JP2005100821A - High temperature type fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a suitable means in order to effectively utilize reaction heat by preventing that reaction heat generated accompanied by a power generation reaction inside a high temperature type fuel cell stack of a high temperature type fuel cell system is dissipated as a heat discharge loss through a heat-insulating and temperature reserving layer formed so as to surround the high temperature type fuel cell stack. <P>SOLUTION: In the high temperature type fuel cell system which is provided with an electrolyte, oxidizer gas supply lines for supplying the oxidizer gases to a fuel electrode, an air electrode, and the fuel cell stack at both sides of the electrolyte, a fuel gas supply line for supplying the fuel gas to the fuel cell stack, and the heat-insulating and temperature reserving layer at surroundings of the fuel cell stack, a heat utilizing measure is provided between the fuel cell stack and the heat-insulating and temperature-reserving layer or inside the heat-insulating and temperature-reserving layer. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a high-temperature fuel cell system, and in particular, in a high-temperature fuel cell system having a high operating temperature such as a solid oxide fuel cell or a molten carbonate fuel cell, the power generation reaction is performed inside the fuel cell stack. It is an invention that provides a suitable means for effectively utilizing the reaction heat (hereinafter also referred to as power generation reaction heat) that is generated.

  A typical example of a conventional high-temperature fuel cell system is shown in FIG. The conventional high-temperature fuel cell system incorporates a fuel reformer 110 in the fuel cell stack 1 in order to use reaction heat generated in the fuel cell stack 1 due to a power generation reaction (for example, (See Patent Document 1 and Patent Document 2.) In the high-temperature fuel cell system, since the operating temperature of the fuel cell stack 1 is higher than the environmental temperature in which the fuel cell system is installed, the heat insulating heat insulating layer 4 for maintaining the operating temperature and heat insulating is provided in the fuel cell stack. 1 is disposed around. In this case, a part of the reaction heat is used for the built-in fuel reformer 110, but most of the reaction heat is dissipated outside the system through the heat insulating and heat insulating layer 4 disposed in the surroundings. Due to this heat dissipation, there is a problem that the effective use of reaction heat generated in the fuel cell stack 1 of the high-temperature fuel cell system due to the power generation reaction is impaired, and the overall energy utilization efficiency is lowered.

In addition, other conventional high-temperature fuel cell systems incorporate a heat exchanger in the fuel cell stack 1 for utilizing reaction heat generated in the fuel cell stack 1 due to a power generation reaction (for example, a patent) Reference 3). However, also in this case, much reaction heat is dissipated outside the system through the heat insulation layer 4 on the peripheral surface of the fuel cell stack 1 in which the heat exchanger is not incorporated, and the fuel cell stack 1 of the high temperature fuel cell system. There is a problem that the effective use of the reaction heat generated with the power generation reaction in the interior is impaired.
JP-T-2001-507501 (Page 7, FIGS. 1 and 2) JP-A-3-216966 (page 32, FIG. 1) JP-T-8-504049 (page 15, Fig. 2)

The present invention has been made in order to solve the above-described problems, and an object of the present invention is to generate a high-temperature reaction heat generated in the fuel cell stack of a high-temperature fuel cell system due to a power generation reaction. An object of the present invention is to provide a suitable means for effectively utilizing reaction heat by preventing damage from heat dissipation through a heat insulating and heat insulating layer disposed around the fuel cell stack.

In order to achieve the above object, according to the first aspect of the present invention, an electrolyte, a fuel cell stack formed by connecting a plurality of fuel cells each having a fuel electrode and an air electrode on both sides of the electrolyte, and the fuel An oxidant gas supply line for supplying an oxidant gas to the battery stack; a fuel gas supply line for supplying a fuel gas to the fuel cell stack; and a heat insulating heat insulating layer disposed around the fuel cell stack. In the high-temperature fuel cell system, heat utilization means is provided between the fuel cell stack and the heat insulation heat insulation layer or in the heat insulation heat insulation layer. Preventing reaction heat generated by the power generation reaction inside the fuel cell stack of the high-temperature fuel cell system from being damaged as a heat dissipation through the heat insulating thermal insulation layer disposed around the high-temperature fuel cell system, The reaction heat can be used effectively.

