JP2010238436A - Solid oxide fuel battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To attain uniformity of temperature distribution in lamination direction of a fuel battery cell stack. <P>SOLUTION: A cooling separator 80 is laminated at an optional part in lamination direction of a fuel battery cell stack 101, and a cooling dedicated passage 83 in which cooling air can be circulated and the air after circulation is discharged from a separate exit 83a which is not communicated with a reaction gas ejection hole 12a is installed in the cooling separator. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a solid oxide fuel cell having a stack structure in which power generation cells and separators are alternately stacked, and more particularly to a solid oxide fuel cell in which the temperature is uniform in the stacking direction of the stack.

  In recent years, solid oxide fuel cells that directly convert chemical energy of fuel into electrical energy have attracted attention as high-efficiency and clean power generators. This solid oxide fuel cell has a stacked structure in which a solid electrolyte layer made of an oxide ion conductor is sandwiched between an air electrode layer (cathode) and a fuel electrode layer (anode) from both sides.

During power generation, an oxidant gas (oxygen) is supplied to the air electrode layer side and a fuel gas (H ₂ , CO, CH _4, etc.) is supplied to the fuel electrode layer side as a reaction gas. The air electrode layer and the fuel electrode layer are both porous layers so that the reaction gas can reach the interface with the solid electrolyte layer.

Oxygen supplied to the air electrode layer passes through the pores in the air electrode layer and reaches the vicinity of the interface with the solid electrolyte layer, and receives electrons from the air electrode layer at this portion to receive oxide ions (O ²⁻ ). Is ionized. The oxide ions diffuse and move in the solid electrolyte layer toward the fuel electrode layer, and the oxide ions that reach the vicinity of the interface with the fuel electrode layer react with the fuel gas at this portion to react with the reaction product (H ₂ O, CO _2, etc.) are generated and electrons are emitted to the fuel electrode layer. Electrons generated in the electrode reaction (power generation reaction) can be taken out as an electromotive force at an external load on another route.

  A flat-stacked solid oxide fuel cell stacks a plurality of power generation cells, current collectors, and separators alternately, and stacks them, and loads in this stack (this is called a fuel cell stack) in the stacking direction. And the above-described constituent elements are pressed and brought into close contact with each other.

  By the way, in the flat plate type fuel cell stack described above, the cell temperature (separator temperature) at the middle stage of the stack tends to be extremely higher than the cell temperature at the end of the stack. This is due to the fact that the fuel cell stack has a laminated structure, so that the heat dissipation of the middle stage is poor compared to both ends, and it is difficult for the Joule heat generated during power generation to be dissipated outside the cell.

  When a temperature difference occurs in the stacking direction of the fuel cell stack, the concentration of the circulating gas decreases in the high temperature part, and the uniform distribution of the reaction gas to each power generation cell collapses, resulting in nonuniform cell voltage. It will be. In a fuel cell stack configured by connecting a large number of power generation cells in series, if such voltage non-uniformity occurs in each power generation cell, the total output of the fuel cell is limited by some low voltage cells. Therefore, efficient power generation cannot be performed.

  Therefore, as a technique for equalizing the temperature of the fuel cell stack, the following Patent Document 1 discloses a fuel cell in which a radiator is disposed between separators in the middle part of the fuel cell stack in the stacking direction.

  FIG. 11 is a configuration diagram of the fuel cell stack described in Patent Document 1, FIG. 12 is a perspective view showing the configuration of the heat radiator, and FIG. 13 is a diagram showing the flow of reaction gas in the fuel cell stack in which the heat radiator is laminated. It is.

  As shown in FIG. 11, the fuel cell stack 1 is disposed outside the fuel electrode layer 3 and the power generation cell 5 configured by disposing the fuel electrode layer 3 and the air electrode layer 4 on both surfaces of the solid electrolyte layer 2. A large number of unit cells 10 each including a fuel electrode current collector 6, an air electrode current collector 7 disposed outside the air electrode layer 4, and a separator 8 disposed outside each current collector 6, 7 are stacked. Configured.

