustion operation, then "air" should, strictly speaking, be replaced by "oxygen carrier." However, the λ parameter is still used in the above definition.

[0209] 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.

[0210] In another preferred embodiment, NH3 is combusted alone in step (a), i.e., NH3 is the only combustible gas that is combusted.

[0211] In a preferred embodiment, the firing system, preferably an internal combustion engine, is mounted on a vehicle and serves to move the vehicle. The vehicle is preferably a watercraft. The vehicle is preferably a road vehicle selected from commercial vehicles, trucks and passenger cars, or a rail vehicle.

[0212] In another preferred embodiment, the firing system, preferably a gas turbine, is part of a power plant, which preferably produces electricity and / or district heating.

[0213] In a further preferred embodiment, the calcination system, preferably a furnace for cracking NH to N and H, is integrated into a system for thermal and / or catalytic cracking of NH to N and H. The combustion of NH is then integrated into a process for thermal and / or catalytic cracking of NH to N and H.

[0214] 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. X The 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.

[0215] 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.

[0216] 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.

[0217] 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.

[0218] 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.

[0219] 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.

[0220] 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.

[0221] 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.

[0222] 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.

[0223] In another 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.%.

[0224] 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.

[0225] 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.

[0226] 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.

[0227] 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.

[0228] 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.

[0229] 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.

[0230] 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.

[0231] 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.

[0232] Preferably, the off-gas comprises further gaseous components, preferably selected from the group consisting of O2, CO, CO2, NH3, CH4 and mixtures thereof.

[0233] Preferably, the off-gas leaving the calcination system, preferably an internal combustion engine, gas turbine or furnace, 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.

[0234] Preferably, the off-gas leaving the calcination system, preferably an internal combustion engine, gas turbine or furnace, 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.

[0235] Preferably, the off-gas is cooled over the course of the method of the present invention after leaving the calcination system, although steps (c1) and / or (c2) and / or (d) may introduce new heat.

[0236] Preferred variant of the combination of steps (c) and (d): In a preferred embodiment, steps (c1) and / or (c2) and / or (d) 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.

[0237] Preferably, the off-gas leaving the calcination system, preferably an internal combustion engine, gas turbine or furnace, is at a pressure of up to 1.5 bar, preferably atmospheric pressure.

[0238] Preferably, the off-gas leaving the firing system, preferably an internal combustion engine, gas turbine or furnace, 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

[0239] Preferably, the off-gas leaving the firing system, preferably an internal combustion engine, gas turbine or furnace, contains 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 has an oxidation degree of

[0240] Preferably, the off-gas leaving the calcination system, preferably an internal combustion engine, gas turbine or furnace, has an O2 content of less than 2.0% by volume.

[0241] Preferably, the off-gas leaving the calcination system, preferably an internal combustion engine, gas turbine or furnace, has an O2 content by volume greater than 4.0%.

[0242] In step (b) of the method of the present invention, the off-gas exiting the firing system, preferably an internal combustion engine, gas turbine or furnace, is transferred to an off-gas treatment system.

[0243] This can be done, for example, by means of a pipeline connecting the outlet of the calcination system, preferably an internal combustion engine, a gas turbine or a furnace, to the inlet of the off-gas treatment system. Since the process of the invention is preferably carried out at atmospheric pressure, no special requirements are usually imposed on such pipelines with regard to possible compressive stresses.

[0244] However, the pipeline should withstand the temperatures of the off-gas as it leaves the firing system, preferably an internal combustion engine, gas turbine or furnace, or as it enters the off-gas treatment system.

[0245] In a preferred embodiment, the off-gas temperature is measured at the outlet of the calcination system, preferably an internal combustion engine, a gas turbine or a furnace, and optionally modified with a suitable device so that the off-gas entering the off-gas treatment system has an optimized temperature under given conditions for the execution of steps (c) and (d) of the method of the present invention in the off-gas treatment system. The optimized temperature is in particular the temperature of the NO decomposition catalyst and / or the NO reduction catalyst and the NO X The optimized temperature depends on the type of catalytic material used in the reduction catalyst. The optimized temperature depends on the selected configuration of steps (c) and (d), i.e., NO reduction and NO X The type and sequence of the individual process steps for reduction, in particular the N2O decomposition catalyst and / or N2O reduction catalyst and the NO X This is guided by the type of catalytic material used in the reduction catalyst.

[0246] 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.

[0247] Preferably, the at least one heat exchanger in which the off-gas is cooled is arranged downstream of the gas turbine in the flow direction of the off-gas and upstream of the off-gas treatment system.

[0248] Preferably, the off-gas temperature at the outlet from the heat exchanger is at most 550°C, more preferably at most 525°C, even more preferably at most 500°C.

[0249] Preferably, the off-gas temperature at the outlet from the heat exchanger is at least 400°C, more preferably at least 425°C, even more preferably at least 450°C.

[0250] In order to avoid heat losses, it is preferred according to the invention to choose the distance from the outlet of the firing system, preferably the internal combustion engine, gas turbine or furnace, to the inlet to the off-gas treatment system as short as possible, thus achieving a compact design.

[0251] 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 (c1), (c2) and (d), 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.

[0252] The off-gas treatment system of the present invention is particularly used to carry out steps (c) and (d) of the method of the present invention, however, in addition to steps (c) and (d), further steps and chemical reactions may also be carried out within the off-gas treatment system.

[0253] 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 (c) and (d).

[0254] In carrying out steps (c) and (d) 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 catalyst used, the reducing agent used, the space velocity and other reaction conditions.

[0255] 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.

[0256] 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.

[0257] Particularly preferred variants / embodiments are: [a] (c2) chemical reduction of N2O with NH3 and (d) NO with NH3, preferably together in one reaction zone X Chemical reduction of; [b] (c2) chemical reduction of N2O with hydrocarbons (CH4, natural gas, etc.) and (d) NO with NH3, preferably together in one reaction zone X Chemical reduction of; [c] (c1) decomposition of NO with NH3 and (d) decomposition of NO, preferably together in one reaction zoneX Chemical reduction of; [d] (c1) decomposition of N2O and (c2) chemical reduction of N2O with NH3 and (d) NO with NH3, preferably together in one reaction zone. X Chemical reduction of; [e] (c1) decomposition of N2O and (c2) chemical reduction of N2O with hydrocarbons (CH4, natural gas, etc.) and (d) decomposition of NO with NH3, preferably together in one reaction zone. X Chemical reduction of; [f] (c1) decomposition of N2O, preferably in a first reaction zone; then (d) decomposition of NO with NH3, preferably in a second reaction zone. X Chemical reduction of; [g] (c1) preferably incomplete decomposition of N2O in a first reaction zone; then (c2) chemical reduction of residual N2O with NH3 and (d) preferably decomposition of NO2O with NH3 in a second reaction zone. X Chemical reduction of; [h] (c1) preferably incomplete decomposition of N2O in a first reaction zone; then (c2) chemical reduction of the residual N2O with hydrocarbons (CH4, natural gas, etc.) and (d) preferably decomposition of NO with NH3 in a second reaction zone. X Chemical reduction of; [i] (c1) preferably incomplete decomposition of N2O in the first reaction zone; then (c1*) decomposition of residual N2O and (d) preferably decomposition of NO with NH3 in the second reaction zone. X Chemical reduction of; [j] (c1) preferably incomplete decomposition of N2O in a first reaction zone; then (c1*) decomposition of residual N2O, and (c2) chemical reduction of residual N2O with NH3 and (d) preferably decomposition of NO in a second reaction zone. X Chemical reduction of with NH3; [k] (c1) preferably incomplete decomposition of N2O in a first reaction zone; then (c1*) decomposition of residual N2O, and (c2) chemical reduction of residual N2O with hydrocarbons (CH4, natural gas, etc.), and (d) preferably reduction of NO2O with NH3 in a second reaction zone. X Chemical reduction of.

