JP3995778B2 - Solid electrolyte fuel cell and stack structure of solid oxide fuel cell - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a unit cell manifold structure and a stack structure of a solid oxide fuel cell.
[0002]
[Prior art]
Solid oxide fuel cells (SOFC) are roughly classified into flat plate types and cylindrical types (Energy Integrated Engineering 13-2, 1990). Since the electromotive force of the SOFC unit cell is about 1 V in open circuit and the current density is about several hundred mA / cm ² at the time of actual use, the unit cells having a large power generation area can be easily connected in series or in parallel. It is important to be able to connect. From this point of view, the structure of the cell and its stack (collective cell) must be considered.
[0003]
In particular, in a stack structure of a solid oxide fuel cell, it is required to maintain airtightness between the oxidizing gas and the fuel gas at the operating temperature of the power generator. For example, in a so-called Westinghouse type solid oxide fuel cell, a cylindrical air electrode is used as a base, and a solid electrolyte membrane and a fuel electrode membrane are formed thereon. Further, the applicant of the present invention also relates to a flat unit cell having a structure in which a laminated sintered body composed of an air electrode and an interconnector is used as an air electrode / interconnector base, and a solid electrolyte membrane and a fuel electrode membrane are formed thereon. Disclosed (Japanese Patent Laid-Open No. 5-166518). In these stack structures, a so-called sealless structure is employed. That is, an oxidizing gas supply pipe is inserted into each oxidizing gas passage formed in each unit cell, and the oxidizing gas is supplied from each oxidizing gas supply pipe to the inside of the unit cell. Then, the exhaust oxidant gas discharged from each oxidant gas passage of the unit cell is guided to flow into the combustion chamber, and is reacted with the exhaust fuel gas in the combustion chamber.
[0004]
However, in this method, for example, as disclosed in Japanese Patent Application Laid-Open No. 5-166518, for example, three or more oxidizing gas passages are provided in a single cell, and a gas supply pipe is provided in each oxidizing gas passage. It is necessary to insert. For this reason, many gas supply pipes are needed, and it is necessary to insert each gas supply pipe into each oxidizing gas passage of each unit cell separately.
[0005]
On the other hand, several methods for stacking a plurality of unit cells having a plurality of oxidizing gas passages to form a so-called stack structure have been proposed (for example, Japanese Patent Laid-Open No. 7-226220). In this stack structure, a stack of unit cells having a rectangular parallelepiped shape is formed. In this stack, the individual cells are connected in series. Thereafter, current collector plates are brought into contact with the uppermost end portion and the lowermost end portion of the stack, respectively, and the stack and the current collector plate are accommodated in a metal outer shell and fixed. In this case, a heat insulating material layer is provided inside the outer shell. Then, the oxidizing gas is supplied to the oxidizing gas passage provided in the unit cell, and at the same time, the fuel gas is caused to flow inside the heat insulating layer, and the fuel gas is brought into contact with the fuel electrode outside each unit cell. Power generation is performed in a single cell. The electric power of the plurality of single cells connected in series is taken out from the pair of current collector plates.
[0006]
Then, air manifolds are respectively installed on two opposing surfaces of the four rounds of the unit cell stack, and air is allowed to flow from one manifold to the other manifold. In addition, fuel manifolds are provided on the remaining two opposing surfaces of the four rounds of the unit cell stack, and fuel gas flows from one manifold to the other manifold.
[0007]
[Problems to be solved by the invention]
However, the following problems remain in the cell stack structure as described above. For example, in the stack structure disclosed in Japanese Patent Application Laid-Open No. 7-226220, an oxidizing gas manifold member is fixed to two opposing surfaces among the four surfaces of a stack composed of a plurality of unit cells, and the stack and each manifold member are The gap is sealed rigidly with a gasket or sealing material to prevent mixing of oxidizing gas and fuel gas. In such a structure, a large number of single cells are rigidly fixed to the manifold member, and the space between the manifold member and each single cell is hermetically sealed.
