Starting up a plant for catalytically decomposing ammonia

Abstract

The present invention relates to a plant for preparing H2 by catalytically decomposing NH3. The plant according to the present invention can be operated in a start-up mode to heat the plant equipment to a raised operating temperature using a heat transfer medium, for example, following an interruption in continuous operation of the plant due to maintenance work. After heating to the operating temperature, the plant according to the present invention can be operated in a production mode for continuous production of H2. The present invention also relates to a method for starting a plant for preparing H2 by catalytically decomposing NH3.

Description

[Technical Field]

[0001] The present invention relates to a plant for producing H2 by catalytic decomposition of NH3 to obtain H2 and N2. The plant of the present invention can be operated in a start-up mode to heat the plant equipment to a high operating temperature using a heat transfer medium after interruption of continuous operation of the plant, for example, due to maintenance work. After heating to the operating temperature, the plant of the present invention can be operated in a production mode for continuous production of H2. The present invention further relates to a method for starting a plant for producing H2 by catalytic decomposition of NH3. [Background technology]

[0002] H2 can be obtained from H2O using renewable energy and then converted to NH3 using N2. NH3 can be stored and transported much more safely than H2. NH3 can then be broken down again into H2 and N2. After being separated from N2, H2 finds a wide range of industrial applications.

[0003] The decomposition of NH3 into N2 and H2 is an endothermic reaction in which the molar amount doubles (2NH3 → N2 + 3H2) (ΔH° = 45.9 kJ·mol). -1 Therefore, the reaction is generally favored at high temperatures and low pressures. The higher the pressure, the higher the temperature must be to achieve a satisfactory reaction yield. On an industrial scale, the catalytic decomposition of NH3 to N2 and H2 occurs in the gas phase at high temperatures and moderate pressures.

[0004] The stored NH3 is in liquid form in a refrigerated tank at atmospheric pressure and -32.8°C. A pump is used to supply NH3 to the system at system pressure. As the system pressure increases, the boiling point of NH3 rises, for example, to about 62.2°C at 27.8 bara. To convert NH3 to the gas phase, evaporation of NH3 requires a heat supply. The evaporated NH3 is then further heated until it reaches a sufficiently high temperature to be decomposed on an NH3 decomposition catalyst.

[0005] Known methods for catalytically decomposing NH3 into N2 and H2 require a considerable amount of heat supply. Firstly, heat is needed to bring the process gas and the NH3 decomposition catalyst to a sufficiently high temperature to achieve a satisfactory conversion rate. Secondly, heat is needed to maintain the endothermic decomposition reaction.

[0006] In industrial-scale processes, this heat is usually supplied by the combustion of energy carriers (e.g., U.S. Patent No. 4704267; French Patent Application Publication No. 1469045A; Chinese Patent Application Publication No. 111957270; Chinese Patent Application Publication No. 113896168; International Publication No. 2001 / 087770A1; International Publication No. 2011 / 107279A1; International Publication No. 2017 / 160154A1; International Publication No. 2019 / 038251A1; International Publication No. 2012 / 03 See International Publication No. 9183A1; International Publication No. 2012 / 090739A1; International Publication No. 2020 / 095467A; International Publication No. 2021 / 257944A1; International Publication No. 2022 / 096529A1; International Publication No. 2022 / 243410A1; International Publication No. 2022 / 265647A1; International Publication No. 2022 / 265648A1; International Publication No. 2022 / 265649A1; International Publication No. 2022 / 265650A1; International Publication No. 2022 / 265651A1). In principle, all energy carriers, such as natural gas or mixtures of NH3 and H2, are useful.

[0007] Plants for producing H2 from NH3 typically operate continuously for extended periods without interruption, such as weeks or months. However, such plants may need to be put into standby mode for purposes such as safety checks, catalyst material replacement, or other maintenance work. In standby mode, the system cools to ambient temperature depending on the duration of the operational interruption.

[0008] To convert such a plant from standby to continuous operation, it must first be heated to the operating temperature, and NH3 cannot be decomposed at room temperature. Different parts of the plant typically have different operating temperatures and therefore require different degrees of heating. Heating can, in principle, be achieved by passing a heat transfer medium, such as N2, steam, natural gas, or a mixture thereof, through the process side of the plant and initiating the combustion of an energy carrier to supply heat to the heating process. Depending on its properties, the heat transfer medium can be circulated or incinerated by flare.

[0009] To reduce or completely avoid the use of fossil fuels, during normal plant operation, a portion of NH3 is burned instead of fossil fuels, and the resulting heat of combustion is used for heating. NH3 is, firstly, a reactant for the decomposition process, and secondly, an energy carrier for generating the necessary heat. However, since NH3 burns only incompletely in a mixture with air, burning only pure NH3 with combustion air is disadvantageous. As a result, unburned NH3 is emitted, which is unacceptable. To improve the combustibility when burning NH3 with combustion air, a predetermined amount of H2 produced is added to the proportion of NH3 burned during normal plant operation.

[0010] However, a major problem is that H2 cannot be used as a decomposition product during plant startup.

[0011] In principle, this problem can be resolved through temporary measures during the plant's startup period and will be terminated once normal operation is achieved. (i) generating heat by burning natural gas or propane; H2 is not required for this purpose, but CO2 emissions are produced; or (ii) Provide H2 on a small scale, then, for example, - To generate H2 using an electric heating device for catalytic decomposition of NH3; - The production of H2 by the electrolysis of water; or - Utilizing H2 stored from previous production, This causes H2 to burn in a mixture with NH3.

[0012] However, these approaches to finding solutions have various drawbacks.

[0013] Alternative combustion of natural gas or propane not only results in undesirable CO2 emissions but also requires dual operation, particularly in the combustion of the energy carrier. Since burner configurations typically need to be adapted to the energy carrier, switching from natural gas / propane to NH3 / H2 requires configuration changes or the installation of a second, separate combustion device.

[0014] The small-scale transient generation of H2 using separate catalytic decomposition devices or electrolytic cells requires considerable additional equipment complexity. This is also true for the storage of H2, which further presents a number of safety concerns.

[0015] International Publication No. 2011 / 150370A2 relates to the decomposition of NH3 into an H2 gas mixture, wherein an NH3-rich gas mixture of NH3 and air enters a conduit in which the combustion and decomposition of a portion of the mixture is initiated, releasing heat and H2. The H2 mixes with the majority of the gas mixture, and the released heat propels the combustion reaction. When starting the NH3 flame cracker, the catalyst can be heated electrically, inductively, by a brief combustion of the catalyst and / or surrounding structural chemicals, or by an electric arc. Heating the catalyst can be used to initiate the combustion and decomposition reaction of NH3 and to supply heat to the combustion gases as needed until the NH3 flame cracker is fully heated. After the NH3 flame cracker has started, the power can be turned off or reduced so that the energy required to decompose the NH3 is essentially provided by the combustion of a portion of the NH3, and that the combustion of NH3 is essentially sufficient to keep the catalyst at a high temperature.

[0016] International Publication No. WO 2013 / 119281 A1 relates to the decomposition of NH3 in an NH3-rich gas mixture of NH3 and air into a H2-containing gas mixture entering a heat exchanger. A part of the NH3 is combusted and the remainder is decomposed to obtain the H2-containing gas mixture. The NH3 frame cracker can be brought to the operating temperature by combusting the starting mixture and subsequently passing the combusted starting mixture through the NH3 frame cracker, as a result of which the combusted starting mixture is in thermal contact with the heat exchanger and / or the burner of the NH3 frame cracker during the starting phase. Since the surface temperature rises during the heating phase, one or more of the following measures can be taken: increasing the total flow rate of the starting mixture, decreasing the oxygen content of the oxidant component, or increasing the total content of the starting mixture. As a result, the NH3 frame cracker can be started quickly even when the flow rate of the purified oxygen is relatively low. The flow of purified oxygen is shut off at the end or towards the end of the starting phase.

[0017] Plants and methods known from the prior art for obtaining H2 from NH3 are not satisfactory in all respects, especially with regard to the interruption of normal operation and the subsequent start-up of the plant. Therefore, improved plants and methods that can be economically implemented on an industrial scale are needed.

Prior Art Documents

Patent Documents

[0018]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

[0019] The object of the present invention is to provide a favorable plant and method for producing H2 from NH3 that overcomes the aforementioned drawbacks. The plant should be able to start up without additional costly means and equipment, should not be based on fossil fuels, should not involve additional safety risks, and should be possible on an economical and industrial scale. [Means for solving the problem]

[0020] This objective is achieved by the subject matter of the claims.

[0021] Surprisingly, it was found that certain devices that serve other purposes during the normal operation of the plant can be recycled and interconnected differently during the start-up period. In this way, even during plant startup, a sufficient amount of H2 can be obtained from NH3 by decomposition, the combustion of NH3 can be started with a mixture of NH3 and H2, and the plant can be gradually heated to operating temperature. Thus, the complexity of additional equipment for plant startup is minimized.

[0022] A first aspect of the present invention is a plant for producing H2 from NH3, The plant is capable of operating in manufacturing mode (normal operation) at the operating temperature. The plant is capable of operating in a start-up mode (start-up operation) to heat at least one of its components from the start-up temperature to the operating temperature. For the start-up mode, the plant has at least the following devices for heating at least one device to operating temperature: - Heating element for heating NH3; - A first NH3 decomposition device (pre-reactor) located downstream of the heating element in the NH3 flow direction, for partially catalytically decomposing heated NH3 to produce a combustion gas containing H2, N2, and residual NH3; -Optionally, a device for metering and supplying combustion air into the combustion gas downstream of the first NH3 decomposition device (pre-reactor) in the direction of combustion gas flow; - A combustion device located downstream of the first NH3 decomposition device in the direction of combustion gas flow, for burning the combustion gas to produce combustion heat and combustion exhaust gas; - A compressor for compressing a heat transfer medium; and - Downstream of the combustion device in the flow direction of the combustion exhaust gas, and downstream of the compressor in the flow direction of the heat transfer medium, To heat the heat transfer medium by absorbing heat from the combustion exhaust gas. - A first heat exchanger [preferably a combustion exhaust gas / heat transfer medium heat exchanger for the start-up mode], and / or - Second heat exchanger [preferably a combustion exhaust gas / heat transfer medium heat exchanger for the start-up mode] Equipped with, The present invention relates to a plant in which at least one device of the plant is located downstream of a first heat exchanger and / or a second heat exchanger in the flow direction of the heat transfer medium and is in fluid communication with the heat transfer medium for the absorption of heat from the heat transfer medium.

[0023] A second aspect of the present invention relates to the use of the plant of the present invention for the production of H2.

[0024] A third aspect of the present invention is a method for starting a plant for producing H2 from NH3, (a) optionally, a step of evaporating water to generate steam, (b) Optionally, a step of evaporating liquid NH3 by heat absorption from the vapor, (c) A step of heating NH3, (d) A step of partially catalytically decomposing heated NH3 in a first NH3 decomposition device to produce a combustion gas containing H2, N2 and residual NH3, (e) Optionally, a step of metering and supplying combustion air into the combustion gas, (f) A process of burning combustion gas in a combustion device to produce combustion heat and combustion exhaust gas, (g) A step of compressing the heat transfer medium, (h) A step of heating the heat transfer medium by absorbing heat from the combustion exhaust gas, The present invention relates to a method comprising (i) heating at least one device of a plant by absorbing heat from a heat transfer medium.

