JP2009193808A - Solid oxide fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid oxide fuel cell module which recovers a thermal energy effectively without damaging a piping or a preheating unit or the like. <P>SOLUTION: The solid oxide fuel cell includes a fuel cell module having a group of fuel battery unit cells in which an anode to which fuel gas is supplied and a cathode to which oxidizer gas is supplied are formed with a solid oxide electrolyte layer in-between and a single layer or a plurality of layers of a heat insulation material surrounding an outer portion of the group, one or a plurality of heat insulating outer walls forming preheating passages which are arranged outside of the fuel cell module and in which the fuel gas or the oxidizer gas flow, and a porous body arranged between the insulating out walls and the fuel cell module. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a solid oxide fuel cell that can effectively reduce thermal energy loss due to heat dissipation.

  In general, a solid oxide fuel cell (SOFC) uses an oxide ion conductor, for example, stabilized zirconia, as an electrolyte, and an anode and a cathode are arranged on both sides of the electrolyte. In addition, depending on the cell shape, an interconnector that serves as an electrical connection with the anode or the cathode during stacking is provided. This fuel cell is normally used as a fuel cell stack in which a predetermined number of single cells and separators are stacked.

  Conventionally, the power generation temperature of SOFC is very high at about 1000 ° C., and in order to maintain the high temperature, a heat insulating structure filled with a heat insulating material has been taken. The battery module body has become a large scale. Further, the internal temperature of the fuel cell is preferably made uniform, and it is preferable to prevent the temperature distribution from occurring inside depending on the operating conditions.

  In such a heat insulating structure, as a means for insulating the reaction heat generated in the fuel cell or the like, as described in Patent Document 1, for example, a fuel gas or an oxidant gas that supplies the heat generated by the cell exothermic reaction to the fuel cell Means for heat exchange and recovery have been proposed.

  If it is only heat insulation and cooling, it can be easily solved by covering the outside of the module with a heat insulating material and further incorporating a cooling device. However, in the case of home use, downsizing is desired.

JP 09-07624 A Japanese Patent Laid-Open No. 08-273686

  Therefore, in order to make the fuel cell module compact, it is necessary to arrange fuel gas or oxidant gas piping or a preheating container adjacent to the power generation module. However, if the operation is continued at a high temperature of about 1000 ° C., there is a problem that the pipe or the preheating container may be damaged due to a difference in thermal expansion of the high-temperature pipe.

  An object of the present invention is to provide a solid oxide fuel cell module that can effectively recover thermal energy without damaging piping or preheating equipment.

  The present invention includes an assembly of fuel cell single cells in which an anode to which a fuel gas is supplied and a cathode to which an oxidant gas is supplied are formed via a solid oxide electrolyte layer, and surrounds the outside of the assembly. A fuel cell module provided with a heat insulating means using a single layer or a plurality of layers of heat insulating material, and one or a plurality of preheating passages arranged outside the fuel cell module through which the fuel gas or oxidant gas flows. The present invention provides a solid oxide fuel cell comprising a heat insulating outer wall to be formed and a porous body disposed between the heat insulating outer wall and the fuel cell module.

  According to the present invention, it is possible to provide a solid oxide fuel cell capable of effectively recovering thermal energy from a fuel cell module without damaging a pipe or a preheating device.

  The heat insulation outer wall is a heat insulation outer wall (21 ′ and 21 ″ in FIG. 1) arranged between and around the high temperature heat insulator disposed on the outer periphery of the fuel cell module and the preheat passage. Those consisting of are preferred.

  An object of the present invention is a fuel cell single cell assembly having an anode to which fuel gas is supplied and a cathode to which an oxidant gas is supplied, and outside the fuel cell module in which the outside of the assembly is surrounded by a heat insulating material. A preheating passage through which the fuel gas or oxidant gas flows is arranged. Specifically, a porous body is disposed between the inlet and the outlet of the fuel gas or oxidant gas supplied to the passage to recover heat transfer and radiant heat from the fuel cell module more efficiently. It is characterized by.

