A process and a system of carbon oxides-free hydrogen production

Abstract

The disclosure concerns a process of carbon oxides-free hydrogen production is disclosed. The process comprises the following steps: - heating a gas stream of a reacting compound including hydrogen atoms in absence of oxidizing agents, to thermally decompose the reacting compound into smaller product compounds, including hydrogen molecules, obtaining a stream of decomposition product compounds; - separating hydrogen molecules from other product compounds of the stream of decomposition product compounds; - reacting a portion of the stream of separated hydrogen molecules with a stream of an oxidizing agent, in particular oxygen or air, to obtain combustion product compounds, including steam and heat, in a stream of combustion product compounds; - providing heat obtained in the previous step to the step of heating the reacting compound; and wherein the process can comprise a step of - recovering energy from the stream of decomposition product compounds and / or from the stream of combustion product compounds. Additionally, a system of hydrogen production is also disclosed, the system being configured to operate according to the above process.

Description

A Process and a System of Carbon Oxides-free Hydrogen ProductionDescriptionTECHNICAL FIELD

[0001] The present disclosure concerns hydrogen production on an industrial scale. Embodiments disclosed herein specifically concern a process and a system of production of hydrogen that does not imply any production of carbon oxides as a by-product. Additionally, the disclosure concerns a process and a system of production of hydrogen that comprises recovering energy generated by the chemical reactions involved, to additionally lower the production of carbon oxides by auxiliary processes and devices while reducing the demand of external energy sources.BACKGROUND ART

[0002] Hydrogen is emerging as a new energy vector and a 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 automobiles, energy carriers, and integrated heating and electrical power generation systems.

[0003] However, hydrogen production techniques present technological challenges, including feedstock type, conversion efficiency, carbon emissions, energy intensity of the production processes and the need for the safe integration of H2 production systems with H2 purification and storage technologies.

[0004] Hydrogen production may 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). The majority of hydrogen is currently produced via the CO2- intensive steam methane reforming process. Electrolysis is a typical method that uses an electrical current to separate water into oxygen and hydrogen and creates green hydrogen without any direct emissions of carbon dioxide. Renewable energy sources may be used to produce the necessary electricity. The expense of producing hydrogen, particularly for green hydrogen, is a significant hurdle. The cost of manufacturing hydrogen using steam reforming is around three times greater than the cost of producing one unitof energy using natural gas. Hydrogen will cost almost twice as much to produce using electrolysis with 5 cents / kWh of energy compared to hydrogen produced using natural gas. Lower hydrogen concentrations may be transported via the existing natural gas pipeline infrastructure, which will also assist in reducing CO2 emissions from the existing natural gas reforming plants.

[0005] Both approaches negatively affect the operation costs of the system and may have an adverse environmental impact.

[0006] Thermal decomposition of methane or ammonia in absence of oxygen, or more in general, in absence of oxidants or oxidizing agents, appears to be a potential candidate for H2 production. However, thermal decomposition is an energy intensive process, and the current technologies still involves direct and indirect CO2 emissions.

[0007] Accordingly, an improved system and method for hydrogen production through of the thermal decomposition of methane or ammonia to H2 in absence of oxidizing agents, in particular in absence of oxygen, which is highly selective towards H2 and free of CO2 emissions would be beneficial and would be welcomed in the technology.

[0008] Preferably, the system and method for hydrogen production according to the present disclosure allow for recovering energy generated by the chemical reactions involved, to additionally lower the production of carbon oxides by auxiliary processes and devices while reducing the demand of external energy sources.SUMMARY

[0009] In one aspect, the subject matter disclosed herein is directed to an efficient carbon oxides-free process for continuous H2 generation from a reacting compound or a mixture of reacting compounds, the reacting compounds including hydrogen atoms, without promoting side reactions. In particular, the reacting compound can be chosen amongst ammonia or fossil fuels.

[0010] In particular, the hydrogen generation process includes thermal decomposition of the reacting compound or compounds in an oxidizing agents free environment, to obtain hydrogen and other product compounds that smaller than the reacting compounds. Hydrogen is subsequently separated from the other product compounds and apart of the separated hydrogen is reacted with an oxidizing agent, 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 pressure of the products of the above reactions. The thermal decomposition reaction can be conducted in the presence of a catalyst.

