Method and system for carbon oxide free hydrogen production

Abstract

The present disclosure relates to a method of carbon oxide free hydrogen production. The method comprises the steps of:-heating a gaseous stream of a reaction compound comprising hydrogen atoms in the absence of an oxidizing agent to thermally decompose the reaction compound into smaller product compounds comprising hydrogen molecules, thereby obtaining a stream of decomposed product compounds; -separating the hydrogen molecules from other product compounds of the stream of decomposition product compounds; -reacting a portion of the separated stream of hydrogen molecules with an oxidizing agent, in particular a stream of oxygen or air, to obtain a combustion product compound in a stream of combustion product compounds, the combustion product compound comprising steam and heat; a step of supplying the heat obtained in the previous step to the heating reaction compound; and wherein the process may comprise the step of recovering energy from the stream of decomposition product compounds and / or from the stream of combustion product compounds. In addition, a hydrogen production system configured to operate according to the above method is also disclosed.

Description

[0001] SPECIFICATION TECHNICAL FIELD

[0002] The present disclosure relates to hydrogen production on an industrial scale. The embodiments disclosed herein relate specifically to methods and systems for producing hydrogen that do not entail any production of carbon oxides as byproducts. Additionally, the present disclosure relates to methods and systems for producing hydrogen that include recovering energy generated by the chemical reactions involved to additionally reduce the production of carbon oxides through ancillary processes and equipment, while reducing the need for external energy sources. BACKGROUND

[0003] Hydrogen is emerging as a new energy carrier and viable fuel route. This is not only because hydrogen is the least polluting fuel, but also because different energy sources can be used to produce hydrogen, and also because hydrogen can meet many energy needs, including residential applications, hydrogen fuel cell vehicles, energy carriers, and integrated heating and power systems.

[0004] However, there are technical challenges to hydrogen production technology, including feedstock type, conversion efficiency, carbon emissions, energy intensity of the production process, and the need for safe integration of H2 production systems with H2 purification and storage technologies.

[0005] Hydrogen production can be based on renewable energy (so-called green hydrogen); on coal gasification and natural gas with systems for capturing carbon emissions (CCS: Carbon Capture Systems) (blue hydrogen); and on conventional fossil fuels (grey hydrogen). Currently, most hydrogen is produced via a CO2-intensive steam methane reforming process. Electrolysis is a typical method that uses an electric current to separate water into oxygen and hydrogen, and produces green hydrogen without any direct carbon dioxide emissions. Renewable energy can be used to generate the necessary electricity. The cost of producing hydrogen, particularly green hydrogen, is a significant barrier. The cost of manufacturing hydrogen using steam reforming is about three times the cost of producing one unit of energy using natural gas. The cost of producing hydrogen using electrolysis with 5 cents / kWh of energy is almost twice that of using natural gas to produce hydrogen. Lower hydrogen concentrations can be transported via existing natural gas pipeline infrastructure, which will also help to reduce CO2 emissions from existing natural gas reforming equipment.

[0006] Both methods have a negative impact on the operating costs of the system and can have adverse environmental impacts.

[0007] The thermal decomposition of methane or ammonia in the absence of oxygen, or more generally in the absence of oxidants or oxidizing agents, appears to be a potential candidate for H2 production. However, thermal decomposition is an energy-intensive process and current technologies still involve direct and indirect CO2 emissions.

[0008] Therefore, an improved system and method for hydrogen production by thermal decomposition of methane or ammonia into H2 in the absence of oxidants, in particular in the absence of oxygen, which has a high selectivity for H2 and no CO2 emissions, would be beneficial and would be welcome in the art.

[0009] Preferably, the system and method for hydrogen production according to the present disclosure allows recovering the energy generated by the chemical reactions involved to additionally reduce the production of carbon oxides by auxiliary processes and devices, while reducing the need for external energy sources. SUMMARY

[0010] In one aspect, the subject matter disclosed herein relates to an efficient carbon-oxide-free method for the continuous generation of H2 from a reaction compound or a mixture of reaction compounds, the reaction compound comprising hydrogen atoms, without promoting side reactions. In particular, the reaction compound can be selected from ammonia or fossil fuels.