  According to the second aspect of the present invention, the reaction heat that has been radiated through the heat insulating heat insulation layer by the fuel reformer is installed between the fuel cell stack and the heat insulating heat insulating layer or in the heat insulating heat insulating layer. It was made possible to use it effectively for the endothermic reaction of reforming.

  The fuel reformer referred to here converts raw fuel gas such as natural gas or hydrocarbon gas into hydrogen rich gas, and generally has a reforming catalyst built therein, and connects the raw fuel inlet and the hydrogen rich gas outlet. It is comprised with the metal container which has. As a constituent material of the fuel reformer, a heat resistant metal such as a heat resistant alloy steel or a heat resistant stainless steel is suitable. As the reforming catalyst, in addition to a granular catalyst such as a pellet or sphere, a corrugated or honeycomb metal plate surface coated with an appropriate metal such as nickel or ruthenium can also be configured inside the fuel reformer.

  According to the invention of claim 3, the fuel reformer is installed between the fuel cell stack and the heat insulation heat insulation layer or in the heat insulation heat insulation layer, and the fuel reformer is provided in the middle of the fuel gas supply line. As a result, the reaction heat that has been radiated through the heat insulation and heat insulation layer can be effectively used for the endothermic reaction in the fuel reforming of the raw fuel gas supplied to the high temperature fuel cell system. The fuel gas supplied to the high-temperature fuel cell system is preferably hydrogen gas, but natural gas or hydrocarbon gas is generally used as the raw fuel gas from the viewpoint of availability. In this case, before introduction into the fuel cell stack, it is necessary to reform the fuel and convert it into hydrogen-rich gas. Since the fuel reforming reaction is an endothermic reaction, it is possible to effectively utilize the reaction heat that has been radiated through the heat insulating and heat insulating layer as a heat source.

  According to the fourth aspect of the present invention, the reaction heat that has been radiated through the heat insulating heat insulating layer is heated by the gas heating by installing the gas heater between the fuel cell stack and the heat insulating heat insulating layer or in the heat insulating heat insulating layer. It was possible to use it effectively.

  The gas heater here is a closed container having an inlet and an outlet. Installed between or in the fuel cell stack and the heat insulation layer, introduces a low temperature gas from the inlet, raises the temperature of the gas using reaction heat, and discharges the high temperature gas from the outlet Is. The container itself may not be provided with heating means. Heat transfer promoting means such as fins may be provided inside the container. The constituent material of the gas heater is generally a metal material, but an appropriate material can be selected according to use conditions such as use temperature. In the present invention, a high-temperature gas can be obtained by utilizing the reaction heat generated with the power generation reaction as the heating means of the gas heater.

  According to the invention of claim 5, by installing a gas heater between the fuel cell stack and the heat insulation heat insulation layer or in the heat insulation heat insulation layer, and further providing the gas heater in the middle of the fuel gas supply line, The reaction heat that has been radiated through the heat insulation layer can be effectively used for preheating the fuel supplied to the high temperature fuel cell system. Since the operating temperature of the high-temperature fuel cell system is high, it is preferable to preheat the supplied fuel gas and bring it close to the operating temperature. It can be used effectively.

  According to the invention of claim 6, the gas heater is installed between the fuel cell stack and the heat insulating heat insulating layer or in the heat insulating heat insulating layer, and the gas heater is provided in the middle of the oxidant gas supply line. The reaction heat, which has been radiated through the heat insulating layer, can be effectively used for preheating the oxidant gas supplied to the high temperature fuel cell system. Since the operating temperature of the high-temperature fuel cell system is high, it is preferable to preheat the supplied oxidant gas and keep it close to the operating temperature, and the reaction that has been dissipated through the conventional heat insulation layer as a heat source for preheating the oxidant gas. Heat can be used effectively.

  According to the seventh aspect of the present invention, a liquid heater is installed between the fuel cell stack and the heat insulating heat insulating layer, or in the heat insulating heat insulating layer, so that the reaction heat that has been radiated through the heat insulating heat insulating layer is heated by the liquid. It was possible to use it effectively. For example, by supplying water to a liquid heater and heating it, it is possible to recover and effectively use the reaction heat that has been radiated through the heat insulating and heat insulating layer as warm water.

