SELF-CLAMPING SYSTEM FOR SOLID OXIDE STACK

Abstract

The present invention relates to a self-supporting clamping system (1) for a high-temperature solid oxide stack (2), said self-supporting clamping system comprising an upper clamping plate (11) and a lower clamping plate (12), between which the solid oxide stack (2) is intended to be clamped, at least two clamping rods (14) for joining the upper and lower clamping plates (11, 12), clamping means (15) for applying a compressive force to the solid oxide stack, and at least one self-contained, sealed bellows containing a gas (17). The present invention also relates to an assembly comprising a self-supporting clamping system and at least one high-temperature solid oxide stack, and a method for mounting at least one high-temperature solid oxide stack. Figure for the abstract: Figure 2

Description

Title of the invention: SELF-Clamping system for solid oxide stacking TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to the field of high-temperature solid oxide stacks. It relates in particular to the field of high-temperature solid oxide electrolyzers and high-temperature solid oxide fuel cells. More specifically, the invention relates to a self-contained clamping system for a high-temperature solid oxide stack, an assembly comprising such a self-contained clamping system and at least one high-temperature solid oxide stack, or a method for mounting at least one high-temperature solid oxide stack. STATE OF THE ART

[0002] Solid oxide stacks are used in a known way at high temperature in various applications. They can serve as high-temperature solid oxide electrolyzers, commonly referred to by the English acronym SOEC (“Solid Oxide Electrolyzer Cell”) or as high-temperature solid oxide fuel cells, commonly referred to by the English acronym SOFC (“Solid Oxide Fuel Cell”).

[0003] A high-temperature solid oxide electrolyzer makes it possible, in particular, to transform water—more precisely water vapor (H2O)—into dihydrogen (H2) and dioxygen (O2) by means of an electric current. In a high-temperature solid oxide fuel cell, the operation is reversed: a high-temperature solid oxide fuel cell makes it possible, in particular, to produce an electric current and heat by being supplied with dihydrogen (H2) and dioxygen (O2).

[0004] As illustrated in [Fig. 1], a high-temperature solid oxide electrolyzer comprises - a plurality of electrochemical units (U), each consisting of an anode (A), a cathode (C), and an electrolyte (E) interposed between the cathode and the anode; and - a plurality of interconnectors (I). Each electrochemical unit is interposed between two interconnectors.

[0005] Each electrochemical unit corresponds to an electrolyte / electrode assembly, which is typically a multilayer ceramic assembly in which the electrolyte is formed by a central ion-conducting layer. This solid, dense, and impermeable layer is sandwiched between the two porous layers forming the electrodes, the interconnectors, typically made of metallic alloys, are electronic conductors that ensure, from an electrical standpoint, the connection of each electrochemical unit and thus the functions of supplying and collecting electrical current, and from a fluidic standpoint, the circulation of gases. It should be noted that additional layers may exist, but they serve only to provide electrical and gas supply and / or to improve the operation of one or more of the layers described above.

[0006] A high-temperature solid oxide electrolyzer is therefore an alternating stack of electrochemical units and interconnectors. A high-temperature solid oxide fuel cell comprises the same type of stack.

[0007] To ensure the proper functioning of a solid oxide stack operating at high temperature, it is necessary to maintain the stack under compression during its operation, transport, and handling. This primarily protects the stack, notably by preventing the application of tensile and shear stresses on the electrochemical units and interconnectors. It also ensures the performance of the electrolyzer or fuel cell by maintaining sufficient electrical contact and contact surface area between the electrochemical units and interconnectors. The compressive force required during handling or transport at ambient temperature may be lower than during operation at high temperature, but a compressive force is nevertheless necessary to protect the stack.

[0008] It is known to use metallic clamping systems comprising upper and lower clamping plates between which the solid oxide stack is intended to be clamped, threaded clamping rods connecting the two clamping plates, and nut-type clamping means for compressing the stack between the two clamping plates. This system, which may appear simple to implement, proves complex when the solid oxide stack operates at high temperature. At high temperature, the compressive force initially applied to the stack is indeed likely to vary significantly due to the difference in coefficient of thermal expansion between, on the one hand, the solid oxide stack, which comprises materials with a low coefficient of thermal expansion, and, on the other hand, the clamping system, which comprises metallic materials with a higher coefficient of thermal expansion.

[0009] To try to ensure stable clamping at high temperature over time, several solutions have been proposed.

[0010] US patent 6,835,486 suggests matching the coefficient of thermal expansion of certain elements of the clamping system with that of the stack at solid oxides. However, this solution only partially solves the problem. The compressive force applied to the solid oxide stack will vary depending on the coefficient of thermal expansion. A slight difference in the coefficient of thermal expansion between the materials in the clamping system will have a significant impact on the compressive force. Furthermore, the force applied to the stack will vary with the temperature, which changes over time. Therefore, it will not be possible to apply a stable compressive force over time. Finally, at high temperatures, the metallic materials of the clamping system will be subjected to fining and relaxation phenomena (at 800 °C, these fining and relaxation effects occur even in a metallic element with a low stress level – on the order of a few MPa). The compressive force will therefore decrease over time, even at a constant temperature.