[0008]
However, when power is actually generated, the airtightness at the boundary between the manifold member and the stack tends to decrease, and this tendency becomes more prominent as the operation time becomes longer. When this airtightness is lowered, it causes a reduction in power generation efficiency and electromotive force.
[0009]
An object of the present invention is to prevent a decrease in hermeticity at the boundary between a manifold member and a single cell even when the battery is operated for a long time, particularly in a solid oxide fuel cell having a plurality of gas passages, It is to be able to prevent a drop in electromotive force.
[0010]
[Means for Solving the Problems]
Solid oxide fuel cell according to the present invention, between the air electrode, the fuel electrode and comprises a solid electrolyte, and gas passage for the flow of one of the power generation gas is one end surface and other end surface even without least a unit cell which is provided a plurality of rows so as to extend in, for the introduction or evacuation of the one of the power generation gas to each gas passage of the, attached to said one end face of the unit cell a manifold member comprises a ceramic gas flow pipe which is attached to this manifold member, said manifold member, said projecting wall protruding toward towards said one end face of the unit cell A cell fixing space for inserting and fixing the end of the unit cell is formed inside the protruding wall, and the unit cell fixing space communicates with the gas distribution space. And wherein the Rukoto.
[0011]
In addition, the present invention provides a stack structure including the solid oxide fuel cell , a plurality of unit cells, a plurality of manifold members separately attached to the plurality of unit cells, and a plurality of unit cells. And a container for housing the unit cell.
[0012]
As a result of examining the cause of the decrease in airtightness at the boundary between the manifold member and the stack, the present inventor has obtained the following knowledge. That is, the temperature inside the container that accommodates the stack reaches 1000 ° C. or higher during power generation, but at this time, the temperature of each single cell constituting the stack is not necessarily uniform. The cells at the top and bottom of the stack have a relatively low gas temperature, and the power generation efficiency tends to be low. However, in the single cell at the center of the stack, especially in the oxidizing gas passage near the center of the single cell, exhaust heat is concentrated, the temperature of the single cell rises, and this cell rise further increases the activity of the single cell. Therefore, the temperature of the central part of the stack tends to increase. This tendency becomes stronger as power generation time becomes longer.
[0013]
On the other hand, the thermal expansion coefficients of the unit cell, the metal manifold member, and the sealant interposed therebetween are different. At the time of operation, each cell constituting the stack and the manifold member have different degrees of thermal expansion, so stress concentrates near the boundary between the manifold member and the cell, particularly around the seal material. At this time, particularly in the unit cell located near the center of the stack, the difference in thermal expansion between the unit cell and the manifold member is large, whereas in the unit cell in the peripheral portion of the stack, the thermal expansion between the unit cell and the manifold member is large. The difference is small. Due to this difference in thermal expansion, it is considered that a thermal stress that causes a positional shift acts on the seal material between the manifold member and the single cell.
[0014]
In contrast, the present inventor separately prepares a manifold member for each unit cell, attaches the manifold member to one end surface side of the unit cell, and attaches a ceramic gas flow pipe to the manifold member. It has been conceived that the manifold member is provided with a gas distribution space communicating with the gas flow holes of the gas flow pipe and the plurality of rows of gas passages.
[0015]
Thereby, gas can be supplied from one manifold member to the plurality of gas passages of the unit cell. In addition, since the area of the seal portion between each unit cell and each corresponding manifold member is small, the sum of thermal stress due to the temperature difference in each part of the stack is concentrated on some unit cells. There is no. That is, the distortion concentrated on the boundary portion between each unit cell and each manifold member is small.
[0016]
Moreover, even when the degree of expansion and contraction of the individual cells constituting the stack is different, the individual cells can move relative to each other. At the same time, there is room for each gas supply pipe to change its direction and rotate in accordance with the minute position movement of each unit cell and absorb the relative position movement of each unit cell.
[0017]
In the present invention, the manifold member, member for supplying the power generation gas to each gas passage of the cell or from the gas passage of the cell, meaning the member for discharging the depleted power generation gas To do. Accordingly, the gas flow pipe becomes a gas supply pipe or a gas discharge pipe.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
When oxidizing gas is used as one power generating gas, fuel gas is used as the other power generating gas, and when oxidizing gas is used as the other power generating gas, fuel gas is used as one power generating gas. Is used.
