Methods for (co)electrolysis of water (SOEC) or for producing electricity at a high temperature with exchangers incorporated as stages of a reactor stack (HTE) or a fuel cell (SOFC)

Abstract

The invention relates to the production or a heat-transfer gas circuit for the heat management/regulation of the stack of an HTE reactor or an SOFC fuel cell by removing certain cells in certain areas of the stack in order to replace them with electrical contact elements that allow the heat transfer gas to pass through.

Claims

1. A high-temperature electrolysis reactor, comprising an alternating stack of two groups of distinct stages, including: a group of a plurality of electrochemical stages, each consisting of an individual electrolysis cell of SOEC solid oxide type, formed from a cathode, an anode and an electrolyte inserted between the cathode and the anode, and two interconnectors, each suitable for electrical and fluid interconnection, arranged on either side of the individual electrolysis cell, and a group of at least one thermal regulation stage, consisting of at least one electrical contact element allowing gases to pass, and two interconnectors, each suitable for electrical and fluid interconnection, arranged on either side of the at least one electrical contact element, wherein the interconnectors of the electrochemical stages and the at least one thermal regulation stage are suitable for both (i) and (ii): (i) circulating, through the stack, steam or a mixture of steam and carbon dioxide, a draining gas, and a heat-exchange gas, and (ii) recovering hydrogen or synthesis gas produced at the cathodes of the electrolysis cells, oxygen produced at the anodes of the electrolysis cells, and where appropriate the draining gas, and the heat-exchange gas at an outlet of the at least one electrical contact element, the interconnectors of the electrochemical stages are also suitable for distributing both steam or the mixture of steam and carbon dioxide to the cathodes of the electrolysis cells, and the draining gas to the anodes of the electrolysis cells, and the interconnectors of the at least one thermal regulation stage are suitable for distributing solely the heat-exchange gas to the at least one electrical contact element.

2. The high-temperature electrolysis reactor of claim 1, wherein the at least one electrical contact element is a metal grid.

3. The high-temperature electrolysis reactor of claim 1, wherein the interconnectors of the electrochemical stages each consist of a device consisting of three flat metal sheets of a first end metal sheet, a second end metal sheet, and a central metal sheet, the three flat metal sheets are elongated along two axes of symmetry (X, Y) orthogonal to one another, one of the first and second end metal sheets is configured to come into mechanical contact with a plane of the cathode of the individual electrolysis cell and the other of the first and second end metal sheets is configured to come into mechanical contact with a plane of the anode of the adjacent individual electrolysis cell, central parts of the central metal sheet and the first end metal sheet are not pierced, while a central part of the second end metal sheet is pierced, each of the three flat metal sheets is pierced, at a periphery of the central part thereof, with six ports, the first to fourth ports of each flat metal sheet being elongated over a length corresponding to a portion of a length of the central parts along one of the axes X of the flat metal sheets and being distributed in pairs on either side of said axis X, while the fifth and sixth ports are elongated over a length corresponding substantially to a length of the central parts along the other of the axes Y, the first end metal sheet also comprises a seventh and an eighth port arranged symmetrically on either side of the axis X, inside its first to fourth ports, and elongated over a length corresponding substantially to a length of the central part along the axis X, the second end metal sheet also comprises a seventh and an eighth port arranged symmetrically on either side of the axis Y, inside its fifth and sixth ports, respectively, and elongated over a length corresponding substantially to the length of the central part along said axis Y, the first, third, fifth and sixth ports of the central metal sheet are widened relative to the first, third, fifth and sixth ports of each end metal sheet, respectively, while the second and fourth ports of the three flat metal sheets are of substantially identical dimensions to one another, all the widened ports of the central metal sheet comprise tongues of metal sheets spaced apart from one another, forming a comb with a plurality of slits, each slit between an edge of the widened port and the adjacent tongue or between two consecutive tongues opening onto one inner port of the first or second end metal sheet, and the three flat metal sheets are laminated and assembled together such that: the tongues of metal sheets form spacers between the first and second end metal sheets, between the first and seventh ports of the first end metal sheet, between the third and eighth ports of the first end metal sheet, between the fifth and seventh ports of the second end metal sheet, and between the sixth and eighth ports of the second end metal sheet, each of the first to sixth ports of one of the three flat metal sheets is individually in fluid communication with one of the corresponding first to sixth ports of the two other metal sheets, the first or alternatively the second port of the first end metal sheet is in fluid communication with the seventh port of the first end metal sheet via the slits of the first widened port of the central metal sheet, the third or alternatively the fourth port of the first end metal sheet is in fluid communication with the eighth port of the first end metal sheet via the slits of the third widened port of the central metal sheet, the fifth and the seventh ports of the second end metal sheet are in fluid communication via the slits of the fifth widened port of the central metal sheet, and the sixth and the eighth ports of the second end metal sheet are in fluid communication via the slits of the sixth widened port of the central metal sheet.

