High-temperature, low-temperature—gradient methods for (CO-)electrolysis of water (SOEC) or for producing electricity within a reactor or fuel-cell stack (SOFC) respectively

Abstract

The invention essentially consists in supplying fuel (either steam or a mixture of steam with CO2 or H2 or CH4) to distinct zones of a cell or a group of stacked cells and of an adjacent cell or group of adjacent stacked cells within a given (co-)electrolysis reactor or a SOFC fuel-cell stack.

Claims

1. A method for high-temperature electrolysis of steam, or for co-electrolysis of steam and of carbon dioxide, implemented in a reactor comprising: a stack of individual electrolysis cells of a solid oxide type, each comprising a cathode, an anode and an electrolyte inserted between the cathode and the anode, and a plurality of electrical and fluid interconnectors, each arranged between two adjacent individual electrolysis cells with one face thereof in electrical contact with the anode of one of the two adjacent individual electrolysis cells and the other face thereof in electrical contact with the cathode of the other of the two adjacent individual electrolysis cells, the method comprising: supplying a first zone of each electrical and fluid interconnector of a first group with steam or with a mixture of steam and of carbon dioxide, and distributing it to a cathode of each individual electrolysis cell of the first group, then recovering hydrogen produced or a synthesis gas, which is a mixture of carbon monoxide and of hydrogen in a second zone of the each electrical and fluid interconnector of the first group, and supplying a first zone of each electrical and fluid interconnector of a second group, at least one of which is adjacent to the electrical and fluid interconnector of the first group, with steam or with a mixture of steam and of carbon dioxide, and distributing it to a cathode of each individual electrolysis cell of the second group, at least one of which is adjacent to the electrolysis cell of the first group, then recovering hydrogen produced or a synthesis gas, which is a mixture of carbon monoxide and of hydrogen in a second zone of the each electrical and fluid interconnector of the second group, the first and second zones of the electrical and fluid interconnectors of the second group not being located vertically in line respectively with the first and second zones of the electrical and fluid interconnectors of the first, group, wherein, within the stack, the supplying and a circulation respectively to the electrical and fluid interconnectors and to the electrolysis cells of the first group are carried out independently relative to the supplying and a circulation respectively to the electrical and fluid interconnectors and to the electrolysis cells of the second group.

2. The method of claim 1, wherein the first and second zones of the electrical and fluid interconnectors of the first and second groups are arranged such that the distributing the steam or of the mixture of steam and of carbon dioxide to the cathode of the electrolysis cells of the first group is carried out in co-current to the to the electrolysis cells of the second group.

3. The method of claim 1, wherein the first and second zones of the first and second groups of the electrical and fluid interconnectors are arranged such that the distributing the steam or of the mixture of steam and of carbon dioxide to the cathode of the electrolysis cells of the first group is carried out in counter-current to the distributing to the electrolysis cells of the second group.

4. The method of claim 1, the method further comprising: supplying a third zone of the each electrical and fluid interconnector of the first group with a draining gas, and distributing it to the anode of the each electrolysis cell of the first group, then recovering oxygen produced and, where appropriate, the draining gas in a fourth zone of the each electrical and fluid interconnector of the first group, and supplying a third zone of the each electrical and fluid interconnector of the second group with a draining gas, and distributing it to the anode of the each electrolysis cell of the second group, then recovering oxygen produced and, where appropriate, the draining gas in a fourth zone of the each electrical and fluid interconnector of the second group, the third and fourth zones of the electrical and fluid interconnectors of the second group being located vertically in line respectively with the third and fourth zones of the electrical and fluid interconnectors of the first group, so as to have a supply of draining gas and a recovery of oxygen produced which are common to the first and second groups.

5. The method of claim 1, the method further comprising: supplying a third zone of the each electrical and fluid interconnector of the first group with a draining gas, and distributing it to the anode of the each electrolysis cell f the first group, then recovering oxygen produced and, where appropriate, the draining gas in a fourth zone of the each electrical and fluid interconnector of the first group, and supplying a third zone of the each electrical and fluid interconnector of the second group with a draining gas, and distributing it to the anode of the each electrolysis cell of the second group, then recovering oxygen produced and, where appropriate, the draining gas in a fourth zone of the each electrical and fluid interconnector of the second group, the third and fourth zones of the electrical and fluid interconnectors of the second group not being located vertically in line respectively with the third and fourth zones of the electrical and fluid interconnectors of the first group, so as to have a supply of draining gas and a recovery of oxygen produced which are separate between the first group and the second group.