[0019]
The material of the gas flow pipe and the manifold member must have heat resistance, durability against oxidizing gas and fuel gas. As such a material, alumina, alumina-magnesia spinel, and zirconia are preferable.
[0020]
In the present invention, the manifold member further includes a protruding wall portion protruding toward one end face of the unit cell, and the end portion of the unit cell is inserted and fixed inside the protruding wall portion. It is preferable to form a unit cell fixing space for communication and communicate the unit cell fixing space with the gas distribution space. At this time, if the protruding wall portions are in close contact with at least a pair of main surfaces of the unit cell , the airtightness of the solid oxide fuel cell is broken even with respect to stress acting in the main surface direction of the unit cell. more preferred because the Ku rather than made. In this case, by further bringing the projecting wall portion into close contact with the pair of side surfaces of the unit cell, the airtightness of the seal portion at the boundary between the manifold member and the unit cell is further maintained.
[0021]
These embodiments will be described in more detail with reference to FIGS.
[0022]
FIG. 1 is a cross-sectional view of a unit cell 1 used in an embodiment of the present invention. 4 is a longitudinal sectional view showing a stack structure 8 using a stack 36 in which, for example, three unit cells of FIG. 1 are connected in series, and FIG. 5 is a transverse sectional view of the stack structure 8 of FIG. . 2A to 2C show the manifold member 41, and FIG. 3 is a plan view for explaining a connection state between each unit cell 1 and each manifold member 41.
[0023]
First, the entire stack structure 8 will be described, and then the details of the solid oxide fuel cell will be described.
[0024]
A support 2 of the unit cell 1 (1A, 1B, 1C) is composed of an air electrode plate 3 and a separator 4. The planar shape of the separator 4 is a rectangle. A pair of elongated side walls 4 a is formed at the edge of the flat plate-like main body of the separator 4 in the cross-sectional direction. Each side wall 4a has a quadrangular prism shape and extends from one end of the separator 4 in the longitudinal direction to the other end.
[0025]
For example, three rows of quadrangular prism-shaped partition walls 4b are provided between the pair of side walls 4a. Each partition wall 4b extends in parallel with each other from one end of the separator 4 in the longitudinal direction to the other end. For example, a total of four rows of grooves parallel to each other are formed between the side wall 4a and the partition wall 4b.
[0026]
The planar shape of the air electrode plate 3 is the same as the planar shape of the separator 4. A pair of elongate side walls 3a are formed at the edge of the flat plate body of the air electrode plate 3 in the cross-sectional direction, and three columns of square columnar partition walls 3b are provided between the pair of side walls 3a, for example. Yes. For example, a total of four rows of grooves parallel to each other are formed between the side wall 3a and the partition wall 3b. Each side wall 4 a of the separator 4 is joined to each side wall 3 a of the air electrode 3, and each partition 4 b of the separator 4 is joined to each partition 3 b of the air electrode plate 3. As a result, for example, four rows of oxidizing gas passages 5 are formed between the air electrode plate 3 and the separator 4.
[0027]
The solid electrolyte membrane 6 covers the main surface 3 c and the side surface 3 d of the air electrode 3, and further covers the upper part of the width side surface 4 d of the separator 4. Both the oxidizing gas passage 5 and the side surface 3d of the air electrode 3 are surrounded by a separator 4 and a solid electrolyte membrane 6 which are airtight. A fuel electrode membrane 7 is formed on the solid electrolyte membrane 6.
[0028]
Stacks such as shown in FIGS. 4 and 5 are configured by stacking and connecting the single cells as shown in FIG. 1 in series. In the stack 36, for example, three unit cells 1A, 1B, and 1C are stacked. Each main surface 4c of each separator 4 of each unit cell 1A, 1B is connected to each fuel electrode membrane 7 of each lower unit cell 1B, 1C via a breathable conductive material 17, respectively. Yes. As the breathable conductive material, nickel felt and nickel sponge are preferable.
