SOEC / SOFC solid oxide stack assembly and hotplate clamping device

Description

TECHNICAL FIELD

[0001] The present invention relates to the general field of high temperature electrolysis (HTE), in particular high temperature steam electrolysis (HTSE), respectively designated by the English names "High Temperature Electrolysis" (HTE) and "High Temperature Steam Electrolysis" (HTSE), of the electrolysis of carbon dioxide (CO 2 ), or even of the co-electrolysis of water vapor and carbon dioxide (CO 2 ) at high temperature.

[0002] More specifically, the invention relates to the field of high-temperature solid oxide electrolysers, usually designated by the acronym SOEC (for “Solid Oxide Electrolysis Cell” in English).

[0003] It also concerns the field of high-temperature solid oxide fuel cells, usually designated by the acronym SOFC (for “Solid Oxide Fuel Cells” in English).

[0004] Thus, more generally, the invention refers to the field of solid oxide stacks of the SOEC / SOFC type operating at high temperature.

[0005] More specifically, the invention relates to an assembly comprising a stack of solid oxide cells of the SOEC / SOFC type and a clamping system comprising at least one removable and interchangeable heating plate, as well as an associated manufacturing method. STATE OF THE PRIOR ART

[0006] In the context of a high-temperature solid oxide electrolyzer of the SOEC type, it is a question of transforming, by means of an electric current, within the same electrochemical device, water vapor (H 2 O) into dihydrogen (H 2 ) and dioxygen (O 2 ), and / or of transforming carbon dioxide (CO 2 ) into carbon monoxide (CO) and dioxygen (O 2 ). In the context of a high-temperature solid oxide fuel cell of the SOFC type, the operation is reversed to produce an electric current and heat by being supplied with dihydrogen (H 2 ) or other fuels such as methane (CH 4 ), natural gas, biogas, and dioxygen (O 2 ), typically air. For the sake of simplicity, the following description focuses on the operation of a high-temperature solid oxide electrolyzer of the SOEC type performing the electrolysis of water vapor.However, this operation is applicable to the electrolysis of carbon dioxide (CO2), or even to the co-electrolysis of high-temperature water vapor with carbon dioxide (CO2). In addition, this operation can be transposed to the case of a high-temperature solid oxide fuel cell of the SOFC type.

[0007] To carry out the electrolysis of water, it is advantageous to carry it out at high temperature, typically between 600 and 1000°C, because it is more advantageous to electrolyze water vapor than liquid water and because part of the energy necessary for the reaction can be provided by heat, which is cheaper than electricity.

[0008] To implement high-temperature steam electrolysis (HTSE), a high-temperature solid oxide electrolyzer of the SOEC type consists of a stack of elementary patterns, each comprising a solid oxide electrolysis cell, or electrochemical cell, consisting of three anode / electrolyte / cathode layers superimposed on each other, and interconnection plates made of metal alloys, also called bipolar plates or interconnectors. Each electrochemical cell is sandwiched between two interconnection plates. A high-temperature solid oxide electrolyzer of the SOEC type is then an alternating stack of electrochemical cells and interconnectors. A high-temperature solid oxide fuel cell of the SOFC type consists of the same type of stack of elementary patterns.Since this high-temperature technology is reversible, the same stack can operate in electrolysis mode and produce hydrogen and oxygen from water and electricity, or in fuel cell mode and produce electricity from hydrogen and oxygen.

[0009] Each electrochemical cell corresponds to an electrolyte / electrode assembly, which is typically a multi-layer ceramic assembly whose electrolyte is formed by a central ion-conducting layer, this layer being solid, dense and waterproof, and sandwiched between the two porous layers forming the electrodes. It should be noted that additional layers may exist, but these only serve to improve one or more of the layers already described.

[0010] The electrical and fluidic interconnection devices are electronic conductors which ensure, from an electrical point of view, the connection of each electrochemical cell of elementary pattern in the stack of elementary patterns, guaranteeing the electrical contact between one face and the cathode of a cell and between the other face and the anode of the following cell, and from a fluidic point of view, the supply of reactants and the evacuation of products for each of the cells. The interconnectors thus ensure the functions of supplying and collecting electric current and delimiting gas circulation compartments, for distribution and / or collection.

[0011] More specifically, the main function of the interconnectors is to ensure the passage of electric current but also the circulation of gases in the vicinity of each cell (namely: injected water vapor, hydrogen and oxygen extracted for EHT electrolysis; air and fuel including injected hydrogen and extracted water for a SOFC cell), and to separate the anode and cathode compartments of two adjacent cells, which are the gas circulation compartments on the anode and cathode sides of the cells respectively.

