JP2004227845A - Solid oxide fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To miniaturize a fuel cell module and to improve its reliability. <P>SOLUTION: An electrode layer is disposed on both surfaces of a solid electrolytic layer, to constitute a power generation cell 5, and the power generation cell 5 and a separator 8 which incorporates gas flow paths 9 and 10 are laminated alternately by a plurality of numbers, to constitute a fuel cell stack 1. Each separator 8 is connected to gas supply pipes 13 and 14 for supplying reactive gas to each electrode layer. The gas supply pipes 13 and 14 are arranged vertical to the separator 8. With this configuration, wasteful space is eliminated on the lateral parts of the stack, when stacking the fuel cell is stacked, so the fuel cell module is miniaturized. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a plate-stacked solid oxide fuel cell, and more particularly, to an arrangement structure of a gas supply pipe connecting a distributor and a separator.
[0002]
[Prior art]
The solid oxide fuel cell (SOFC) is being developed as a third-generation fuel cell for power generation. At present, three types of solid oxide fuel cells, a cylindrical type, a monolith type, and a flat plate type, have been proposed. In each case, a solid electrolyte made of an oxide ion conductor is connected to an air electrode (cathode) from both sides. It has a laminated structure sandwiched between fuel electrodes (anodes). The power generation cells composed of the stacked body are alternately stacked with the separator with the fuel electrode current collector and the air electrode current collector interposed therebetween to form a fuel cell stack.
[0003]
In a solid oxide fuel cell, oxygen (air) is supplied to the air electrode side, and fuel gas (H ₂ , CO, etc.) is supplied to the fuel electrode side. Both the air electrode and the fuel electrode are porous layers so that the gas can reach the interface with the solid electrolyte.
Oxygen supplied to the air electrode side reaches the vicinity of the interface with the solid electrolyte layer through pores in the air electrode layer, receives electrons from the air electrode at this portion, and is ionized into oxide ions (O ²⁻ ). Is done. The oxide ions diffuse and move in the solid electrolyte layer toward the fuel electrode. The oxide ions that have reached the vicinity of the interface with the fuel electrode react with the fuel gas at this portion to generate a reaction product (H ₂ O, CO _2, etc.), and emit electrons to the fuel electrode. The electrons can be extracted to the outside as an electromotive force.
[0004]
FIG. 8 shows a stack structure of a solid oxide fuel cell.
The fuel cell stack 1 includes a power generation cell 5 in which a fuel electrode layer and an air electrode layer (oxidant electrode layer) are arranged on both surfaces of a solid electrolyte layer, a fuel electrode current collector 6 outside the power generation cell, and an air electrode current collector. 7 and a separator 8 outside the current collectors 6 and 7 are sequentially laminated.
[0005]
The solid electrolyte layer is made of stabilized zirconia (YSZ) to which yttria is added, and the fuel electrode layer is made of a metal such as Ni or Co or a cermet such as Ni-YSZ or Co-YSZ. Is composed of LaMnO ₃ , LaCoO _3, etc., the fuel electrode current collector 6 is composed of a sponge-like porous sintered metal plate such as a Ni-based alloy, and the air electrode current collector 7 is composed of an Ag-based alloy, etc. The separator 8 is made of a sponge-like porous sintered metal plate, and the separator 8 is made of stainless steel or the like.
[0006]
The separator 8 has a function of electrically connecting the power generation cells 5 and supplying a gas to the power generation cells 5. Fuel gas is introduced into the inside of the separator 8 from the outer peripheral surface of the separator 8, and the fuel of the separator 8 is discharged. A fuel gas passage for discharging from a substantially central portion of the surface facing the pole current collector 6; and an oxidizing gas introduced from the outer peripheral surface of the separator 8 and discharging from the surface of the separator 8 facing the cathode current collector 7. An oxidant gas passage is provided.
[0007]
A plurality of reaction gas supply pipes (that is, a fuel gas supply pipe 13 and an oxidizing gas supply pipe 14) are connected to the side of the fuel cell stack 1 in the horizontal direction. A fuel distributor 15 for supplying a fuel gas through a fuel gas supply pipe 13 and an oxidant distributor 16 for supplying an oxidant gas (air) through an oxidant gas supply pipe 14 to the oxidant gas passage of each separator 8. , Extending in the stacking direction of the power generation cells 5.
[0008]
Such an arrangement structure of the gas supply pipe and the distributor is also described in Patent Document 1.
