Hot box comprising plate stacks for uniformly fed solid oxide electrolyzer (SOEC) or fuel cell system (SOFC), and associated installation

Abstract

The invention relates to a hot box (1) for SOEC / SOFC reversible high-temperature electrolysis stacks (2), comprising a tank (10) accommodating at least two stacks, an inlet (14) and an outlet (15) through which first and second fluids (32) can enter and be evacuated, said hot box further comprising a first supply line (6) for a third fluid in each of said at least two stacks (2), which extends from the outside of said tank to a central shaft (60). The hot box comprises sub-lines (61) for distributing said third fluid, each extending from the central distribution shaft to an inlet of a stack, said at least two stacks being positioned at an equal distance from said central shaft. The hot box also includes discharge channels (62) which extend from the bottom of each of the stacks, to a second discharge line which collects a fourth fluid and discharges it from said tank.Figure for abstract: [Fig. 1].

Description

Title of the invention: Hot box comprising stacks of plates for a solid oxide electrolyzer (SOEC) or for a fuel cell system (SOFC) uniformly supplied, and associated installation Technical field

[0001] The present invention relates to a hot box comprising stacks, i.e. columns of stacking of solid oxide plates making it possible to generate either dihydrogen or current, depending on the application that one wishes to implement, as well as an installation comprising at least one such hot box. State of the art

[0002] An energy production system or a system for producing hydrogen and oxygen-enriched air comprises at least one hot box comprising devices comprising a stack of solid oxide plates, called stacks, which ensure either the production of energy or the production of hydrogen from a gas flow passing through them. Depending on the implementation of such devices, the system operates either in electric current production (SOFC) or in dihydrogen production (SO$EC). In addition to the thermal management of such systems, the homogeneity of the distribution of fluids among the numerous devices required for large capacity hot boxes constitutes a major challenge.

[0003] Solutions are being sought to optimize the flow distribution of process fluids within a hot box for a SOEC / SOFC type system, while combining many other advantages, such as the possible elimination of a costly and energy-consuming safety air sweeping system.

[0004] Fuel cell stacks are electrochemical devices capable of converting the energy stored in fuels into electrical energy with high efficiency. Electrolyzer cells are electrochemical devices that can use electrical energy to reduce a given material, such as water, to generate a fuel, such as hydrogen. Fuel cells and electrolyzers may include reversible cells that operate in both fuel cell mode and electrolysis.

[0005] In a high temperature fuel cell system, such as a solid oxide fuel cell (SOFC) system, the oxidant stream is generally oxygen and flows on the cathode side, the fuel stream is generally hydrogen or other hydrocarbon, and flows on the anode side.

[0006] The fuel cell, operating at a typical temperature between 750°C and 950°C, allows the combination of oxygen and free hydrogen, leaving behind excess electrons. The excess electrons are returned to the cathode side of the fuel cell via an electrical circuit made between the anode and the cathode, which results in an electric current flow through the circuit.

[0007] In stacks constituting internally manifolded cells, fuel and air are distributed to each cell using risers contained within the stack. In other words, the gas flows through openings or holes in the support layer of each fuel cell, such as the electrolyte layer, and into the gas separator of each cell. In externally manifolded cells, the stack is open on the fuel and air inlet and outlet sides, and the fuel and air are introduced and collected independently of the cell hardware. For example, the inlet and outlet fuel and air flow in separate channels between the stack and the manifold housing in which the cell is located. Some fuel cell stacks may be collected internally for a first reactant (e.g., fuel) and externally for a second reactant (e.g., air).

[0008] An energy production system or a system for producing dihydrogen and oxygen-enriched air may comprise one or more stacks and a distribution system.

[0009] However, depending on the internal layout of the installations and the distribution system, the distribution of fluids to the stacks is not homogeneous, which has consequences on the efficiency of such installations or on their operating cost.