[0011] In another aspect, the reacting compound can be ammonia and the heating step is operated to heat the reacting compound at a temperature above 400°C, preferably above 450°C, or in the presence of a catalyst at a temperature above 200°C, and the catalyst is based on transition metals, preferably: Ru, Ni, Co or Fe and bimetallic, intermetallic or trimetallic compounds thereof; supported on a material chosen among: alumina, silica, zirconia and, carbon materials and mixture thereof. Alternatively, the catalyst can be supported on a material chosen among: carbon nanotubes (CNT), activated carbon, carbon black, graphite, graphene, doped carbon, normally nitrogen doped carbon; preferably carbon nanotubes.

[0012] In one aspect, the reacting compound can be an organic compound, preferably a hydrocarbon, more preferably natural gas, still more preferably methane. If the reacting compound is methane, then the heating step is operated to heat the reacting compound at a temperature above 547°C, preferably above 760°C, or in the presence of a catalyst at a temperature above 200°C and the catalyst can be based on: iron, nickel and bimetallic formulations thereof, deposited on alumina or carbon. In particular, when the reacting compound is methane, then the catalyst is a carbon-based material, preferably carbon black.

[0013] In another aspect, the subject matter disclosed herein concerns a system of hydrogen production from thermal decomposition in absence of oxidizing agents of a reacting compound including hydrogen atoms, the system comprising a reactor comprising two separate reaction zones: a thermal decomposition zone for the cracking of the reacting compounds to H2 and a zone for heat generation through hydrogen combustion with an oxidizing agent, in particular oxygen or air. The heat for the thermal decomposition reaction is generated by the combustion of a part of the hydrogen produced in the thermal decomposition zone. The combustion reaction releases steam and reaches a high combustion efficiency.

[0014] A further aspect of the present disclosure is drawn to a system of hydrogen production from thermal decomposition of a reacting compound including hydrogen atoms in absence of oxidizing agents, to obtain smaller product compounds, including hydrogen molecules, wherein the system also comprises an energy recovery unit, downstream of the thermal decomposition reaction zone, to recover energy from the stream of decomposition product compounds, and / or downstream of the combustion reaction zone, to recover energy from the stream of combustion product compounds, and separating means, downstream of the energy recovery unit or the thermal decomposition reaction zone, to separate hydrogen and gas by-products from non-gaseous product compounds, the hydrogen recirculation line being configured to withdraw at least a portion of the stream of hydrogen from the separating means and direct it to the combustion zone of the reactor.

[0015] According to one embodiment, the system can comprise an additional energy recovery unit connected downstream of the zone for heat generation through hydrogen combustion, to recover energy from the stream of combustion product compounds.

[0016] According to another embodiment, the energy recovery unit and the additional energy recovery unit can be part of an energy recovery module, configured to connect at least downstream of the thermal decomposition reaction zone, to recover energy from the stream of decomposition product compounds and downstream of the zone for heat generation through hydrogen combustion, to recover energy from the stream of combustion product compounds.

[0017] According to another embodiment, the system can comprise a gas-gas separator connected downstream of the separating means to separate a stream of hydrogen and a stream of other gas components.BRIEF DESCRIPTION OF THE DRAWINGS

[0018] A more complete appreciation of the disclosed embodiments of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:- Fig. 1 illustrates a schematic of a system of hydrogen production through thermal decomposition in absence of oxidizing agents of a reacting compound or amixture of reacting compounds including hydrogen atoms and recirculation of part of the produced hydrogen 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;- Fig.2 illustrates a schematic of a system of hydrogen production through thermal decomposition in absence of oxidizing agents, according to a second embodiment; and- Fig.3 illustrates a schematic of a system of hydrogen production through thermal decomposition in absence of oxidizing agents, according to a third embodiment.DETAILED DESCRIPTION OF EMBODIMENTS

[0019] According to one aspect, the present subject matter is directed to systems and methods for the production of hydrogen through the processes comprising the following steps:- heating a gas stream of a reacting compound including hydrogen atoms in absence of oxidizing agents, to thermally decompose the reacting compound into smaller product compounds, including hydrogen molecules, obtaining a stream of decomposition product compounds;- separating a stream of hydrogen molecules from other product compounds of the stream of decomposition product compounds;- reacting a portion of the stream of separated hydrogen molecules with a stream of an oxidizing agent, in particular oxygen or air, to obtain steam and heat, in a stream of combustion product compounds; and- providing heat obtained in the previous step to the step of heating the reacting compound.In particular, according to the present disclosure, the process can also comprise a step of- recovering energy from the stream of decomposition product compounds and / or from the stream of combustion product compounds.