[0258] [;] (d) preferably NO in the first reaction zone X incomplete chemical reduction of NO; ​​then (c1) decomposition of NO and (d*) preferably residual NO with NH in a second reaction zone. X Chemical reduction of; [m](d) preferably NO in the first reaction zone X incomplete chemical reduction of NO; ​​then (c1) decomposition of NO, and (c2) chemical reduction of NO with NH, and (d*) decomposition of residual NO preferably with NH in a second reaction zone. X chemical reduction of; or [n](d) preferably NO in the first reaction zone X then (c1) decomposition of NO, and (c2) chemical reduction of NO with hydrocarbons (CH, natural gas, etc.), and (d*) decomposition of residual NO with NH, preferably in a second reaction zone. X Chemical reduction of.

[0259] 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.

[0260] 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.

[0261] For purposes of illustration, an "*" indicates a component method step that has previously been performed only partially in the same type of component method step; the component method step identified by the "*" then continues the previously performed component method step only partially, but possibly in a different reaction zone or a different catalyst bed. As with all other method steps, unless otherwise specified, the results achieved at the end of all component method steps are not quantified. For example, in the first component method step (d), NO X If NO is chemically incompletely reduced, the fact that component method step (d*) is subsequently performed means that at the end of component method step (d*), 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 (d*), X It is entirely possible that residual amounts of are still present.

[0262] 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.

[0263] 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 NO 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.

[0264] 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.

[0265] 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).

[0266] 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.

[0267] 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 (c) and (d) 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.

[0268] 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.

[0269] In a preferred embodiment, the reaction zones are each spatially separated catalyst beds.

[0270] In a preferred embodiment, the off-gas undergoes the steps of the method of the present invention in one of the following orders:

[0271] (i) (a) → (b) → (c1) → (d); step (c1) preferably proceeds in a first reaction zone; step (d) proceeds in a second reaction zone; (ii) (a) → (b) → (d) → (c2); step (d) preferably proceeds in the first reaction zone; step (c2) proceeds in the second reaction zone; (iii) (a) → (b) → (d) → (c2) → (c1); step (d) preferably proceeds in the first reaction zone; step (c2) proceeds in the second reaction zone; step (c1) proceeds in the third reaction zone; (iv) (a) → (b) → (d) → (c1) + (c2); step (d) preferably proceeds in a first reaction zone; step (c1) and step (c2) proceed in a second reaction zone; (v) (a) → (b) → (d) → (c1); step (d) preferably proceeds in the first reaction zone; step (c1) proceeds in the second reaction zone; (vi) (a) → (b) → (c1) + (d) → (d*); preferably, step (c1) and step (d) proceed incompletely in the first reaction zone; the remainder of step (d*) proceeds in the second reaction zone; (vii) (a) → (b) → (c1) + (d) → (d*) + (c2); preferably, step (c1) and step (d) proceed incompletely in the first reaction zone; and step (c2) and the remainder of step (d*) proceed in the second reaction zone; (viii) (a) → (b) → (c1) + (c2) + (d) → (c1*) + (c2*) + (d*); preferably, step (c1) proceeds partially and step (c2) partially and step (d) partially in a first reaction zone that preferably does not contain a zeolitic material as a catalyst; the remainder of step (c1*) and the remainder of step (c2*) and the remainder of step (d*) proceeds preferably in a second reaction zone that contains a zeolitic material as a catalyst; (ix) (a) → (b) → (c1) + (c2) + (d) → (c1*) + (c2*) + (d*); preferably, step (c1) proceeds incompletely and step (c2) incompletely and step (d) incompletely in a first reaction zone, preferably comprising a zeolitic material as a catalyst; the remainder of step (c1*) and the remainder of step (c2*) and the remainder of step (d*) preferably proceeds in a first reaction zone comprising NO as a catalyst. X proceeds in a second reaction zone containing a sensitive N2O decomposition catalyst; (x) (a) → (b) → (c1) → (c1*) + (c2) + (d); preferably, step (c1) proceeds incompletely in a first reaction zone, preferably comprising a zeolitic material as a catalyst; step (c1*) and step (c2) and the remainder of step (d) proceed in a second reaction zone, preferably comprising a zeolitic material as a catalyst; (xi) (a) → (b) → (c1) → (c1*) + (c2) + (d); preferably, step (c1) is preferably carried out using NO as a catalyst. X The first reaction zone preferably comprises a sensitive NO decomposition catalyst; the remainder of step (c1*), step (c2) and step (d) preferably comprise a second reaction zone comprising a zeolitic material as a catalyst.

[0272] 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 (c2) and (d) 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 (c1) (first reaction zone). Since there is a reducing agent downstream of the feed point, steps (c2) and (d) of the method of the present invention can be carried out, possibly overlapping with step (c1) (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 due to the absence of a reducing agent, and the chemical reduction of NO in the first reaction zone and the decomposition of NO are not possible. X They differ from each other in that no chemical reduction of

[0273] 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.

[0274] 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.

[0275] 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).

[0276] Preferably, the temperature in the first reaction zone (within the first catalyst bed) 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.

[0277] 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.

[0278] Preferably, 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, especially at least 100°C.

[0279] Preferably, 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.

[0280] 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.

[0281] 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.

[0282] 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).

[0283] 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).

[0284] 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.

[0285] 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.

[0286] 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.

[0287] Preferably, the first reaction zone and the second reaction zone are located within a common vessel.

[0288] 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.

[0289] 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.

[0290] 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.

[0291] 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.

[0292] 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.

[0293] 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.

[0294] 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.

[0295] 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.

[0296] Preferably, the off-gas entering the off-gas treatment system is at a relatively lower temperature than the temperature of the off-gas exiting the calcination system, preferably an internal combustion engine, gas turbine or furnace, preferably 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.

[0297] Preferably, the off-gas entering the off-gas treatment system is at a pressure of at most 1.4 bara, preferably at most 1.3 bara, more preferably at most 1.2 bara.

[0298] 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

[0299] 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

[0300] 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

[0301] Preferably, the off-gas entering the off-gas treatment system has an O2 content of less than 2.0% by volume.

[0302] Preferably, the off-gas entering the off-gas treatment system has an O2 content greater than 4.0% by volume.

[0303] In step (c) of the method of the present invention, the NO content in the off-gas is reduced. This can be achieved in various ways: (c1) decomposition of NO via an NO decomposition catalyst and / or (c2) chemical reduction of NO with a reducing agent via an NO reduction catalyst. Step (c) of the method of the present invention is carried out in an off-gas treatment system.

[0304] In a preferred embodiment, step (c) comprises (d1) reducing the N2O content in the off-gas by decomposing N2O via an N2O decomposition catalyst.

[0305] 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.

[0306] 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 (d), i.e., the NO in the off-gas is XThe 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

[0307] Preferably, the N2O decomposition catalyst is disposed in a radial basket through which the flow passes axially.

[0308] The N2O decomposition catalyst is preferably in particulate form and comprises at least 50 particles.

[0309] In a preferred embodiment, step (c) comprises (c2) 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.

[0310] Preferably, the N2O reduction catalyst is disposed in a radial basket through which the flow passes axially.

[0311] The N2O reduction catalyst is preferably in particulate form and comprises at least 50 particles.