[0029]
In the present embodiment, one current collector 12A and the other current collector 12B are combined to produce the container 32. At this time, the container 32 is assembled after the stack 36 is sandwiched between the current collector plates 12A and 12B.
[0030]
Each of the current collecting plates 12A and 12B includes a flat plate portion 12a, side plate portions 12b and 12d, and a protruding portion 12c. The protruding portion 12c of the current collector plate 12A and the protruding portion 12c of the current collector plate 12B are aligned as shown in FIG. 5, and the insulating member 13 is sandwiched between the protruding portions. Then, for example, each projecting portion 12c of each current collector plate 12A, 12B is fastened by a fastening member including a bolt 33 and a nut 34, and pressure is applied as indicated by an arrow A by adjusting the fastening force of the bolt. Thus, the protruding portion 14 of the container 32 is configured.
[0031]
As a result, the stack 36 of unit cells connected in series is housed and fixed in the power generation region 38 inside the container 32. In this state, a predetermined pressure is applied to each unit cell in the direction A in which the unit cells are stacked. The unit cell 1A of the stack is connected to the current collector plate 12A through the air-permeable conductive material 16, and the cell 1C is connected to the current collector plate 12B through the conductive material 16. The heat insulating layers 11A and 11B are provided outside the current collector plates 12A and 12B, and the outer shells 10A and 10B are provided outside the respective heat insulating layers. Each bolt 33 penetrates each outer shell and each heat insulating material layer.
[0032]
In FIG. 4, a combustion region 30, a power generation region 38, a preheating chamber 19, and an oxidizing gas chamber 24 are provided in order from the left side. The stack shown in FIG. 5 shows the state of the power generation region 38 in FIG. The oxidizing gas chamber 24 and the preheating chamber 19 are separated by an airtight partition wall 20, and the preheating chamber 19 and the power generation chamber are also separated by an airtight partition wall 44.
[0033]
Corresponding to each unit cell, each oxidizing gas supply pipe 42 is provided. The right end of each supply pipe 42 opens into the oxidizing gas chamber 24, and each supply pipe 42 passes through the partition wall 20, the preheating chamber 19, and the partition wall 44, and is connected to one end face 1 a side of each unit cell by the manifold member 41. It is attached to. 44a and 20a are through-holes of the respective partition walls.
[0034]
A solid oxide fuel cell will be described. 2 (a) is a front view of the manifold member 41, FIG. 2 (b) is a plan view showing a state where the supply pipe 42 is attached to the member 41, and FIG. 2 (c) is a longitudinal sectional view thereof. . FIG. 3 is a plan view showing a state in which the manifold member and the unit cell 1 are combined.
[0035]
As shown in FIG. 4, the manifold member 41 is attached to each end of each unit cell. A pair of projecting wall portions 41a and 41b are provided on the unit cell side of the member 41, and a unit cell fixing space 41d is formed between the projecting wall portions 41a and 41b. A fixed space 41e for the supply pipe is provided on the opposite side of the fixed space 41d, and the single cell fixed space 41d and the fixed space 41e for the supply pipe communicate with the distribution space 41c.
[0036]
The end 42a of the supply pipe 42 is inserted into the fixed space 41e, and the end face 42b of the supply pipe 42 faces the rectangular parallelepiped distribution space 41c. On the other hand, one end 1a of the unit cell 1 is inserted into the fixed space 41d, and the protruding wall portions 41a and 41b are in close contact with the main surfaces 1e and 1f (see FIGS. 4 and 5) of the unit cell. is doing.
[0037]
As shown in FIGS. 3 and 4, the oxidizing gas is supplied from the outside of the outer shells 10 </ b> A and 10 </ b> B to the oxidizing gas chamber 24 as indicated by an arrow B through the supply port 26 and enters each supply pipe 42. The gas flows through the gas flow holes 42c of the supply pipes as indicated by arrows C. Then, it flows into the distribution space 41 c from the end face 42 b of the supply pipe 42, then enters one opening 5 a of each gas passage 5 of the unit cell 1, flows through each gas passage 5, and the other end surface of the unit cell 1. As indicated by the arrow D, the other opening 5b on the 1b side is discharged into the combustion region 30, where it reacts with the fuel gas.