4. The high-temperature electrolysis reactor of claim 3, wherein at least one of the two interconnectors of the at least one thermal regulation stage is constituted from three flat metal sheets of a first end metal sheet, a second end metal sheet, and a central metal sheet, and the three flat metal sheets of the at least one interconnector of the at least one thermal regulation stage are identical to the three flat metal sheets of the interconnectors of the electrochemical stages except that the second end metal sheet of the at least one interconnector of the at least one thermal regulation stage does not comprise the seventh and the eighth ports.

5. The high-temperature electrolysis reactor of claim 3, wherein the two interconnectors of the same electrochemical stage each are constituted from three identical flat metal sheets, but with the central metal sheet of one of the interconnectors turned upside down relative to the central metal sheet of the other interconnector.

6. The high-temperature electrolysis reactor of claim 1, wherein a number of the at least one thermal regulation stage is different from a number of the electrochemical stages.

7. The high-temperature electrolysis reactor of claim 1, wherein a number of the at least one thermal regulation stage is higher at the center of the stack than at the ends of the stack.

8. The high-temperature electrolysis reactor of claim 1, wherein the at least one thermal regulation stage is not visible from the outside of the stack.

9. A high-temperature fuel cell, comprising an alternating stack of two groups of distinct stages, including: a group of a plurality of electrochemical stages, each consisting of an individual electrochemical cell of SOFC solid oxide type, formed from a cathode, an anode and an electrolyte inserted between the cathode and the anode, and two interconnectors, each suited for electrical and fluid interconnection, arranged on either side of the individual electrochemical cell, and a group of at least one thermal regulation stage, consisting of at least one electrical contact element allowing gases to pass, and two interconnectors, each suitable for electrical and fluid interconnection, arranged on either side of the at least one electrical contact element, wherein the interconnectors of the electrochemical stages and the at least one thermal regulation stage are suitable for both (i) and (ii): (i) circulating, through the stack, a fuel, an oxidizer, and a heat-exchange gas, and (ii) recovering a surplus fuel and water produced at the anodes of the electrochemical cells, a surplus oxidizer at the cathodes of the electrochemical cells, and the heat-exchange gas at an outlet of the at least one electrical contact element, the interconnectors of the electrochemical stages are also suitable for distributing both the fuel to the anodes of the electrochemical cells and the oxidizer to the anodes of the electrochemical cells, and the interconnectors of the at least one thermal regulation are suitable for distributing solely the heat-exchange gas to the at least one electrical contact element.

10. A method for electrolysis of steam or co-electrolysis of a mixture of steam and carbon dioxide in the high-temperature electrolysis reactor of claim 1, the method comprising: supplying the steam or the mixture from the interconnectors of the electrochemical stages as fuel, and distributing the fuel to the cathodes of the electrolysis cells, then recovering hydrogen or the synthesis gas at an outlet of the cathodes, supplying the draining gas from the interconnectors of the electrochemical stages and distributing the draining gas to the anodes of the electrolysis cells, then recovering oxygen produced and where appropriate the draining gas at an outlet of the anodes, and supplying the heat-exchange gas from the interconnectors of the at least one thermal regulation stage and distributing the heat-exchange gas to the at least one electrical contact element, then recovering the heat-exchange gas at the outlet of the at least one electrical contact element.

11. The method of claim 10, wherein the heat-exchange gas is the fuel or the draining gas.

12. The method of claim 10, wherein the supplying of the fuel is connected in series to the supplying of the heat-exchange gas.

13. The method of claim 10, wherein the supplying of the fuel is in coflow to the supplying of the heat-exchange gas.

14. The method of claim 10, wherein the supplying of the fuel is in counterflow to the supplying of the heat-exchange gas.