[0012] In particular, for a high-temperature solid oxide electrolyzer of the SOEC type, the cathode compartment contains water vapor and hydrogen, the product of the electrochemical reaction, while the anode compartment contains a drain gas, if present, and oxygen, another product of the electrochemical reaction. For a high-temperature solid oxide fuel cell of the SOFC type, the anode compartment contains the fuel, while the cathode compartment contains the fuel.

[0013] To perform high-temperature steam electrolysis (HTE), water vapor (H 2 O) is injected into the cathode compartment. Under the effect of the electric current applied to the cell, the dissociation of water molecules in the form of vapor is carried out at the interface between the hydrogen electrode (cathode) and the electrolyte: this dissociation produces dihydrogen gas (H 2 ) and oxygen ions (O 2-< ). The dihydrogen (H 2 ) is collected and evacuated at the outlet of the hydrogen compartment. The oxygen ions (O 2-< ) migrate through the electrolyte and recombine into dioxygen (O 2 ) at the interface between the electrolyte and the oxygen electrode (anode). A draining gas, such as air, can circulate at the anode and thus collect the oxygen generated in gaseous form at the anode.

[0014] To operate a solid oxide fuel cell (SOFC), air (oxygen) is injected into the cathode compartment of the cell and hydrogen into the anode compartment. The oxygen in the air will dissociate into O 2-< ions. These ions will migrate in the electrolyte from the cathode to the anode to oxidize the hydrogen and form water with simultaneous production of electricity. In SOFC cells, just like in SOEC electrolysis, the water vapor is in the dihydrogen (H 2 ) compartment. Only the polarity is reversed.

[0015] As an illustration, the Figure 1 represents a schematic view showing the operating principle of a high-temperature solid oxide electrolyzer of the SOEC type. The function of such an electrolyzer is to transform water vapor into hydrogen and oxygen according to the following electrochemical reaction: 2 H 2 O → 2 H 2 + O 2 .

[0016] This reaction is carried out electrochemically in the cells of the electrolyser. As shown in the diagram Figure 1 , each elementary electrolysis cell 1 is formed of a cathode 2 and an anode 4, placed on either side of a solid electrolyte 3. The two electrodes (cathode and anode) 2 and 4 are electronic and / or ionic conductors, made of porous material, and the electrolyte 3 is gas-tight, electronically insulating and ionically conductive. The electrolyte 3 may in particular be an anionic conductor, more precisely an anionic conductor of O 2-< ions and the electrolyser is then called an anionic electrolyser, as opposed to protonic electrolytes (H +< ).

[0017] Electrochemical reactions take place at the interface between each of the electronic conductors and the ionic conductor.

[0018] At cathode 2, the half-reaction is as follows: 2 H 2 O + 4 e -< → 2 H 2 + 2 O 2-< .

[0019] At anode 4, the half-reaction is: 2 O 2-< → O 2 + 4 e -< .

[0020] Electrolyte 3, intercalated between the two electrodes 2 and 4, is the place of migration of the O 2-< ions under the effect of the electric field created by the potential difference imposed between the anode 4 and the cathode 2.

[0021] As shown in parentheses on the Figure 1 , the water vapor at the cathode inlet can be accompanied by hydrogen H 2 and the hydrogen produced and recovered at the outlet can be accompanied by water vapor. Similarly, as shown in dotted lines, a draining gas, such as air, can also be injected at the inlet on the anode side to evacuate the oxygen produced. The injection of a draining gas has the additional function of acting as a thermal regulator.

[0022] An elementary electrolyzer, or electrolysis reactor, consists of an elementary cell as described above, with a cathode 2, an electrolyte 3, and an anode 4, and two interconnectors which provide the electrical and fluid distribution functions.

[0023] To increase the flow rates of hydrogen and oxygen produced, it is known to stack several elementary electrolysis cells on top of each other, separated by interconnectors. The assembly is positioned between two end interconnection plates that support the electrical supplies and gas supplies of the electrolyzer (electrolysis reactor).

[0024] A high-temperature solid oxide electrolyser of the SOEC type thus comprises at least one, generally a plurality of electrolysis cells stacked on top of each other, each elementary cell being formed of an electrolyte, a cathode and an anode, the electrolyte being intercalated between the anode and the cathode.

[0025] As previously indicated, the fluidic and electrical interconnection devices which are in electrical contact with one or more electrodes generally provide the functions of supplying and collecting electric current and delimit one or more gas circulation compartments.

[0026] Thus, the so-called cathode compartment has the function of distributing the electric current and water vapor as well as recovering hydrogen at the cathode in contact.

[0027] The so-called anode compartment has the function of distributing the electric current as well as recovering the oxygen produced at the anode in contact, possibly using a draining gas.

