FR2888835A1 - Procedure for producing hydrogen from hydrocarbon and oxidant products uses electrical discharge to produce a non-thermic plasma in a spiral reagent flow - Google Patents

Abstract

The procedure consists of creating a reaction in a cylindrical chamber (100) between hydrocarbon and oxidant products in a spiral flow, using an electrical discharge to produce a non-thermic plasma, the discharge being selected so that the plasma is moved by the products to occupy the major part of the chamber. The discharge is produced by a high-tension generator fed by a low-tension current source and comprises a single or double resonance converter. The spiral flow of the products is created by a tangential injection of at least one of the reagents through one or more injectors that are preferably spaced at even intervals round the axis of the chamber, and possibly in groups. The reagents are introduced in the form of gases, either separately or pre-mixed.

Description

PROCESS FOR PRODUCING HYDROGEN FROM HYDROCARBONS OR COMPOUNDS

HYDROCARBON

  The present invention relates to a method and apparatus or system for producing hydrogen from hydrocarbons or hydrocarbon compounds.

  It is envisaged to use hydrogen in particular for the supply of PEM fuel cells (Proton Exchange Membrane), which play an increasingly important role for both stationary and mobile applications.

  There are currently various processes for producing hydrogen. The best known and most used is the catalytic reforming of hydrocarbons. This process consists of converting a hydrocarbon into a gas containing predominantly hydrogen and carbon monoxide, this transformation being carried out by partial oxidation, steam reforming or autothermal reforming.

  Partial oxidation is an exothermic operation that involves reacting a hydrocarbon with air or pure oxygen. The steam reforming is an endothermic reaction, that is to say which requires a supply of energy externally. Autothermal reforming consists of a combination of the two previous reactions corresponding to autothermal conditions.

  Although widely used, catalytic reforming has many disadvantages. In particular, if this process is perfectly controlled on an industrial scale for large capacity installations, the transition to reduced scales poses significant problems in terms in particular of compactness, response time or poisoning of the catalysts. This is why processes using plasma technologies have recently been proposed. Among these new processes we can distinguish two categories: processes based on the use of thermal plasmas, where plasma acts essentially as a source of energy, and those based on the use of non-thermal plasmas, where plasma acts. essentially as a catalyst.

  The methods based on the use of thermal plasmas have major disadvantages, in particular a high electrical energy consumption and erosion of the electrodes used to generate the plasma which leads to lifetimes limited to a few hundred hours.

  The present invention relates to a method using non-thermal plasmas.

  It is known from US Pat. No. 6,322,757 B1 to use a method in which an electric discharge is produced between two electrodes and then the reagents are introduced between these two electrodes with a high speed. The plasma thus created serves as a catalyst for accelerating the reaction. For the supply of electrical energy for generating the plasma, this prior document provides for the use of a direct current source which allows the control of the current in a zone of very high voltage and low intensity of the current; but the description of this patent provides no solution for carrying out this control of the direct current.

  Studies conducted in the context of the present invention have shown that if one uses a known plasma power supply based on a high voltage transformer connected to an impedance fed either by direct current or alternating current, it necessarily occurs a non-stationary glidarc operation, where the voltage and current vary very strongly over time, with a frequency depending on the flow conditions. These strong variations have the effect of creating an inhomogeneous and confined plasma, and therefore a reaction that has a non-optimized performance.

  Moreover this type of power supply is necessarily characterized by very poor performance.

  The invention aims to remedy these drawbacks. The invention relates to a process for producing hydrogen from a hydrocarbon product and an oxidizing product, the reaction being carried out in an enclosure in which the products circulate and in which an electrical discharge is produced producing a non-thermal plasma (also called cold plasma or plasma out of equilibrium thermodynamic), the electric discharge being selected so that the plasma is such that it is driven by the products to occupy most of the enclosure.

  The circulation of the reactive products makes it possible, when passing in front of the electric arc, to drive the discharge throughout the enclosure.

  In one embodiment, the discharge is stable and occupies the entire length of the enclosure.

  In one embodiment, the electric discharge is produced by a DC electric generator, which includes a resonance-type AC DC converter. A resonance converter, an example of which will be described later, makes it possible to regulate the current precisely. Moreover, it makes it possible to maintain the intensity of the current at a constant and stable value. This allows a dynamic control of the plasma by varying the current very precisely, and one can thus obtain particularly favorable reactive conditions for the conversion of the reagents into hydrogen-rich gas.

