Reactors, systems, and processes for the decomposition of ammonia

Abstract

An ammonia decomposition reactor comprising: one or more reaction tubes containing an ammonia decomposition catalyst; one or more fuel combustion elements for burning fuel in a fuel combustion zone surrounding one or more reaction tubes to provide thermal energy to assist in the decomposition of ammonia in one or more reaction tubes; and one or more electric heating elements for providing thermal energy to assist in the decomposition of ammonia in one or more reaction tubes, wherein one or more fuel combustion elements and one or more electric heating elements are provided in the same reactor to assist in the decomposition of ammonia in the same reaction tube, and together they form an electric-assisted fuel-combustion ammonia decomposition reactor.

Description

Technical Field

[0001] This specification relates to reactors, systems, and processes for catalytically decomposing ammonia to produce hydrogen gas.

Background Art

[0002] In various industrial settings, there is a new interest in using hydrogen as an environmentally friendly carbon-free fuel. Hydrogen can be burned to generate thermal energy or electricity. Alternatively, hydrogen can be used, for example, in fuel cells to generate electrochemical energy.

[0003] Ammonia has gathered interest as a compound that may enable the storage and transportation of hydrogen. Liquid ammonia has a higher hydrogen density than liquid hydrogen and can be transported using existing infrastructure already in use for this purpose, such as that used for transporting ammonia in the agrochemical fertilizer industry. Liquid ammonia can be burned directly after being transported or converted to hydrogen by a decomposition process.

[0004] The catalytic decomposition of ammonia into hydrogen and nitrogen has been known for many years. The reaction can be shown as follows.

[0005]

Chemical Formula

[0006] The ammonia decomposition reaction is endothermic and can be effectively achieved by passing ammonia over a suitable catalyst in a heated catalyst-containing reaction tube disposed within a furnace. For example, such furnaces for steam reforming of natural gas or naphtha feedstocks are known. In industrial processes used for the catalytic decomposition of ammonia, the gas produced by the ammonia decomposition reaction is purified to produce a purified hydrogen stream and a waste gas stream.

[0007] Improved processes for the catalytic cracking of ammonia are still needed. [Overview of the Initiative]

[0008] One issue to consider is the most effective way to heat the decomposition reactor to support the endothermic ammonia decomposition reaction. One option is to burn the exhaust gas stream from the ammonia decomposition system, which contains residual hydrogen, residual ammonia, and nitrogen. However, there is not enough energy from the exhaust gas combustion to achieve the desired reaction temperature.

[0009] The energy deficit from the combustion of exhaust gas streams has been suggested to be met by adding natural gas, ammonia, decomposition gas, hydrogen, or mixtures of these gases to the exhaust gas for combustion. However, each of these approaches has its drawbacks. Combustion of ammonia gas, decomposition gas, and / or the hydrogen produced reduces the amount of hydrogen-producing gas that can be generated from the ammonia gas introduced into the system. Combustion of natural gas is undesirable from the standpoint of environmental fossil fuel use or CO2 generation.

[0010] In contrast, the present invention proposes compensating for the energy shortage by burning waste off-gas using electrical energy. Accordingly, this specification describes an ammonia decomposition reactor, One or more reaction tubes containing an ammonia decomposition catalyst, One or more fuel combustion elements for burning fuel within a fuel combustion zone surrounding one or more reaction tubes to provide thermal energy to assist in the decomposition of ammonia in one or more reaction tubes, It comprises one or more electrically heated elements for providing thermal energy to assist in the decomposition of ammonia in one or more reaction tubes, The present invention provides an ammonia decomposition reactor in which one or more fuel combustion elements and one or more electric heating elements are provided in the same reactor to assist in the decomposition of ammonia within the same reaction tube, together forming an electric-assisted fuel combustion ammonia decomposition reactor.

[0011] The electric heating element is not limited to resistance heating, but also includes other electric heating means, such as induction and plasma heating.

