ASSEMBLY CONSISTING OF A SOLID-OXIDE STACK OF THE SOEC/SOFC TYPE AND OF A COUPLING SYSTEM GASTIGHT AT HIGH TEMPERATURE WITH COUPLING FLANGE

Abstract

An assembly includes a solid-oxide stack of the SOEC/SOFC type and a system for clamping the solid-oxide stack. This assembly also comprises one system for the coupling, gastight at high temperature, including a coupling flange to enable a gas inlet and/or outlet tube to pass, at least one clamping screw, provided with a clamping head, and a seal, positioned between said at least one of the top and bottom clamping plates and against the coupling flange.

Claims

1. Assembly, including: a solid-oxide stack of the SOEC/SOFC type operating at high temperature, including: a plurality of electrochemical cells each formed by a cathode, an anode and an electrolyte interposed between the cathode and the anode, and a plurality of intermediate interconnectors each arranged between two adjacent electrochemical cells, a system for clamping the solid-oxide stack of the SOEC/SOFC type, including a top clamping plate and a bottom clamping plate, between which the solid-oxide stack of the SOEC/SOFC type is gripped, each clamping plate including at least two clamping orifices, the clamping system further including: at least two clamping rods intended to each extend through a clamping orifice of the top clamping plate and through a corresponding clamping orifice in the bottom clamping plate to enable the top and bottom clamping plates to be assembled together, clamping means at each clamping orifice of the top and bottom clamping plates intended to cooperate with said at least two clamping rods to enable the top and bottom clamping plates to be assembled together, wherein it further includes: at least one system for the coupling, gastight at high temperature, of the solid-oxide stack of the SOEC/SOFC type, attached to at least one of the top and bottom clamping plates, including: a coupling flange attached to said at least one of the top and bottom clamping plates, the coupling flange comprising a through internal conduit to enable a gas inlet and/or outlet tube to pass, and at least one first through internal screwing orifice including a first internal thread, at least one clamping screw, provided with a clamping head, able to be screwed into said at least one first through internal screwing orifice, a seal, positioned between said at least one of the top and bottom clamping plates and against a first end face, opposite to a second end face, of the coupling flange, and wherein said at least one of the top and bottom clamping plates includes at least one second internal screwing orifice comprising a second internal thread opposite the first internal thread, said at least one clamping screw being able to be screwed into said at least one second internal screwing orifice for attaching the coupling flange to said at least one of the top and bottom clamping plates, and includes a through gas-passage conduit, intended to be in fluidic communication with the solid-oxide stack of the SOEC/SOFC type and said gas inlet and/or outlet tube.

2. Assembly according to claim 1, wherein said at least one of the top and bottom clamping plates and the coupling flange are produced from the same material.

3. Assembly according to claim 1, wherein the gas inlet and/or outlet tube includes a spiral winding, comprising at least four turns.

4. Assembly according to claim 1, wherein said at least one clamping screw and the coupling flange are produced from the same material.

5. Assembly according to claim 1, wherein the number of clamping screws, the number of first through internal screwing orifices and the number of second internal screwing orifices is between 2 and 10.

6. Assembly according to claim 1, wherein the coupling flange includes at least one shoulder on the lateral surface of the coupling flange.

7. Assembly according to claim 1, wherein it includes a top end plate and a bottom end plate, between which the plurality of electrochemical cells and the plurality of intermediate connectors are gripped.

8. System, including: an assembly according to claim 1, a furnace, to which at least one gas inlet and/or outlet tube is connected, and to which the solid-oxide stack of the SOEC/SOFC type operating at high temperature is coupled for the entry and exit of gas by means of said at least one coupling system gastight at high temperature.

9. Method for the coupling, gastight at high temperature, of a solid-oxide stack of the SOEC/SOFC type implemented by means of an assembly according to claim 1, wherein it includes the step of coupling the solid-oxide stack of the SOEC/SOFC type to at least one gas inlet and/or outlet tube by means of said at least one coupling system gastight at high temperature.

10. Method according to claim 9, wherein it includes the step of heat treatment of the coupling flange and of said at least one clamping screw before coupling.

11. Method according to claim 10, wherein the heat treatment step consists of a progressive heating up to a predetermined heat-treatment temperature to reach a plateau at the predetermined heat-treatment temperature, and then progressive cooling to the initial temperature.