[0025] Steps (a), (b), and (e) of the method of the present invention are independent and optional. If steps (a) to (i) are carried out, they are preferably performed in alphabetical order. [Brief explanation of the drawing]

[0026] [Figure 1] A preferred embodiment of the plant of the present invention, which can carry out a preferred embodiment of the method of the present invention, is shown in the form of a flowchart. Figure 1 is a schematic diagram of such a process configuration. [Figure 2] A preferred embodiment of the plant of the present invention, which can carry out a preferred embodiment of the method of the present invention, is shown in the form of a flowchart. Figure 2 shows a preferred device according to the present invention. [Figure 3] A preferred embodiment of the plant of the present invention, which can carry out a preferred embodiment of the method of the present invention, is shown in the form of a flowchart. Figure 3 shows a preferred modified example of the plant of the present invention according to Figure 2. [Modes for carrying out the invention]

[0027] According to the present invention, a manufacturing mode (normal operation) and a starting mode (startup operation) are distinguished. In the starting mode, H2 is produced from NH3 to a certain extent, but it is preferable that there is a considerable difference in the amount and yield of H2 produced.

[0028] In the starting mode, it is preferable that both the amount and yield of H2 produced are relatively low. Preferably, only the first NH3 decomposition device is used for the partial catalytic decomposition of NH3, and the produced intermediate product gas is burned as a combustion gas to generate the required heat.

[0029] In the production mode, it is preferable that both the amount and yield of H2 produced are relatively high. Both the first NH3 decomposition device (preliminary reactor) and the downstream second NH3 decomposition device (main reactor) are preferably used for very substantially complete catalytic decomposition of NH3. The intermediate product gas produced in the first NH3 decomposition device is not burned as a combustion gas, but is preferably supplied after heating of the downstream second NH3 decomposition device, where very substantially complete decomposition of NH3 occurs. Then, preferably by pressure swing adsorption, H2 is separated from the product gas produced in the second NH3 decomposition device, and the resulting residual gas mixture is burned as a combustion gas to generate the required heat. In practice, the decomposition of NH3 in the second NH3 decomposition device does not proceed to completion (100.0%), so a residual amount of NH3 remains that is burned as a combustion gas after additional fresh NH3 is added by metering, if applicable.

[0030] The heat exchanger of the present invention is useful for transferring heat from one medium to another without mixing the mediums. For explanatory purposes, in relation to an "A / B heat exchanger," the heat dissipation medium A is mentioned first, followed by the heat absorption medium B. Thus, for example, a "combustion flue gas / NH3 heat exchanger" plays the role of releasing heat present in the combustion flue gas into NH3. For this purpose, the combustion flue gas / NH3 heat exchangers are interconnected in correspondence, i.e., the combustion flue gas flows through its higher temperature side and the NH3 flows through its lower temperature side.

[0031] For explanatory purposes, the heat exchangers are numbered. This numbering is for linguistic purposes only, and the existence of a higher-numbered heat exchanger, such as "the fourth heat exchanger," should not necessarily be understood as requiring the existence of all the lower-numbered heat exchangers ("the first heat exchanger," "the second heat exchanger," "the third heat exchanger," etc.). For example, the plant of the present invention may include the second heat exchanger and the fourth heat exchanger of the present invention, but may not include the first heat exchanger or the third heat exchanger of the present invention.

[0032] According to the present invention, one of the same heat exchangers in the manufacturing mode may perform a different function than in the starting mode, and is particularly preferable if other media can flow through them at least partially or on one side (hot side versus cold side). In such cases, for the purposes of explanation, the two operating modes and their respective preferred heat exchange configurations are distinguished in the following square brackets for each individual case. For example, “first heat exchanger [preferably a combustion flue gas / NH3 heat exchanger for the manufacturing mode; a combustion flue gas / heat transfer medium heat exchanger for the starting mode]” means that the first heat exchanger preferably takes on two different functions: in the manufacturing mode, heat is preferably released from the combustion flue gas to NH3 within the first heat exchanger. In the starting mode, it is preferable that heat is released from the combustion flue gas to the heat transfer medium within the first heat exchanger. If the heat transfer medium in the starting mode is NH3, then it is ultimately also a combustion flue gas / NH3 heat exchanger for the starting mode. When such a heat exchanger is described in the context of a specific mode (either a manufacturing mode or a startup mode), only the corresponding preferred heat exchange configuration may be referenced within the following square brackets.

[0033] For explanatory purposes, unless otherwise specified, the term "water" applies to all its physical states, and in such cases, depending on temperature and pressure, this water may be in liquid or gaseous form, or in a two-phase system, i.e., vapor. The same applies to "NH3".

[0034] The plant of the present invention comprises a first NH3 decomposition device and a second NH3 decomposition device, both of which contain an NH3 decomposition catalyst. The first NH3 decomposition device is preferably a fixed-bed reactor. In the first NH3 decomposition device, the decomposition of NH3 is preferably adiabatic. The downstream second NH3 decomposition device is preferably formed together with a combustion device in a manner similar to a primary reformer used in conventional steam reforming to produce H2, O2, and CO / CO2 from H2O and CH4.

[0035] In the manufacturing mode, catalytic cracking of NH3 proceeds in two stages in a first NH3 cracking device and a downstream second NH3 cracking device. Preferably, a second heat exchanger [preferably a combustion flue gas / intermediate product gas heat exchanger for the manufacturing mode] is located downstream of the first NH3 cracking device in the direction of NH3 flow, preferably upstream of the downstream second NH3 cracking device. In the manufacturing mode, the second heat exchanger preferably functions to heat the intermediate product gas after it has left the first NH3 cracking device and before it enters the downstream second NH3 cracking device (similar to a primary reformer, together with the combustion device, the main reactor). In the manufacturing mode, it is preferable that the intermediate product gas absorbs heat from the combustion flue gas in the second heat exchanger (see Figure 2, second heat exchanger 67).

[0036] In the production mode, preheated NH3 enters a first NH3 decomposition device, where partial catalytic decomposition of NH3 occurs to some extent, yielding N2 and H2. An intermediate product gas is formed, which still contains a considerable amount of undecomposed NH3, but also contains the already formed N2 and H2. As a result of the endothermic decomposition of NH3, the intermediate product gas is preferably cooled. Preferably, the conversion rate of the decomposed NH3 in the first NH3 decomposition device is up to 25%, more preferably up to 20%, of the total conversion rate achieved. Preferably, the conversion rate of the decomposed NH3 in the first NH3 decomposition device is at least 5%, more preferably at least 10%, and even more preferably at least 15% of the total conversion rate achieved. After leaving the first NH3 decomposition device, the intermediate product gas is preferably reheated in a second heat exchanger [preferably a combustion exhaust gas / intermediate product gas heat exchanger for the production mode] before entering a downstream second NH3 decomposition device. Next, in the second NH3 decomposition device, the residual decomposition of NH3 proceeds until the total conversion rate is achieved.

[0037] In contrast, in the startup mode, catalytic decomposition of NH3 preferably has only one step, performed by the first NH3 decomposition device. The second NH3 decomposition device preferably does not yet contribute to the decomposition of NH3 in the startup mode, at least during the initial stages of the startup mode.

[0038] In the starting mode, preheated NH3 enters the first NH3 decomposition device, where partial catalytic decomposition of NH3 occurs to some extent, yielding N2 and H2. An intermediate product gas is also formed, which still contains a considerable amount of undecomposed NH3, but also contains the already formed N2 and H2. Preferably, the conversion rate of decomposed NH3 in the first NH3 decomposition device is at most 25%, more preferably at most 20%, based on the amount of NH3. Preferably, the conversion rate of decomposed NH3 in the first NH3 decomposition device is at least 5%, more preferably at least 10%, and even more preferably at least 15%, based on the amount of NH3.

[0039] In contrast to the manufacturing mode, in the start-up mode, the intermediate product gas formed in the first NH3 decomposition device is preferably not introduced into the second NH3 decomposition device, but instead into the combustion device. The amount of H2 formed in the intermediate product gas is sufficient for sufficient combustion of NH3 so that the combustion of the intermediate product gas generates enough heat of combustion to gradually heat the plant to operating temperature.

[0040] In a preferred embodiment, the NH3 stream in the starting mode is divided into a first NH3 substream and a second NH3 substream. Only the first NH3 substream is supplied to the first decomposition device. Instead, the second NH3 substream flows through the second NH3 decomposition device, and as a result, heat is absorbed from the second NH3 substream by the second NH3 decomposition device. Thus, the second NH3 substream initially functions only as a heat transfer medium. In this way, by gradually heating the second NH3 decomposition device until it reaches the starting temperature (activation temperature) for catalytic decomposition of NH3, additional H2 is produced in the second NH3 decomposition device by catalytic decomposition of NH3 (see Figure 3).

[0041] In a preferred embodiment, the amount of H2 in the combustion gas increases in the start-up mode compared to the manufacturing mode. A higher ratio of H2 to NH3 promotes combustion and allows for a more rapid achievement of the operating temperature.

[0042] A key advantage of the present invention is that the first NH3 decomposition device can be used for two different purposes: a starting mode for generating combustion gases and a production mode for the first stage of a two-stage decomposition of whole NH3 for generating product gases. The plant of the present invention preferably does not include a further separate NH3 decomposition device used only in the starting mode but not in the production mode. Such separate NH3 decomposition devices are commercially available and may already have electric heating, but according to the present invention, it is also possible to avoid the complexity of such additional equipment.

[0043] Preferably, the plant of the present invention comprises essentially only two devices that are used only in the startup mode but not in the production mode, namely, - Preferably an electrically operated heating element, - Preferably, it includes an electrically operated H2O steam generator.

[0044] In order for NH3 to have a sufficiently high temperature for catalytic decomposition in the first NH3 decomposition device, the plant of the present invention has a heating element for heating NH3 for the start-up mode. The heating element is preferably electrically operated. Therefore, heating of NH3 in step (c) of the method of the present invention is preferably carried out using electrical energy.

[0045] The heating element is preferably provided only for the start-up mode and is switched off in the production mode. In a preferred embodiment, the heating element is interconnected in a bypass via a conduit system, and NH3 can pass through the heating element in the start-up mode via the bypass to be heated therein. Once the production mode is achieved, preferably there is no longer any flow of NH3 through the entire bypass including the heating element. To enable such a reaction regime, a suitable valve is preferably provided to allow a controlled flow of NH3 through or not through the bypass.

[0046] NH3 is typically supplied in liquid form as a starting material and therefore must be evaporated first. This applies not only to the manufacturing mode but also to the starting mode. According to the present invention, NH3 is preferably evaporated by the absorption of heat from the vapor.

[0047] In the manufacturing mode, it is preferable that the steam is supplied by process heat, in that water, acting as a heat transfer medium, absorbs heat from the product gas and / or combustion exhaust gas, and the steam thus heated releases heat into liquid NH3.

[0048] However, in the starting mode, there is initially no process heat, so the plant of the present invention preferably includes an H2O evaporator for evaporating water to generate steam. The H2O evaporator is preferably located upstream of the heating element in the direction of NH3 flow. The H2O evaporator is preferably electrically heated. Therefore, the method of the present invention preferably comprises two optional steps (a) and (b), preferably using electrical energy to generate steam in step (a) of the method of the present invention.