[0010] An object of the present invention is to optimize the distribution of fluids among the numerous stacks required for large capacity hot boxes, although it should be understood that the invention also applies in small capacity systems. Statement of the invention

[0011] ->Method or device

[0012] To this end, the invention relates to a hot box for reversible high-temperature electrolysis stacks SOEC / SOFC, comprising a tank comprising a tank side wall, a tank bottom, a tank top wall and a tank central axis, said tank delimiting an enclosure accommodating at least two stacks. Said tank comprising an inlet through which a first fluid can enter and circulate in said enclosure and an outlet through which a second fluid can be evacuated. The hot box further comprises a first pipe for supplying a third fluid into each of said at least two stacks.

[0013] According to the invention, the hot box is remarkable in that the first supply pipe comprises a main supply part for said third fluid, which extends from the outside of said tank to a central distribution shaft, and in that said box comprises: - distribution sub-conduits of said third fluid, which extend from the central distribution shaft to an inlet of a stack, said at least two stacks being positioned at equal distance from said central shaft, and - discharge channels which extend from the bottom of each of the stacks to a second discharge pipe which collects a fourth fluid and which discharges said fourth fluid from said tank.

[0014] This configuration of a central distribution shaft, positioned at an equal distance from each of the stacks, has several advantages, including: - Thermal and fluidic homogeneity thanks to a homogeneous distribution of the fluid, - A reduction in pressure losses for the same reasons. - The enclosure helps eliminate the effect of lower pressure on the stacks because the pressure is balanced inside and outside the stacks.

[0015] According to an advantageous (but not essential) option, the invention allows management of the safety function from the design stage: the need for air sweeping is eliminated with a box designed in this way, which thus allows energy savings and simplification of the system.

[0016] Advantageously, the invention has one or more of the following characteristics, taken in isolation or in any technically possible combination:

[0017] Preferably, said at least two stacks are positioned at equal distance from said axis of said tank and the central distribution shaft extends along said central axis of the tank.

[0018] According to an advantageous embodiment, said tank comprises an internal base which rests on said bottom of said tank and which at least partially comprises said central shaft, the distribution sub-ducts and said discharge channels. Said internal base is equipped with connection devices at the ends of the distribution sub-ducts and said discharge channels. Said connection devices are accessible from the enclosure of the tank to allow the connection of said stacks to the distribution sub-ducts and to the discharge channels.

[0019] More preferably, said main supply pipe is also said second discharge pipe for said fourth fluid, said supply pipe comprising a chamber for supplying the third fluid, the chamber being cylindrical and surrounding the discharge pipe for said fourth fluid, the discharge pipe and the supply chamber being coaxial. This embodiment makes it possible to recover the heat from the evacuated fluid to heat the fluid supplied to the stacks, which allows energy savings.

[0020] Advantageously, said tank has a square section and said stacks are positioned along the internal wall in the tank. This embodiment allows for ease of arrangement of the hot boxes and stacks.

[0021] According to an alternative embodiment, said tank has a cylindrical shape, said stacks are positioned along the side wall in the tank. In this second alternative, a compromise is made on the footprint in the ground for the benefit of a possible increase in pressure of the cylindrical enclosure, to guarantee greater efficiency of the electrochemical reaction.

[0022] Furthermore, the hot box comprises thermal insulation devices positioned between said stacks. More specifically, the thermal insulation devices can be positioned along the side wall of the tank, under the top wall, above the base and, preferably, between said stacks in order to guarantee their thermal homogeneity.

[0023] More preferably, said first fluid comprises air, said second fluid comprises a mixture enriched in dioxygen, said third fluid comprises water vapor and the fourth fluid comprises dihydrogen.

[0024] The invention also relates to an installation comprising at least one hot box of stacks as defined above. The installation further comprises a unit for controlling the operation of said at least one hot box of stacks, a main installation pipe ensuring the supply of third fluid to said first supply pipe.

[0025] Preferably, the installation according to the invention comprises at least three hot stack boxes, said main installation pipe opens into a central distribution trunk, the first supply pipe of each of said hot boxes is connected to said central distribution trunk and each of the hot boxes is positioned at an equal distance from said central distribution trunk.