  As another preferred embodiment of the present invention, there is a solid oxide fuel cell module in which the porosity of the porous body arranged in the preheating passage varies depending on the position of the fuel cell module. As another embodiment, the preheating passage and the fuel cell are provided with a temperature measuring means and a reaction gas flow rate adjusting means, and the fuel gas or oxidation supplied to the preheating passage according to the temperature distribution of the fuel cell. There is a solid oxide fuel cell module that controls the flow rate of the agent gas.

  As another preferred embodiment, a solid oxide fuel cell module in which a thermal insulation terminal is connected to a measurement port for taking out the temperature measurement means provided in the fuel cell and the preheating passage from the fuel cell module to the outside. There is. Further, when the fluid flowing through the preheating passage is fuel gas, there is a solid oxide fuel cell module in which the porous body disposed inside the passage is a reduction-resistant material.

  Further, as a preferred embodiment, when the fluid flowing through the preheating passage is an oxidant gas, there is a solid oxide fuel cell module in which the porous body disposed inside the passage is an oxidation resistant material.

  According to another preferred embodiment of the present invention, a passage through which a fuel gas or an oxidant gas supplied to the fuel cell flows is disposed close to the fuel cell module surrounded by the heat insulating means, and a single fuel cell The heat generated by generating electricity can be recovered before dissipating heat to the outside of the fuel cell module.

  In addition, by disposing a porous plate in the preheating passage, the thermal conductivity in the preheating passage can be improved and the fuel gas or oxidant gas flowing in the preheating passage can be made to flow uniformly in the surface of the preheating passage. Therefore, the temperature distribution of the fuel cell can be made uniform, and the heat radiation can be efficiently recovered.

  When a plurality of the preheating passages are provided, it is preferable to adjust the flow rate of the fuel gas or the oxidant gas flowing through each passage according to the temperature measured by the temperature measuring means of the fuel cell. Thereby, since the temperature distribution of the fuel cell can be made uniform, the heat radiation can be recovered more efficiently.

  Further, the porous material inserted into the passage is preferably a metal material having good heat conduction, and if the fluid flowing in the passage is the fuel gas, it is a reducing atmosphere, so a metal material of a reduction resistant material such as nickel is used, If the fluid flowing through the passage is an oxidant gas, the heat radiation can be effectively recovered by using an oxidation-resistant metal material such as stainless steel.

  In the present invention, the fuel cell module means a configuration including an anode, an assembly of fuel cell single cells including a cathode disposed via a solid oxide layer, and a heat insulating material (heat insulating inner wall 20) surrounding the outer periphery thereof. .

  A heat insulating outer wall that forms one or more preheating passages through which fuel gas or oxidant gas flows is disposed outside the fuel cell module. And the porous body 9 is arrange | positioned in the preheating channel | path 41 formed in this heat insulation outer wall 21, and the thermal energy from the said heat insulation inner wall (high temperature heat insulating material) 20 is collect | recovered with a porous body. The heat insulating outer wall 21 includes an outer heat insulating outer wall 21 ′ and an inner heat insulating wall 21 ″.

Hereinafter, specific embodiments of the present invention will be specifically described.
(First embodiment)
FIG. 1 is a schematic sectional view of a fuel cell module according to a first embodiment of the present invention. As shown in FIG. 1, the present invention has a fuel cell 1. The fuel cell 1 is a solid oxide fuel cell. The fuel cell 1 is an assembly of fuel cell single cells, and a fuel cell module is configured by the assembly of fuel cell single cells, the collector electrode 3, and the high-temperature heat insulating material 20 disposed on the outer periphery thereof.

  FIG. 2 is a partial cross-sectional perspective view showing the structure of a cylindrical fuel cell single cell that can be employed in the present invention. The present invention is applied to, for example, a cylindrical type as shown in FIG. The cylindrical solid oxide fuel cell single cell shown in FIG. 2 includes an electrolyte electrode assembly in which a cathode 51, an anode 54, and an interconnector 52 are provided on both surfaces of an electrolyte 53.

  The electrolyte 53 is made of an oxide ion conductor such as stabilized zirconia. The interconnector 52 plays a role of electrical connection with the anode or the cathode when stacked. FIG. 1 also shows a fuel cell module in which a plurality of single cells shown in FIG. 2 are arranged and its heat recovery system.