[0020] According to another aspect, the step of recovering energy from the stream of decomposition product compounds can comprise expanding the stream of decomposition product compounds to produce work.

[0021] According to still 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.

[0022] 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 gas stream of a reacting compound including hydrogen atoms and / or the stream of separated hydrogen molecules and / or the stream of oxidizing agent.

[0023] According to another aspect, said step of heating a reacting compound including hydrogen atoms in absence of oxidizing agents, to thermally decompose the reacting compound, can be conducted in the presence of a catalyst, which can be provided as a fixed bed or as a fluidized bed. In particular, when the reacting compound is ammonia, the catalyst can be based on transition metals, preferably: Ru, Ni, Co or Fe and bimetallic, intermetallic or trimetallic compounds thereof and the catalyst can be supported on a material chosen among: alumina, silica, zirconia and, carbon materials and mixture thereof, in particular carbon nanotubes (CNT), activated carbon, carbon black, graphite, graphene, doped carbon, normally nitrogen doped carbon; preferably the catalyst is based on carbon nanotubes. When the reacting compound is an organic compound, it is most preferably natural gas or methane, the catalyst can be based on: iron, nickel and bimetallic formulations thereof, which can be deposited on alumina or carbon, preferably carbon black. Carbon black can also be used alone as a catalyst, in particular in fluidized bed reactors.

[0024] According to another aspect, the present subject matter is directed to a system of hydrogen production from thermal decomposition of a reacting compound including hydrogen atoms in absence of oxidizing agents, to obtain smaller product compounds, including hydrogen molecules, wherein the system comprises:- 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 the reacting compound and an outlet of a stream of decomposition product compounds, including hydrogen, and the second reaction zone comprising a first inlet of a stream of hydrogen and a second inlet of a stream of an oxidizing agent, in particular oxygen or air, a burner and an outlet of a stream of combustionproduct compounds, including steam, steam and oxygen or steam and air;and- a hydrogen recirculation line downstream of the first reaction zone of the reactor, to recirculate at least a portion of the hydrogen of the stream of decomposition product compounds from the first reaction zone of the reactor to the second reaction zone of the reactor, wherein it reacts with an oxidizing agent, in particular oxygen or air.

[0025] According to one aspect, the system can additionally comprise an energy recovery unit connected downstream of the first reaction zone of the reactor, to recover 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, to recover energy from the stream of combustion product compounds; and / or separating means to separate a gas stream including hydrogen and gas by-products from non- gaseous product compounds of the stream of decomposition product compounds from the first reaction zone of the reactor.

[0026] According to another aspect, the system can additionally comprise a condenser, downstream of the second reaction zone of the reactor or downstream of the additional energy recovery unit, to condensate steam of the stream of combustion product compounds and separate oxygen from water. In particular, an oxidizing agent recirculation line, in particular an oxygen recirculation line is present, to recirculate oxygen to the second reaction zone of the reactor.

[0027] According to still another aspect, the system can additionally comprise a gasgas separator downstream of the outlet of the separating means, to separate a stream of hydrogen and a stream of other gas components of the gas stream from the separating means. In particular, the gas-gas separator can be a pressure swing absorber.

[0028] It will be evident to those skilled in the art that the process and the system of the present disclosure allow for a carbon-free hydrogen production, compared to the solutions of the prior art such as natural gas combustion-assisted pyrolysis reactors, plasma reactors, and electrically-heated reactors. Additionally, it will be evident that the possibility of recovering energy generated by the chemical reactions involved allows to additionally lower the production of carbon oxides by auxiliary processes anddevices while reducing the demand of external energy sources. The reactor of the present disclosure can be equipped with tube bundles to convey the H2 combustion products (steam) and heat up the thermal decomposition reaction zone. Therefore, any direct contact between steam and the compound to be thermally decomposed is avoided, thus suppressing side reactions and resulting in a maximization of H2 selectivity. Additionally, the reactor of the present disclosure can be filled with solid catalyst to improve the reaction rate and to reach a higher yield and / or to operate at a lower temperature. Moreover, by separating the thermal decomposition reaction zone from the combustion reaction zone, the system of the present disclosure can work at a pressure comprised between 1 and 100 atm, preferably between 30 and 50 atm, but also allows operating the reaction at atmospheric pressure.