[0038]
Further, the fuel gas is supplied from the outside of the outer shell into the power generation chamber as indicated by the arrow E, flows between the single cells, and through the gap 15 between the single cells and the container as indicated by the arrow F, and enters the combustion region 30. Inflow.
[0039]
In the combustion region 30, the depleted fuel gas reacts with the depleted oxidizing gas and burns. The combustion exhaust gas flows through the exhaust gas pipe 25 as indicated by arrows G and H, is supplied into the preheating chamber 19, and is discharged from the preheating chamber 19 through the discharge port 27 as indicated by arrow I. With the waste heat of the combustion exhaust gas, as shown by an arrow C, the oxidizing gas flowing through the gas flow holes 42c of the supply pipes 42 can be preheated.
[0040]
In the present embodiment, a structure for urging the supply pipe toward the unit cell is provided at the supply-side end of each supply pipe 42. That is, at the supply side end on the right side of each supply pipe 42, a movable seal device 40 is installed on the partition wall 20, and each supply pipe 42 and each partition wall 20 are arranged in a direction perpendicular to the airtight partition wall 20. It can move while maintaining airtightness with the supply pipe 42. The movable sealing device 40 includes an O-ring 22 and a pressing member 21 that presses each O-ring 22 with a predetermined pressure. Further, a predetermined urging member 23 is attached to the end face of each supply pipe 42, and each supply pipe 42 is urged at a constant pressure toward the corresponding unit cell. Yes.
[0041]
As in the present embodiment, it is preferable to employ a structure in which the preheating chamber 19 is provided and the gas in the supply pipe 42 is preheated. This eliminates the need to provide a preheating chamber separate from the stack structure outside the stack structure 8.
[0042]
In the present invention, a temperature gradient of 700 ° C. or more between one end portion 42a attached to the manifold member and the other end portion of the gas flow tube among the gas flow tubes (for example, 42). Is preferably provided. This eliminates the need for thick insulation on the outer shell of the stack structure. Further, an O-ring made of silicon rubber can be used for the movable seal portion.
[0043]
In addition, it is particularly preferable that the protruding wall portion of the manifold member is in close contact with the pair of main surfaces of the unit cell, and is also in close contact with the pair of side surfaces of the unit cell. FIG. 6A is a front view showing such a manifold member 43, FIG. 6B is a plan view showing a state in which the supply pipe 42 is attached to the member 43, and FIG. 4 is a longitudinal sectional view showing a state in which a supply pipe 42 is attached to 43. FIG.
[0044]
As shown in FIG. 4, the manifold member 43 is also attached to each end of each unit cell. Four rows of protruding wall portions 43a, 43b, 43f, 43g are provided on the unit cell side of the member 43, and a unit cell fixing space 43d is formed therebetween. On the opposite side of the fixed space 43d, a fixed space 43e for the supply pipe is provided. The unit cell fixed space 43d and the supply pipe fixed space 43e communicate with the distribution space 43c.
[0045]
One end 42a of the supply pipe 42 is inserted into the fixed space 43e, and the end face 42b of the supply pipe 42 faces the rectangular parallelepiped distribution space 43c. One end 1a of the unit cell 1 is inserted into the fixed space 43d. The opposing protruding wall portions 43a and 43b are in close contact with the main surfaces 1e and 1f (see FIGS. 3, 4 and 5) of the single cell, and the opposing protruding wall portions 43f and 43g are the single cell. Are closely attached to side surfaces 1c and 1d (see FIG. 3).
[0046]
【The invention's effect】
As described above, according to the present invention, in a solid oxide fuel cell having a plurality of gas passages, even when the cell is operated for a long time, deterioration in airtightness at the boundary between the manifold member and the unit cell is prevented. In addition, it is possible to prevent a decrease in power generation efficiency and electromotive force.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a cell 1 that can be used in an embodiment of the present invention.
