JP2005327513A - Hot standby method for solid oxide fuel cell and system for the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hot standby system for an SOFC system utilizing heat generated at hot standby as a warming heat by actively utilizing carbon deposited from hydrocarbon group fuel supplied to the SOFC, and also to provide a system for carrying out a hot standby method. <P>SOLUTION: On the hot standby method for a solid oxide fuel cell system comprising a solid oxide fuel cell stack and an off-gas combustion part, a catalyst layer for thermal decomposition of hydrocarbon group fuel is arranged on a fuel supply tube supplying fuel to the solid oxide fuel cell stack. When the system is operated, hydrogen and carbon are generated from the hydrocarbon group fuel by using a catalyst for thermal decomposition, and the hydrogen is utilized for power generation and the carbon is deposited on the catalyst. When the system is stopped, the carbon deposited on the catalyst is utilized for heat insulation. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a hot standby method for a solid oxide fuel cell system and a system for carrying out the hot standby method, and also relates to a method for maintaining an anode atmosphere when the operation of the solid oxide fuel cell system is stopped.

  A solid oxide fuel cell (hereinafter abbreviated as SOFC as appropriate) has a fuel electrode and an air electrode (oxygen electrode when oxygen is used as the oxidant gas) with a solid electrolyte in between. And a three-layer unit of fuel electrode (anode) / electrolyte (solid oxide electrolyte) / air electrode (cathode). During the operation, electric power is taken out by supplying fuel to the anode side and supplying an oxidant gas such as air, oxygen-enriched air or oxygen to the cathode side to cause an electrochemical reaction. Hereinafter, air is taken as an example as appropriate, but the same applies to other oxidant gases. This fuel cell generally has a high operating temperature of about 1000 ° C., but recently, a fuel cell having an operating temperature of about 800 ° C. or lower, for example, about 750 ° C. is being developed.

Oxygen in the air introduced into the cathode becomes oxide ions (O ²⁻ ) at the cathode, and reaches the anode through the solid oxide electrolyte. Here, it reacts with the fuel gas (hydrogen, carbon monoxide) introduced into the anode to release electrons, thereby generating a reaction product of electricity and water or carbon monoxide. Spent air at the cathode is discharged as cathode offgas, and spent fuel at the anode is discharged as anode offgas. Since the voltage of one unit cell is low, the unit cell is usually configured by stacking a plurality of layers.

  As an operation mode of the SOFC system, continuous operation is efficient, but depending on the usage, it is necessary to frequently start and stop such as daytime operation-nighttime stop. When the stop time is long, a so-called cold start method is effective in which the system is completely stopped and restarted after the temperature is lowered to room temperature. However, when the stop time is short, the system is not completely stopped, only power generation is stopped, and the so-called hot standby method is applied to maintain the temperature close to the operation temperature, and the operation is started immediately from that state. It is efficient to apply a so-called hot start method. Further, it is necessary to control the atmosphere so that the anode portion of the SOFC is not oxidized during hot standby.

  However, in order to apply the hot standby method, it is necessary to supply extra heat commensurate with the heat dissipation loss for maintaining the SOFC system at a predetermined temperature. As a method of supplying the heat retaining heat, a method of using an electric heater, a method of using fuel gas by burning, and the like can be considered. 1 and 2 are diagrams showing a case of heat supply using an electric heater. FIG. 1 shows a state during power generation of the system and FIG. 2 shows a state during hot standby of the system. The SOFC system is configured by surrounding the SOFC stack and the off-gas combustion section with a heat insulating material, but is also configured by housing them in a heat insulating container. As shown in FIG. 1, during operation of the system, the flue gas from the off-gas combustion unit is used for heating the fuel and air supplied to the SOFC stack via the heat exchanger.

  On the other hand, as shown in FIG. 2, during the hot standby of the system, the supply of fuel and air is stopped, and the combustion exhaust gas outlet pipe from the off-gas combustion unit is also sealed. Instead of these, heat corresponding to the heat dissipation loss is supplied from a heat source, for example, an electric heater. As described above, in order to apply the hot standby method in the prior art, it is necessary to supply extra heat corresponding to a heat dissipation loss for maintaining the system at a predetermined temperature by an electric heater or the like. Since this heat is only for heat retention, the heat energy required for this heat supply is wasted. Further, it is necessary to control the atmosphere so that the anode portion of the SOFC is not oxidized during hot standby, and the method of supplying the reducing gas for that purpose also becomes a problem.