[0011] The use of elastic systems, such as springs, has also been suggested to maintain a constant compressive force over time, regardless of the coefficient of thermal expansion of the clamping system. However, the use of metal springs suffers from the same drawbacks as those mentioned previously: at high temperatures, they will be subject to flexing and relaxation phenomena and will therefore lose their elasticity over time. Oversizing metal springs to maintain the level of compression also has obvious limitations due to the resulting rigidity and / or size of the system. To avoid flexing and relaxation phenomena, the use of ceramic springs is described in US patent 9,812,729. However, these springs are fragile and can only withstand a limited load.

[0012] It has also been suggested that the clamping elements be relocated outside the high-temperature environment. US patents 6,797,425 and 9,559,378 disclose clamping systems that pass through the heating chamber to avoid exposure to high temperatures. While these systems do provide stable clamping over time and temperature, they require complex systems to ensure the clamping system passes through the heating chamber. They also generate significant heat losses and temperature gradients within the chamber. Furthermore, they require the use of a separate clamping system during the transport and handling of the solid oxide stack before insertion into the heating chamber.

[0013] The invention falls within this context. Summary of the invention

[0014] The invention notably allows the implementation of a simple clamping system for a high-temperature operating solid oxide stacks that may exhibit the following attributes: - temperature stable to withstand the high-temperature operation of the stack, - stable over time to withstand the fining and relaxation phenomena that can occur at high temperatures, - autonomous to avoid the need for continuous tightening control and command systems, - of reduced size so that it can be contained entirely within the heating enclosure and avoid heat loss and temperature gradients within the enclosure.

[0015] The invention relates, according to a first aspect, to a self-contained clamping system for a solid oxide stack operating at high temperature, said self-contained clamping system comprising: - an upper clamping plate and a lower clamping plate, between which the solid oxide stack is intended to be clamped, each clamping plate comprising at least two clamping holes, - at least two clamping rods configured to extend each through a clamping hole in the upper clamping plate and through a corresponding clamping hole in the lower clamping plate to allow the upper and lower clamping plates to be joined together, - clamping means configured to cooperate with said at least two clamping rods to apply a compressive force on the solid oxide stack, said self-contained clamping system further comprising at least one self-contained, sealed bellows containing a gas, in which, the clamping means are configured to apply, in a first configuration, a first compressive force on the solid oxide stack under the effect of solid contact between the clamping plates and the solid oxide stack and, in which, at least one self-contained sealed bellows is configured to apply, in a second configuration, a second compressive force on the solid oxide stack under the effect of the pressure of the gas contained in at least one self-contained sealed bellows.

[0016] The clamping system according to the invention ensures clamping stability at temperature. At ambient temperature, the clamping system applies an initial compressive force to the solid oxide stack through direct or indirect solid contact between the clamping plates and the solid oxide stack. This initial compressive force ensures the stability of the stack during transport and handling. At high temperature, the clamping system applies a A second compressive force is exerted on the solid oxide stack by the pressure of the gas contained in at least one self-contained, sealed bellows. Thus, even though the metal clamping rods expand more than the solid oxide stack due to their generally higher coefficient of thermal expansion, the pressure of the gas contained in at least one self-contained, sealed bellows will increase with temperature and apply a compressive force to maintain the stack in compression.

[0017] The clamping system according to the invention ensures the stability of the clamping over time. The gas is not subject to the phenomena of fineness and relaxation.

[0018] The clamping system according to the invention is self-contained. The self-contained, sealed bellows containing a gas is not connected to external means for controlling and / or modifying the gas pressure, such as pneumatic means. In one embodiment, the self-contained, sealed bellows containing a gas also does not include internal means for controlling and / or modifying the gas pressure.

[0019] The clamping system according to the invention is small in size. It can be entirely contained within a heating chamber.

[0020] According to one embodiment, the ambient temperature pressure of the gas contained in the at least one self-sealing bellows is lower than atmospheric pressure. The pressure of the gas contained in the at least one self-sealing bellows is predefined at ambient temperature such that, at high temperatures (i.e., within the operating temperature range of the solid oxide stack), the pressure exerted by the gas contained in the at least one self-sealing bellows ensures compression of the stack. According to one embodiment, at ambient temperature, the pressure exerted by the gas contained in the at least one self-sealing bellows does not apply a compressive force to the stack.

