Ammonia decomposition for hydrogen production

Abstract

1. A process for producing hydrogen from ammonia, comprising ammonia decomposition, in which ammonia is decomposed into hydrogen and nitrogen, wherein the ammonia decomposition is carried out in a series of decomposition steps (13, 36, 17, 20), a final decomposition stream (21) is obtained after the last decomposition step (20), the last ammonia decomposition step (20) is carried out adiabatically, and / or the final decomposition stream (21) is quenched by direct mixing with water or steam after the last decomposition step.

Description

[Technical Field]

[0001] The present invention is in the field of hydrogen production based on ammonia decomposition. [Background technology]

[0002] The decomposition of ammonia has attracted much attention, especially in the production of hydrogen. In the ammonia decomposition process, ammonia is decomposed into H2 and N2 in the presence of heat and a suitable catalyst. Typical catalysts for ammonia decomposition include Ni-based, Ru-based, Pt-based, and iron-based catalysts.

[0003] Traditionally, the ammonia decomposition process is carried out by passing the ammonia feed through catalytic tubes in a combustion furnace, sometimes followed by a pre-cracking step. A challenge with this process is the high temperature of the cracked stream effluent from the catalytic tubes, which is typically around 750°C. Associated drawbacks include the need for expensive materials such as high-nickel alloy steels, as catalyst and tube life is affected by such high operating temperatures, and downstream equipment traversed by the process stream, particularly heat exchangers, is subject to nitriding and hydrogen attack. This problem is particularly prevalent with gas-to-gas heat exchangers, which are required to operate at high temperatures, pressures, and in the presence of hydrogen and nitrogen, conditions that are very demanding on metal surfaces.

[0004] Ammonia decomposition for the production of hydrogen is disclosed in WO 2022 / 243410 and WO 2022 / 265650. Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention faces the challenges posed by the high temperatures of the cracked stream effluent from the catalyst tubes that still affect the prior art of ammonia decomposition processes. [Means for solving the problem]

[0006] The object of the present invention is achieved by the process as set forth in the claims, in which the decomposition of ammonia is carried out in a series of steps until a final decomposition stream is obtained, the term final decomposition stream referring to the stream obtained after the last decomposition step, which contains mainly hydrogen and nitrogen and may contain small amounts of unreacted ammonia.

[0007] The temperature of the final decomposition stream is reduced compared to the prior art by performing the final decomposition step adiabatically or by quenching the final decomposition stream.

[0008] The present invention stems from the inventive discovery that the temperature of the decomposition stream can be significantly reduced if the final decomposition step is adiabatic or by quenching the decomposition stream. Quenching can be achieved using water, steam, ammonia, or a gaseous cryogenic stream, or a mixture of the aforementioned compounds. If the final decomposition step is adiabatic, the temperature of the process stream is reduced by the absorption of heat caused by the endothermic decomposition itself. In this case, the invention stems from the discovery that the decomposition itself can be considered a heat holdup suitable for reducing the temperature of the process stream, instead of conventional cooling. This is in contrast to the prior art, which integrated adiabatic decomposition even when it was only used for the initial pre-decomposition step.

[0009] A distinctive feature of some embodiments of the present invention is the serial adiabatic reactor configuration, which means that the adiabatic reactors are connected in series so that the effluent of the first reactor is further processed in the next reactor, and so on to the last reactor.

[0010] A very interesting advantage of carrying out the final decomposition step adiabatically is that the final decomposition stream is obtained at a lower temperature without the need for heat exchange with a cooling medium, which would require heat exchangers adapted to operate at very high temperatures. Similarly, quenching of the stream is carried out by direct mixing with a cooling medium, typically water or steam, and therefore does not require large heat exchange surfaces made of expensive materials.

[0011] According to an embodiment of the present invention, the decomposition step may include one or more steps carried out adiabatically, or may include steps carried out in the catalytic tubes of a furnace. The tubes are heated externally by heat generated in the combustion process of the furnace, i.e., by radiant heat and / or contact with hot fumes. A gas-heated or adiabatic reactor may also be operated in parallel with the catalytic tubes. For example, the gas-heated reactor may be heated by the effluent of the same catalytic tubes, whereby the hot effluent of the tubes is cooled by transferring heat to a parallel decomposition process.