[0312] In a preferred embodiment, step (c) comprises: - (c1) decomposing N2O via an N2O decomposition catalyst, preferably the N2O decomposition catalyst is 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, AEI and / or MEL structural type, - (c2) 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- or copper-containing zeolite, even more preferably an iron- or copper-containing zeolite of the MFI, BEA, FER, MOR, FAU, AEI and / or MEL structural type, This includes reducing the N2O content in the off-gas by both

[0313] Preferably, the reducing agent in step (c2) is selected from NH3, hydrocarbons, CO, H2 and mixtures thereof, preferably NH3.

[0314] In a preferred embodiment, the reducing agent in step (c2) 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.

[0315] In a preferred embodiment, the reducing agent in step (c2) 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 (d) also proceeds with a catalyst bed of the NO reduction catalyst, this amount is X Any necessary amount of NH3 is added for reduction.

[0316] 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 (d) also proceeds with a catalyst bed of the NO reduction catalyst, or if the device of the present invention is configured accordingly, this amount is XAny necessary amount of NH3 for reduction is added as well.

[0317] The reducing agent may also already be present in the off-gas, for example in the form of residual fuel and / or its 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 fuel and / or its oxidation products).

[0318] In step (d) 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 (d) of the method of the present invention is also carried out in an off-gas treatment system.

[0319] 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.

[0320] Preferably, NO X The reduction catalyst is placed in a radial basket through which the flow passes axially.

[0321] Preferably, NO X The reduction catalyst is in particulate form and comprises at least 50 particles.

[0322] Preferably, the reducing agent in step (d) is selected from NH3, hydrocarbons, CO, H2 and mixtures thereof, preferably NH3.

[0323] Preferably, the reducing agent in step (d) is chemically reduced NO XNH3 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

[0324] In a preferred embodiment, the reducing agent in step (c2) is the same as the reducing agent in step (d), preferably NH3.

[0325] 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 steps (c2) and / or (d) 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.

[0326] A particularly preferred process regime of the present invention is described in detail below.

[0327] 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 (d)) (de-NO Xstep (c1), the N2O content in the off-gas may be further reduced by decomposition of N2O via an N2O decomposition catalyst (step (c1)) and / or chemical reduction of N2O with a reducing agent via an N2O reduction catalyst (step (c2)); 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 (c1)) and / or chemical reduction of N2O with a reducing agent via an N2O reduction catalyst (step (c2)) (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 (d)).

[0328] 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.

[0329] Preferably, the temperature of the off-gas entering the first reaction zone is at most 400°C, preferably at most 350°C.

[0330] 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.

[0331] 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.

[0332] 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. Xcontent and N2O content in the range of 200 to 2000 ppmv.

[0333] 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, over which the off-gas passes successively through 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 (d)) (de-NO X step (c1), the N2O content in the off-gas may be further reduced by decomposition of N2O via an N2O decomposition catalyst (step (c1)) and / or chemical reduction of N2O with a reducing agent via an N2O reduction catalyst (step (c2)); 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 (c1)) and / or chemical reduction of N2O with a reducing agent via an N2O reduction catalyst (step (c2)) (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 (d)).

[0334] Preferably, the NO in the first 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.

[0335] 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.

[0336] 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.

[0337] 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.

[0338] 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.

[0339] 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 (c1), NO is decomposed, and (d) NO is decomposed. Xis incompletely chemically reduced with NH, at least a portion of which may preferably originate from the incomplete combustion of NH in step (a) (NH slip), and (ii) in a second catalyst bed (c2), residual N2O is chemically reduced with NH, (c1*) residual N2O may be decomposed, and (d*) residual NO X is chemically reduced with NH3.

[0340] 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

[0341] 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.

[0342] Preferably, NO X Additional 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.

[0343] Preferably, the temperature of the off-gas leaving the first catalyst bed is in the range of 400 to 550°C.

[0344] 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.

[0345] 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 X has an oxidation degree of

[0346] 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

[0347] 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

[0348] 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

[0349] 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

[0350] 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.

[0351] Preferably, residual NO X is a NO 3 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%.

[0352] 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 X and 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.

[0353] 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[NOX ] 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

[0354] 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:

[0355] 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.

[0356] 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.

[0357] 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.

[0358] 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.

[0359] 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.

[0360] NO leaving the first catalyst bed X If the molar ratio of NH3 / N2O is at least 10, the metered addition of NH3 via the second device X It is preferred to do this only for the amount of

[0361] 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 no more than 550° C., more preferably no more than 525° C., even more preferably no more than 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.

[0362] 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.

[0363] 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.

[0364] 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.

[0365] 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 from 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.

[0366] 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 slipX and - Allows simultaneous complete or substantially complete decomposition of N2O at a relatively low catalyst volume, i.e., at a relatively high space velocity.

[0367] 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 X The 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

[0368] 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.

[0369] 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 XIt was found to inhibit the establishment of equilibrium.

[0370] 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 X A decrease in the degradation of α-tocopherol may even be observed.

[0371] 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

[0372] 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

[0373] 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.

[0374] 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.

[0375] 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.

[0376] 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 Xand produces an off-gas that further contains N2O.

[0377] 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

[0378] 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. [Brief explanation of the drawings]

[0379] [Figure 1] 1 shows a schematic representation of a preferred embodiment according to the present invention in which a first waste heat steam generator (ADE1), a second waste heat steam generator (ADE2), a first catalyst bed (K1) and a second catalyst bed (K2) can be arranged to contact the hot turbine off-gas downstream of the turbine outlet. [Figure 2]1 shows a schematic representation of a preferred embodiment according to the present invention in which a first waste heat steam generator (ADE1), a second waste heat steam generator (ADE2), a first catalyst bed (K1) and a second catalyst bed (K2) can be arranged to contact the hot turbine off-gas downstream of the turbine outlet. [Figure 3] 1 shows a schematic representation of a preferred embodiment according to the present invention in which a first waste heat steam generator (ADE1), a second waste heat steam generator (ADE2), a first catalyst bed (K1) and a second catalyst bed (K2) can be arranged to contact the hot turbine off-gas downstream of the turbine outlet. [Figure 4] Another embodiment is shown in which there is only one catalyst bed and the combustion is carried out as a premixed combustion. [Figure 5] Another embodiment is shown in which there is only one catalyst bed and the combustion is carried out as a rich-lean combustion. DETAILED DESCRIPTION OF THE INVENTION

[0380] Waste Heat Steam Generator In a preferred embodiment, the off-gas treatment system of the present invention comprises a first waste heat steam generator, preferably a second waste heat steam generator, the first waste heat steam generator being arranged upstream of the second waste heat steam generator in the flow direction of the off-gas.

[0381] 1 to 3 show a schematic diagram of a preferred embodiment according to the present invention, in which a first waste heat steam generator (ADE1), a second waste heat steam generator (ADE2), a first catalyst bed (K1), and a second catalyst bed (K2) can be arranged to contact the hot turbine off-gas downstream of the turbine outlet. The generator (G) drives a compressor (V), in which air is compressed. Ammonia, possibly in a mixture with CH4 or H2, is burned in a combustion chamber (VK, combustion chamber), and the formed off-gas enters the gas turbine (GT) under expansion. After leaving the gas turbine (GT), the off-gas is fed to an off-gas treatment system (AB), which comprises a first waste heat steam generator (ADE1), a second waste heat steam generator (ADE2), a first catalyst bed (K1), and a second catalyst bed (K2). In the second waste heat steam generator (ADE2), and then also in the first waste heat steam generator (ADE1), steam absorbs heat from the off-gas. The heated steam is fed to a steam turbine driven by a generator (G) and flows through a heat exchanger (WT). After leaving the off-gas treatment system (AB), the off-gas is fed to a chimney (SS).

