FR3112656A1 - ELECTROCHEMICAL DEVICE - Google Patents

Abstract

The invention relates to an electrochemical device (100) comprising:- a solid oxide stack (200);- two clamping plates gripping the stack (200);- two clamping rods (60) each extending from a first orifice (51) to a second orifice (52), respectively of the first and of the second plate; at least one clamping rod, comprises, in its volume, a recess forming a duct (80) allowing the distribution or the evacuation of at least one gas from the stack (200), said duct (80) extends from the first to the second plate (310) so that the heat produced by the stack (200) allows, by radiation , a heating of the gas circulating in the said primary conduit (80), the recess being made in such a way as to impose on a gas capable of circulating in the primary conduit (80) a path of a length greater than the spacing between the two clamping plates. Figure for abstract: Figure 6.

Description

ELECTROCHEMICAL DEVICE

The present invention relates to the general field of electrochemical devices provided with at least one solid oxide electrochemical cell operating at high temperature.

The present invention relates in particular to an electrochemical device comprising at least one electrochemical cell sandwiched between two clamping plates, held by the clamping rods.

In particular, the clamping rods comprise a gas circulation duct intended to be distributed at the level of the at least one electrochemical cell and thus allow overheating or preheating of said gas. The circulation duct, according to the present invention, is in particular arranged so that the residence time of the gas in the duct is greater than the spacing between the two clamping plates. The duct may, in this respect, be of helical shape. Such an arrangement thus makes it possible to improve the efficiency of the heat exchange likely to occur between the gas and the heat produced by the at least one electrochemical cell.

PRIOR ART

FIG. 1 represents an electrochemical device 100 known from the state of the art and described in document [1] cited at the end of the description.

The electrochemical device comprises a stack 200 of solid oxides operating at high temperature enclosed in two clamping plates 300 and 310 able to operate either in electrolyser mode or in fuel cell mode. Clamping rods, extending between the two clamping plates, are also implemented in order to maintain the clamping of the stack by the clamping plates.

The electrochemical device 100 is generally referred to by one or other of the acronyms "SOEC" ("Solid Oxide Electrolyser Cell") or "SOFC" ("Solid Oxide Full Cell") when it operates, respectively, in electrolyser mode or in fuel cell mode.

The stack 200, as illustrated in FIG. 2, comprises a stack 200 of elementary electrochemical cells 210 between which are interposed interconnectors 230 intended to ensure electrical contact between the elementary electrochemical cells. These interconnectors also include channels allowing the evacuation and/or the distribution of gas at the level of the elementary cells.

Each elementary electrochemical cell comprises an electrolyte 210e interposed between an anode 210a and a cathode 210c.

Throughout the description of the present application, by "anode", "cathode" and "electrolyte" is meant elements of generally flat shape, for example in the form of a layer, which comprise two essentially parallel main faces and connected by an outline.

The anode and the cathode of each elementary electrochemical cell generally comprise a porous layer, while the electrolyte forms a dense and tight layer.

Each interconnector arranged on either side of an electrochemical cell forms, respectively, with the anode an anode compartment 230a for gas distribution and collection, and with the cathode a cathode compartment 230c for gas distribution and collection.

In operation, the anode and the cathode are the site of electrochemical reactions, while the electrolyte allows the transport of ions from the cathode to the anode, or vice versa depending on whether the electrochemical device operates in electrolyser mode or in battery mode. fuel.

Thus in electrolyser mode, the cathode compartment allows a supply of water vapor and an evacuation of the water reduction products, in particular hydrogen, while the anode compartment ensures, via a draining gas, the evacuation of the dioxygen produced from the oxidation of O ^2- ions migrating from the cathode to the anode.

The mechanism of electrolysis (“SOEC” mode) of water vapor by an elementary electrochemical cell is illustrated in figure 3. During this electrolysis, the elementary electrochemical cell is powered by a current flowing from the cathode to the 'anode. The water vapor distributed by the cathode compartment is then reduced under the effect of the current according to the following half-reaction:
[Math 1]
2 H ₂ O + 4 e ^- → 2 H ₂ + 2 O ^2- .
The dihydrogen produced during this reaction is then evacuated, while the O ^2- ions produced during this reduction migrate from the cathode to the anode, via the electrolyte, where they are oxidized to dioxygen according to the half-reaction:
[Math 2]
2 O ^2- → O ₂ + 4 e ^- .
The oxygen thus formed is evacuated by the draining gas circulating in the anode compartment.

