STAND-ALONE SYSTEM FOR CLAMPING A HIGH-TEMPERATURE SOEC/SOFC STACK

Abstract

The main subject of the invention is a system (10) for clamping a high-temperature SOEC/SOFC stack (11), characterised in that it includes: an upper clamping plate (12) and a lower clamping plate (13) between which the stack (11) is intended to be clamped, each plate including at least one clamping orifice (14); at least one clamping rod (15) intended to extend through clamping orifices (14) in the upper and lower clamping plates (12, 13) in order to allow them to be assembled; clamping means (16, 17, 18, 20, 21) level with each clamping orifice (14), which means are intended to interact with said at least one clamping rod (15); and at least one electrically insulating plate (19) that is intended to be located between the stack (11) and at least one of the upper and lower clamping plates (12, 13).

Claims

1-26. (canceled)

27. An assembly, comprising: an SOEC/SOFC type solid oxide stack operating at high temperature, comprising: a plurality of electrochemical cells each including a cathode, an anode, and an electrolyte intercalated between the cathode and the anode, a plurality of intermediate interconnectors each formed between two adjacent electrochemical cells, an upper terminal plate and a lower terminal plate, between which the plurality of electrochemical cells and the plurality of intermediate interconnectors are clamped; a standalone clamping system for the SOEC/SOFC type solid oxide stack operating at high temperature, comprising: an upper clamping plate and a lower clamping plate between which the SOEC/SOFC type solid oxide stack is clamped, each plate comprising at least one clamping orifice, each of the upper and lower terminal plates being in contact with one of the upper and lower clamping plates or in contact with at least one electrical insulation plate of the clamping system located between the SOEC/SOFC type solid oxide stack and at least one of the upper and lower clamping plates, at least one clamping rod that extends through a clamping orifice in the upper clamping plate and through a corresponding clamping orifice in the lower clamping plate to enable assembly of the upper and the lower clamping plates to each other, clamping means at each clamping orifice of the upper and lower clamping plates configured to cooperate with the at least one clamping rod to assemble the upper and lower clamping plates to each other, the clamping means comprising at least one first clamping nut associated with at least one clamping washer at each clamping orifice in one among the upper and lower clamping plates, configured to cooperate with the at least one clamping rod inserted through the clamping orifice; the at least one clamping rod and the at least one first clamping nut being made from a super alloy based on nickel, the at least one clamping washer being made of refractory austenitic steel and the upper clamping plate and the lower clamping plate being made of austenitic refractory steel.

28. An assembly according to claim 27, wherein difference in expansion between the at least clamping rod and the SOEC/SOFC type solid oxide stack is compensated by expansion of the lower and upper clamping plates and the at least clamping washer.

29. An assembly according to claim 27, wherein the upper clamping plate and the lower clamping plate each have a thickness of between 20 and 30 mm.

30. An assembly according to claim 27, wherein the at least one clamping rod is threaded, and wherein the clamping means comprises at least one second clamping nut at each clamping orifice in one of the upper and lower clamping plates, configured to cooperate with the at least one clamping rod inserted through the clamping orifice, and comprises the at least one first clamping nut associated with the at least one clamping washer at each clamping orifice in the other among the upper and lower clamping plates, configured to cooperate with the at least one clamping rod inserted through the clamping orifice, the at least one clamping washer being located between the at least one first clamping nut and the other among the upper and lower clamping plates.

31. An assembly according to claim 27, wherein each of the upper and lower clamping plates comprises at least two clamping orifices, and further comprising: at least two clamping rods, each of which extends through a clamping orifice in the upper clamping plate and through a corresponding clamping orifice in the lower clamping plate to enable assembly of the upper and lower plates to each other; clamping means at each clamping orifice in the upper and lower clamping plates configured to cooperate with the at least two clamping rods to assemble the upper and lower clamping plates to each other; the at least two clamping rods being threaded, and the clamping means comprising a second clamping nut at each clamping orifice in one of the upper and lower clamping plates, configured to cooperate with the clamping rod inserted through the clamping orifice, and comprising a first clamping nut associated with a clamping washer at each clamping orifice in the other among the upper and lower clamping plates, configured to cooperate with the clamping rod inserted through the clamping orifice, the clamping washer being located between the first clamping nut and the other among the upper and lower clamping plates.