[0382] In a preferred embodiment, the off-gas flows first through a first waste heat steam generator, then a first catalyst bed, then a second catalyst bed, and finally a second waste heat steam generator (FIG. 1).

[0383] In another preferred embodiment, the off-gas flows first through a first waste heat steam generator, then through a first catalyst bed, then through a second waste heat steam generator, and finally through a second catalyst bed (FIG. 2).

[0384] In a more preferred embodiment, the off-gas flows first through a first catalyst bed, then a first waste heat steam generator, then a second catalyst bed, and finally a second waste heat steam generator (FIG. 3).

[0385] In other, less preferred embodiments, there is only one catalyst bed and combustion is carried out in two stages as premixed combustion (Figure 4) or rich-lean combustion (Figure 5).

[0386] De-N2O-de-NO 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 via an N2O decomposition catalyst (step (c1)) (N2O removal stage); 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 (d)) (de-NO X After the decomposition of N2O via an N2O decomposition catalyst (step (c1)), the N2O content in the off-gas may be further reduced by further decomposition of N2O via an N2O decomposition catalyst (step (c1)) and / or chemical reduction of N2O with a reducing agent via an N2O reduction catalyst (step (c2)).

[0387] Preferably, no reducing agent is added to the off-gas upstream of the first reaction zone.

[0388] 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.

[0389] 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.

[0390] 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.

[0391] 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.

[0392] Preferably, the first reaction zone and the second reaction zone are operated at different temperature levels here.

[0393] 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 XIn 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.

[0394] 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.

[0395] 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.

[0396] 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.

[0397] 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 via an N2O decomposition catalyst (step (c1)) and by chemical reduction with a reducing agent via an N2O reduction catalyst (step (c2)).

[0398] 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 (c2)).

[0399] 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.

[0400] Closed-Loop Control Regardless of the respective process regime, the method of the present invention is preferably under closed-loop control.

[0401] In a preferred embodiment, depending on the configuration of the calcination system, preferably an internal combustion engine, a gas turbine or a furnace, the first measurement variable measured for the closed-loop control of the method of the invention is at least one parameter characteristic of the current operating state of the calcination system, preferably an internal combustion engine, a gas turbine or a furnace. Preferably, this first measurement variable or parameter is selected from the group consisting of the combustion temperature, the NH3 consumption, optionally the rotation speed, and the noise emitted by the calcination system, preferably an internal combustion engine, a gas turbine or a furnace.

[0402] In particular, the characteristics of the off-gas leaving the firing system, preferably an internal combustion engine, a gas turbine or a furnace, i.e. -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; Depending on the NO in the off-gas X The process conditions can be optimized to achieve an efficient and economically viable reduction in the content of N2O.

[0403] Therefore, in a preferred embodiment, in order to control the method of the present invention, in addition to or instead of the first measurement variable, 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 at the outlet from the firing system, preferably an internal combustion engine, a gas turbine or a furnace, and / or at the inlet to the off-gas treatment system. 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.

[0404] 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.

[0405] 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.

[0406] 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.

[0407] 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

[0408] 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.

[0409] 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).

[0410] The preferred manipulated variables (control variables) according to the present invention are as follows:

[0411] - amount of reducing agent; - Off-gas temperature, if appropriate; and - Catalyst temperature, if appropriate.

[0412] 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.

[0413] 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.

[0414] A further aspect of the present invention is (i) an NH3-driven gas turbine, preferably an NH3-driven internal combustion engine, an NH3-driven gas turbine, or a furnace for cracking NH3 into N2 and H2; and (ii) an off-gas treatment system; In a device comprising: The apparatus is configured to carry out a method according to any of the preceding claims.

[0415] A particularly preferred embodiment of the present invention is summarized in the following sentence:

[0416] Sentence 1: NO in the off-gas of NH3-powered firing systems X and a method for reducing the content of N2O, Sentence 2: The method includes (a) burning NH3 to drive a calcination system and producing N2, H2O, and NO X (b) transferring the off-gas to an off-gas treatment system; (c) reducing the N2O content in the off-gas by (c1) decomposing N2O via an N2O decomposition catalyst and / or (c2) chemically reducing N2O with a reducing agent via an N2O reduction catalyst; and (d) removing N2O from the off-gas. X NO by reducing agent through reduction catalyst X By chemically reducing NO in the off-gas X and reducing the content.

[0417] Sentence 3: The method of sentence 1, wherein the NH3-powered firing system is an NH3-driven internal combustion engine or an NH3-driven gas turbine.

[0418] Sentence 4: The method of sentence 1, wherein the NH3-powered calcination system is a furnace for cracking NH3 into N2 and H2.

[0419] Sentence 5: 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 zeolite material, preferably a zeolite comprising a transition metal (including a lanthanide), in particular iron, cobalt or copper, more preferably an iron-containing zeolite, even more preferably independently an iron-containing zeolite of MFI, BEA, FER, MOR, FAU and / or MEL structural type.

[0420] Sentence 6: The method of any of the preceding sentences, wherein the N2O decomposition catalyst and the N2O reduction catalyst are formed from the same material.

[0421] Sentence 7: N2O decomposition catalyst and NO X The method of any of the preceding sentences, wherein the reduction catalysts are formed from the same material.

[0422] Sentence 8: NO reduction catalyst and NO X The method of any of the preceding sentences, wherein the reduction catalysts are formed from the same material.

[0423] Sentence 9: 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.

[0424] Sentence 10: The method of any of the preceding sentences, wherein the combustion of NH3 in step (a) is not carried out via a catalyst.

[0425] Sentence 11: A method according to any of the preceding sentences, wherein NH3 is combusted in step (a) in a mixture with a further combustible gas, preferably the further combustible gas being selected from (i) H2, (ii) fossil fuels, preferably hydrocarbons and hydrocarbon mixtures, more preferably methane, ethane, propane, butane, natural gas, gasoline and / or diesel, (iii) alcohols, preferably methanol and / or ethanol, and mixtures thereof. Sentence 12: A method according to any of the preceding sentences, wherein NH3 is burned in a mixture with H2 in step (a).

[0426] Sentence 13: The method of sentence 11, wherein step (a) comprises the component steps of (a1) thermally and / or catalytically cracking NH3 to produce a cracked gas comprising N2, H2, and optionally residual NH3, (a2) optionally mixing the cracked gas with additional NH3 to produce a mixture comprising H2 and NH3, and (a3) ​​combusting the cracked gas or mixture. Sentence 14: The method according to sentence 11 or 12, wherein the proportion of H2 in the mixture with 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%.

[0427] Sentence 15: A method according to any of sentences 11 to 13, wherein the proportion of H2 in the mixture with 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%.

[0428] Sentence 16: The method of any of sentences 11 to 14, wherein the molar ratio of H2:NH3 in the mixture is within 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.

[0429] Sentence 17: The method of any of sentences 11 to 15, wherein the air ratio λ is 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.

[0430] Sentence 18: The method of any of sentences 1 to 9, wherein in step (a) only NH3 is combusted, and thus NH3 is the only combustible gas combusted.

[0431] Sentence 19: A method according to any of the preceding sentences, wherein the firing system, preferably an internal combustion engine, is mounted on a vehicle and used to propel the vehicle.

[0432] Sentence 20: The method of sentence 18, wherein the vehicle is a watercraft.