[0029] Reference now will be made in detail to embodiments of the disclosure, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the disclosure, not limitation of the disclosure. 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. Reference throughout the specification to "one embodiment" or "an embodiment" or “some embodiments” means that the particular feature, structure or characteristic described in connection with an embodiment is included in at least one embodiment of the subject matter disclosed. Thus, the appearance of the phrase "in one embodiment" or "in an embodiment" or "in some embodiments" in various places throughout the specification is not necessarily referring to the same embodiment(s). Further, the particular features, structures or characteristics may be combined in any suitable manner in one or more embodiments.

[0030] 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 may be additional elements other than the listed elements.

[0031] Referring now to the drawings, Fig.1 shows a schematic of an exemplary system 10 of hydrogen production through thermal decomposition in absence of oxidizing agents of a reacting compound or a mixture of reacting compounds including hydrogen atoms and recirculation of part of the produced hydrogen to react with an oxidizingagent, in particular oxygen and / or air to produce heat to be provided to the thermal decomposition reaction, according to a first embodiment. In particular, the system 10 includes a reactor 11 composed of a first reaction zone 12, inside which a reacting compound or a mixture of reacting compounds including hydrogen atoms is thermally decomposed into smaller product compounds, including hydrogen molecules, and a second reaction zone 13, wherein hydrogen is reacted with an oxidizing agent, in particular oxygen or air to obtain combustion product compounds, including steam or steam and air or steam and an oxidizing agent, in particular oxygen. The two reaction zones 12, 13 are configured to exchange heat between each other, the first reaction zone 12 comprising an inlet 121 of a stream of the reacting compound and an outlet 122 of a stream of product compounds including hydrogen and the second reaction zone 13 comprising a first inlet 131 of a stream of hydrogen and a second inlet 132 of a stream of an 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, hydrogen fed to the second reaction zone 13 of the reactor 11 through the first inlet 131 is recirculated from a portion of the hydrogen obtained by thermal decomposition in the first reaction zone 12 of the reactor 11. To this aim, a hydrogen recirculation line 16 is connected downstream of the outlet 122 of the first reaction zone 12 of the reactor 11, to withdraw part of the hydrogen of the stream of decomposition product compounds from the first reaction zone 12 of the reactor 11 and direct it 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 as a fluidized bed reactor. In order to recover energy from the high temperature and pressure of the products of the stream of decomposition product compounds from the first reaction zone 12 of the reactor 1 1 , 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 recirculation line 16. In particular, the expander can be connected to an electrical power generator (not shown) to produce electrical power and / or to a compressor (not shown). In some embodiments, the energy recovery unit 30 and the additional energy recovery unit 31 are connected to compressing means and / or heating means (not shown) configured to compress and / or heat the gas stream of reacting compound including hydrogen atoms and / or the stream of separated hydrogen molecules and / or the stream of oxidizing agent.

[0032] In some embodiments, the reacting compound is ammonia and the catalyst isbased on transition metals, preferably Ru, Ni, Co or Fe and bimetallic, intermetallic or trimetallic compounds thereof, supported on a material chosen among: alumina, silica, zirconia, carbon materials and mixture thereof. In particular, the carbon material can be a material chosen among: carbon nanotubes (CNT), activated carbon, carbon black, graphite, graphene, doped carbon, normally nitrogen doped carbon; preferably carbon nanotubes.

[0033] In some embodiments, the reacting compound is an organic compound, preferably a hydrocarbon, more preferably natural gas, still more preferably methane. In particular, when the reacting compound is methane, the catalyst can be based on: iron, nickel and bimetallic formulations thereof, and can be supported on alumina or carbon, preferably carbon black. Carbon black can also be used alone as a catalyst, in particular in fluidized bed reactors.