  In a variant, the generator produces a constant direct current.

  In one embodiment, the intensity of the current used to supply the plasma has a value of less than 1 ampere. The resonance converter guarantees stability and the ability to adjust the current even for low intensity values, typically less than 1 ampere. Since the voltage level is defined by the geometry of the system and the flow conditions, and generally having a high value, it is important to be able to control the current even for low intensity values in order to make the best use of the process. all the conditions.

  In one embodiment, the resonance converter used in the electrical generator is single or double resonance, preferably double resonance. The use of a double resonance converter makes it possible to generate either a high electrical power or a quasi-zero power, depending on the frequency conditions used. An example of such a converter will be described later.

  According to one embodiment, the electric generator is powered by a DC low voltage source, and it comprises three elements: the resonant type AC voltage DC voltage converter, a voltage booster and a high voltage DC voltage converter. . The voltage booster, or transformer, increases the voltage to obtain relatively high values (of the order of several kV) whose level is a function of the geometry and dimensions of the enclosure, as well as the conditions reactive. The AC / DC converter is used to rectify the high voltage obtained at the output of the transformer.

  In one embodiment, the enclosure has a cylindrical symmetry around an axis, and a helical flow of reagents is created, this flow being effected along this axis. This helical flow makes it possible to obtain a homogeneous plasma throughout the enclosure, and therefore a high conversion efficiency.

  It should be noted that this helical flow can be used independently of the generator using a resonance converter, for example with a conventional generator such as those used in existing devices.

  According to one embodiment, to create this helical flow, the reactants are injected substantially tangentially in the chamber by injectors distributed in at least one section of the enclosure.

  The injectors can be equidistributed around the axis of the enclosure and their number is preferably between 2 and 6. The uniform distribution of the injectors makes it possible to increase the homogeneity of the plasma created and therefore to further increase the efficiency.

  According to one embodiment, several groups of injectors are provided. One group is located on a different section than the one on which another group is located. This arrangement makes it possible to distribute the injection in several sections located downstream of the first, and thus to maintain or even reinforce the flow over the entire length of the enclosure.

  According to one embodiment, the reactants are introduced in gaseous form into the chamber. The reagents are injected either separately or pre-mixed.

  In one embodiment, the chamber is provided with a post-reactive zone maintained at high temperature.

  This zone is used especially in the case of operation with large amounts of water, in order to maintain the reagents at a temperature sufficient for the chemical reaction to be complete.

  This post-reactive zone may, in addition, comprise a catalyst.

  According to one embodiment, the hydrocarbon product is included in the group comprising: pure hydrocarbons, automotive fuels, fuels used for aerial and marine propulsion, alcohols, ethers and esters.

  According to one embodiment, the oxidizing product is included in the group comprising: air, water, oxygen enriched air and water / air mixtures (enriched with oxygen or not).

  According to one embodiment the reaction chamber is maintained at a pressure of between 1 and 20 bar.

  According to one embodiment, the current generator is connected to two concentric electrodes: one axial and the other in the form of a cylindrical tube of the same axis.

  The tubular electrode comprises a membrane permeable to hydrogen. This membrane makes it possible in particular to modify the hydrogen pressure in the chamber and thus to shift the thermodynamic equilibrium and to increase the conversion to hydrogen.

  In one embodiment, a dielectric thin film is deposited on the inner surface of the tubular electrode. This layer allows a better distribution of electric charges at the surface, and thus a greater homogeneity of the discharge.

  In one embodiment, the tubular electrode comprises a catalyst. It is for example made of a nickel-based alloy.

  The catalyst makes it possible to accelerate the chemical reactions in contact with the electrode.