6. The method of claim 5, wherein the third and fourth zones of the electrical and fluid interconnectors of the first and second groups are arranged such that the distributing the draining gas and of the oxygen produced by electrolysis at the anode of the electrolysis cells of the first group is carried out in counter-current to the distributing the electrolysis cells of the second group.

7. A method for producing electricity a high temperature, implemented in a solid oxide fuel cell comprising: a stack of individual electrochemical cells of an SOFC type, each comprising a cathode, an anode and an electrolyte inserted between the cathode and the anode, and a plurality of electrical and fluid interconnectors, each arranged between two adjacent individual electrochemical cells with one face thereof in electrical contact with the anode of one of the two adjacent individual electrochemical cells and the other face thereof in electrical contact with the cathode of the other of the two adjacent individual electrochemical cells, the method comprising: supplying a first zone of each electrical and fluid interconnector of a first group with fuel, and distributing it to an anode of each individual electrochemical cell of the first group, then recovering surplus fuel and water produced in a second zone of the each electrical and fluid interconnector of the first group, and supplying a first zone of each electrical and fluid interconnector of a second group, at least one of which is adjacent to the each electrical and fluid interconnector of the first group, with fuel, and distributing it to an anode of each individual electrochemical cell of the second group, at least one of which is adjacent to the electrochemical cell of the first group, then recovering surplus fuel and ater produced in a second zone of the each electrical and fluid interconnector of the second group, the first and second zones of the electrical and fluid interconnectors of the second group not being located vertically in line respectively with the first and second zones of the electrical and fluid interconnectors of the first group, wherein, within the stack, the supplying and a circulation respectively to the electrical and fluid interconnectors and to the electrochemical cells of the first group are carried out independently relative to the supplying and circulation respectively to the electrical and fluid interconnectors and to the electrochemical cells of the second group.

8. The method of claim 7, wherein the first and second zones of the electrical and fluid interconnectors of the first and second groups are arranged such that the distributing the fuel to the anode of the electrochemical cells of the first group is carried out in co-current to the distributing to the electrochemical cells of the second group.

9. The method of claim 7, wherein the first and second zones of the first and second groups of the electrical and fluid interconnectors are arranged such that the distributing the fuel to the anode of the electrochemical cells of the first group is carried out in counter-current to the distributing to the electrochemical cells of the second group.

10. The method of claim 7, the method further comprising: supplying a third zone of the each electrical and fluid interconnector of the first group with an oxidizer, and distributing it to the cathode of the each, electro chemical cell of the first group, then recovering surplus oxidizer in a fourth zone of the each electrical and fluid interconnector of the first group, and supplying a third zone of the each electrical and fluid interconnector of the second group with an oxidizer such, and distributing it to the cathode of the each electrochemical cell of the second group, then recovering the surplus oxidizer in a fourth zone of the each electrical and fluid interconnector of the second group, the third and fourth zones of electrical and fluid interconnectors of the second group being located vertically in line respectively with the third and fourth zones of electrical and fluid of the first group interconnectors, so as to have a supply of oxidizer and a recovery of surplus oxidizer which are con on to the first and second groups.

11. The method of claim 7, the method further comprising: supplying a third zone of the each electrical and fluid interconnector of the first group with an oxidizer, and distributing it to the cathode of the each electrochemical cell of the first group, there recovering surplus oxidizer in a fourth zone of the each electrical and fluid interconnector of the first group, and supplying a third zone of the each electrical and fluid interconnector of the second group with an oxidizer, and distributing it to the cathode of the each electrochemical cell of the second group, then recovering surplus oxidizer in a fourth zone of the each electrical and fluid interconnector of the second group, the third and fourth zones of electrical and fluid interconnectors of the second group not being located vertically in line respectively with the third and fourth zones of electrical and fluid interconnectors of the first group, so as to have a supply of oxidizer and a recovery of surplus oxidizer which are separate between the first group and the second group.

12. The method of claim 11, wherein the third and fourth zones of electrical and fluid interconnectors of the first and second group are arranged such that the distributing the oxidizer to the cathode of the electrochemical cells of the first group is carried out in counter-current to the distributing the electrochemical cells of the second group.