Here, for example, the solid electrolyte layer 2 is made of stabilized zirconia (YSZ) or the like to which yttria is added, and the fuel electrode layer 3 is made of a metal such as Ni or Co, or a cermet such as Ni-YSZ or Co-YSZ. The air electrode layer 4 is made of LaMnO ₃ , LaCoO ₃ or the like, the fuel electrode current collector 6 is made of a sponge-like porous sintered metal plate such as a Ni-based alloy, and the air electrode current collector 7 is made of Ag. The separator 8 is made of stainless steel or the like, and is made of a sponge-like porous sintered metal plate such as a base alloy.

  The separator 8 has a function of electrically connecting the power generation cells 5 and supplying a reaction gas to the power generation cells 5, and introduces a fuel gas from the outer periphery of the separator 8 to provide fuel for the separator 8. A fuel gas passage 11 that is discharged from a reaction gas discharge hole 11a located at substantially the center of the surface facing the electrode current collector 6 and an oxidant gas introduced from the outer periphery of the separator 8 to collect the air electrode current collector of the separator 8 It has an oxidant gas passage 12 that is discharged from a reaction gas discharge hole 12a located substantially at the center of the surface facing the body 7.

  In addition, a fuel gas manifold 13 and an oxidant gas manifold 14 extending in the stacking direction are formed inside the fuel cell stack 1, and the fuel gas passages 11 of the separators 8 are provided in the fuel gas manifold 13. The oxidant gas passages 14 of the separators communicate with the oxidant gas manifold 14.

  During operation, fuel gas and oxidant gas (air) supplied from the outside are introduced into the manifolds 13 and 14, and each reaction gas is collected through the gas passages 11 and 12 of the separators 8. It discharges to the electric current collector 6 side and the air current collector 7 side, diffuses and moves inside the current collectors 6 and 7 and is guided to each electrode of each power generation cell 5 to generate a power generation reaction.

  This fuel cell stack 1 employs a sealless structure in which a gas leak prevention seal is not provided on the outer periphery of the power generation cell 5, and surplus gas (exhaust gas) that has not been consumed in the power generation reaction is removed from the outer periphery of the power generation cell. It is designed to release freely. Further, the Joule heat of the power generation cell portion generated during the power generation reaction is thermally conducted to the adjacent separator 8 and is radiated from the outer peripheral portion of the separator 8.

  In the fuel cell stack 1, the heat dissipating body 20 is disposed so that the upper and lower sides are sandwiched between the separators 8 in the vicinity of the middle stage in the stacking direction. The heat dissipating body 20 is made of a metal having excellent thermal conductivity. As shown in FIG. 12, as shown in FIG. 12, a cylindrical support portion 22 and a plurality of sheets projecting radially from the peripheral side surface of the support portion 22. A heat dissipating plate member 23 (heat dissipating fins 23) and flange portions 21, 21 provided at both upper and lower ends of the support portion 22 are provided, and the support portion 22 is arranged so as to be located at substantially the center in the surface direction of the fuel cell stack 1. It is installed.

  Here, the flange portion 21 is disposed in an intimately integrated manner between the separator 8 and the separator 8, so that good electrical contact with the adjacent separators 8, 8 can be obtained. . The support portion 22 mainly serves as a cell current path and supports a load in the stacking direction applied to the upper flange portion 21.

  By disposing the support portion 22 at a substantially central portion in the stack surface direction, the stack current that concentrates in the central portion of the power generation cell 5 and flows in the stacking direction can be efficiently relayed to the next power generation cell 5. . The support portion 22 may be solid or hollow, and in the case of being hollow, a large number of holes are provided in the peripheral wall for allowing a heat reservoir generated in the hollow portion to escape to the outside.

  In addition, since the radiating fins 23 are provided radially around the support portion 22, the radiating effect by the radiating fins 23 is improved.

  Thus, when the radiator 20 is disposed in an intimately integrated manner between the separators 8 and 8, the Joule heat from the power generation cells 5 in the middle stage of the stack where the temperature inside the stack tends to be relatively high. Can be thermally conducted from the entire surface of the adjacent separators 8 and 8 to efficiently radiate heat from the heat radiation fins 23.