[0012] The provision of catalytic tubes as described above is one option. In one embodiment, the entire decomposition process is carried out in a series of adiabatic decomposition steps without passing through catalytic tubes.

[0013] The adiabatic cracking steps may be carried out in separate adiabatic reactors with separate pressure vessels, or may be carried out in catalyst beds contained in a single pressure vessel. Intermediate heating steps are provided between the adiabatic cracking steps to provide the necessary heat of reaction. In one embodiment, the intermediate heating is provided by a heat exchanger or coil configured in a combustion furnace and heated by the furnace combustion process. In certain embodiments, some or all of the heat of reaction may be provided by an electric heater. DETAILED DESCRIPTION OF THE INVENTION

[0014] One aspect of the invention is a process for producing hydrogen from ammonia comprising ammonia decomposition in which a gaseous ammonia feed is catalytically decomposed into hydrogen and nitrogen, wherein the ammonia decomposition is carried out in a series of ammonia decomposition steps with the final decomposition stream being the stream obtained after the last ammonia decomposition step, the final ammonia decomposition step being carried out adiabatically without supplying heat to the process stream being decomposed, and / or the final decomposition stream is quenched by direct mixing with water and / or steam prior to indirect heat exchange.

[0015] The final decomposition stream may be the stream prior to heat removal by indirect heat exchange with one or more cooling fluids.

[0016] The final decomposition stream after the last step of decomposition, or after quenching if provided, has a much lower temperature than the effluent of the prior art catalyst tubes. Preferably, the stream has a temperature of 700°C or less, or 650°C or less, or 550°C or less, or 500°C or less. More preferably, the stream has a temperature in the range of 350-700°C, or 350-650°C, or 250-550°C.

[0017] The temperature of the feed to each decomposition step is preferably between 300° C. and 650° C. During the adiabatic decomposition step, the temperature of the process stream may be reduced by between 50° C. and 400° C., preferably between 200° C. and 300° C., or between 250° C. and 300° C.

[0018] In a preferred embodiment of the present invention, the decomposition process is carried out under pressure. Preferably, the decomposition process is carried out at a pressure ranging from 5 bar to 55 bar. The advantage of carrying out ammonia decomposition under pressure is that energy for compressing the hydrogen thus obtained can be saved or compression may not be required. Pressure is given in bar gauge pressure. Another advantage of operating under pressure is the reduction in the size of equipment such as reactors, PSA units, membrane separation units, and the like.

[0019] Adiabatic reactors may have axial, radial, or mixed axial-radial flow. In radial or mixed flow embodiments, the radial flow may be inward or outward.

[0020] In a preferred embodiment, the series of ammonia decomposition steps is configured such that the effluent of each decomposition step is sent to the next decomposition step in the series, preferably either directly or after heat exchange, but preferably without further processing that would change the composition of the stream, such as separation of components.

[0021] Preferred embodiments of the invention are set forth in the appended claims. The following includes a description of various features and embodiments of the invention followed by a description of preferred general embodiments.

[0022] New Ammonia Feed The new ammonia feed is typically liquid ammonia. The liquid ammonia can be heated and evaporated with heat removed from the ammonia decomposition process, for example, by removing heat from the final decomposition stream, from purified hydrogen, or from the distillation of an aqueous ammonia solution (aquaammonia solution). Aqueous solutions may be removed from a gas scrubbing process to remove unreacted ammonia from the decomposition stream. Electrical heating can also be employed to heat and vaporize the liquid ammonia.

[0023] The gaseous ammonia obtained after evaporation may be heated in a furnace until the gaseous ammonia reaches a temperature suitable for the decomposition process, for example a temperature above 400°C, or a temperature above 500°C, more preferably a temperature above 600°C, such as 650°C.

[0024] Hydrogen Refining The final cracked stream, containing primarily ammonia and hydrogen, is processed to obtain hydrogen of the desired purity, which may be 99% or greater and, in some embodiments, may reach 99.999%.

[0025] The hydrogen-containing cracked stream is typically cooled after the final cracking step by transferring heat to a fresh ammonia feed that is vaporized. The cracked stream may then be further cooled, preferably to a temperature of 5 to 60°C, and the resulting cooled gas mixture may optionally be scrubbed with water to remove unreacted ammonia.