13. The method of claim 7, wherein the fuel is hydrogen, methane or both hydrogen and methane.

14. The method of claim 1, wherein supplies of gases in the first zone of the electrical and fluid interconnectors of the first group is connected in series to supplies of gases in the first zone of the electrical and fluid interconnectors of the second group.

15. The method of claim 14, wherein the gases are enriched in a fuel and/or in an oxidizer between an outlet of the first group and an inlet of the second group, or vice-versa.

16. The method of claim 14, wherein the electrolysis cells of different sizes between the first and the second groups are used, so that all the electrolysis cells are at the same voltage with different fuel compositions.

17. The method of claim 1, wherein supplies of gases in the first zone of the electrical and fluid interconnector of the first group is in parallel to supplies of gases in the first zone the electrical and fluid interconnector of the second group.

18. The method of claim 17, wherein the first and second group supplied with same compositions and same flow rates of gas.

19. The method of claim 17, wherein the first and the second group are supplied with different compositions of methane or hydrogen so as to have different reforming between the first and the second groups.

20. The method of claim 7, wherein wherein supplies of gases in the first zone of the electrical and fluid interconnector of the first group is in parallel to supplies of gases in the first zone of the electrical and fluid interconnector of the second group, and the first and the second group are supplied with a same H.sub.2O/CO.sub.2/CO ratio.

21. The method claim 14, wherein, in operation, the supplies in series are changed into supplies in parallel, and wherein flow rates and compositions are simultaneously made different between the first and the second groups so as to manage a premature degradation of the electrolysis cells of one of the first and the second groups.

Description

DETAILED DESCRIPTION

(1) Other advantages and features of the invention will become more clearly apparent on reading the detailed description of examples of implementation of the invention, given by way of non-limiting illustration 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 sectional view of an electrolysis reactor implementing the method for high-temperature electrolysis according to one mode of the invention,

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

(6) FIG. 5 is an exploded view of a part of an electrolysis reactor according to the invention with interconnectors enabling independent supply and circulation of steam in counter-current from one electrolysis cell relative to the adjacent cell,

(7) FIGS. 6A and 6B are exploded views of two interconnectors according to the invention which enable a supply/recovery of the steam and of the hydrogen produced, separate and in co-current from one electrolysis cell to an adjacent cell, and a supply/recovery of the draining gas and of the oxygen produced, common between the two adjacent cells, the figures showing the supply, distribution and recovery of the steam and of the hydrogen produced,

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

(9) FIGS. 7A and 7B are exploded views of two interconnectors according to the invention which enable a supply/recovery of the steam and of the hydrogen produced, separate and in counter-current from one electrolysis cell to an adjacent cell, and a supply/recovery of the draining gas and of the oxygen produced, common between the two adjacent cells, the figures showing the supply, distribution and recovery of the steam and of the hydrogen produced,

(10) FIGS. 8A and 8B are exploded views of two interconnectors according to the invention which enable a supply/recovery of the steam and of the hydrogen produced, separate and in counter-current from one electrolysis cell to an adjacent cell, and a supply/recovery of the draining gas and of the oxygen produced, also separate and in counter-current from one electrolysis cell to an adjacent cell, the figures showing the supply, distribution and recovery of the steam and of the hydrogen produced,

(11) FIGS. 9A and 9B are identical, respectively, to FIGS. 8A and 8B, but show the supply, distribution and recovery of the draining gas and of the oxygen produced,

(12) FIG. 10 is a perspective view of an interconnector according to FIGS. 7A and 7B,

(13) FIG. 10A is a front view of an end metal sheet of an interconnector according to FIG. 7A, showing the supply, distribution and recovery of the steam and of the hydrogen produced,

(14) FIG. 10B is a front view of an end metal sheet of an interconnector according to FIG. 7A, showing the supply, distribution and recovery of the steam and of the hydrogen produced,

(15) FIG. 10C is a front view of an end metal sheet of an interconnector according to FIG. 7B, showing the supply, distribution and recovery of the draining gas and of the oxygen produced,

(16) FIGS. 11A and 11B are detail views of a part of an interconnector according to the invention.

(17) It is specified here that, in all of FIGS. 1 to 11B, the symbols and arrows of supply firstly 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.

(18) It is also specified that, throughout the application, the terms above, below, vertically in line with, vertical, lower, upper, bottom, top, below and above should be understood with reference to an HTE reactor or an SOFC cell in the vertical configuration in operation, that is to say with the planes of interconnectors and electrochemical cells being horizontal.