[0433] Sentence 21: The method of sentence 18, wherein the vehicle is a road vehicle, preferably selected from a commercial vehicle, a truck, and a passenger car, or is a rail vehicle.

[0434] Sentence 22: A method according to any of the preceding sentences, wherein the firing system, preferably a gas turbine, is part of a power generation plant.

[0435] Sentence 23: The method of sentence 21, wherein the power plant generates electricity and / or district heating.

[0436] Sentence 24: A method according to any of the preceding sentences, wherein the calcination system, preferably a furnace, is incorporated into a system for thermal and / or catalytic cracking of NH3 to N2 and H2.

[0437] Sentence 25: 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.

[0438] Sentence 26: The method of any of the preceding sentences, wherein the off-gas has a 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, and especially at least 10 times higher than the NO content.

[0439] Sentence 27: The method of any of the preceding sentences, wherein the off-gas has a NO2 content that is greater 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, and especially at least 10 times higher than the N2O content.

[0440] Sentence 29: The method of any of sentences 1 to 23, 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, and especially at least 10 times higher than the NO content.

[0441] Sentence 30: The method of any of the preceding sentences, wherein the off-gas has an N2O content that is greater 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.

[0442] Sentence 29: 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, and especially at least 10 times higher than the NO content.

[0443] Sentence 31: 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 A method according to any of the preceding sentences having the content.

[0444] Sentence 32: 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 A method according to any of the preceding sentences having the content.

[0445] Sentence 33: 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 A method according to any of the preceding sentences having the content.

[0446] Sentence 34: The method of 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.

[0447] Sentence 35: The method of 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.

[0448] Sentence 36: The method of 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.

[0449] Sentence 37: The method of any of the preceding sentences, wherein the off-gas has an H2O content of less than 2.0% by volume.

[0450] Sentence 38: The method of 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.%.

[0451] Sentence 39: The method of 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, and in particular at least 20% by volume.

[0452] Sentence 40: The method of any of the preceding sentences, wherein the off-gas has an HO content within the range of 10±8% by volume, preferably within the range of 10±7% by volume, more preferably within the range of 10±6% by volume, even more preferably within the range of 10±5% by volume, most preferably within the range of 10±4% by volume, and in particular within the range of 10±3% by volume.

[0453] Sentence 41: The method of 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, and in particular in the range of 15±3% by volume.

[0454] Sentence 42: The method of any of the preceding sentences, wherein the off-gas has an HO content within the range of 20±8% by volume, preferably within the range of 20±7% by volume, more preferably within the range of 20±6% by volume, even more preferably within the range of 20±5% by volume, most preferably within the range of 20±4% by volume, and in particular within the range of 20±3% by volume.

[0455] Sentence 43: The method of any of the preceding sentences, wherein the off-gas has an HO content within the range of 25±8% by volume, preferably within the range of 25±7% by volume, more preferably within the range of 25±6% by volume, even more preferably within the range of 25±5% by volume, most preferably within the range of 25±4% by volume, and in particular within the range of 25±3% by volume.

[0456] Sentence 44: The method of 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, and especially in the range of 30±3% by volume.

[0457] Sentence 45: The method of 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.

[0458] Sentence 46: The method of 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.

[0459] Sentence 47: 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.

[0460] Sentence 48: A method according to any of the preceding sentences, wherein the off-gas exiting the firing system, preferably an internal combustion engine, gas turbine, or furnace, 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, and especially at least 900°C.

[0461] Sentence 49: A method according to any of the preceding sentences, wherein the off-gas leaving the firing system, preferably an internal combustion engine, gas turbine, or furnace, 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.

[0462] Sentence 50: A method according to any of the preceding sentences, wherein the off-gas leaving the firing system, preferably an internal combustion engine, a gas turbine, or a furnace, is at a pressure of up to 1.5 bar, preferably atmospheric pressure.

[0463] Sentence 51: The off-gas from a firing system, preferably an internal combustion engine, gas turbine, or furnace, 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

[0464] Sentence 52: The off-gas from a firing system, preferably an internal combustion engine, gas turbine, or furnace, 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

[0465] Sentence 53: A method according to any of the preceding sentences, wherein the off-gas exiting the firing system, preferably an internal combustion engine, a gas turbine, or a furnace, has an O2 content of less than 2.0% by volume.

[0466] Sentence 54: A method according to any of sentences 1 to 28, wherein the off-gas upon exiting an internal combustion engine, preferably an internal combustion engine, a gas turbine, or a furnace, has an O2 content of more than 4.0% by volume.

[0467] Sentence 55: 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 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.

[0468] Sentence 56: 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.

[0469] Sentence 57: 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.

[0470] Sentence 58: 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.

[0471] Sentence 59: A 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 as it leaves the internal combustion engine, preferably the internal combustion engine, gas turbine, or furnace.

[0472] Sentence 60: The method of 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.

[0473] Sentence 61: 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

[0474] Sentence 62: 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

[0475] Sentence 63: A method according to 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.

[0476] Sentence 64: A method according to any of sentences 1 to 36, wherein the off-gas entering the off-gas treatment system has an O2 content greater than 4.0% by volume.

[0477] Sentence 65: A method according to any of the preceding sentences, wherein step (c) comprises reducing the N2O content in the off-gas by (c1) 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.

[0478] Sentence 66: A method according to any of the preceding sentences, wherein step (c) comprises reducing the N2O content in the off-gas by (c2) 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 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.

[0479] Sentence 67: A method according to any of the preceding sentences, wherein the reducing agent in step (c2) is selected from NH3, a hydrocarbon, CO, H2 and mixtures thereof, preferably NH3.

[0480] Sentence 68: A method according to any of the preceding sentences, wherein the reducing agent in step (c2) 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.

[0481] Sentence 69: A method according to any of the preceding sentences, wherein the reducing agent in step (c2) 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.

[0482] Sentence 70: NO XThe 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.

[0483] Sentence 71: The method of any of the preceding sentences, wherein the reducing agent in step (d) is selected from NH3, a hydrocarbon, CO, H2, and mixtures thereof, and is preferably NH3.

[0484] Sentence 72: The reducing agent in step (d) is NO to be 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, preferably 1.0 to 1.2 molar parts, based on the molar ratio of

[0485] Sentence 73: The method of any of the preceding sentences, wherein the reducing agent in step (c2) is the same as the reducing agent in step (d), preferably NH3.

[0486] Sentence 74: The off-gas treatment system includes a first reaction zone and a second reaction zone, the off-gas is continuously passed through the second reaction zone beyond the second reaction zone, a reducing agent is added to the off-gas upstream of the first reaction zone, and NO in the off-gas is reduced in the first reaction zone. X The content is first, NO X NO by reducing agent through reduction catalyst X(step (d)), the N2O content in the off-gas is optionally further reduced by decomposition of N2O via an N2O decomposition catalyst (step (c1)) and / or by chemical reduction of N2O with a reducing agent via an N2O reduction catalyst (step (c2)), 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 (c1)) and / or by chemical reduction of N2O with a reducing agent via an N2O reduction catalyst (step (c2)), and the N2O content in the off-gas is X The content may optionally be NO X NO via reduction catalyst X The method of any of the preceding sentences, wherein the compound is further reduced by chemical reduction of (step (d)).

[0487] Sentence 75: NO in the first reaction zone X The method of sentence 73, wherein the reduction catalyst comprises a conventional SCR catalyst, preferably based on V2O5-WO3- / TiO2.

[0488] Sentence 76: The method of sentence 73 or 74, wherein the temperature of the off-gas entering the first reaction zone is 400°C or less, preferably 350°C or less.