[0028] There Figure 2 represents an exploded view of elementary patterns of a high-temperature solid oxide electrolyzer of the SOEC type according to the prior art. This electrolyzer comprises a plurality of elementary electrolysis cells C1, C2, of the solid oxide cell (SOEC) type, stacked alternately with interconnectors 5. Each cell C1, C2 consists of a cathode 2.1, 2.2 and an anode (only the anode 4.2 of cell C2 is shown), between which an electrolyte is arranged (only the electrolyte 3.2 of cell C2 is shown).

[0029] The interconnector 5 is a metal alloy component that ensures the separation between the cathode 50 and anode 51 compartments, defined by the volumes between the interconnector 5 and the adjacent cathode 2.1 and between the interconnector 5 and the adjacent anode 4.2 respectively. It also ensures the distribution of gases to the cells. The injection of water vapor into each elementary pattern is done in the cathode compartment 50. The collection of the hydrogen produced and the residual water vapor at the cathode 2.1, 2.2 is carried out in the cathode compartment 50 downstream of the cell C1, C2 after dissociation of the water vapor by the latter. The collection of the oxygen produced at the anode 4.2 is carried out in the anode compartment 51 downstream of the cell C1, C2 after dissociation of the water vapor by the latter.The interconnector 5 ensures the passage of current between cells C1 and C2 by direct contact with the adjacent electrodes, i.e. between the anode 4.2 and the cathode 2.1.

[0030] Since the operating conditions of a high-temperature solid oxide electrolyser (SOEC) are very close to those of a solid oxide fuel cell (SOFC), the same technological constraints are encountered.

[0031] Thus, the proper functioning of such SOEC / SOFC type solid oxide stacks operating at high temperature mainly requires satisfying the points set out below.

[0032] First of all, it is necessary to have electrical insulation between two successive interconnectors, otherwise the electrochemical cell will be short-circuited, but also good electrical contact and a sufficient contact surface between a cell and an interconnector. The lowest possible ohmic resistance is sought between cells and interconnectors.

[0033] Furthermore, it is necessary to have a seal between the anode and cathode compartments, otherwise there will be a recombination of the gases produced, leading to a drop in efficiency and, above all, the appearance of hot spots damaging the stack.

[0034] Finally, it is essential to have good gas distribution both at the inlet and during product recovery, otherwise there will be a loss of efficiency, inhomogeneity of pressure and temperature within the different elementary patterns, or even prohibitive degradation of the electrochemical cells.

[0035] Conventionally, the incoming and outgoing gases in a high temperature electrolysis stack (SOEC) or fuel cell stack (SOFC) operating at high temperature can be managed through devices such as that illustrated with reference to Figure 3 The device 13 thus comprises cold parts PF and hot parts PC, the latter comprising the furnace bottom 11, the furnace bell 10, a loop tube 12 for managing the gas inlets and outlets and the stack 20, also called a “stack”, of high-temperature electrolysis (SOEC) or fuel cell (SOFC).

[0036] French patent application FR 3 045 215 A1 discloses a principle of an autonomous clamping system for a SOEC / SOFC type stack to make it autonomous and give it a "Plug & Play" (PnP) type character, i.e. a "plug and play" type. Such a stack concept, having removable integrated heating elements, for example of the electrical resistance type, allows both the application of the force to the manufacture of the stack, the maintenance of this same force, including in operation at high temperature, as well as the supply of heat necessary for its operation as close as possible to the stack.This PnP system with integrated heating units allows the stack to be quickly installed within a so-called "Hot-Box" system, consisting of only an insulated and compact enclosure, and its operation without having to manage its tightening during operation at high temperature, despite the differential expansions of the various components, and the improvement of the thermal efficiency of the system and consequently its performance. This also allows for a gain in compactness in the heating zone since a resistive furnace is no longer necessary.

[0037] In reference to the Figure 4, an example of an assembly 80 has thus been illustrated comprising a stack 20 of solid oxides of the SOEC / SOFC type and a clamping system 60. This stack 20 comprises a plurality of electrochemical cells 41 each formed of a cathode, an anode and an electrolyte intercalated 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 is also referred to as a “stack”.

[0038] In addition, the stack 20 comprises an upper end plate 43 and a lower end plate 44, respectively also called upper stack end plate 43 and lower stack end plate 44, between which the plurality of electrochemical cells 41 and the plurality of intermediate interconnectors 42 are sandwiched, or between which the stack is located.

[0039] Furthermore, the assembly 80 also comprises a clamping system 60 for the stack 20 of solid oxides of the SOEC / SOFC type, comprising an upper clamping plate 45 and a lower clamping plate 46, between which the stack 20 of solid oxides of the SOEC / SOFC type is clamped. Each clamping plate 45, 46 of the clamping system 60 comprises four clamping orifices 54.