(19) It is finally specified that all the electrolyzers described are of solid oxide type (SOEC, acronym for Solid Oxide Electrolysis Cell) operating at high temperature. The high operating temperature of an electrolyzes (electrolysis reactor) is typically between 600 C. and 950 C.

(20) 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.

(21) TABLE-US-00001 TABLE Electrolysis cell Unit Value Cathode 2 Constituent material NiYSZ Thickness m 315 Thermal conductivity Wm.sup.1 K.sup.1 13.1 Electrical conductivity .sup.1 m.sup.1 10.sup.5.sup. Porosity 0.37 Permeability m.sup.2 10.sup.13 Tortuosity 4.sup. Current density A .Math. m.sup.2 5300 Anode 4 Constituent material LSM Thickness m 20 Thermal conductivity Wm.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.sup. 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

(22) FIGS. 1 and 2 have already been described in detail in the preamble. They are therefore not described hereafter.

(23) By convention, and in order to facilitate the reading of the circulations of the gases in the different figures, the following symbols are used: EH2(1): denotes the circulation, through the stack, of the steam supplying an electrolysis cell or a group of electrolysis cells C1; SH2(1): denotes the circulation, through the stack, of the hydrogen produced at an electrolysis cell or a group of electrolysis cells C1; EH2(2): denotes the circulation, through the stack, of the steam supplying an electrolysis cell or a group of electrolysis cells C2; SH2(2): denotes the circulation, through the stack, of the hydrogen produced at an electrolysis cell or a group of electrolysis cells C2; E1(O.sub.2): denotes the circulation, through the stack, of the draining gas supplying an electrolysis cell or a group of electrolysis cells C1; S1(O.sub.2): denotes the circulation, through the stack, of the oxygen produced at an electrolysis cell or a group of electrolysis cells C1; E2(O.sub.2): denotes the circulation, through the stack, of the draining gas supplying an electrolysis cell or a group of electrolysis cells C2; S2(O.sub.2): denotes the circulation, through the stack, of the oxygen produced at an electrolysis cell or a group of electrolysis cells C2.

(24) In order to improve the management of the thermal operations of the electrolysis reactor and to reduce the thermal gradients therein, the inventors of the present invention had the idea of carrying out a circulation of the fuel gas, i.e. the steam, and of the hydrogen produced within each interconnector 5.1, 5.2 of the stack, such that the distribution at a cell C1 or group of cells is separate from that at a cell C2 or adjacent group of cells.

(25) For this purpose, as illustrated in FIG. 3: steam EH2(1) is supplied in a first zone of each interconnector 5.1 (on the left in FIG. 3), and it is distributed to a cathode of the cells C1, then the hydrogen H.sub.2 produced is recovered in a second zone of the interconnectors 5.1 (on the right in FIG. 3). steam EH2(2) is supplied in a first zone of each interconnector 5.2, each adjacent to an interconnector 5.1 (on the right in FIG. 3), and it is distributed to a cathode of the cells C2, each adjacent to the cell C1, then the hydrogen H.sub.2 produced is recovered in a second zone of the interconnectors 5.2 (on the left in FIG. 3).

(26) All the first and second zones of the interconnectors 5.2 are not situated vertically in line respectively with first and second zones of the interconnectors 5.1.

(27) As illustrated in FIGS. 3 and 5, it is possible to provide for producing the interconnectors 5.1, 5.2, in order to arrange the different zones for supply and recovery of the steam and of the hydrogen produced such that their circulation at the cells C1 is in counter-current to the circulation at the cells C2. This circulation may also be in co-current, as illustrated in FIGS. 6A and 6B.

(28) The interconnectors 5.1, 5.2 may also be produced in order to arrange the different zones for supply and recovery of the draining gas and of the oxygen produced such that their circulation at the cells C1 is in co-current (FIGS. 3 and 5) to the circulation at the cells C2, or in counter-current thereto (FIG. 4).

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

(30) This electrolyzer electrolysis reactor comprises a stack of individual electrolysis cells of SOEC type (C1, C2), each 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.

(31) A fluid and electrical interconnector 5.1, 5.2 is arranged between two adjacent individual cells C1, C2, with one face thereof in electrical contact with the anode of one of the two individual cells and the other face thereof in electrical contact with the cathode of the other of the two individual cells.