15. The method of claim 10, wherein an exothermic or endothermic chemical reaction is carried out between the heat-exchange gas and the at least one electrical contact element.

16. A method for producing electricity at high temperature in the high-temperature electrolysis reactor of claim 2, the method comprising: supplying a fuel from the interconnectors of the electrochemical stages and distributing the fuel to the anodes of the electrolysis cells, then recovering a surplus fuel and water produced at an outlet of the anodes, supplying an oxidizer from the interconnectors of the electrochemical stages and distributing the oxidizer to the cathodes of the electrolysis cells, then recovering a surplus oxidizer at an outlet of the cathodes, and supplying the heat-exchange gas from the interconnectors of the at least one thermal regulation stage and distributing the heat-exchange gas to the at least one electrical contact element, then recovering the heat-exchange gas at the outlet of the at least one electrical contact element.

17. The method of claim 16, wherein the fuel is hydrogen or methane.

Description

DETAILED DESCRIPTION

(1) Other advantages and features of the invention will become more clearly apparent on reading the detailed nonlimiting and illustrative description of exemplary embodiments of the invention given with reference to the following figures, in which:

(2) FIG. 1 is a schematic view showing the operating principle of a high-temperature water electrolyzer;

(3) FIG. 2 is a schematic exploded view of a part of a high-temperature steam electrolyzer comprising interconnectors according to the state of the art,

(4) FIG. 3 is a schematic exploded view of a part of a high-temperature SOFC fuel cell comprising interconnectors according to the state of the art,

(5) FIG. 4 is a section of an electrolysis reactor implementing a method for high-temperature electrolysis according to one mode of the invention,

(6) FIG. 5 is an exploded view of a part of an electrolysis reactor according to the invention with an electrolysis stage adjacent to a thermal regulation stage,

(7) FIGS. 6A and 6B are exploded views of an interconnector of an electrolysis stage according to the invention which enables a supply/recovery of the steam and the hydrogen produced, and a supply/recovery of the heat-exchange gas, the figures showing the supply, distribution and recovery of the steam and of the hydrogen produced in FIG. 6A and the heat-exchange gas in FIG. 6B,

(8) FIG. 6C is an exploded view of the interconnector according to FIGS. 6A and 6B, showing the supply, distribution and recovery of the draining gas and of the oxygen produced,

(9) FIG. 7A is a front view of an end metal sheet of an interconnector according to FIG. 6A, showing the supply, distribution and recovery of the steam and of the hydrogen produced,

(10) FIG. 7B is a front view of an end metal sheet of an interconnector according to FIG. 6B, showing the supply, distribution and recovery of the heat-exchange gas according to the invention,

(11) FIG. 7C is a front view of an end metal sheet of an interconnector according to FIG. 6A or 6B, showing the supply, distribution and recovery of the draining gas and of the oxygen produced,

(12) FIG. 7D is a perspective view of an interconnector according to FIG. 6A or 6B,

(13) FIG. 8 is an exploded view of an interconnector of a thermal regulation stage according to the invention, this figure showing the absence of port for the supply, distribution and recovery of the draining gas and of the oxygen at the thermal regulation stage,

(14) FIGS. 9A and 9B are detail views of a part of an interconnector according to the invention.

(15) It is specified here that, in all of FIGS. 1 to 8, the symbols and arrows of supply of steam H.sub.2O, of distribution and recovery of dihydrogen H.sub.2 and of oxygen O.sub.2 and of the current are shown for the purposes of clarity and precision, to illustrate the operation of a steam electrolysis reactor according to the state of the art and of a steam electrolysis reactor according to the invention.

(16) It is also specified that all the electrolysers described are of solid oxide type (SOEC, acronym for Solid Oxide Electrolysis Cell) operating at high temperature. Thus, all the constituents (anode/electrolyte/cathode) of an electrolysis cell are ceramics. The high operating temperature of an electrolyzer (electrolysis reactor) is typically between 600 C. and 950 C.

(17) Typically, the characteristics of an individual SOEC electrolysis cell suitable for the invention, of the cathode-supported type (CSC), may be those indicated as follows in the table below.