32. An assembly according to claim 27, wherein the at least one electrical insulation plate is made of mica.

33. An assembly according to claim 27, wherein the SOEC/SOFC type solid oxide stack further comprises a first contact layer between the upper terminal plate and the assembly composed of the electrochemical cells and the intermediate interconnectors, and a second contact layer between the lower terminal plate and the assembly composed of the electrochemical cells and the intermediate interconnectors.

34. An assembly according to claim 33, wherein one of the first and second contact layers comprises a ceramic oxide layer, and wherein the other among the first and second contact layers comprises a layer made of nickel.

35. An assembly according to any claim 27, wherein the SOEC/SOFC type solid oxide stack further comprises at least two guide columns extending through guide orifices formed in at least the upper terminal plate, the lower terminal plate, the intermediate interconnectors, and the upper clamping plate, and configured to guide the SOEC/SOFC type solid oxide stack in compression during its fabrication.

36. A method for fabrication of an SOEC/SOFC type solid oxide stack operating at high temperature of an assembly according to claim 27, making use of a clamping system of the assembly, the method comprising fabrication by external clamping of the SOEC/SOFC type solid oxide stack through a clamping system.

37. A method according to claim 36, further comprising, prior to the fabrication by external clamping, positioning the SOEC/SOFC type solid oxide stack between the upper and lower clamping plates of the clamping system with presence of the at least one electrical insulation plate located between the SOEC/SOFC type solid oxide stack and at least one of the upper and lower clamping plates.

38. A method according to claim 36, wherein the fabrication by external clamping includes compression of the SOEC/SOFC type solid oxide stack, when temperature increases from about 20 C. to a temperature of more than 800 C.

39. A method according to claim 38, wherein the compression applied during the fabrication by clamping is achieved by an external load.

40. A method according to claim 38, wherein the compression applied during the fabrication by external clamping is a distributed weight equal to between 2 and 2.5 kg/cm.sup.2 of electrochemical cell.

41. A method according to claim 38, wherein the at least one clamping rod in the clamping system is threaded, and wherein the clamping means comprises at least one second clamping nut at each clamping orifice in one of the upper and lower clamping plates, configured to cooperate with the at least one clamping rod inserted through the clamping orifice, and comprising at least one first clamping nut associated with at least one clamping washer at each clamping orifice in the other among the upper and lower clamping plates, configured to cooperate with the at least one clamping rod inserted through the clamping orifice, the at least one clamping washer being located between the at least one first clamping nut and the other among the upper and lower clamping plates, and wherein, after cooling to a temperature of about 20 C. during the compression of the SOEC/SOFC solid oxide stack, the at least one threaded rod, the at least one second clamping nut, the at least one first clamping nut, and the at least one clamping washer are put into place on the clamping system, the at least one first and one second clamping nuts being brought into contact without additional clamping.

42. A method according to claim 41, wherein after placement of the at least one threaded clamping rod, the at least one second clamping nut, the at least one first clamping nut, and the at least one clamping washer on the clamping system, compression of the SOEC/SOFC type solid oxide stack is interrupted, by removing the external load such that the force previously applied by clamping is transferred onto the existing installed clamping means.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0095] The invention will be better understood after reading the following detailed description of non-limitative example embodiments of the invention, and an examination of the diagrammatic and partial figures in the appended drawing on which:

[0096] FIG. 1 is a diagrammatic view showing the operating principle of a high temperature solid oxide electrolyser (SOEC).

[0097] FIG. 2 is a diagrammatic exploded view of a part of a high temperature solid oxide electrolyser (SOEC) comprising interconnectors according to prior art.

[0098] FIG. 3 is a partial perspective exploded view representing an example of an assembly comprising a high temperature SOEC/SOFC type solid oxide stack and a clamping system for this stack according to the invention, and

[0099] FIGS. 4 to 7 are partial perspective exploded views, each representing variant embodiments of an assembly comprising a high temperature SOEC/SOFC type solid oxide stack and a clamping system for this stack according to the invention.

[0100] In all these figures, identical references may denote identical or similar elements.

[0101] Furthermore, the different parts shown on the figures are not necessarily all at the same scale, to make the figures more easily understandable.