[0040] In addition, the clamping system 60 further comprises four clamping rods 55, or tie rods, extending through a clamping hole 54 of the upper clamping plate 45 and through a corresponding clamping hole 54 of the lower clamping plate 46 to allow the upper 45 and lower 46 clamping plates to be assembled together.

[0041] The clamping system 60 further comprises clamping means 56, 57, 58 at each clamping orifice 54 of the upper 45 and lower 46 clamping plates cooperating with the clamping rods 55 to allow the upper 45 and lower 46 clamping plates to be assembled together.

[0042] More specifically, the clamping means comprise, at each clamping orifice 54 of the upper 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 comprise, at each clamping orifice 54 of the lower 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 lower clamping plate 46.

[0043] Furthermore, French patent application FR 3 087 952 A1 also discloses a principle for integrating heating elements into the upper and lower plates of a PnP-type autonomous stack clamping system, in particular as described above. Thus, heating elements of the heating cord type are integrated into the two upper and lower clamping plates, which are about 30 mm thick, made of refractory austenitic steel, type AISI 310, by machining and brazing.

[0044] The heating elements integrated into the dense metal components in direct contact with the stack thus significantly improve heat transfer losses, which then occur by conduction without disturbance and uniformly across the contact areas. This allows for excellent thermal homogeneity between the upper and lower plates, and by extension good overall homogeneity of the stack, and increased responsiveness of the heating elements to the temperature setpoint for the electrolyser. This results in better thermal management of the entire system. Since the heating is integrated, the insulation can be modulated to the shapes of the stack, further limiting radiation to the outside. Such heat transfer efficiency of the heating elements then makes it possible to reduce the power supplied to the system by at least 100 W to operate at temperatures of around 600 to 1000°C.The temperature measured in the insulated enclosure follows a rising ramp almost identical to that of the plates, which is also a very good sign for the thermal control of the “Hot-Box”.

[0045] However, one of the problems with this technology is that if a heating element malfunctions, there is no room for maneuver. The thermal management of the stack is then lost, with no possibility of recovery. In addition, the cost of producing these heating elements, particularly in the form of resistors soldered onto the clamping plates, is very high and therefore restrictive.

[0046] There is therefore still a need to improve the integration of heating units in a high-temperature electrolysis stack (SOEC) or fuel cell (SOFC) while allowing operation at high temperatures, particularly between 600 and 1000°C. STATEMENT OF THE INVENTION

[0047] The invention aims to at least partially remedy the needs mentioned above and the drawbacks relating to the achievements of the prior art.

[0048] The invention thus relates, according to one of its aspects, to an assembly, comprising: a stack of solid oxide cells of the SOEC / SOFC type operating at high temperature, comprising: a plurality of electrochemical cells each formed of 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 stack of solid oxide cells of the SOEC / SOFC type, comprising an upper clamping plate and a lower clamping plate, between which the stack of solid oxide cells of the SOEC / SOFC type is clamped, each clamping plate comprising at least two clamping holes,the clamping system further comprising: at least two clamping rods each intended to extend through a clamping orifice of the upper clamping plate and through a corresponding clamping orifice of the lower clamping plate to allow the upper and lower clamping plates to be assembled together, clamping means at each clamping orifice of the upper and lower clamping plates intended to cooperate with said at least two clamping rods to allow the upper and lower clamping plates to be assembled together, characterized in that at least one of the upper and lower clamping plates comprises a housing, formed in the thickness of said at least one of the upper and lower clamping plates, comprising first and second opposite ends, at least one of which opens onto the lateral face of said at least one of the upper and lower clamping plates, said housing being located inside said at least one of the upper and lower clamping plates, at a distance from its upper and lower main faces which are substantially parallel to each other, and in that the assembly comprises at least one heating plate, removable and interchangeable, inserted into said housing.

[0049] Thanks to the invention, it may be possible to maintain the interests associated with the integration of heating elements in the thick clamping plates, which makes it possible to improve the thermal efficiency of the SOEC / SOFC type stack while minimizing heat losses and maintaining the same dimensioning of the elements of the autonomous clamping system described above. In addition, the principle of the invention makes it possible to make the heating element(s) removable and interchangeable, in particular in the event of their malfunction.

[0050] The assembly according to the invention may also include one or more of the following characteristics taken in isolation or in any possible technical combination.

[0051] Said housing and said at least one heating plate may have a substantially parallelepiped shape, in particular a block shape or a cubic shape.

[0052] Furthermore, said housing may be formed, in the thickness of said at least one of the upper and lower clamping plates, centrally, at an equal distance from the upper and lower main faces, and at an equal distance from the clamping holes, between the clamping holes.

[0053] In addition, the thickness of said housing may be between 5 mm and 10 mm, in particular of the order of 8 mm. The width of said housing may be between 20 mm and 86 mm, in particular of the order of 86 mm.