[0009]
[Patent Document 1]
JP-A-6-13088
[Problems to be solved by the invention]
By the way, as described in the above-described disclosed technology, a known gas supply structure such as extending a gas supply pipe in a horizontal direction from a side portion of a separator and connecting the gas supply pipe to a distributor has a problem in stacking. Each of the sections requires a useless space for extending a gas supply pipe, which has been an obstacle to downsizing the module.
[0011]
The present invention has been made in view of the above-described problems, and by arranging a gas supply pipe in a direction perpendicular to a separator, it is possible to reduce a space in a lateral direction and reduce the size of a module, and to provide a flow path connecting mechanism. It is an object of the present invention to provide a solid oxide fuel cell having an improved module reliability with respect to a heat cycle.
[0012]
[Means for Solving the Problems]
That is, according to the first aspect of the present invention, a fuel cell is provided by arranging electrode layers on both sides of a solid electrolyte layer to form a power generation cell, and alternately stacking a plurality of the power generation cells and a separator having a gas flow path therein. A stack is formed, and in a flat-plate stacked solid oxide fuel cell that supplies a reaction gas to each electrode layer through a separator by a gas supply pipe, the gas supply pipe is disposed in a direction perpendicular to the separator. Configured.
[0013]
According to a second aspect of the present invention, in the solid oxide fuel cell according to the first aspect, the other end of each of the gas supply pipes is connected to a distributor above or below the fuel cell stack.
[0014]
According to a third aspect of the present invention, in the solid oxide fuel cell according to the second aspect, a part or all of the distributor is made of a polytetrafluoroethylene material.
[0015]
In the configuration according to the first and second aspects, a wasteful space in the lateral direction (side portion) of the fuel cell stack can be eliminated in stacking, so that the size of the module can be reduced.
Further, according to the configuration of the third aspect, electrical insulation between the separators can be obtained without providing a complicated flow path connecting mechanism for insulation (for example, the ceramic joint 17 shown in FIG. 8), and the ceramic material is used. Damage due to the thermal cycle that caused the problem can be avoided, and the reliability of the module can be improved. In particular, when the distributor is disposed at a normal temperature or a low temperature environment of 100 to 200 ° C., the polytetrafluoroethylene material is advantageous because it is inexpensive.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to FIGS.
[0017]
1 is a longitudinal sectional view of a flat-plate type fuel cell stack according to the present invention, FIG. 2 is a plan view thereof, FIG. 3 is a plan view of each separator used in the fuel cell stack of FIG. 1, and FIG. 5 is a plan view, FIG. 6 is a plan view of each separator used in the fuel cell stack of FIG. 4, and FIG. 7 is a longitudinal sectional view of a fuel cell module.
[0018]
As shown in FIG. 1, a fuel cell stack 1 of the present embodiment includes a power generation cell 5 configured by arranging a fuel electrode layer and an air electrode layer on both surfaces of a solid electrolyte layer, and a fuel cell disposed outside the fuel electrode layer. A single cell is composed of the electrode current collector 6, the air electrode current collector 7 disposed outside the air electrode layer, and the separator 8 disposed outside each of the current collectors 6 and 7. It is a cylindrical body that is stacked.
The configuration of the single cell is the same as that of FIG. 8, but in the present embodiment, the fuel gas supply pipe 13 and the oxidant gas supply pipe 14 connected to each separator 8 are substantially perpendicular to the separator 8, that is, in the vertical direction. Are different from those in FIG.
[0019]
Here, the separator 8 is made of a square stainless steel plate having a thickness of about 3.5 mm. As shown in FIG. 1, the fuel gas supplied from the fuel gas supply pipe 13 is supplied to the inside of the separator 8. A fuel gas passage 9 which is introduced from the outer peripheral surface of the separator and is discharged from a central gas discharge hole 11, and an oxidizing gas supplied from an oxidizing gas supply pipe 14 is introduced from an opposite outer peripheral surface of the separator to form a central gas discharging hole. An oxidizing gas passage 10 to be discharged from the nozzle 12 is formed.
[0020]
As shown in FIG. 2, a rectangular fuel gas connecting portion 19 having a through hole 19a communicating with the fuel gas passage 9 at an end portion at an outer peripheral portion of each separator 8; Rectangular connecting portions 20 for oxidizing gas having communicating holes 20a are arranged to face each other and extend in the horizontal direction, and each connecting portion is connected so as to communicate with the through holes 19a and 20a of these connecting portions. The fuel gas supply pipe 13 and the oxidant gas supply pipe 14 made of stainless steel are fixed and connected in a substantially vertical state by welding, for example, corresponding to the pipes 19 and 10, and the vicinity of the side of the tubular body extends upward. Is established.