The electrolysis of water vapor responds to the following reaction:
[Math 3]
_2H2O → _2H2 + _O2 .
In fuel cell (“SOFC”) mode, air is injected into the cathode compartment where the oxygen is then reduced to O ^2- ions. These O ^2- ions then migrate towards the anode and react with dihydrogen circulating in the anode compartment to form water.

Operation in fuel cell mode allows the production of an electric current.

The optimization of the operation of such an electrochemical device known from the state of the art may however require certain constraints.

In particular, it is necessary to have an electrical insulation between two successive interconnectors under penalty of short-circuiting the elementary electrochemical cell, but also a good electrical contact and a sufficient contact surface between an elementary electrochemical cell and an interconnector. The lowest possible ohmic resistance is then sought between cells and interconnectors. This depends on the facing materials but also on the level of tightness of the stack.

In addition, it is necessary to have a seal between the anode and cathode compartments under penalty of having a recombination of the gases produced leading to a drop in efficiency and especially the appearance of hot spots damaging the stack. Again, this tightness depends on the design of the joints and the materials used, but also on the level of tightness of the stack.

Finally, it is preferable to have a good distribution of the gases both at the inlet and at the recovery of the products, under penalty of loss of yield, of inhomogeneity of pressure and temperature within the various elementary electrochemical cells, even of prohibitive degradations. of said cells.

It is also noteworthy that injection of gases at high temperature, in particular between 600°C and 1000°C, both in electrolysis mode and in fuel cell mode, has a definite advantage.

The gases entering and leaving the SOEC or SOFC high-temperature solid oxide stack can be heated prior to their injection into said stack, in particular with a furnace as shown in Figure 4.

In this respect, the furnace 10 comprises cold parts PF and hot parts PC, the latter comprising the furnace floor 11, a loop tube 12 to manage the gas inlets and outlets of the electrochemical device.

There are then two main techniques for superheating the inlet gases in a high temperature electrolysis (SOEC) or fuel cell stack (SOFC).

As shown schematically in Figure 4, it is possible to arrange a tube loop 12 wound in line with the heating resistors of the oven 10 in its hot part PC.

The gases are then heated beforehand to a temperature close to approximately 500° C. at the outlet of the exchangers, and then circulate in the loop tube 12 in order to be exposed to the radiation of the heating resistors. This exposure to radiation results in overheating of the gases to a temperature of around 300°C before they are injected into the solid oxide stack.

Alternatively, it is possible to pass the gases through an electric heater 30 (FIG. 5) which comprises an inertial mass 31 made of steel, a heating resistor 32 and a gas conduit tube 33 wound on the inertial mass 31. A such an electric heater 30 makes it possible to bring the incoming gases GE from 20° C. to a temperature of approximately 800° C. before their introduction (outgoing gases GS) into the solid oxide stack.

However, these two techniques require the adjustment of the gas temperature in a very precise way in order to ensure the proper functioning of the electrochemical device.

Furthermore, the implementation of overheating according to the principle shown in Figure 4 requires the use of a complicated assembly due to the presence of windings, and in particular a bending of the tubes in a loop. The looped tubes increase the volume of the device accordingly, and also generate difficulties with regard to the overall assembly of the device (passage of current leads, thermocouples, etc.).

In addition, the loop tube may require costly and time-consuming treatment to avoid pollution due to its oxidation.

The technique implemented in Figure 5, on the other hand, presents a size that is not compatible with the current trend of proposing increasingly compact systems.

Various alternatives to these overheating modes have therefore been proposed. The latter implement, in general, a superheating of the gases closer to the stack in order to make better use of the heat produced, and therefore radiated, by the stack 200.

It is thus possible, as described in document [2] cited at the end of the description, to provide a heat exchange channel in one and/or the other of the clamping plates. This configuration thus makes it possible to expose the gas flowing in said channel, and before its injection into the stack 200, to the heat likely to be produced by said stack 200. This positioning as close as possible to the heat source formed by the stacking gives the electrochemical device improved thermal efficiency.

In a complementary or alternative manner, and as proposed in document [3] cited at the end of the description, hollow clamping rods holding the clamping plates can also be integrated into the gas circulation means. These clamping rods, in fluidic connection with one of the clamping plates, notably play the role of heat exchangers. In particular, the heat produced by the stack 200 allows by radiation to overheat the gas flowing in said rods, before its injection at the level of the stack 200.