DETAILED PRESENTATION OF PARTICULAR EMBODIMENTS

[0102] FIGS. 1 and 2 have already been described above in the part dealing with the state of prior art and the technical context of the invention. Note that for these FIGS. 1 and 2, the symbols and the arrows indicating the supply of steam H.sub.2O, the distribution and recovery of dihydrogen H.sub.2, oxygen O.sub.2, air and electrical current, are shown for reasons of clarity and precision, to illustrate the operation of the devices represented.

[0103] Note also that all the constituents (anode/electrolyte/cathode) of a given electrochemical cell are preferably ceramics. Furthermore, the operating temperature of a high temperature SOEC/SOFC type stack is typically between 600 and 1000 C.

[0104] Furthermore, the terms upper and lower as used herein should be understood in the sense of the normal orientation of an SOEC/SOFC type stack and/or a clamping system according to the invention when in their usage configuration.

[0105] With reference to FIG. 3 a partial perspective exploded view represents an example of an assembly 30 comprising a high temperature SOEC/SOFC type solid oxide stack 11 and a self-contained clamping system 10 for this stack 11 according to the invention.

[0106] According to the invention, the clamping system 10 comprises firstly an upper clamping plate 12 and a lower clamping plate 13, between which the SOEC/SOFC type solid oxide stack is clamped.

[0107] Each upper clamping plate 12 and lower clamping plate 13 comprises a plurality of clamping orifices 14.

[0108] Furthermore; the clamping system 10 comprises four clamping rods 15, each extending through a clamping orifice 14 in the upper clamping plate 12 and through a corresponding clamping orifice 14 in the lower clamping plate 13 to enable assembly of the upper clamping plate 12 and the lower clamping plate 13 to each other.

[0109] Advantageously, the clamping rods 15 are threaded and have a cylindrical shape with a diameter greater than or equal to 16 mm.

[0110] Furthermore; the clamping system 10 also comprises clamping means 16, 17, 18 at each clamping orifice 14 in the upper clamping plate 12 and the lower clamping plate 13 that cooperate with the clamping rods 15 to enable assembly of the upper clamping plate 12 and the lower clamping plate 13 together.

[0111] In this example in FIG. 3, these clamping means comprise a second clamping nut 18 cooperating with the corresponding clamping rod 15 inserted through the clamping orifice 14, at each clamping orifice 14 in the lower clamping plate 14. Furthermore, the clamping means comprise a first clamping nut 16 associated with a clamping washer 17, at each clamping orifice 14 in the upper clamping plate 12, cooperating with the corresponding clamping rod 15 inserted through the clamping orifice 14. As can be seen on this FIG. 3, the clamping washer 17 is located between the first clamping nut 16 and the upper clamping plate 12.

[0112] Advantageously, the upper clamping plate 12 and the lower clamping plate 13 are made of AISI 310 type austenitic refractory steel. Each is of the order of 25 mm thick.

[0113] Furthermore, the clamping rods 15 and the first 16 and second 18 clamping nuts are advantageously made of an Inconel 625 type nickel-based super alloy. In this way, it is possible to guarantee elastic behaviour and therefore avoid any creep or relaxation despite the envisaged temperatures.

[0114] The clamping washers 17 are made of AISI 310 type austenitic refractory steel. The thickness of the clamping washers 17 can be adjusted as a function of the number of electrochemical cells 31 present in the SOEC/SOFC type solid oxide stack 11. Advantageously, the invention can compensate for the difference in expansion between the clamping rods 15 made of an Inconel 625 type nickel-based super alloy and the SOEC/SOFC type solid oxide stack 11 by the large expansion of the lower 12 and upper 13 clamping plates and the clamping washers 17 made of AISI 310 type austenitic refractory steel.

[0115] Furthermore, in this example in FIG. 3, the clamping system according to the invention also comprises an electrical insulation plate 18 between the SOEC/SOFC type solid oxide stack 11 and the upper clamping plate 12.

[0116] This electrical insulation plate 19 is advantageously made of mica. This electrical insulation plate 19 acts as an electrical insulating packing between the SOEC/SOFC type solid oxide stack 11 and the upper clamping plate. If this plate is not present and since the clamping system 10 is preferably metallic, it would cause a global short circuit between the top and the bottom of the stack 11.