  The combustion chamber 10 burns unreacted fuel discharged from the anode and cathode of the fuel cell 1 and increases the amount of heat of the combustion exhaust gas. Combustion exhaust gas is a very high temperature of 600 ° C. to 1000 ° C., and this high temperature combustion exhaust gas is used as a heat source for air and fuel preheating, fuel reforming, steam generation, and hot water.

  The air introduction pipe 2 is provided on the cathode side of the fuel cell 1 in order to supply an oxidant gas from an oxidant gas supply source (not shown) such as a blower or a compressor. It is used to send air, which is an oxidant gas, to the tip of the gas.

  The collecting electrode 3 is provided to collect the electromotive force generated by the power generation by the fuel cell 1 and take it out.

  A soaking plate 13 is provided for the purpose of reducing the temperature difference between the single fuel cells 1. The soaking plate 13 is not particularly limited as a material, but a material having good heat conduction is preferable. For example, copper that can be used even in a reducing atmosphere is preferable.

In order to uniformly supply the fuel gas to the anode of the fuel cell 1, the anode chamber 11 disperses the fuel gas to every corner of the anode chamber 11 with the anode chamber partition plate 7, and the fuel cell 1 with the porous rectifying plate 6. The fuel gas is uniformly supplied to the anode. A fuel gas supply means 32 is connected to the anode chamber 11. As the fuel gas supply means 32, for example, a reformer (not shown) capable of steam reforming to a raw fuel gas mainly containing methane (CH ₄ ) such as city gas is used as a suitable means.

  In order for the cathode chamber 12 to uniformly supply the oxidant gas to the cathode of the fuel cell 1, the oxidant gas is dispersed throughout the cathode chamber 12 by the cathode chamber partition plate 8, and the oxidant is uniformly distributed in the air introduction pipe 2. By supplying the gas, the oxidant gas can be uniformly supplied also to the cathode of the fuel cell 1.

  FIG. 3 is a schematic diagram of a heat insulating structure of a fuel cell 1 power generation portion that can be employed in the present invention. From FIG. 3, the heat radiation from the single fuel cell 4 can be reduced to about 400 ° C. by the high-temperature heat insulating material (heat insulating inner wall) 20 and the low-temperature high-functional heat insulating material (heat insulating outer wall) 21. Here, the heat insulating material 20 for high temperature is preferably a material having a low thermal expansion coefficient at a heat resistance of about 700 ° C to 1000 ° C. For example, fine flex (registered trademark, trade name of Nichias Co., Ltd.) composed of silica-alumina heat-resistant fibers can be cited as a suitable material, but is not limited thereto. Moreover, as a low-temperature high-performance heat insulating material, low thermal expansion is preferable at about 400 ° C. to 600 ° C., for example, “PORTHETHERM WDS” developed by Wacker Chemie GmbH in Germany can be cited as a suitable material. However, the present invention is not limited to this.

  The oxidant gas is preheated by the air preheating passage 41 by heat radiation from the inner wall 21 ″ of the low temperature heat insulating material 21. A porous body 9 is inserted into the air preheating passage 41 in order to efficiently recover thermal energy from heat dissipation. Here, the material of the porous body 9 is not limited, but a metal material having good thermal conductivity is preferable in order to recover heat radiation more efficiently. However, a sufficiently high heat-resistant material is selected so as not to be burned or destroyed by the preheated gas and the heat energy from the heat insulating inner wall 21 ″. The pores of the porous body are preferably through-holes, and the direction of the through-holes is preferably perpendicular or transverse to the direction of the preheating passage.

  Here, it is desirable to use a porous material having a different pore diameter or porosity with respect to the axial direction of the fuel cell module. For example, a porous material having a large pore diameter or porosity is inserted into a portion where the temperature is assumed to be higher than the average temperature in the axial direction of the single fuel cell. Thereby, since the flow volume of the fuel gas or oxidant gas which flows through the part can be increased, the temperature of the high temperature part of the fuel cell can be lowered more effectively.