Detailed description:

  Other characteristics and advantages of the invention will be better understood by means of the description of certain embodiments, described in non-limiting manner and illustrated with the aid of the drawings in which: FIG. 1 is a section axial view of a device according to the invention, - Figure la shows a similar device to that of Figure 1, wherein the interior of the enclosure is covered with a thin dielectric layer, - Figure 2 is a radial section view of the device shown in FIG. 1; FIG. 3 is a view similar to that of FIG. 1 in which the device is provided with a heat exchanger according to the invention; FIG. After the post-reactive reaction is added to the device shown in FIGS. 1 and 2, FIG. 4a shows a device similar to that of FIG. 4, in which the post-reactive zone contains a catalyst; FIG. 5 is a block diagram of FIG. an electric generator f 5a shows an exemplary embodiment of a dual-resonance DC / AC converter; FIG. 6 illustrates the sliding-arc phenomenon appearing in a device according to the invention; FIG. 6a shows curves representing the intensity and current variations in the case of a generator operation in glidarc mode; FIG. 6b shows curves representing the intensity and current variations in the in the case of continuous operation of the generator, - Figure 7 shows a device according to the invention comprising a honeycomb type disk which allows to confine the discharge in a defined area, - Figure 7a shows a device according to the invention in which the end of the tubular electrode consists of a neck and a divergent, - Figure 8 shows a device according to the invention for separating hydrogen from other elements present in the gas, and - Figure 9 shows a device according to the invention having inside the tubular electrode a disk for mixing reagents and a cooling of the central electrode.

  The device that will be described with the figures has a cylindrical geometry of revolution. It comprises an enclosure 100 in which the reaction takes place, and two electrodes 10 and 12 (Figure 1). The first electrode 10 is in a central position along the axis of the enclosure. It has a diameter of 1.5 mm, and is made of a metallic material that has a high electrical conductivity, a high melting temperature and a high corrosion resistance. The second electrode 12 has the shape of a cylindrical tube with an internal diameter of 15 mm and a length of 120 mm. It is made of stainless steel and is the body of the reactor. In the remainder of the description, no distinction will be made between the enclosure 100 and the electrode 12.

  The entire device is thermally insulated by a sleeve 14 which surrounds the tubular electrode 12, to minimize the losses to the outside. This sleeve is for example made of a material based on alumina fibers, 5 cm thick.

  The two electrodes 10 and 12 are electrically insulated from each other by the introduction of a second insulating sleeve 16 of thickness 2 mm around the electrode 10. The insulator is for example a ceramic element based on metal oxide .

  The electrodes 10 and 12 are respectively connected to terminals 18 and 20 of an electric generator described below.

  The tubular electrode 12 comprises, in an example detailed below, a membrane permeable to hydrogen. It also comprises, in one example, a thin layer made of a dielectric material 23 (Figure la) based on alumina 5 microns thick on its inner face. This dielectric layer allows a better distribution of electric charges at the surface of the thin layer and a greater homogeneity of the discharge. Alternatively, the tubular electrode comprises a substrate formed for example of a nickel-based alloy on its inner face.

  The reactive mixture is composed of a hydrocarbon product (hydrocarbon, alcohol, ester, ether or any other product containing hydrogen and carbon) and an oxidizing product (air, water, oxygen-enriched air or a mixture of water and air, enriched or not).

  The reagents are introduced into the chamber 12 with a high speed. These reactants are injected substantially tangentially by injectors 24 and 25 (FIG. 2). These injectors, of diameter 1 mm, are four in number and they are uniformly distributed over a section located 1 cm upstream of the end of the electrode 10. Each injector thus forms an angle of 90 in the plane of the section with each of his two neighbors. This makes it possible to create a helical flow 22 in the axial direction. This helical flow has the advantage of creating a homogeneous medium inside the enclosure.

  The reactants are introduced into the chamber in gaseous form, generally at a temperature of 120 ° C. They can be introduced either separately or premixed.

  In one example, there are several groups of injectors located in different sections of the enclosure (sections 1, 2 and 3 in Figure 1). This makes it possible to inject reagents at different levels of the enclosure, that is to say in different sections located downstream of the first, in order to maintain or reinforce the helical flow over the entire length of the enclosure .

  An electric generator shown in FIG. 5 makes it possible to generate the plasma. This generator is powered by a DC low-voltage source, and it comprises three elements: a resonant-type DC voltage converter 31, a transformer-type voltage booster 32 and a DC voltage converter 33 to straighten the high output voltage.