By the way, in SOFC, hydrogen and carbon monoxide are used as fuel, but methane is steam-reformed by the catalytic action of a metal that is a component of the anode, such as nickel, to form hydrogen and carbon monoxide. In addition to fuel containing hydrogen and carbon monoxide, fuel containing methane is also used. However, the carbon number of C ₂ and higher hydrocarbons in the fuel, i.e. ethane, ethylene, propane and butane are contained, to produce carbon in piping and the anode of the SOFC, which inhibit the electrochemical reaction cell The performance deteriorates, and it becomes fatal in the SOFC that is used repeatedly for a long time.

  For this reason, it is necessary to eliminate deposited carbon as much as possible, but instead, a technique for using the deposited carbon again as a fuel for a fuel cell is being developed. For example, Japanese Patent Laid-Open No. 2003-327411 discloses that precipitated carbon permeates through an electrolyte membrane and reacts with oxygen supplied to an anode from an oxidant gas passage to be converted into carbon monoxide and reused as a fuel. Has been. FIG. 10 is a diagram showing a carbon-based fuel cell disclosed therein.

JP 2003-327411 A

As shown in FIG. 10, the carbon-based fuel cell has a single cell three-layer film structure of a flat plate reforming unit and a flat plate power generation unit. The power generation unit includes a flat plate electrolyte membrane 1, an anode electrode 2, and a cathode electrode 3. And a conventional SOFC with a separator 6. The reforming section, like the power generation section, has a flat-plate three-layer film structure, and has a structure in which the cathode 12 and the anode 13 are integrated on each surface of the electrolyte membrane 11. An air passage 14 through which an air flow can flow is formed between the cathode 12 and the flat plate separator 16. Methane supplied to the fuel passage 15 reacts with oxygen ions permeated through the electrolyte membrane 11 due to a difference in oxygen partial pressure with the air passage 14 to be converted into carbon monoxide and hydrogen, and at the same time, cracking reaction (CH ₄ → Carbon is precipitated by C + 2H ₂ ).

Although the cracking reaction is an endothermic reaction, it only requires much smaller reaction heat than the conventional steam reforming reaction. The deposited carbon is oxidized by an electrochemical reaction: C + O ²⁻ → CO + 2e, and converted to carbon monoxide. This reaction is a partial oxidation exothermic reaction, and this heat of reaction supplements the heat required for the cracking reaction. Thus, a reformed gas containing a relatively large amount of hydrogen and carbon monoxide is generated in the fuel passage 15, and the reformed gas is supplied to the reformed gas passage 5, so that an exothermic reaction in the power generation unit proceeds. At that time, if desired, a relatively small amount of water vapor is supplied to the fuel flow path 15, and the steam reforming reaction of the fuel gas proceeds simultaneously in the fuel flow path. The supply of water vapor is effective in preventing accumulation of carbon precipitated during the cracking reaction.

  The present invention provides a hot standby method for a SOFC system that actively uses precipitated carbon from hydrocarbon fuel supplied to the SOFC and uses it as heat during hot standby, and a system for implementing the hot standby method. In addition, an object of the present invention is to provide a method for maintaining the anode atmosphere when the SOFC system is stopped.

  The present invention relates to (1) a hot standby method of a solid oxide fuel cell system including a solid oxide fuel cell stack and an off-gas combustion section, wherein a hydrocarbon is provided in a fuel supply pipe to the solid oxide fuel cell stack. The catalyst layer for thermal decomposition of the system fuel is arranged, and when the system is operated, hydrogen and carbon are generated from the hydrocarbon fuel by the catalyst layer for thermal decomposition, and the hydrogen is used for power generation in the stack, and the carbon is used. A hot standby method for a solid oxide fuel cell system using precipitated carbon, characterized in that the carbon deposited on the catalyst is used for heat insulation of the system when the system is shut down and the system is shut down. Provide a system for implementing the law.