  The liquid heater here is a sealed container having an inlet and an outlet. By installing between the fuel cell stack and the heat insulating heat insulating layer or in the heat insulating heat insulating layer, a low temperature liquid is introduced from the inlet, the temperature of the liquid is raised by reaction heat, and the high temperature liquid is discharged from the outlet. The container itself may not be provided with heating means. Heat transfer promoting means such as fins may be provided inside the container. The constituent material of the liquid heater is generally a metal material, but an appropriate material can be selected according to use conditions such as use temperature.

  According to the eighth aspect of the present invention, the reaction heat that has been radiated through the heat insulating heat insulating layer is heated by heating the liquid generator between the fuel cell stack and the heat insulating heat insulating layer or in the heat insulating heat insulating layer. It can be used effectively for evaporation. For example, by supplying water to the liquid heater and evaporating it by heating, it is possible to recover and effectively use the reaction heat that has been radiated through the heat insulating and heat insulating layer as steam. Further, when the fuel reformer uses a steam reforming reaction, the steam can be used as steam necessary for the reforming reaction by introducing the steam into the fuel reformer.

  A steam generator is a sealed container having an inlet and an outlet, which introduces a low-temperature liquid from the inlet, raises the temperature of the liquid using reaction heat, evaporates, and discharges a high-temperature gas from the outlet. . Heat transfer promoting means such as fins may be provided inside the container. Since the pressure inside the container increases due to the increase in volume accompanying the evaporation of the liquid, it is preferable to make the container a pressure resistant structure or install a safety device such as a safety valve. The constituent material of the liquid heater is generally a metal material, but an appropriate material can be selected according to use conditions such as use temperature and use pressure.

  According to the invention of claim 9, by installing a heat accumulator between the fuel cell stack and the heat insulation heat insulation layer or in the heat insulation heat insulation layer, the heat of reaction that has been radiated through the heat insulation heat insulation layer is stored and effective. It was possible to use it.

  The heat accumulator refers to a heat accumulator having a function of storing heat storage material and storing heat and taking it out when necessary. There are two types of heat accumulators: a sensible heat storage system that stores heat using a temperature change of a substance, and a latent heat storage system that stores heat using a phase change of a material. Solid sensible heat storage materials used in the sensible heat storage system include bricks, concrete, pebbles, metal blocks, and liquid sensible heat storage materials include water and heat transfer oil. Latent heat storage materials used in the latent heat storage system include hydrated salts such as sodium chloride and calcium chloride, paraffin wax, fatty acids, ice, polyethylene, etc., and their transition heat (solid-solid), heat of fusion (solid- Liquid) and heat of evaporation (liquid-gas). An appropriate heat storage material can be selected according to the temperature condition of the installation location of the heat storage device.

  According to the invention of claim 10, heat insulation means comprising a jacket container surrounded by the fuel cell stack is installed between the fuel cell stack and the heat insulation heat insulation layer or in the heat insulation heat insulation layer. It was possible to effectively use most of the heat of reaction that radiated heat through the thermal insulation layer. The jacket container is a sealed container installed around the fuel cell stack so as to cover the fuel cell stack, and heat utilization means can be easily installed on the most surface of the heat insulating and heat insulating layer.

  According to the invention of claim 11, the heat utilization means comprising the coiled container surrounded by the fuel cell stack is installed between the fuel cell stack and the heat insulation heat insulation layer or in the heat insulation heat insulation layer. It was made possible to effectively use most of the reaction heat radiated through the heat insulation layer. The coiled container is a tubular material such as a general piping material that is installed around the fuel cell stack in a coil shape, and heat utilization means are easily installed on the most part of the heat insulation layer. It becomes possible.

  According to the twelfth aspect of the present invention, the thermoelectric conversion element is installed between the fuel cell stack and the heat insulating heat insulating layer or in the heat insulating heat insulating layer, thereby converting the heat of reaction conventionally radiated through the heat insulating heat insulating layer into electric power. It was possible to use it effectively. A thermoelectric conversion element is an element that converts heat (temperature difference) into electric power based on the Seebeck effect, so it is recovered as electric power by installing it between the high-temperature fuel cell stack and the outside of the low-temperature heat insulation layer. It can be used effectively.