[0489] Sentence 77: A method according to any of sentences 73 to 75, wherein the NO 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.

[0490] Sentence 78: The method of any of sentences 73 to 76, 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.

[0491] Sentence 79: NO in the first reaction zone X 78. The method of any of sentences 73 to 77, 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.

[0492] Sentence 80: The method of any of sentences 73 to 78, 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.

[0493] Sentence 81: The method of any of sentences 73 to 79, wherein the temperature of the off-gas entering the first reaction zone is 600°C or less, more preferably 550°C or less.

[0494] Sentence 82: The N2O decomposition catalyst in the second reaction zone X 81. The method of any of sentences 73 to 80, comprising a sensitive N2O decomposition catalyst.

[0495] Sentence 83: The method of any of sentences 73 to 81, 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.

[0496] Sentence 84: The method of any of sentences 73 to 82, wherein the temperature of the off-gas entering the second reaction zone is 600°C or less, preferably 550°C or less.

[0497] Sentence 85: 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 84. The method of any of sentences 73 to 83, having a content and an N2O content in the range of 200 to 2000 ppmv.

[0498] Sentence 86: The off-gas after leaving the first reaction zone and before entering the second reaction zone has a NO content of 20 ppmv or less, more preferably 10 ppmv or less, and even more preferably 5 ppmv or less. X 85. The method of any of sentences 73 to 84, having a N2O content in the range of 200 to 2000 ppmv.

[0499] Sentence 87: The off-gas treatment system comprises a first reaction zone and a second reaction zone, the off-gas is continuously passed through the second reaction zone beyond 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 via an N2O decomposition catalyst (step (c1)), 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 (c1)). X The content is NO X NO by reducing agents via reduction catalysts X (step (d)), and the N2O content in the off-gas is optionally further reduced by further decomposition of N2O via an N2O decomposition catalyst (step (c1)) and / or by chemical reduction of N2O with a reducing agent via an N2O reduction catalyst (step (c2)).

[0500] Sentence 88: The method of sentence 86, wherein no reducing agent is added to the off-gas upstream of the first reaction zone.

[0501] Sentence 89: The method of sentence 86 or 87, wherein the NO decomposition catalyst in the first reaction zone comprises a zeolite 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.

[0502] Sentence 90: The N2O decomposition catalyst in the first reaction zoneX 89. The method of any of sentences 86 to 88, comprising a sensitive N2O decomposition catalyst.

[0503] Sentence 91: NO in the second reaction zone X 89. The method of any of sentences 86 to 89, 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.

[0504] Sentence 92: A method according to any of sentences 86 to 90, 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.

[0505] Sentence 93: A method according to any of sentences 86 to 91, wherein in the second reaction zone, the N2O content in the off-gas is further reduced by at least 30%, preferably at least 40%, and more preferably at least 50%, based on the N2O content in the off-gas entering the second reaction zone.

[0506] Sentence 94: A method according to any of sentences 86 to 92, wherein in a 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 (c2)).

[0507] Sentence 95: The method of any of sentences 73 to 93, wherein the first reaction zone and the second reaction zone are spatially separated.

[0508] Sentence 96: The method of any of sentences 73 to 94, wherein the first reaction zone and the second reaction zone are spatially connected.

[0509] Sentence 97: The method of any of sentences 73 to 95, wherein the first reaction zone and the second reaction zone are disposed within a shared vessel.

[0510] Sentence 98: The method of any of sentences 73 to 96, wherein the off-gas temperature in the first reaction zone and the second reaction zone is 500°C or less, preferably in the range of 350 to 450°C.

[0511] Sentence 99: The method of any of sentences 73 to 97, wherein the space velocity in the first reaction zone is 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.

[0512] Sentence 100: The method of any of sentences 73 to 98, wherein the space velocity in the first reaction zone is 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 than the space velocity in the second reaction zone.

[0513] Sentence 101: The method of any of sentences 73 to 99, wherein 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, and especially at least 650°C.

[0514] Sentence 102: The method of any of sentences 73 to 100, wherein the temperature in 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, and especially at most 400°C.

[0515] Sentence 103: The method of any of sentences 73 to 101, wherein the temperature in the first reaction zone is relatively higher than the temperature in the second reaction zone 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.

[0516] Sentence 104: The method of any of sentences 73 to 102, wherein the temperature in the first reaction zone is relatively higher than the temperature in the second reaction zone by at least 120°C, more preferably at least 140°C, even more preferably at least 160°C, most preferably at least 180°C, and especially at least 200°C.

[0517] Sentence 105: The off-gas exits the off-gas treatment system and contains 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.

[0518] Sentence 106: The method of any of the preceding sentences, wherein the off-gas exits the off-gas treatment system and has a residual NO 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, and most preferably at most 5.0 ppmv, especially at most 2.5 ppmv.

[0519] Sentence 107: 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.

[0520] Sentence 108: The method of any of the preceding sentences, wherein the N2O decomposition catalyst is in particulate form and comprises at least 50 particles.

[0521] Sentence 109: 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.

[0522] Sentence 110: The method of any of the preceding sentences, wherein the N2O reduction catalyst is in particulate form and comprises at least 50 particles.

[0523] Sentence 111: 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.

[0524] Sentence 112: NO X The method of any of the preceding sentences, wherein the reduction catalyst is in particulate form and comprises at least 50 particles.

[0525] Sentence 113: The method of any of the preceding sentences, wherein at least one parameter characteristic of a current operating state of the baking system is measured in the baking system as the first measurement variable.

[0526] Sentence 114: The method of sentence 112, wherein the first measurement variable is selected from the group consisting of combustion temperature, NH3 consumption, rotation speed, if appropriate, and volume of the firing system.

[0527] Sentence 115: A method as recited in any of the preceding sentences, wherein at least one parameter characteristic of the current state of the off-gas before entering the off-gas treatment system is measured as a second measurement variable before entering the off-gas treatment system.

[0528] Sentence 116: 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.

[0529] Sentence 117: A method according to any of the preceding sentences, wherein at least one parameter characteristic of the current state of the off-gas exiting the exhaust gas treatment system is measured as a third measurement variable as it exits the exhaust gas treatment system.

[0530] Sentence 118: 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.

[0531] Sentence 119: 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 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 a 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.

[0532] Sentence 120: 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.

[0533] Sentence 121: A method according to any of sentences 112 to 119, wherein the control of the method is based on a first measured variable and / or a second measured variable and / or a third measured variable and / or a fourth measured variable by controlled changes in the manipulated variables.

[0534] Sentence 122: The method of sentence 120, wherein the manipulated variable is the amount of metered reducing agent.

[0535] Sentence 123: An apparatus configured to carry out a method as described in any of the preceding sentences, comprising: (i) an NH3-powered calcination system, preferably an NH3-driven internal combustion engine, an NH3-driven gas turbine, or a furnace for cracking NH3 into N2 and H2; and (ii) an off-gas treatment system. [Explanation of symbols]

[0536] G generator V compressor GT Gas Turbine VK combustion chamber AB Offgas Treatment System ADE1 First Waste Heat Steam Generator ADE2 No. 2 waste heat steam generator K1 First catalyst bed K2 Second catalyst bed WT heat exchanger DT steam turbine SS chimney

Claims

1. NH ３ NO in the off-gas of a combustion system, preferably a gas turbine Ｘ and N ２ 1. A method for reducing the content of O, comprising the steps of: (a) providing NH3 for the operation of said firing system, preferably a gas turbine; ３ 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) transferring the off-gas to an off-gas treatment system; (c) N in the off-gas ２ The O content is (c １ ) N ２ N via O decomposition catalyst ２ decomposing O, and / or (c ２ ) N ２ O reduction catalyst to reduce N ２ Chemically reduce O and reducing the (d) NO Ｘ NO by reducing agent through reduction catalyst Ｘ NO in the off-gas by chemical reduction of Ｘ Reducing the content; A method comprising:

2. Said NH ３ The operating firing system is NH ３ The method of claim 1 , wherein the fuel is a gas turbine.

3. The method of claim 2 wherein the gas turbine is combined with a steam turbine.

4. 4. The method of claim 2 or 3, wherein the gas turbine is part of a power plant.