  The present invention relates to (2) a hot standby method of a solid oxide fuel cell system including a solid oxide fuel cell stack and an off-gas combustion section, and a fuel supply pipe and an oxidant for the solid oxide fuel cell stack A carbon-based fuel cell is arranged in the supply pipe, and when the system is operated, hydrogen and carbon are generated from the hydrocarbon-based fuel by the carbon-based fuel cell, and the hydrogen is used for power generation in the stack. And a hot standby method for a solid oxide fuel cell system using precipitated carbon, wherein the deposited carbon is used for heat generation and heat retention when the system is shut down. A system for implementing the above is provided.

  The present invention is (3) a method for maintaining an anode atmosphere of a solid oxide fuel cell system including a solid oxide fuel cell stack and an off-gas combustion section, and carbonizing a fuel supply pipe to the solid oxide fuel cell stack A catalyst layer for thermal decomposition of hydrogen-based fuel is arranged, and during operation of the system, hydrogen and carbon are generated from the hydrocarbon-based fuel by the catalyst layer for thermal decomposition, and the hydrogen is used for power generation in the stack, and carbon When the system is shut down, the flue gas from the off-gas combustion section is passed through the thermal decomposition catalyst layer to convert the deposited carbon into carbon monoxide and hydrogen, which is used to maintain the anode atmosphere of the system. A method for maintaining the anode atmosphere of a solid oxide fuel cell system using precipitated carbon is characterized.

  According to the present invention, the heat supply for maintaining the temperature of the SOFC system, which has been a problem during the hot standby of the conventional SOFC system, can be effectively obtained by utilizing the deposited carbon on the pyrolysis catalyst layer or the anode of the carbon-based fuel cell. Can be done automatically. In addition, by using a thermal decomposition catalyst layer or a carbon-based fuel cell, the amount of heat for heat retention can be freely adjusted, and a reducing gas for maintaining the reducing atmosphere of the anode can be simultaneously supplied.

<Hot standby method and system of SOFC system using catalyst layer for thermal decomposition>
The present invention (1) is a SOFC system hot standby method using precipitated carbon and a system for implementing the hot standby method. Then, a catalyst layer for pyrolysis of hydrocarbon fuel is arranged in the fuel supply pipe to the SOFC stack, and during operation of the system, hydrogen and carbon are generated from the hydrocarbon fuel by the catalyst catalyst for pyrolysis. In addition to being used as a fuel for power generation in real time, carbon is deposited on the catalyst, and the carbon deposited on the catalyst is used for heat retention of the system when the system is stopped.

  The SOFC system targeted in the present invention is an SOFC system including an SOFC stack and an off-gas combustion section. These are configured by being surrounded by a heat insulating material, but are also configured by accommodating them in a heat insulating container. Then, a catalyst layer for thermal decomposition of hydrocarbon fuel is disposed in the fuel supply pipe to the SOFC stack. The thermal decomposition catalyst layer accommodates the thermal decomposition catalyst in a granular, pellet, tablet or other suitable shape in a container, and connects a fuel introduction pipe to this and a fuel outlet pipe on the opposite side. It is composed by doing.

  During system operation, hydrogen and carbon are produced from the hydrocarbon-based fuel by the thermal decomposition catalyst layer, and hydrogen is used as a fuel for power generation in real time, and at the same time, carbon is deposited on the thermal decomposition catalyst. When the operation of the SOFC system is stopped, the carbon deposited on the thermal decomposition catalyst layer is converted into carbon monoxide and hydrogen by the combustion exhaust gas from the off-gas combustion section, and the generated heat is used for heat retention of the system. The required amount of combustion exhaust gas is used. Moreover, since carbon monoxide and hydrogen are reducing gases, the anode of the SOFC stack can be kept in a reducing atmosphere, and oxidation of the anode portion can be prevented.