  As a result, the temperature difference across the stacking direction can be reduced so that the temperature of the stack middle stage approaches the temperature of the stack upper and lower stages, thereby achieving a uniform temperature distribution in the stack stacking direction. Thus, the voltage distribution in each power generation cell 5 can be suppressed, and the temperature of the entire stack can be maintained in a predetermined temperature range suitable for the power generation reaction temperature. Therefore, efficient power generation that is not restricted by some low-voltage cells can be performed, and damage to the power generation cell 5 such as peeling of the electrode layers 3 and 4 due to thermal stress that easily occurs at high temperatures can be prevented. The durability (thermal cycle characteristics) of the battery can be improved.

JP 2006-222074 A

  By the way, in the fuel cell described in Patent Document 1 described above, the radiator 20 is sandwiched between the separator 8 and the separator 8, and the temperature of the high temperature portion is lowered by the heat radiation action from the surface of the radiator 20. Although the temperature distribution in the stacking direction is made uniform, there is still a case where the maximum temperature of the single cell cannot be lowered sufficiently. In such a case, the heat dissipating area is increased by increasing the thickness of the heat dissipating body 20 or the number of heat dissipating fins. However, if the heat dissipating effect is increased, the structure becomes complicated.

  In addition, even when the radiator 20 is arranged, if the maximum temperature is still high, the supply amount of air to the power generation cell 5 is increased to lower the maximum temperature. If the amount is increased, the temperature of other parts (minimum temperature part, etc.) also decreases at the same rate, causing a problem that power generation efficiency decreases.

  The present invention has been made in view of the above circumstances, and can effectively lower the maximum temperature with a simpler structure than a radiator, thereby further uniforming the temperature distribution in the stacking direction of the fuel cell stack. Therefore, an object of the present invention is to provide a solid oxide fuel cell that can improve power generation efficiency.

  In order to solve the above-mentioned problem, the invention described in claim 1 is to form a power generation cell by disposing a fuel electrode layer and an air electrode layer on both sides of the solid electrolyte layer, and to the fuel electrode current collector outside the power generation cell. A single cell is formed by disposing a body and an air electrode current collector, and a separator is disposed outside these current collectors, and a fuel cell stack is formed by stacking a plurality of the single cells. Forming a reaction gas discharge hole for discharging a reaction gas on each surface facing the fuel electrode layer and the air electrode layer, and through the collector through the internal flow path of the separator. In the solid oxide fuel cell that generates a power generation reaction by supplying a reaction gas to the fuel electrode layer and the air electrode layer, a cooling separator is stacked at any location in the stacking direction of the fuel cell stack, Cooling center A cooling dedicated passage is provided in the circulator for allowing cooling air to circulate and exhausting the circulated air out of the separator from another outlet that is not in communication with the reaction gas discharge hole. To do.

  The invention according to claim 2 is the solid oxide fuel cell according to claim 1, wherein the reaction facing the fuel electrode layer in addition to the cooling dedicated passage is provided inside the cooling separator. A fuel gas supply path communicating with the gas discharge hole and an oxidant gas supply path communicating with the reaction gas discharge hole facing the air electrode layer are formed at least one internal gas supply path. It is.

  Furthermore, the invention described in claim 3 is the solid oxide fuel cell according to claim 1 or 2, wherein a radiator is disposed at a location adjacent to the cooling separator in the stacking direction of the fuel cell stack. The outlet of the cooling dedicated passage is provided so that the air from the cooling dedicated passage is discharged toward the radiator.

  According to the first aspect of the present invention, since the cooling dedicated passage is provided in the cooling separator and air is circulated through the cooling dedicated passage, the separator and the surrounding heat can be actively released. By inserting this separator at the maximum temperature location, the maximum temperature can be reduced, and the temperature distribution in the stacking direction of the fuel cell stack can be made uniform. At that time, the air flowing through this cooling-only passage does not go to the power generation cell, so just because the amount of air supplied to the separator is increased, the temperature other than the high temperature part is lowered unexpectedly. There is no end.

  In general, the amount of air supplied to the power generation cell as the oxidant gas is set to be larger (for example, about 1.4 times) than the amount of air necessary for power generation. The separator can be used for cooling, and the supplied air can be effectively used. Moreover, structurally, only the cooling dedicated passage is provided inside the separator, so that it is not bulky and the stack structure is not particularly complicated.