[0054] Furthermore, said at least one heating plate may comprise a heating resistor whose maximum power is at least 1200 W.

[0055] Said at least one heating plate may be made of ceramic or metal alloy, in particular stainless steel or nickel-based alloy, being in particular treated with an aluminizing coating.

[0056] In addition, a clearance may be present between the external surface of said at least one heating plate and the internal surface of said housing, the dimension of which may be between 0.2 and 0.5 mm.

[0057] Furthermore, said at least one of the upper and lower clamping plates may comprise at least one internal groove formed in the thickness of said at least one of the upper and lower clamping plates, and extending substantially parallel to the upper and lower faces thereof, and at least one end of which opens onto the lateral face of said at least one of the upper and lower clamping plates. The assembly may then comprise at least one thermocouple device inserted into said at least one internal groove.

[0058] In particular, said at least one internal groove may comprise a first internal safety groove and a second internal regulation groove. Said at least one thermocouple device may comprise a first safety thermocouple device inserted in the first internal groove and a second regulation thermocouple device inserted in the second internal groove.

[0059] Furthermore, the assembly may include an upper end plate and a lower end plate, between which the plurality of electrochemical cells and the plurality of intermediate interconnectors are sandwiched.

[0060] In addition, said at least one of the upper and lower clamping plates can advantageously be manufactured by an additive manufacturing technique, being in particular made of refractory austenitic steel, in particular of the AISI 310 type.

[0061] Furthermore, said at least one of the upper and lower clamping plates may have a thickness of between 20 and 30 mm, in particular of the order of 25 mm.

[0062] Furthermore, the invention also relates, according to another of its aspects, to a system, characterized in that it comprises: an assembly as defined previously, a device, to which at least one gas inlet and / or outlet tube is connected, and to which the stack of solid oxide cells of the SOEC / SOFC type operating at high temperature is coupled for the supply and outlet of gases.

[0063] Furthermore, the invention also relates, according to another of its aspects, to a method of manufacturing an assembly as defined above, characterized in that it comprises the step of producing said housing in said at least one of the upper and lower clamping plates.

[0064] The step of producing said housing may, for example, include production by electroerosion by sinking and / or by additive manufacturing. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] The invention may be better understood by reading the detailed description which follows, non-limiting examples of its implementation, as well as by examining the schematic and partial figures of the attached drawing, in which: [ Fig. 1 ] is a schematic view showing the operating principle of a high-temperature solid oxide electrolyzer (SOEC), [ Fig. 2 ] is an exploded schematic view of a portion of a high temperature solid oxide electrolyzer (SOEC) comprising interconnectors according to the prior art, [ Fig. 3 ] illustrates the principle of the architecture of a device on which a high-temperature electrolysis stack (SOEC) or fuel cell (SOFC) operating at high temperature is placed, [ Fig. 4] represents, in perspective and by observation from above, an example of an assembly comprising a stack of solid oxide cells of the SOEC / SOFC type and a stack clamping system, [ Fig. 5 ] represents, in perspective and by observation from above, an example of an assembly in accordance with the invention comprising a stack of solid oxide cells of the SOEC / SOFC type, a stack clamping system, and two heating plates inserted into corresponding housings formed in the clamping plates, [ Fig. 6 ] represents, in a perspective view and by observation from above and in transparency, an upper clamping plate of an assembly according to the invention, represented in isolation, [ Fig. 7 ] is a partial lateral view along VII of [ Fig. 6 ], [ Fig. 8 ] represents, by observation from below, a lower clamping plate of an assembly according to the invention, such as that of [ Fig. 5 ], And [ Fig. 9] is a partial side perspective view of the assembly according to the invention of [ Fig. 5 ].

[0066] Throughout these figures, like references may designate identical or similar elements.

[0067] Furthermore, the different parts represented in the figures are not necessarily on a uniform scale, to make the figures more readable. DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

[0068] THE figures 1 to 4 have already been described previously in the section relating to the state of the prior art and the technical context of the invention. It is specified that, for the Figures 1 and 2 , the symbols and arrows for the supply of water vapor H 2 O, distribution and recovery of dihydrogen H 2 , oxygen O 2 , air and electric current, are shown for clarity and precision, to illustrate the operation of the devices represented.

[0069] Furthermore, it should be noted that all the components (anode / electrolyte / cathode) of a given electrochemical cell are preferably ceramics. The operating temperature of a high-temperature SOEC / SOFC stack is also typically between 600 and 1000°C.

[0070] In addition, the possible terms “upper” and “lower” are to be understood here according to the normal orientation of a SOEC / SOFC type stack when in its usage configuration.