5. The method of claim 4 , wherein the power plant generates electricity and / or district heating.

6. 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.

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

8. NH ３ is combusted in step (a) in a mixture with a further combustible gas, preferably the further combustible gas (i)H ２ 、 (ii) fossil fuels, preferably hydrocarbons and hydrocarbon mixtures, more preferably methane, ethane, propane, butane, natural gas, gasoline and / or diesel; (iii) alcohol, preferably methanol and / or ethanol; and mixtures thereof The method according to any one of claims 1 to 7, wherein the compound is selected from the group consisting of:

9. NH ３ In step (a), H ２ 9. The method according to claim 1, wherein the combustion is carried out in a mixture with

10. Step (a) (a １ ) NH ３ by thermal and / or catalytic cracking to produce N ２ , H ２ and optionally residual NH ３ a component step of generating a cracking gas comprising: (a ２ Optionally, the cracking gas is further treated with NH ３ Mixed with H ２ and N.H. ３ a constituent step of generating a mixture comprising: (a ３ ) the component step of combusting said cracking gas or said mixture; 10. The method of claim 9, comprising:

11. The H ２ is at most 50% by volume, and the combustion is carried out at an air ratio λ preferably in the range of 2.0 to 3.0, more preferably 2.1 to 2.9, even more preferably 2.2 to 2.

8.

12. The H ２ 11. The method according to claim 9 or 10, wherein the proportion of is higher than 50% by volume, and the combustion is carried out at an air ratio λ preferably in the range of 2.5 to 3.5, more preferably 2.6 to 3.4, even more preferably 2.7 to 3.

3.

13. NH ３ is CH ４ 13. The method of claim 1, wherein the combustion is carried out in step (a) in a mixture with

14. CH ４ is at most 50% by volume, and the combustion is carried out at an air ratio λ in the range of 1.5 to 2.5, more preferably 1.6 to 2.4, even more preferably 1.7 to 2.

3.

15. CH ４ 14. The method according to claim 13, wherein the proportion of is greater than 50% by volume and the combustion is carried out at an air ratio λ in the range of 2.0 to 3.0, more preferably 2.1 to 2.9, even more preferably 2.2 to 2.

8.

16. NH ３ is combusted alone in step (a), thus NH ３ 8. The method of claim 1, wherein is the only combustible gas combusted.

17. 17. The method of claim 16, wherein the combustion is carried out at an air ratio λ in the range of 1.0 to 1.5, more preferably 1.1 to 1.4, even more preferably 1.1 to 1.

3.

18. 18. The method of any one of claims 1 to 17, wherein off-gas is produced in step (a) at a temperature in the range of 1000 to 1500°C.

19. 19. The method of any one of claims 1 to 18, wherein the off-gas produced in step (a) is at a pressure in the range of 10 to 32 bar.

20. NO at most 5.0%, more preferably at most 4.0%, even more preferably at most 3.0%, most preferably at most 2.0%, especially at most 1.0%, and in some cases at most 0.5% Ｘ 20. The method of any one of claims 1 to 19, wherein an off-gas having an oxidation degree of

21. 21. The method of any one of claims 1 to 20, wherein the off-gas produced in step (a) is expanded through a gas turbine.

22. 22. The method of claim 21, wherein the off-gas at the outlet from the gas turbine is at a temperature in the range of 450 to 670°C.

23. 23. A method according to claim 21 or 22, wherein the off-gas at the outlet from the gas turbine is at a pressure higher than atmospheric pressure, i.e. ≥ 1.0 bara, but at most 1.2 bara, preferably at most 1.1 bara.

24. The off-gas at the outlet from the gas turbine contains NO in the range of 500 to 3000 ppmv. Ｘ 24. The method of any one of claims 21 to 23, having a content of

25. The off-gas at the outlet from the gas turbine has a concentration in the range of 1.0 to 6.0 vol.% O ２ 25. The method of any one of claims 21 to 24, having a content of

26. The off-gas at the outlet from the gas turbine contains H in the range of 20 to 30% by volume. ２ 26. The method of any one of claims 21 to 25, having an O content.

27. The off-gas at the outlet from the gas turbine contains a maximum of 500 ppmv, more preferably a maximum of 200 ppmv, and even more preferably a maximum of 100 ppmv of N ２ 27. The method of any one of claims 21 to 26, having an O content.

28. The off-gas at the outlet from the gas turbine contains at least 5 ppmv, more preferably at least 20 ppmv, and even more preferably at least 50 ppmv of N ２ 28. The method of any one of claims 21 to 27, having an O content.

29. The off-gas at the outlet from the gas turbine has a maximum NH ３ 29. The method of any one of claims 21 to 28, having a content of

30. The off-gas at the outlet from the gas turbine contains at least 10 ppmv, more preferably at least 50 ppmv, and even more preferably at least 100 ppmv NH ３ 30. The method of any one of claims 21 to 29, having a content of

31. The off-gas at the outlet from the gas turbine contains at most 10%, more preferably at most 9.0%, even more preferably at most 8.0%, most preferably at most 7.0%, in particular at most 6.0%, and in some cases at most 5.0% NO Ｘ The degree of oxidation (n(NO ２ ) / (n(NO)+n(NO) ２ 31. The method of any one of claims 21 to 30, wherein

32. NH ３ is CH ４ and CO. ２ 32. The method of any one of claims 1 to 31, further comprising, preferably also HCN.

33. 33. The method of claim 32, wherein the off-gas at the outlet from the gas turbine has an HCN content of at least 5 ppmv, more preferably at least 10 ppmv, even more preferably at least 50 ppmv.

34. 34. A method according to claim 32 or 33, wherein the off-gas at the outlet from the gas turbine has an HCN content of maximum 1000 ppmv, more preferably maximum 500 ppmv, even more preferably maximum 200 ppmv, and most preferably maximum 100 ppmv.

35. 35. The method of any one of claims 1 to 34, wherein at least one heat exchanger in which the off-gas is cooled is arranged downstream of the gas turbine in a flow direction of the off-gas and upstream of the off-gas treatment system.

36. 36. The method of claim 35, wherein the temperature of the off-gas at the outlet from the heat exchanger is at most 550°C, more preferably at most 525°C, even more preferably at most 500°C.

37. 37. A method according to claim 35 or 36, wherein the temperature of the off-gas at the outlet from the heat exchanger is at least 400°C, more preferably at least 425°C, even more preferably at least 450°C.

38. Step (c) １ ) 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 38. The method of any one of claims 1 to 37, 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.

39. Step (c) 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 39. The method of any one of claims 1 to 38, 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.

40. Step (c ２ ) The reducing agent in ３ , hydrocarbons, CO, H ２ and mixtures thereof, preferably NH ３ 40. The method of any one of claims 1 to 39, wherein

41. Step (c 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 41. The method of any one of claims 1 to 40, wherein

42. Step (c ２ The reducing agent in ２ 42. The method according to any one of claims 1 to 41, 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.

43. 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.