  In addition, air can be flowed through the cooling separator in an amount necessary for cooling, and the cooling effect can be greatly enhanced by simply increasing the amount of air as necessary. In addition, since the cooling air can be supplied through the same line as that supplied to the power generation cell as the oxidant gas, the temperature distribution in the stacking direction in the stack is made uniform without major structural changes and cost increases. It is possible to increase the power generation efficiency.

  Furthermore, according to the invention described in claim 2, although it is a separator for cooling, it also has a function of discharging a reaction gas to the power generation cell, so that it can be incorporated into the stack in exactly the same manner as a normal separator. it can.

  In addition, according to the invention described in claim 3, the radiator is disposed at a location adjacent to the cooling separator, and the air discharged from the cooling dedicated passage toward the radiator is discharged. In addition to improving the cooling effect by simply adding the radiator, the heat radiation performance of the surface of the radiator can be enhanced by the flowing air. Therefore, a larger cooling effect can be exhibited by the combination of the cooling separator and the radiator, and the structure of the radiator can be avoided.

1 is a side view showing a principle configuration of a solid oxide fuel cell according to a first embodiment of the present invention. It is sectional drawing which shows the structural example of the separator for cooling incorporated in a fuel cell. FIG. 2 is a plan view of a general separator incorporated in the fuel cell. It is a top view which shows the planar structure of the separator which formed only the cooling only channel | path of FIG. It is a side view which shows the principle structure of the solid oxide fuel cell of 2nd Embodiment of this invention. It is a side view which shows the principle structure of the solid oxide fuel cell of 3rd Embodiment of this invention. It is a top view which shows the plane structure of the separator 180 for cooling integrated in the fuel cell of FIG. It is a perspective view which shows the structure of the part incorporating the heat radiator in the fuel cell of embodiment of FIG. It is a perspective view which fractures | ruptures and shows a part of FIG. FIG. 10 is a partially enlarged perspective view of FIG. 9. It is a schematic block diagram of the conventional fuel cell. It is a perspective view which shows the structure of the heat radiator incorporated in the fuel cell. It is a figure which shows the flow of the gas for reaction in the fuel cell which laminated | stacked the same heat radiator.

Hereinafter, embodiments of the present invention will be described with reference to FIGS.
In the solid oxide fuel cell shown in FIG. 1, the fuel cell layer 3 and the air electrode layer 4 are arranged on both sides of the solid electrolyte layer 2 in the same manner as described with reference to FIG. The fuel cell current collector 6 and the air electrode current collector 7 are disposed outside the power generation cell 5, and the separator 8 is disposed outside the current collectors 6 and 7 to form a single cell 10. At the same time, a fuel cell stack 101 is formed by stacking a plurality of the single cells 10, and reaction gas discharge holes for discharging a reaction gas to each surface of the separator 8 facing the fuel electrode layer 3 and the air electrode layer 4. 11a and 12a are formed, and the reaction gas (oxidation) is supplied to the fuel electrode layer 3 and the air electrode layer 4 from the reaction gas discharge holes 11a and 12a through the current collectors 6 and 7 through the internal flow paths 11 and 12 of the separator 8. Power generation reaction by supplying agent gas A and fuel gas B) It is intended to produce.

  This basic configuration is the same as that of FIG. Note that the separators 8A and 8B at the ends in the stacking direction have the reaction gas discharge holes 11a and 11b on only one side, and are therefore given a distinguishing sign for convenience.

  The fuel cell of the present embodiment shown in FIG. 1 is different from that of FIG. 11 in that a cooling separator 80 is laminated at an arbitrary position in the stacking direction of the fuel cell stack instead of interposing a heat radiating body. A cooling-only passage 83 is provided in which the cooling air can be circulated in the separator 80 and the circulated air is discharged outside the separator 80 from another outlet 83a that is not in communication with the reaction gas discharge hole 12a. It is a point provided.

  In this case, the cooling separator 80 has a cooling gas passage 83 facing the air electrode layer 4 and a fuel gas supply path 11 communicating with the reaction gas discharge hole 11 a facing the fuel electrode layer 3 in addition to the cooling dedicated passage 83. It has both the oxidant gas supply path 12 communicating with the hole 12a, and has three independent flow paths inside.