12. Method according to claim 10, wherein, before coupling, said at least one clamping screw is subjected to the use of an anti-binding paste resistant to high temperature.

13. Method according to claim 12, wherein the anti-binding paste has in its composition a weight proportion of chromium powder Cr.sub.3 of between 10 and 90%.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0085] The invention can be better understood from the reading of the following detailed description of non-limitative examples of embodiment thereof, as well as from the examination of the schematic partial figures of the accompanying drawing, on which:

[0086] FIG. 1 is a schematic view showing the operating principle of a high-temperature solid-oxide electrolyser (SOEC),

[0087] FIG. 2 is an exploded schematic view of a part of a high-temperature solid-oxide electrolyser (SOEC) comprising interconnectors according to the prior art,

[0088] FIG. 3 illustrates the principle of the architecture of a furnace on which a high-temperature electrolysis stack (SOEC) or fuel cell (SOFC) operating at high temperature is placed,

[0089] FIG. 4 shows, in perspective and by observation from above, an example of an assembly according to the invention comprising a solid-oxide stack of the SOEC/SOFC type and a system for clamping the stack, which may include a coupling system gastight at high temperature,

[0090] FIG. 5 shows, in perspective and by observation from below, another example of an assembly according to the invention comprising a solid-oxide stack of the SOEC/SOFC type and a system for clamping the stack, furthermore comprising four coupling systems gastight at high temperature,

[0091] FIG. 6 shows, in a view in partial longitudinal section, a detail of the assembly of FIG. 5 with the bottom clamping plate and a coupling system gastight at high temperature,

[0092] FIG. 7 shows, in a partial perspective, an example of a system according to the invention including the assembly of FIG. 5 and a furnace, to which the solid-oxide stack of the SOEC/SOFC type is coupled for feeding and discharging gases by means of four coupling systems gastight at high temperature, and

[0093] FIG. 8 shows, in a view from below, a detail of the assembly of FIG. 5 with regard to a coupling system gastight at high temperature.

[0094] In all these figures, identical references may designate identical or similar elements.

[0095] In addition, the various parts shown in the figures are not necessarily shown to a uniform scale, to make the figures more legible.

DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS

[0096] FIGS. 1 to 3 have already been described previously in the part relating to the prior art and to the technical context of the invention. It is stated that, for FIGS. 1 and 2, the symbols and the arrows for the supply of steam H.sub.2O, for the distribution and recovery of dihydrogen H.sub.2, of oxygen O.sub.2, of air and of electric current, are shown for purposes of clarity and precision, to illustrate the operation of the devices shown.

[0097] Furthermore, it must be noted that all the constituents (anode/electrolyte/cathode) of a given electrochemical cell are preferentially ceramics. The operating temperature of a stack of the high-temperature SOEC/SOFC type is moreover typically between 600 and 1000° C.

[0098] In addition, any terms “top” and “bottom” are to be understood here according to the normal direction of orientation of a stack of the SOEC/SOFC type when in its configuration of use.

[0099] With reference to FIG. 4, an example has been illustrated of an assembly 80 comprising a solid-oxide stack 20 of the SOEC/SOFC type and a clamping system 60, this assembly 80 being able to comprise a coupling system 90 gastight at high temperature as described hereinafter with reference to FIGS. 5 to 8.

[0100] Advantageously, the assembly 80 according to the invention has a structure similar to that of the assembly described in the French patent application FR 3 045 215 A1, apart from the presence here of a coupling system gastight at high temperature 90, i.e. the stack 20 has a character of the “Plug & Play” (PnP) type.

[0101] Also, as is common to the various embodiments of the invention described hereinafter, and as can be seen in FIG. 4, the assembly 80 includes a solid-oxide stack 20 of the SOEC/SOFC type operating at high temperature.

[0102] This stack 20 includes a plurality of electrochemical cells 41 each formed by a cathode, an anode and an electrolyte interposed between the cathode and the anode, and a plurality of intermediate interconnectors 42 each arranged between two adjacent electrochemical cells 41. This assembly of electrochemical cells 41 and intermediate interconnectors 42 may also be referred to as a stack.

[0103] In addition, the stack 20 includes a top end plate 43 and a bottom end plate 44, respectively also referred to as top stack end plate 43 and bottom stack end plate 44, between which the plurality of electrochemical cells 41 and the plurality of intermediate interconnectors 42 are gripped, i.e. between which the stack is located.