However, the hollow rod portion at which the overheating of the gas is effective has a length, called exchange length, limited to the spacing between the two clamping plates. This exchange length is insufficient to ensure optimal superheating of the gas.

Thus, and still in document [3], it is also proposed to implement twisting means, and more particularly a twisted ribbon ("Swirl" according to Anglo-Saxon terminology), in order to increase, for a flow rate equivalent (while limiting the pressure drops), the residence time of the gas circulating in the clamping rods.

This latter configuration may, however, require the hollow clamping rods to have a sufficient section to resist creep in the face of the temperature likely to be imposed by the electrochemical stack. This creep is also exacerbated by the tension imposed on the tightening rods when tightening them cold.

In addition, the assembly of "Swirls" in the clamping rods remains complicated to implement.

The object of the invention is to propose an electrochemical device for which the superheating of the gases is improved.

In particular, the aim of the invention is to propose clamping rods allowing optimized overheating of the gases, and having resistance to creep adapted to their implementation in an electrochemical device, and more particularly in the electrochemical device described in the document [1 ] quoted at the end of the description.

The invention also aims to propose an electrochemical device provided with clamping rods whose formation is simplified with regard to the clamping rods known from the state of the art.

The aims of the invention are, at least in part, achieved by an electrochemical device comprising:
- a SOEC/SOFC type solid oxide stack operating at high temperature and comprising at least one elementary electrochemical cell;
- a clamping system provided with two clamping plates called, respectively, first plate and second plate, and between which the stack is clamped, each of the clamping plates comprising two essentially parallel main faces and connected by a lateral surface, each plate clamping further comprising at least two orifices, said clamping orifices;
- at least two clamping rods which each extend from a clamping orifice, said first orifice, of the first plate towards a clamping orifice, said second orifice, of the second plate so as to maintain the clamping of the stacking by clamping plates;
at least one clamping rod among the at least two clamping rods, called the duct rod, comprises, in its volume, a recess forming a primary duct in fluidic connection at one of its ends, called the first end, with a secondary duct formed in the volume of the first clamping plate, so as to allow the distribution of at least one gas in the stack, said primary duct extends from the first towards the second plate so that the heat produced by the stack allows, by radiation, a heating of the gas circulating in the said primary conduit, the recess being made in such a way as to impose on a gas capable of circulating in the primary conduit a path of a length greater than the spacing between the two clamping plates.

According to one mode of implementation, the recess is formed around an axis of revolution of the first rod.

According to one mode of implementation, the recess follows a helical path.

According to one mode of implementation, the conduit rod comprises a gas inlet end to be preheated and a gas outlet end preheated and in fluid communication with the clamping plate.

According to one embodiment, the conduit rod comprises a radial conduit providing fluid communication between the primary conduit and the secondary conduit, the secondary condition being arranged to ensure the distribution of gas from the primary conduit to the stack.

According to one mode of implementation, the radial duct is formed in a section of the duct rod housed in the first orifice, the radial duct extends in a direction perpendicular to a direction of extension of the duct rod and is extended by a section, called the first secondary section of the secondary duct.

According to one mode of implementation, the secondary duct comprises another section, called the second secondary section, which extends perpendicular to the first secondary section.

According to one mode of implementation, the first plate comprises a channel, called mounting channel opening at the level of the side surface and of the first orifice and in alignment with the first secondary section, advantageously the mounting channel and the first secondary conduit s extend on either side of the radial duct and are in fluid communication with said radial duct.

According to one mode of implementation, a plugging pin forming a keying element is inserted into the mounting channel.

According to one mode of implementation, the duct rod comprises an alignment means intended to cooperate with the plugging pin in order to impose the alignment of the radial duct and the first secondary duct.

According to one mode of implementation, each of the at least two clamping rods is welded at the level of exposed main faces, called first exposed face and second exposed face, respectively, of the first plate and of the second plate.

According to one mode of implementation, the at least two clamping rods are each assembled in a removable manner to the first and to the second plate.

According to one mode of implementation, the secondary duct comprises a so-called exchange duct section allowing the gas flowing in said channel to undergo additional overheating by means of the heat likely to be produced by the solid oxide stack of of the SOEC/SOFC type, the exchange duct comprises at least one section which extends in a direction parallel to the main faces.

According to one mode of implementation, the exchange conduit comprises two heat exchange sub-channels formed in two volume sections of the first plate, plumb with one another in a direction perpendicular to the main faces , a passage hole being formed between the two volume sections communicating the two heat exchange sub-channels.