(18) TABLE-US-00001 TABLE Electrolysis cell Unit Value Cathode 2 Constituent material Ni-YSZ Thickness m 315 Thermal conductivity W m.sup.1 K.sup.1 13.1 Electrical conductivity .sup.1 m.sup.1 10.sup.5 Porosity 0.37 Permeability m.sup.2 10.sup.13 Tortuosity 4 Current density A .Math. m.sup.2 5300 Anode 4 Constituent material LSM Thickness m 20 Thermal conductivity W m.sup.1 K.sup.1 9.6 Electrical conductivity .sup.1 m.sup.1 1 10.sup.4 Porosity 0.37 Permeability m.sup.2 10.sup.13 Tortuosity 4 Current density A .Math. m.sup.2 2000 Electrolyte 3 Constituent material YSZ Thickness m 90 m in support electrolyte and 5 m in support electrode Resistivity m 0.42

(19) FIGS. 1 to 3 have already been described in detail in the preamble. They are therefore not described hereafter.

(20) By convention, and in order to facilitate the reading of the circulations of the gases in the different figures, the following symbols are used:

(21) EH.sub.2(1): denotes the circulation, through the stack, of the steam as fuel supplying the electrolysis cells C1, C2;

(22) SH.sub.2(1): denotes the circulation, through the stack, of the hydrogen produced by the electrolysis cells C1, C2;

(23) EH.sub.2(2): denotes the circulation, through the stack, of the heat-exchange gas supplying the thermal regulation stages;

(24) SH.sub.2(2): denotes the circulation, through the stack, of the heat-exchange gas at the outlet of the thermal regulation stages;

(25) E(O.sub.2): denotes the circulation, through the stack, of the draining gas supplying the electrolysis cells C1, C2;

(26) S(O.sub.2): denotes the circulation, through the stack, of the oxygen produced at the electrolysis cells C1, C2.

(27) In order to improve the management of the thermal operations of the electrolysis reactor of the electrochemical stages, more particularly those at the center of the stack which do not have the possibility of exchange with the outside environment, the inventors have wisely thought to integrate thermal regulation stages within the stack by employing flat metal sheet interconnectors whose structure is barely modified compared to those intended for the electrochemical stages, and by arranging electrical contact elements allowing the gases to pass instead of the electrolysis cells.

(28) Thus, as illustrated in FIG. 4, the following steps are carried out simultaneously within the stack according to the invention:

(29) the steam EH.sub.2(1) is supplied from the interconnectors 5.1, 5.2 of the electrochemical stages as fuel, and it is distributed to the cathodes of the electrolysis cells C1, C2, then the hydrogen H.sub.2 produced SH.sub.2(1) is recovered at the outlet of the cathodes 2.1, 2.2,

(30) a draining gas, such as air, E(O.sub.2), is supplied from the interconnectors 5.1, 5.2 of the electrochemical stages and it is distributed to the anodes 4.1, 4.2 of the cells, then the oxygen O.sub.2 produced and where appropriate the draining gas S(O.sub.2) is recovered at the outlet of the anodes,

(31) a heat-exchange gas EH.sub.2(2) is supplied from the interconnectors 5.2, 5.3 of the thermal regulation stages and it is distributed to the electrical contact elements 14, then it is recovered at the outlet of these elements 14 SH.sub.2(2).

(32) Thus, according to the invention, the majority of the usual electrochemical stages of an EHT reactor stack are retained, which stages are intended for the electrolysis of the steam, and stages with a thermal regulation function are added thereto, instead of electrochemical stages, in order to regulate the heat of the reactions in these zones.

(33) According to the invention, it is provided that the circuit of the thermal regulation stages is swept with a sufficiently reducing heat-exchange gas to avoid the oxidation of the contact elements 14. Thus, the heat-exchanger may advantageously be a mixture of steam and hydrogen. In this case, the hydrogen is present at at least 10%, in order to avoid the oxidation of the contact elements 14, especially in the form of a nickel grid.

(34) FIG. 5 shows a schematic representation of a part of a high-temperature solid oxide electrolyzer (SOEC) according to the invention.

(35) This electrolyzer electrolysis reactor comprises an alternating stack of an individual electrolysis cell of SOEC type (C1) formed from a cathode 2.1, 2.2, from an anode 4.1, 4.2, and from an electrolyte 3.1, 3.2, inserted between the cathode and the anode, and from a metal grid 14.