[0026] Thus conceived, the invention allows the following advantages:

[0027] - ease of transport and installation thanks to the modular capacity of the boxes hot, in the context of such an embodiment,

[0028] - minimized bulk, because the piles (or stacks) can be arranged in modular clusters whose size and number can be selected to meet production needs,

[0029] - better management of seals and leaks: in fact, the seals are not no longer referenced to atmospheric pressure: only the pressure difference between the two gas circuits counts. A (slight) increase in pressure in the circuits of gas is possible without increasing the stress on the seals (pressure almost identical everywhere),

[0030] - the invention promotes the production of air enriched in O2, and

[0031] - it allows several hot boxes to be individually managed within the framework of a installation in accordance with the invention. Brief description of the figures

[0032] The invention will be better understood on reading the following description, given solely by way of non-limiting example and made with reference to the appended drawings in which:

[0033] [Fig-1]: [Fig.l] is a sectional view of a hot box according to the invention,

[0034] [Fig.2]: [Fig.2] is a top view of the hot box illustrated in [Fig.l], and

[0035] [Fig.3]: [Fig.3] shows an installation in accordance with the invention, comprising several hot boxes.

[0036] [Fig.4]: [Fig.4] shows another installation in accordance with the invention, comprising several hot boxes.

[0037] [Fig.5]: [Fig.5] shows the hot box of the installation illustrated in [Fig.4], seen in section according to plan AA.

[0038] [Fig.6]: [Fig.6] shows a schematic enlargement of a supply pipe of fuel (or combustible) and evacuation of fluid produced by the stacks of hot boxes in an installation in accordance with the invention.

[0039] [Fig.7]: [Fig.7] shows an alternative embodiment of an installation in accordance with the invention, comprising several hot boxes.

[0040] [Fig.8]: [Fig.8] shows yet another variant of an installation in accordance with the invention, comprising several hot boxes

[0041] It is understood that the embodiments which will be described subsequently are not limiting. In particular, it will be possible to imagine variants of the invention comprising only a selection of characteristics described subsequently isolated from the other characteristics described, if this selection of characteristics is sufficient to confer a technical advantage or to differentiate the invention compared to the state of the prior art. This selection comprises at least one preferably functional characteristic without structural details, or with only a part of the structural details if it is this part which is only sufficient to confer a technical advantage or to differentiate the invention compared to the state of the prior art.

[0042] In particular, all the variants and all the embodiments described can be combined with each other if nothing prevents this combination from a technical point of view.

[0043] In the figures and in the remainder of the description, the elements common to several figures retain the same reference. Detailed description

[0044] Figures 1 and 2 show a hot box 1 according to the invention, comprising a cylindrical tank 10, in which eight stacks 2 (i.e. eight stacks of solid oxide plates forming columns) are distributed equidistantly in the tank 10, along the internal wall of the tank.

[0045] More precisely, the tank 10 of the hot box 1 comprises a cylindrical side wall 11, a tank bottom 12, a tank top wall 13 and a central tank axis Z.

[0046] The set of walls 11, 12 and 13 delimits a closed volume forming an enclosure which accommodates the eight stacks 2.

[0047] It should be understood that the tank of the hot box according to the invention could have a different shape without departing from the scope of the invention: it could, for example, be parallelepipedal in shape, or any other cross-sectional shape. [Fig.4] illustrates an example which will be described later.

[0048] Similarly, the hot box according to the invention could have a different number of stacks without departing from the scope of the invention: for example, it could comprise three, ten, twelve, etc. without departing from the scope of the invention. The tank must comprise at least two stacks.

[0049] In the context of this example, stacks 2 are high-temperature electrolysers for generating dihydrogen.

[0050] The principle of the electrolyser is the opposite of that of a fuel cell. The operation of the electrolyser requires a supply of fuel, which includes water vapour possibly mixed with a little dihydrogen.

[0051] As previously indicated, the stacks operate at a typical temperature between 650°C and 950°C.