[0034] The system 10 operates as follows. A reacting compound including hydrogen atoms is heated in absence of oxidizing agents, to thermally decompose the reacting compound into smaller product compounds, including hydrogen molecules. The energy of the stream of decomposition product compounds is recovered by the expander, for example by producing electrical power and / or by driving a compressor. The hydrogen molecules are separated from other product compounds and a portion of the separated hydrogen molecules is reacted with an oxidizing agent, in particular oxygen or air, to obtain heat and a stream of combustion product compounds, comprising steam. Heat obtained by the combustion of hydrogen is then provided to heat the reacting compound, in order to obtain its thermal decomposition. In particular, the energy recovery unit 30 can be connected to compressing means and / or heating means configured to compress and / or heat the gas stream of reacting compound including hydrogen atoms and / or the stream of separated hydrogen molecules and / or the stream of oxidizing agent.

[0035] In some embodiments, thermal decomposition of the reacting compound is operated in the presence of a catalyst. In particular, if the reacting compound is ammonia, then the heating step is operated to heat the reacting compound at a temperature above 400°C, preferably above 450°C. However, in presence of a suitable catalyst, such temperature can be lowered to above 200°C. suitable catalyst for the thermal decomposition of ammonia can be based on transition metals, preferably Ru, Ni, Co orFe and bimetallic, intermetallic or trimetallic compounds thereof, and can be supported on a material chosen among: alumina, silica, zirconia, carbon materials and mixture thereof. In particular, the carbon material can be chosen among: carbon nanotubes (CNT), activated carbon, carbon black, graphite, graphene, doped carbon, normally nitrogen doped carbon; preferably carbon nanotubes.

[0036] In other embodiments, the reacting compound can be an organic compound, preferably a hydrocarbon, more preferably natural gas, still more preferably methane. In particular, if the reacting compound is methane, then the heating step is operated to heat the reacting compound at a temperature above 547°C, preferably above 760°C. However, in presence of a suitable catalyst, such temperature can be lowered to above 200°C. In particular, if the reacting compound is methane then the catalyst can be based on: iron, nickel and bimetallic formulations thereof and can be deposited on alumina or carbon, preferably carbon black. Carbon black can also be used alone as a catalyst, in particular in fluidized bed reactors.

[0037] In some embodiments, the thermal decomposition of the reacting compound can be conducted at atmospheric pressure.

[0038] With continuing reference to Fig.l, Fig.2 illustrates an embodiment of the system 10 that is suitable in case hydrocarbons are used as reacting compounds in the thermal decomposition reaction. The same reference numbers designate the same or corresponding parts, elements or components already illustrated in Fig. 1 and described above, and which will not be described again. The system 10 according to this embodiment additionally comprises separating means 14, such as a cyclones, filters, inertial separators, gravity settlers, downstream of the expander 30, to separate hydrogen and gas by-products from non- gaseous decomposition product compounds. The separating means 14 include one outlet 142 of a gas stream of hydrogen and gaseous by-products and an additional outlet 143 of non-gaseous decomposition products. In this embodiment, the hydrogenrecirculation line 16 is connected to the outlet 143 of the separating means 14 through a line 17, to recirculate a portion of the stream of hydrogen from the separating means 14 to the first inlet 131 of the second reaction zone 13 of the reactor 11. In an alternative embodiment, the separating means 14 can be arranged upstream of the expander 30, this solution being preferred in some cases, to avoid solid carbon to enter the expander.

[0039] In another embodiment, also shown in Fig.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 to recover energy from the stream of combustion product compounds from the second reaction zone and to condensate steam and separate an oxidizing agent, in particular oxygen from water. The condenser includes an inlet 181 that is connected to the outlet of the additional expander 31 , an outlet 182 of a stream of an 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, which is 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 includes a water withdrawal line 21 connected downstream of the outlet 183. In an alternative embodiment, the additional expander 31 can be arranged downstream of the condenser 18.

[0040] According to this embodiment, also the energy of the stream of combustion product compounds can be recovered, thanks to the additional expander 31 , for example by producing electrical power and / or by driving a compressor. In particular, the additional energy recovery unit 31 can be connected to compressing means and / or heating means configured to compress and / or heat the gas stream of reacting compound including hydrogen atoms and / or the stream of separated hydrogen molecules and / or the stream of oxidizing agent.