  In addition, by inserting a porous material having a small pore diameter or porosity into a portion where the temperature is assumed to be lower than the average temperature in the axial direction of the fuel cell module, the fuel gas flowing through that portion or The flow rate of the oxidant gas can be reduced. Overcooling at that portion can be prevented.

  As described above, when a large flow rate of fuel gas or oxidant gas is required, a porous body having a large pore size or porosity is used. When a small flow rate is required, a porous body having a high pore size or a low porosity is used. Let it be the body.

The solid oxide fuel cell according to the present embodiment has the following effects.
(1) The heat radiation from the fuel cell module to the outside can be used as preheating of the fuel gas and the oxidant gas, and the porous body can be inserted into the preheating passage for more efficient preheating. If the preheating passage is simply provided, the thermal energy released from the fuel cell module is released to the outside of the fuel cell without being sufficiently recovered. However, by arranging a porous body in the preheating passage, the thermal energy is Can be recovered extremely efficiently.
(2) The porous body preferably has continuous pores. By inserting this porous body, the fuel gas or the oxidant gas can flow uniformly in the preheating passage, so that the temperature of the fuel cell module is made uniform. can do.
(3) By changing the porosity of the porous body to be inserted with respect to the axial direction of the fuel cell module, the temperature can be made uniform with respect to the axial direction of the fuel cell module.
(4) Since the heat radiation from the module is recovered by the preheating passage, the heat insulating material can be thinned, so that the heat radiation loss of the fuel cell module can be reduced and the fuel cell module can be made compact.
(Second Embodiment)
FIG. 4A is a schematic perspective view of a solid oxide fuel cell according to the second embodiment of the present invention, and FIG. 4B is a graph showing a temperature gradient in the axial direction of the fuel cell module. In the first embodiment, there is one air preheating passage, but in this embodiment, this passage is divided into a plurality of portions in the axial direction.

  As shown in FIG. 4a), a plurality of air preheating passages (three in this embodiment) are provided in the axial direction of the fuel cell module body according to the present embodiment, and the oxidant gas inlets of the respective passages are independent. ing. As shown in FIG. 4B, near the surface of the fuel cell 1, there are provided means for measuring temperatures (T 1, T 2, and T 3) at respective axial heights.

  By dividing a plurality of air preheating passages, even if there is a difference in temperature distribution in the axial direction of the fuel cell 1, the flow rate of air supplied to each air preheating passage according to the measured temperature is controlled by a control means (not shown). Since it can be controlled, the heat distribution in the axial direction of the fuel cell 1 can be made uniform.

  That is, as shown in FIG. 4B, when the temperature distribution of the fuel cell 1 is high in the central portion (T2) with respect to the axial direction (solid line in the drawing), By selectively lowering the temperature of T2 by increasing the flow rate, the temperature distribution can be made uniform with respect to the axial direction of the fuel cell 1. Further, since the porous plate is used in the circumferential direction with respect to the axial direction of the fuel cell, the gas flow rate becomes uniform as a whole, so that the temperature of the fuel cell can be controlled uniformly.

According to the solid oxide fuel cell according to the present embodiment, the temperature distribution in the axial direction of the fuel cell 1 is made uniform by dividing the air preheating passage into a plurality of parts, so that the deterioration of the fuel cell due to the temperature rise Etc. can be prevented.
(3 embodiment)
FIG. 5 is a schematic view of a solid oxide fuel cell according to a second embodiment of the present invention. As shown in FIG. 5, in the third embodiment, a fuel preheating passage 421 is provided in addition to a passage for preheating air. The fuel preheating passage 421 is supplied with a gas obtained by mixing raw fuel gas and steam before reforming or reformed fuel gas.

  As described above, according to the present embodiment, not only air but also heat radiation from the fuel cell 1 can be used for preheating and reforming of the fuel gas, so that no external reformer, fuel preheater, etc. are required. A more compact fuel cell system can be provided.

  The present invention is not limited to the embodiment of the invention described above, and any structure may be used as long as it provides a heat exchange function outside the fuel cell module and removes excess heat from the fuel cell module. Therefore, the present invention is not limited to the configuration as illustrated, and various modifications can be made without departing from the scope of the present invention.