<Hot standby method and system of SOFC system using carbon fuel cell>
The present invention (2) is a SOFC system hot standby method using precipitated carbon and a system for implementing the hot standby method. Carbon fuel cells are arranged in the fuel supply pipe and oxidant supply pipe to the SOFC stack, and during operation of the system, hydrogen and carbon are generated from hydrocarbon fuel by the carbon fuel cell, and the hydrogen is used for power generation. In addition, the carbon is deposited on the carbon-based fuel cell, and the carbon deposited on the carbon-based fuel cell is used for heat retention of the power generation and system when the system is stopped.

  The SOFC system targeted in the present invention is an SOFC system including an SOFC stack and an off-gas combustion section. These are configured by being surrounded by a heat insulating material, but are also configured by accommodating them in a heat insulating container. Then, a carbon-based fuel cell is disposed in a fuel supply pipe and an oxidant supply pipe to the SOFC stack (or an air supply pipe when the oxidant is air). The carbon-based fuel cell may have a structure similar to that of SOFC. For example, an anode and a cathode are stacked on both sides of a flat electrolyte membrane, and separators are provided at intervals with respect to the anode surface and the cathode surface, respectively. It is composed by arranging. A fuel flow path is formed between the anode surface and the separator, and an air flow path is formed between the cathode surface and the separator. The SOFC system and the carbon-based fuel cell are surrounded by a heat insulating material, but may be accommodated in a heat insulating container.

  Since the fuel flow path is between the anode surface and the separator, and the air flow path is between the cathode surface and the separator, the fuel supply pipe to the SOFC stack faces one side of the fuel flow path, and the air to the SOFC stack The supply pipe faces one side of the air flow path. The fuel flow path and the air flow path are connected to a fuel supply pipe and an air supply pipe to the SOFC stack, respectively. Thus, the fuel flow path through the carbon-based fuel cell is connected to the anode side of the SOFC stack, and the other end of the air flow path is connected to the anode side of the SOFC stack.

  During operation of the SOFC system, hydrogen and carbon are generated from hydrocarbon fuel by a carbon-based fuel cell, hydrogen is used as a fuel for power generation in real time, and carbon is deposited on the anode of the carbon-based fuel cell. When the SOFC system is shut down, the air from the air supply pipe is passed through the anode of the carbon-based fuel cell, the carbon deposited there is converted into carbon monoxide and hydrogen, and the generated heat is used to keep the system warm. Use. Moreover, since carbon monoxide and hydrogen are reducing gases, the anode of the SOFC stack can be kept in a reducing atmosphere, and oxidation of the anode portion can be prevented.

  Here, the cracking reaction of methane in the catalyst layer for thermal decomposition or the carbon-based fuel cell in the present invention, that is, the thermal decomposition reaction, is an endothermic reaction and is represented by the following formula (1). As shown in formula (1), methane generates carbon and hydrogen by a cracking reaction. Although this equilibrium reaction is close to 90% at about 900 ° C., it decreases as the temperature decreases, to about 29% at 600 ° C., and the reaction rate also decreases as the temperature decreases. For this reason, the reaction of carbon deposition can be controlled by controlling the temperature.

  On the other hand, the cell reaction using the deposited carbon as a fuel is an exothermic reaction and is represented by the following formula (2). Further, when water vapor or carbon dioxide is supplied to the precipitated carbon, reactions of the following formulas (3) to (4) occur, and both reactions are endothermic reactions. When these reactions (2) to (4) are viewed as overalls, they are exothermic reactions (−393 + 131.3 + 172.4 = −89.3 kJ), and the reaction of the formula (3) becomes dominant. For the removal of precipitated carbon, these reactions (2) to (4) may be used as overalls, or one or two of the reactions (2) to (4) may be used.

In the present invention, a catalyst layer for thermal decomposition of a hydrocarbon fuel or a carbon-based fuel cell is combined with the SOFC system, and these reactions (1) to (4) are used for the hot standby method of the SOFC system. Among these, the reaction (1) is used for carbon precipitation, and one or more of the reactions (2) to (4) are used for removal of the precipitated carbon. The combustion exhaust gas from the off-gas combustion section contains oxygen (O ₂ ), water vapor (H ₂ O) and carbon dioxide (CO ₂ ) as its components, so that the off-gas combustion section is used as an oxygen source necessary for the reaction of the above formula (2). Is used as the water vapor and carbon dioxide source necessary for the reactions of the above formulas (3) to (4).