[0011] In particular, the hydrogen generation process comprises the thermal decomposition of one or more reaction compounds in the absence of oxidants to obtain hydrogen and other product compounds of the reaction compound, which are smaller than the reaction compound. The hydrogen is subsequently separated from the other product compounds, and a portion of the separated hydrogen is reacted with an oxidant, in particular oxygen or air, to produce heat, which is used to sustain the thermal decomposition reaction. In particular, energy recovery can be obtained from the high temperature and / or high pressure of the products of the above-mentioned reaction. The thermal decomposition reaction can be carried out in the presence of a catalyst.

[0012] In another aspect, the reaction compound can be ammonia, and the heating step is operated to heat the reaction compound at a temperature higher than 400°C, preferably higher than 450°C, or to heat the reaction compound in the presence of a catalyst at a temperature higher than 200°C, and the catalyst is based on a transition metal, preferably: Ru, Ni, Co or Fe and their bi-metallic, inter-metallic or tri-metallic compounds; supported on a material selected from the group consisting of: alumina, silica, zirconia and carbon materials and mixtures thereof. Alternatively, the catalyst can be supported on a material selected from the group consisting of: carbon nanotubes (CNT), activated carbon, carbon black, graphite, graphene, doped carbon, typically nitrogen-doped carbon; preferably carbon nanotubes.

[0013] In one aspect, the reaction compound can be an organic compound, preferably a hydrocarbon, more preferably natural gas, still more preferably methane. If the reaction compound is methane, the heating step is operated to heat the reaction compound at a temperature higher than 547°C, preferably higher than 760°C, or to heat the reaction compound at a temperature higher than 200°C in the presence of a catalyst, and the catalyst can be based on: iron, nickel and their bimetallic formulations, and deposited on alumina or carbon. In particular, when the reaction compound is methane, then the catalyst is a carbon-based material, preferably carbon black.

[0014] In another aspect, the subject matter disclosed herein relates to a system for hydrogen production from thermal decomposition of a reaction compound comprising hydrogen atoms in the absence of an oxidizing agent, the system comprising a reactor comprising two separate reaction zones: a thermal decomposition zone for cracking the reaction compound into H2 and a zone for generating heat by hydrogen combustion with an oxidizing agent, in particular oxygen or air. The heat for the thermal decomposition reaction is generated by combustion of a portion of the hydrogen gas produced in the thermal decomposition zone. The combustion reaction releases steam and reaches high combustion efficiency.

[0015] A further aspect of the present disclosure relates to a system for hydrogen production from thermal decomposition of a reaction compound comprising hydrogen atoms in the absence of an oxidizing agent to obtain smaller product compounds comprising hydrogen molecules, wherein the system further comprises: an energy recovery unit downstream of the thermal decomposition reaction zone to recover energy from a stream of decomposition product compounds, and / or downstream of the combustion reaction zone to recover energy from a stream of combustion product compounds; and a separation device downstream of the energy recovery unit or the thermal decomposition reaction zone for separating hydrogen gas and gaseous by-products from non-gaseous product compounds, a hydrogen gas recirculation line being configured to extract at least a portion of the stream of hydrogen gas from the separation device and direct it to the combustion zone of the reactor.

[0016] According to one embodiment, the system can comprise an additional energy recovery unit connected downstream of the zone for generating heat by hydrogen combustion for recovering energy from a stream of combustion product compounds.

[0017] According to another embodiment, the energy recovery unit and the additional energy recovery unit can be part of an energy recovery module configured to be connected at least downstream of the thermal decomposition reaction zone to recover energy from a stream of decomposition product compounds, and downstream of the zone for generating heat by hydrogen combustion to recover energy from a stream of combustion product compounds.

[0018] According to another embodiment, the system can comprise a gas-gas separator connected downstream of the separation device for separating a stream of hydrogen gas and a stream of other gaseous components. Attached Figure Description

[0019] When considered in conjunction with the accompanying drawings, the embodiments disclosed in this invention and their many accompanying advantages will become better understood by referring to the following detailed description, thereby readily providing a more comprehensive understanding of them, wherein:

[0020] - Figure 1 A schematic diagram of a system according to a first embodiment is shown, which produces hydrogen by thermally decomposing a reactive compound or mixture of reactive compounds containing hydrogen atoms in the absence of an oxidant, and recycles a portion of the produced hydrogen to react with an oxidant (particularly oxygen and / or air) to generate heat to be supplied to the thermal decomposition reaction.

