JP2004055195A - Flat layer-built solid oxide fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a connection mechanism for a gas supply tube independent of the thickness of a separator for reducing the thickness and weight of a fuel cell stack. <P>SOLUTION: A power generation cell 5 is constituted by arranging a fuel electrode layer and an oxidant electrode layer on both faces of a solid electrolyte layer, and a fuel cell stack 1 is constituted by layering multiple power generation cells 5 via separators 8 each having a gas passage inside. In the outer circumference of the separator 8, connection parts 14 and 15 communicated with the gas passage and connected to gas supply tubes 9 and 10 from the outside are protruded outward, while the respective separators 8 are arranged to be stacked so that the adjacent connection parts 14 and 15 are shifted from each other in the layer direction. In this way, the thickness of the separator 8 can be reduced, while the size and the weight of the fuel cell stack 1 can be reduced. In addition, heavy pressure to the power generation cell 5 positioned in the lower part of the stack can be reduced because of reduction in weight, and the breakage of the power generation cell 5 due to the heavy pressure can be prevented. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a solid oxide fuel cell, and more particularly, to a flat plate type solid oxide fuel cell in which the thickness of a separator is reduced to reduce the thickness of a fuel cell stack.
[0002]
[Prior art]
A solid electrolyte fuel cell with a laminated structure in which a solid electrolyte layer composed of an oxide ion conductor is sandwiched between an air electrode layer (oxidant electrode layer) and a fuel electrode layer is a third-generation fuel cell for power generation. Development is in progress. 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 so that the gas can reach the interface with the solid electrolyte.
[0003]
Oxygen supplied to the air electrode side passes through pores in the air electrode layer and reaches near the interface with the solid electrolyte layer, where electrons are received from the air electrode and converted into oxide ions (O ²⁻ ). Ionized. 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.
[0004]
The electrode reaction when hydrogen is used as the fuel is as follows.
Air electrode: 1/2 O ₂ + 2e ⁻ → O ²⁻
The fuel ^{_{electrode: H 2 + O 2- → H}} 2 O + 2e -
Whole: H ₂ + 1 / 2O ₂ → H ₂ O
[0005]
The solid electrolyte layer is a gas impermeable dense structure because it functions as a partition for preventing direct contact between fuel gas and air, as well as a moving medium for oxide ions. This solid electrolyte layer must be composed of a material that has high oxide ion conductivity, is chemically stable under the conditions from the oxidizing atmosphere on the air electrode side to the reducing atmosphere on the fuel electrode side, and is resistant to thermal shock. As a material satisfying such requirements, stabilized zirconia (YSZ) to which yttria is added is generally used.
[0006]
On the other hand, both the air electrode (cathode) layer and the fuel electrode (anode) layer, which are electrodes, need to be made of a material having high electron conductivity. Since the air electrode material must be chemically stable in a high-temperature oxidizing atmosphere of about 700 ° C., a metal is inappropriate, and a perovskite-type oxide material having electron conductivity, specifically LaMnO ₃ Alternatively, LaCoO ₃ or a solid solution in which part of La is replaced with Sr, Ca, or the like is generally used. The fuel electrode material is generally a metal such as Ni or Co, or a cermet such as Ni-YSZ or Co-YSZ.
[0007]
Solid oxide fuel cells include a high-temperature operation type that operates at a high temperature of about 1000 ° C. and a low-temperature operation type that operates at a low temperature of about 700 ° C. In a low-temperature operation type solid oxide fuel cell, for example, the thickness of stabilized zirconia (YSZ) to which yttria as an electrolyte is added is reduced to about 10 μm to lower the resistance of the electrolyte, and power is generated as a fuel cell even at a low temperature. Use a modified power generation cell.
[0008]
In a high-temperature solid oxide fuel cell, a ceramic having electronic conductivity such as lanthanum chromite (LaCrO ₃ ) is used as a separator. In a low-temperature operating solid oxide fuel cell, a metal material such as stainless steel is used. Can be used.
[0009]
In addition, three types of structures of a solid oxide fuel cell, a cylindrical type, a monolith type, and a flat plate type, have been proposed. Among these structures, a low-temperature-operating solid oxide fuel cell can use a metal separator, and therefore, a flat plate-type structure that can easily impart a shape to the metal separator is suitable.