[0071] THE figures 5 to 9 relate to an exemplary embodiment of an assembly 80 in accordance with the invention. In particular, the Figure 5 represents an example of an assembly 80 in accordance with the invention similar to that described previously with reference to the Figure 4 . Also, the common elements of the figures 4 And 5 will not be described again.

[0072] According to the invention, each upper 45 and lower 46 clamping plate comprises a housing 90. The characteristics of such housings 90 are better seen with reference to figures 6 to 8 .

[0073] Each housing 90 is formed in the thickness ep of each upper 45 and lower 46 clamping plate. It comprises a first end 90a and a second end 90b, opposite one another, which both open onto the lateral face FL of each clamping plate 45, 46.

[0074] The housing 90 is formed inside the corresponding clamping plate 45, 46, passing through it along a longitudinal axis passing through the middle of the plate. It is therefore centered inside the clamping plate 45, 46. In particular, as seen in the Figure 6 relative to the upper clamping plate 45, the housing 90 is formed at an equal distance from the clamping holes 54, between them. Similarly, as visible on the figure 8 relative to the lower clamping plate 46, the housing 90 is formed at an equal distance from the gas inlet and / or outlet passage holes 97. Each housing 90 is thus intended to receive a heating plate 95, as visible in the Figure 5 . Each hot plate 95 is powered via power cords 98 visible on the Figure 5 The positioning of the heating plates 95, provided with such electrical inlets in the form of cables 98, can be done so that these are located outside the side generating the least disturbance.

[0075] Preferably, each housing 90 and each heating plate 95 are in a substantially parallelepiped shape, and in particular here a substantially block shape, but it could also be a cubic shape, or even another shape.

[0076] Advantageously, the invention therefore allows the use of removable and interchangeable heating plates. Also, in the event of deterioration of a heating plate, it can be easily replaced.

[0077] The dimensions of the housing 90 and the heating plate 95 may vary according to different needs and in particular according to the nature of the heating plates used.

[0078] Generally, the thickness el of the housing 90 is between 5 mm and 10 mm, being for example here of the order of 8 mm, and the width l of the housing 90 is between 20 mm and 86 mm, being for example here of the order of 86 mm.

[0079] Furthermore, the thickness e' of the heating plate 95 is between 5 mm and 10 mm, being for example here of the order of 5 mm, the width l' of the heating plate 95, in particular its heating surface, is between 20 mm and 86 mm, being for example here of the order of 84 mm, and the length L' of the heating plate 95, in particular its heating surface, is between 210 mm and 220 mm, being for example here of the order of 260 mm.

[0080] The housings 90, or openings, formed in the upper 45 and lower 46 clamping plates can be produced in different ways. In particular, they can be obtained by a die-sinking electroerosion process (or EDM for “Electrical Discharge Machining” in English) and / or by an additive manufacturing process, including in particular 3D printing.

[0081] On the one hand, die-sinking EDM is a machining process that involves removing material from a part using electrical discharges. It is also known as spark machining. This technique is characterized by its ability to machine all electrically conductive materials, such as metals, alloys, carbides, graphites, etc., regardless of their hardness. This machining process involves passing a current through a dielectric to generate a "bubble" of vapor or vacuum that ionizes and reabsorbs by imploding, resulting in the destruction of the material. This destruction, micro-implosion, causes the spark. The high-intensity current ionizes a channel through the dielectric. A disruptive discharge then occurs, from the electrode to the part to be machined, damaging it very locally, in the order of a few µm 2< .The dielectric then cools the deteriorated particles which fall into the machine's tank in the form of a sludge (microparticles of matter and dielectric).

[0082] On the other hand, additive manufacturing technology allows, from a digital file model and with the help of a machine using a process such as extrusion or solidification of metal powder, polymer and polymer thread, to create, step by step, an object. This is called "layer by layer" printing. 3D printing boils down to a deposition of the molten material, selective filtering using an energy source (laser, resistors, electron beams, or ultraviolet light) which allows the object to be assembled and finally the solidification of the material during the cooling period, except in the case of stereolithography where a chemical phenomenon of polymerization occurs on photocrosslinkable resins. The machine prints each layer sequentially, one on top of the other, thus building a real object inside the machine's construction chamber.Once the 3D printer completes the last layer, a short drying cycle begins. Then the actual object can be removed, and potentially undergo a finishing treatment if necessary, such as sanding, baking for hardness, etc. Manufacturing therefore no longer consists of subtracting material, as traditional techniques do with rolling or machining, but rather adding it layer by layer in order to obtain the final object imagined in the desired material.

[0083] Furthermore, in order to be able to operate in the temperature ranges expected for a stack of SOFC / COEC type solid oxide cells, the 95 heating plates include heating resistors whose maximum power is at least 1200 W. Thus, they can reach a power of approximately 1200 W ± 10% under 230 V, which corresponds to a maximum temperature of the hot zone of 1000°C with good insulation and suitable regulation, thus making it possible to cover the power dissipated by the insulated enclosure. The 95 heating plates can be obtained commercially, in particular through companies specializing in high temperatures.