<Specific embodiment of hot standby method and system using thermal decomposition catalyst layer>
When using a pyrolysis catalyst layer, a hydrocarbon pyrolysis catalyst layer is combined with the SOFC system. FIGS. 3 to 4 are diagrams showing such modes. FIG. 3 is a state during power generation in the system, and FIG. 4 is a state during hot standby of the system. The present SOFC system is configured by surrounding the SOFC stack and off-gas combustion section with a heat insulating material, but they may be housed in a heat insulating container. As shown in FIGS. 3 to 4, in a normal SOFC system, a hydrocarbon pyrolysis catalyst layer 21 is arranged in a fuel supply pipe. And the recirculation line 24 of the combustion exhaust gas branched from the combustion exhaust gas discharge pipe 23 from an off-gas combustion part is provided.

  The catalyst for pyrolysis is not particularly limited as long as it is a catalyst capable of cracking hydrocarbon fuels such as city gas, natural gas, and petroleum gas, that is, pyrolyzing to deposit carbon, but examples thereof include iron. Examples include catalysts, iron-nickel catalysts, and vanadium oxide catalysts. These can be used in the form of granules, pellets, tablets and other appropriate shapes.

  As shown in FIG. 3, during power generation in the SOFC system, before supplying the hydrocarbon-based fuel to the SOFC stack, the fuel is passed through the thermal decomposition catalyst layer 21 to deposit carbon. At this time, the exhaust gas recirculation line 24 from the off-gas combustion section is closed. Then, as shown in FIG. 4, when the operation of the SOFC system is stopped, the fuel supply is stopped, the combustion exhaust gas recirculation line 24 is opened, and the combustion exhaust gas from the off-gas combustion part is recirculated to the thermal decomposition catalyst layer 21. At this time, air continues to be supplied to the stack. Since the system is shut down, air passes through the SOFC stack and enters the off-gas combustion section.

  From this point onward, according to the equation (3), the precipitated carbon reacts with the water vapor in the combustion exhaust gas to produce hydrogen and carbon monoxide. The overall reaction as a system at the time of shutdown is substantially only the reaction of the above formula (3). The generated gases (reducing gases) pass through the SOFC stack and enter the off-gas combustion section where they are mixed with air and burned to generate heat. The generated heat can be used to heat the SOFC stack to keep warm during hot standby. Further, the amount of heat generated in the SOFC system per hour can be adjusted by controlling the recirculation amount of the combustion exhaust gas. 3-4, V1 is a valve (three-way valve) for it. In addition to the three-way valve, a flow control valve may be disposed in the recirculation line 24.

  Hydrogen and carbon monoxide produced by the reaction of precipitated carbon with water vapor in the combustion exhaust gas are reducing gases, and this gas passes through the fuel supply pipe 22 and the anode of the SOFC stack to the off-gas combustion section. Thus, the anode can be maintained in a reducing atmosphere.

<Specific embodiment of hot standby method and system using carbon fuel cell>
When using a carbon-based fuel cell, the carbon-based fuel cell is combined with the SOFC system. FIGS. 5 to 6 are diagrams showing such modes. FIG. 5 is a system during power generation, and FIG. 6 is a system hot standby. As shown in FIGS. 5 to 6, in a normal SOFC system, the carbon-based fuel cell 25 is disposed in the middle of the fuel supply pipe 26 and the air supply pipe 27.

  The configuration of the carbon-based fuel cell used in the present invention is basically the same as that of the conventional SOFC as in the reforming section in FIG. 10, and may be a general SOFC configuration. The role of this fuel cell is to connect the electric power generated there during hot standby to an electric heater to generate heat and keep the system warm, so a single cell may be used, but multiple layers may be stacked. . FIG. 7 shows a further example of the configuration. As shown in FIG. 7, the anode and the cathode are arranged with the solid electrolyte sandwiched between them. Fuel is supplied to the anode side, and air is supplied to the cathode side to cause an electrochemical reaction. It is. In the present invention, this electric power is used as a power source for the electric heater.