[0021] According to one embodiment, at least one of the clamping plates comprises at least one recess, said at least one recess being located on a face oriented towards the solid oxide stack and opposite the solid oxide stack. In this embodiment, at least one self-contained, sealed bellows is intended to be positioned in said at least one recess. This embodiment allows the first compression force to be applied by direct solid contact between, on the one hand, the bearing surface around the at least one recess of the at least one of the clamping plates comprising at least one recess and, on the other hand, the solid oxide stack.

[0022] According to one embodiment, the depth of at least one recess is configured to correspond to the height of at least one self-contained bellows that is sealed at room temperature. A bellows is defined as an axially deformable cylindrical part closed at both ends, the lateral surface of which preferably comprises essentially a corrugated structure perpendicular to the axis of the cylinder. By bellows height, we mean the dimension of the bellows measured along the axis of the cylinder.

[0023] According to one embodiment, at least one recess is located at the center of at least one clamping plate. This embodiment ensures the application of the second compressive force at the center of the stack, which improves the electrical connection between the electrochemical units and the interconnectors of the stack.

[0024] According to one embodiment, at least one of the clamping plates comprises at least two raised features located on a face oriented towards the solid oxide stack and opposite the solid oxide stack. In this embodiment, said at least one clamping plate comprises a featureless area intended to be in contact with at least one self-sealing bellows. In this embodiment, the at least one self-sealing bellows is intended to be located in this area between said at least two raised features. This embodiment allows the first compression force to be applied by direct solid contact between, on the one hand, at least one of the clamping plates comprising the at least two raised features and, on the other hand, the solid oxide stack.

[0025] According to one embodiment, the height of the at least two reliefs is configured to correspond to the height of the at least one self-contained bellows that is airtight at room temperature.

[0026] According to one embodiment, the clamping system further comprises at least one spacer located between the solid oxide stack and one of the clamping plates. This embodiment allows the first compressive force to be applied through indirect solid contact between, on the one hand, at least one of the clamping plates and, on the other hand, the solid oxide stack, via the at least one spacer.

[0027] According to one embodiment, the self-sealing bellows comprises at least one support element configured to limit the crushing of the self-sealing bellows in the first configuration. This embodiment allows the first compression force to be applied through indirect solid contact between, on the one hand, at least one of the clamping plates and, on the other hand, the solid oxide stack, via the support element. According to one embodiment, at least one self-sealing bellows is located between one of the clamping plates and the solid oxide stack.

[0028] According to one embodiment, said at least one support element is a rigid solid. According to another embodiment, said at least one support element is a spring. According to another embodiment, said at least one support element consists of the side walls of the self-sealing bellows which have a stiffness configured to limit the crushing of the self-contained, airtight bellows.

[0029] According to one embodiment, the self-sealing bellows contains air or an inert gas such as, for example, argon, helium, or nitrogen. The use of an inert gas reduces the risk of corrosion.

[0030] According to one embodiment, the at least one self-contained, sealed bellows is a metal bellows sealed at its periphery, preferably by welding. This embodiment ensures the durability and reliability of the bellows.

[0031] According to one embodiment, the first configuration corresponds to a configuration at room temperature.

[0032] According to one embodiment, the second configuration corresponds to a high-temperature configuration. By high temperature, we mean a temperature above 650°C, typically a temperature between 700°C and 850°C.

[0033] According to one embodiment, the at least two clamping rods are threaded.

[0034] According to one embodiment, the clamping means comprise, at the level of Each clamping hole of the upper and lower clamping plates includes at least one clamping nut designed to cooperate with the clamping rods to apply a compressive force to the solid oxide stack. In one embodiment, the clamping means comprise, at each clamping hole of the upper and lower clamping plates, at least one clamping nut associated with at least one clamping washer designed to cooperate with the clamping rods to apply a compressive force to the solid oxide stack. These at least one clamping washers are located between the nuts and the clamping plates.

[0035] According to a second aspect, the invention also relates to an assembly comprising a self-contained clamping system according to the first aspect of the invention and at least one high-temperature operating solid oxide stack.

[0036] According to one embodiment, the high-temperature operating solid oxide stack comprises: - a plurality of electrochemical units, each consisting of a cathode, an anode, and an electrolyte interposed between the cathode and the anode, - a plurality of interconnectors, each arranged between two adjacent electrochemical units, - optionally, an upper terminal plate and a lower terminal plate, between which the plurality of electrochemical units and the plurality of interconnectors are enclosed.

[0037] According to one embodiment, in the first configuration each clamping plate is in direct or indirect solid contact with one of the end plates of the solid oxide stack. The transmission of the compressive force thus occurs via a succession of solid contacts between the clamping means and The solid oxide stack. The solid contact between the clamping plates and the end plates of the solid oxide stack can be direct if there is no intermediate element between the clamping plates and the end plates of the solid oxide stack. The solid contact between the clamping plates and the end plates of the solid oxide stack can also be indirect if there is an intermediate element between the clamping plates and the end plates, for example, at least one support element or at least one spacer as described previously.