[0026] The resulting scrubbed gas can be sent to a suitable hydrogen separation system, such as a PSA (pressure swing absorption) unit or a membrane-based system, to produce hydrogen and tail gas of the target purity. The tail gas can be recycled as fuel, for example, to a combustion furnace. In some embodiments, the tail gas removed from the first PSA unit is compressed and sent to a second PSA unit to improve hydrogen recovery. Flue gas produced inside the combustion furnace can be used to preheat the combustion air.

[0027] As described above, gas scrubbing produces an aqua-ammonia solution. This solution may be sent to a distillation column equipped with a reboiler and a condenser. The reboiler may be heated electrically or with steam, e.g., steam generated by removing heat from the cracked ammonia.

[0028] A portion of the ammonia vapor emerging from the top of the distillation column may be mixed with liquid ammonia or with gaseous ammonia, provided the liquid or gaseous ammonia is at sufficient pressure. The remaining portion may be condensed and returned to the distillation column. Alternatively, the entire ammonia vapor stream is condensed and a portion is recycled as ammonia feed.

[0029] Various embodiments of the present invention may include supplementing the fuel gas system with hydrogen taken from a hydrogen storage or buffer system. A storage or buffer system may be added to the fuel gas system to stabilize the ammonia decomposition process and have an independent source of fuel gas available at the battery limit during both normal operation and start-up.

[0030] Fuel gases different from hydrogen, such as ammonia, synthesis gas, natural gas, or hydrocarbon sources in general, may be advantageously employed to enhance the conversion of ammonia to hydrogen.

[0031] Hybrid Options In some embodiments, the decomposition process of the present invention is hybridized by providing a portion of the heat input electrically. The electrically supplied heat input may include one or more of the following: heat for reboiling the aqua ammonia solution, heat for preheating or vaporizing the liquid ammonia feed, heat for preheating combustion air in a fuel-fired furnace, and heat for decomposing the ammonia.

[0032] In some embodiments, electrical heating of the process stream is provided before or after the furnace. The electrical heater may be located inside or outside the furnace.

[0033] In other embodiments, the ammonia decomposition reactor may be configured with a tube-heated or plate-heated design to sustain the decomposition reaction. In certain embodiments, to achieve higher conversion of ammonia to products, the heated stream may be gaseous ammonia itself, or a stream of H and N, or water vapor, or a combination of the foregoing; alternatively or additionally, in some embodiments, heat may be supplied by electrodes.

[0034] In another embodiment, a gas turbine is installed to combine power generation and hydrogen production. According to an embodiment of the process of the present invention, a portion of the process fuel is sent to the gas turbine, and the turbine exhaust gas is used as a heat source in the ammonia decomposition process. For example, the gas turbine exhaust gas may be used to heat a bundle of catalyst tubes in a furnace. In a preferred embodiment, the gas turbine installation is combined with ammonia decomposition performed by catalyst tubes, and the ammonia decomposition performed by catalyst tubes is preceded or followed by an adiabatic ammonia decomposition reactor, and the gas turbine can also be included in a plant layout made up of only an adiabatic decomposition reactor.

[0035] In some embodiments, the gas turbine is incorporated into a steam generation system and coupled with a heat recovery steam generator (HRSG) to generate electricity via the steam turbine, and the hot exhaust gases of the gas turbine are used in the HRSG to generate steam for the steam turbine.

[0036] The process may include a fuel gas system to supply fuel to any combustion equipment, such as a furnace. In some embodiments, supplemental hydrogen may be added to the fuel gas system. In some embodiments, natural gas or an external fuel source may be used to supplement the fuel gas. The gas turbine described above may be installed as part of the fuel gas system.

[0037] First embodiment In a first embodiment, the ammonia decomposition is carried out entirely in a series of adiabatic reactors. This means that the process does not involve decomposition in heated catalyst tubes. To provide an intermediate heating step, in this embodiment, a combustion furnace may be used to heat the partially decomposed effluent of one or more adiabatic reactors before the effluent is introduced into the next reactor in the series. The preferred number of adiabatic reactors in the series is three or four. Each reactor contains at least one catalyst bed. In some embodiments, a single reactor may contain two or more catalyst beds.