(32) 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. 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 for supplying the gases in electrolysis or co-electrolysis, H.sub.2O, CO.sub.2, air, and for recovering the gases produced, H.sub.2, CO, O.sub.2 with air.

(33) The same electrical current passes through all the electrolysis cells C1 and C2.

(34) In the reactor according to the invention, all the cathode compartments 50 of the group of cells C1, in which the steam H.sub.2O supplied and the hydrogen H.sub.2 produced circulate, communicate with one another. Similarly, all the cathode compartments 50 of the group of cells C2, in which H.sub.2O/H.sub.2, also circulate, communicate with one another, but are completely isolated from the compartments 50 intended for the group of cells C1.

(35) Finally, the two simultaneous but separate electrolysis reactions both produce oxygen, which is collected by all the anode compartments 51 which communicate or do not communicate with one another. Thus, as is described in detail below, as a function of the design of the ports intended for discharging, the oxygen, it is possible to carry out a collection of oxygen which is common to all the cells or, conversely, a collection which is separate from one cell C1 relative to the other, adjacent cell C2.

(36) According to the invention, an interconnector 5.1 is different from an adjacent interconnector 5.2 in order to be able to carry out a supply of steam and a recovery of hydrogen produced at a cell C1 which is distinct from that carried out at a cell C2.

(37) Thus, as illustrated in FIG. 5, the circulation of the hydrogen/steam through the stack and at the cell C1 is separate from the circulation through the stack and at the cell C2.

(38) FIG. 6A shows an exploded view of an interconnector 5.1 according to the invention, making it possible to provide the supply of steam H.sub.2O, the circulation of steam and of the hydrogen produced at the cell C1 and also the recovery of the oxygen O.sub.2 produced within the stack of an electrolysis reactor. As described in detail below, the interconnector 5 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 cell C1.

(39) The interconnector 5.1 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.

(40) The first 6 end metal sheet is intended to come into mechanical contact with the plane of a cathode 2.1 of an 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.

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

(42) 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 8 is pierced.

(43) 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, 76; 81, 82, 83, 84, 85, 86.

(44) 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.

(45) 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.

(46) 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.

(47) 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.

(48) The second 8 end metal sheet also comprises a seventh 87 and an eighth 88 port 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.

(49) 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.

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

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

(52) FIGS. 11A and 11B 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. 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, CO.sub.2, air) over the electrolysis cell, and by virtue of these comb forms for the widened slits 73, 76 a recovery is obtained of the gas produced (H.sub.2, CO, O.sub.2). These homogeneous distributions or recoveries or, in other words, these distributions or recoveries which are uniform in terms of flow rate over the surface of the cell are shown in the different FIGS. 6A to 10C in the form of small arrows spaced apart from one another.

(53) In order to produce the interconnector 5.2 represented in FIG. 6B, which is intended for steam electrolysis at the cell C2, the same three flat metal sheets 6, 7, 8 are used as those used for producing the interconnector 5.2, but the central metal sheet 7 is merely turned upside down before its lamination and assembly with the two end metal sheets 6, 8.

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

(55) 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 and 6B.

(56) The first 61, 71, 81 ports of the interconnector 5.1 are supplied with steam EH2(1) and simultaneously but separately the second 62, 72, 82 ports of the interconnector 5.1 are also supplied with steam EH2(2).

(57) The steam EH2(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.

(58) Similarly, the steam EH2(1) passes through the interconnector 5.2 without being distributed to the cathode 2.2 of the cell C2.

(59) The path, within an interconnector 5.1, of the steam injected and of the hydrogen produced, is illustrated schematically in FIGS. 6A, 7A and 8A.

(60) The path, within an interconnector 5.2, of the steam injected and of the hydrogen produced within an interconnector 5.2, is illustrated schematically in FIGS. 6B. 7B and 8B.

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

(62) The path of the air as draining gas injected and of the oxygen produced within an interconnector 5 is schematically illustrated in FIG. 6C.

(63) The hydrogen produced SH2(1) by the steam electrolysis at the cell C1 is thus recovered in the third 63, 73, 83 ports of the interconnector 5.1 and in the third 63, 83 ports of the end metal sheets and the second port 72 of the interconnector 5.2.