[0049] Preferably electrically heated H2O evaporators are provided only for the start-up mode and are switched off in the production mode. In a preferred embodiment, the H2O evaporators are interconnected within the bypass via a conduit system so that water can pass through the H2O evaporators in the start-up mode, where it can be heated and evaporated. Once the production mode is achieved, preferably there is no longer any flow of water through the entire bypass, including the H2O evaporators. To enable such a reaction regime, suitable valves are preferably provided to allow a controlled flow of water through or not through the bypass.

[0050] Furthermore, it is preferable that the plant of the present invention includes an NH3 evaporation device for evaporating liquid NH3 by absorbing heat from steam.

[0051] In this way, liquid NH3 can first evaporate in the starting mode by absorbing heat from the vapor, and then preferably in an electrically heated H2O evaporation device. The evaporated NH3 then passes through a preferably electrically heated heating element and is heated to a temperature sufficient for the subsequent partial catalytic decomposition of NH3 in a first NH3 decomposition device. The intermediate product gas thus produced is burned in a combustion device to generate combustion exhaust gas and combustion heat.

[0052] According to the present invention, the heat generated by the combustion of the combustion gas is used not only in the manufacturing mode but also in the starting mode. The combustion gas may typically have different origins and compositions.

[0053] In the production mode, reaction heat is supplied to the endothermic reaction in the first NH3 decomposition device and the downstream second NH3 decomposition device, and the combustion heat essentially helps to heat the NH3 to the required reaction temperature so that the reaction can be carried out with a high conversion rate using both NH3 decomposition devices. For this purpose, it is preferable to use vapor as a heat transfer medium, in particular for the evaporation of NH3.

[0054] In the starting mode, the heat of combustion essentially serves to heat a heat transfer medium that is compressed, preferably by a compressor, and then passes through the plant components. For this purpose, it is preferable that the heat transfer medium absorbs heat directly from the heat of combustion and / or indirectly from the combustion exhaust gas. For this purpose, it is preferable that the heat transfer medium is located downstream of the combustion device in the direction of the combustion exhaust gas flow and downstream of the compressor in the direction of the heat transfer medium flow. - First heat exchanger [preferably a combustion exhaust gas / heat transfer medium heat exchanger for the start-up mode] and / or - Second heat exchanger [preferably a combustion exhaust gas / heat transfer medium heat exchanger for the start-up mode] This is achieved by the arrangement of These devices are designed to heat a heat transfer medium by absorbing heat from combustion exhaust gases.

[0055] In a preferred embodiment, the heat transfer medium contains or is essentially made of N2. The N2 is preferably circulated through at least a portion of the plant until a desired operating temperature for the plant components is achieved. Once this state is reached, it is preferable that the N2 is discharged from the plant and the plant switches to manufacturing mode. This switching is preferably achieved by continuously adding NH3 to the N2 and, if necessary, incinerating the mixture of N2 and NH3 with a flare. The manufacturing mode can be initiated when the NH3 content in the mixture with N2 is sufficiently high.

[0056] In other preferred embodiments, the heat transfer medium includes or is essentially made of NH3. The NH3 is preferably circulated through at least part of the plant until a desired operating temperature for the plant components is achieved. Once this state is reached, the manufacturing mode is entered.

[0057] In a preferred embodiment, the NH3 stream in the starting mode is divided into a first NH3 substream and a second NH3 substream. Only the first NH3 substream is supplied to the first decomposition device. Instead, the second NH3 substream flows through the second NH3 decomposition device, and as a result, heat is absorbed from the second NH3 substream by the second NH3 decomposition device. Thus, the second NH3 substream initially functions only as a heat transfer medium. In this way, by gradually heating the second NH3 decomposition device until it reaches the starting temperature (activation temperature) for catalytic decomposition of NH3, additional H2 is produced in the second NH3 decomposition device by catalytic decomposition of NH3.

[0058] In a preferred embodiment, the amount of H2 in the combustion gas increases in the start-up mode compared to the manufacturing mode. A higher ratio of H2 to NH3 promotes combustion and allows for a more rapid achievement of the operating temperature.

[0059] In the startup mode, at least one device of the plant is located downstream of the first and / or second heat exchangers in the flow direction of the heat transfer medium and is in fluid communication with the heat transfer medium for heat absorption from the heat transfer medium. This at least one device of the plant is heated in the startup mode by heat absorption from the heat transfer medium.

[0060] In a preferred embodiment, at least one device heated in the start-up mode by heat absorption from a heat transfer medium is a second NH3 decomposition device (see Figure 2, second NH3 decomposition device 24). In the production mode, the second NH3 decomposition device is preferably located downstream of the first NH3 decomposition device and preferably assists in the catalytic decomposition of evaporated NH3, producing a product gas containing H2 and N2. For switching from the start-up mode to the production mode, the plant of the present invention preferably includes corresponding conduits and valves that enable modified interconnections (see Figure 2).

[0061] In a preferred embodiment, at least one device heated in the start-up mode by absorbing heat from a heat transfer medium is a third heat exchanger [preferably a heat transfer medium / water heat exchanger for the start-up mode] (see Figure 2, third heat exchanger 26). In the production mode, the third heat exchanger [preferably a product gas / water heat exchanger for the production mode] is preferably used to heat or generate steam, preferably to heat water by absorbing heat from the product gas. For switching from the start-up mode to the production mode, the plant of the present invention preferably includes corresponding conduits and valves that enable modified interconnections (see Figure 2).

[0062] In a preferred embodiment, at least one device heated in the start-up mode by absorbing heat from a heat transfer medium is a fourth heat exchanger [preferably a heat transfer medium / heat transfer medium heat exchanger for the start-up mode] (see Figure 2, fourth heat exchanger 20). In the production mode, the fourth heat exchanger [preferably a product gas / NH3 heat exchanger for the production mode] is used to heat the NH3 by absorbing heat from the product gas. For switching from the start-up mode to the production mode, the plant of the present invention preferably includes corresponding conduits and valves that enable modified interconnections (see Figure 2).

[0063] In a preferred embodiment, at least one device heated in the start-up mode by absorbing heat from a heat transfer medium is a fifth heat exchanger [preferably a heat transfer medium / water heat exchanger for the start-up mode] (see Figure 2, fifth heat exchanger 28). In the production mode, the fifth heat exchanger [preferably a product gas / water heat exchanger for the production mode] is preferably used to heat water by absorbing heat from the product gas. For switching from the start-up mode to the production mode, the plant of the present invention preferably includes corresponding conduits and valves that enable modified interconnections (see Figure 2).

[0064] In a preferred embodiment, at least one device heated in the start-up mode by receiving heat from a heat transfer medium is a sixth heat exchanger [preferably a heat transfer medium / water heat exchanger for the start-up mode] (see Figure 2, sixth heat exchanger 29). In the production mode, the sixth heat exchanger [preferably a product gas / water heat exchanger for the production mode] is preferably used to heat water by absorbing heat from the product gas. For switching from the start-up mode to the production mode, the plant of the present invention preferably includes corresponding conduits and valves that enable modified interconnections (see Figure 2).

[0065] Furthermore, in the start-up mode, the combustion exhaust gases generated by the combustion of the combustion gases can also release heat to at least one device in the plant. This at least one device is typically located within the combustion exhaust gas duct. This at least one device is preferably located downstream of the first and / or second heat exchanger in the direction of the combustion exhaust gas flow.

[0066] In a preferred embodiment, at least one device heated in the start-up mode by absorbing heat from the combustion exhaust gas is a first combustion exhaust gas / combustion air heat exchanger (see Figure 2, first combustion exhaust gas / combustion air heat exchanger 45), which is preferably used in the start-up mode and / or production mode to heat the combustion air by absorbing heat from the combustion exhaust gas.

[0067] In a preferred embodiment, at least one device heated in the start-up mode by absorbing heat from the combustion exhaust gas is a combustion exhaust gas DeNOx unit (see Figure 2, combustion exhaust gas DeNOx unit 50), which is preferably used in the start-up mode and / or production mode to remove nitrogen oxides (NOx) from the combustion exhaust gas.

[0068] In a preferred embodiment, at least one device heated in the start-up mode by absorption of heat from the combustion exhaust gas is a combustion exhaust gas / water heat exchanger (see FIG. 2, combustion exhaust gas / water heat exchanger 52), which is preferably used in the start-up mode and / or the production mode to heat water by absorption of heat from the combustion exhaust gas and preferably to heat or generate steam.

[0069] In a preferred embodiment, at least one device heated in the start-up mode by absorption of heat from the combustion exhaust gas is a second combustion exhaust gas / combustion air heat exchanger (see FIG. 2, second combustion exhaust gas / combustion air heat exchanger 43), which is preferably used in the start-up mode and / or the production mode to heat the combustion air by absorption of heat from the combustion exhaust gas.

[0070] Preferably, the combustion device and the second NH3 decomposition device are in a heat exchange relationship and are configured for a heat flow from the combustion device to the second NH3 decomposition device. For this purpose, they are preferably designed in the same way as a primary reformer used in conventional steam reforming for producing H2, O2 and CO / CO2 from H2O and CH4.

[0071] In a preferred embodiment of the plant according to the invention, the plant is designed for a throughput based on H2 of at least 500 mol·h -1 , preferably at least 1000 mol·h -1 , more preferably at least 5000 mol·h -1 , even more preferably at least 10000 mol·h -1 , most preferably at least 50000 mol·h -1 , especially at least 100000 mol·h -1 in the production mode (i.e., during normal operation).

[0072] In a preferred embodiment of the plant according to the invention, the plant is at least 50 m 3 , preferably at least 100 m 3 , more preferably at least 500 m 3More preferably, at least 1000m 3 , most preferably at least 5000m 3 , especially at least 10,000m 3 It is equipped with a tank for liquid NH3 having a volume of [volume].

[0073] In a preferred embodiment of the plant of the present invention, in addition to the first NH3 decomposition device, the plant further includes a second NH3 decomposition device having at least three, preferably at least four, more preferably at least five, even more preferably at least six, most preferably at least seven, and especially at least eight catalyst beds, each containing an NH3 decomposition catalyst, wherein each catalyst bed is preferably in a tube. The catalyst beds are preferably connected in parallel. Preferably, each catalyst bed contains the same NH3 decomposition catalyst.

[0074] In a preferred embodiment of the plant of the present invention, the plant comprises a second NH3 decomposition device having at least one catalyst bed containing an NH3 decomposition catalyst, in addition to a first NH3 decomposition device, wherein the length of the catalyst bed in the direction of NH3 flow is at least 1.0 m, preferably at least 1.5 m, more preferably at least 2.0 m, even more preferably at least 2.5 m, most preferably at least 3.0 m, and particularly at least 3.5 m, and the catalyst bed is preferably located in a pipe.

[0075] In a preferred embodiment of the plant of the present invention, the plant comprises a combustion device having at least three, preferably at least four, more preferably at least five, even more preferably at least six, most preferably at least seven, and especially at least eight burners for burning combustion gases.

[0076] In a preferred embodiment of the plant of the present invention, the plant includes a first heat exchanger and / or a second heat exchanger, which independently take the form of a tube heat exchanger or a shell-and-tube heat exchanger.

[0077] In a preferred embodiment of the method of the present invention, at least 500 mol·h is used in the production mode (i.e., during normal operation). -1 Preferably at least 1000 mol·h -1 , more preferably at least 5000 mol·h -1 More preferably, at least 10,000 mol·h -1 Most preferably at least 50,000 mol·h -1 , especially at least 100,000 mol·h -1 The throughput based on H2 is achieved.