  As shown in FIG. 5, when generating power in the SOFC system, before using the hydrocarbon fuel such as city gas or the fuel and air preliminarily reformed to hydrogen, carbon monoxide and methane and the air to the SOFC stack, Through the battery 25, carbon is deposited on the anode. At this time, the carbon-based fuel cell 25 is a closed circuit and does not generate power. The fuel and air are introduced into the SOFC stack after passing through the carbon-based fuel cell 25.

  When the operation of the SOFC system is stopped, as shown in FIG. 6, the fuel supply is stopped, and the carbon-based fuel cell 25 generates power using the carbon deposited at the anode portion of the carbon-based fuel cell 25 through the air. That is, carbon deposited on the anode reacts with oxygen ions that have permeated the electrolyte membrane from the cathode, and is converted into carbon monoxide and hydrogen to generate electricity. The generated electric power is used to generate heat by the electric heater 28, and the heat is used to keep the system warm.

  At this time, heat generation also occurs in the carbon-based fuel cell portion. The heat is introduced into the SOFC stack along with the gas from the carbon-based fuel cell 25 through the fuel supply pipe 26 and the air supply pipe 27, so that it is used for heat insulation of the system together with the heat generated by the electric heater 28. Regarding the SOFC system using a carbon-based fuel cell as well, the reaction at the time of operation stoppage is an exothermic reaction when the overall system is viewed as an overall reaction, and the reaction of the above formula (3) becomes dominant.

  In addition, in the hot standby method and system using the carbon-based fuel cell of the present invention, the carbon-based fuel cell can be surrounded with a heat insulating material together with the SOFC system or disposed in a heat insulating container. FIG. 8 is a diagram showing this aspect. As shown in FIG. 8, the carbon-based fuel cell 25 is disposed in the heat insulating container close to the SOFC system. Thereby, the heat radiation from the carbon-based fuel cell 25 can be reduced, and the heat retention effect during the hot standby of the system can be more effectively performed. Other points are the same as in the above embodiment.

  Further, in the hot standby method and system using the carbon-based fuel cell of the present invention, a cell near the fuel inlet can be used as the carbon-based fuel cell among cells constituting a normal flat plate type SOFC stack. . FIG. 9 is a diagram schematically showing the mode. In FIG. 9, description of separators and the like is omitted. As shown in FIG. 9, among the cells constituting the SOFC stack formed by stacking a plurality of cells, the cells near the fuel inlet are used as carbon-based fuel cells. In FIG. 9, spacers are arranged between the cells used as the carbon-based fuel cell among the cells constituting the SOFC stack and the other cell groups, but the intervals are not necessarily required.

  In addition, the carbon-based fuel cell used in the present invention can be used not only for keeping the system warm but also for taking out electric power if the characteristics are good. In the case of performing only the heat retention, there is no problem even if the performance is low. If there is no problem in durability, the battery configuration may be reduced in cost.

  EXAMPLES Hereinafter, although this invention is demonstrated in more detail based on an Example, it cannot be overemphasized that this invention is not limited by an Example. The present embodiment is an example using the SOFC system configured as shown in FIGS.

As shown in FIGS. 3 to 4, as the SOFC system, an SOFC stack with an output of 10 kW and an off-gas combustion part are accommodated in a heat insulating container. The operating temperature of the SOFC stack is 750 ° C., and the heat dissipation from the SOFC system is about 1 kW. Then, it is driven for 16 hours in the daytime and stopped for 8 hours at night. In this case, the amount of heat required for heat retention when the system is stopped is 1 × 10 ³ × 3600 × 8 = 28.8 × 10 ³ kJ.

  Since the calorific value of 1 mol of methane is 890 kJ, about 32 mol of methane is required for heat retention. On the other hand, in the case of this SOFC system, carbon (of methane) and 2 moles of hydrogen are generated from 1 mole of methane from the formula (1), and the reaction heat of carbon is 393 from the formula (2). The calorific value of hydrogen is 286 kJ, and about 29 mol of methane is required for heat insulation. Therefore, about 10% of the fuel consumption can be saved as compared with the conventional system. This mechanism is because the above formula (1) is an endothermic reaction, and surplus heat during operation of the SOFC system is changed to carbon and accumulated.