[0021] - Figure 2 A schematic diagram of a system for producing hydrogen by thermal decomposition in the absence of an oxidant, according to the second embodiment, is illustrated; and

[0022] - Figure 3 A schematic diagram of a system for producing hydrogen by thermal decomposition in the absence of an oxidant, according to a third embodiment, is shown. Detailed Implementation

[0023] According to one aspect, this subject matter relates to systems and methods for producing hydrogen by including the following steps:

[0024] - Heating a gas stream containing hydrogen atoms in the absence of an oxidizing agent thermally decomposes the reaction compound into smaller product compounds containing hydrogen molecules, thereby obtaining a stream of decomposition product compounds;

[0025] - Separate the stream of hydrogen molecules from the stream of other product compounds of the decomposition product compounds;

[0026] - To react a portion of the separated hydrogen molecules with a stream of oxidant, particularly oxygen or air, to obtain steam and heat in the stream of combustion product compounds; and

[0027] - The heat obtained in the previous step will be used for the step of heating the reaction compound.

[0028] In particular, according to this disclosure, the method may also include the following steps:

[0029] -Recover energy from the stream of decomposition product compounds and / or from the stream of combustion product compounds.

[0030] According to another approach, the step of recovering energy from a stream of decomposition product compounds may include expanding the stream of decomposition product compounds to generate work.

[0031] According to yet another aspect, the step of recovering energy from the stream of combustion product compounds can comprise expanding the stream of combustion product compounds to produce work.

[0032] According to one aspect, the energy recovered from the step of recovering energy from the stream of decomposition product compounds and / or from the stream of combustion product compounds can be used at least partially to compress and heat the stream of reaction compounds comprising hydrogen atoms and / or the stream of separated hydrogen molecules and / or the stream of oxidizing agent.

[0033] According to another aspect, the step of heating the reaction compounds comprising hydrogen atoms to thermally decompose the reaction compounds in the absence of an oxidizing agent can be performed in the presence of a catalyst, which can be provided as a fixed bed or as a fluidized bed. In particular, when the reaction compounds are ammonia, the catalyst can be based on transition metals, preferably: Ru, Ni, Co or Fe and their bi- or tri-metallic compounds, and the catalyst can be supported on a material selected from the group consisting of: alumina, silica, zirconia and carbon materials and mixtures thereof, in particular carbon nanotubes (CNT), activated carbon, carbon black, graphite, graphene, doped carbon, typically nitrogen-doped carbon; preferably, the catalyst is based on carbon nanotubes. When the reaction compounds are organic compounds, most preferably natural gas or methane, the catalyst can be based on: iron, nickel and their bi-metallic formulations, the catalyst can be deposited on alumina or carbon, preferably carbon black. Carbon black can also be used as catalyst alone, in particular in a fluidized bed reactor.

[0034] According to another aspect, the present subject-matter relates to a system for hydrogen production from thermal decomposition of reaction compounds comprising hydrogen atoms in the absence of an oxidizing agent to obtain smaller product compounds comprising hydrogen molecules, wherein the system comprises:

[0035] - a reactor comprising a first reaction zone and a second reaction zone configured to exchange heat between each other, the first reaction zone having an inlet of a stream of reaction compounds and an outlet of a stream of decomposition product compounds comprising hydrogen gas, and the second reaction zone comprising a first inlet of a stream of hydrogen gas and a second inlet of a stream of oxidizing agent, in particular oxygen or air, a burner and an outlet of a stream of combustion product compounds, the combustion product compounds comprising steam, steam and oxygen, or steam and air; and

[0036] - a hydrogen gas recirculation line downstream of the first reaction zone of the reactor for recirculating at least a portion of the hydrogen gas of the stream of decomposition product compounds from the first reaction zone of the reactor to the second reaction zone of the reactor, in which second reaction zone at least a portion of the hydrogen gas reacts with the oxidizing agent, in particular oxygen or air.

[0037] According to one aspect, the system may further include an energy recovery unit connected downstream of the first reaction zone of the reactor for recovering energy from the stream of decomposition product compounds; and / or an additional energy recovery unit connected downstream of the second reaction zone of the reactor for recovering energy from the stream of combustion product compounds; and / or a separation device for separating the gaseous stream containing hydrogen and gaseous byproducts from the non-gaseous product compounds from the stream of decomposition product compounds from the first reaction zone of the reactor.

[0038] According to another approach, the system may additionally include a condenser, located downstream of the second reaction zone of the reactor or downstream of the additional energy recovery unit, for condensing the vapor of the combustion product compound stream and separating oxygen from water. Specifically, an oxidant recirculation line, particularly an oxygen recirculation line, is present to recirculate oxygen to the second reaction zone of the reactor.