[0117] Furthermore, the SOEC/SOFC type solid oxide stack 11 comprises firstly a plurality of electrochemical cells 31 each composed of a cathode, an anode and an electrolyte intercalated between the cathode and the anode, and a plurality of intermediate interconnectors 32 each arranged between two adjacent electrochemical cells 31.

[0118] Furthermore, the stack 11 also comprises an upper terminal plate 33 and a lower terminal plate 34, between which the plurality of electrochemical cells 31 and the plurality of intermediate interconnectors 32 are clamped.

[0119] In this example in FIG. 3, the upper terminal plate 33 is in contact with the electrical insulation plate 19 of the clamping system 10, while the lower terminal plate 34 is in contact with the lower clamping plate 13 of the clamping system 10.

[0120] Not that the thickness of each intermediate interconnector 32 is preferably small, particularly less than or equal to 1 mm.

[0121] Furthermore, the upper terminal plate 33 and the lower terminal plate 34 are each of the order of 10 mm thick.

[0122] Furthermore, four metallic inlet/outlet tubes 35 pass through each lower terminal plate 34 to carry the gases produced.

[0123] Furthermore, a layer forming insulating packing 36 is located around each electrochemical cell 31 and between each adjacent intermediate interconnector 32. This insulating packing 36 can advantageously help to centre each electrochemical cell 31 and provide electrical insulation between intermediate interconnectors 32. It is preferably made of mica. It can also provide a support for seals, particularly made of glass.

[0124] As shown, the SOEC/SOFC type solid oxide stack 11 also comprises a first contact layer 37 between the upper terminal plate 33 and the assembly formed by the electrochemical cells 31 and the intermediate interconnectors 32, and a second contact layer 38 between the lower terminal plate 34 and the assembly formed by the electrochemical cells 31 and the intermediate interconnectors 32. More precisely, although not shown, the stack 11 comprises a first contact layer 37 between each H.sub.2 electrode of the electrochemical cells 31 and each intermediate connector 32 or upper terminal plate 33, and comprises a second contact layer 38 between each O.sub.2 electrode of the electrochemical cells 31 and each intermediate connector 32 or lower terminal plate 34.

[0125] The first 37 and second 38 contact layers can advantageously improve the passage of electrical current between the intermediate interconnectors 32 and the electrochemical cells 31.

[0126] In this example in FIG. 3, the first contact layer 37 is formed from a nickel grating while the second contact layer 38 is a Lanthanum Strontium Manganite (LSM) type ceramic oxide layer.

[0127] Furthermore, the SOEC/SOFC type solid oxide stack 11 also comprises two guide columns 39 extending through guide orifices 40 formed in the upper terminal plate 33, the lower terminal plate 34, the intermediate interconnectors 32, the insulating packing 36 and the upper clamping plate 12. These guide columns 39 are advantageously configured to guide the SOEC/SOFC type solid oxide stack 11 in compression, by compression during fabrication.

[0128] Moreover, it should be noted that that the set of steel materials used in the stack 11 are ferritic steels, particularly of the Crofer, AISI 441 and/or AISI 430 type, principally to adapt coefficients of expansion between glass seals, cells 31 and interconnectors 32.

[0129] It is also worth noting for guidance, the average order of magnitude of coefficients of expansion a used between 20 and 800 C. for the various materials mentioned above, namely: [0130] ferritic steel: =1210.sup.6, [0131] nickel and Inconel 625 grating: =1610.sup.6, [0132] AISI 310 type austenitic steel: =1810.sup.6, and [0133] lanthanum strontium manganite (LSM): =1210.sup.6.

[0134] Depending on the thicknesses of each of the components of the stack 11, the thickness of the clamping washers 17 made of AISI 310 steel is chosen so as to guarantee that all expansions of parts located between the clamping nuts 16 and 18, corresponding to the sum of the (thickness) product for each component is equal to or slightly more than the expansion of the threaded clamping rods 15. This guarantees that initial clamping will be maintained regardless of the temperature variation, or even provide slight additional clamping as the temperature increases from 20 to 800 C. Thus, for a conclusive test result of the electrical contact and leak tightness of an assembly 30 according to the invention, clamping washers 17 made of AISI 310 are about 10 mm thick for 25 electrochemical cells 31.