(36) This metal grid provides electrical continuity in series through the thermal regulation stage.

(37) The electrochemical stage comprises two electrical and fluid interconnectors 5.1, 5.2, arranged either side of the individual cell C1 with the cathode in electrical contact with the lower face of the above interconnector 5.1 and the anode in electrical contact with the upper face of the below interconnector 5.2.

(38) The thermal regulation stage also comprises two electrical and fluid interconnectors 5.2, 5.3, the above one of which 5.2 is shared with the electrochemical stage. The two interconnectors 5.2, 5.3 are arranged on either side of the metal grid 14.

(39) As shown in FIG. 5, insulation and leaktightness frames 9 are also provided, making it possible to provide electrical insulation between interconnectors 5.1 and 5.2 on the one hand and between interconnectors 5.2, 5.3 on the other. It should be noted that, between the two interconnectors 5.2 and 5.3, the frame 9 serves first and foremost for leaktightness, since electrical insulation is not required on the stage intended for thermal management.

(40) Each frame 9 is pierced with ports 99, suitable for accommodating rods for fixing the stack, and also seals 10 provided to produce leaktightness around the ports 91, 92, 93, 94, 95, and 96 for supplying the gases H.sub.2O and air and for recovering the gases produced H.sub.2, O.sub.2 with air, and also around the manifolds intended for the heat-exchange gas.

(41) A contact layer 11, such as a metal grid made of nickel, makes it possible to provide contact between the cathode of the cell C1 and the above interconnector 5.1.

(42) Another seal 12 is also provided at the periphery of the anode of the cell, to provide leaktightness for the oxygen produced.

(43) The assembly of the stack comprising the electrolysis cell C1 and the metal grid 11 for passage of the heat-exchange gas is passed through by the same electrical current.

(44) In the reactor according to the invention, all the cathode compartments 50 of the electrochemical stages, in which the steam H.sub.2O supplied and the hydrogen H.sub.2 produced circulate, communicate with one another.

(45) Similarly, all the thermal regulation stages, in which the heat-exchange gas circulates, communicate with one another.

(46) According to the invention, an interconnector 5.3 intended for a thermal regulation stage is different from an interconnector 5.1 intended for an electrochemical stage, in order to be able to solely carry out a supply of heat-exchange gas, without introducing fuel, at a metal grid 14.

(47) FIGS. 6A to 6C each show an exploded view of an interconnector 5.1 or 5.2 of an electrochemical stage according to the invention, making it possible to provide both:

(48) the supply of steam H.sub.2O as fuel, the circulation of the steam and of the hydrogen produced at the cell C1, the recovery of the hydrogen produced, and also the supply and recovery of the oxygen O.sub.2 produced within the stack of an electrolysis reactor,

(49) the supply of heat-exchange gas, the circulation of this heat-exchange gas at a metal grid 14, and also the recovery thereof, having circulated over a metal grid 14 within the stack of an electrolysis reactor.

(50) Each interconnector 5.1, 5.2 intended for an electrochemical stage makes it possible to provide a circulation of the gas (H.sub.2O/H.sub.2) to the cathodes of the cells at 90 cross-current with the circulation of the recovered gas (O.sub.2) and the draining gas at the anode of the cells.

(51) The interconnector 5.1 or 5.2 consists of three flat metal sheets 6, 7, 8, elongated along two axes of symmetry (X, Y) orthogonal to one another, the flat metal sheets being laminated and assembled together by welding. A central metal sheet 7 is inserted between a first 6 and a second 8 end metal sheet.

(52) The first 6 end metal sheet is intended to come into mechanical contact with the plane of a cathode 2.1 of the individual electrolysis cell C1 and the central metal sheet 7 is intended to come into mechanical contact with the plane of an anode 4.1 of an adjacent individual electrolysis cell, each of the two adjacent individual electrolysis cells (C1, C2) of SOEC type being formed from a cathode 2.1, 2.2, from an anode 4.1, 4.2, and from an electrolyte 3.1, 3.2, inserted between the cathode and the anode.

(53) Each of the three flat metal sheets 6, 7, 8 comprises a central part 60, 70, 80.

(54) The central parts 60, 70 of the central metal sheet 7 and of the first end metal sheet 6 are not pierced, while the central part 80 of the second end metal sheet 80 is pierced.