(64) The hydrogen produced SH2(2) by the steam electrolysis at the cell C2 is recovered separately in the fourth 64, 84 ports of the end metal sheets and the first port 71 of the interconnector 5.2 and in the fourth 64, 74, 84 ports of the interconnector 5.1.

(65) 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.

(66) 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, constitutes a co-current circulation of fuel of a cell C1 relative to the other adjacent cell C2, and a cross-current circulation with the common circulation of draining gas/oxygen produced.

(67) With the two types of interconnectors 1, 5.2, it is thus possible to carry out, as a variant, a counter-current circulation of fuel of a cell C1 relative to the other adjacent cell C2, and a cross-current circulation with the common circulation of draining gas/oxygen produced (FIGS. 7A and 7B).

(68) It is thus possible to carry out a counter-current circulation of fuel of a cell C1 relative to the other adjacent cell C2, and with the circulation of draining gas/oxygen produced and separate from a cell C1 relative to the other cell C2 (FIGS. 8A and 8B). In order to carry out this separate circulation of draining gas/oxygen produced, it is then sufficient to somehow divide in two the ports 65, 75, 85 for supply of draining gas and the ports 66, 76, 86 for recovery of oxygen produced.

(69) It is also possible to carry out a separate circulation of draining gas/oxygen produced in counter-current relative to the circulations of draining gas/oxygen of a cell C1 relative to the other adjacent cell C2. Thus, as illustrated in FIG. 9A, the draining gas E1(O2) supplies the ports 65.1, 75.1, 85.1 of the interconnector 5.1 and the oxygen produced S1(O.sub.2) is recovered at the ports 66.1, 76.1, 86.1. As illustrated in FIG. 9B, the draining gas E2(O2) supplies the ports 66.2, 76.1, 86.2 of the interconnector 5.2 and the oxygen produced S2(O2) is recovered at the ports 65.2, 75.1, 85.2.

(70) FIG. 10 represents a perspective view of an interconnector 5.1 with ports 65, 75, 85 for a common circulation of draining gas and a common recovery of oxygen at the ports 66, 76, 86.

(71) The three flat metal sheets 6, 7, 8 constituting each interconnector 5.1, 5.2 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 are produced upon manufacture and 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.

(72) All the metal sheets are advantageously made of ferritic steel with approximately 20% chromium, preferably made of CROFER 22APU or FT18TNb. AISI 441, or based on nickel of Inconel 600 or Haynes type in thicknesses typically of between 0.1 and 1 mm.

(73) Assembly by weld lines 1s around the ports between flat metal sheets 6, 7, 8 guarantees good leaktightness during operation of the electrolyzer between the steam EH2(1) conveyed to the interconnectors 5.1, the steam EH2(2) conveyed to the interconnectors 5.2, the hydrogen SH2(1) recovered at the interconnectors 5.1, the hydrogen SH2(2) recovered at the interconnectors 5.2, the draining gas conveyed E(O2) and the oxygen S(O2) recovered. The weld lines are illustrated in FIGS. 10A to 10C.

(74) As illustrated on all the FIGS. 5 to 10C, 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 of the electrolysis reactor.

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

(76) If, in the embodiments illustrated, there is alternation of a cell C1 with a cell C2 and thus of an interconnector 5.1 with an interconnector 5.2, it is also possible to provide, within the context of the invention, for a certain number of cells C1 and interconnectors 5.1 to be stacked and separated from the other number of these cells C1 and interconnectors 5.1 by at least one cell C2 and an interconnector C2. It is thus possible to have overlapping of the first group of cells C1 and interconnectors 5.1 with the second group of cells C2 and interconnectors, with one-by-one alternation or alternation in bundles.

(77) It goes without saying that the invention encompasses the possibility of having n groups of cells C1, C2, . . . Cn and interconnectors 5.1, 5.2, . . . 5n within the same stack with supply and recovery manifolds which are independent of one another. The two cells C1 and C2 may be supplied in parallel if the manifolds remain independent upstream and downstream of the stack, or in series if they are connected to one another outside the stack. Supplementation with fuel and/or with draining gas may then be carried out between, the two cells C1, C2 in series.

(78) As illustrated, cells of the same nature, of solid oxides type, are stacked for all the cells C1, C2. The number of cells per group and their respective size may be different depending on the application: the current is identical for all the cells, but the choice to be at the same voltage or not for different gas conditions may determine the size ratio of cells C1 and cells C2 and also the number thereof.