[0135] Due to the invention, it is thus possible to manage clamping of the stack 11 and to hold its temperature without any transfer into a cold zone. The choice of materials and thicknesses of components of the clamping system 10 can hold this clamping force regardless of the temperature, despite differential expansions of each of the components of the stack 11. Furthermore, the sizing of the clamping system 10 makes it possible for all strains to remain elastic to guarantee possible temperature cycles. Moreover, the clamping system 10 can protect the stack 11 from electrical short circuits in the remainder of an installation in which it is installed.

[0136] More specifically, the invention can advantageously obtain a self-contained clamping system 10 capable of operating over the entire temperature range from 20 to 900 C., and maintain the initial clamping applied during fabrication over the entire temperature range from 20 to 900 C. The invention can advantageously be based on compensation of the difference in expansion between the nickel-based super alloy and ferritic steel by austenitic refractory steel. It does not use a transfer to a cold zone, guaranteeing a compact stack size without a temperature gradient to be maintained. Furthermore, the invention enables displacement of the stacks 11 obtained from one fabrication installation to another fabrication installation for their operation. The invention can thus be used to fabricate stacks 11 in the chain independently of their use. Furthermore, the clamping system 10 according to the invention is flexible, so that the number of electrochemical cells 31 in the stack 11 can be adapted by adjusting the thickness of the austenitic refractory steel clamping washers 17. Finally, the clamping system 10 according to the invention makes it possible to manage electrical insulation of the stack 11 in the case of an installation of several stacks 11 simultaneously.

[0137] Moreover, depending on the required electrical installation for the stack 11, or even the combination of several stacks 11, different configurations can be envisaged for the electrical insulation between external clamping and the stack 11.

[0138] Thus, FIGS. 4 to 7 are partial perspective exploded views, each representing variant embodiments of an assembly 30 comprising a high temperature SOEC/SOFC type solid oxide stack 11 and a clamping system 10 for this stack 11 according to the invention, with insulation of the clamping linkage.

[0139] More precisely, as can be seen on these FIGS. 4 to 7, the clamping means 16, 17, 18, 20, 21 may comprise an insulating washer 20 and an insulating tube 21 through which a corresponding threaded clamping rod 15 passes, at each clamping orifice 14 of the upper clamping plate 12 or the lower clamping plate 13 at which the second clamping nuts 18 are located, inserted through the clamping orifice 14, to enable cooperation of the assembly between the clamping rod 15 and the corresponding second clamping nut 18. The insulating tube 21 is then located between the upper clamping plate 12 or the lower clamping plate 13 and the insulating washer 20, and the insulating washer 20 is located between the insulating tube 21 and the second clamping nut 18.

[0140] In other words, the clamping systems 10 in FIGS. 4 to 7 allow for the addition of four insulating washers 20 and four insulating tubes 21 so as to enable different electrical potentials between a clamping plate 12, 13 and the threaded rods 15.

[0141] The various non-limitative configurations thus envisaged by this invention, are described in detail below. Obviously, for safety reasons, the installation in which the assembly 30 will be installed containing the clamping system 10 and the stack 11 is connected to the ground.

[0142] In the configuration described above with reference to FIG. 3, all that are considered are the four inlet/outlet tubes 35 for the gases produced, the upper clamping plate 12 and lower clamping plate 13, the lower terminal plate 3, the four clamping rods 15, the clamping washers 17 and the first 16 and second 18 clamping nuts are connected to the ground. Only the remaining part of the stack 11 is not connected to this potential and therefore requires the electrical insulation plate 19 between the upper clamping plate 12 and the upper terminal plate 33.

[0143] In the configuration in FIG. 4, unlike the configuration in FIG. 3, insulating washers 20 and insulating tubes 21 are provided at the lower clamping plate 13 between this plate and the second clamping nuts 18. Thus, this configuration consists of modifying the configuration in FIG. 3 by requiring a different potential for the upper clamping plate 12 and the clamping system 10. The four inlet/outlet tubes 35 for gases produced, the lower terminal plate 34 and the lower clamping plate 13 are then connected to the ground. The clamping rods 15, the clamping washers 17, the clamping nuts 16 and 18 and the upper clamping plate 12 can be connected to a potential different from the ground and different from the potential of the stack 11.