[0041] With continuing reference to Figs 1 and 2, a further embodiment of a system 10 is shown in Fig.3. The same reference numbers designate the same or corresponding parts, elements or components already illustrated in Fig.l and Fig.2 and described above, and which will not be described again. The system 10 according to this embodiment additionally comprises a gas-gas separator 22, in particular a pressure swing absorber, which is connected downstream of the outlet 143 of the separating means 14 through a line 17, to separate a stream of hydrogen and a stream of other gas components. In particular, the gas-gas separator 22 comprises an inlet 221 connected downstream of the outlet 143 of the separating means 14 through the line 17, a first hydrogen outlet 222 and a second hydrogen outlet 223 and an additional outlet 224 of other gas components. The first hydrogen outlet 222 is connected to a hydrogen withdrawal line 23, whereas the second hydrogen outlet 223 is connected to the second reaction zone 13 of the reactor 11 through the hydrogen recirculation line 16. Finally, the additionaloutlet 224 of other gas components is connected to the inlet 121 of the first reaction zone 12 of the reactor 11 through the recirculation line 24. The figure also shows a heat exchanger 25, along the line 15, for heat recovery from the pyrolysis product stream from the first reaction zone 12 of the reactor 11.

[0042] While the invention has been described in terms of various specific embodiments, it will be apparent to those of ordinary skill in the art that many modifications, changes, and omissions are possible without departing form the spirt and scope of the claims. In addition, unless specified otherwise herein, the order or sequence of any process or method steps may be varied or re-sequenced according to alternative em- bodiments.

Claims

A Process and a System of Carbon Oxides-free Hydrogen ProductionCLAIMS1. A process of hydrogen production, the process comprising the following steps:- heating a gas stream of a reacting compound including hydrogen atoms in absence of oxidizing agents, to thermally decompose the reacting compound into smaller product compounds, including hydrogen molecules, obtaining a stream of decomposition product compounds;- separating a stream of hydrogen molecules from other product compounds of the stream of decomposition product compounds;- reacting a portion of the stream of separated hydrogen molecules with a stream of an oxidizing agent, in particular oxygen or air, to obtain combustion product compounds, including steam and heat, in a stream of combustion product compounds;- providing heat obtained in the previous step to the step of heating the reacting compound.

2. The process of claim 1, wherein the process additionally comprises a step of- recovering energy from the stream of decomposition product compounds and / or from the stream of combustion product compounds.

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

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

5. The process of one or more of claims 2-4, wherein 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 is used at leastpartially to compress and heat the gas stream of a reacting compound including hydrogen atoms and / or the stream of separated hydrogen molecules and / or the stream of oxidizing agent.

6. The process of one or more of the preceding claims, wherein said step of heating a gas stream of a reacting compound including hydrogen atoms in absence of oxidizing agents, to thermally decompose the reacting compound is conducted in the presence of a catalyst.

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

8. The process of claim 6, wherein the reacting compound is ammonia and the catalyst is based on transition metals, preferably Ru, Ni, Co or Fe and bimetallic, intermetallic or trimetallic compounds thereof.

9. The process of claim 8, wherein the catalyst is supported on a material chosen among: alumina, silica, zirconia, carbon materials and mixture thereof.

10. The process of claim 98, wherein the carbon material is a material chosen among: carbon nanotubes (CNT), activated carbon, carbon black, graphite, graphene, doped carbon, normally nitrogen doped carbon; preferably carbon nanotubes.

11. The process of one or more of claims 1 -6, wherein the reacting compound is an organic compound, preferably a hydrocarbon, more preferably natural gas, still more preferably methane.

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

13. The process of claim 11 or 12, wherein the reacting compound is methane and the catalyst is based on: iron, nickel and bimetallic formulations thereof.

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

15. The process of claim 11 or 12, wherein the reacting compound is methane and the catalyst is a carbon-based material, preferably carbon black.

16. The process of one or more of claims 1-15, wherein said step of heating a gas stream of a reacting compound including hydrogen atoms in absence of oxidizing agents, is conducted at a pressure comprised between 30 and 50 atm.