[0078] In a preferred embodiment of the method of the present invention, during the manufacturing mode (i.e., during normal operation), the liquid NH3 is at least 50 ml 3 Preferably at least 100m 3 , more preferably at least 500m 3 More preferably, at least 1000m 3 , most preferably at least 5000m 3 , especially at least 10,000m 3 It is taken out from a tank having a certain volume.

[0079] In a preferred embodiment of the method of the present invention, in the production mode (i.e., during normal operation), catalytic decomposition of NH3 is carried out in at least three, preferably at least four, more preferably at least five, even more preferably at least six, most preferably at least seven, and especially at least eight catalyst beds, each containing an NH3 decomposition catalyst, wherein each catalyst bed is preferably located in a tube, and NH3 preferably flows through the catalyst beds in parallel.

[0080] In a preferred embodiment of the method of the present invention, in the production mode (i.e., during normal operation), catalytic decomposition is carried out in at least one catalyst bed containing an NH3 decomposition catalyst, wherein the length of the catalyst bed in the direction of NH3 flow is at least 1.0 m, preferably at least 1.5 m, more preferably at least 2.0 m, even more preferably at least 2.5 m, most preferably at least 3.0 m, and particularly at least 3.5 m, and the catalyst bed is preferably located in a tube.

[0081] In a preferred embodiment of the method of the present invention, in the manufacturing mode (i.e., during normal operation), the combustion of the combustion gas is carried out using at least three, preferably at least four, more preferably at least five, even more preferably at least six, most preferably at least seven, and especially at least eight burners.

[0082] According to the present invention, catalytic decomposition of NH3 means the formation of N2 and H2, which is sometimes referred to as "cracking" of NH3 in the prior art.

[0083] Preferably, according to the present invention, catalytic decomposition of NH3 is carried out in the absence of O2.

[0084] Preferably, the manufacturing mode of the present invention includes the following means: (i) Evaporation of NH3; (ii) Catalytic decomposition of NH3 with heat supply to obtain a product gas containing N2, H2 and any undecomposed NH3; (iii) Heat recovery; (iv) Undegraded NH3 may be recovered; (v) Purification of H2.

[0085] Since H2O is frequently present in liquid NH3 at concentrations of 0.5% by weight or less, typically less than 0.3% by weight, H2O is not a reaction product and may be present in very small amounts. As a result of the evaporation of NH3, the presence of H2O at relatively low concentrations is expected.

[0086] NH3 - From storage to before catalytic decomposition According to the present invention, NH3 is preferably stored as a starting material.

[0087] The stored NH3 is preferably in liquid form in a cooling tank at atmospheric pressure and a temperature below its boiling point of -33.5°C. A pump is used to supply the NH3 to the plant at plant pressure.

[0088] Preferably, NH3 is heated continuously to multiple temperature levels according to the present invention before it can be catalytically decomposed.

[0089] Starting from liquid NH3, the NH3 is heated and then evaporated to an average temperature level (<300°C) by heat absorption from water or steam. In the production mode, steam is preferably generated by heat absorption from combustion exhaust gas and / or product gases. In the start-up mode, steam is preferably generated by an electrically operated H2O evaporation device.

[0090] Preferably, a preheater is positioned downstream of the tank and upstream of the NH3 evaporator in the direction of NH3 flow. This preheater preferably heats the NH3 to a desired temperature at the inlet to the NH3 evaporator, where the NH3 absorbs heat from water previously away from the NH3 evaporator as steam condensate. Preferably, the steam and steam condensate are guided countercurrently through the preheater and the NH3 evaporator.

[0091] Next, the NH3 is preferably further heated to a high temperature level (>300°C).

[0092] In the manufacturing mode, further heating of NH3 is preferably carried out by absorbing heat directly from the combustion exhaust gas and / or product gas, i.e., without using water as a heat transfer medium.

[0093] For this purpose, a corresponding heat exchanger is provided for the manufacturing mode: - Preferably a fourth heat exchanger [preferably a product gas / NH3 heat exchanger for the production mode]; - Preferably, a first heat exchanger [preferably, a combustion exhaust gas / NH3 heat exchanger for the manufacturing mode]; and / or - Preferably, a second heat exchanger [preferably a combustion exhaust gas / intermediate product gas heat exchanger for the production mode].

[0094] In the startup mode, further heating of NH3 is preferably carried out by absorbing heat from an electric heating element.

[0095] In order to catalytically decompose the evaporated NH3 in the start-up mode, the evaporated NH3 must be heated to the activation temperature of the NH3 decomposition catalyst.

[0096] In preferred embodiments, the NH3 decomposition catalyst is nickel-based, and the evaporated NH3 is preferably heated to a temperature in the range of 600 to 650°C.

[0097] In other preferred embodiments, the NH3 decomposition catalyst is ruthenium-based, and the evaporated NH3 is heated to a temperature preferably in the range of 350 to 400°C.

[0098] In all of these embodiments, NH3 (partially or entirely) passes through an electrically heated element and is heated to a temperature higher than the activation temperature of the NH3 decomposition catalyst in the first NH3 decomposition device. The heated NH3 then flows into the first NH3 decomposition device, where the NH3 is at least partially decomposed. Thus, preferably in an adiabatic reaction, a conversion rate of, for example, 18% can be achieved depending on the preheating temperature.

[0099] NH3-catalytic decomposition The catalytic decomposition of NH3 according to this invention is an actual reaction for the formation of H2, which in principle proceeds thermally but is accelerated by the use of an NH3 decomposition catalyst. According to this invention, catalytic decomposition of NH3 can be carried out under various conditions with various interconnections to various reactor types using various NH3 decomposition catalysts.

[0100] According to the present invention, catalytic decomposition of NH3 is preferably carried out by supplying heat in the presence of an NH3 decomposition catalyst. Important parameters for catalytic decomposition of NH3 are the type of NH3 decomposition catalyst, the reaction temperature, and the reaction pressure.

[0101] The useful NH3 decomposition catalysts according to the present invention include a variety of materials. The reaction temperature at which catalytic decomposition of NH3 proceeds is determined in particular by the selection of the NH3 decomposition catalyst.

[0102] In preferred embodiments of the present invention, a nickel-based NH3 decomposition catalyst is used. The reaction temperature and reaction pressure determine the equilibrium conversion rate. At 900°C and a pressure of 20 bar, the decomposition of NH3 proceeds almost quantitatively. At 650°C, the conversion rate of NH3 is about 98.5%, and at 500°C, it is only about 95%. According to the present invention, to achieve a high conversion rate, it is preferable to establish a reaction temperature in the range of about 600°C to about 900°C, preferably about 600°C to about 700°C. In terms of energy balance and conversion rate, the optimal reaction temperature is in the range of about 630°C to 640°C. Nickel-based NH3 decomposition catalysts are advantageous despite relatively high reaction temperatures. Due to the high conversion rate, the residual content of undecomposed NH3 in the product gas is relatively low, so it is preferable to omit the separation of undecomposed NH3 for recovery. Instead, the combined separation of N2 and undecomposed NH3 from the product gas is combined by pressure swing adsorption during the H2 purification process.

[0103] The NH3 decomposition catalyst preferably contains supported nickel. Preferred support materials include Al2O3, MgO, SiO2, mesoporous SiO2 (e.g., MCF-17, MCM-41, SBA-15), zeolite (e.g., HY, H-ZSM-5), BaMnO3, BaTiO3, BaZrO3, CaMnO3, CaTiO3, CaZrO3, CeO2, Gd2O3, GdAlO3, KNbO3, La2O3, LaAlO3, MnO2, The group is selected from NaNbO3, Nb2O5, Sm2O3, SmAlO3, SrMnO3, SrTiO3, SrZrO3, TiO2, Y2O3, ZrO2, carbon (e.g., CNT, SWCNT, AX-21, MSC-30, MESO-C, GNP, activated carbon, graphene, graphene oxide), attapulgite, hydrocalmite, sepiolite, and mixtures thereof.

[0104] In another preferred embodiment of the present invention, a ruthenium-based NH3 decomposition catalyst is used. For this purpose, according to the present invention, a reaction temperature in the range of about 450°C to about 500°C is preferred, but a somewhat lower conversion rate of, for example, about 95%, can be achieved so that a higher residual content of undecomposed NH3 in the product gas is obtained.

[0105] Alternatively, other NH3 decomposition catalysts may be used at even lower reaction temperatures. Lower reaction temperatures result in lower conversion rates, requiring more undecomposed NH3 to be separated from the product gas and recycled.

[0106] In a preferred embodiment, the first NH3 decomposition device includes two catalyst beds connected in series, one of which contains an NH3 decomposition catalyst having a relatively high activation temperature (preferably a first nickel-based NH3 decomposition catalyst), and the other catalyst bed contains an NH3 decomposition catalyst having a relatively low activation temperature (preferably a second nickel-based NH3 decomposition catalyst). NH3 decomposition catalysts with different activation temperatures are known to those skilled in the art (see, for example, I. Lucentini et al., Ind. Eng. Chem. Res. 2021, 60, 51, 18560-18611). According to the present invention, it is preferable to use an NH3 decomposition catalyst based on iron, ruthenium, nickel, cerium, cobalt, chromium, iridium, copper, platinum, molybdenum, palladium, zirconium, tungsten and / or vanadium, more preferably an NH3 decomposition catalyst based on nickel, iron and / or cerium.

[0107] In the starting mode, catalytic decomposition of NH3 preferably proceeds over an NH3 decomposition catalyst having a particularly relatively low activation temperature (preferably a second nickel-based NH3 decomposition catalyst). In contrast, in the production mode, catalytic decomposition of NH3 preferably proceeds first over an NH3 decomposition catalyst having a particularly relatively high activation temperature (preferably a first nickel-based NH3 decomposition catalyst), and additionally or subsequently over an NH3 decomposition catalyst having a relatively low activation temperature (preferably a second nickel-based NH3 decomposition catalyst).

[0108] Preferably, according to the present invention, the reaction pressure is about 15 bar to about 25 bar. Since the stoichiometry of the reaction (2NH3 → N2 + 3H2) increases the volume, an increased reaction pressure fundamentally negatively affects the conversion rate. On the other hand, to limit the volume of the vessel and therefore the capital cost, it is desirable to operate the entire process at a higher pressure. A conversion rate of over 99% may be achievable at a reaction pressure of just 1 bar at a reaction temperature above 400°C. However, since a reaction pressure of 1 bar is only feasible in a microplant, the plant of the present invention is preferably operated at a higher reaction pressure, even if it means accepting a certain loss of conversion rate as a result.

[0109] The reaction pressure is determined in particular by the performance of H2 purification. The preferred pressure swing adsorption (PSA) according to the present invention for H2 purification can be effectively operated according to the invention at a pressure preferably in the range of about 15 bar to about 25 bar. The pressure of the product gas when it starts from the second NH3 decomposition device is preferably in the range of about 15 to about 25 bara, more preferably about 18 bara to about 22 bara, and even more preferably about 19 bara to about 21 bara. In this way, a good balance is found between the requirements of pressure swing adsorption on the one hand and the conversion rate achieved on the other hand.

[0110] In principle, the decomposition of NH3 can proceed using different reactor types.