[0012] This specification relates to the energization of a fuel-combustion type ammonia decomposition reactor. Here, a combination of waste off-gas combustion and electro-heating is used, which recovers calorific value from the waste gas, safely disposes of the waste gas, and reduces the electrical load compared to an electric-only system. This technology enables decarbonization of the ammonia decomposition process and reduces energy consumption through the combination of waste off-gas combustion and electro-heating. Electric heating can be applied in various forms, including thermal plasma, non-thermal plasma, induction heating, and resistance heating. In this process, waste gas containing up to 40% hydrogen is safely utilized. The hydrogen content of the waste gas depends on the amount of hydrogen in the hydrogen purifier (e.g., pressure swing adsorption unit) and the purifier tail gas that is led to be used as fuel in the ammonia decomposition reactor.

[0013] The energization of the ammonia decomposition reactor, combined with the combustion of waste off-gas, allows the desired catalyst temperature to be achieved using electricity. This eliminates the need for supplemental fuel (potentially ammonia supply, or either decomposition gas or hydrogen products) and improves the hydrogen efficiency / recovery of the process. Furthermore, the combustion of fuel produces NO x This process generates emissions such as N2O. By replacing part of the combustion load with electric heating, these emissions can be reduced, and therefore the environmental impact of the process can be reduced.

[0014] It should be noted that electric heating reactors are known as alternatives to fuel gas combustion reactors. However, according to this specification, electric and gas combustion heating are combined in a single ammonia decomposition reactor configuration, where electrical energy is provided to compensate for any energy deficiency provided by the combustion of fuel gas in the reactor, for example, allowing the combustion process to be fueled primarily or entirely by waste gas from the ammonia decomposition system. Furthermore, this single combined reactor solution may be less expensive than two separate reactors, one of which is electrically heated and the other heated by combustion.

[0015] The energization of a fuel combustion reactor can be achieved by various different methods, as described in more detail below. This specification also provides systems and processes for decomposing ammonia using an energized fuel combustion ammonia decomposition reactor. [Brief explanation of the drawing]

[0016] For a better understanding of the present invention and to illustrate how it can be implemented, certain embodiments of the present invention are described hereby by reference only to the accompanying drawings. [Figure 1] A schematic diagram of an ammonia decomposition reactor based on fuel combustion is shown. [Figure 2] A schematic diagram of an electrically assisted fuel combustion ammonia decomposition reactor, which has an electrically heated element in the combustion zone along with a gas burner, is shown. [Figure 3] A schematic diagram of an electrically assisted fuel combustion ammonia decomposition reactor is shown, which has an electrically heated element inside the reaction tube and a gas burner outside the reaction tube in the combustion zone. [Figure 4] A schematic diagram of an electrically assisted fuel combustion ammonia decomposition reactor equipped with a plasma torch instead of a conventional gas burner is shown. [Figure 5] A schematic diagram of an electrically assisted fuel combustion ammonia decomposition reactor with electrically heated catalytic combustion of exhaust gas in the combustion zone is shown. [Figure 6]A schematic diagram of an electric assist fuel combustion ammonia decomposition reactor having a single configuration for decomposition and combustion catalysts is shown. [Figure 7] A schematic diagram of an electric assist fuel combustion ammonia decomposition reactor including an electrically heated element within a reaction tube combined with a hydrogen combustion catalyst around the outside of the reaction tube is shown. [Figure 8] A schematic diagram of the electrical connection for an electric assist fuel combustion ammonia decomposition reactor including an electrically heated element within a reaction tube combined with a hydrogen combustion catalyst around the outside of the reaction tube is shown.

[0017] In all the figures, like reference numerals are used for like parts. A list of references is shown below.