[0052] In the context of our example, each stack (or fuel cell) comprises at least one stack of plates capable of generating the desired chemical reaction for the use that is desired (production of dihydrogen or energy). It could be provided that the stack comprises several stacks on top of each other without departing from the scope of the invention.

[0053] The stacks thus form columns which each extend along an axis parallel to the Z axis of the cylindrical tank 10. The stacks 2 thus have a column shape which extends over the height of the internal enclosure of the tank 10.

[0054] According to the invention, the tank 10 comprises an inlet 14 through which a first fluid 31 can enter: in the context of our example, this is air 31 which is distributed homogeneously around each stack 2.

[0055] The tank 10 also comprises an outlet 15 through which a second fluid can be evacuated: in our example this is a mixture 32 enriched in O2, which can be extracted using standard piping, connecting each stack 2.

[0056] The inlet 14 and the outlet 15 essentially have the function of creating a movement of air in the hot box, allowing the possible evacuation of dihydrogen which may come from leaks, and at the same time allowing the internal / external pressures in the stack to be balanced.

[0057] It can be seen in [Fig.l] that the outlet 15 collects the oxygen-enriched air 32 under each stack 2 and that, to enable this collection, the tank has an internal base 4, on which each of the stacks 2 rests, the base having a number of through openings 40 proportional to the number of stacks 2 installed.

[0058] The through openings 40 open into said piping, comprising conduits 41 which join in a common conduit 42, the latter opening onto the outlet 15 of the tank.

[0059] In the case of this example, sufficient sealing must be achieved between the tank enclosure, the stacks 2 and the base 4.

[0060] It is provided that the base 4 is positioned at a height h above the bottom of the tank, so that the tank comprises an internal base 5 of height h, in which the conduits 41 and 42 extend.

[0061] The internal base 5 can be filled with an insulating material.

[0062] The base 5 also includes other pipes which allow water vapor containing a little dihydrogen to be brought into the stacks, this vapor allowing the reaction that is desired to be obtained, which produces dihydrogen. These same pipes allow the dihydrogen produced to be evacuated.

[0063] The main objective of the invention is to bring to each stack 2 and at the same time the same quantity or proportion of water vapor (possibly including a little dihydrogen) necessary for the production of dihydrogen. Thus the stacks 2 are arranged so as to optimize the distribution of fluid between them.

[0064] In the examples shown in the figures, the incoming fluid and the outgoing fluid are conveyed via the same pipe, illustrated in particular in [Fig.6].

[0065] This is a main supply pipe 6 which is connected to a central shaft 60: in the example illustrated in Figures 1 and 2, the pipe 6 extends from the side wall 10 of the tank to a central shaft 60 which has the function of distributing the fuel to the stacks 2.

[0066] According to an alternative embodiment shown in [Fig.5], the pipe 6 extends above the tank and feeds the central shaft 60 which extends in the center of the hot box 1, into the base 5.

[0067] Advantageously, the fuel fluid (or combustible) (i.e., in our example, the mixture of water vapor with possibly a little di-hydrogen) can circulate in the wall of the pipe 6, which is hollow (see arrow Fl) and the dihydrogen produced circulates in the central part of the pipe 6 (see arrow F2). In other words, said main pipe 6 for supplying the steam is also said second pipe for discharging the dihydrogen: as can be seen in [Fig.6], said pipe 6 comprising a chamber 63 for supplying the water vapor, which is cylindrical and which surrounds the discharge pipe 64 of said dihydrogen, the discharge pipe 64 and the supply chamber 63 being coaxial.

[0068] This advantageous embodiment makes it possible to use the heat produced by the hydrogen discharged into the pipe 64 to adjust the temperature of the water vapor brought into the chamber 63.

[0069] The distribution shaft 60 ensures that all fluid paths to the stacks 2 have exactly the same length and design, thus ensuring a homogeneous flow distribution. This same distribution shaft 60 and the pipe 6 associated with it also collect the dihydrogen produced by the stacks to evacuate it from the hot box 1.