[0038] The catalytic reactors are preferably separate reactors, each with its own pressure vessel. The reactors are connected in series, whereby the effluent of each reactor except the last is further cracked in the next reactor in the series. A final cracked stream is obtained at the output of the last reactor in the series. Generally, the final cracked stream has a temperature low enough to avoid the use of expensive materials in the following equipment, and can optionally be quenched, preferably with water and / or steam, as needed.

[0039] A particularly preferred implementation of the first embodiment of the present invention is A process for producing hydrogen from ammonia comprising ammonia decomposition in which a gaseous ammonia feed is catalytically decomposed into hydrogen and nitrogen, the ammonia decomposition being carried out in a series of preferably three or four ammonia decomposition steps with a final decomposition stream being the stream obtained after the last decomposition step, all of the ammonia decomposition steps being carried out adiabatically without supplying heat to the process streams being decomposed, each decomposition step being carried out separately in an adiabatic reactor, and each partially decomposed stream going to the next reactor in the series being heated by passing through a heat exchanger or coil in a fuel-fired furnace before entering the next reactor.

[0040] Second embodiment In a second embodiment, the decomposition process is carried out partly in one or more adiabatic reactors and partly in externally heated catalyst tubes. One or more adiabatic reactors may be provided upstream or downstream, or both, in the catalyst tubes, meaning that the decomposition step in the tubes can be carried out before or after the adiabatic decomposition.

[0041] In this second embodiment, the decomposition is carried out partly adiabatically and partly non-adiabatically with the supply of heat. A variant of the second embodiment is a first cracking step through one or more successive adiabatic reactors, followed by a final cracking step in catalyst tubes and a quenching step of the final cracked stream (adiabatic / tube / quench); a first cracking step through a series of one or more adiabatic reactors, followed by a cracking step in catalyst tubes, followed by a final cracking step in a series of one or more adiabatic reactors (adiabatic / tube / adiabatic); It may involve a first step of decomposition in catalyst tubes followed by a final decomposition or quench step in one or more successive adiabatic reactors (tube / insulation or tube / quench).

[0042] The catalyst tubes are preferably placed in a combustion furnace and heated by combustion flue gases.

[0043] In a further variation, the catalyst tubes operate in parallel with a gas-heated reformer or with one or more adiabatic reactors. For example, the partially cracked effluent of one or more first adiabatic reactors is partially fed to the catalyst tubes and partially fed to a parallel gas-heated reactor (GHR). The gas-heated reactor can be heated by the hot effluent of the catalyst tubes. For example, the gas-heated reactor can be a shell-and-tube reactor in which cracking is carried out on the tube side and the hot effluent traverses the shell side.

[0044] In embodiments using a gas-heated reactor, the reactor effluent is typically at a high temperature. According to various embodiments, heat can be removed from the effluent in a steam boiler or in the reboiler of an ammonia distillation column. Alternatively, the stream can be quenched with water and / or steam.

[0045] In a further variation of the second embodiment, the cracked stream effluent from the catalyst tubes is quenched before or after passing through a steam boiler. In a further variation, quenching is performed, but no steam boiler is installed. If no boiler is present, the heat for the ammonia column reboil can be supplied electrically, as in the hybrid option described above.

[0046] Instead of a steam reboiler, an ammonia reboiler may be installed.

[0047] Third embodiment A third embodiment involves multiple adiabatic decomposition steps carried out in catalyst beds housed in a single pressure vessel with interbed heating, preferably electrical. Preferably, the decomposition is carried out entirely in this series of catalyst beds without passing the process gas through the catalyst tubes of a furnace. A variation of this embodiment, however, includes at least one decomposition step carried out in an externally heated catalyst tube.

[0048] The catalyst interbed heater may also include at least one heat exchanger configured to recover heat from the process gas stream and / or the flue gas stream. [Brief explanation of the drawings]

[0049] [Figure 1] 1 is a diagram of a plant for producing hydrogen according to an embodiment of the process of the present invention. [Figure 2] 1 is a diagram of a plant for producing hydrogen according to an embodiment of the process of the present invention. [Figure 3] 1 is a diagram of a plant for producing hydrogen according to an embodiment of the process of the present invention.

[0050] Figure 1 shows the following main units: Ammonia Storage Unit 1 Pump 3 Evaporator 6 Ammonia recirculation evaporator 6B Combustion furnace 10 Adiabatic decomposition reactors 13, 17, 20 with catalyst beds 38, 39, 40 heat exchanger 22 Washing tower 24 Hydrogen Separation Unit 31 Distillation column 27 heating element 41

[0051] FIG. 1 discloses a diagram of a process in which ammonia 2 is decomposed to produce a hydrogen stream 50 .