[0018] Reference Item 2 Ammonia decomposition reactor 4 NH3 gas 6 Catalyst-containing reaction tube 8 Decomposed gas 10 Fuel 12 Gas burner 14 Combustion zone 16 Flue gas duct heat recovery (e.g., steam generation, superheating, or process heating) 18 Electric heater (within combustion zone) 20 Purifier (e.g., pressure swing adsorption unit) 22 Purified hydrogen gas stream 24 Waste gas stream (e.g., offgas waste <20% H2) 26 Electric heater (within reaction tube) 28 Catalyst-coated electric heating element (e.g., made by Catacel) 30 Plasma torch 32 Plasma torch electrode 34 Plasma plume 36 Combustion catalyst 38 Electric heater thermally coupled to combustion catalyst 40 Metal electrode of heating element 42 Ceramic support 44 Solder 46 Electrical insulator 48. Leak detector (e.g., ammonia sensor or pressure gauge) [Modes for carrying out the invention]

[0019] Figure 1 shows an example of a combustion ammonia decomposition reactor 2. The combustion ammonia decomposition reactor 2 is known and may include a fuel combustion zone 14 having a radiating section containing one or more fuel streams 10 and one or more burners 12 supplied with an oxidant-containing oxygen supply gas, such as air, oxygen-enriched air, or oxygen. The radiating section may include one or more catalyst-containing reaction tubes 6 through which the ammonia stream 4 passes and is decomposed to produce a hydrogen-containing decomposition gas stream 8. The combustion of one or more fuel streams 10 in one or more burners 12 in the fuel combustion zone produces thermal energy (e.g., radiant heat) to heat one or more catalyst-containing reaction tubes 6. Dozens or hundreds of catalyst-containing reaction tubes 6 may be present in the radiating section. If necessary, downstream of the radiating section, flue gas from the combustion of one or more fuel streams may be used to preheat one or more supply streams in a convection section 16. A reactor comprising a catalyst-containing radiating section containing catalyst-containing reaction tubes and a convection section for preheating the supply is known in steam methane reforming and can be applied to the present invention.

[0020] According to this specification, the configuration of the ammonia decomposition reactor shown in Figure 1 is modified to include electric heating combined with fuel gas combustion heating. In this regard, it should be noted that electric heating reactors are known as alternatives to fuel gas combustion reactors. However, according to this specification, electric and gas combustion heating are combined in a single ammonia decomposition reactor configuration, and the electrical energy is provided to compensate for any energy deficiency provided by the combustion of fuel gas in the reactor, for example, enabling the combustion process to be fueled primarily or entirely by exhaust gas from the system.

[0021] Figure 2 shows a schematic diagram of an electrically assisted fuel combustion ammonia decomposition reactor having an electrically heated element in the combustion zone along with a gas burner. In many respects, the ammonia decomposition reactor is similar to that shown in Figure 1. Ammonia feed gas 4 is supplied to a reaction tube 6, which contains an ammonia decomposition catalyst, to decompose ammonia to produce hydrogen-containing decomposition gas 8. Fuel gas 10 is supplied to a burner 12 to burn the fuel gas in a combustion zone 14 surrounding the reaction tube 6. Flue gas from the combustion can be used to preheat one or more feed streams 16.

[0022] A key difference between the configuration in Figure 1 and the configuration in Figure 2 is that the configuration in Figure 2 includes one or more electrically heated elements 18 to provide additional heat to the reaction tube. In the configuration in Figure 2, the electrically heated elements 18 are located within the combustion zone surrounding the reaction tube. One advantage of this configuration is that less thermal energy is required from the burner to reach the desired reaction temperature in the reaction tube. This, therefore, makes it possible to fuel the burner entirely or at least primarily with waste gas from the system without requiring a large amount of additional fuel. As shown in Figure 2, the decomposition gas 8 can be sent to a purifier 20, such as a pressure swing adsorption unit. The purifier 20 produces a purified hydrogen gas stream 22 and a waste gas stream 24 containing nitrogen and a mixture of residual ammonia and nitrogen (e.g., off-gas waste <20% H2). The waste gas 24 can be recycled and used as fuel 10 for combustion in the combustion zone of the reactor. Since the heating of the reaction tube 6 is supplemented by the electric heating element 18, it becomes possible to supply the majority of the fuel burned by the burner 12 (e.g., at least 50%, 60%, 70%, 80%, 90%, 95%, or 100%) with recycled waste gas 24.