  As shown in FIG. 2, the cooling separator 80 includes a separator 81 having only a cooling passage 83, a separator 8B having only the reaction gas discharge hole 11a and the fuel gas supply passage 11, and a reaction gas discharge. A separator 8A in which only the holes 12a and the oxidant gas supply path 12 are formed may be laminated.

  FIG. 3 is a plan view of a general separator (base separator) 8 incorporated in the fuel cell stack 101. In this separator 8, a fuel gas supply path 11 and an oxidant gas supply path 12 are formed, and the fuel gas A fuel gas passage 11 communicates with the manifold 13 and an oxidant gas passage 12 communicates with the oxidant gas manifold 14.

  FIG. 4 is a plan view showing a planar configuration of the separator 81 in which only the cooling-only passage shown in FIG. 2 is formed. In the separator 81, only the cooling-only passage 83 is formed. The base end of this cooling exclusive passage 83 communicates with the oxidant gas manifold 14, and the distal end opens as an outlet 83 a on the outer peripheral surface of the separator.

  As described above, since the solid oxide fuel cell of the present embodiment has the cooling separator 80 interposed at an arbitrary position of the fuel cell stack 101, by circulating air through the cooling dedicated passage 83, The separator 80 and its surrounding heat can be actively released. Therefore, by inserting the separator 80 at the highest temperature location, the maximum temperature can be reduced, and the temperature distribution in the stacking direction of the fuel cell stack 101 can be made uniform.

  At this time, since the air flowing through the cooling dedicated passage 83 is not directed to the power generation cell 5, just because the amount of air supplied to the separators 8 and 80 is increased, the temperature other than the high temperature portion is predicted as in the past. It wo n’t fall outside. In general, the amount of air supplied to the power generation cell 5 as an oxidant gas is set to be larger (for example, about 1.4 times) than the amount of air necessary for power generation. The separator 80 can be used for cooling, and the supplied air can be effectively used.

  Further, structurally, only the cooling exclusive passage 83 is provided inside the separator 80, so that the structure of the stack 101 is not particularly complicated without being bulky. In addition, air can flow through the cooling separator 80 in an amount necessary for cooling, and the cooling effect can be greatly enhanced by simply increasing the amount of air as necessary. Further, since the cooling air can be supplied through the same line as that supplied to the power generation cell 5 as the oxidant gas, the temperature distribution in the stacking direction in the stack 101 is made uniform without changing the structure or increasing the cost. Power generation efficiency can be improved.

FIG. 5 is a side view showing the principle configuration of the solid oxide fuel cell according to the second embodiment.
In this fuel cell, two cooling separators 80A and 80B are interposed at an arbitrary position in the stacking direction of the fuel cell stack 102, and between the two cooling separators 80A and 80B, electric A conductive member 170 that secures a flow path is interposed. The upper cooling separator 80B has the cooling dedicated passage 83 and the fuel gas passage 11, and the lower cooling separator 80A has the cooling dedicated passage 83 and the oxidant gas passage 12.

  In this case, since the two cooling separators 80A and 80B are interposed in the middle of the fuel cell stack 102, the cooling effect can be enhanced more than in the first embodiment. Moreover, since one side of the cooling separators 80A and 80B is opened by interposing the conductive member 170, the heat dissipation effect can be enhanced. The conductive separators 170 may be omitted so that the cooling separators 80A and 80B are in close contact with each other, and one of the two cooling separators 80A and 80B is a normal single-sided type that does not have a cooling dedicated passage. The separators 8A and 8B can be replaced.

FIG. 6 is a side view showing the principle configuration of the solid oxide fuel cell of the third embodiment.
In this fuel cell, a single cooling separator 180 is interposed at an arbitrary position in the stacking direction of the fuel cell stack 103, and a heat dissipating body 120 is disposed adjacent to the cooling separator 180. The position of the outlet 83 of the cooling dedicated passage 83 is set so that the air from the cooling dedicated passage 83 in the cooling separator 180 is discharged. In this case, as shown in FIG. 7, the cooling separator 180 is provided with the fuel gas passage 11 in addition to the cooling exclusive passage 83.