[0021]
FIG. 3 shows the structure of each separator 8. FIG. 3A shows a separator located at the lowermost portion of the stack, in which only a fuel gas connecting portion 19 is formed on the far right side of the rectangular separator 8 in the figure, and the fuel gas communicates with the through hole 19a. A passage 9 extends to the center of the separator 8, and a discharge hole 11 that opens upward is formed at the end of the passage.
Further, the fuel gas connecting portion 19 of the lowermost separator 8 does not vertically overlap with the fuel gas connecting portion 19 of the lowermost separator 8, so that the fuel gas The connecting portion 19 is formed, and on the left side, an oxidizing gas connecting portion 20 is formed at a position facing the oxidizing gas. An oxidizing gas passage 10 communicating with the through hole 20a of the oxidizing gas connecting portion 20 extends to the center of the separator 8, and a discharge hole 12 that opens downward is formed at an end thereof.
Similarly, in FIGS. 3C and 3D, the connecting portions for the fuel gas 19 and the connecting portion for the oxidizing gas are shifted from each other so that the connecting portions of the adjacent separators 8 are not overlapped in the vertical direction. The separator 8 on which only the oxidizing gas connecting portion 20 is formed as shown in FIG.
[0022]
As described above, in the present embodiment, the individual separators 8 are arranged such that the positions of the connecting portions 19 and 20 adjacent to each other in the laminating direction are continuously shifted in the circumferential direction of the separator 8 and are stacked in a cylindrical shape. I have. The plurality of fuel gas supply pipes 13 and the oxidant gas supply pipes 14 connected to the connecting portions 19 and 20 of the stacked separators 8 are each extended in the vertical direction at a predetermined interval without contacting each other. The ends of the gas supply pipes 13 and 14 are fixedly connected to the side walls of the fuel distributor 15 and the oxidant distributor 16 disposed above the fuel cell stack 1 in a line.
[0023]
For example, in the case where the number of stacked separators 8 is large and it is not possible to dispose all the connecting portions so as not to overlap the four sides of the separator 8, as shown in FIGS. The pipe 13 and the oxidizing gas supply pipe 14 can be arranged in two rows in the lateral direction, respectively.
In this case, in addition to the separator 8 of FIG. 2 that constitutes the inner tube arrangement, the separator shown in FIGS. 6A to 6E can be provided with the gas supply pipes 13 and 14 disposed outside. Each separator 8 will be added. As shown, in the present embodiment, the positional relationship between the fuel gas connecting portion 19 and the oxidizing gas connecting portion 20 in each separator 8 is the same as that in FIG. 2, and the length thereof is set somewhat longer. .
[0024]
When the separator 8 having this configuration is used, the gas supply pipes 13 and 14 are connected to the distal ends of the connection portions 19 and 20 of the separator 8 at a constant interval in the circumferential direction and the lateral direction of the fuel cell stack 1. The other ends of the distributors 19 and 20 are connected to the side walls of the distributors 19 and 20 above the fuel cell stack in two rows.
[0025]
As described above, by arranging the gas supply pipes 13 and 14 in a vertical structure, when stacking, the wasteful horizontal piping space conventionally generated by the gas supply pipes extending to the side portions of the stack is reduced. Since the fuel cell module can be eliminated, the size of the fuel cell module can be reduced.
[0026]
In this embodiment, only the left side and the right side of the rectangular separator 8 are used as the formation portions of the connecting portions 19 and 20, however, the rear side and the front side can of course be used. For example, the formation portion of the connection portion 19 for the fuel gas uses the left side and the rear side, and the connection portion 20 for the oxidizing gas uses the right side and the front side. In addition, it is of course possible to arrange the gas supply pipes 13 and 14 in three or more rows according to the number of stacked separators 8, and the shape of the separator 8 may be round instead of square.
Further, in the present embodiment, an example in which the distributors 15 and 16 are disposed above the fuel cell stack 1 has been described. On the contrary, the gas supply pipes 13 and 20 are connected from the connecting portions 19 and 20 of the separators 8. The distributors 15 and 16 can be disposed below the fuel cell stack 1 with the shape of the fuel cell stack 1 falling.