[0023] Figure 2 shows an upper combustion reactor with an electric heating element (i.e., a reactor with burner 12 at the top of the reactor), but it should be noted that other burner configurations, such as bottom or side combustion reactors, are possible.

[0024] Figure 3 shows a schematic diagram of another electrically assisted fuel combustion ammonia decomposition reactor having an electrically heated element inside the reaction tube and a gas burner outside the reaction tube in the combustion zone. This configuration is similar to that shown in Figure 2, and for brevity, common features are not repeated here. The main difference here is that the electrically heated element 26 is located inside the reaction tube rather than in the combustion zone. The electrically heated element 26 may take the form of a catalyst-coated component 28, as shown in Figure 3. This configuration can reduce the electrical load due to the fact that electric heating is provided directly to the catalyst component.

[0025] In the configurations shown in Figures 2 and 3, one or more electric heating elements are provided within the fuel combustion zone and / or within one or more reaction tubes. The electric heating elements may provide thermal energy to assist (e.g., via resistance heating) the decomposition of ammonia in one or more reaction tubes, rather than driving the combustion of the fuel. In contrast, it is also possible to provide one or more electric heating elements integrated with one or more fuel combustion elements, resulting in one or more electric heating elements driving the combustion of the fuel, as discussed below.

[0026] Figure 4 shows a schematic diagram of another electrically assisted fuel combustion ammonia decomposition reactor equipped with a plasma torch 30 instead of a conventional gas burner. In this case, the fuel burner and electric element are integrated into the plasma torch 30, rather than having a separate fuel gas burner and resistance electric heating element. As shown in Figure 4, the plasma torch has a fuel gas inlet 10 and an electrode 32 for generating a plasma plume 34. It should be noted that in this plasma torch configuration, the gas supplied to the fuel gas inlet does not have to be a typical combustible fuel, but may be, for example, air, off-gas, or any other gas suitable for forming a plasma plume 34. Waste off-gas can be added before or after the plasma plume. The latter method is NO x This would be preferable because it results in less formation of [unclear]. In other respects, the structure is the same as described above, and for the sake of brevity, common features will not be repeated here.

[0027] Figure 5 shows a schematic diagram of another electrically assisted fuel combustion ammonia decomposition reactor with electrically heated catalyst-assisted combustion of waste gas in the combustion zone. In this case, the gas burner can be replaced with an oxidizing combustion catalyst 36 and an electric heater 38 to drive the combustion of fuel gas in the combustion zone. At startup, the oxidizing catalyst can be heated electrically to, for example, 700°C. This temperature is sufficient for ammonia and hydrogen to be oxidized without forming significant amounts of NOx. The energy deficit from burning the waste off-gas can be compensated for by the electric heater during the normal operation of the ammonia decomposition reactor.

[0028] In Figure 5, the combustion catalyst 36 and the electric heater element 38 are located at the fuel gas inlet of the combustion zone. In contrast, in the configuration of Figure 6, the combustion catalyst 36 and the electric heater element 38 are located around the outside of the reaction tube 6. In this case, both the decomposition catalyst and the combustion catalyst can be located in a single unit, when the electrically heated oxidation catalyst is located around the ammonia decomposition catalyst. In yet another configuration, as shown in Figure 7, the electric heater elements 26, 28, and 38 are ammonia decomposition catalyst coating elements located inside the reaction tube 6 in a manner similar to the configuration of Figure 3, which has the combustion catalyst 36 located around the reaction tube. Here again, in other respects, the configurations of Figures 5 to 7 are similar to those described above, and common features are not repeated here for brevity. Furthermore, the embodiments shown in Figures 3 and 7 can be modified to replace the electrically charged CATACEL® type ammonia decomposition catalyst with a catalyst coated on a conductive structured ceramic support. In this case, doped ceramics such as silicon carbide, molybdenum disilide, lanthanum chromate, zirconium oxide, silicon nitride, and other conductive materials can be used as catalyst supports.