[0038] The assembly may also include one or more additional plates between the clamping plates and the end plates, or between the end plates, to ensure optimal stacking performance (contact plate, insulation plate, etc.). This slight variation, which is within the grasp of a person skilled in the art, does not alter the principle of the invention in any way.

[0039] According to one embodiment, in the second configuration, at least one self-contained, sealed bellows applies a compressive force to at least one of the end plates of the solid oxide stack under the effect of the gas pressure contained in the at least one self-contained, sealed bellows. In this case, the transmission of the compressive force between the clamping means and the solid oxide stack is no longer carried out exclusively via a succession of solid contacts but also through the gas pressure contained in the at least one self-contained, sealed bellows.

[0040] The invention further relates, according to a third aspect, to a method for mounting a solid oxide stack operating at high temperature. This mounting method is implemented by a clamping system according to the first aspect of the invention. The mounting method comprises the following steps: - the insertion of at least one high-temperature operating solid oxide stack between the upper and lower clamping plates of the clamping system according to the first aspect of the invention; - tightening the clamping means of the clamping system so that the upper and lower clamping plates apply a compressive force to the solid oxide stack through solid contact between the clamping plates and the solid oxide stack; and - the high-temperature heating of the assembly comprising the clamping system and said at least one solid oxide stack, so that the at least one self-contained sealed bellows applies a second compressive force on the solid oxide stack under the effect of the pressure of the gas contained in the at least one self-contained sealed bellows.

[0041] According to one embodiment, the clamping step takes place at ambient temperature before the heating stage. BRIEF DESCRIPTION OF THE FIGURES

[0042] Features of the present invention will become clearer upon reading the following detailed description, made without limitation with reference to the accompanying drawings in which:

[0043] [Fig.1] represents a partial schematic view of a solid oxide stack illustrating the operating principle of a solid oxide electrolyzer operating at high temperature.

[0044] [Fig.2] represents a schematic cross-sectional view of an assembly comprising a clamping system and a high-temperature operating solid oxide stack according to an embodiment of the invention.

[0045] [Fig.3] represents the entire [Fig.2] at room temperature after tightening of the stack.

[0046] [Fig.4] represents the entire [Fig.2] at high temperature, after tightening the stack at room temperature.

[0047] [Fig.5] represents the entire [Fig.2] at high temperature after clamping the stack at room temperature, when the clamping system is subjected to the phenomenon of fineness and relaxation.

[0048] [Fig.6] represents a schematic cross-sectional view of an assembly comprising a clamping system and a high-temperature solid oxide stack according to an embodiment of the invention.

[0049] [Fig.7] represents the entire [Fig.6] at room temperature after tightening of the stack.

[0050] [Fig.8] represents the entire [Fig.6] at high temperature, after tightening the stack at room temperature. DETAILED DESCRIPTION OF THE INVENTION

[0051] The [Fig.1] has been described previously in the part relating to the prior art.

[0052] With reference to [Fig. 2], a cross-sectional view of an assembly 3 comprising a system clamping 1 and a solid oxide stack 2 operating at high temperature according to an embodiment of the invention is represented.

[0053] The clamping system 1 comprises an upper clamping plate 11 and a lower clamping plate 12, between which the high-temperature operating solid oxide stack 2 is intended to be clamped.

[0054] The terms "upper" and "lower" are to be understood in terms of the normal direction of orientation of a stack, a clamping system and / or an assembly according to the invention, in the configuration of use.

[0055] Each upper clamping plate 11 and lower clamping plate 12 comprises at least two clamping holes 13.

[0056] The clamping system includes at least two clamping rods 14 configured to extend each through a clamping hole in the upper clamping plate 11 and through a corresponding clamping hole in the lower clamping plate 12 to allow the upper clamping plates 11 and lower clamping plates 12 to be assembled together. The clamping rods are preferably threaded.

[0057] The clamping system includes clamping means 15 configured to cooperate with the clamping rods 14 at the clamping ports 13 to allow the application of a compressive force on the solid oxide stack 2 clamped between the upper clamping plates 11 and lower clamping plates 12.

[0058] As illustrated, the clamping means 15 preferably include at least one clamping nut at each clamping orifice 13 cooperating with the clamping rods 14. The clamping nuts at the clamping orifices of the upper clamping plate are located above the upper clamping plate and the clamping nuts at the clamping orifices of the lower clamping plate are located above the lower clamping plate.

[0059] The clamping means may also include a clamping washer at each clamping orifice between at least one clamping nut and the corresponding clamping plate.

[0060] The upper and lower clamping plates preferably have a sufficient thickness to transmit the compressive force uniformly without deformation.