[0010]
The stack of the plate-stacked solid oxide fuel cell has a structure in which power generation cells, current collectors, and separators are alternately stacked. A pair of separators sandwich the power generation cell from both sides, one of which is in contact with the air electrode via the air electrode current collector, and the other is in contact with the fuel electrode via the fuel electrode current collector. A sponge-like porous material such as a Ni-based alloy can be used for the fuel current collector, and a similar sponge-like porous material such as an Ag-based alloy can be used for the air electrode current collector. it can. The sponge-like porous body has a current collecting function, a gas permeating function, a uniform gas diffusing function, a cushioning function, a thermal expansion difference absorbing function, and the like, and is therefore suitable as a multifunctional current collector material.
[0011]
The separator has a function of electrically connecting the power generation cells and supplying gas to the power generation cells. The fuel is introduced from the outer peripheral surface of the separator and discharged from the surface of the separator facing the fuel electrode layer. The separator has a passage and an oxidant passage for introducing an oxidant gas from the outer peripheral surface of the separator and discharging the oxidant gas from the surface of the separator facing the oxidant electrode layer.
[0012]
FIG. 4 shows an example of the configuration of the fuel cell stack 1, in which a power generation cell 5 in which a fuel electrode layer 3 and an air electrode layer 4 (oxidant electrode layer) are arranged on both surfaces of a solid electrolyte layer 2, and an outer side of the fuel electrode layer 3. , An air electrode current collector 7 outside the air electrode layer 4 (oxidizer electrode current collector), and a separator 8 outside each of the current collectors 6 and 7 were sequentially laminated. It has a structure and has a cylindrical shape as a whole.
[0013]
[Problems to be solved by the invention]
By the way, in such a flat plate type solid oxide fuel cell, particularly in a low-temperature operation type, a metal plate (stainless steel or the like) having a thickness of about 5 mm is used as a separator 8 for a power generation cell 5 having a size diameter of about 150 mm. An oxidant gas supply pipe 9 and a fuel gas supply pipe 10 for introducing a fuel gas and an oxidant gas into the fuel passage and the oxidant passage, respectively, are formed on the side surface having a thickness of about 5 mm so as to face each other. It has a connected structure.
In the drawing, reference numeral 11 denotes a discharge hole for the gas introduced from the gas supply pipe.
[0014]
However, such a separator structure has the following problems.
That is, (1) as described above, when the separator 8 is made of a single metal plate having a thickness of 5 mm, the heat capacity of the separator itself becomes large, and the responsiveness at the time of starting the fuel cell deteriorates (that is, the temperature rise). (2) The weight of the unit cell itself is increased, and the fuel cell stack 1 becomes larger and heavier when a stack structure is adopted.
And so on.
[0015]
In particular, in the case of solid oxide fuel cells, which are often configured with the battery stack placed vertically, the power generation cells arranged at the lower part are easily damaged by heavy pressure. There is also a problem that the number of layers to be obtained must be limited.
[0016]
To reduce the size, the thickness of the separator 8 may be reduced as much as possible (for example, about 2 mm in thickness). However, in the connection structure of the gas supply pipes described above, the diameter of the pipe is reduced as the thickness of the separator 8 is reduced. (In the above example, a pipe having an outer diameter of about 3.2 mm corresponding to the thickness of the separator 8 is used). There is a danger of pipe clogging due to carbon deposition during reforming of raw fuel (methane or natural gas), which is likely to occur in fuel cells, and therefore, the thickness of the separator cannot be reduced to a dark cloud.
[0017]
The present invention has been made in view of such a problem, and by using a gas supply pipe connecting mechanism that is not affected by the thickness of a separator, a flat plate type in which the fuel cell stack is made thinner and lighter. It is an object to provide a solid oxide fuel cell.
[0018]
[Means for Solving the Problems]
That is, the present invention according to claim 1 forms a power generation cell by arranging a fuel electrode layer and an oxidant electrode layer on both surfaces of a solid electrolyte layer, and the power generation cell is disposed via a separator having a gas flow path therein. In a flat plate type solid oxide fuel cell in which a plurality of fuel cells are stacked to constitute a fuel cell stack and a fuel gas and an oxidizing gas are supplied from the separator to the fuel electrode layer and the oxidizing electrode layer, the outer periphery of the separator In addition, a connecting portion that communicates with the gas flow path and is connected to a gas supply pipe from the outside is protruded outward, and the separators are arranged such that positions of adjacent connecting portions in the stacking direction are shifted. It is characterized by being stacked.