[0029] Figure 8 shows the electrical connection configuration for an electrically assisted fuel combustion ammonia decomposition reactor, including energized heating elements 40, 42, and 44 inside the reaction tube, combined with a hydrogen combustion catalyst 36 around the outside of the reaction tube. The energized heating elements include metal electrodes 40 connected to a conductive ceramic support 42 via a welding / joining / soldering material 44. To avoid the formation of contact resistance between the metal and ceramic materials, it is desirable to weld the metal electrodes 40 of the heating elements to the conductive ceramic support 42 with solder 44. The metal-ceramic joint can be located inside or outside the reaction zone of the reactor. The latter option helps to reduce / avoid the generation of thermal stress between the joining materials and eliminates the possibility of chemical reactions between the solder (or other welding / joining material) and the gas mixture. However, in this case, the ceramic support may have two parts: a non-porous segment connected to the metal electrodes 40 of the heating elements and a porous segment coated with the ammonia decomposition catalyst 28. Electrical insulators 46 graded for high-pressure operation (e.g., spark plug ceramics) can be used to insulate the electricity supplied to the inside of the pressurized reactor via the energized heating elements 40, 42, and 44. For safety reasons, an additional chamber, as shown in Figure 8, equipped with, for example, an ammonia sensor or a pressure gauge 48, can be installed to indicate any possible leaks from the pressurized reactor.

[0030] In light of the above, it will be understood that the energization of the fuel combustion ammonia decomposition reactor can be achieved by various different methods. One or more electric heating elements can be included within the combustion zone of the ammonia decomposition reactor (Figure 2). One or more electric heating elements can be included in one or more reaction tubes of the ammonia decomposition reactor. For example, the electric elements can be coated with an ammonia decomposition catalyst and placed inside the reaction tube (Figure 3). • The gas burner can be replaced with an electrically driven plasma torch in the combustion zone (Figure 4). The gas burner can be replaced with an oxidative combustion catalyst and an electric heater to drive the combustion of the fuel gas. The electric heater and combustion catalyst can be arranged in several different configurations, including the following: • The combustion catalyst and electric heater elements are positioned at the fuel gas inlet of the combustion zone (Figure 5). • The combustion catalyst and electric heater elements are arranged around the outside of the reaction tube (Figure 6). • An electric heater element is placed inside the reaction tube, and the combustion catalyst is placed around the outside of the reaction tube (Figure 7).

[0031] In all of these configurations, the ammonia decomposition reactor comprises one or more reaction tubes containing an ammonia decomposition catalyst, one or more fuel combustion elements for burning fuel in a fuel combustion zone surrounding one or more reaction tubes to provide thermal energy to assist in the decomposition of ammonia in one or more reaction tubes, and one or more electric heating elements for providing thermal energy to assist in the decomposition of ammonia in one or more reaction tubes. The electric heating elements may be provided as separate elements from the fuel combustion elements to provide additional thermal energy to assist in the decomposition of ammonia in one or more reaction tubes. Alternatively, the electric heating elements may be integrated with the fuel combustion elements such that the electric heating elements drive the combustion of fuel to assist in the decomposition of ammonia in one or more reaction tubes.

[0032] Electric heating elements can reduce fuel consumption and, for example, allow exhaust gases from the system to be used as the primary or sole fuel source for the fuel combustion element. Furthermore, the configurations described herein can, additionally or alternatively, increase the flexibility of the types of fuels available. This may be particularly useful when starting an ammonia decomposition reactor when hydrogen-containing exhaust gases or product gases are not yet available for combustion as fuel for the decomposition reactor. In this case, it would be advantageous to be able to utilize an ammonia source gas to fuel the decomposition reactor during system startup, at least when only ammonia may be available as fuel. Experimental studies have shown that when using 100% ammonia fuel, the burner in a standard combustion ammonia decomposition reactor will not ignite (i.e., no flame will be formed). In contrast, this specification allows for the use of an electric heating element to ignite the ammonia fuel for starting the ammonia decomposition unit. Thus, the configurations according to this specification can provide advantages in starting the ammonia decomposition reactor system, as well as advantages in long-term operation of the ammonia decomposition reactor system, including reduced fuel consumption, reduced emissions, and / or reduced operating costs.