[0061] The clamping system includes at least one self-contained, sealed bellows containing a gas 17. Each bellows 17 includes an upper end 171, a lower end 172 and a side wall 173.

[0062] As illustrated in [Fig.2], the self-sealing bellows 17 is located in a recess 16 of the upper clamping plate 11. The upper end 171 is in contact with the recess and the lower end 172 is in contact with the solid oxide stack 2. In this embodiment, the lower clamping plate 12 is essentially flat.

[0063] The recess 16 is located on a face oriented towards the solid oxide stack 2 and opposite the solid oxide stack. The recess 16 is preferably located in the center of the upper clamping plate 11.

[0064] A self-sealing bellows can alternatively or additionally be located in a recess in the lower clamping plate 12. An additional self-sealing bellows can also be located in an additional recess in one of the clamping plates 11, 12.

[0065] The high-temperature operating solid oxide stack 2 comprises, in addition the elements described with reference to [Fig.1], an upper terminal plate 21 and a lower terminal plate 22 between which the plurality of electrochemical units U and the plurality of interconnectors I are sandwiched.

[0066] The upper terminal plates 21 and lower terminal plates 22 preferably have a sufficient thickness to transmit the compressive force uniformly without deformation to the electrochemical units and interconnectors.

[0067] Figure 3 shows the entire assembly of Figure 2 in the first configuration, after tightening the clamping means. This first configuration corresponds to a configuration at room temperature.

[0068] Tightening the clamping means 15, in particular the clamping nuts, allows a compressive force to be applied to the high-temperature operating solid oxide stack 2.

[0069] As illustrated, in this first configuration, the clamping means allow a first compressive force to be applied to the solid oxide stack 2 through direct solid contact between the clamping plates 11, 12 and the solid oxide stack 2. Each clamping plate 11, 12 is in solid contact with one of the end plates 21, 22 of the solid oxide stack 2. Solid contact is understood to mean contact via solid elements, such that the transmission of compressive forces occurs through contacts between solid elements. The upper clamping plate 11, in particular the bearing area around the recess 16, is in direct solid contact with the upper end plate 21, and the lower clamping plate 12 is in direct solid contact with the lower end plate 22.

[0070] In the figures, compressive forces are represented by arrows. As illustrated in [Fig. 2], the clamping means 15 apply a compressive force to the clamping plates 11, 12. The lower clamping plate 12 transmits this compressive force to the lower end plate 22 by direct solid contact. The upper clamping plate 11 transmits this compressive force to the upper end plate 21 by direct solid contact, in particular by direct solid contact between the bearing area around the recess 16 and the upper end plate 21.

[0071] In the first configuration, the height of the self-sealing bellows corresponds to the depth of the recess, so that the bellows does not exert a compressive force on the stack. Alternatively, the height of the self-sealing bellows may be greater than the depth of the recess, and the bellows is compressed in the first configuration, so that the compressive force on the stack is mainly transmitted by direct solid contact between the clamping plates of the clamping system and the end plates of the stack. The height of the self-sealing bellows may also, in this configuration, be less than the depth of the emptying.

[0072] In the first configuration, at room temperature, the pressure of the gas at room temperature in the self-sealing bellows can be lower than atmospheric pressure.

[0073] The gas pressure in the self-sealing bellows is predefined at room temperature so that within the operating temperature range of the solid oxide stack, the pressure exerted by the gas ensures the compression of the stack within a predefined force range.

[0074] An example of calculating the initial pressure Pini of the gas in a self-contained, sealed bellows is given below by way of example and not limitation, based on the following assumptions: - the bellows has a force application surface Ssou / jiet, for example 250 cm2, - the minimum force to be maintained on the high-temperature stack Fmin, for example 3800 N, - the operating temperature range [Tmin - Tmax], for example 975.15 - 1073.15 K. The absolute gas pressure in the bellows at ambient temperature Tamh is determined as follows by application of the ideal gas law: Σ = constant- When the temperature reaches Tmin, the pressure in the bellows becomes p_r> .. Tmin, the force exerted by the bellows becomes *Tmin ~ 1 ini x 1 (T \ P _ Ç v ( p kz 7 nun _ pi . 7 Tmin ^ bellows X1 ini r ~ 1 atm ) The initial pressure in the bellows is predefined such that the force applied by the bellows at the minimum temperature of the operating range is equal to the minimum effort: bjnm = F min, i.e. in the example 3800 N. _ Pcanb .. / FTmin । p ) With the values ​​given as an example above, finished T . xls ni , *atm I 1 nun \ ^bellows / We obtain Pini = 76313 Pa, which is a pressure lower than atmospheric pressure.