According to one mode of implementation, two terminal plates called, respectively, first terminal plate and second terminal plate, interposed, respectively, between the first plate and the stack on the one hand, and the second plate and the stack of on the other hand, advantageously, the end plates are adapted to electrically insulate the clamping plates from the stack.

According to one mode of implementation, the first plate comprises a heating element intended to heat the gas capable of flowing in the secondary conduit, advantageously, the heating element comprises an electrical resistor.

According to one mode of implementation, the at least one elementary electrochemical cell is formed of an electrolyte interposed between two electrodes of different type called respectively anode and cathode

According to one mode of implementation, the clamping plates are made of refractory austenitic steel, in particular of the AISI 310 type.

According to one mode of implementation, the clamping plates each have a thickness of between 20 and 30 mm, in particular of the order of 25 mm.

Other characteristics and advantages will appear in the following description of an electrochemical device, given by way of non-limiting examples, with reference to the appended drawings in which:

shows, in a perspective view, an electrochemical device known from the state of the art (document [1]), and on which the present invention is likely to be implemented;

is an exploded schematic view of a stack of two basic electrochemical cells known from the state of the art and capable of being implemented within the scope of the present invention;

is a schematic view showing the principle of operation of an elementary electrochemical cell in high temperature solid oxide electrolyser (SOEC) mode, the arrows represent the circulation of gases at the level of the electrodes, in particular the arrows in solid lines represent the circulation of reactive gas or reaction product, while the arrow in broken lines represents the circulation of draining gas;

illustrates the principle of the architecture of a furnace on which a stack of high temperature electrolysis (SOEC) or fuel cell (SOFC) operating at high temperature is placed;

illustrates the principle of an electric gas heater according to the prior art;

is a schematic and partial illustration of an electrochemical device according to a first embodiment of the present invention, the electrochemical device is in particular illustrated according to a section plane perpendicular to a clamping plate and passing through an axis of revolution of one of the clamping rods, Figure 6 illustrates in particular the clamping according to a first variant;

is a schematic and partial illustration of an electrochemical device according to the first embodiment of the present invention, the electrochemical device is in particular illustrated according to a section plane perpendicular to a clamping plate and passing through an axis of revolution of one of the clamping rods, Figure 7 illustrates in particular the clamping according to a second variant;

is a partial schematic illustration in perspective of an electrochemical device according to a second embodiment of the present invention;

is a schematic representation of a clamping plate according to a broken section with secant planes and in perspective of the first clamping plate according to the second embodiment of the present invention;

are schematic representations of a clamping rod capable of being implemented in the present invention, in particular FIG. 10a is a representation in transparency while FIG. 10b is a representation according to a longitudinal section plane of said rod.

DETAILED DISCUSSION OF PARTICULAR EMBODIMENTS

The present invention proposes an electrochemical device 100 provided with a stack formed of at least one elementary solid oxide electrochemical cell sandwiched between two clamping plates.

In this respect, an elementary electrochemical cell comprises an electrolyte interposed between an anode and a cathode.

By "clamping plate" is meant a plate of generally flat shape, which comprises two main faces connected by a lateral surface, and which when assembled in pairs are intended to maintain the cohesion of a stack of at least an elementary electrochemical cell.

The clamping plates are additionally held tight against the stack by at least two clamping rods.

The electrochemical device also comprises at least one heat exchange means for preheating or superheating gases intended to be distributed or evacuated from the stack.

According to the present invention, a heat exchange means comprises in particular a primary duct formed by a recess in one of the clamping rods and in which a gas is able to circulate before its distribution or after its evacuation from the stack.

The proximity of the clamping rod and the stack makes it possible in particular to preheat or superheat a gas flowing in the primary duct by radiating the heat likely to be produced by the stack.

The recess extends in the clamping rod between the two clamping plates, and is made in such a way as to impose on a gas capable of circulating in the primary duct a path of a length greater than the spacing between the two plates Clamping.

This last aspect makes it possible to increase the exposure time of the gas flowing in the primary duct to the thermal radiation from the stack.

It is also understood that the clamping rod is formed in one piece, and that the recess alone imposes its shape on the duct without resorting to an additional part or element. Such a clamping rod can be formed using an additive manufacturing process, and in particular 3D manufacturing, and therefore requires no assembly.