[0039] According to another aspect, the system may additionally include a gas-gas separator downstream of the outlet of the separation unit for separating the hydrogen stream from the gas stream of the separation unit from the stream of other gas components. In particular, the gas-gas separator may be a pressure swing absorber.

[0040] It will be apparent to those skilled in the art that the methods and systems of this disclosure allow for hydrocarbon-free production compared to existing solutions such as natural gas combustion-assisted pyrolysis reactors, plasma reactors, and electrically heated reactors. Furthermore, it will be apparent that the possibility of recovering energy generated by the chemical reactions involved allows for an additional reduction in the production of carbon oxides through auxiliary processes and apparatus, while simultaneously reducing the need for external energy. The reactors of this disclosure can be equipped with tube bundles to deliver H2 combustion products (steam) and heat the pyrolysis reaction zone. Therefore, any direct contact between the steam and the compounds to be pyrolyzed is avoided, thus suppressing side reactions and leading to maximization of H2 selectivity. Additionally, the reactors of this disclosure can be packed with a solid catalyst to increase the reaction rate and achieve higher yields and / or operate at lower temperatures. Moreover, by separating the pyrolysis reaction zone from the combustion reaction zone, the systems of this disclosure can operate at pressures ranging from 1 atm to 100 atm, preferably between 30 atm and 50 atm, but also allow for operation at atmospheric pressure.

[0041] Reference will now be made in detail to the embodiments of the present disclosure, one or more examples of which are illustrated in the accompanying drawings. Each example is provided by way of explanation of the present disclosure and not limitation thereof. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present disclosure without departing from the scope or spirit of the disclosure. References throughout this specification to "one embodiment" or "an embodiment" mean that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the disclosed subject matter. Thus, the appearance of the phrases "in one embodiment" or "in some embodiments" in various places throughout this specification are not necessarily referring to the same embodiment. Furthermore, the particular features, structures, or characteristics can be combined in any suitable manner in one or more embodiments.

[0042] When introducing elements of various embodiments, the articles "a," "an," "the," and "said" are intended to mean that there are one or more of the elements. The terms "comprising," "including," and "having" are intended to be inclusive and mean that there can be additional elements other than the listed elements.

[0043] Reference will now be made to the drawings, in which Figure 1A schematic representation of an exemplary system 10 for hydrogen production by thermal decomposition of a reaction compound or a mixture of reaction compounds comprising hydrogen atoms in the absence of an oxidizing agent and recycling a portion of the produced hydrogen gas to react with an oxidizing agent, in particular oxygen and / or air, to produce heat to be provided to the thermal decomposition reaction, according to a first embodiment, is shown. In particular, the system 10 comprises a reactor 11 composed of a first reaction zone 12, within which a reaction compound or a mixture of reaction compounds comprising hydrogen atoms is thermally decomposed into smaller product compounds comprising hydrogen molecules, and a second reaction zone 13, in which hydrogen reacts with an oxidizing agent, in particular oxygen or air, to obtain a combustion product compound comprising steam, or steam and air, or steam and oxidizing agent, in particular oxygen. The two reaction zones 12, 13 are configured to exchange heat between each other, the first reaction zone 12 comprises an inlet 121 of a stream of reaction compounds and an outlet 122 of a stream of product compounds comprising hydrogen gas, and the second reaction zone 13 comprises a first inlet 131 of a stream of hydrogen gas and a second inlet 132 of a stream of oxidizing agent, in particular oxygen or air, a burner 133 and an outlet 134 of a stream of steam, steam and oxygen or steam and air. In particular, the hydrogen gas fed to the second reaction zone 13 of the reactor 11 through the first inlet 131 is recycled from a portion of the hydrogen gas obtained by thermal decomposition in the first reaction zone 12 of the reactor 11. To this end, a hydrogen gas recycling line 16 is connected downstream of the outlet 122 of the first reaction zone 12 of the reactor 11 to withdraw a portion of the hydrogen gas of the stream of decomposition product compounds from the first reaction zone 12 of the reactor 11 and direct the portion of the hydrogen gas of the stream of decomposition product compounds to the first inlet 131 of the second reaction zone 13 of the reactor 11. The first reaction zone 12 can comprise a catalyst and can be configured as a fixed bed reactor or a fluidized bed reactor. To recover energy from the high temperature and high pressure of the products of the stream of decomposition product compounds from the first reaction zone 12 of the reactor 11, an expander 30 is arranged downstream of the outlet 122 of the first reaction zone 12 of the reactor 11 and upstream of the hydrogen gas recycling line 16. In particular, the expander can be connected to an electric generator (not shown) to produce electric power and / or to a compressor (not shown). In some embodiments, the energy recovery unit 30 and an additional energy recovery unit 31 are connected to a compression device and / or a heating device (not shown) configured to compress and / or heat a stream of reaction compounds comprising hydrogen atoms and / or a stream of separated hydrogen molecules and / or a stream of oxidizing agent.