17. The process of one or more of claims 1-15, wherein said step of heating a gas stream of a reacting compound including hydrogen atoms in absence of oxidizing agents is conducted at atmospheric pressure.

18. A system (10) of hydrogen production from thermal decomposition of a stream of reacting compounds including hydrogen atoms in absence of oxidizing agents, to obtain smaller product compounds, including hydrogen molecules, wherein the system comprises:- a reactor (11) comprising two separate reaction zones, namely a first reaction zone (12) and a second reaction zone (13), configured to exchange heat between each other, the first reaction zone (12) comprising an inlet (121) of a stream of the reacting compounds, which is heated to thermally decompose, and an outlet (122) of a stream of decomposition product compounds including hydrogen and the second reaction zone (13) comprising a first inlet (131) of a stream of hydrogen and a second inlet (132) of a stream of an oxidizing agent, in particular oxygen or air, a burner (133), to start a combustion reaction of hydrogen and an oxidizing agent, in particular oxygen, the combustion reaction developing heat, and an outlet (134) of a stream of combustion product compounds, including steam, steam and oxygen or steam and air;- a hydrogen recirculation line (16) connected downstream of the first reaction zone (12) of the reactor (11), the hydrogen recirculation line (16) being configured to withdraw at least a portion of the hydrogen of the stream of decomposition product compounds including hydrogen from the first reaction zone (12) of the reactor (11) and direct it 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), to recover energy from the stream of 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), 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 stream of decomposition product compounds to produce work.

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

22. The system of one or more of claims 19-21, wherein the additional energy recovery unit (31) is configured to expand the stream of combustion product compounds to produce work.

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

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

25. The system of one or more of claims 19-24, wherein the energy recovery unit (30) and the additional energy recovery unit (31) are connected to compressing means and / or heating means configured to compress and / or heat the gas stream of reacting compound including hydrogen atoms and / or the stream of separated hydrogen molecules and / or the stream of oxidizing agent.

26. The system (10) of one or more of claimsl8-25, wherein the first reaction zone (12) comprises a catalyst.

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

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

29. The system (10) of one or more of claims 18-28, wherein the system additionally comprises:- separating means ( 14), configured to separate hydrogen and gas by-products from non-gaseous decomposition product compounds, the separating means (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 a gas stream of hydrogen and gaseous by-products and an additional outlet (143) of non-gaseous decomposition product compounds.

30. The system (10) of claim 29, wherein the separating means (14) are arranged upstream of the energy recovery unit (30).

31. The system (10) of claim 29, wherein the separating means (14) are arranged downstream of the energy recovery unit (30).

32. The system (10) of one or more of claims 29-31, the system additionally comprising:- a gas-gas separator (22) connected downstream of the outlet (143) of the separating means (14) or downstream of the energy recovery unit (30), the gas-gas separator (22) being configured to separate a stream of hydrogen and a stream of other gas components, the gas-gas separator (22) comprising a first hydrogen outlet (222) and a second hydrogen outlet (223) and an additional outlet (224) of other gas components, the first hydrogen outlet (222) being connected to a hydrogen withdrawal line (23), the second hydrogen outlet (223) being connected to the hydrogen recirculation line (16) and the additional outlet (224) of other gas components being connected to the inlet (121) of the first reaction zone (12) of the reactor (11).

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

34. The system (10) of one or more of claims 18-33, wherein the systemadditionally 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 condensate steam and separate an oxidizing agent, in particular oxygen from water, the condenser (18) including an inlet (181) of combustion product compounds, including steam or steam and an oxidizing agent, in particular air or steam and oxygen from the second reaction zone (13) of the reactor (11), an outlet (182) of a stream of an oxidizing agent, in particular a stream of oxygen and an outlet (183) of water;- an oxidizing agent recirculation line (20), in particular an oxygen recirculation line connected downstream of the outlet (182) of the condenser (18), the oxidizing agent recirculation line (20) being configured to direct the stream of oxidizing agent from the outlet (182) to the second inlet (132) of the second reaction zone (13) of the reactor (11);- a water withdrawal line (21) connected downstream of the outlet (183) of the condenser (18).

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

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

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