[0070] To do this, distribution sub-ducts 61 (or “outgoing” ducts) all leave from the shaft 60 to supply each of the stacks 2 and evacuation channels 62 (or return ducts) all leave from the stacks 2 to return to the central shaft 60. In addition, the stacks 2 are positioned at an equal distance from said axis Z of the tank and therefore from the central distribution shaft 60.

[0071] All the forward 61 and return 62 pipes extend into the insulating and insulated base 5.

[0072] To enable the stacks 2 to be connected to the supply and return pipes 61 and 62, as well as to the discharge pipes 40, the base 4 comprises connection devices which are accessible from the enclosure of the tank.

[0073] In order to allow a clear reading of the figures, these connection devices have not been shown. It should however be understood that such devices are known to those skilled in the art and relate to conventional pipe connection devices.

[0074] Insulating elements 7 may be provided between two contiguous stacks 2: these elements 7 allow the stacks to operate at their optimum temperature by limiting the thermal influence of the neighboring stacks.

[0075] Depending on the positioning of the stacks in the tank, and depending on the shape of the tank, the insulating elements can be of various shapes, occupying the spaces between the columns of stacks.

[0076] Thus, in [Fig.4], the insulating elements are insulating walls, surrounding all of the stacks 2 and a grid in which the stacks are positioned, while in Figures 1 and 2, the insulating elements 7 each form sections of rings positioned between the stacks, opposite the internal wall of the tank 10.

[0077] Reference will now be made to Figures 3 and 4, which illustrate installations in accordance with the invention.

[0078] The installation shown in [Fig.3] comprises eight hot boxes of stacks 2 such as those illustrated in Figures 1 and 2.

[0079] It also comprises a control unit 8 for the operation of the hot boxes 1 and a main pipe 9 which ensures the supply of fluid to the supply pipes 6 of each hot box 1.

[0080] In the context of this embodiment, a main pipe 9 (or a network of main pipes 9) which supplies the hot boxes with fluid is also the pipe for discharging the fluids at the outlet of the stacks of the hot boxes, because it collects the fluid produced by the stacks: the main pipe 9 can be produced in the same way as the pipes 6. The reference 9 could also indicate a set of fluid supply and discharge pipes, the set of pipes would be linked to the main pipes 6 of the hot boxes 1, without departing from the scope of the invention.

[0081] It can be seen that all the hot boxes 1 are positioned at equal distance from the main conduit 9.

[0082] [Fig.4] illustrates another installation, where the hot boxes 1 have a camembert shape, comprising a set of stacks distributed in a square around the shaft 60: the stacks are all at equal distance from the shaft 60 and the hot boxes 1 are all positioned at equal distance from a central trunk 20, this central trunk being supplied by the main pipe 9 of the installation: such an embodiment makes it possible to ensure that all the hot boxes are truly supplied at the same time; the pipes 6 having the same length between the central distribution shaft of each hot box and the central trunk 20 from which the water vapor (possibly mixed with a little dihydrogen) supplying the stacks comes.

[0083] It can be seen in [Fig.4] that each hot box 1 comprises a panel 3, which is removable, and which allows access to the interior of the tank of the hot box.

[0084] The assembly forms a module which can operate alone, or be combined with other modules to form an even larger installation.

[0085] For example, [Fig.7] illustrates an installation which combines several modules: this installation is in the shape of a flower.

[0086] It comprises four groups (or four modules) of three hot boxes 1, in the shape of a camembert, which each comprise a set of stacks 2 distributed in a square around a common feed shaft.

[0087] The hot boxes 1 are all positioned at equal distance from a central trunk 20 which feeds their main line 6.

[0088] Each module (or group) of hot boxes is supplied by a main pipe 9 which is connected to a common control and supply module 90.

[0089] We note in [Fig.7] that the module is attached to the control module 90 which forms the heart of the installation.

[0090] [Fig.8] illustrates an alternative embodiment of a four-module installation: according to this embodiment, the common control and power supply module 90 extends between two columns of two modules each comprising three hot boxes 1. The modules are thus placed on either side of the control and power supply module 90.

[0091] The main pipes 9 leave on either side of the control module 90, whereas according to the configuration shown in [Fig.7], the main pipes form a star from the control module 90.