(55) Each metal sheet 6, 7, 8 is pierced, at the periphery of the central part thereof, with six ports 61, 62, 63, 64, 65, 66; 71, 72, 73.74, 75, 66; 81, 82, 83, 84, 85, 86.

(56) The first 61, 71, 81 to fourth 64, 74, 84 ports of each metal sheet are elongated over a length corresponding to a portion of the length of the central part 60, 70, 80 along one of the axes X of the metal sheets, and are distributed pairwise on either side of said axis X.

(57) The fifth 65, 75, 85 port is elongated over a length corresponding substantially to the length of the central part 60, 70, 80 along the other of the axes Y.

(58) The sixth 66, 76, 86 port is elongated over a length corresponding substantially to the length of the central part 60, 70, 80 along the other of the axes Y.

(59) The first 6 end metal sheet also comprises a seventh 67 and an eighth 68 port arranged symmetrically on either side of the axis X, inside its first to fourth ports 61 to 64, and are elongated over a length corresponding substantially to the length of the central part along the axis X.

(60) The second 8 end metal sheet also comprises a seventh 87 and an eighth port arranged symmetrically on either side of the axis Y inside, respectively, its fifth 85 and its sixth 86 port, and elongated over a length corresponding substantially to the length of the central part along said axis Y.

(61) As can be seen in FIG. 6A, the first 71, third 73, fifth 75 and sixth 76 ports of the central metal sheet 7 are widened relative, respectively, to the first 61, 81, third 63, 83, fifth 65, 85 and sixth 66, 86 ports of each end metal sheet 6, 8.

(62) The second 62, 72, 82 and fourth 64, 74, 84 ports of the three metal sheets are of substantially identical dimensions to one another.

(63) The lamination and the assembly of the three metal sheets 6, 7, 8 with one another are carried out such that:

(64) each of the first to sixth ports 61 to 66 of one of the three metal sheets is individually in fluid communication respectively with one of the corresponding first to sixth ports 71 to 76 and 81 to 86 of the two other metal sheets 7, 8,

(65) the first port 61 of the first 6 end metal sheet is in fluid communication with the seventh port 67 of the first 6 end metal sheet via the first port 71 of the central metal sheet 7,

(66) the third port 63 of the first 6 end metal sheet is in fluid communication with the eighth port 68 of the first 6 end metal sheet via the third port 73 of the central metal sheet 7,

(67) the fifth 85 and the seventh 87 ports of the second 8 end metal sheet are in fluid communication via the fifth 75 port of the central metal sheet 7,

(68) the sixth 86 and the eighth 88 ports of the second 8 end metal sheet are in fluid communication via the sixth 76 port of the central metal sheet 7.

(69) FIGS. 9A and 9B show in detail the production of the comb formed by the tongues of metal sheet 710 at the widened slit 71 of the central metal sheet and its arrangement between the two end metal sheets 6, 8 in order to enable the supply of an electrolysis cell, here with steam H.sub.2O, or of a metal grid 14 at a thermal regulation stage, as detailed below. Thus, the comb formed 710, 711 enables the steam to pass from the supply manifold 61, 71, 81 to the distribution slit 67, by passing into the space between the two end metal sheets 6, 8. The thickness of the central metal sheet 7 at this comb 710, 711 provides it with a spacer function and thereby guarantees the height of the passage for the steam into the space between the end metal sheets 6, 8. Such a passage of gases according to the invention via the inside of the interconnector 5.1 has the advantage of liberating a flat surface for producing seals. In addition, by virtue of these comb forms for the widened slits 71, 75 a homogeneous distribution is obtained of each gas (H.sub.2O, air) over each electrolysis cell and over each metal grid of the thermal stage, and by virtue of these comb forms for the widened slits 73, 76 a recovery is obtained of the gas produced (H.sub.2, O.sub.2) or of the heat-exchange gas. These homogeneous distributions or recoveries or, in other words, these distributions or recoveries which are uniform in terms of flow rate, are shown in the different FIGS. 6A to 8 in the form of small arrows spaced apart from one another.

(70) In order to produce the interconnector 5.2 represented in FIG. 6B, which makes it possible both to convey the draining gas to the cell C1 and the heat-exchange gas to the metal grid 14, the same three flat metal sheets 6, 7, 8 are used as those used for producing the interconnector 5.1, but the central metal sheet 7 is merely turned upside down before its lamination and assembly with the two end metal sheets 6, 8.