[0111] In adiabatic reaction regimes, the internal heat of the reaction gas is used as the energy source for the reaction. Suitable reactors for this purpose are self-thermal reformers and secondary reformers that function in conjunction with internal energy generation. Combustion air is added to the process gas to raise the temperature so that the reactor outlet temperature reaches the desired temperature, and a portion of the reaction gas is burned. A drawback is the presence of water formed during combustion in the process gas, which must be removed by condensation. Then, some of the undecomposed NH3 must be lost by dissolving in the condensed water or recycled. Furthermore, high temperatures result in the formation of a considerable amount of nitrogen oxides.

[0112] According to the present invention, these drawbacks are avoided in that the product gas is physically separated from the combustion gas and the combustion exhaust gas formed from the combustion gas.

[0113] In the manufacturing mode, the decomposition of NH3 according to the present invention preferably proceeds in two stages in two NH3 decomposition devices through which the flow passes continuously. In the first NH3 decomposition device, only a portion of the NH3 is partially decomposed first. Then, the remaining decomposition of NH3 up to the obtained maximum conversion rate is carried out in the second NH3 decomposition device. Preferably, for this purpose, the second NH3 decomposition device, together with the combustion device of the present invention, forms a reactor similar in design to the primary reformer, as described in detail above.

[0114] In the starting mode, the decomposition of NH3 according to the present invention preferably proceeds in one step only in a first NH3 decomposition device which may comprise several catalyst beds connected in series.

[0115] In both operating modes, preheated NH3 enters a first NH3 decomposition device containing an NH3 decomposition catalyst, where partial catalytic decomposition of NH3 occurs to some extent, yielding N2 and H2. An intermediate product gas is formed, which still contains a considerable amount of undecomposed NH3, but also contains the already formed N2 and H2. As a result of the endothermic decomposition of NH3, the intermediate product gas is preferably cooled. Preferably, the conversion rate of decomposed NH3 in the first NH3 decomposition device is at most 25%, more preferably at least 20%, of the total conversion rate achieved. Preferably, the conversion rate of decomposed NH3 in the first NH3 decomposition device is at least 5%, more preferably at least 10%, and even more preferably at least 15% of the total conversion rate achieved.

[0116] After exiting the first NH3 decomposition device, the intermediate product gas is used differently depending on the operating mode.

[0117] In the starting mode, the intermediate product gas may be mixed with NH3 and then combusted in the combustion device by supplying combustion air.

[0118] As already mentioned, in a preferred embodiment, the NH3 stream in the starting mode is divided into a first NH3 substream and a second NH3 substream. Only the first NH3 substream is supplied to the first decomposition device. Instead, the second NH3 substream flows through the second NH3 decomposition device, and as a result, heat is absorbed from the second NH3 substream by the second NH3 decomposition device. Thus, the second NH3 substream initially functions only as a heat transfer medium. In this way, by gradually heating the second NH3 decomposition device until the starting temperature for catalytic decomposition of NH3 is reached, additional H2 is produced in the second NH3 decomposition device by catalytic decomposition of NH3. For example, the first NH3 substream is supplied to the first NH3 decomposition device, and the entire resulting intermediate product gas (e.g., in the case of a 20% conversion rate: 20 mol% H2 + N2 and 80 mol% undecomposed NH3) can be completely combusted in the combustion device. The second NH3 substream is not supplied to the first NH3 decomposition device and is not burned, but is preferably used as a heat transfer medium. For this purpose, among other uses, it is preferably conducted within the circuit and preferably plays a role in heating the second NH3 decomposition device.

[0119] In the manufacturing mode, the intermediate product gas is preferably reheated before entering the downstream second NH3 decomposition device. Then, in the second NH3 decomposition device, the residual decomposition of NH3 proceeds to the total conversion rate to be achieved.

[0120] In the production mode, the product gas is formed in the second NH3 decomposition device of the present invention by the decomposition of NH3 and exits the second NH3 decomposition device through a dedicated outlet. The combustion gas is burned together with the combustion air in the combustion device, and the resulting combustion exhaust gas also exits the combustion device through a dedicated outlet and preferably enters a combustion exhaust gas duct. The product gas and combustion exhaust gas are not mixed with each other and remain physically separated. The heat of combustion generated by the combustion of the combustion gas flows into the second NH3 decomposition device as a heat flow, providing the heat necessary to maintain the endothermic decomposition of NH3.

[0121] In a preferred embodiment of the present invention, catalytic decomposition of NH3 in the production mode proceeds within a second NH3 decomposition device similar to a primary reformer. For this purpose, the primary reformer analog includes both the second NH3 decomposition device and the combustion device of the present invention. For this purpose, the NH3 decomposition catalyst is preferably arranged within the second NH3 decomposition device of the present invention in at least one tube, more preferably at least two tubes, and even more preferably at least three tubes through which NH3 flows. At least one tube contains the NH3 decomposition catalyst. NH3 preferably flows from top to bottom through at least one tube. In a physically separated combustion chamber, the combustion gas to be burned is preferably a mixture of NH3 and H2 together with combustion air (combustion device). The N2 formed in addition to H2 during the catalytic decomposition of NH3 is inert and acts as an additional heat carrier. The heat of combustion generated by the combustion process within the combustion chamber of the combustion device is used to heat the second NH3 decomposition device, preferably one or more tubes through which the NH3 to be decomposed passes. For this purpose, the heat flow is directed from the combustion device to a second NH3 decomposition device.

[0122] The NH3 decomposition catalyst in the first NH3 decomposition device is preferably the same as that in the second NH3 decomposition device. If the first NH3 decomposition device includes a plurality of catalyst beds connected in series, preferably at least one of these series-connected catalyst beds contains the same NH3 decomposition catalyst as that in the second NH3 decomposition device.

[0123] Combustion gas According to the present invention, heat is provided by the combustion of a combustion gas in a combustion device. For this purpose, the combustion device preferably comprises one or more burners, preferably at least two burners, and more preferably at least three burners.

[0124] The combustion gas preferably contains NH3. This is especially true in the starting mode. Therefore, the combustion device of the present invention is preferably an NH3 combustion device.

[0125] The combustion gas preferably contains a mixture of H2 and NH3, because this mixture generates a moderate flame temperature and has better combustion characteristics than pure NH3. An appropriate mixing ratio of H2 and NH3 further results in less nitrogen oxide formation than in the absence of H2.

[0126] In the manufacturing mode, the combustion gas used is preferably the residual gas mixture remaining after separating H2 from the product gas by pressure swing adsorption. Fresh NH3 is preferably metered and supplied to this residual gas mixture. Since pressure swing adsorption typically does not separate all of the H2 from the product gas, the remaining H2 in the residual gas mixture preferably acts as a combustion enhancer for NH3.

[0127] The intermediate product gas formed in the first NH3 decomposition device in the starting mode contains H2 and may be mixed with further NH3, and is burned to provide combustion exhaust gas in the combustion device in the starting mode. At least partial decomposition of NH3 makes available a sufficient amount of H2 to ensure or improve the combustion of NH3.

[0128] In the starting mode, preferably an electrically operated H2O evaporation device and an electric heating element require electrical energy for further heating of NH3 for evaporation and catalytic decomposition, and the subsequent combustion of NH3 together with H2 formed by catalytic decomposition then provides heat for heating the heat transfer medium.

[0129] As already mentioned, in a preferred embodiment, the amount of H2 in the combustion gas increases in the starting mode compared to the manufacturing mode. The higher proportion of H2 in the combustion gas promotes the combustion of the NH3 and H2 mixture, making it possible to achieve the operating temperature more quickly. Therefore, the method of the present invention is preferably carried out in a manufacturing mode having H2 component A1 and a starting mode having H2 component A2, where A2 > A1. In a preferred embodiment, the relative difference between A2 and A1 is at least 1 vol%; more preferably at least 2 vol%; even more preferably at least 3 vol%; most preferably at least 4 vol%; and particularly at least 5 vol%.

[0130] It will be apparent to those skilled in the art that the conditions during the start-up mode do not need to be statically constant, but can change dynamically, especially considering the continuous heating of the plant or its components. Accordingly, according to the present invention, it is preferable that for at least a portion of the total duration of the start-up mode, the ratio A2 increases compared to the ratio A1. For example, the start-up mode can be divided into a first section and a second section immediately following it, where A2 > A1 in the first section and A2 = A1 in the second section.

[0131] Combustion air Preferably, the combustion device (combustion chamber of the reactor) is supplied with combustion air that has been preheated, preferably by a first combustion exhaust gas / combustion air heat exchanger and / or a second combustion exhaust gas / combustion air heat exchanger. Preferably, the first combustion exhaust gas / combustion air heat exchanger and / or the second combustion exhaust gas / combustion air heat exchanger are located in a combustion exhaust gas duct, and the combustion air absorbs heat from the combustion exhaust gas.

[0132] Preferably, the combustion air is filtered before being supplied to the plant, compressed to the required pressure in a compressor, and then supplied and heated by a first combustion exhaust gas / combustion air heat exchanger and / or a second combustion exhaust gas / combustion air heat exchanger in a combustion exhaust gas duct. The heated combustion air then flows into the combustion device. Inside the combustion device or just upstream of its entry into the combustion device, the combustion air is mixed with the combustion gas (preferably NH3 in a mixture with H2).

[0133] After catalytic decomposition until the purification of the product gas -H2 In the production mode, the product gas exits the second NH3 decomposition device at a high temperature. To utilize the heat present in the product gas, downstream of the second NH3 decomposition device for the production mode, in the direction of the product gas flow, the product gas flows before being supplied for H2 purification. - Preferably a third heat exchanger [preferably a product gas / water heat exchanger for the production mode]; - Preferably a fourth heat exchanger [preferably a product gas / NH3 heat exchanger for the production mode]; - Preferably a fifth heat exchanger [preferably a product gas / water heat exchanger for the production mode]; and / or - Preferably a sixth heat exchanger [preferably a product gas / water heat exchanger for the production mode] Preferably, at least one heat exchanger is provided.

[0134] Product gas - Residual amount of undecomposed NH3 In the production mode, the preferred NH3 recovery according to the present invention preferably helps to separate undegraded NH3 from the product gas and provide it for further use as a combustion gas or recovered reactant. It is preferable to omit the separate recovery of NH3. Therefore, according to the present invention, the purification of H2 from the product gas in the production mode is preferably carried out by pressure swing adsorption (PSA). According to the present invention, small amounts of residual undegraded NH3 can also be separated preferably by pressure swing adsorption, thereby enabling a combined process of NH3 recovery and H2 purification.

[0135] Purification of the product gas -H2 and removal of residual gas mixture. In the production mode, H2 is more preferably purified according to the present invention by pressure swing adsorption (PSA). One reason why adsorption separation in a pressure swing adsorption device according to the present invention is preferred is that it proceeds at moderate pressure and can further achieve high purity H2 of 99.9% or more as needed, with an H2 yield in the range of about 80-85%. As already mentioned, pressure swing adsorption can also separate residual amounts of NH3 and optionally H2O. For this purpose, the product gas is preferably cooled to a desired temperature by a sixth heat exchanger [preferably a product gas / water heat exchanger for the production mode] before entering the pressure swing adsorption device. The corresponding amount of heat is preferably absorbed by water in the sixth heat exchanger. According to the present invention, the cooling water thus heated is preferably used to preheat NH3 in a preheating device where NH3 absorbs heat from the water. Subsequently, the cooled product gas is preferably sent to a pressure swing adsorption device, where the gas mixture is separated under pressure by adsorption.