[0092] It is thus understood that, depending on the space available, the invention can allow different configurations, to form systems with high production capacity.

[0093] The preceding description makes it possible to appreciate how the invention makes it possible to achieve the set objectives and, in particular, how it allows a good distribution of energies around the stacks and an equivalent efficiency for each of the stacks.

[0094] Of course, the invention is not limited to the examples which have just been described and extends to the implementation of any equivalent means.

Claims

Claims

1. Hot box (1) of SOEC / SOFC reversible high-temperature electrolysis stacks (2), comprising a tank (10) comprising a tank side wall (11), a tank bottom (12), a tank top wall (13) and a tank central axis (Z), said tank (10) delimiting an enclosure accommodating at least two stacks (2), said tank (10) comprising an inlet (14) through which a first fluid (31) can enter and circulate in said enclosure and an outlet (15) through which a second fluid (32) can be evacuated, said hot box (1) further comprising a first supply line (6) for a third fluid in each of said at least two stacks (2), characterized in that: - the first supply line (6) comprises a main supply portion of said third fluid, which extends from the outside of said tank to a central distribution shaft (60), and in that that it comprises: - sub-conduits (61) for distributing said third fluid,which extend from the central distribution shaft (60) to an inlet of a stack, said at least two stacks (2) being positioned at equal distance from said central shaft (60), and - evacuation channels (62) which extend from the bottom of each of the stacks (2), to a second evacuation pipe which collects a fourth fluid and which evacuates said fourth fluid from said tank.,

2. Hot box of stacks according to claim 1, characterized in that said at least two stacks (2) are positioned at equal distance from said axis (Z) of said tank and in that said central distribution shaft (60) extends along said central axis (Z) of the tank.

3. Hot box of stacks according to claim 1 or 2, characterized in that said tank (10) comprises an internal base (5) which rests on said bottom (12) of said tank and which at least partially comprises said central shaft (60), the distribution sub-ducts (61) and said discharge channels (62), said internal base (5) being equipped with connection devices at the ends of the distribution sub-ducts (61) and said discharge channels (62), said connection devices being accessible from the enclosure of the tank (10) to allow the connection of said stacks (2) to the distribution sub-ducts (61) and to the channels evacuation (62).

4. Hot box according to any one of the preceding claims, characterized in that said main supply pipe (6) is also said second discharge pipe of said fourth fluid, said supply pipe (6) comprising a supply chamber (63) for the third fluid (F1), the supply chamber being cylindrical and surrounding the discharge pipe (64) of said fourth fluid, the discharge pipe (64) and the supply chamber (63) being coaxial.

5. Hot box according to any one of the preceding claims, characterized in that said tank (10) has a square section and in that said stacks are positioned along the internal wall in the tank.

6. A hot box of stacks according to any one of claims 1 to 4, characterized in that said tank (10) has a cylindrical shape and in that said stacks are positioned along the side wall (11) in the tank.

7. Hot box of stacks according to any one of the preceding claims, characterized in that it comprises thermal insulation devices (7) positioned between said stacks (2).

8. Hot box of stacks according to any one of the preceding claims, characterized in that said first fluid (31) comprises air, said second fluid (32) comprises a mixture enriched in dioxygen, said third fluid (F1) comprises water vapor and in that the fourth fluid comprises dihydrogen.

9. Installation comprising at least one hot box (1) of stacks (2) according to any one of the preceding claims, a control unit (8) for the operation of said at least one hot box (1) of stacks (2), a main installation pipe (9) ensuring the supply of third fluid to said first supply pipe (6) of said at least one hot box (1) of stacks (2).

10. Installation according to claim 9, characterized in that it comprises at least three hot boxes (1) of stacks (2), in that said main installation pipe (9) opens into a central distribution trunk (20), in that the first supply pipe (6) of each of said hot boxes (1) of stacks (2) is connected to said central distribution trunk (20) and in that each of the hot boxes (1) is positioned at an equal distance from said central distribution trunk (20).

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