  An embodiment of the resonance converter is shown in Figure 5a. It is a full bridge double resonance converter. The principle of such a converter is as follows: the DC input voltage is first cut by two semiconductor switches (hereinafter referred to as transistors, of the IGBT or MOSFET type, for example) 40 and 42 respectively placed in parallel with each other. diodes 44 and 46 and two transistors 60 and 62 respectively placed in parallel of diodes 64 and 66. The transistors 40 and 62 are in the on state during all or part of the first half operating period. During all this half-life, the transistors 42 and 60 are blocked. During all or part of the second half-operating period, the transistors 40 and 62 are in the on state. During all this second half of operation, the transistors 42 and 60 are blocked. When a transistor is not in the on state during its half operating period it is its antiparallel diode which is in the on state. A cut-off voltage is thus created across a circuit 38 connected in series with the primary of the transformer 32; this double resonance circuit 38 comprises an inductor 48, in series with an assembly consisting of an inductor 50 and a capacitor 52, themselves connected in parallel. The cut-off voltage can thus excite two resonances: the resonance of the circuit constituted by the inductance 50 and the capacitor 52, and the resonance of the circuit formed by the inductor 48 and the capacitor 52. Thus, the amplitude of the current flowing through the The primary winding of the transformer 32 depends on the switching frequency, which makes it possible to control the electrical power that passes through this transformer. The waveform of the current flowing through the primary winding of the transformer 32 depends on the values of the inductors 48 and 50 and the capacitance of the capacitor 52. The use of a double-resonance converter is preferred because, at a switching frequency high, a high electric power can be generated, while at a lower frequency almost zero power can be generated. The reciprocal is possible according to the values of the components 48,50 and 52 chosen. Thus during the presence of the arc a resistance to this short circuit can be controlled using this double resonance circuit.

  The AC / DC converter is a rectifier of conventional construction or with a voltage multiplier. The constituent components play, as in the DC / AC converter, the role of switches that can rectify the signal and obtain a high DC voltage.

  The experiments carried out in the context of the present invention have shown that the use of this type of generator makes it possible: to maintain the voltage across the electrodes at a very high level (up to several tens of kV), constant and perfectly stable. The voltage level is defined by the geometry of the enclosure and the flow conditions (gas composition, flow, pressure).

  - To keep the current in the discharge at a constant, perfectly stable and adjustable level, whatever the value of the current, even for very low values (1A).

  When the generator is turned on, an electrical discharge 70 is created where the space between the electrodes is minimum, this discharge gives rise to a sliding arc phenomenon, illustrated by Figures 6 and 6a. After a few seconds, this discharge stabilizes. As the reagents are introduced with a certain speed, their displacement leads to a diffusion of the plasma. The discharge is driven by the reagents to reach a very long length and stabilize throughout the enclosure. This discharge results in the creation of a homogeneous plasma inside the enclosure. When the flow is helical, the discharge is stabilized as a vortex.

  It can be seen from the curves of FIG. 6b that the intensity of the current 72 is very small (less than 1A), and the voltage 74 is relatively high (of the order of a few kV).

  Thanks to this electric generator, the electric discharge obtained stabilizes under very specific electrical conditions of high voltage (typically between 1 and 10 kV) and very low intensity of the current (typically less than 1A). In addition, the electric generator makes it possible to perfectly adjust the delivered current, and thus to dynamically control the plasma. A very homogeneous plasma is thus obtained, which allows a large fraction of the reactants to pass in front of the active zone consisting of the electric discharge. The conversion yield thus obtained is relatively high.

  In an example using a device according to Figure 1, maintained at atmospheric pressure, is introduced an air-water-isooctane mixture in the following proportions: - Air: 5.3 Nm3 / h, -Isooctane: 0.3 g / s, - Water 0.7 g / s.

  It should be noted that the unit Nm3, which means normal m3, represents the quantity of gas, free of water vapor, which, at a temperature of 0 C and an absolute pressure of 1.01325 bar, occupies a volume of 1 m3 .

  After ignition of the arc, a DC voltage of 4800 V is established at the terminals of the electrodes and the current in the discharge is maintained at 200 mA, which corresponds to a power dissipated in the discharge of 960 W. At the output of The reactor obtained a mixture of volume composition (or molar) following: - Hydrogen (H2): 22%, - Carbon monoxide (CO): 14%, - Carbon dioxide (CO2): 7%, - Methane (CH4) : 1%, - Nitrogen (N2): 56%.