[0136] H2 - From purification to storage In the manufacturing mode, the separated H2 preferably exits a pressure swing adsorption device and is preferably pressurized to, for example, about 200 bar using an H2 compressor. However, compression of the separated H2 to high pressure is not absolutely necessary, and pressures significantly lower than 200 bar are also in accordance with the present invention. Preferably, the compressed H2 then flows through a first H2 heat exchanger where cooling water absorbs heat from the compressed H2. In a preferred embodiment, the separated H2 is then pressurized further in a second H2 compressor. Preferably, the further compressed H2 flows through a second H2 heat exchanger where cooling water similarly absorbs heat from the compressed H2. The compressed H2 is then discharged from the plant at a pressure of, for example, about 70 bar and is stored, for example, in a suitable pressure vessel or sent directly to further applications.

[0137] Residual gas mixture In the manufacturing mode, the residual gas mixture remaining after purification / removal of H2, preferably in a pressure swing adsorption device, typically contains N2, H2O, residual NH3, and H2. Preferably, the residual gas mixture is sent to a combustion device so that it can be used to generate combustion heat.

[0138] Combustion exhaust gas The combustion exhaust gas exits the combustion device at a high temperature and preferably enters a combustion exhaust gas duct. To utilize the heat present in the combustion exhaust gas, a heat exchanger is preferably provided downstream of the combustion device in the direction of the combustion exhaust gas flow, through which the combustion exhaust gas flows before being discharged into the environment, for example, through a chimney. The heat exchanger is provided as follows: - Preferably, a second heat exchanger [preferably a combustion exhaust gas / intermediate product gas heat exchanger for the production mode; preferably a combustion exhaust gas / heat transfer medium heat exchanger for the start-up mode]; - Preferably, a first heat exchanger [preferably, a combustion exhaust gas / NH3 heat exchanger for the manufacturing mode; a combustion exhaust gas / heat transfer medium heat exchanger for the starting mode]; - Preferably, a first combustion exhaust gas / combustion air heat exchanger; - Preferably, a combustion exhaust gas / water heat exchanger; and / or - Preferably, a second combustion exhaust gas / combustion air heat exchanger.

[0139] In the starting mode as well, the combustion exhaust gas formed in the combustion of a mixture containing NH3 and H2 flows through the combustion exhaust gas duct, preferably heating a second heat exchanger [preferably a combustion exhaust gas / heat transfer medium heat exchanger for the starting mode], and then preferably heating a first heat exchanger [preferably a combustion exhaust gas / heat transfer medium heat exchanger for the starting mode], both releasing heat into the heat transfer medium. The combustion exhaust gas then flows through preferably a first combustion exhaust gas / combustion air heat exchanger, preferably a combustion exhaust gas DeNOx unit, preferably a combustion exhaust gas / water heat exchanger, and preferably a second combustion exhaust gas / combustion air heat exchanger. In this way, the combustion air or water is heated by the absorption of heat from the combustion exhaust gas.

[0140] water vapor The water supplied to the plant to generate steam is preferably desalinated. Air and other gases dissolved in the water are preferably removed by a degasser.

[0141] The water is preferably preheated by a fifth heat exchanger. In the production mode, the product gas preferably flows through the fifth heat exchanger [preferably a product gas / water heat exchanger for the production mode], so the water absorbs heat from the product gas. In the start-up mode, the heat transfer medium preferably flows through the fifth heat exchanger [preferably a heat transfer medium / water heat exchanger for the start-up mode], so the water absorbs heat from the heat transfer medium. In the flow direction of the product gas / heat transfer medium, the fifth heat exchanger is preferably located downstream of the third heat exchanger.

[0142] Next, the water preferably passes through a combustion exhaust gas / water heat exchanger and is heated. The combustion exhaust gas / water heat exchanger cools the combustion exhaust gas from the combustion device in the combustion exhaust gas duct and uses the heat present in the combustion exhaust gas to heat the steam.

[0143] Next, the steam is preferably led to a steam drum.

[0144] From the steam drum, water preferably passes through a third heat exchanger and therefore preferably returns to the steam drum, absorbing further heat. The third heat exchanger is located downstream of the second NH3 decomposition device in the flow direction of the product gas / heat transfer medium. In the production mode, the third heat exchanger [preferably a product gas / water heat exchanger for the production mode] preferably functions to cool the product gas while heating the steam using the heat also present in the product gas after it has left the second NH3 decomposition device. In the start-up mode, the third heat exchanger [preferably a heat transfer medium / water heat exchanger for the start-up mode] preferably functions to release heat from the heat transfer medium to the water. In the start-up mode, high-temperature steam may be additionally generated in an H2O evaporator and supplied to the NH3 evaporator along with the steam from the steam drum.

[0145] The condensation of steam within the NH3 evaporator generates heat to evaporate the preheated NH3. After flowing through the NH3 evaporator, the steam condensate is preferably sent to a preheater that preheats the NH3, so that the heat present in the steam is used in two stages to heat the NH3. Once flowing through the preheater, the steam condensate can be discharged from the plant.

[0146] Preferably, an electrically operated H2O evaporator supplies steam as long as the heat available in the start-up mode is insufficient for steam generation. The NH3 introduced from the tank to the plant is preferably preheated in a preheater with the help of electrically generated steam, as in the production mode, and then evaporated in an NH3 evaporator.

[0147] Heat transfer medium In the starting mode, a heat transfer medium, preferably N2 or NH3, is introduced through at least a portion of the plant to absorb heat from combustion or combustion exhaust gases and heat one or more devices in the plant to operating temperature. The heat transfer medium is preferably circulated here and pressed to the required pressure by a compressor. The plant of the present invention preferably includes several valves in appropriate locations to close the main process path at several locations in the starting mode and to allow circulation of the heat transfer medium.

[0148] Preferably, the heat transfer medium in the starting mode circulates from the compressor to a fourth heat exchanger [preferably a heat transfer medium / heat transfer medium heat exchanger for the starting mode], where it absorbs heat from the heat transfer medium conducted in crossflow.

[0149] The heat transfer medium in the starting mode preferably flows from there to a first heat exchanger [preferably a combustion exhaust gas / heat transfer medium heat exchanger for the starting mode], where it absorbs heat from the combustion exhaust gas.

[0150] The heat transfer medium in the starting mode then preferably flows to a second heat exchanger [preferably a combustion exhaust gas / heat transfer medium heat exchanger for the starting mode], where it similarly absorbs heat from the combustion exhaust gas.

[0151] In the starting mode, the heat transfer medium preferably flows from there through a second NH3 decomposition device, where it absorbs the heat of combustion that flows from the combustion device to the second NH3 decomposition device as a heat flow.

[0152] Subsequently, the heat transfer medium in the starting mode preferably reaches a third heat exchanger [preferably a heat transfer medium / water heat exchanger for the starting mode], where it releases heat into the water.

[0153] Next, the heat transfer medium in the starting mode preferably flows again through a fourth heat exchanger (i.e., a cross-flow), where it releases heat to the heat transfer medium conducted by the cross-flow.

[0154] Subsequently, the heat transfer medium in the starting mode preferably flows through a fifth heat exchanger [preferably a heat transfer medium / water heat exchanger for the starting mode], where it releases heat into the water.

[0155] Subsequently, the heat transfer medium in the starting mode preferably flows through a sixth heat exchanger [preferably a heat transfer medium / water heat exchanger for the starting mode], where it similarly releases heat into the water.

[0156] The heat transfer medium is ultimately returned to the compressor.

[0157] Description of the drawing The present invention will be described in detail below with reference to the drawings by preferred embodiments. Figures 1, 2, and 3 show, in flowchart form, preferred embodiments of a plant of the present invention that can carry out a preferred embodiment of the method of the present invention. In this case, the embodiment in Figure 3 is a modification of the embodiment in Figure 2 and is shown only as a cutout. Details not shown in the cutout of Figure 3 are preferably the same as those shown in Figure 2.

[0158] Figure 1 is a schematic diagram of such a process scheme. A portion of the NH3 used as a whole is combusted in a mixture with H2 and O2 (reaction (A)). Combustion releases heat of combustion Δ. The remaining portion of the NH3 is catalytically decomposed into H2 and N2 by supplying heat of combustion, and the resulting mixture contains not only H2 and N2 but also residual undecomposed NH3 (reaction (B)). Reactions A and B are preferably carried out separately in a common reactor of a similar design to a primary reformer. The majority of the H2 is separated as a product from the mixture formed by the decomposition of NH3, typically by pressure swing adsorption (PSA), and the remaining mixture of unseparated H2, N2 and undecomposed NH3 is sent to combustion (recycle (C)).

[0159] If the amount of unseparated H2 present in the remaining mixture is insufficient for the complete combustion of NH3, it may be possible to divert the H2 from the H2 products and similarly send it to combustion (recycling (D)). However, this is undesirable. For example, pressure swing adsorption typically already achieves excellent purity of H2, and the residual gas mixture remaining in the pressure swing adsorption device after H2 removal contains not only N2 and residual NH3 but also a sufficient amount of H2, which is largely unavoidable for process-related reasons. By recycling this H2-containing residual gas mixture to the combustion device, the energy present in the residual gas mixture can be utilized to generate combustion heat. Further enriching the residual gas mixture with H2 for combustion is economically unfeasible, at least in the production mode, and therefore undesirable. If the amount of residual gas mixture is overall insufficient to generate the amount of heat required for the catalytic decomposition of NH3, according to the present invention, it is preferable to increase the amount of NH3 in the combustion gas as needed, but not the amount of H2 from the purified valuable products.

[0160] Figure 2 shows a preferred device according to the present invention. For convenience, the manufacturing mode and startup mode will be described sequentially below.

[0161] Manufacturing mode system / method as shown in Figure 2: In the production mode, low-temperature, high-pressure liquid NH3 is supplied from tank 10 through conduit 11 by pump 12 through preheater 13 and heated. In NH3 evaporation device 14, the NH3 is evaporated and then flows through conduit 15 to branch 16, where the NH3 flow is split into two substreams. Proceeding from branch 16, the first substream of NH3 is expanded and supplied to combustion device 18 through conduit 17. The second substream of NH3 flows from branch 16 through conduit 19 to a fourth heat exchanger [preferably a product gas / NH3 heat exchanger for the production mode] 20, and then through conduit 21 to a first heat exchanger [preferably a combustion exhaust gas / NH3 heat exchanger for the production mode] 22, where the NH3 is further heated. The preheated NH3 is supplied to a first NH3 decomposition device 65, where partial catalytic decomposition takes place, preferably adiabatically. The intermediate product gas exiting the first NH3 decomposition device 65 is led via conduit 66 to a second heat exchanger [preferably a combustion exhaust gas / intermediate product gas heat exchanger for the production mode] 67, which is located upstream of the first heat exchanger 22 in the combustion exhaust gas duct 49 in the direction of combustion exhaust gas flow. The intermediate product gas is heated therein and then introduced into the second NH3 decomposition device 24 via conduit 23. The flow preferably flows from top to bottom through the second NH3 decomposition device 24. The combustion of H2 and NH3 in the combustion device 18 heats the second NH3 decomposition device 24, generating the heat necessary to sustain the reaction.