According to the invention of claim 13, by installing the heat utilization means according to claims 1 to 12 between the fuel cell stack and the heat insulation heat insulation layer or in the heat insulation heat insulation layer, the conventional heat insulation heat insulation layer is passed through. It was possible to effectively use almost all of the reaction heat that was dissipating heat.

According to the present invention, the reaction heat generated by the power generation reaction inside the fuel cell stack of the high temperature fuel cell system is lost as a heat dissipation loss through the heat insulating heat insulating layer disposed around the high temperature fuel cell stack. This can be largely prevented, and the reaction heat generated with the power generation reaction can be used effectively. Therefore, the overall energy utilization efficiency of the high-temperature fuel cell system can be increased.

Hereinafter, the present invention will be described more specifically with reference to the drawings.
A first embodiment of the present invention is shown in FIGS. FIG. 1 shows a longitudinal section of an embodiment in which heat is utilized by installing a first jacket vessel 6 and a second jacket vessel 7 between a fuel cell stack 1 and a heat insulation layer 4 in a cylindrical solid oxide fuel cell system. FIG. FIG. 2 is a cross-sectional view taken along the line AA ′ of FIG. The fuel battery cell 101 has a cylindrical shape, and an upper end in FIG. 1 is an open end and a lower end is a sealed end, and a plurality of fuel battery cells 101 are connected by a connecting member (not shown). An air electrode (not shown) is formed inside the electrolyte (not shown) of the fuel cell 101 and a fuel electrode (not shown) is formed outside. An air introduction tube 102 is inserted inside each fuel cell 101, and air is supplied from the air supply line 2 to the air electrode of each fuel cell 101 via the air distributor 103 and the air introduction tube 102. Is supplied. Air is used as the oxidant gas. On the other hand, the fuel gas is supplied from below the fuel cell 101 to the fuel electrode of the fuel cell 101, and a power generation reaction occurs in the power generation chamber 104 surrounded by the stack container 105, generating electric power, reaction heat, and water. The Electric power is taken out and used through a lead wire (not shown) connected to the air electrode and the fuel electrode. The exhaust gas is discharged outside the stack container 105 through the exhaust gas discharge line 8. Since the operating temperature of the solid oxide fuel cell is about 700 to 1000 ° C., a heat resistant alloy steel, a heat resistant stainless steel, or the like is used as a constituent material of the stack container 105.

  The first jacket container 6 is installed on the outer side of the lower side surface and the lower surface of the stack container 105. Water is supplied from the water supply line 5, heated by power generation reaction heat, and evaporated to generate water vapor. The generated water vapor is connected and supplied to a second jacket vessel 7 described later via a water vapor extraction line 501. The water vapor extraction line 501 can be embedded in the heat insulating and heat insulating layer 4. It is also possible to take out a part of the generated water vapor and use it. The ratio of the water vapor and the water vapor supplied to the second jacket container 7 can be adjusted using a flow rate control valve (not shown). The first jacket container 6 is generally configured using the same constituent material as that of the stack container 105 and is installed on the outer surface of the stack container 105 by a joining method such as welding.

  Another second jacket container 7 is installed outside the upper side surface and the upper surface outside the stack container 105, and natural gas is supplied from the fuel gas supply line 3. Since the inside of the second jacket vessel 7 is filled with a reforming catalyst (not shown), a steam reforming reaction takes place, the natural gas is converted into a hydrogen rich gas, and the inside of the stack vessel 105 is passed through the hydrogen rich gas line 301. It is supplied to the power generation chamber 104. The reforming catalyst is generally in the form of a pellet in which an appropriate metal such as nickel or ruthenium is supported on a support such as alumina. However, the reforming catalyst is supported on other metal or in other shapes such as a spherical shape. Can also be used. As the steam necessary for the steam reforming reaction, steam generated in the first jacket vessel 6 is used. Power generation reaction heat is used as a heat source for the endothermic reaction of the steam reforming reaction. The second jacket container 7 is also generally made of a constituent material such as heat-resistant alloy steel or heat-resistant stainless steel equivalent to the stack container 105, and is installed on the outer surface of the stack container 105 by a joining method such as welding. ing. In the present embodiment, since the reforming catalyst is filled in the second jacket vessel 7, it is preferable to provide a maintenance port for filling or replacing the reforming catalyst.