[0044] In some embodiments, the reaction compound is ammonia and the catalyst is based on a transition metal, preferably Ru, Ni, Co or Fe and their bimetallic, intermetallic or trimetallic compounds, supported on a material selected from the group consisting of alumina, silica, zirconia, carbon materials and mixtures thereof. In particular, the carbon material can be a material selected from the group consisting of carbon nanotubes (CNT), activated carbon, carbon black, graphite, graphene, doped carbon, typically nitrogen-doped carbon; preferably carbon nanotubes.

[0045] In some embodiments, the reaction compound is an organic compound, preferably a hydrocarbon, more preferably natural gas, still more preferably methane. In particular, when the reaction compound is methane, the catalyst can be based on: iron, nickel and their bimetallic formulations, and can be supported on alumina or carbon, preferably carbon black. Carbon black can also be used as catalyst alone, in particular in a fluidized bed reactor.

[0046] The system 10 operates as follows. The reaction compound comprising hydrogen atoms is heated in the absence of an oxidizing agent to thermally decompose the reaction compound into smaller product compounds comprising hydrogen molecules. The energy of the stream of decomposed product compounds is recovered by an expander, for example by generating electric power and / or by driving a compressor. The hydrogen molecules are separated from the other product compounds and a part of the separated hydrogen molecules is reacted with an oxidizing agent, in particular oxygen or air, to obtain heat and a stream of combustion products compounds comprising steam. The heat obtained by combustion of hydrogen is then provided to heat the reaction compound in order to obtain its thermal decomposition. In particular, the energy recovery unit 30 can be connected to a compression device and / or a heating device configured to compress and / or heat the stream of gas comprising hydrogen atoms of the reaction compound and / or the stream of separated hydrogen molecules and / or the stream of oxidizing agent.

[0047] In some embodiments, the thermal decomposition of the reaction compound is performed in the presence of a catalyst. In particular, if the reaction compound is ammonia, the heating step is operated to heat the reaction compound at a temperature higher than 400°C, preferably higher than 450°C. However, in the presence of a suitable catalyst, such temperature can be reduced to higher than 200°C. A suitable catalyst for the thermal decomposition of ammonia can be based on a transition metal, preferably Ru, Ni, Co or Fe and their bimetallic, intermetallic or trimetallic compounds, and can be supported on a material selected from the group consisting of alumina, silica, zirconia, carbon materials and mixtures thereof. In particular, the carbon material can be selected from the group consisting of carbon nanotubes (CNT), activated carbon, carbon black, graphite, graphene, doped carbon, typically nitrogen-doped carbon; preferably carbon nanotubes.

[0048] In other embodiments, the reaction compound can be an organic compound, preferably a hydrocarbon, more preferably natural gas, and even more preferably methane. Specifically, if the reaction compound is methane, the heating step is operated to heat the reaction compound at a temperature above 547°C, preferably above 760°C. However, in the presence of a suitable catalyst, such temperatures can be reduced to above 200°C. Specifically, if the reaction compound is methane, the catalyst can be based on iron, nickel, and their bimetallic formulations, and can be deposited on alumina or carbon (preferably carbon black). Carbon black can also be used alone as a catalyst, particularly in fluidized bed reactors.

[0049] In some implementations, the thermal decomposition of the reactant compound can take place at atmospheric pressure.