[0162] In the production mode, after the decomposition of NH3, the formed product gas (including N2, H2, and any residual NH3) flows through a third heat exchanger [preferably a product gas / water heat exchanger for the production mode] 26, then a fourth heat exchanger [preferably a product gas / NH3 heat exchanger for the production mode] 20, then a conduit 27, and then a fifth heat exchanger [preferably a product gas / water heat exchanger for the production mode] 28, which is preferably operated with water for further cooling. Finally, the product gas is further cooled by a sixth heat exchanger [preferably a product gas / water heat exchanger for the production mode] 29, and then supplied via a conduit 30 to a pressure swing adsorption device 31, where the gas mixture is separated under pressure by adsorption. The H2 separated here exits the pressure swing adsorption device 31 via conduit 32, is pressurized by the first H2 compressor 33, flows through the first H2 heat exchanger 34, the second H2 compressor 35 to further increase the pressure, and the second H2 heat exchanger 36, and is discharged from the plant via conduit 37 at a pressure of, for example, about 70 bar.

[0163] After H2 is separated, the residual gas mixture remaining in the pressure swing adsorption device 31 contains N2, residual NH3, and H2, and is returned via the return conduit 38 and supplied to the combustion device 18 via the branch conduit 39, thereby allowing the energy present in the residual gas mixture to be utilized for the generation of combustion heat.

[0164] In the manufacturing mode, combustion air for the combustion process is purified by a filter 40 in the combustion device 18, compressed by a compressor 41, and guided through a conduit 42 to a second combustion exhaust gas / combustion air heat exchanger 43 where it is heated. The combustion air then flows through a conduit 44 to a first combustion exhaust gas / combustion air heat exchanger 45 where it is further heated, and then flows through a conduit 46 and two branch conduits 47 and 48 to the combustion device 18, where the combustion air is supplied to a substream of NH3 supplied through conduit 17 to burn and thus generate combustion heat.

[0165] In the manufacturing mode, the high-temperature combustion flue gas from combustion in the combustion device 18 is first cooled through a second heat exchanger [preferably a combustion flue gas / intermediate product gas heat exchanger for the manufacturing mode] 67, thereby recovering heat for heating the intermediate product gas that is supplied to the second NH3 decomposition device 24 after exiting the first NH3 decomposition device 65. Subsequently, the combustion flue gas is further cooled by a first heat exchanger [preferably a combustion flue gas / NH3 heat exchanger for the manufacturing mode] 22, thereby recovering heat for heating the NH3 supplied to the first NH3 decomposition device 65. The combustion flue gas is then further guided through a combustion flue gas duct 49 via a first combustion flue gas / combustion air heat exchanger 45, thereby preheating the combustion air, which then flows through a combustion flue gas DeNOx unit 50, thereby removing nitrogen oxides (NOx) from the combustion flue gas. Subsequently, the combustion exhaust gas flows through the conduit 51 to the combustion exhaust gas / water heat exchanger 52, where heat is recovered for heating the water, and then flows through the second combustion exhaust gas / combustion air heat exchanger 43, which similarly serves to heat the combustion air. The combustion exhaust gas is then compressed in the end region of the combustion exhaust gas duct 49 by the combustion exhaust gas compressor 53 and exits the plant through the chimney 54.

[0166] In the manufacturing mode, water for generating steam is supplied through conduit 55, passes through a fifth heat exchanger [preferably a product gas / water heat exchanger for the manufacturing mode] 28, and is then supplied at a high temperature to a deaerator 56, where air and other gases dissolved in the water are removed. Pump 57 supplies the water through conduit 58 to a combustion exhaust gas / water heat exchanger 52, where it is heated. The combustion exhaust gas / water heat exchanger 52 serves to cool the combustion exhaust gas from the combustion device 18 in the combustion exhaust gas duct 49, and the thermal energy present in the combustion exhaust gas is used to heat the steam, which, after passing through the combustion exhaust gas / water heat exchanger 52, is led through conduit 59 to the steam drum 60. From the steam drum 60, the water is led through conduit 61 to a third heat exchanger [preferably a product gas / water heat exchanger for the manufacturing mode] 26, thus absorbing further thermal energy, and then returning to the steam drum through conduit 62. The third heat exchanger 26 is located in the outlet conduit 25 downstream of the second NH3 decomposition device 24 in the direction of the product gas flow and functions to cool the product gas after it leaves the second NH3 decomposition device 24. Thus, the heat obtained can be used to generate further steam.

[0167] In the manufacturing mode, the high-temperature steam generated in the steam drum 60 is introduced into the upper region of the NH3 evaporator 14 via the conduit 63. The condensation of the steam provides heat for the evaporation of the preheated NH3. After flowing through the NH3 evaporator 14, the steam condensate is supplied to the preheater 13 via the conduit 64, which preheats the NH3, and the heat present in the steam is utilized in two stages for heating the NH3. After passing through the preheater 13, the steam condensate can be discharged from the plant.

[0168] System / method in startup mode as shown in Figure 2 In the plant concept of the present invention, in the startup mode, a heat transfer medium, preferably N2 or NH3, is introduced through at least a portion of the plant to absorb heat from the combustion device or combustion exhaust gas and to heat the plant equipment to operating temperature. The low-temperature heat transfer medium is preferably circulated and introduced through a compressor 77 to build the required pressure. In the startup mode, to enable the circulation of the heat transfer medium, the main process path is closed at several points by at least some of the valves 68, 75, 79, 81, 82, and 83, where the first NH3 decomposition device 65 is excluded from circulation.

[0169] During startup, as long as there is still insufficient heat available for steam generation, an electrically operated H2O evaporator 84 preferably provides the steam. The NH3 introduced into the plant from tank 10 is preheated in preheater 13 with the help of electrically generated steam, as in the production mode, and then evaporated in NH3 evaporator 14. In order for the evaporated NH3 to be catalytically decomposed, it must be heated to the activation temperature of the NH3 decomposition catalyst, preferably to 600-650°C for nickel-based NH3 decomposition catalysts and preferably to 350-400°C for ruthenium-based NH3 decomposition catalysts.

[0170] In the starting mode, for this purpose, NH3 (partially or entirely) passes through the electric heating element 74, where it is heated to a temperature above the activation temperature of the NH3 decomposition catalyst in the first NH3 decomposition device 65. The heated NH3 then flows through the conduit 73 to the first NH3 decomposition device 65, where the NH3 is at least partially decomposed. Therefore, preferably in an adiabatic reaction, a conversion rate of, for example, 18% can be achieved depending on the preheating temperature.

[0171] In the starting mode, the intermediate product gas thus formed contains H2 and may be mixed with further NH3, which is then burned in the combustion device 18 to produce combustion exhaust gas. Partial decomposition of NH3 makes a sufficient amount of H2 available to ensure or improve the combustion of NH3. Preferably, an electrically operated H2O evaporation device 84 and an electric heating element 74 require electrical energy for further heating of NH3 for evaporation and catalytic decomposition, and the subsequent combustion of NH3 together with the H2 formed by catalytic decomposition then provides heat for heating the heat transfer medium.

[0172] In the starting mode, the heat transfer medium circulates from the compressor 77 to the fourth heat exchanger on the low-temperature side [preferably a heat transfer medium / heat transfer medium heat exchanger for the starting mode] 20, then through the conduit 21 to the first heat exchanger [preferably a combustion exhaust gas / heat transfer medium heat exchanger for the starting mode] 22, and then through the conduit 80 to the second heat exchanger [preferably a combustion exhaust gas / heat transfer medium heat exchanger for the starting mode] 67. The heat transfer medium then flows through the second NH3 decomposition device 24, reaches the third heat exchanger [preferably a heat transfer medium / water heat exchanger for the starting mode] 26 through the conduit 25, and then reaches the fourth heat exchanger on the high-temperature side [preferably a heat transfer medium / heat transfer medium heat exchanger for the starting mode] 20. The heat transfer medium then flows through heat exchanger 5 [preferably a heat transfer medium / water heat exchanger for the start-up mode] 28, and then through heat exchanger 6 [preferably a heat transfer medium / water heat exchanger for the start-up mode] 29, which ensures a constant inlet temperature to the downstream nitrogen compressor, which compensates for the pressure drop throughout the plant. Alternatively, the downstream compressor may be a dual-function N2 / NH3 compressor, used to compress both N2 and NH3.

[0173] In a preferred embodiment, the NH3 stream in the starting mode is divided into a first NH3 substream and a second NH3 substream. Only the first NH3 substream is supplied to the first decomposition device 65. The second NH3 substream flows through the first heat exchanger [preferably a combustion exhaust gas / heat transfer medium heat exchanger for the starting mode] 22 and then is separated via a conduit 80 and preferably flows through the second heat exchanger [preferably a combustion exhaust gas / heat transfer medium heat exchanger for the starting mode] 67 and then the second NH3 decomposition device 24, so that heat is absorbed from the second NH3 substream by the second NH3 decomposition device 24. Thus, the second NH3 substream initially functions only as a heat transfer medium. In this way, by gradually heating the second NH3 decomposition device 24 until it reaches the starting temperature (activation temperature) for catalytic decomposition of NH3, additional H2 is produced in the second NH3 decomposition device 24 by catalytic decomposition of NH3.

[0174] The heat transfer medium is heated in the starting mode as it flows through the low-temperature side of the fourth heat exchanger [preferably a heat transfer medium / heat transfer medium heat exchanger for the starting mode] 20, where it absorbs heat from the heat transfer medium conducted in crossflow. Furthermore, the heat transfer medium is heated as it flows through the first heat exchanger [preferably a combustion exhaust gas / heat transfer medium heat exchanger for the starting mode] 22 and the second heat exchanger [preferably a combustion exhaust gas / heat transfer medium heat exchanger for the starting mode] 67, where it absorbs heat from the combustion exhaust gas. Furthermore, the heat transfer medium is heated as it flows through the second NH3 decomposition device 24, where it absorbs the heat of combustion flowing from the combustion device 18 to the second NH3 decomposition device 24 as a heat flow.

[0175] The heat transfer medium is cooled in the starting mode as it flows through the third heat exchanger [preferably a heat transfer medium / water heat exchanger for the starting mode] 26, where it releases heat into the water, and then cooled as it flows through the high-temperature side of the fourth heat exchanger [preferably a heat transfer medium / heat transfer medium heat exchanger for the starting mode] 20, where it releases heat into the cross-flow guided heat transfer medium. In addition, the heat transfer medium is cooled as it flows through the fifth heat exchanger [preferably a heat transfer medium / water heat exchanger for the starting mode] 28, and then the sixth heat exchanger [preferably a heat transfer medium / water heat exchanger for the starting mode] 29, releasing heat into the water in each case.

[0176] The combustion exhaust gas formed by the combustion of a mixture containing NH3 and H2 flows through the combustion exhaust gas duct 49 in the starting mode, heating the second heat exchanger [preferably a combustion exhaust gas / heat transfer medium heat exchanger for the starting mode] 67, then the first heat exchanger [preferably a combustion exhaust gas / heat transfer medium heat exchanger for the starting mode] 22, both of which release heat into the heat transfer medium. The combustion exhaust gas then flows through the first combustion exhaust gas / combustion air heat exchanger 45, the combustion exhaust gas DeNOx unit 50, the combustion exhaust gas / water heat exchanger 52, and the second combustion exhaust gas / combustion air heat exchanger. In this way, the combustion air or water is heated by the absorption of heat from the combustion exhaust gas.

[0177] Once the plant has heated up to the point where it can switch from start-up mode to production mode, the circulation of the heat transfer medium is terminated with the help of valves 68, 75, 79, 81, 82, and 83.