  In an embodiment shown in FIG. 3, a heat exchanger 26 is provided in the device in order to vaporize reagents introduced in liquid form, and which must therefore be transformed into gas before being able to react. In this example isooctane is introduced into the device in liquid form (0.3 g / s), and air (5 Nm3 / h). The electrode 12 is, in this case, made of a nickel-based metal alloy. The isooctane is introduced into the system in liquid form at 20 C. It is preheated and totally vaporized before being introduced into the reactor through injectors 24. The air is, meanwhile, introduced at 20 C by the injectors 25.

  After ignition of the arc, a DC voltage of 5400 V is established and the current is maintained at 180 mA, which corresponds to a power dissipated in the discharge of 972 W. At the outlet of the reactor, a mixture of compositions is obtained. volume (or molar) according to: - Hydrogen (H2): 16%, Carbon monoxide (CO): 20%, - Carbon dioxide (CO2): 4%, - Methane (CH4): 0.5%, - Nitrogen (N2) ): 59.5%.

  In another example, the device is extended by a post-reactive zone, as shown in FIG.

  This post-reactive chamber 28 comprises a stainless steel cylinder 500 mm in length. In this chamber is introduced a tube of alumina 29 of length 500 mm and 25 mm internal diameter, which keeps the chamber at high temperature.

  An air-water-isooctane mixture is introduced in the following proportions: - Air: 5.3 Nm3 / h, - Isooctane: 0.3 g / s, - Water: 0.7 g / s.

  The reactants are introduced premixed and the pressure in the chamber is maintained at a value of 2 bars.

  After ignition of the arc, a DC voltage of 5900 V is established and the current is maintained at 310 mA, which corresponds to a power dissipated in the discharge of 1829 W. At the outlet of the reactor, a mixture of compositions is obtained. volume (or molar) according to: - Hydrogen (H2): 23%, Carbon monoxide (CO): 17%, - Carbon dioxide (CO2): 6%, - Methane (CH4): 1%, - Nitrogen (N2) ): 53%.

  In another example, a device shown in FIG. 4a is used. A catalytic bread 30 consisting of a honeycomb structure made of alumina is introduced inside the alumina tube 29. This catalytic bread, which allows the circulation of gases, comprises a deposition thin layer of nickel metal on its outer surface, a thickness of 8 microns.

  An air-water-isooctane mixture is introduced in the following proportions: - Air: 11 Nm3 / h, - Isooctane: 0.6 g / s, - Water: 1 g / s.

  The reactants are introduced premixed and the pressure in the chamber is maintained at a value of 5 bars.

  After ignition of the arc, a DC voltage of 12000 V is established and the current is maintained at 150 mA, which corresponds to a power dissipated in the 1800 W discharge. At the outlet of the reactor, a composition mixture is obtained. volume (or molar) according to: - Hydrogen (H2): 24%, - Carbon monoxide (CO): 15%, - Carbon dioxide (CO2): 5%, Methane (CH4): 0.5%, - Nitrogen (N2) ): 55.5%.

  In another example, a device represented in FIG. 7 is used. At the end of the tubular electrode 12 is inserted a honeycomb-type alumina disk 80 of thickness 5 mm. This disc allows the passage of reagents while maintaining a slight overpressure in the discharge chamber, which allows to confine the discharge in a defined area and stabilize the combustion reactions related to the propagation of the flame front.

  An air-water-isooctane mixture is introduced in the following proportions: - Air: 4.7 Nm3 / h, - Isooctane: 0.3 g / s, - Water: 0.8 g / s.

  The reactants are introduced premixed and the pressure in the chamber is maintained at a value of 5 bars.

  After ignition of the arc, a DC voltage of 4200 V is established and the current is maintained at 300 mA, which corresponds to a power dissipated in the discharge of 1260 W. At the outlet of the reactor, a composition mixture is obtained. volume (or molar) according to: - Hydrogen (H2): 24%, Carbon monoxide (CO): 18%, - Carbon dioxide (CO2): 5%, - Methane (CH4): 0.5%, - Nitrogen (N2) ): 52.5%.

  In another embodiment, in accordance with FIG. 7a, the end of the tubular electrode 12 consists of a neck 82 followed by a divergent 84. This device makes it possible to stabilize the electric discharge by confining the attachment of the bow at the collar. Furthermore, this device for controlling the attachment zone of the arc, it is possible, by varying the position of the neck and its divergent, to vary the voltage of the discharge and thus to finely control the power injected in the dump.