[0019]
According to a second aspect of the present invention, in the flat plate type solid oxide fuel cell according to the first aspect, the respective separators are arranged such that the respective connection portions are continuously shifted. It is characterized by.
[0020]
According to a third aspect of the present invention, in the flat plate type solid oxide fuel cell according to the first aspect, the separators are arranged such that the connecting portions are staggered. It is characterized by.
[0021]
According to a fourth aspect of the present invention, in the flat plate type solid oxide fuel cell according to any one of the first and second aspects, the gas supply pipe is provided in the connecting portion in the stacking direction. It is characterized by being connected.
[0022]
According to a fifth aspect of the present invention, in the flat plate type solid oxide fuel cell according to any one of the first to third aspects, the gas supply pipe is provided in the connecting portion in the stacking direction. And is connected horizontally.
[0023]
As in the above configuration, each connecting portion of the separator connected to the gas supply pipe protrudes (extends) to the outside of the separator, and the upper and lower connecting portions of the adjacent separator do not overlap each other at the time of lamination. By stacking while shifting the position of the connecting portion in the circumferential direction of the separator, it is possible to connect a gas supply pipe having a suitable outer diameter that does not adversely affect gas supply without being affected by the thickness of the separator. it can.
Therefore, the separator can be made thinner, and the fuel cell stack can be made smaller and lighter. In addition, the weight reduction can reduce the pressure on the battery cells located at the lower part of the stack, and the weight of the battery can be reduced. Cell destruction can also be prevented.
Note that the connecting portions located vertically may be continuously shifted in the circumferential direction of the separator, or may be staggered depending on the connection direction of the gas supply pipe.
[0024]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to FIGS. In order to simplify the description, in the following description, the same reference numerals are used for the same parts as those in the related art.
Here, FIGS. 1 and 2 show the structure of a separator to which the present invention is applied, and FIG. 3 shows the structure of a flat plate type solid oxide fuel cell assembled using the separator of FIG. .
[0025]
The fuel cell stack 1 according to the present embodiment includes a power generation cell 5 in which a fuel electrode layer 3 and an air electrode layer 4 (oxidant layer) are arranged on both surfaces of a solid electrolyte layer 2, and a fuel collector arranged outside the fuel electrode layer 3. A single cell is composed of the body 6, an air electrode current collector 7 (oxidant electrode current collector) disposed outside the air electrode layer 4, and a separator 8 disposed outside each current collector 7. 4 is substantially the same as that shown in FIG. 4, but the connection structure between the separator 8 and the gas supply pipe is different from that shown in FIG. 4. As a material, for example, a metal plate (such as stainless steel) having a thickness of 2 mm is used.
[0026]
That is, in FIG. 4, the gas supply pipes 9 and 10 are directly connected to the side surfaces thereof using the thickness of the disk-shaped separator 8, whereas in the first embodiment shown in FIG. 1, A connecting portion 14 and a connecting portion 15 to which the oxidizing gas supply pipe 9 and the fuel gas supply pipe 10 are connected at two places on the outer peripheral portion of the separator 8 are respectively extended outward in a rectangular shape. Has a connection structure that is not directly affected by the thickness of the separator 8.
[0027]
The connecting portion 14 communicates with the oxidizing agent passage 12 and connects an end of the oxidizing gas supply pipe 9 for introducing the oxidizing gas to a communication hole 14 a on the upper surface of the connecting portion 14 as shown in FIG. The oxidizing gas supply pipe 9 is connected to the oxidizing agent passage 12 in a state where the oxidizing gas supply pipe 9 is vertically connected by fitting (e.g., screw-in type) into the oxidizing gas passage 12.
The oxidant gas supplied from the outside is introduced into the oxidant passage 12 from the oxidant gas supply pipe 9 through the communication hole 14a of the connecting portion 14, and is discharged from the oxidant gas discharge hole 11b at the end of the passage. It is supplied to the facing air electrode current collector.
[0028]
On the other hand, the connecting portion 15 is communicated with the fuel passage 13, and the end of the fuel gas supply pipe 10 for introducing the fuel gas is fitted into the communication hole 15 a on the upper surface of the connecting portion 15 (for example, a screw-in type). Thus, they are connected in the vertical direction.