  2 is a cross-sectional view taken along the line A-A 'of FIG. As apparent from FIG. 2, the second jacket container 7 is surrounded so as to cover the entire outer periphery of the fuel cell stack 1. Although FIG. 2 illustrates a stack container having a quadrangular cross-sectional shape, a jacket container can be similarly installed even if it is another polygonal shape or a circular shape.

As can be seen from FIGS. 1 and 2, the first jacket container 6 and the second jacket container 7 are almost all of the outer surface of the fuel cell stack 1 except for the space necessary for supplying fuel gas and air and discharging exhaust gas. It is installed in the part of. Therefore, most of the reaction heat that has been radiated through the heat insulation and heat insulation layer 4 can be effectively used as a heat source for the endothermic reaction of the steam reforming reaction of the second jacket vessel 7.
Furthermore, a third jacket container (not shown) may be installed as a gas heater, and for example, air (oxidant gas) may be preheated by reaction heat.

  A second embodiment of the present invention is shown in FIG. FIG. 3 is an example in which heat utilization means by the first coiled container 9 and the second coiled container 10 is installed, and the heat utilization means is provided in the heat insulating heat insulating layer 4 disposed around the fuel cell stack 1. Applicable when installed. The first coiled container 9 is installed in the heat insulating and heat insulating layer 4 on the lower outer side of the stack container 105. Water is supplied from the water supply line 5, heated by power generation reaction heat, and evaporated to generate water vapor. The generated water vapor is connected and supplied to a second coiled container 10 described later via a water vapor extraction line 501. The water vapor extraction line 501 can also be embedded in the heat insulating and heat insulating layer 4. Part of the generated water vapor can be taken out and used.

  The second coiled container 10 is installed in the heat insulating and heat insulating layer 4 above the stack container 105, and natural gas is supplied from the fuel gas supply line. The inside of the second coiled vessel 10 is filled with a reforming catalyst (not shown), a steam reforming reaction takes place, the natural gas is converted into a hydrogen rich gas, and the inside of the stack vessel 105 is passed through the hydrogen rich gas line 301. It is supplied to the power generation chamber 104. As the steam necessary for the steam reforming reaction, steam generated in the first coiled container 9 is used. The power generation reaction heat can be effectively used as a heat source for the endothermic reaction of the steam reforming reaction.

  The first coiled container 9 and the second coiled container 10 are made of carbon steel tubes for piping, alloy steel tubes for piping, stainless steel tubes for piping, and other general metal piping materials, as well as steel tubes for boilers, heat-resistant alloy steel tubes, etc. Can be formed so as to surround the stack container 105 in a spiral or spiral shape. The first coiled container 9 and the second coiled container 10 can be easily installed even if the fuel cell stack 1 has a cylindrical shape, a polygonal cylindrical shape, or other complicated shapes. By adjusting the coil pitch, it can be installed on the outer surface of the fuel cell stack 1 with almost no gap. Furthermore, since the first coiled container 9 and the second coiled container 10 have good followability to thermal expansion, the generation of thermal stress can be greatly reduced. Details of the material, shape, dimensions, etc. of the first coiled container 9 and the second coiled container 10 depend on the design conditions such as the type / operating temperature / scale of the fuel cell stack 1 and the type / temperature of the heat utilization means. It can be selected appropriately.

  In the present invention, a plurality of heat utilization means can be combined. For example, a fuel reformer, a gas heater, a liquid heater, a steam generator, a heat accumulator, and a thermoelectric conversion element can be used in appropriate combination. Moreover, the jacket container and the coil-shaped container can be combined with the structure of the plurality of heat utilization means depending on the shape of the fuel cell stack and the configuration requirements of the fuel cell system. Furthermore, each jacket container and coil-shaped container do not need to be an integral type, but can be divided according to the shape of the fuel cell stack and the configuration requirements of the fuel cell system. When the fuel cell stack is operated, temperature distribution may occur depending on the fuel gas supply conditions, the oxidant gas supply conditions, and the power generation reaction conditions inside the fuel cell stack. In such a case, it is preferable to install a plurality of appropriate heat utilization means at an appropriate location with an appropriate configuration in accordance with the temperature distribution state of the fuel cell stack.