[0084] Heating plates can preferably be made of ceramic. Various dimensions and sizes can be produced. Such heating plates can have a hot zone with an operating range up to 1000°C and a cold zone in the contact zone up to 600°C, which can be protected by ceramic wool sheathing. However, large flat heating plates can be manufactured without a cold zone. The special properties and low mass of the ceramic material can enable fast heating rates, uniform temperature distribution, and precise control. The high emissivity and broad emission spectrum of thermal radiation can make the ceramic material, obtained from silicon nitride, an ideal radiant heating element. A power of 15 W / cm 2 < at 1000°C can be achieved.

[0085] Heating plates can also be made of a metal alloy. For example, they can be made of stainless steel, for example 316L stainless steel, or a nickel-based alloy, such as Inconel ®<, for example Inconel ®< 600. In this case, they are advantageously treated with an aluminizing coating on their surfaces so as not to weld with the surfaces with which they might be in contact.

[0086] In addition, the heating plates can be made up of heating cables, in particular composed of a heating core with mineral insulation, for example of the 96-99% magnesium oxide (MgO) type, under an Inconel ®< 600 sheath and integrated cold terminations, illustrated by the reference 95t on the Figure 5 The heating core can have a diameter between 1 and 2 mm at ± 0.05 mm over a given length.

[0087] Furthermore, as visible on the Figure 9, it should be noted that a clearance J is present between the external surface of the heating plate 95 and the internal surface of the housing 90. This clearance J may in particular have a dimension of between 0.2 and 0.5 mm.

[0088] When inserting the heating plate 95 into its housing 90, it can be coated with thermal grease, which will have the effect of filling the gap J and achieving good heat transfer.

[0089] Each clamping plate 45, 46 is for example made of refractory material of the 310s stainless steel type. Its coefficient of thermal expansion at 850°C is for example 18.2 (in 10 -6< .K -1< ), which gives a displacement of 0.012 mm for a width l of 86 mm of the housing 90. It should be noted that the expansion of the silicon nitride (ceramic) is negligible for a width of 86 mm.

[0090] Table 1 below presents data of interest for ceramic materials that can be used for the manufacture of 95 heating plates, and in particular the coefficients of thermal expansion. Table 1 Ceramic Linear thermal expansion coefficient 25-1000°C (10 -6< .K -1< ) Thermal conductivity (W / mK) Maximum operating temperature (°C) in air Resistance to thermal shock Alumina (94%-99.8%) 7,5 à 9,5 18 à 30 1500 à 1700 + Alumina-zirconia composite 8 25 1500 ++ Zirconia MgO & Y-TZP 10 2 à 2,5 1000 à 2000 ++ Aluminum nitride 5,5 140 à 180 800 ++ Sintered silicon carbide 4 à 5 80 à 125 1400 à 1900 +++ Sintered silicon nitride 3 à 4 20 à 25 1200 à 1500 +++ Quartz 0,5 1,5 950 à 1150 - Vitroceramic 13 1,5 800 -

[0091] Furthermore, in order to be able to control each heating plate 95, each clamping plate 45, 46 has internal grooves 100, 101, for example made in the form of holes, in order to insert two thermocouple devices per plate 45, 46.

[0092] Precisely, as visible on the Figure 9, a first internal safety groove 100 and a second internal regulation groove 101 are formed in the upper clamping plate 45, respectively allowing the insertion of a first safety thermocouple device and a second thermocouple device.

[0093] The first safety thermocouple device of the heating plate 95 is placed as close as possible to the area to be controlled, namely as close as possible to the heating resistor in order to avoid its overheating and deterioration. The second regulating thermocouple device of the heating plate 95 is located in the area of ​​interest making it possible to obtain information on the heat transfer to the stack 20, or stack.

[0094] It is important to note that expansion must also be taken into account, but since the clamping forces are at the bores of the clamping plates, care must be taken to ensure that the plates do not bend because the heating plates, preferably ceramic, would break.

[0095] In order to perform a finite element calculation, a housing 90 of 86 mm x 8 mm in the middle of the clamping plate was chosen. It is then necessary to verify that under a clamping force of 500 N per tie rod, the deflection of the clamping plate allows the heating plate 95 to be inserted or removed when the stack 20 is under clamping. The calculation was carried out at 800°C with the material of the clamping plate 45, 46 being 310S steel.

[0096] It was then observed that a deflection of the order of a micron is obtained, which does not pose any particular problem in allowing the assembly and disassembly of the heating plate 95.