[0104] Moreover, the assembly 80 also includes a system 60 for clamping the solid-oxide stack 20 of the SOEC/SOFC type, including a top clamping plate 45 and a bottom clamping plate 46, between which the solid-oxide stack 20 of the SOEC/SOFC type is gripped.

[0105] Each clamping plate 45, 46 of the clamping system 60 includes four clamping orifices 54.

[0106] In addition, the clamping system 60 furthermore includes four clamping rods 55, or tie rods, extending through a clamping orifice 54 in the top clamping plate 45 and through a corresponding clamping orifice 54 in the bottom clamping plate 46 to enable the top 45 and bottom 46 clamping plates to be assembled together.

[0107] The clamping system 60 also includes clamping means 56, 57, 58 at each clamping orifice 54 of the top 45 and bottom 46 clamping plates cooperating with the clamping rods 55 to enable the top 45 and bottom 46 clamping plates to be assembled together.

[0108] More precisely, the clamping means include, at each clamping orifice 54 of the top clamping plate 45, a first clamping nut 56 cooperating with the corresponding clamping rod 55 inserted through the clamping orifice 54. In addition, the clamping means include, at each clamping orifice 54 in the bottom clamping plate 46, a second clamping nut 57 associated with a clamping washer 58, these cooperating with the corresponding clamping rod 55 inserted through the clamping orifice 54. The clamping washer 58 is located between the second clamping nut 57 and the bottom clamping plate 46.

[0109] In accordance with the invention, the assembly 80 includes at least one system 90 for the coupling, gastight at high temperature, of the stack 20, for example as described with reference to FIGS. 5 to 8 but not visible on FIG. 4.

[0110] Such an example of a coupling system 90 gastight at high temperature will now be described with reference to FIGS. 5 to 8 relating to one and the same embodiment shown in various views. This coupling is implemented in a hot gas-inlet zone.

[0111] In this example, the assembly 80 includes four coupling systems 90 gastight at high temperature attached to the bottom clamping plate 46, in proximity to the four clamping nuts 56.

[0112] Thus, these four coupling systems 90 gastight at high temperature, for coupling to the furnace 10, are distributed regularly around a support stud 100, secured to the bottom clamping plate 46, intended to allow the support of the assembly 80 in the furnace 10.

[0113] As more particularly visible in FIG. 6, each gastight coupling system 90 includes first of all a coupling flange 110. This coupling flange 110 includes a first end face 110a opposite the bottom clamping plate 46, and a second opposite end face 110b onto which the heads 105a of the clamping screws 105 described subsequently come into abutment.

[0114] In addition, this coupling flange 110 includes a through internal conduit 111, emerging on the first 110a and second 110b end faces, which allows the passage of a tube 103 intended to provide the entry and/or exit of gas G.

[0115] Moreover, each coupling flange 110 includes four first through internal screwing orifices 112, each emerging on the first 110a and second 110b end faces and including a first internal thread 112a to allow the introduction and screwing of four clamping screws 105, each provided with a screwing head 105a. In addition, the bottom clamping plate 46 also includes four second internal screwing orifices 113 each comprising a second internal thread 113a to allow the introduction and screwing of the four clamping screws 105. In this way, the coupling system 90 is demountable.

[0116] Furthermore, each gastight coupling system 90 also includes a compressive seal 118, preferentially metallic, for example in a C shape. This seal 118 is positioned against the first end face 110a of the coupling flange 110 and against the bottom clamping plate 46. Advantageously, the seal 118 is compressed by means of easily accessible planar surfaces.

[0117] Advantageously, the seal 118 is formed by a flexible metal seal comprising: a core consisting of a metal helical spring with contiguous turns closed on itself and having, in the state of rest, the form of a torus; a first envelope made from non-ductile metal in which the spring is embedded, this envelope having, in the state of rest, the form of a toric surface the generatrix circle of which does not close on itself; and a second envelope made from ductile metal in which the first envelope is embedded and also having, in the state of rest, the form of a toric surface the generatrix circle of which does not close on itself. Such an example of a seal is described in the French patent application FR 2 151 186 A1.