In order to keep the temperature using only the precipitated carbon, 73 mol% of methane is required from the combustion heat of carbon. The pyrolysis reaction of 73 moles of methane generates 146 moles of hydrogen. In the case of an SOFC system with an output of 10 kW as in this example, the total amount of power generated in an operation time of 16 hours is 7.2% 10 ⁵ kJ [= (10 × 10 ³ × 3600 × 16) /0.8]. If the power generation efficiency of hydrogen fuel is 50% HHV, the amount of hydrogen required for power generation is 2517 moles (= 7.2 × 10 ⁵ kJ).

Here, if the total amount of hydrogen is generated from the reforming of methane, the required amount of hydrogen is about 593 mol [= (2517-146) / 4]. Therefore, 666 (= 593 + 73) mol / day of methane is consumed including the methane used for carbon deposition for hot standby. In addition, if about 11% of the introduced methane is carbon deposited during SOFC operation and used for heat retention during stoppage, the heat retention heat during stoppage can be covered.
Further, during this time, the reducing gas always flows to the anode part of the battery body, so that it is not necessary to supply the reducing gas separately.

Diagram explaining the hot standby method (during power generation) of a conventional SOFC system Diagram explaining the hot standby method (during hot standby) of a conventional SOFC system The figure explaining the hot standby method (at the time of electric power generation) which combined the catalyst layer for thermal decomposition of a hydrocarbon with the SOFC system in this invention The figure explaining the hot standby method (at the time of hot standby) which combined the catalyst layer for thermal decomposition of a hydrocarbon with the SOFC system in this invention The figure explaining the hot standby method (at the time of electric power generation) which combined the carbon utilization fuel cell with the SOFC system in this invention The figure explaining the hot standby method (at the time of hot standby) which combined the carbon utilization fuel cell with the SOFC system in this invention The figure which shows the structural example of a carbon utilization fuel cell used by this invention The figure which shows the aspect which arrange | positions a carbon utilization fuel cell in a heat insulation container by the hot standby method and system using a carbon utilization fuel cell. The figure which shows the aspect which uses the cell near a fuel inlet_port | entrance as a carbon utilization fuel cell among normal flat plate type SOFC stacks by the hot standby method and system using a carbon utilization fuel cell. The figure which shows the carbon utilization fuel cell currently disclosed by the prior gazette

Explanation of symbols

21 catalyst layer for thermal decomposition 22 fuel supply pipe 23 flue gas exhaust pipe from off-gas combustion section 24 flue gas recirculation line V1 flow control valve 25 carbon fuel cell 26 fuel supply pipe 27 air supply pipe 28 electric heater

Claims (11)