Figures 6 and 7 are illustrations of an electrochemical device 100 according to a first embodiment of the present invention.

The electrochemical device 100 according to the present invention is intended to be implemented for high temperature electrolysis (“SOEC” mode) or as a fuel cell (“SOFC” mode).

The electrochemical device 100 comprises a solid oxide stack 200 of the SOEC/SOFC type operating at high temperature (FIGS. 1 and 2);

The stack 200 notably comprises at least one elementary electrochemical cell 210.

The at least one elementary electrochemical cell may in particular comprise, in order, a cathode 210c, an electrolyte 210e, and an anode 210a.

It is understood, without it being necessary to specify, that "the cathode", "the anode" and "the electrolyte" are generally flat in shape, for example in the form of layers, and comprise two essentially parallel main faces. and connected by an outline.

In other words, an elementary electrochemical cell 210 is an assembly of ceramic layers, in particular an anode, an electrolyte and a cathode. The electrolyte in this regard comprises a solid and dense ion-conducting layer, while the anode and cathode are porous layers.

The stack 200 can also comprise intermediate interconnectors 230, each of the intermediate interconnectors 230 being interposed between two adjacent elementary electrochemical cells 210 (FIG. 2).

The intermediate interconnectors 230 provide an electrical connection between the cathode and the anode of two adjacent elementary electrochemical cells 210.

The intermediate interconnectors also delimit fluidic compartments at the level of the surface of the electrodes with which they are in contact.

In particular, the face of an intermediate interconnector 230 in contact with an anode 210a of an elementary electrochemical cell 210 delimits a compartment called anode compartment 230a.

Equivalently, the face of an intermediate interconnector 230 in contact with a cathode 210c of an elementary electrochemical cell 210 delimits a compartment called cathode compartment 230c.

Each of the anode 230a and cathode 230c compartments allows the circulation of gas, in particular for the distribution and collection of said gases.

More particularly, in the context of an implementation of the electrolysis of water, the cathode compartment 230c ensures, at the level of the cathode, a distribution of water vapor and allows the evacuation of dihydrogen, while the anode compartment 230a ensures, at the anode, the circulation of a draining gas and the evacuation of oxygen.

The electrochemical device 100 can also comprise end plates 240a and 240b arranged on either side of the stack 200 (FIG. 1).

The assembly comprising the stack 200 and the end plates 240a and 240b can be crossed by metal gas distribution and evacuation tubes (not shown).

In particular, the metal tubes can comprise two gas distribution tubes, called the anode distribution tube and the cathode distribution tube, for the distribution of gas, respectively, in the anode compartments 230a and the cathode compartments 230c.

Equivalently, the metal tubes can comprise two gas evacuation tubes, called anode evacuation tube and cathode evacuation tube, for the evacuation of gas, respectively, from anode compartments 230a and cathode compartments 230c.

The electrochemical device 100 also comprises a clamping system provided with two clamping plates, respectively called first plate 300 and second plate 310 (FIG. 1).

Each clamping plate comprises two essentially parallel main faces connected by a side surface. In particular, the first plate 300 and second plate 310 are each in contact with the stack by one of their main faces called, respectively, first internal face 300a and second internal face 310a (the other main face, respectively, of the first plate 300 and the second plate 310, is named first exposed face 300b and second exposed face 310b).

The clamping plates can be made of refractory austenitic steel, in particular of the AISI 310 or Inconel 600 type. Alloyed stainless steels are particularly advantageous because they have excellent resistance to high temperatures. These steels are particularly very resistant to creep and deformation, and are resistant to environmental attacks.

Each clamping plate comprises at least two clamping holes, for example four clamping holes 51 and 52 (Figure 1, 6, 7). In particular, the clamping orifices pass through and open at one and the other of the main faces of the clamping plate on which they are formed. Each clamping orifice is in particular delimited by an internal surface which can for example be of cylindrical shape.

The clamping holes are arranged in pairs of holes. More particularly, each pair of clamping orifices comprises a clamping orifice of one and the other of the first 300 and of the second 310 plate called, respectively, first clamping orifice 51 and second clamping orifice 52 and corresponding to each other.

By “in correspondence of one another”, is meant two orifices of one and the other of the first and of the second clamping plate aligned in a direction perpendicular to the main faces of the clamping plates.

The clamping plates 300, 310 can each have a thickness of between 20 and 30 mm, in particular of the order of 25 mm.