[0118] The seal 118 can be produced from a nickel-based superalloy, in particular of the Inconel 600 type. It may have an inside diameter of approximately 12.5 mm and an outside diameter of approximately 17.5 mm. It may be coated with gold and the clamping torque may be between 1 N.m and 20 N.m with a preferential value 4 N.m for excessively strong adhesion.

[0119] In order to be able to mount each gastight coupling system 90 on the bottom clamping plate 46 and to provide the entry and/or exit of the gas G, the bottom clamping plate 46 includes a through conduit 102 for passage of gas G, in fluidic communication with the solid-oxide stack 20 of the SOEC/SOFC type and the tube 103 for entry and/or exit of gas G. For example, the tube 103 may be welded to the conduit 102, for example by TIG method or any other welding means. The connection of the tube 103 by welding in the internal conduit 111 is facilitated since the welding is done on a solid part that limits the deformations due to welding.

[0120] Advantageously, the bottom clamping plate 46 and the coupling flanges 110 are produced from the same material, in particular from austenitic stainless steel, in particular of the 310S type. In this way, the thermal expansions are identical.

[0121] Moreover, as can be seen in FIG. 7, which shows a system 130 according to the invention, each tube 103 includes a spiral winding 103e in order to increase the flexibility of the assembly and to be able to position the first end face 110a of the coupling flange 110 parallel to the bottom clamping plate 46. It must be noted that the number of turns and the dimensions, in particular the diameter, of the spiral winding 103e will depend on the type of tube 103 used. By way of example, the spiral winding 103e may be formed by four turns with a diameter of 200 mm for a tube 103 with an inside diameter of 10 mm and an outside diameter of 12 mm.

[0122] Advantageously, the clamping screws 115 produced from the same material as the coupling flanges 110, in particular from austenitic stainless steel, in particular of the 310S type. In this way, the thermal expansions are identical.

[0123] Although in the example described here the number of clamping screws 115 is equal to 4, this is in no way limitative. In particular, the number of clamping screws 115 may be between 2 and 10. The use of a plurality of clamping screws 115 advantageously makes it possible to limit the size thereof and to allow lesser tightening of each screw so as to limit binding. In particular, a tightening of the order of 1 to 10 N/m can be envisaged, preferentially of the order of 4 N/m.

[0124] Preferentially, before use of the coupling flanges 110 and of the clamping screws 118, heat treatment is carried out. This treatment consists in subjecting them to a temperature progressively increasing up to 800° C. at a rate of 5° C./min. Then a plateau at 800° C. is maintained for 1 hour before proceeding with a cooling by a reduction in the temperature at a rate of 5° C./min. This heat treatment can take place under air, under neutral gas or under reducing gas. The value of 800° C. is preferential but the heat-treatment temperature may be between 600 and 950° C., and preferentially between 700 and 870° C. In this way, the materials are subjected to temperatures close to those of use. The heating speed is not critical but the temperature plateau, here preferentially indicated at a duration of 1 hour, can be between 10 min and several hours.

[0125] Moreover, before fitting and clamping, the clamping screws 115, in particular the screw pitch and the parts under the heads 115a, may be subjected to the use of an anti-binding paste resistant to high temperature to facilitate dismantling and to avoid the phenomenon of diffusion welding in the threads during the thermal cycling. This anti-binding paste also lubricates the connection and resists corrosion. It avoids jamming and excessive wear on the parts exposed to extreme temperature or in a so-called aggressive atmosphere, for example in the case of threads of thermal machines, manifolds for hot gases, burners, valves, disc brakes, spark plugs, exhaust brackets, rollers, bolts, collars, etc.

[0126] This anti-binding paste is preferentially in the form of a grease comprising 50% by weight chromium powder Cr.sub.3 and 50% by weight industrial multi-use grease based on mineral oil or any other constituent. It must be noted that the proportion of the Cr.sub.3 powder is preferentially 50% by weight but may also be between 10 and 90% by weight. The grease obtained then has a characteristic green colour.

[0127] Moreover, FIG. 8 illustrates the fact that each coupling flange 110 includes at least one shoulder 120, here two opposite shoulders 120, on its lateral surface 110c. This shoulder 120 is intended to be located at the passage of the clamping screws 56 so as to obtain both a compact device and ease of implementation.

[0128] Naturally, the invention is not limited to the example embodiments that have just been described. Various modifications can be made thereto by a person skilled in the art.