  A hot standby method for a solid oxide fuel cell system including a solid oxide fuel cell stack and an off-gas combustion unit, wherein a catalyst for thermal decomposition of hydrocarbon fuel is provided in a fuel supply pipe to the solid oxide fuel cell stack When the system is in operation, hydrogen and carbon are generated from the hydrocarbon-based fuel by the pyrolysis catalyst layer, and the hydrogen is used for power generation in the stack, and the carbon is deposited on the catalyst. A hot standby method of a solid oxide fuel cell system using precipitated carbon, wherein carbon deposited on a catalyst is used for heat insulation of the system when the operation is stopped.   In the hot standby method according to claim 1, when the carbon deposited on the catalyst is used for heat insulation of the system when the operation of the system is stopped, the combustion exhaust gas from the off-gas combustion part is passed through the thermal decomposition catalyst layer, A hot standby method for a solid oxide fuel cell system using precipitated carbon, wherein the deposited carbon is changed into carbon monoxide and hydrogen, and the generated heat is used for heat insulation of the system.   A hot standby method for a solid oxide fuel cell system including a solid oxide fuel cell stack and an off-gas combustion unit, wherein a fuel supply pipe to the solid oxide fuel cell stack and an oxidant supply pipe are carbon-based fuel cells. When the system is operated, hydrogen and carbon are generated from the hydrocarbon-based fuel by the carbon-based fuel cell, and the hydrogen is used for power generation in the stack, and carbon is deposited on the carbon-based fuel cell. A hot standby method for a solid oxide fuel cell system using precipitated carbon, wherein the precipitated carbon is used for heat insulation of the power generation and system when the operation is stopped.   4. The hot standby method according to claim 3, wherein the carbon deposited on the carbon fuel cell when the system is stopped is used to keep the power generation and the system warm. Solid oxidation using precipitated carbon, characterized in that the oxidant gas from the supply pipe is passed through a carbon-based fuel cell to convert the precipitated carbon into carbon monoxide and hydrogen, and the generated heat is used to keep the system warm. Hot standby method for physical fuel cell systems.   A system for performing a hot standby method of a solid oxide fuel cell system including a solid oxide fuel cell stack and an off-gas combustion unit, wherein a hydrocarbon system is provided in a fuel supply pipe to the solid oxide fuel cell stack A catalyst layer for thermal decomposition of fuel is arranged, and during operation of the system, hydrogen and carbon are generated from hydrocarbon fuel by the catalyst layer for thermal decomposition, and the hydrogen is used for power generation and carbon is deposited on the catalyst. In order to implement a hot standby method for a solid oxide fuel cell system using precipitated carbon, characterized in that carbon deposited on the catalyst is used for heat insulation of the system when the system is shut down. System.   6. The system for carrying out the hot standby method according to claim 5, wherein when the system is stopped, carbon deposited on the catalyst is used for heat insulation of the system, and the combustion exhaust gas from the off-gas combustion section is pyrolyzed. A solid oxide fuel cell system using precipitated carbon, wherein the deposited carbon is converted into carbon monoxide and hydrogen through the catalyst layer for use, and the generated heat is used for heat insulation of the system. A system for implementing the hot standby method.   A system for performing a hot standby method of a solid oxide fuel cell system including a solid oxide fuel cell stack and an off-gas combustion unit, wherein a fuel supply pipe and an oxidant supply are supplied to the solid oxide fuel cell stack A carbon-based fuel cell is placed in the tube, and during operation of the system, hydrogen and carbon are generated from hydrocarbon fuel by the carbon-based fuel cell, and the hydrogen is used for power generation and carbon is deposited on the carbon-based fuel cell. When the system is shut down, the carbon deposited on the carbon-utilized fuel cell is used for power generation and heat retention of the system. A system for implementing the standby method.   8. The system for carrying out the hot standby method according to claim 7, wherein when the system is stopped, carbon deposited on the carbon-based fuel cell is used for heat retention as the power generation and system. The oxidant gas from the oxidant supply pipe to the battery stack is passed through the carbon-based fuel cell, and the deposited carbon is converted into carbon monoxide and hydrogen, and the generated heat is used for heat insulation of the system. A system for carrying out a hot standby method of a solid oxide fuel cell system using the precipitated carbon.   The system for carrying out the hot standby method according to claim 7 or 8, wherein the carbon-based fuel cell system is enclosed with a heat insulating material together with a solid oxide fuel cell, or disposed in a heat insulating container. A system for carrying out a hot standby method of a solid oxide fuel cell system using the precipitated carbon.   The system for implementing the hot standby method according to any one of claims 7 to 9, wherein a cell in the vicinity of the fuel inlet among the cells constituting the solid oxide fuel cell stack is used as a carbon-based fuel cell. A system for carrying out a hot standby method of a solid oxide fuel cell system using precipitated carbon, which is characterized by the above. A method for maintaining an anode atmosphere of a solid oxide fuel cell system including a solid oxide fuel cell stack and an off-gas combustion section, for pyrolyzing hydrocarbon fuel in a fuel supply pipe to the solid oxide fuel cell stack A catalyst layer is disposed, and during operation of the system, hydrogen and carbon are generated from hydrocarbon fuel by the thermal decomposition catalyst layer, and the hydrogen is used for power generation in the stack, and carbon is deposited on the catalyst, and the system is When the operation is stopped, the flue gas from the off-gas combustion section is passed through the thermal decomposition catalyst layer to convert the precipitated carbon into carbon monoxide and hydrogen, which is used for maintaining the anode atmosphere of the system. A method for maintaining the anode atmosphere of a solid oxide fuel cell system to be used.

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