The clamping system further comprises at least two clamping rods 60 (Figures 10a and 10b), for example four clamping rods as shown in Figures 1 and 8.

In particular, each clamping rod 60 is associated with a pair of clamping holes, and extends through one and the other of the first 51 and the second 52 clamping hole of said pair of clamping holes. .

The clamping system may also comprise clamping means cooperating with each of the clamping rods 60 so as to hold the clamping plates 300 and 310 tight against the stack 200.

According to a first alternative, the clamping means are adapted to allow dismantling of the assembly formed by the clamping plates and the stack.

In particular, the clamping means cooperating with a given clamping rod may comprise a first clamping nut 71 and a second clamping nut 72 at the level, respectively, of the first orifice and of the second orifice through which the rod in question passes. The clamping rod comprises in this respect threaded sections at each of its ends, and intended to cooperate with one and the other of the first 71 and the second 72 clamping nut (Figure 6).

It is also possible to combine one and/or the other of the first 71 and the second 72 clamping nut with a clamping washer. In particular, a washer can be inserted between the first clamping nut 71 and the first plate 300 and/or the second clamping nut 72 and the second clamping plate 310.

According to a second alternative, the clamping means may involve the formation of one or more weld beads 73 intended to secure each clamping rod at the orifices through which it passes (FIG. 7). The weld bead(s) can be formed by an arc welding process with a non-fusible electrode of the TIG type (for "Tungsten Inert Gas" in English) or any other welding process.

In general, the clamping means can also be arranged to provide sealing at the interface between the clamping rod and the internal wall of the orifices through which it passes. In particular, the first variant can implement a seal 74 (another sealing means, for example a seal, can also be implemented between the nut 71 and the plate 300), while the second variant can implement two weld beads on either side of the clamping plate.

The electrochemical device 100 comprises at least one heat exchange means suitable for preheating or superheating a gas intended to be distributed or evacuated from the stack.

In this respect, a heat exchange means according to the present invention comprises in particular a primary conduit 80 formed by a recess in the volume of one of the clamping rods, and in fluid connection with a secondary conduit formed in the volume of the first clamping plate 300.

The recess extends in particular at least from the first plate 300 towards the second plate 310 so that the heat produced by the stack in operation allows, by radiation, a heating of a gas circulating in the primary circuit. The recess is also made in such a way as to impose on a gas capable of circulating in the primary duct a path of a length greater than the spacing between the two clamping plates 300, 310. Such an arrangement of the recess allows to increase, for the same flow rate, the residence time of the fluid for a given rod length.

According to a particularly advantageous aspect, the recess is formed around an axis of revolution of the clamping rod in question, and can be more particularly helical. This last arrangement makes it possible in particular to limit pressure drops during the circulation of a gas in the main conduit 80.

The fluidic communication between the primary duct 80 and the secondary duct 90 can in particular be ensured by a radial duct 81. In this respect, as illustrated in FIGS. 6 and 7, the radial duct 81 is formed in a section of the tightening housed the first orifice 51. In particular, the radial duct 81 can extend in a direction perpendicular to a direction of extension of the duct rod.

The secondary circuit 90 can comprise two sections, respectively called first secondary section 91 and second secondary section 92. 51 through which the clamping rod 60 passes. The second secondary section 92, perpendicular to the first secondary section 91, provides fluid communication with one of the gas distribution or evacuation tubes of the stack.

The first plate 310 may also include a channel, called mounting channel 93 opening out at the level of the side surface and the internal surface of the first orifice 51. In particular, the mounting channel 93 is in alignment with the first secondary conduit 91. According to the example of Figures 6 and 7, the mounting channel 93 and the first secondary section can be formed by machining, in particular by drilling using a drill bit.

Advantageously, a plugging element 94, forming a keying element, is inserted at least into the mounting channel 93. This plugging element 94 can be positioned after inserting the clamping rod 60 into the first clamping orifice 51 It can be attached welded in the mounting channel for example by an arc welding process with a non-fusible electrode of the TIG type (for “Tungsten Inert Gas” in English) or any other welding process.

Furthermore, the clamping rod may comprise an alignment means, in particular a groove 62, intended to cooperate with the plugging element in order to impose the alignment of the radial duct and of the first secondary duct when the rod is mounted. Clamping.

Thus, the at least one heat exchange means described above can be implemented for preheating or superheating gases intended to be distributed at the anodes (or cathodes).