[0027]
In the stack structure as described above, the oxidizing gas supplied from the outside is introduced into the oxidizing gas passage 10 from the oxidizing gas supply pipe 14 through the through hole 20a of the connecting portion 20 for the oxidizing gas. The oxidant gas is discharged from the discharge hole 12 and supplied to the facing air electrode current collector 7. On the other hand, fuel gas from the outside is introduced into the fuel gas passage 9 from the fuel gas supply pipe 13 through the through hole 19a of the fuel gas connecting portion 19, and is discharged from the fuel gas discharge hole 11 at the end of the passage to face the fuel gas. To the current collector 6.
[0028]
Further, in the present embodiment, since the distributors 15 and 16 are each formed of an electrically insulating member such as a polytetrafluoroethylene material, a complicated flow path connecting mechanism for insulation such as a conventional ceramic joint is used. Electrical insulation between the separators can be obtained without using them. Thereby, damage due to the thermal cycle, which is a problem with ceramic materials, can be avoided, and the reliability of the fuel cell module is improved.
[0029]
In particular, when the distributor is disposed in a normal temperature or low temperature environment, the polytetrafluoroethylene material is advantageous because it is inexpensive.
FIG. 7 shows an example of this. The fuel cell stack 1 is housed in a box 21 made of a heat insulating material, a heat-resistant metal, ceramics, or the like to make the fuel cell modular, and a thermal cell is provided outside the box. In this configuration, a separated chamber 22 is provided separately, and a distributor 15 for fuel and a distributor 16 for oxidant are installed in the chamber.
As described above, in the case of the module structure in which the distributors 15 and 16 are installed outside the power generation furnace, the chamber 22 is maintained at a normal temperature or a low temperature such as 100 to 200 ° C., so that the heat resistance of the poly 4 is lower than that of the ceramic material. Use of distributors 15 and 16 made of fluorinated ethylene becomes possible. As a result, the reliability of the insulating seal portion (the gas seal at the connection between the gas supply pipes 13 and 14 and the distributors 15 and 16, for example, a glass seal) is greatly improved, and the heat cycle resistance of the fuel cell module is improved. Leads to the improvement of
[0030]
【The invention's effect】
As described above, according to the first and second aspects of the present invention, the gas supply pipes are disposed perpendicular to the separator, and the other end of each gas supply pipe is located above the fuel cell stack. Alternatively, since it is configured to be connected to the distributor at the lower side, it is possible to eliminate a useless space in the lateral direction of the stack when stacking the fuel cells, so that the size of the fuel cell module can be reduced.
[0031]
According to the third aspect of the present invention, since a part or all of the distributor is made of a polytetrafluoroethylene material, a complicated flow path connection for insulation like a conventional ceramic joint is used. Electrical insulation between the separators can be obtained without using a mechanism, and breakage due to a thermal cycle, which has conventionally been a problem with ceramic materials, can be avoided, thereby improving the reliability of the module.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of a fuel cell stack according to the present invention.
FIG. 2 is a plan view of the fuel cell stack of FIG.
FIG. 3 is a plan view of each separator used in the fuel cell stack of FIG. 1;
FIG. 4 is a longitudinal sectional view of another fuel cell stack different from FIG. 1;
FIG. 5 is a plan view of the fuel cell stack of FIG.
FIG. 6 is a plan view of each separator used in the fuel cell stack of FIG.
FIG. 7 is a longitudinal sectional view showing the structure of the fuel cell module according to the present invention.
FIG. 8 is a diagram showing a structure of a conventional fuel cell stack.
[Explanation of symbols]
Reference Signs List 1 fuel cell stack 5 power generation cell 8 separator 9 gas flow path (fuel gas passage)
10. Gas flow path (oxidant gas path)
13 Gas supply pipe (fuel gas supply pipe)
14. Gas supply pipe (oxidant gas supply pipe)
15 Distributor (distributor for fuel)
16 Distributor (Distributor for oxidizer)

Claims (3)

An electrode layer is arranged on both sides of the solid electrolyte layer to form a power generation cell, a plurality of the power generation cells and a separator having a gas flow path therein are alternately stacked to form a fuel cell stack, and a gas supply pipe passes through the separator. In a solid oxide fuel cell that supplies a reaction gas to each electrode layer,
The solid oxide fuel cell according to claim 1, wherein the gas supply pipe is disposed in a direction perpendicular to the separator. The solid oxide fuel cell according to claim 1, wherein the other end of each of the gas supply pipes is connected to a distributor above or below the fuel cell stack. The solid oxide fuel cell according to claim 2, wherein a part or all of the distributor is made of a polytetrafluoroethylene material.

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