1 is a configuration diagram of a solid oxide fuel cell according to a first embodiment of the present invention. 1 is a partial cross-sectional perspective view of a cylindrical fuel cell that can be employed in the present invention. 1 is a cross-sectional view of the outside of a solid oxide fuel cell module according to a first embodiment of the present invention. It is a schematic block diagram of the solid oxide fuel cell which concerns on 2nd Embodiment of this invention. It is a schematic block diagram of the solid oxide fuel cell which concerns on 3rd Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Fuel cell, 2 ... Air introduction pipe, 3 ... Collector electrode, 4 ... Fuel cell single cell, 6 ... Current plate, 7 ... Anode chamber partition plate, 8 ... Cathode chamber partition plate, 9 ... Porous body, 10 ... Combustion chamber, 11 ... anode chamber, 12 ... cathode chamber, 20 ... high temperature insulation, 21 ... high performance insulation for low temperature, 31 ... oxidant gas supply means, 32 ... fuel gas supply means, 41 ... air preheating passage, DESCRIPTION OF SYMBOLS 51 ... Cathode, 52 ... Interconnector, 53 ... Solid oxide electrolyte, 54 ... Anode, 311, 312, 313 ... Oxidant gas supply means, 321 ... Fuel gas supply means, 411 ... Air preheating passages 1, 412 ... Air Preheating passage 2, 413 ... Air preheating passage 3, 414 ... Air preheating passage, 421 ... Fuel preheating passage

Claims (9)

  An assembly of fuel cell single cells in which an anode to which fuel gas is supplied and a cathode to which oxidant gas is supplied are formed via a solid oxide electrolyte layer, and a single layer surrounding the outside of the assembly, or A fuel cell module having a plurality of layers of high-temperature heat insulating material; a heat insulating outer wall that forms one or more preheating passages through which the fuel gas or oxidant gas flows disposed outside the fuel cell module; and the heat insulating outer wall A solid oxide fuel cell comprising a porous body disposed between the fuel cell module and the fuel cell module.   2. The solid oxide fuel cell according to claim 1, wherein the porosity of the porous body disposed in the preheating passage varies depending on the position of the fuel cell module.   Temperature measuring means and reactive gas flow rate adjusting means are provided in the preheating passage and the fuel cell module, and the flow rate of the fuel gas or oxidant gas supplied to the preheating passage is controlled according to the temperature distribution of the fuel cell module. The solid oxide fuel cell according to claim 1 or 2.   The thermal insulation terminal is connected to a measurement port for taking out the temperature measurement means provided in the fuel cell module and the preheating passage from the fuel cell module to the outside. A solid oxide fuel cell module according to claim 1.   The solid oxide form according to any one of claims 1 to 4, wherein when the fluid flowing through the preheating passage is fuel gas, the porous body disposed inside the passage is a reduction resistant material. Fuel cell module.   The solid oxide according to any one of claims 1 to 5, wherein when the fluid flowing through the preheating passage is an oxidant gas, the porous body disposed inside the passage is an oxidation resistant material. Fuel cell module.   An assembly of fuel cell single cells in which an anode to which a fuel gas is supplied and a cathode to which an oxidant gas is supplied are formed via a solid oxide electrolyte layer, and a high-temperature heat insulating material surrounding the outside of the assembly A fuel cell module comprising: a heat insulating outer wall that forms a preheating passage through which the fuel gas or oxidant gas flows disposed outside the fuel cell module; and the heat insulating outer wall and the fuel cell module. A solid oxide fuel cell, wherein the porosity of the porous body is higher at a higher temperature in the axial direction of the fuel cell module.   A temperature measuring means and a reaction gas flow rate adjusting means provided in the preheating passage and the fuel cell module, and the fuel gas or oxidant gas supplied to the preheating passage according to the temperature distribution in the axial direction of the fuel cell module; 8. The solid oxide fuel cell according to claim 7, wherein the flow rate is controlled.   8. The solid oxidation according to claim 7, wherein a thermal insulation terminal is connected to a measurement port for taking out the temperature measurement means provided in the fuel cell module and the preheating passage from the fuel cell module to the outside. Physical fuel cell module.

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