[0097] Of course, the invention is not limited to the exemplary embodiments which have just been described. Various modifications may be made thereto by those skilled in the art.

Claims

1. An assembly (80), including: - an SOEC / SOFC type solid oxide cell stack (20) operating at high temperature, including: - a plurality of electrochemical cells (41) each formed of 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), - a system (60) for clamping the SOEC / SOFC type solid oxide cell stack (20), including an upper clamping plate (45) and a lower clamping plate (46), between which the SOEC / SOFC type solid oxide cell stack (20) is clamped, each clamping plate (45, 46) including at least two clamping holes (54), the clamping system (60) further including: - at least two clamping rods (55) intended to each extend through a clamping hole (54) of the upper clamping plate (45) and through a corresponding clamping hole (54) of the lower clamping plate (46) to allow the assembly of the upper (45) and lower (46) clamping plates together, - clamping means (56, 57, 58) at each clamping hole (54) of the upper (45) and lower (46) clamping plates intended to cooperate with said at least two clamping rods (55) to allow the assembly of the upper (45) and lower (46) clamping plates together, characterised in that at least one of the upper (45) and lower (46) clamping plates includes a housing (90), formed in the thickness (ep) of said at least one of the upper (45) and lower (46) clamping plates, comprising first (90a) and second (90b) opposite ends of which at least one opens onto the lateral face (FL) of said at least one of the upper (45) and lower (46) clamping plates, said housing (90) being located inside said at least one of the upper (45) and lower (46) clamping plates, at a distance from its upper (FS) and lower (FI) main faces, which are substantially parallel with each other, and in that the assembly (80) includes at least one, removable and interchangeable, heating plate (95) inserted into said housing (90).

2. The assembly according to claim 1, characterised in that said housing (90) and said at least one heating plate (95) have a substantially parallelepiped shape, particularly a block shape or a cubic shape.

3. The assembly according to claim 1 or 2, characterised in that said housing (90) is formed, in the thickness (ep) of said at least one of the upper (45) and lower (46) clamping plates, centrally, at equal distance from the upper (FS) and lower (FI) main faces, and at equal distance from the clamping holes (54), between the clamping holes (54).

4. The assembly according to one of the preceding claims, characterised in that the thickness (el) of said housing (90) is between 5 mm and 10 mm, particularly of the order of 8 mm, and in that the width (I) of said housing (90) is between 20 mm and 86 mm, particularly of the order of 86 mm.

5. The assembly according to any one of the preceding claims, characterised in that said at least one heating plate (95) includes a heating resistor, the maximum power of which is at least 1200 W.

6. The assembly according to any one of the preceding claims, characterised in that said at least one heating plate (95) is made of ceramic or metal alloy, particularly of stainless steel or nickel-based alloy, being particularly treated with an aluminising coating.

7. The assembly according to any one of the preceding claims, characterised in that a gap (J) is present between the outer surface of said at least one heating plate (95) and the inner surface of said housing (90), the dimension of which is between 0.2 and 0.5 mm.

8. The assembly according to any one of the preceding claims, characterised in that said at least one of the upper (45) and lower (46) clamping plates includes at least one inner groove (100, 101) formed in the thickness (ep) of said at least one of the upper (45) and lower (46) clamping plates and extending substantially parallel with the upper (FS) and lower (FI) faces thereof, and of which at least one end (100a, 101a) opens onto the lateral face (FL) of said at least one of the upper (45) and lower (46) clamping plates, and in that the assembly (80) includes at least one thermocouple device inserted into said at least one inner groove (100, 101).

9. The assembly according to claim 8, characterised in that said at least one inner groove (100, 101) includes a first inner safety groove (100) and a second inner control groove (101) and in that said at least one thermocouple device includes a first safety thermocouple device inserted into the first inner groove (100) and a second control thermocouple device inserted into the second inner groove (101).

10. The assembly according to any one of the preceding claims, characterised in that it includes an upper end plate (43) and a lower end plate (44), between which the plurality of electrochemical cells (41) and the plurality of intermediate interconnectors (42) are clamped.

11. The assembly according to any one of the preceding claims, characterised in that said at least one of the upper (45) and lower (46) clamping plates is manufactured by an additive manufacturing technique, being particularly made of refractory austenitic steel.

12. The assembly according to any one of the preceding claims, characterised in that said at least one of the upper (45) and lower (46) clamping plates has a thickness between 20 and 30 mm, in particular of the order of 25 mm.

13. A method for manufacturing an assembly (80) according to any one of the preceding claims, characterised in that it includes the step of producing said housing (90) in said at least one of the upper (45) and lower (46) clamping plates.

14. The method according to claim 13, characterised in that the step of producing said housing (90) comprises producing by electroerosion by die sinking and / or by additive manufacturing.