Fuel gas from the outside is introduced into the fuel passage 13 from the fuel gas supply pipe 10 through the communication hole 15a of the connecting portion 15, and is discharged from the fuel gas discharge hole 11a at the end of the passage to face the fuel electrode current collector. It is supplied to.
[0029]
Here, both the oxidizing agent passage 12 and the fuel passage 13 are formed inside the separator 8, and the discharge hole 11a of the fuel gas is opened on the surface side in FIG. It is assumed that the discharge hole 11b is open on the back side in FIG. In the connection structure, if the thickness of the separator 8 is about 2 mm, the thickness of each of the connecting portions 14 and 15 can be the same as that of the separator 8.
[0030]
Next, the second embodiment shown in FIG. 2 has a structure in which an oxidizing gas supply pipe 9 and a fuel gas supply pipe 10 are connected horizontally to the stacking direction.
[0031]
In the second embodiment, joints 14b and 15b are provided on the upper surface of the connecting portions 14 and 15, and the gas supply pipes 9 and 10 are provided with communication holes 14a provided on outer surfaces of the joints 14b and 15b. The joints 14b and 15b have a thickness corresponding to the outer diameter of each gas supply pipe to be connected.
Therefore, the oxidizing gas from the outside is introduced into the oxidizing passage 12 from the oxidizing gas supply pipe 9 through the communication hole 14a of the joint 14b, and is discharged from the oxidizing gas discharge hole 11b at the end of the passage to face the oxidizing gas. Supplied to the air electrode current collector.
[0032]
On the other hand, the fuel gas from the outside is introduced into the fuel passage 13 from the fuel gas supply pipe 10 through the communication hole 15a of the joint 15b, and is discharged from the fuel gas discharge hole 11a at the end of the passage to face the fuel electrode collecting surface. Supplied to the electrical body.
[0033]
FIG. 3 shows the internal structure of a flat plate type solid oxide fuel cell 20. In the present embodiment, a cylindrical type fuel cell is formed by stacking a number of single cells via the separator 8 shown in FIG. The battery stack 1 is provided.
[0034]
As shown in FIG. 3B, the separators 8 are arranged and stacked so that the positions of the connecting portions 14 and 15 adjacent in the laminating direction are continuously shifted in the circumferential direction.
Each fuel gas gas supply pipe 10 and oxidant gas supply pipe 9 are connected in the stacking direction (longitudinal direction) from the respective connection portions projecting on the periphery of the fuel cell stack 1, and as shown in FIG. A plurality of fuel gas supply pipes 10 and oxidant gas supply pipes 9 extending in parallel with the vertical direction are arranged in a circle in a side portion of a fuel distributor 17 and an oxidant distributor 16 disposed on the upper part of the battery, respectively. The fuel gas and the oxidizing gas are connected to each other in an arc shape, and the fuel gas and the oxidizing gas from the outside are once introduced into the fuel distributor 17 and the air distributor 16, where the fuel gas and the oxidizing gas are branched into a large number. Each of the separators 8 is supplied through a supply pipe 9.
In FIG. 3, reference numeral 19 denotes a holding plate for supporting and fixing a large number of stacked single cells in the stacking direction.
[0035]
Thus, in the present invention, as shown in FIGS. 1 and 2, the connecting portions 14 and 15 of the separator 8 connected to the gas supply pipes 9 and 10 have a structure extending outside the separator 8, Further, as shown in FIG. 3, the stacking is performed while shifting the positions of the connecting portions 14 and 15 in the circumferential direction of the separator 8 so that the connecting portions of the stacked upper and lower separators 8 do not overlap each other. The gas supply pipes 9 and 10 having a suitable outer diameter (3.2 mm) which are not affected by the thickness (2 mm) of the gas supply pipes can be connected.
[0036]
As described above, if the thickness of the separator 8 can be made smaller than the outer diameter of the gas supply pipes 9, 10, the fuel cell stack 1 can be reduced in size and weight by making the separator 8 thinner. In addition, the weight reduction can reduce the pressure on the battery cells located at the lower part of the stack, and can prevent the power generation cells 5 from being damaged by the load. As a result, the number of stackable battery stacks can be increased as compared with the related art, and accordingly, high electromotive force power generation can be realized. Further, as the size and weight are reduced, the support structure of the fuel cell stack 1 can be simplified as in the pressing plate 19 shown in FIG.