[0075] A person skilled in the art can easily adapt the initial pressure in the self-sealing bellows according to the size of the bellows, the minimum force to be maintained at high temperature, and the high-temperature operating range. Any other suitable law can also be used by a person skilled in the art to model the gas.

[0076] Figure 4 represents the entirety of Figure 2 in the second configuration. This second configuration corresponds to a high-temperature configuration (i.e., the operating temperature of the solid oxide stack).

[0077] As illustrated, in this second configuration, the clamping means make it possible to apply a second compressive force to the solid oxide stack 2 under the effect of the pressure of the gas contained in at least one self-contained bellows Sealed 17. As detailed previously, at high temperature, the gas pressure in the self-contained, sealed bellows is greater than the pressure at ambient temperature. This pressure increase allows a compressive force to be applied to the solid oxide stack independently of the expansion of the clamping system, which is generally greater than the expansion of the stack (particularly due to the difference in coefficient of thermal expansion between, on the one hand, the solid oxide stack, which comprises materials with a low coefficient of thermal expansion, and, on the other hand, the clamping system, which comprises metallic materials with a higher coefficient of thermal expansion). More specifically, the upper end 171 of the self-contained, sealed bellows 17 is in direct solid contact with the recess 16 of the upper clamping plate 11, and the lower end 172 of the bellows 17 is in direct solid contact with the upper end plate 21.

[0078] The second compressive force is transmitted from the clamping means 15 and the clamping plates 11, 12 under the effect of the pressure of the gas contained in at least one self-sealing bellows 17, as illustrated by the arrows in [Fig. 4]. As illustrated, the clamping means 15, together with the self-sealing bellows 17, apply a compressive force to the solid oxide stack. The lower clamping plate 12 transmits this compressive force to the lower end plate 22 by direct solid contact.The upper clamping plate 11 transmits this compressive force to the upper end plate 21 via (i) direct solid contact between the upper clamping plate 11 and the upper end 171 of at least one self-sealing bellows, (ii) the pressure of the gas contained in the at least one self-sealing bellows 17 and (iii) direct solid contact between the lower end 172 of the at least one self-sealing bellows and the upper end plate 21 of the solid oxide stack 2. In this configuration, the presence or absence of direct solid contact between the upper clamping plate 11 and the upper end plate 21 is irrelevant due to the pressure of the gas contained in the at least one self-sealing bellows.

[0079] Figure 5 also represents the entire high-temperature configuration of Figure 2 under the assumption that the clamping system is subjected to the phenomena of sagging and relaxation. Under this assumption, even if there is no longer direct solid contact between the clamping plates and the stack, the second compressive force remains applied under the effect of the gas pressure contained in at least one self-sealing bellows. In particular, the second compressive force remains applied under the effect of the gas pressure contained in at least one self-sealing bellows, notably through (i) the solid contact between the upper end plate 21 of the solid oxide stack 2 and the lower end 172 of at least one self-sealing bellows 17, (ii) the gas pressure contained in the less one self-sealing bellows 17, and (iii) solid contact between the upper end 171 of at least one self-sealing bellows 17 and the upper clamping plate 11.

[0080] According to a variant conforming to this embodiment, the upper clamping plate 11 may, instead of a recess 16, comprise at least one, preferably a plurality of ridges integral with the upper clamping plate and projecting from the face of the upper clamping plate 11 oriented towards the stack. The ridges are intended to ensure direct solid contact with the stack in the first configuration. These ridges are preferably distributed over the entire surface of the upper clamping plate 11, with the exception of one or more locations intended to accommodate the self-sealing bellows. The ridges preferably extend perpendicularly to the upper clamping plate, and their contact surfaces may be of any shape. They may, for example, have point contact (the ridges being, for example, hemispherical), linear contact, or surface contact.However, any shape allowing direct solid contact with the stack can be considered. The reliefs are configured so that the contact surfaces of said reliefs are in simultaneous contact with the stack, for example with the upper end plate 21. In this case, the contact surfaces are located in the same plane, which constitutes the contact plane with the upper end plate.

[0081] In another embodiment, the upper clamping plate may be essentially flat, and at least one spacer may be placed between the flat upper clamping plate and the solid oxide stack to provide space for the self-sealing bellows. The solid contact between the upper clamping plate and the solid oxide stack in the first configuration is then indirect via the at least one spacer.

[0082] At least one spacer can alternatively or additionally be placed between the lower clamping plate 12 and the solid oxide stack 2. Similarly, the lower clamping plate can have another shape and any configuration of lower clamping plate allowing solid contact with the stack can be considered.

[0083] With reference to [Fig.6], a schematic cross-sectional view of an assembly comprising a clamping system and a high-temperature operating solid oxide stack according to another embodiment of the invention is shown.

[0084] In the example of the clamping system of [Fig.6], at least one self-sealing bellows 17 includes a support element 18 configured to limit the crushing of the self-sealing bellows 17.