(71) Thus, in the interconnector 5.2, the three metal sheets 6, 7, 8 are laminated and assembled together such that:

(72) each of the first to sixth 61 to 66 ports of one of the three metal sheets is individually in fluid communication respectively with one of the corresponding first to sixth 71 to 76 and 81 to 86 ports of the two other metal sheets 7, 8,

(73) the second port 62 of the first 6 end metal sheet is in fluid communication with the seventh 67 port of the first 6 end metal sheet via the third 73 port of the central metal sheet 7,

(74) the fourth port 64 of the first 6 end metal sheet is in fluid communication with the eighth 68 port of the first 6 end metal sheet via the first 71 port of the central metal sheet 7,

(75) the fifth 85 and the seventh 87 ports of the second 8 end metal sheet are in fluid communication via the fifth 75 port of the central metal sheet 7,

(76) the sixth 86 and the eighth 85 ports of the second 8 end metal sheet are in fluid communication via the sixth 76 port of the central metal sheet 7.

(77) In order to produce the interconnector 5.3 represented in FIG. 8 which makes it possible not to convey draining gas or oxygen to or to recover oxidizer gas at the metal grid 14, the same three flat metal sheets 6, 7, 8 are used as those used for producing the interconnectors 5.1 and 5.2, retaining all the ports intended for the supply/recovery of the gases with the exception of the ports 87, 88 which are removed.

(78) In other words, an interconnector 5.3 is created intended for a thermal regulation stage, starting from exactly the same flat metal sheets 6, 7, 8 constituting the interconnectors 5.1, 5.2 intended for an electrochemical stage, and removing solely the ports 87, 88 or slits usually intended for the function of supplying draining gas and of recovering the oxygen O.sub.2 produced.

(79) Thus, according to the invention, by means of an interconnector identical in its structure to laminated and assembled flat metal sheets and in its thicknesses and forms to those intended for the electrochemical stages, a stage intended for thermal regulation is produced.

(80) By virtue of the invention, an alternating stack of thermal regulation stages and of electrochemical stages is thus obtained, the thermal regulation of which, in particular in the center of the stack, is very effective, and the production cost of which is less compared to the solutions according to the state of the art, since all the interconnectors 5.1, 5.2, 5.3 are produced with the same flat metal sheets 6, 7, 8, and thus according to the same manufacturing ranges, and some electrolysis cells are replaced by metal grids which provide electrical continuity through the stack.

(81) The operating method of an electrolysis reactor according to the invention, as has just been described, will now be described with reference to FIGS. 6A to 8.

(82) The first 61, 71, 81 ports of the interconnectors 5.1 to 5.3 are supplied with steam EH2(1) and simultaneously the second 62, 72, 82 ports of the interconnectors 5.1 to 5.3 are supplied with heat-exchange gas EH.sub.2(2).

(83) The heat-exchange gas EH.sub.2(2) passes through the interconnector 5.1 without being distributed to the cathode 2.1 of the cell C1. It supplies the ports 62, 73 and 82 of the interconnector 5.2.

(84) Similarly, the steam EH.sub.2(1) passes through the interconnector 5.2 without being distributed on the metal grid 14.

(85) The path, within an interconnector 5.1, of the steam injected and of the hydrogen produced, is illustrated schematically in FIGS. 6A and 7A.

(86) The path, within an interconnector 5.2, of the heat-exchange gas within an interconnector 5.2, is schematically illustrated in FIGS. 6B and 7B.

(87) In addition, the fifth 65, 75, 85 ports of the three metal sheets 8 of each interconnector 5.1, 5.2, 5.3 are supplied with a draining gas E(O.sub.2), such as air.

(88) The path of the air as draining gas injected and of the oxygen produced within an interconnector 5.1 or 5.2 is schematically illustrated in FIG. 6C.

(89) Due to the absence of the ports 87, 88 within the interconnector 5.3, the draining gas is not distributed/recovered on the metal grid 14.

(90) The hydrogen produced SH.sub.2(1) by the steam electrolysis at the cell C1 is thus recovered in the third 63, 73, 83 ports of the interconnector 5.1.