  8-10 is a figure which shows the specific structure of the location which provided the heat radiator 120, and the heat radiator 120 is pinched | interposed into the upper separator 180 for cooling and the lower separator 8A. The configuration of the auxiliary heat body 120 is substantially the same as that shown in FIG. 12, and is entirely composed of a metal having excellent thermal conductivity. The cylindrical support portion 122 and the outer peripheral side of the support portion 122 A plurality of radiating fins 123 arranged radially and flange portions 121 and 121 provided at both upper and lower ends of the support portion 122 are provided, and the support portion 122 is positioned substantially at the center in the surface direction of the fuel cell stack 103. It is arranged.

  The flange portion 121 is arranged in an intimately integrated state between the separator 180 and the separator 8A, so that good electrical contact with the adjacent separators 180 and 8A can be obtained. The support portion 122 mainly serves as a cell current path and supports a load in the stacking direction applied to the upper flange portion 121. By disposing the support portion 122 at the substantially central portion in the stack surface direction, the stack current concentrated in the central portion of the power generation cell 5 and flowing in the stacking direction can be efficiently relayed to the next power generation cell 5. The support part 122 consists of a hollow cylindrical body, and has many holes 122a in the peripheral wall.

  Further, the upper end of the support portion 122 is opened on the upper surface of the flange portion 121, and the outlet 83a of the cooling dedicated passage 83 of the upper cooling separator 180 communicates with the opening. Therefore, the air that has exited from the outlet 83a of the cooling separator 180 flows radially from the hole 122a in the cylindrical peripheral wall of the support portion 122 through the space between the upper and lower flange portions 121, while the flange portion 121 and By contacting the surfaces of the support part 122 and the heat radiation fins 123, the heat radiation performance of the heat radiator 120 is significantly improved.

  Therefore, a greater cooling effect can be exhibited by the combination of the cooling separator 180 and the radiator 120, and the structure of the radiator 120 can be prevented from becoming complicated.

2 solid electrolyte layer 3 fuel electrode layer 4 air electrode layer 5 power generation cell 6 fuel electrode current collector 7 air electrode current collector 8, 8A, 8B separator 11 fuel gas passage 11a reactive gas discharge hole 12 oxidant gas passage 12a reactive gas Discharge hole 80, 80A, 80B, 180 Cooling separator 83 Cooling exclusive passage 83a Outlet 101, 102, 103 Fuel cell stack 120 Radiator

Claims (3)

A power generation cell is configured by disposing a fuel electrode layer and an air electrode layer on both sides of the solid electrolyte layer, and a fuel electrode current collector and an air electrode current collector are disposed outside the power generation cell. A single cell is formed by arranging a separator on the outside, and a fuel cell stack is formed by stacking a plurality of the single cells, and a reaction gas is provided on each surface of the separator facing the fuel electrode layer and the air electrode layer. Forming a reaction gas discharge hole for discharging gas and supplying the reaction gas from the reaction gas discharge hole to the fuel electrode layer and the air electrode layer through the current collector through the internal flow path of the separator. In a solid oxide fuel cell that generates a power generation reaction,
Cooling separators can be stacked at any location in the stacking direction of the fuel cell stack, cooling air can be circulated inside the cooling separator, and the circulated air can be connected to the reaction gas discharge holes. Is a solid oxide fuel cell characterized in that a cooling-only passage is provided to discharge outside the separator from another non-communication outlet.   In addition to the cooling dedicated passage, a fuel gas supply path communicating with the reaction gas discharge hole facing the fuel electrode layer, and the reaction gas discharge hole facing the air electrode layer, in the cooling separator. 2. The solid oxide fuel cell according to claim 1, wherein at least one internal gas supply path of the oxidant gas supply path communicating with the first and second oxidant gas supply paths is formed.   A radiator is provided at a location adjacent to the cooling separator in the stacking direction of the fuel cell stack, and an outlet of the cooling dedicated passage is discharged so that air from the cooling dedicated passage is discharged toward the radiator. The solid oxide fuel cell according to claim 1, wherein the solid oxide fuel cell is provided.

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