2A is a front view of a manifold member 41, FIG. 2B is a plan view showing a state where a supply pipe 42 is attached to the member 41, and FIG. 2C is a longitudinal sectional view thereof.
FIG. 3 is a plan view showing a state in which the manifold member and the unit cell 1 are combined.
4 is a longitudinal sectional view showing a stack structure 8 in which a stack 36 obtained by stacking unit cells of FIG. 1 is accommodated in a container. FIG.
5 is a cross-sectional view schematically showing the stack structure 8 of FIG.
6A is a front view of another manifold member 43, FIG. 6B is a plan view showing a state where a supply pipe 42 is attached to the member 43, and FIG. 6C is a longitudinal sectional view thereof; It is.
[Explanation of symbols]
1, 1A, 1B, 1C unit cell, 2 unit cell support, 3 air electrode plate, 4 separator, 5 oxidizing gas passage, 6 solid electrolyte membrane, 7 fuel electrode membrane, 8 stack structure, 10A, 10B outer shell, 11A, 11B insulation layer, 12A current collector plate, 12B other current collector plate, 13 insulating member, 14 container protrusion, 15 fuel gas passage, 19 preheating chamber, 24 oxidizing gas chamber, 30 combustion region, 32 Container, 36 Stack, 38 Power generation area of power generation chamber, 40 Movable seal device, 41, 43 Manifold member, 41a, 41b, 43a, 43b Protruding wall portion in close contact with main surface of unit cell, 41c, 43c Distribution space, 41d 43d single cell fixed space, 41e, 43e fixed space for gas flow pipe, 42 oxidizing gas supply pipe, 42a one end of oxidizing gas supply pipe, 42c gas flow hole for oxidizing gas supply pipe, 4 f, 43 g protruding wall portion in close contact with the pair of side surfaces of the cells, B, C, the flow of D oxidizing gas, E, flow F fuel gas, G, H, the flow of I flue gas

Claims (7)

Even without least an air electrode, provided with a fuel electrode and a solid electrolyte, and a single gas passage for flowing one of the power generation gas is provided a plurality of rows so as to extend between one end face and the other end face a battery, for the introduction or evacuation of the one of the power generation gas to each gas passage of the, and the manifold member is mounted on said one end face of the unit cell, attached to the manifold member It is provided with a ceramic gas flow pipe and,
The manifold member is provided with a gas distribution space communicating with the gas flow holes of the gas flow pipe and the plurality of rows of gas passages, and the manifold member is formed on the one end surface of the unit cell. A projecting wall portion projecting toward the direction, and an end portion of the unit cell is inserted and fixed inside the projecting wall portion, and the unit cell fixing space is formed. A solid oxide fuel cell, wherein a space communicates with the gas distribution space . It said manifold member, characterized in that said a manifold member for supplying the power generation gas of said one for each gas passage, the solid electrolyte fuel cell according to claim 1, wherein. In the unit cell, a pair of opposing main surfaces and a pair of side surfaces opposing each other are formed between the one end surface and the other end surface, and the end of the unit cell is disposed in the unit cell fixing space. The solid oxide fuel cell according to claim 1 or 2, wherein a portion is inserted and fixed, and the protruding wall portion is in close contact with at least the pair of main surfaces of the unit cell . 4. The solid oxide fuel cell according to claim 3, wherein the protruding wall portions are in close contact with the pair of side surfaces of the unit cell . A gas flow pipe fixing space for inserting and fixing an end of the gas flow pipe into the manifold member is formed, and the gas flow pipe fixing space communicates with the gas distribution space. The solid oxide fuel cell according to any one of claims 1 to 4 . A stack structure comprising the solid oxide fuel cell according to claim 1,
The stack structure includes a plurality of the unit cells, a manifold member separately attached to each of the plurality of unit cells, and a container for housing the plurality of unit cells. , Stack structure of solid oxide fuel cell. A temperature difference of 700 ° C. or more is provided during power generation between one end of the gas flow pipe attached to the manifold member and the other end of the gas flow pipe. The stack structure of a solid oxide fuel cell according to claim 6.

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