  In another example, a device shown in FIG. 8 is used. The body of the reactor comprises a tube 86 which makes it possible to ensure the positioning of a membrane 88 made of a conductive material that is permeable to hydrogen. This device makes it possible to combine two functions: electrode and in situ separation of hydrogen. The H2 hydrogen is sucked continuously through a device 90, which makes it possible to reduce the partial pressure of the hydrogen in the discharge, and thus to shift the thermodynamic equilibrium and to increase the conversion to hydrogen. hydrogen is extracted from the reactive zone through the permeable membrane. This has the effect of creating a lack, or a partial underpressure of hydrogen, which increases the conversion rate.

  In another example, shown in FIG. 9, a disk 11 made of boron nitride is inserted inside the tubular electrode 12 and pierced to pass the central electrode 10. The positioning of the disk 11 creates a chamber 13 in which the reagents having been introduced separately can be mixed. This device also makes it possible to achieve a very efficient cooling of the central electrode 10 and the electrical insulator 16 by the injected gases. Indeed, the gases trapped in the mixing chamber are at a lower temperature than that of the plasma.

  Furthermore, the gases are accelerated because they are introduced into the chamber by a duct of smaller section than the chamber, which has the effect of accelerating the speed of the gases and thus the cooling of the part of the chamber. electrode 10 being in contact with the plasma.

2888835 20

Claims (21)

  1. A process for producing hydrogen from a hydrocarbon product and an oxidizing product, the reaction being carried out in a chamber (100), having a cylindrical symmetry about an axis and in which the products circulate, a helicoidal flow of the reactants along the axis of the chamber being created in this chamber, and creating an electric discharge (70) producing a non-thermal plasma, the electric discharge being selected so that the plasma is such that it is driven by products to occupy most of the enclosure.   2. The method of claim 1 wherein the discharge is produced by a generator for a stable discharge and occupying the entire length of the enclosure.   The method of claim 1 or 2 wherein the electric discharge (70) is produced by a DC electric generator which comprises a resonance type AC direct current converter (31).   4. The method of claim 3 wherein the intensity of the current is at most 1 ampere.   5. The method of claim 3 or 4 wherein a single or double resonance converter, preferably double resonance, is used.   6. Method according to one of claims 3 to 5 wherein the electric generator, powered by a DC low voltage electrical source, comprises: - a DC / AC converter type resonant converter (31), - an elevator voltage converter (32), and an AC / DC converter (33).   7. Method according to one of the preceding claims, wherein the helical flow is achieved by a substantially tangential injection of at least one of the reagents into the chamber (100), by one or more injector (s) (24 or 25) distributed in at least one of the sections (section 1, section 2 or section 3) of this chamber.   8. The method of claim 7 wherein the number of injectors is between 2 and 6 in each section, these injectors preferably equidistributed around the axis.   9. The method of claim 7 or 8 wherein there is provided a plurality of groups of injectors, a group being on a different section of the section on which there is another group.   10. Method according to one of the preceding claims wherein the reagents are introduced in gaseous form into the device, either separately or premixed.   11. Method according to one of the preceding claims, wherein the enclosure comprises a post-reactive zone (28) maintained at high temperature.   The method of claim 11, wherein the post-reactive zone contains a catalyst (30).   13. Method according to one of the preceding claims wherein the hydrocarbon product is a product included in the group comprising: pure hydrocarbons, automotive fuels, fuels used for aerial and marine propulsion, alcohols, ethers and esters .   14. Method according to one of the preceding claims wherein the oxidizing product is a product included in the group comprising: air, mixtures composed of air and water, air more or less enriched with oxygen, mixtures of oxygen enriched air and water.   15. Method according to one of the preceding claims wherein the enclosure is maintained at a pressure of between 1 and 20 bar.   16. Method according to one of the preceding claims wherein the current generator is connected to two electrodes of which one is axial (10) and the other is in the form of a cylindrical tube of the same axis (12).   17. The method of claim 16 wherein the cylindrical electrode comprises a membrane (88) permeable to hydrogen.   18. The method of claim 16 or 17 wherein a cylindrical electrode having a dielectric thin film is used on its inner surface.   19. Method according to one of claims 16 to 18 according to which the cylindrical electrode comprises a catalyst.   20. The method of claim 19 wherein the cylindrical electrode comprises a nickel-based alloy.   21. Hydrogen production system implementing the method according to one of claims 3 to 9 and 16 to 20.