In particular, the at least one heat exchange means may comprise four heat exchange means. In particular, the at least one heat exchange means may comprise two distribution heat exchange means and two evacuation heat exchange means. The two distribution heat exchange means can in particular be arranged to superheat the gases intended to be distributed at the level, respectively, of the anodes and the cathodes. Equivalently, the two evacuation heat exchange means can in particular be arranged to superheat the gases intended to be evacuated, respectively, from the anodes and the cathodes.

It is thus understood that each heat exchange means is formed in a clamping rod which is specific to it, and is associated with a secondary duct which is different from one means to another. Thus, in operation, and as illustrated in FIG. 7 by the arrows symbolizing the flow of the gas intended to be distributed (for example at the level of the anodes), said gas is injected at the level of an inlet 61 of the primary conduit 80. The latter therefore flows, in order, in the primary conduit 80, the radial conduit 81, the first secondary section 91 and the second secondary section 92, and is finally distributed at the level of the anodes via the anode distribution tube. During its flow, in the primary pipe 80, the gas undergoes heating by radiating the heat produced by the stack 200.

It is understood that a gas intended to be evacuated circulates in one of the evacuation heat exchange means in the opposite direction. In other words, the latter flows, in order, in the second secondary section, the first secondary section, radial duct, and the primary duct.

A clamping rod provided with a primary duct according to the terms of the present invention can be manufactured by an additive manufacturing technique, and in particular by 3D printing. 3D printing includes in particular sequences of material deposition, fusion of the latter by adding heat (for example with a laser, using a heating resistor, an electron beam, or even heating UV), and finally solidification of the molten material by cooling. The formation of the clamping rod by 3D printing is therefore carried out layer by layer. At the end of this printing phase, a drying step is generally carried out. The clamping rod can then undergo a heat treatment intended to improve its hardness or mechanical strength.

Furthermore, the clamping rods can be dimensioned so as to exert a constant force and in a wide temperature range. More particularly, the clamping rods can be sized to withstand creep at high temperature. In this regard, the inventors have been able to observe that the creep of a clamping rod, made of refractory austenitic steel of the AISI 310 type and whose main duct follows a helical path, has a creep of less than 10 ^-5 %. In other words, the creep likely to be observed at the rod is sufficiently low and consequently makes said rod compatible with a high temperature application.

The invention also relates to a second embodiment shown in Figure 8.

This second embodiment substantially incorporates all the characteristics of the first embodiment.

In particular, according to this second embodiment, at least one of the heat exchange means can be associated with an exchange conduit 400 (FIG. 8). In particular, the exchange duct is included in the volume of the first clamping plate and corresponds to a section of the secondary duct. The exchange conduit is in particular arranged to allow the gas flowing in said conduit to undergo additional overheating by means of the heat likely to be produced by the stack 200 (as described in document [2] cited in end of description). In particular, the exchange conduit 400 may comprise at least one section which extends in a direction parallel to the main faces. More particularly and as illustrated in FIG. 9, the exchange conduit 400 may comprise two heat exchange sub-channels 400A and 400B formed in two volume sections 301A and 301B of the first plate 300, plumb one from the other in a direction perpendicular to the main faces. A passage hole can, moreover, be formed between the two volume sections in order to make the two heat exchange sub-channels communicate.

In a particularly advantageous manner, the first plate 300 comprises, in its volume, four exchange conduits 401, 402, 403, and 404 (not shown) each associated with a different heat exchange means (FIG. 8).

In particular, each exchange circuit can occupy a quarter of the first plate.

Like the clamping rods, the first plate can also be manufactured using an additive manufacturing process, and in particular 3D manufacturing.

Thus, the heat exchange means described in the present invention make it possible to exploit the heat likely to be released by the stack in order to improve the overall efficiency of the electrochemical device. In particular, the proximity of the clamping rods and the stack makes the heat exchange more efficient, and without affecting the compactness of the electrochemical device.

Furthermore, the conformation of the recess forming the primary duct makes it possible to impose on the gas flowing in said primary duct a longer travel time and therefore a longer heat exchange time as well.

Finally, the one-piece nature of the clamping rod makes the reliability of the latter improved with respect to the same duct formed for example by means of an insert as described in document [3] cited at the end of the description.

REFERENCES

[1] FR 3 045 215;

[2] FR 3 088 773;

[3] FR 3 073 092.