[0050] Continue to refer to Figure 1 , Figure 2 An embodiment of system 10 is illustrated, which is suitable for situations where hydrocarbons are used as reactants in thermal decomposition reactions. The same reference numerals have been used to indicate... Figure 1 The same or corresponding parts, elements, or components illustrated above and described herein will not be described again. System 10 according to this embodiment further includes a separation device 14, such as a cyclone separator, filter, inertial separator, or gravity settling device, downstream of expander 30, for separating hydrogen and gaseous byproducts from non-gaseous decomposition product compounds. Separation device 14 includes an outlet 142 for the gaseous stream of hydrogen and gaseous byproducts and an additional outlet 143 for non-gaseous decomposition products. In this embodiment, hydrogen recirculation line 16 is connected via line 17 to outlet 143 of separation device 14 to recirculate a portion of the hydrogen stream from separation device 14 to the first inlet 131 of the second reaction zone 13 of reactor 11. In an alternative embodiment, separation device 14 may be arranged upstream of expander 30; in some cases, this solution is preferred to prevent solid carbon from entering the expander.

[0051] In another implementation, it is also shown that... Figure 2, the system 10 additionally comprises an additional expander 31 and a condenser 18 downstream of the second reaction zone 13 of the reactor 11 for recovering energy from the stream of combustion product compounds coming from the second reaction zone and condensing the steam and separating the oxidizing agent, in particular oxygen, from the water. The condenser comprises an inlet 181 connected to the outlet of the additional expander 31, an outlet 182 of a stream of oxidizing agent, in particular oxygen, and an outlet 183 of water. The stream of oxidizing agent, in particular oxygen, is recirculated to the second reaction zone 13 of the reactor 11 through a recirculation line 20 connected at one end to the outlet 182 of the condenser 18 and at the other end to the second inlet 132 of the second reaction zone 13 of the reactor 11. Finally, the condenser 18 comprises a water extraction line 21 connected downstream of the outlet 183. In an alternative embodiment, the additional expander 31 can be arranged downstream of the condenser 18.

[0052] According to the present embodiment, thanks to the additional expander 31, it is also possible to recover energy from the stream of combustion product compounds, for example by generating electric power and / or by driving a compressor. In particular, the additional energy recovery unit 31 can be connected to a compression device and / or a heating device configured to compress and / or heat the gaseous stream of reaction compounds containing hydrogen atoms and / or the stream of separated hydrogen molecules and / or the stream of oxidizing agent.

[0053] With continued reference to Figure 1 and Figure 2 , a further embodiment of the system 10 is shown in Figure 3 . The same reference numbers indicate the same or corresponding parts, elements or components already exemplified in Figure 1 and Figure 2 and described in the above and will not be described again. The system 10 according to the present embodiment additionally comprises a gas-gas separator 22, in particular a pressure swing absorber, connected downstream of the outlet 143 of the separation device 14 through the line 17 for separating a stream of hydrogen gas and a stream of other gaseous components. In particular, the gas-gas separator 22 comprises an inlet 221 connected downstream of the outlet 143 of the separation device 14 through the line 17, a first hydrogen gas outlet 222 and a second hydrogen gas outlet 223 and an additional outlet 224 of other gaseous components. The first hydrogen gas outlet 222 is connected to a hydrogen gas extraction line 23, while the second hydrogen gas outlet 223 is connected to the second reaction zone 13 of the reactor 11 through a hydrogen gas recirculation line 16. Finally, the additional outlet 224 of other gaseous components is connected to the inlet 121 of the first reaction zone 12 of the reactor 11 through a recirculation line 24. The figure also shows a heat exchanger 25 along the line 15 for recovering heat from the stream of pyrolysis products coming from the first reaction zone 12 of the reactor 11.

[0054] While the application has been described in terms of various specific embodiments, it will be apparent to those with ordinary skill in the art that many modifications, changes and omissions can be made without departing from the spirit and scope of the application. In addition, unless otherwise indicated herein, sequences or order of any process or method steps should not be construed as critical. Accordingly, the scope of the application should be judged in terms of the claims and their full scope or equivalents, without being limited to the above described embodiments.

Claims

1. A method for producing hydrogen, the method comprising the following steps: - Heating a gas stream containing hydrogen atoms in the absence of an oxidant to thermally decompose the reaction compound into smaller product compounds containing hydrogen molecules, thereby obtaining a stream of decomposition product compounds; - Separate the stream of hydrogen molecules from the stream of other product compounds of the decomposition product compounds; - A portion of the separated hydrogen molecule stream is reacted with an oxidant, particularly an oxygen or air stream, to obtain a combustion product compound in a stream of combustion product compounds, the combustion product compound comprising vapor and heat; - The heat obtained in the previous step will be used for the step of heating the reactant compound.