[0033] The ammonia decomposition catalyst in the catalyst-containing reaction tube can be any ammonia decomposition catalyst. For example, a nickel catalyst and / or a ruthenium catalyst may be used. A preferred catalyst is a nickel catalyst. The catalyst may contain 3 to 30% by weight of nickel, preferably 8 to 20% by weight, expressed as NiO, on a suitable refractory carrier, such as alumina or a metallic aluminate. The catalyst may be in the form of pelletized units, which may contain one or more through-holes, or it may be provided as a washcoat on a structured metal or ceramic catalyst. A particularly preferred catalyst is KATALCO, available from Johnson Matthey PLC. RTM The material is 27-200MQ, which contains 16% by weight of nickel, expressed as NiO, on cylindrical pellets formed from a high-surface-area calcium aluminate support.

[0034] The input ammonia stream may be heated before being supplied to the electrically charged ammonia decomposition reactor. Therefore, the process of the present invention may include a step of heating the input ammonia stream. The input ammonia stream may be heated to a temperature above 350°C, above 400°C, above 450°C, above 500°C, or above 550°C. The input ammonia stream may be heated to a temperature below 1000°C, below 950°C, below 850°C, below 750°C, or below 700°C. The input ammonia stream may be heated to a temperature between 350°C and 1000°C, 400°C and 950°C, 450°C and 850°C, or 500°C and 750°C, for example, between 550°C and 700°C.

[0035] The temperature of the hydrogen-containing stream exiting one or more catalyst-containing reaction tubes affects the equilibrium position of the decomposition reaction and may be in the range of 500 to 950°C. When nickel catalysts are used in one or more catalyst-containing reaction tubes, the temperature of the hydrogen-containing stream exiting one or more catalyst-containing reaction tubes may preferably be higher than about 700°C.

[0036] The inlet pressure to one or more catalyst-containing reaction tubes is set by the flow sheet design and may be in the range of 1 to 100 bar absolute pressure, preferably 10 to 90 bar absolute pressure, for example, 31 to 51 bar absolute pressure.

[0037] The hydrogen-containing stream from the reactor can be supplied to one or more purification units to increase the hydrogen content of the hydrogen-containing stream and generate a hydrogen-enriched stream and a tail gas stream. An example of a purification unit is a pressure swing adsorption unit that increases the H2 content by separating H2 from other components. The tail gas stream can be recycled and burned as fuel in the combustion zone of the main reactor.

[0038] It may be preferable to supply the hydrogen-containing stream to a steam generation unit and / or heat recovery zone before supplying the hydrogen-containing stream to one or more purification units. As will be understood by those skilled in the art, the steam generation unit and / or heat recovery zone may be used to recover low or moderate amounts of heat.

[0039] The hydrogen-enriched stream after purification may contain 70 mol% or more of H2, 75 mol% or more of H2, 80 mol% or more of H2, 85 mol% or more of H2, or 90 mol% or more of H2. The hydrogen-enriched stream may contain 100 mol% or less of H2. For example, the hydrogen-enriched stream may contain 70 mol% to 100 mol% of H2, 75 mol% to 100 mol% of H2, 80 mol% to 100 mol% of H2, 85 mol% to 100 mol% of H2, or 90 mol% to 100 mol% of H2. Preferably, the hydrogen-enriched stream may contain more than 90 mol% of H2, more than 95 mol% of H2, more than 98 mol% of H2, or more than 99 mol% of H2. More preferably, the hydrogen-enriched stream may contain more than 99.9 mol% of H2, more than 99.95 mol% of H2, or about 100 mol% of H2. Most preferably, a stream containing high-concentration hydrogen may contain more than 99.95 mol% H2 or about 100 mol% H2.

[0040] Although the present invention has been specifically illustrated and described with reference to certain examples, it will be understood by those skilled in the art that various modifications of form and detail can be made without departing from the scope of the invention as defined by the appended claims.