[0085] In the embodiment of [Fig. 6], unlike in [Fig. 2], the self-sealing bellows 17 comprises a support element 18 and the clamping plate su The upper clamping plate 11 does not include a recess (for example, the upper clamping plate 11 is essentially flat). This embodiment simplifies the manufacture of the upper clamping plate. The self-sealing bellows 17 is located between the upper clamping plate 11 and the upper end plate 21 of the stack. One end 171 of the self-sealing bellows is in contact with the upper clamping plate 11, and the other end of the bellows is in contact with the upper end plate 21. Alternatively, the self-sealing bellows can be positioned between the lower clamping plate 12 and the lower end plate 22. Multiple self-sealing bellows can also be provided between the clamping plates and the end plates.

[0086] The support element 18 can be a rigid solid such as a support foot or a spring. The support element is configured to limit the crushing of the self-sealing bellows. In particular, the support element is configured to limit the crushing of the self-sealing bellows in the direction of the cylinder axis, corresponding to the axis of the solid oxide stack. As illustrated in Figures 6 to 8, the support element 18 can be attached to one end of the self-sealing bellows 17.

[0087] Thus, in the first configuration (at room temperature), as illustrated in [Fig. 7], a first compressive force is applied to the solid oxide stack 2 by means of solid contact between the clamping plates 11, 12 and the solid oxide stack 2. In particular, the first compressive force is applied by means of indirect solid contact between the upper clamping plate 11 and the upper end plate 21, and direct solid contact between the lower clamping plate 12 and the lower end plate 22. The indirect solid contact between the upper clamping plate 11 and the upper end plate 21 is achieved through a chain of solid contacts via the support element 18. Each clamping plate is thus in solid contact, direct or indirect, with one of the end plates of the solid oxide stack.The contact between the upper clamping plate 11 and the upper end plate 21 is made via the ends of the self-sealing bellows 171, 172 and the support element 18.

[0088] In the second configuration, illustrated in [Fig. 8], a compressive force is applied to the solid oxide stack 2 under the effect of the gas pressure in at least one self-sealing bellows 17. As illustrated, there is no longer any solid contact between at least one end of the self-sealing bellows and the support element: the compressive force is transmitted via the gas pressure contained in at least one bellows. Indeed, as detailed previously, at high temperature, the gas pressure in the self-sealing bellows is greater than the pressure at ambient temperature. This pressure increase allows maintain a compressive force on the solid oxide stack independently of the expansion of the clamping system which is greater than the expansion of the stack. More specifically, one end 171 of the self-sealing bellows 17 is in direct solid contact with the upper clamping plate 11 and the second end 172 of the self-sealing bellows 17 is in direct solid contact with the upper end plate 21. The second compressive force is transmitted from the clamping means and the clamping plates under the effect of the pressure of the gas contained in at least one self-sealing bellows 17, as illustrated by the arrows in [Fig. 8].

[0089] A method for mounting a high-temperature solid oxide stack according to an embodiment of the invention is described above.

[0090] According to this method, at least one high-temperature operating solid oxide stack 2 is inserted between the upper clamping plates 11 and lower clamping plates 12 of the clamping system 1, with at least one self-sealing bellows 17 between one of the clamping plates and the stack. Thus, the at least one self-sealing bellows 17 is to be positioned at the time of stack insertion.

[0091] The method also includes a tightening step of the clamping means 15 of the clamping system 1 such that the upper clamping plates 11 and lower clamping plates 12 apply a compressive force to the solid oxide stack 2 through solid contact between the clamping plates and the solid oxide stack. The tightening step is performed by tightening a clamping nut cooperating with the threaded clamping rods. Optionally, the tightening can be carried out in two stages: tightening by external loading followed by maintaining the clamping force using the clamping means. This tightening ensures the stability of the assembly during transport and handling within the heating chamber for high-temperature operation of the solid oxide stack.

[0092] The method also includes a high-temperature heating step of the assembly 3 comprising the clamping system 1 and said at least one solid oxide stack 2 so that the stack can function. During the heating step, the gas pressure in the at least one self-sealing bellows increases so that, at high temperature, the at least one self-sealing bellows 17 applies a second compressive force on the solid oxide stack 2 under the effect of the gas pressure contained in the at least one self-sealing bellows.

[0093] The present invention has been described and illustrated in this detailed description with reference to the accompanying figures. However, the present invention is not limited to the embodiments shown. Other variations, embodiments, and combinations of features can be deduced and implemented by a person skilled in the art upon reading this description and the accompanying figures.

[0094] To satisfy specific needs, a person competent in the field of the invention may apply modifications or adaptations.

[0095] The various features presented and / or claimed can be advantageously combined. Their presence in the description or in different dependent claims does not preclude the possibility of combining them. The reference symbols should not be construed as limiting the scope of the invention.