2. The method of claim 1, wherein the method further comprises the following steps: -Recover energy from the stream of the decomposition product compounds and / or from the stream of the combustion product compounds.

3. The method of claim 2, wherein the step of recovering energy from the stream of the decomposition product compounds comprises expanding the stream of the decomposition product compounds to generate work.

4. The method of claim 2 or 3, wherein the step of recovering energy from the stream of combustion product compounds comprises expanding the stream of decomposition product compounds to generate work.

5. The method according to one or more of claims 2 to 4, wherein the energy recovered in the step of recovering energy from the stream of the decomposition product compounds and / or from the stream of the combustion product compounds is at least partially used to compress and heat the gas stream of the reaction compound containing hydrogen atoms and / or the stream of separated hydrogen molecules and / or the stream of the oxidant.

6. The method according to one or more of the preceding claims, wherein the step of heating a gas stream containing hydrogen atoms to thermally decompose the reaction compound in the absence of an oxidant is carried out in the presence of a catalyst.

7. The method according to one or more of claims 1 to 6, wherein the reacting compound is ammonia, and the heating step is operated to heat the reacting compound in the presence of a catalyst at a temperature above 400°C, preferably above 450°C, or at a temperature above 200°C.

8. The method according to claim 6, wherein the reactant compound is ammonia, and the catalyst is based on a transition metal, preferably Ru, Ni, Co or Fe, and their bimetallic, intermetallic or trimetallic compounds.

9. The method of claim 8, wherein the catalyst is supported on a material selected from alumina, silica, zirconium oxide, carbon materials, and mixtures thereof.

10. The method of claim 98, wherein the carbon material is selected from the group consisting of carbon nanotubes (CNTs), activated carbon, carbon black, graphite, graphene, and doped carbon, typically nitrogen-doped carbon; preferably carbon nanotubes.

11. The method according to one or more of claims 1 to 6, wherein the reacting compound is an organic compound, preferably a hydrocarbon, more preferably natural gas, and even more preferably methane.

12. The method of claim 11, wherein the reacting compound is methane, and the heating step is operated to heat the reacting compound in the presence of a catalyst at a temperature above 547°C, more preferably above 760°C, or at a temperature above 200°C.

13. The method according to claim 11 or 12, wherein the reactant compound is methane, and the catalyst is based on: iron, nickel, and bimetallic formulations thereof.

14. The method of claim 13, wherein the catalyst is deposited on alumina or carbon.

15. The method according to claim 11 or 12, wherein the reactant compound is methane and the catalyst is a carbon-based material, preferably carbon black.

16. The method according to one or more of claims 1 to 15, wherein the step of heating the gas stream containing hydrogen atoms in the absence of an oxidant is carried out at a pressure between 30 atm and 50 atm.

17. The method according to one or more of claims 1 to 15, wherein the step of heating the gas stream containing hydrogen atoms in the absence of an oxidizing agent is carried out at atmospheric pressure.

18. A system (10) for producing hydrogen from a stream of reactive compounds containing hydrogen atoms by thermal decomposition in the absence of an oxidant, wherein the system comprises: - Reactor (11), the reactor comprising two separate reaction zones, namely a first reaction zone (12) and a second reaction zone (13), the two separate reaction zones being configured to exchange heat with each other, the first reaction zone (12) comprising an inlet (121) for a stream of the reaction compounds heated to thermal decomposition and an outlet (122) for a stream of decomposition product compounds containing hydrogen, and the second reaction zone (13) comprising a first inlet (131) for a stream of hydrogen; and a second inlet (132) for a stream of oxidant, particularly oxygen or air; a burner (133) for initiating a combustion reaction of hydrogen and oxidant, particularly oxygen, the combustion reaction generating heat; and an outlet (134) for a stream of combustion product compounds containing steam, steam and oxygen, or steam and air; - A hydrogen recirculation line (16) is connected downstream of the first reaction zone (12) of the reactor (11), the hydrogen recirculation line (16) being configured to extract at least a portion of the hydrogen from the stream of the hydrogen-containing decomposition product compound from the first reaction zone (12) of the reactor (11), and to direct the at least a portion of the hydrogen from the stream of the hydrogen-containing decomposition product compound to the first inlet (131) of the second reaction zone (13) of the reactor (11).