44. The reducing agent in step (d) is NH ３ , hydrocarbons, CO, H ２ and mixtures thereof, preferably NH ３ 44. The method of any one of claims 1 to 43, wherein

45. The reducing agent in step (d) 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 45. The method of any one of claims 1 to 44, wherein

46. Step (c ２ The reducing agent in step (d) is the same as the reducing agent in step (d), preferably NH ３ 46. ​​The method of any one of claims 1 to 45, wherein

47. 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: (c １ ) N in the off-gas ２ The O content is ２ reduced by catalytic decomposition of O, and (d) 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: (c ２ ) residual N ２ O content is NH ３ by N ２ reduced by catalytic chemical reduction of O, (c1*) Residual N ２ The O content is ２ Optionally reduced by catalytic decomposition of O, and (d*) Residual NO Ｘ The content is NH ３ No by Ｘ reduced by catalytic chemical reduction of 47. The method of any one of claims 1 to 46.

48. N in the first catalyst bed ２ The catalytic decomposition of NO present in the off-gas Ｘ 48. The method of claim 47, wherein the method is co-catalyzed by

49. 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 49. The method of claim 47 or 48, resulting in a content.

50. 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 50. The method according to any one of claims 47 to 49, wherein the actual concentration of is measured (actual value) and, if there is a difference between a setpoint and the actual value (control difference), the output of the first control valve is changed to minimize said difference.

51. The additional NH ３ is the amount of NO leaving the first catalyst bed Ｘ 51. The method according to claim 50, wherein the residual concentration of is selected to be at most 1000 ppmv, preferably at most 500 ppmv, more preferably at most 100 ppmv.

52. The additional NH ３ is the amount of NO leaving the first catalyst bed Ｘ 52. The method of claim 50 or 51, wherein the residual concentration of is selected to be at least 10 ppmv, preferably at least 20 ppmv, more preferably at least 40 ppmv.

53. 53. The method of any one of claims 47 to 52, wherein the temperature of the off-gas at the outlet from the first catalyst bed is in the range of 400 to 550°C.

54. 54. A method according to any one of claims 47 to 53, wherein the off-gas at the outlet from the first catalyst bed is at a pressure above atmospheric pressure, i.e. ≥ 1.0 bara, but at a maximum of 1.2 bara, more preferably at a maximum of 1.1 bara.

55. The off-gas leaving the first catalyst bed is 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 Ｘ 55. The method of any one of claims 47 to 54, wherein the oxidation degree is

56. The off-gas at the outlet from the first catalyst bed is in the range of 30% to 50% NO Ｘ 56. The method of any one of claims 47 to 55, wherein the oxidation degree is

57. The off-gas at the outlet from the first catalyst bed is in the range of 15% to 35% NO Ｘ 56. The method of any one of claims 47 to 55, wherein the oxidation degree is

58. The off-gas at the outlet from the first catalyst bed is in the range of 10% to 20% NO Ｘ 56. The method of any one of claims 47 to 55, wherein the oxidation degree is

59. The off-gas at the outlet from the first catalyst bed is in the range of 5% to 15% NO Ｘ 56. The method of any one of claims 47 to 55, wherein the oxidation degree is

60. 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 60. The method of any one of claims 47 to 59, wherein O is decomposed in the second catalyst bed to a residual concentration of O.

61. Residual NO Ｘ but the 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 61. The method of any one of claims 47 to 60, wherein the hydroxybenzoates are decomposed in the second catalyst bed to a residual concentration of

62. 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 said first catalyst bed and ３ The amount of off-gas entering the second catalyst bed is taken into account to calculate the required amount of NH ３ 62. The method of any one of claims 47 to 61, wherein the method is used to vary the output of the second control valve to meter the required amount of

63. NH entering the second catalyst bed ３ / (NO Ｘ +N ２ 63. The process according to any one of claims 47 to 62, 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.

64. NH entering the second catalyst bed ３ / NO Ｘ 64. The process according to any one of claims 47 to 63, 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.

65. NH entering the second catalyst bed ３ / N ２ 65. The process of any one of claims 47 to 64, 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.

66. The further NH ３ 66. The method of any one of claims 47 to 65, wherein the first and second electrodes are not dispensed under feedback control by the second device.

67. The amount of catalyst is determined by the N ２ Based on the concentration of O, ２ 67. The process of any one of claims 47 to 66, 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.

68. The amount of the catalyst and the additional NH ３ is the amount of NO upon exiting the first catalyst bed. Ｘ / N ２ 68. The method of any one of claims 47 to 67, wherein the molar ratio of O is selected to be at least 5, more preferably at least 10, and even more preferably at least 20.

69. The space velocity of the first catalyst bed is 5000 h －１ From 100,000 hours －１ , more preferably 10,000 h －１ From 50,000 hours －１ , and even more preferably 15000h －１ From 45,000 hours －１ 69. The method of any one of claims 47 to 68, wherein the

70. NO exiting the first catalyst bed Ｘ / N ２ O molar ratio of at least 10, and further NH ３ The metered addition of the incoming NO Ｘ 70. The method of any one of claims 47 to 69, wherein the method is carried out only with respect to the amount of

71. 71. The method of any one of claims 47 to 70, 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.

72. 72. The method of any one of claims 47 to 71, 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.

73. 73. The method of any one of claims 47 to 72, 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.

74. The space velocity of the second catalyst bed is 5000 h －１ From 100,000 hours －１ , more preferably 10,000 h －１ From 50,000 hours －１ , and even more preferably 15000h －１ From 45,000 hours －１ 74. The method of any one of claims 47 to 73, wherein the

75. The catalyst volume V2 of the second catalyst bed ｃａｔ the catalyst volume V1 of the first catalyst bed relative to ｃａｔ Catalyst volume ratio (V1 ｃａｔ / V2 ｃａｔ 75. The method of any one of claims 47 to 74, wherein the ratio of the hydroxyl group to the total hydroxyl group 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.

76. The following conditions are met: the pressure of the off-gas entering the first catalyst bed is at most 5 bara, 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; - the first catalyst bed comprises an Fe zeolite; - the second catalyst bed comprises an Fe zeolite; - the off-gas passes through a temperature control device in which its temperature is regulated 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 leaving 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; 76. The method of any one of claims 47 to 75, wherein at least one, more than one, or all of the following are satisfied:

77. 77. The method of any one of claims 1 to 76, wherein the off-gas treatment system comprises a first waste heat steam generator, preferably a second waste heat steam generator, and the first waste heat steam generator may be positioned upstream of the second waste heat steam generator in a flow direction of the off-gas.

78. 78. The method of any one of claims 47 to 77, wherein the off-gas treatment system comprises a first waste heat steam generator and a second waste heat steam generator, the first waste heat steam generator being positioned upstream of the second waste heat steam generator in a flow direction of the off-gas.

79. 79. The method of claim 78, wherein the off-gas flows first through the first waste heat steam generator, then through the first catalyst bed, then through the second catalyst bed, and finally through the second waste heat steam generator.

80. 79. The method of claim 78, wherein the off-gas flows first through the first waste heat steam generator, then through the first catalyst bed, then through the second waste heat steam generator, and finally through the second catalyst bed.

81. 79. The method of claim 78, wherein the off-gas flows first through the first catalyst bed, then through the first waste heat steam generator, then through the second catalyst bed, and finally through the second waste heat steam generator.

82. 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

83. 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.

84. 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.

85. (i) NH ３ a driving gas turbine; (ii) an off-gas treatment system; and Equipped with 85. Apparatus configured to carry out the method of any one of claims 1 to 84.

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