Claims

Demands

1. A self-contained clamping system (1) for a high-temperature operating solid oxide stack (2), said self-contained clamping system comprising: - an upper clamping plate (11) and a lower clamping plate (12), between which the solid oxide stack (2) is intended to be clamped, each clamping plate (11, 12) comprising at least two clamping holes (13), - at least two clamping rods (14) configured to extend each through a clamping hole (13) of the upper clamping plate (11) and through a corresponding clamping hole (13) of the lower clamping plate (12) to allow the upper and lower clamping plates (11, 12) to be assembled together, - clamping means (15) configured to cooperate with said at least two clamping rods (14) to apply a compressive force to the solid oxide stack (2), characterized in that the self-contained clamping system (1) comprises at least one self-contained, sealed bellows (17) containing a gas, in that the clamping means are configured to apply, in a first configuration, a first compressive force to the solid oxide stack under the effect of solid contact between the clamping plates and the solid oxide stack, in that the at least one self-contained, sealed bellows is configured to apply, in a second configuration, a second compressive force to the solid oxide stack (2) under the effect of the pressure of the gas contained in the at least one self-contained, sealed bellows, and in that at least one of the clamping plates (11) comprises at least one recess (16) and a bearing surface around the recess (16), the recess (16) being located on a face oriented towards, and opposite, the solid oxide stack (2), at least one self-contained sealed bellows (17) being intended to be located in the recess (16), so that, in the first configuration, said first compression force is applied under the effect of solid contact between the bearing surface and the solid oxide stack (2).

2. A self-contained clamping system (1) according to claim 1, wherein the ambient temperature pressure of the gas contained in the at least The self-contained, airtight bellows is below atmospheric pressure.

3. Self-contained clamping system (1) according to claim 1 or 2, wherein the self-contained sealed bellows includes a support element (18) configured to limit the crushing of the self-contained sealed bellows in the first configuration.

4. Self-contained clamping system (1) according to any one of claims 1 to 3, wherein at least one of the clamping plates comprises a plurality of reliefs located on a face oriented towards the solid oxide stack (2) and opposite the solid oxide stack, and wherein said at least one clamping plate comprises a location without reliefs intended to be in contact with the at least one self-contained sealed bellows.

5. Self-contained clamping system (1) according to any one of claims 1 to 4, comprising at least one spacer between the solid oxide stack and one of the clamping plates, the solid contact between said clamping plate and the solid oxide stack being ensured via said at least one spacer.

6. Self-contained clamping system (1) according to any one of claims 1 to 5, wherein at least one self-contained sealed bellows (17) contains air or an inert gas such as, for example, argon, helium or nitrogen.

7. Self-contained clamping system (1) according to any one of claims 1 to 6, wherein the at least one self-contained sealed bellows (17) is a metal bellows sealed at its periphery, preferably by welding.

8. Self-contained clamping system (1) according to any one of claims 1 to 7, wherein the first configuration corresponds to a room temperature configuration and the second configuration corresponds to a high temperature configuration.

9. Assembly (3) comprising a self-contained clamping system (1) according to any one of claims 1 to 8 and at least one high-temperature operating solid oxide stack (2).

10. Assembly (3) according to claim 9, wherein the solid oxide stack (2) comprises: - a plurality of electrochemical units (U), each formed of a cathode (C), an anode (A), and an electrolyte (E) intercalated between the cathode and the anode, - a plurality of interconnectors (I), each arranged between two units adjacent electrochemical cells, - optionally, an upper terminal plate (21) and a lower terminal plate (22), between which the plurality of electrochemical units and the plurality of interconnectors are enclosed.

11. Assembly (3) according to claim 10, in which - in the first configuration, each clamping plate (11, 12) is in solid contact with one of the end plates of the solid oxide stack (21, 22), and - in the second configuration, the self-contained sealed bellows (17) applies a compressive force on at least one of the terminal plates of the solid oxide stack (21, 22) under the effect of the pressure of the gas contained in at least one self-contained sealed bellows.

12. A method for assembling a high-temperature operating solid oxide stack (2), comprising the following steps: - the insertion of at least one high-temperature operating solid oxide stack (2) between the upper and lower clamping plates (11, 12) of a clamping system (1) according to any one of claims 1 to 8; - tightening the clamping means (15) of the clamping system (1) so that the upper and lower clamping plates (11, 12) apply a compressive force to the solid oxide stack (2) through solid contact between the clamping plates and the solid oxide stack; and - the high-temperature heating of the assembly (3) comprising the clamping system (1) and said at least one solid oxide stack (2), so that the at least one self-contained sealed bellows (17) applies a second compressive force on the solid oxide stack (2) under the effect of the pressure of the gas contained in the at least one self-contained sealed bellows.

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