19. The system of claim 18, further comprising: - An energy recovery unit (30), connected downstream of the outlet (122) of the first reaction zone (12) of the reactor (11), is used to recover energy from the stream of the decomposition product compounds, and / or - An additional energy recovery unit (31), connected downstream of the outlet (134) of the second reaction zone (13) of the reactor (11), is used to recover energy from the stream of combustion product compounds.

20. The system of claim 19, wherein the energy recovery unit (30) is configured to expand the flow of the decomposition product compound to generate work.

21. The system of claim 20, wherein the energy recovery unit (30) is connected to a generator and / or a compressor.

22. The system according to one or more of claims 19 to 21, wherein the additional energy recovery unit (31) is configured to expand the flow of the combustion product compound to generate work.

23. The system of claim 22, wherein the additional energy recovery unit (31) is connected to a generator and / or a compressor.

24. The system according to one or more of claims 19 to 23, wherein the energy recovery unit (30) and the additional energy recovery unit (31) are part of an energy recovery module configured to be connected at least to the outlet (122) of the first reaction zone (12) of the reactor (11) to recover energy from the stream of the decomposition product compounds, and to the outlet (134) of the second reaction zone (13) of the reactor (11) to recover energy from the stream of the combustion product compounds.

25. The system according to one or more of claims 19 to 24, wherein the energy recovery unit (30) and the additional energy recovery unit (31) are connected to a compression device and / or a heating device, the compression device and / or the heating device being configured to compress and / or heat the gas stream of the reactive compound containing hydrogen atoms and / or the stream of separated hydrogen molecules and / or the stream of the oxidant.

26. The system (10) according to one or more of claims 18 to 25, wherein the first reaction zone (12) comprises a catalyst.

27. The system (10) according to claim 26, wherein the first reaction zone (12) is configured as a fixed-bed reactor.

28. The system (10) according to claim 26, wherein the first reaction zone (12) is configured as a fluidized bed reactor.

29. The system (10) according to one or more of claims 18 to 28, wherein said system further comprises: - Separation device (14), the separation device being configured to separate hydrogen and gaseous byproducts from non-gaseous decomposition product compounds, the separation device (14) including an inlet (141) of the decomposition product compounds from the first reaction zone (12) of the reactor (11), at least one outlet (142) of the gaseous flow of hydrogen and gaseous byproducts, and an additional outlet (143) of the non-gaseous decomposition product compounds.

30. The system (10) according to claim 29, wherein the separation device (14) is arranged upstream of the energy recovery unit (30).

31. The system (10) according to claim 29, wherein the separation device (14) is arranged downstream of the energy recovery unit (30).

32. The system (10) according to one or more of claims 29 to 31, wherein the system further comprises: - Gas-gas separator (22), the gas-gas separator being connected downstream of the outlet (143) of the separation device (14) or downstream of the energy recovery unit (30), the gas-gas separator (22) being configured to separate the flow of hydrogen and the flow of other gas components, the gas-gas separator (22) including a first hydrogen outlet (222) and a second hydrogen outlet (223) and additional outlets (224) for other gas components, the first hydrogen outlet (222) being connected to a hydrogen extraction line (23), the second hydrogen outlet (223) being connected to the hydrogen recirculation line (16), and the additional outlets (224) for other gas components being connected to the inlet (121) of the first reaction zone (12) of the reactor (11).

33. The system (10) according to claim 32, wherein the gas-gas separator (22) is a pressure swing absorber.

34. The system (10) according to one or more of claims 18 to 33, wherein said system further comprises: - A condenser (18) connected downstream of the outlet (134) of the second reaction zone (13) of the reactor (11), the condenser (18) being configured to condense steam and separate the oxidant, particularly oxygen, from water, the condenser (18) including an inlet (181) for combustion product compounds containing steam, or steam and oxidant, particularly air, or steam and oxygen from the second reaction zone (13) of the reactor (11); an outlet (182) for the flow of oxidant, particularly oxygen; and an outlet (183) for water. -Oxidant recirculation line (20), particularly an oxygen recirculation line connected downstream of the outlet (182) of the condenser (18), the oxidant recirculation line (20) being configured to direct the flow of the oxidant from the outlet (182) to the second inlet (132) of the second reaction zone (13) of the reactor (11). - A water extraction line (21) is connected downstream of the outlet (183) of the condenser (18).

35. The system (10) according to claim 34, wherein the condenser (18) is arranged upstream of the additional energy recovery unit (31).

36. The system (10) according to claim 34, wherein the condenser (18) is arranged downstream of the additional energy recovery unit (31).

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