[0052] A stream of liquid ammonia 2 is taken from an ammonia storage tank 1 and introduced via pump 3 into an evaporator 6 where the liquid ammonia is evaporated into a gaseous ammonia stream 7 .

[0053] The ammonia preheater / evaporator 6 may be a multi-stage heat exchanger. Each stage may be a separate device (separate heat exchanger), or multiple stages may be contained within a single device.

[0054] In some embodiments, the vaporizer 6 may optionally include a stage configured to recover heat from the purified hydrogen stream 50 product outlet from the hydrogen separation unit 31 after separation of the fuel portion 51, and / or the vaporizer 6 may include a stage configured to recover heat from the cracked gas downstream of the final ammonia decomposition step.

[0055] Gaseous ammonia 7 is mixed with recycled ammonia stream 43 (described below) and the ammonia feed 44 so obtained is subjected to a heating step in coils 101, 102 of combustion furnace 10 to produce preheated ammonia feed 12, which is then processed in first adiabatic decomposition reactor 13 to partially decompose the ammonia into nitrogen and hydrogen.

[0056] The output of the first adiabatic reactor 13 is a partially cracked stream 14 containing nitrogen, hydrogen, and uncracked ammonia, which is further heated in furnace 10, traverses coils 103 and 104, and is subjected to a second step of cracking in the second adiabatic cracking reactor 17.

[0057] The effluent stream 16 of the second adiabatic reactor 17 is reheated in furnace 10, traverses coil 105, and then undergoes a third step of decomposition in third adiabatic decomposition reactor 20. Third adiabatic reactor 20 is referred to as the final or last decomposition reactor. The output of last adiabatic decomposition reactor 20 is cracked vapor 21 containing nitrogen, hydrogen, and residual ammonia.

[0058] Decomposition stream 21 preferably has a temperature in the range of 400° C. to 500° C. Preferably, there is no more than 5% residual ammonia by volume in stream 21.

[0059] The decomposition of ammonia is carried out catalytically. Each adiabatic reactor contains at least one catalyst bed for this purpose. Adiabatic reactors 13, 17 and 20 contain at least one catalyst bed 38, 39 and 40, respectively.

[0060] Cracked stream 21 is cooled in heat exchanger 22 to a temperature of about 5° C. to about 60° C., preferably 5 to 50° C. Preferably, cooling is accomplished by direct quenching and / or indirect heat transfer using a cooling medium, which is preferably fresh liquid ammonia feed and / or water / steam.

[0061] In some embodiments, an additional heat exchanger (not shown) after heat exchanger 22 is configured to recover heat from the cracked stream for evaporation of the ammonia feed, and thus operates as a stage of ammonia evaporator 6.

[0062] After cooling, the decomposed stream is contacted with water 23 in a scrubber 24 to remove residual ammonia. The output of the scrubber 24 is an aqueous ammonia solution 25 and a scrubbed gas 26 containing nitrogen and hydrogen.

[0063] The scrubbed gas 26 is separated into a first portion 33 and a second portion 32. Preferably, the first portion 33 is a majority of the effluent 26 and the second portion 32 is a minor portion thereof. The first portion 33 is processed in a hydrogen separation unit 31 to obtain a hydrogen stream 50 and a tail gas 35.

[0064] The tail gas 35 contains nitrogen and a small amount of hydrogen. The tail gas 35 is recycled to the combustion furnace 10 for use as a fuel, preferably with a supplemental fuel stream as needed for combustion control purposes. The supplemental fuel preferably includes a portion 51 of the hydrogen product stream 50 and / or the second portion 32 of the scrubbed gas. Using a portion of the hydrogen 50 as fuel for the furnace 10 is advantageous for reducing carbon emissions.

[0065] The aqueous ammonia solution 25 effluent is preferably treated in distillation unit 27 to separate ammonia stream 29 from water 28. In some embodiments, all or a portion of ammonia solution 25 can bypass distillation unit 27 via line 30. Recycle ammonia stream 43 includes the ammonia stream 29 separated in unit 27 and, optionally, the bypass portion of line 30. Recycle stream 43 is combined with fresh ammonia 7 to form feed 44 for adiabatic reactors 13, 17, 20, as described above.