Claims (19)

Electrochemical device (100) comprising:
- a SOEC/SOFC type solid oxide stack (200) operating at high temperature and comprising at least one elementary electrochemical cell (210);
- a clamping system provided with two clamping plates called, respectively, first plate (300) and second plate (310), and between which the stack (200) is clamped, each of the clamping plates comprising two essentially parallel main faces and connected by a lateral surface, each clamping plate further comprising at least two orifices, called clamping orifices;
- at least two clamping rods (60) which each extend from a clamping orifice, said first orifice (51), of the first plate (300) towards a clamping orifice, said second orifice (52), of the second plate so as to maintain the clamping of the stack (200) by the clamping plates;
at least one clamping rod among the at least two clamping rods (60), called the duct rod, comprises, in its volume, a recess forming a primary duct (80) in fluidic connection at one of its ends, said first end, with a secondary duct (91) formed in the volume of the first clamping plate (300), so as to allow the distribution or evacuation of at least one gas from the stack (200), said primary conduit (80) extends from the first to the second plate (310) so that the heat produced by the stack (200) allows, by radiation, heating of the gas flowing in said primary conduit (80), the the recess being made in such a way as to impose on a gas capable of flowing in the primary duct (80) a path of a length greater than the spacing between the two clamping plates. Device according to claim 1, in which the recess is formed around an axis of revolution of the driven rod. Device according to Claim 2, in which the recess follows a helical course. Device according to one of Claims 1 to 3, in which the conduit rod comprises a gas inlet end to be preheated and a gas outlet end preheated and in fluid communication with the clamping plate. Device according to one of Claims 1 to 4, in which the conduit rod comprises a radial conduit (81) providing fluid communication between the primary conduit (80) and the secondary conduit (90), the secondary condition being arranged to ensure the distributing gas from the primary conduit (80) to the stack (200). Device according to Claim 5, in which the radial conduit (81) is formed in a section of the conduit stem housed in the first orifice, the radial conduit (81) extends in a direction perpendicular to a direction of extension of the rod leads and is extended by a section, called the first secondary section (91) of the secondary conduit. Device according to Claim 6, in which the secondary conduit (90) comprises another section, called the second secondary section (92), which extends perpendicularly to the first secondary section (91). Device according to Claim 6 or 7, in which the first plate (300) comprises a channel, called the assembly channel (93), opening out at the level of the lateral surface and of the first orifice and in alignment with the first secondary section. Device according to Claim 8, in which a plugging pin (94) forming a keying element is inserted in the mounting channel. Device according to Claim 9, in which the duct rod comprises an alignment means (62) intended to cooperate with the plugging pin in order to impose the alignment of the radial duct and the first secondary duct. Device according to one of Claims 1 to 10, in which each of the at least two clamping rods (60) is welded at the level of exposed main faces, called first exposed face and second exposed face, respectively, of the first plate (300 ) and the second plate (310). Assembly according to one of Claims 1 to 11, in which the at least two clamping rods (60) are each assembled in a removable manner to the first and to the second plate (310). Device according to one of Claims 1 to 12, in which the secondary duct comprises a so-called exchange duct section allowing the gas circulating in the said channel to undergo additional overheating by means of the heat capable of being produced by the solid oxide stack (200) of the SOEC/SOFC type, the exchange conduit comprises at least one section which extends in a direction parallel to the main faces. Device according to Claim 13, in which the exchange duct comprises two heat exchange sub-channels formed in two volume sections of the first plate (300), vertical to each other in a perpendicular direction. to the main faces, a passage hole being formed between the two volume sections making the two heat exchange sub-channels communicate. Device according to one of Claims 1 to 14, in which two end plates called, respectively, first end plate (300) and second end plate (310), interposed, respectively, between the first plate (300) and the stack ( 200) on the one hand, and the second plate (310) and the stack (200) on the other hand, advantageously, the end plates are adapted to electrically insulate the clamping plates from the stack (200). Device according to one of Claims 1 to 15, in which the first plate (300) comprises a heating element intended to heat the gas capable of flowing in the secondary conduit, advantageously, the heating element comprises an electrical resistor. Device according to one of Claims 1 to 16, in which the at least one elementary electrochemical cell (210) is formed of an electrolyte interposed between two electrodes of different types called respectively anode and cathode. Device according to one of Claims 1 to 17, in which the clamping plates are made of heat-resistant austenitic steel, in particular of the AISI 310 type. Device according to one of Claims 1 to 18, in which the clamping plates each have a thickness of between 20 and 30 mm, in particular of the order of 25 mm.