[0178] If the heat transfer medium used is NH3 or another flammable gas, it can be discharged through the conduit 76 and valve 68 and then burned in the flare stack 70. It is preferable that the condensate be separated beforehand in the removal device 71. This condensate may contain small amounts (0.5% by weight or less) of water present in the NH3, and / or NH3 that was not converted in the second NH3 decomposition device 24 in the starting mode.

[0179] Figure 3 shows a preferred modified version of the plant of the present invention shown in Figure 2. Since the manufacturing mode according to the modified version in Figure 3 is almost the same as that shown in Figure 2, only the starting mode will be described below.

[0180] When N2 is used as the heat transfer medium, NH3 can be continuously metered and supplied.

[0181] System / Method in Startup Mode as shown in Figure 3 In this preferred embodiment, for the starting mode, the electric heating element 74 is positioned downstream of the valve 82 and upstream of the first NH3 decomposition device 65 in the direction of NH3 flow. The valve 82 is used to control the proportion of NH3 that is led to the first NH3 decomposition device 65 for partial catalytic decomposition, and the proportion of NH3 that is led to the second NH3 decomposition device 24 as a heat transfer medium via the conduit 80.

[0182] A valve 75, located immediately downstream of the branch 16 in the NH3 flow direction, is used to temporarily shut off or control the fuel NH3 supply conduit to the combustion device 18. This function is assumed by the first NH3 decomposition device 65 and valve 82.

[0183] Next, the NH3 is circulated as a heat transfer medium according to the present invention as follows: With valve 75 closed, the NH3 passes through branch 16 and is led to a fourth heat exchanger 20 (not shown again in Figure 3), and then to the first heat exchanger 22. It is then divided into a first NH3 substream and a second NH3 substream.

[0184] The first NH3 substream is supplied to the first NH3 decomposition device 65 via valve 82. Valve 81 is closed so that the intermediate product gas leaving the first NH3 decomposition device is supplied to the combustion device 18 via branch conduit 39, where it is combusted.

[0185] The second NH3 substream is supplied via conduit 80, with valve 81 closed, through the second heat exchanger 67 to the second NH3 decomposition device 24, where it initially acts as a heat transfer medium (if the activation temperature of the NH3 decomposition catalyst in the second NH3 decomposition device has not yet been reached). The second NH3 substream exiting the second NH3 decomposition device 24 is transferred via conduits 25 and 27 to the fourth heat exchanger 20, then to the fifth heat exchanger 28, and finally to the sixth heat exchanger 29 (none of which are shown again in Figure 3). Valves 83 and 68 are closed, thereby sending the second NH3 substream via conduit 76 to the compressor 77 (none of which are shown again in Figure 3). A portion of the NH3 is consumed in this way, and the intermediate product gases are led through, for example, conduit 19. [Explanation of Symbols]

[0186] 10 tanks 11 Conduit 12 pumps 13 Preheater 14 NH3 Evaporation Devices 15 Conduit 16 Branching point 17 Conduit 18 Combustion Devices 19 Conduit 20. Fourth heat exchanger [preferably, a product gas / NH3 heat exchanger for the production mode; a heat transfer medium / heat transfer medium heat exchanger for the start-up mode] 21 Conduit 22 First heat exchanger [preferably, for the manufacturing mode, a combustion exhaust gas / NH3 heat exchanger; for the starting mode, a combustion exhaust gas / heat transfer medium heat exchanger] 23 Conduit 24. Second NH3 disassembly device 25 Outlet conduit 26. Third heat exchanger [preferably, a product gas / water heat exchanger for the production mode; a heat transfer medium / water heat exchanger for the start-up mode] 27 Conduit 28. Fifth heat exchanger [preferably, a product gas / water heat exchanger for the production mode; a heat transfer medium / water heat exchanger for the start-up mode] 29. Sixth heat exchanger [preferably, a product gas / water heat exchanger for the production mode; a heat transfer medium / water heat exchanger for the start-up mode] 30 Conduit 31 Pressure Swing Suction Device 32 Conduit 33 H2 Compressor 34. First H2 heat exchanger 35 H2 Compressor 36. Second H2 heat exchanger 37. Output conduit for hydrogen 38 Return conduit 39 Branch conduit 40. Combustion air filter 41 Compressor 42 Conduit 43. Second combustion exhaust gas / combustion air heat exchanger 44 Conduit 45. First combustion exhaust gas / combustion air heat exchanger 46 Conduit 47 Branch conduit 48 Branch conduits 49 Combustion exhaust gas duct 50 Combustion exhaust gas DeNOx section 51 Conduit 52 Combustion exhaust gas / water heat exchanger 53 Combustion exhaust gas compressor 54 Chimney 55 Conduits for supplying water 56 Degassing device 57 Pumps 58 Conduit 59 Conduit 60 steam drums 61 Conduit 62 Conduit 63 Conduit 64 Conduit 65 First NH3 Decomposition Device 66 Conduit 67 Second heat exchanger [preferably, a combustion exhaust gas / intermediate product gas heat exchanger for the manufacturing mode; a combustion exhaust gas / heat transfer medium heat exchanger for the starting mode] 68 valves 69 Conduit 70 Flare Stack 71 Condensate removal device 72 pumps 73 Conduit 74 Electric heating element 75 valves 76 Conduit 77 Compressor 78 Another tank 79 valves 80 Conduit 81 valves 82 valves 83 valves 84 H2O evaporation device.

Claims

1. NH ３ From H ２ A plant for manufacturing, The aforementioned plant is capable of operating in a manufacturing mode at the operating temperature. The plant is capable of operating in a start mode to heat at least one of its devices from a start temperature to an operating temperature. For the start-up mode, the plant includes at least the following devices for heating the at least one device to the operating temperature: -NH ３ A heating element (74) for heating; -NH ３ downstream of the heating element (74) in the flow direction of, heated NH ３ and partially catalytically decompose it into H ２ , N ２ and residual NH ３ to produce a combustion gas containing, for the first NH ３ decomposition device (65); -Optionally, the first NH in the direction of combustion gas flow ３ A device downstream of the decomposition device (65) for metering and supplying combustion air into the combustion gas; - First NH in the direction of combustion gas flow ３ A combustion device (18) downstream of the decomposition device (65) for burning combustion gases to produce combustion heat and combustion exhaust gas; - Compressor (77) for compressing the heat transfer medium; and - A first heat exchanger (22) and / or a second heat exchanger (67) are provided downstream of the combustion device (18) in the flow direction of the combustion exhaust gas and downstream of the compressor (77) in the flow direction of the heat transfer medium, for heating the heat transfer medium by absorbing heat from the combustion exhaust gas. A plant in which at least one of the devices is located downstream of a first heat exchanger (22) and / or a second heat exchanger (67) in the flow direction of the heat transfer medium and is in fluid communication with the heat transfer medium for the absorption of heat from the heat transfer medium.

2. The aforementioned at least one device, - The second NH ３ Decomposition device (24), preferably in manufacturing mode, evaporated NH ３ Catalytic decomposition of H ２ and N ２ A second NH for producing a product gas containing ３ Disassembly device (24); - A third heat exchanger (26), preferably in the manufacturing mode, for heating water by absorbing heat from the product gas, preferably for heating or generating steam; - A fourth heat exchanger (20), preferably in the manufacturing mode, which absorbs heat from the product gas to generate NH ３ A fourth heat exchanger (20) for heating; - A fifth heat exchanger (28), preferably in the manufacturing mode, for heating water by absorbing heat from the product gas; and - A sixth heat exchanger (29), preferably in the manufacturing mode, for heating water by absorbing heat from the product gas. A plant according to claim 1, selected from the following.

3. The plant has, downstream of the first heat exchanger (22) and / or the second heat exchanger (67) in the direction of the combustion exhaust gas flow, - A first combustion exhaust gas / combustion air heat exchanger (45), preferably for heating the combustion air by absorbing heat from the combustion exhaust gas in the start-up mode and / or production mode; - A combustion exhaust gas denitrification unit (50), preferably for removing nitrogen oxides (NOx) from the combustion exhaust gas in the starting mode and / or manufacturing mode; - A combustion exhaust gas / water heat exchanger (52), preferably for heating water by absorbing heat from the combustion exhaust gas in the starting mode and / or manufacturing mode, preferably for heating or generating steam; - A second combustion exhaust gas / combustion air heat exchanger (43), preferably for heating the combustion air by absorbing heat from the combustion exhaust gas in the starting mode and / or manufacturing mode. The plant according to claim 1 or 2, comprising at least one device selected from the following.

4. The plant according to any one of claims 1 to 3, wherein the heating element (74) is electrically heated.

5. NH ３ Upstream of the heating element (74) in the flow direction, - H for evaporating water to generate steam ２ O evaporation device (84); and - Due to the absorption of heat from the aforementioned vapor, liquid NH ３ NH to evaporate ３ Evaporation device (14) A plant according to any one of claims 1 to 4, comprising:

6. The aforementioned H ２ The plant according to claim 5, wherein the evaporation device (84) is electrically heated.

7. The combustion device (18) and the second NH ３ The decomposition device (24) is in a heat exchange relationship with the combustion device (18), and the second NH ３ The plant according to any one of claims 1 to 6, configured for heat flow to a decomposition device (24).

8. NH ３ From H ２ A method for starting up a plant to manufacture, (c) NH ３ The process of heating, (d) heated NH ３ to the first NH ３ In the decomposition device (65), partial catalytic decomposition is performed, and H ２ , N ２ and remaining NH ３ A process for producing combustion gas containing, (e) Optionally, a step of metering and supplying combustion air into the combustion gas, (f) A step of burning the combustion gas in the combustion device (18) to produce combustion heat and combustion exhaust gas, (g) A step of compressing the heat transfer medium, (h) A step of heating the heat transfer medium by absorbing heat from the combustion exhaust gas, (i) A step of heating at least one device of the plant by absorbing heat from the heat transfer medium; Methods that include...

9. The aforementioned at least one device, - The second NH ３ Decomposition device (24), preferably after the plant has been started, the evaporated NH ３ Catalytic decomposition of H ２ and N ２ A second NH for producing a product gas containing ３ Disassembly device (24); - A third heat exchanger (26), preferably after the plant has been started, for heating water by absorbing heat from the product gas, preferably for heating or generating steam; - A fourth heat exchanger (20), preferably after the plant has been started up, for heating NH3 by absorbing heat from the product gas; - A fifth heat exchanger (28), preferably after the plant has been started, for heating water by absorbing heat from the product gas; and - A sixth heat exchanger (29), preferably a sixth heat exchanger (29) for heating water by absorbing heat from the product gas after the plant has been started. The method according to claim 8, selected from the following.

10. NH ３ The method according to claim 8 or 9, wherein the material is heated in step (c) using electrical energy.

11. (a) A process of evaporating water to generate steam, (b) Due to the absorption of heat from the steam, liquid NH ３ The process of evaporating and The method according to any one of claims 8 to 10, including the method described in any one of claims 8 to 10.

12. The method according to claim 11, wherein steam is produced in step (a) using electrical energy.

13. The method according to any one of claims 8 to 12, wherein the heat transfer medium circulates through at least a portion of the plant.

14. The heat transfer medium is N ２ Includes or N ２ The method according to any one of claims 8 to 13, which is essentially derived from.

15. The heat transfer medium is NH ３ Includes or NH ３ The method according to any one of claims 8 to 14, which is essentially derived from the above.

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