Claims

1. It is an ammonia decomposition reactor, One or more reaction tubes containing an ammonia decomposition catalyst, One or more fuel combustion elements for burning fuel within a fuel combustion zone surrounding one or more reaction tubes to provide thermal energy to support the decomposition of ammonia within the one or more reaction tubes, The system comprises one or more electrically heated elements for providing thermal energy to support the decomposition of ammonia in one or more reaction tubes, An ammonia decomposition reactor in which one or more fuel combustion elements and one or more electric heating elements are provided in the same reactor to assist in the decomposition of ammonia in the same reaction tube, and together they form an electric-assisted fuel combustion ammonia decomposition reactor.

2. The ammonia decomposition reactor according to claim 1, wherein one or more of the electric heating elements are provided within the fuel combustion zone.

3. The ammonia decomposition reactor according to claim 1 or 2, wherein one or more of the electric heating elements are provided inside one or more reaction tubes.

4. An ammonia decomposition reactor according to any one of the preceding claims, wherein one or more of the electrically heated elements provide thermal energy to assist in the decomposition of ammonia in one or more reaction tubes via resistance heating, rather than driving the combustion of the fuel.

5. The ammonia decomposition reactor according to claim 3 or 4, wherein the electrically heated element is coated with the ammonia decomposition catalyst in one or more reaction tubes.

6. The ammonia decomposition reactor according to any one of the preceding claims, wherein one or more of the electric heating elements are integrated with one or more of the fuel combustion elements so as to drive the combustion of the fuel.

7. The ammonia decomposition reactor according to claim 6, wherein one or more of the electric heating elements are integrated with one or more of the fuel combustion elements as one or more plasma torches equipped with electric electrodes.

8. The ammonia decomposition reactor according to claim 6 or 7, wherein one or more of the electric heating elements are integrated with one or more of the fuel combustion elements as one or more electric heating elements and one or more combustion catalyst elements, and drives the combustion of the fuel via electric heating catalyst-assisted combustion of the fuel.

9. The ammonia decomposition reactor according to claim 8, wherein the aforementioned or each electric heating element is arranged on or around the aforementioned or each combustion catalyst element.

10. The ammonia decomposition reactor according to claim 8 or 9, wherein the above or each electric heating element and the above or each combustion catalyst element are arranged around the outside of the one or more reaction tubes containing the ammonia decomposition catalyst.

11. The ammonia decomposition reactor according to claim 8, wherein the above or each electric heating element is arranged in the one or more reaction tubes containing the ammonia decomposition catalyst, and the above or each combustion catalyst element is arranged around the outside of the one or more reaction tubes.

12. A system for producing hydrogen by catalytic decomposition of ammonia, An ammonia decomposition reactor according to any one of the preceding claims, which uses a combination of electrical energy and combustion energy to decompose an ammonia gas input stream and generate a hydrogen-containing gas stream, A system comprising a purification unit that increases the hydrogen content of the hydrogen-containing gas stream.

13. The system according to claim 12, wherein the purification unit is configured to generate a purified hydrogen gas stream and a waste gas stream, and the system is configured to guide the waste gas stream from the purification unit to the combustion zone of the ammonia decomposition reactor, thereby supplying at least partially fuel to the ammonia decomposition reactor.

14. A process for decomposing ammonia using the system according to claim 12 or 13, The ammonia gas input stream is supplied to the ammonia decomposition reactor, and the ammonia gas input stream is decomposed using a combination of electrical energy and combustion energy to generate a hydrogen-containing gas stream. A process comprising purifying the hydrogen-containing gas stream to increase the hydrogen content of the hydrogen-containing gas stream.

15. The process according to claim 14, wherein the purification unit generates a purified hydrogen gas stream and a waste gas stream, and the waste gas stream from the purification unit is guided to the combustion zone of the ammonia decomposition reactor to supply fuel to the main ammonia decomposition reactor at least partially.

16. The process according to claim 14 or 15, wherein the system is started by supplying ammonia fuel to one or more fuel combustion elements of the ammonia decomposition reactor and igniting the ammonia using one or more electric heating elements.

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