  A thermoelectric conversion element is an element that converts heat (temperature difference) into electric power based on the Seebeck effect. Various thermoelectric conversion materials, such as Bi-Te type and silicide type, and various skeleton type and monolithic type have been proposed as the module configuration of the thermoelectric conversion element. For example, in the first embodiment, a thermoelectric conversion element is installed on the outer surface of the first jacket container and / or the second jacket container, and the remaining reaction heat recovered by the first jacket container and / or the second jacket container. May be recovered as electric power. An appropriate one can be selected according to the use conditions such as the temperature and temperature difference of the installation place of the thermoelectric conversion element.

  The thermal energy and electrical energy recovered by the heat utilization means can be used in the high temperature fuel cell system, but can also be used for other external applications.

In the present invention, the high temperature fuel cell mainly refers to a solid oxide fuel cell having an operating temperature of about 700 to 1000 ° C. and a molten carbonate fuel cell having an operating temperature of about 650 ° C. However, the present invention can be applied to a phosphoric acid fuel cell having an operating temperature of about 250 ° C. or a polymer electrolyte fuel cell having an operating temperature of about 80 ° C. without departing from the gist of the present invention.

1 is a longitudinal sectional view of a high temperature fuel cell system according to a first embodiment of the present invention. 1 is a cross-sectional view of a high temperature fuel cell system according to a first embodiment of the present invention. It is a longitudinal cross-sectional view of the high temperature type fuel cell system of 2nd embodiment of this invention. It is a longitudinal cross-sectional view of the conventional high temperature type fuel cell system.

Explanation of symbols

1 fuel cell stack, 2 oxidant gas supply line, air supply line, 3 fuel gas supply line, 4 heat insulation layer, 5 water supply line, 6 first jacket vessel, 7 second jacket vessel, 8 exhaust gas discharge line, 9 First coiled container, 10 Second coiled container, 101 Fuel cell, 102 Air introduction pipe, 103 Air distributor, 104 Power generation chamber, 105 Stack container, 110 Fuel reformer, 301 Hydrogen rich gas line, 501 Water vapor line

Claims (13)

A fuel cell stack formed by connecting a plurality of fuel cells each including an electrolyte and a fuel electrode and an air electrode on both sides of the electrolyte;
An oxidant gas supply line for supplying an oxidant gas to the fuel cell stack;
A fuel gas supply line for supplying fuel gas to the fuel cell stack;
A heat insulating and heat insulating layer disposed around the fuel cell stack;
In a high temperature fuel cell system comprising:
A high-temperature fuel cell system comprising heat utilization means between the fuel cell stack and the heat insulation heat insulation layer or in the heat insulation heat insulation layer. The high-temperature fuel cell system according to claim 1, wherein the heat utilization means is a fuel reformer. The high-temperature fuel cell system according to claim 2, wherein the fuel reformer is provided in the middle of the fuel gas supply line. The high-temperature fuel cell system according to claim 1, wherein the heat utilization means is a gas heater. The high-temperature fuel cell system according to claim 4, wherein the fuel reformer is provided in the middle of the fuel gas supply line. The high-temperature fuel cell system according to claim 4, wherein the gas heater is provided in the middle of the oxidant gas supply line. The high-temperature fuel cell system according to claim 1, wherein the heat utilization means is a liquid heater. The high-temperature fuel cell system according to claim 1, wherein the heat utilization means is a steam generator. The high-temperature fuel cell system according to claim 1, wherein the heat utilization means is a regenerator. The high temperature fuel cell system according to any one of claims 1 to 9, wherein the heat utilization means is a jacket container surrounded by the fuel cell stack. The high-temperature fuel cell system according to claim 1, wherein the heat utilization means is a coiled container surrounded by the fuel cell stack. The high-temperature fuel cell system according to claim 1, wherein the heat utilization means is a thermoelectric conversion element. The high-temperature fuel cell system according to any one of claims 1 to 12, wherein the heat utilization means is a combination of two or more heat utilization means.

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