(91) The heat-exchange gas SH.sub.2(2) having circulated for the purposes of thermal management at the metal grid 14 is separately recovered in the fourth 64, 84 ports of the end metal sheets and the first port 71 of the interconnector 5.2.

(92) Simultaneously, the oxygen O.sub.2 produced S(O.sub.2) is recovered in the sixth 66, 76, 86 ports of the three metal sheets 8 of each interconnector 5.1, 5.2.

(93) The supply of the steam and the recovery of the hydrogen produced and also the supply of draining gas and the recovery of oxygen produced, shown in FIGS. 6A to 6C, constitute a co-current circulation of fuel/heat-exchange gas of a cell C1 relative to the adjacent metal grid 14, and a cross-current circulation with the shared circulation of draining gas/oxygen produced.

(94) With the two types of interconnectors 5.1, 5.2, it is thus possible to produce, as a variant, a counter-current circulation of fuel/heat-exchange gas of a cell C1 relative to the adjacent metal grid 14, and a cross-current circulation with the circulation of draining gas/oxygen produced.

(95) The three flat metal sheets 6, 7, 8 constituting each interconnector 5.1, 5.2, 5.3 according to the invention are thin flat metal sheets, pierced and assembled with one another by welding. The thin metal sheets are preferably metal sheets less than 3 mm thick, typically with a thickness of the order of 0.2 mm. All the welds between metal sheets produced upon manufacture, outside of any operation of the electrolyzer, may advantageously be produced according to a transmission laser technique, which is possible due to the small thickness of the thin metal sheets, typically of the order of 0.2 mm.

(96) All the metal sheets are advantageously made of ferritic steel with approximately 20% chromium, preferably made of CROFER 22APU or FT18TNb, based on nickel of Inconel 600 or Haynes type in thicknesses typically of between 0.1 and 1 mm.

(97) Assembly by weld lines is around the ports between flat metal sheets 6, 7, 8 guarantees good leaktightness during operation of the electrolyzer between the steam EH.sub.2(1) conveyed to the interconnectors 5.1 as fuel, the heat-exchange gas EH.sub.2(2) conveyed to the interconnectors 5.2, 5.3 as thermal management, the hydrogen SH.sub.2(1) recovered at the interconnectors 5.1, the heat-exchange gas SH.sub.2(2) recovered at the interconnectors 5.2, the draining gas conveyed E(O.sub.2) and the oxygen S(O.sub.2) recovered. The weld lines are illustrated in FIGS. 10A to 10C.

(98) As illustrated on all the FIGS. 5 to 8, the three metal sheets 6, 7, 8 are pierced at their periphery by additional ports 69, 79, 89 suitable for accommodating fixing rods. These fixing rods make it possible to apply a retention force to the stack of the different components both of the electrochemical stages and of the thermal regulation stages of the electrolysis reactor.

(99) Other variants and improvements may be envisaged within the context of the invention.

(100) Thus, if, in the illustrated embodiment, the heat-exchange gas is of the steam with hydrogen type, it is equally possible to envisage that the draining gas is also the heat-exchange gas. More generally, the heat-exchange gas may be any gas, with the proviso that it is suited to the material(s) of the contact elements 14, that is to say that it does not oxidize the latter.

(101) It could also be possible to use, to produce a dedicated interconnector, to laminate and to assemble three flat metal sheets such as those 6, 7, 8 illustrated, but with the proviso of removing the ports 67, 68 of the interconnector 5.2 intended for the supply of the steam/hydrogen and the recovery of the hydrogen produced, and of retaining 87 and 88 on the interconnector 5.3 at a thermal regulation stage. According to this variant, thermal regulation would be carried out by the draining gas (or oxidizing gas in SOFC cell). In this case, the metal grid 14 is either a grid resistant to oxidation or an electrical contact provided directly by welding two successive interconnectors 5.2, 5.3 to one another. The welds between these two interconnectors 5.2, 5.3 must then provide leaktightness and the passage of the current.

(102) The electrochemical stages and the thermal regulation stages may be in parallel if the manifolds for supplying/recovering the gases remain independent or in series if they are connected to one another outside the stack.

(103) Connecting in series between electrochemical stages and thermal regulation stages makes it possible to effectively preheat the steam intended for the electrolysis of the water before its entry onto the cathodes of the electrolysis cells.