[0066] Recycle stream 43 is preferably liquid ammonia that is evaporated before mixing with fresh ammonia 7. In Figure 1, recycle stream 34 is evaporated in ammonia recycle evaporator 6B, which may be separate from main feed evaporator 6 or may be integrated as one stage, preferably the last stage, of evaporator 6. When ammonia recycle evaporator 6B is integrated as an ammonia recycle evaporation stage in evaporator 6, the injection point of stream 43 is located upstream of the stage.

[0067] It should be noted that the effluent of each reactor in the series is heated in one or more coils of furnace 10 before being sent to the next reactor in its entirety.

[0068] The number of heating coils in the furnace 10 may vary, for example the series of coils 101, 102 and 103, 104 may be replaced by a single coil or three or more coils as required and appropriately configured to optimize the overall heat exchange.

[0069] The coils 101 to 105 in the furnace 10 may be replaced by a bundle of tubes or other suitable heat exchange elements exposed to the high temperature fumes in the furnace and through which the stream to be heated traverses.

[0070] Figure 2 shows an embodiment that is a variation of Figure 1 in which the additional decomposition step is carried out in a bundle of catalyst tubes 36. Tubes 36 are filled with an ammonia decomposition catalyst and are externally heated by a combustion process in furnace 10. Partially decomposed stream 14, after being heated in coil 103, is decomposed in catalyst tubes 36 and then heated in coil 104 and processed in downstream reactors 17 and 20 to produce cracked gas 21. Other aspects of the process are similar to Figure 1.

[0071] 3 shows an embodiment in which the cracking process is carried out in a single adiabatic cracking reactor 37 containing catalyst beds 38, 39, and 40. Thus, the catalyst beds are provided in a single reactor instead of the separate pressure vessels 13, 17, 20 of FIGS.

[0072] Adiabatic reactor 37 also includes heating elements 41, 42 interposed between successive catalyst beds. Heating elements 41, 42 are preferably electric heaters configured to heat the effluent of a catalyst bed prior to the subsequent catalyst bed. The effluent of bed 38 is heated by heater 41 before entering bed 39, and the effluent of bed 39 is heated by heater 42 before entering bed 40.

[0073] In some embodiments, the heating elements 41, 42 may be heat exchangers and / or coils configured to recover heat from process streams and / or flue gases, which may be gases from the furnace 10 and / or gas turbine exhaust streams.

Claims

1. A process for producing hydrogen from ammonia (2), comprising ammonia decomposition in which a gaseous ammonia feed (7) is catalytically decomposed into hydrogen and nitrogen, wherein the ammonia decomposition is carried out in a series of ammonia decomposition steps (13, 36, 17, 20) in which the final decomposition stream (21) is the stream obtained after the series of final ammonia decomposition steps (20), The final ammonia decomposition step (20) is carried out adiabatically without supplying heat to the process flow during decomposition, and / or The final decomposition flow is quenched by direct mixing with water and / or steam after the final ammonia decomposition step (20). The series of ammonia decomposition steps includes a plurality of decomposition steps carried out in a series of adiabatic reactors connected in series, and optionally one or more decomposition steps in catalyst tubes so that the effluent from each reactor is further processed in the next reactor or in a bundle of catalyst tubes until the last reactor in the series generates the final decomposition flow (21), and an intermediate heating step in which the effluent from the reactors is heated before entering the next reactor in the series to provide heat for the endothermic decomposition of ammonia, wherein no further decomposition of ammonia is carried out during the heating step. Alternatively, the series of ammonia decomposition steps includes at least one decomposition step carried out in a bundle of externally heated catalyst tubes (36), wherein the process includes a parallel decomposition step carried out in parallel with the decomposition step in the catalyst tubes (36), and the parallel decomposition step is carried out adiabatically in a gas-heated reactor or in an adiabatic reactor.

2. The process according to claim 1, wherein the final decomposition flow (21) has a temperature of 700°C or less, or 650°C or less, or 550°C or less, or 450°C or less, after the final step (20) of decomposition, or after rapid cooling if such step is performed.