[0037]
Although not shown, such a solid oxide fuel cell 20 can also be configured using the separator 8 shown in FIG. In this configuration, the separators 8 can be arranged such that the positions of the connecting portions 14 and 15 adjacent to each other in the stacking direction are staggered in the circumferential direction.
[0038]
Each of the gas supply pipes 9, 10 protruding on the periphery of the fuel cell stack 1 is connected to each of the gas supply pipes 9, 10 from the connection portions 14, 15 in a direction perpendicular to the lamination direction (lateral direction), and extends in a state of two rows in parallel. The gas supply pipes 9 and 10 are connected in a staggered manner to the sides of the fuel distributors (oxidant distributors) that extend in the stacking direction.
Also in this case, similarly to the above, the gas supply pipes 9 and 10 having a suitable outer diameter (3.2 mm) which are not affected by the thickness (2 mm) of the separator 8 are provided to the joints 14 b and 15 b of the connecting portions 14 and 15. The separator 8 can be connected, and thus the thickness of the separator 8 can be reduced. In the separator of FIG. 2, the separator 8 may be arranged so that the positions of the connecting portions vertically adjacent to each other are continuously shifted in the circumferential direction.
[0039]
As described above, in the present embodiment, the separator 8 made of a single metal plate has been described. However, the present invention is not limited to this. It is also possible to use a lighter separator 8 which is laminated with a metal thin plate processed into an uneven shape for forming the same.
[0040]
【The invention's effect】
As described above, according to the present invention, the connecting portion of the separator connected to the gas supply pipe is projected outside the separator, and when stacked, the connecting portions of the adjacent upper and lower separators are not overlapped. By stacking while shifting the position of the connecting portion in the circumferential direction of the separator, it is possible to connect a gas supply pipe having a suitable outer diameter which is not affected by the thickness of the separator.
Therefore, the thickness of the separator can be reduced, and the size and weight of the fuel cell stack can be reduced. In addition, by reducing the weight, the pressure on the battery cells located at the lower part of the stack can be reduced, and the power generation cells can be prevented from being damaged by the load.
[Brief description of the drawings]
FIG. 1 is a view showing a structure of a separator to which the present invention is applied, wherein (a) is a plan view and (b) is a front view.
FIGS. 2A and 2B are diagrams showing a structure of a separator different from FIG. 1 to which the present invention is applied, wherein FIG. 2A is a plan view and FIG.
3A and 3B are diagrams showing a flat-plate stacked solid oxide fuel cell assembled using the separator of FIG. 1, wherein FIG. 3A is a plan view and FIG. 3B is a front sectional view.
FIG. 4 is an exploded perspective view showing one configuration example of the fuel cell stack 1.
[Explanation of symbols]
Reference Signs List 1 fuel cell stack 2 solid electrolyte layer 3 fuel electrode layer 4 oxidizer electrode layer (air electrode layer)
5 Power generation cell 8 Separator 9, 10 Gas supply pipe (oxidant gas supply pipe, fuel gas supply pipe)
12, 13 gas passage (oxidant passage, fuel passage)
14, 15 connecting part 20 solid oxide fuel cell

Claims (5)

A fuel cell layer is formed by arranging a fuel electrode layer and an oxidizer electrode layer on both surfaces of a solid electrolyte layer, and forming a fuel cell stack by stacking a large number of the power generation cells via a separator having a gas flow path therein. In a flat-plate stacked solid oxide fuel cell that supplies a fuel gas and an oxidant gas to the fuel electrode layer and the oxidant electrode layer from a separator,
On the outer peripheral portion of the separator, a connecting portion which communicates with the gas flow path and to which a gas supply pipe from the outside is connected is protruded outward, and the position of each connecting portion adjacent in the stacking direction is shifted. A flat-plate stacked solid oxide fuel cell, wherein each separator is arranged and stacked. 2. The solid oxide fuel cell according to claim 1, wherein the separators are arranged such that the connection portions are continuously shifted. 3. 2. The solid oxide fuel cell according to claim 1, wherein the separators are arranged such that the connection portions are staggered. 3. The flat-plate stacked solid oxide fuel cell according to claim 1, wherein the gas supply pipe is connected to the connection portion in a stacking direction. The flat-plate laminated solid oxide fuel cell according to any one of claims 1 to 3, wherein the gas supply pipe is connected to the connecting portion in a direction parallel to the lamination direction.

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