[0144] In the configuration in FIG. 5, unlike that in FIG. 4, the position of the insulating tubes 21, the insulating washers 20, the clamping washers 17 and the clamping nuts 16 and 18 is inverted. Thus, this configuration consists of requiring another potential for the upper clamping plate 12. The four inlet/outlet tubes 35 for gases produced, the lower terminal plate 34, the lower clamping plate 13, the clamping rods 15, the clamping washers 17 and the nuts 16 and 19 are connected to the ground. The upper clamping plate 12 can be connected to a potential different from the ground and different from the potential of the stack 11.

[0145] In the configuration in FIG. 6, unlike that in FIG. 5, an electrical insulation plate 19 is inserted between the lower clamping plate 13 and the lower terminal plate 34.

[0146] In the configuration in FIG. 7, unlike that in FIG. 4, an electrical insulation plate 19 is also inserted between the lower clamping plate 13 and the lower terminal plate 34.

[0147] Thus, these configurations in FIGS. 6 and 7 consist of wishing to completely isolate the stack 11 from the clamping system 10. There is thus an electrical insulation plate 19 between the stack 11 and each of the upper 12 and lower 13 clamping plates. If the four produced gas inlet/outlet tubes 35 are also insulated from the remaining part of the installation, the stack 11 is then said to be floating, in other words it is not connected to the ground of the installation. In these configurations in FIGS. 6 and 7, the insulating washers 20 and the insulating tubes 21 make it possible for the two clamping plates 12 and 13 to be at different potentials.

[0148] All these possible configurations also make it possible to superpose several stacks that are independent or not electrically connected. Moreover, some configurations enable an electric power supply on the nuts of the clamping rods 15, for example through the first nuts 16 on FIG. 5. The configuration in FIG. 4 also enables an electrical power supply to a second stack 11 placed on top of the first stack 11 through second nuts 18 of this first stack 11.

[0149] We will now describe an example of a method of fabricating an SOEC/SOFC type solid oxide stack 11 operating at high temperature, making use of a clamping system 10 according to the invention.

[0150] According to this method, a preliminary step before fabrication by clamping the stack 11 by means of the clamping system 10 consists of putting the stack 11 into position between the upper 12 and lower 13 clamping plates of the clamping system 10 with the presence of the electrical insulation plate(s) 19 between the stack 11 and one or two additional upper 12 and lower 13 clamping plates.

[0151] Thus, some parts of the self-contained clamping system 10 according to the invention should be put into place at the time of assembly of the stack 11, before actual fabrication. As described below, the invention aims to maintain the force applied by compression, particularly be gravity or by a ram, at the time of fabrication by the external linkage of the clamping system 10, namely the clamping rods 15, the first 16 and second 18 clamping nuts and the clamping washers 17.

[0152] The fabrication step by clamping the stack 11 then comprises a compression step of the stack 11. More precisely, the clamping applied during this fabrication step by clamping is achieved by an external load, preferably of the gravity type or using a ram.

[0153] During this compression, the two guide columns 39, preferably made of ceramic, guide the compression of the stack 11. The clamping applied during the fabrication step by clamping is for example a distributed weight equal to between 2 and 2.5 kg/(cm.sup.2 of electrochemical cell). This clamping deforms the contact layers 37 and 38, and the seals, to subsequently guarantee good electrical contact and a good seal.

[0154] After conditioning (in temperature) while clamped, preferably by gravity, the threaded clamping rods 15, the first 16 and second 18 clamping nuts and the clamping washers 17 are put into place on the clamping system 10. Note that the nuts 16 and 18 are simply brought into contact without additional clamping.

[0155] Thus, clamping by compression of the stack 11 is stopped and removed. The result is then that this same force is transferred to the linkage of the clamping system 10, neglecting the elastic elongation of the four clamping rods 15, with a diameter of about 16 mm, under 200 kg.

[0156] The stack 11 obtained can then be transferred from the fabrication installation to a functional installation, for example to produce hydrogen, synthetic gas and/or electricity depending on the mode chosen for this stack 11. All that is then necessary is to plug in the four metallic produced gas inlet/outlet tubes 35 and the current power supplies to enable operation on the functional installation, such that the clamping system 10 according to the invention is of the plug and play type.

[0157] Obviously, the invention is not limited to the example embodiments that have just been described. An expert in the subject can make various modifications to it.