3. The process according to claim 1, wherein the temperature of the feed in each decomposition step is 300°C to 650°C.

4. The process according to claim 1, wherein the final decomposition flow (21) is cooled by indirect heat exchange (22) with one or more cooling fluids in one or more heat exchangers, the cooling fluids comprising a new liquid ammonia feed (2) which is heated and evaporated (6) to produce the gaseous ammonia feed (7), and / or water which is evaporated to produce vapor.

5. The process according to claim 1, wherein the heating step is carried out in a fuel combustion furnace (10).

6. The process according to claim 1, wherein at least one decomposition step performed in a bundle of externally heated catalyst tubes (36) precedes and / or follows one or more decomposition steps performed adiabatically in one or more catalytic reactors.

7. The process according to claim 1, wherein the parallel decomposition step is carried out in a gas-heated reactor, and the reactor is heated by the decomposition effluent from the catalyst tube.

8. The process according to claim 1, wherein the parallel decomposition step is carried out in a gas-heated reactor, and the effluent from the gas-heated reactor is cooled in a boiler or by rapid cooling.

9. The process according to claim 8, wherein the effluent from the gas-heated reactor is cooled in a boiler configured to provide heat for re-boiling the aqua ammonia solution distillation process and for pre-heating new ammonia, or the boiler is a re-boiler for an ammonia distillation column.

10. The process according to claim 1, wherein the new ammonia feed is initially adiabatically decomposed in one adiabatic reactor or a series of adiabatic reactors, a portion of the partially decomposed effluent in the one adiabatic reactor or the last reactor in the series is further decomposed in the catalyst tube, the remaining portion of the partially decomposed effluent is decomposed in a parallel reactor which is either an adiabatic reactor or a gas-heated reactor, and the effluent in the tube and the effluent in the parallel reactor are recombined to form a final decomposition flow.

11. The process according to claim 1, wherein the effluent from the catalyst tube (36) is rapidly cooled before or after the boiler.

12. The process according to claim 1, wherein the series of ammonia decomposition steps comprises a plurality of decomposition steps carried out adiabatically in a series of catalyst beds, the catalyst beds are housed in a single reactor (37) comprising a single pressure vessel, and the reactor comprises one or more inter-catalyst bed heaters (41, 42) configured to provide heat for the endothermic decomposition of ammonia.

13. The process according to claim 12, wherein the catalyst floor heater includes an electric heater, a heat exchanger configured to recover heat from process gas, and a heat exchanger configured to recover heat from flue gas.

14. The process according to claim 12, further comprising at least one decomposition step carried out in a catalyst tube heated from the outside.

15. The disassembly process is hybridized by providing an electrically generated heat input, preferably by using power from a renewable source, and the heat input is The heat required to re-boil the aqua ammonia solution, Heat for preheating or evaporating the liquid ammonia feed, The heat required to preheat the combustion air in the fuel combustion furnace, Heat to decompose ammonia and The process according to claim 1, comprising one or more of the following.

16. The process according to claim 1, wherein the process comprises adding a replenishment of hydrogen taken from a hydrogen storage or buffer system and added to the fuel gas system of the process to stabilize and control the ammonia decomposition process, the replenishment preferably performed during a startup procedure to sustain the startup process.

17. At least a portion of the fuel supply for the combustion furnace (10) is as follows: Tail gas (35) extracted from a hydrogen purification process (31) such as a pressure swing adsorption process, A portion of the hydrogen product (51), A portion of the gas (32) obtained by processing the final decomposition flow (21) in the washing tower (24), In some cases, a portion of the new ammonia feed after the preliminary decomposition step and The process according to claim 1, supplied by one or more of the following.

18. The process according to claim 1, wherein a portion of the fuel in the process is sent to a gas turbine, the exhaust gas from the turbine is used as a heat source in the ammonia decomposition process, and / or the exhaust gas from the turbine is used to generate steam for a steam turbine.

19. The process according to claim 1, wherein natural gas or another external fuel source is used to supplement the fuel gas of the process.

20. The process according to claim 1, wherein in the series of ammonia decomposition steps, all of the effluent from each decomposition step is sent to the next decomposition step.

21. The process according to claim 1, wherein a liquid ammonia feed is evaporated to produce the gaseous ammonia feed (7), and at least a portion of the heat for the evaporation of the liquid ammonia is recovered from the hydrogen product stream and / or the final decomposition stream.

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