JP2016122507A - Solid oxide type fuel battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid oxide type fuel battery that can prevent damage of a fuel battery cell stack while suppressing consumption of fuel gas and pure water as much as possible when power generation operation is stopped.SOLUTION: A solid oxide type fuel battery 1 has power generation operation stop controlling means for supplying a fuel battery cell stack 21 of a fuel battery power generation module 2 with oxidant gas and reformed fuel gas generating by reforming fuel gas with water vapor to perform power generation operation, stopping extraction of power from the fuel battery power generation module 2 and also stopping supply of the fuel gas, the oxidant gas and pure water for water-vapor reforming to the fuel battery power generation module 2 when the power generation operation in the fuel battery power generation module 2 is stopped, and then intermittently supplying respective set amounts of fuel gas, oxidant gas and pure water for water-vapor reforming when the temperature of the fuel battery power generation module 2 is equal to a first set temperature or less.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a solid oxide fuel cell, and more particularly to an improved fuel cell power module stopping process after power generation operation is stopped.

  Conventionally, a pair of electrodes (oxygen electrode and fuel electrode) has been provided on an electrolyte using ion conductive ceramics such as zirconia, and an oxidant gas has been supplied to the oxygen electrode (cathode) side and the fuel electrode (anode) side has been modified. Solid oxide fuel cells that generate electricity by supplying high quality fuel gas (hydrogen-containing gas) and reacting them in a high temperature environment have been put to practical use.

  The above-described solid oxide fuel cell includes a fuel cell stack that generates power using an oxidant gas and a reformed fuel gas, and a reformed fuel gas supplied to the fuel cell stack from pure water (steam) and fuel gas. Fuel cell power generation module having a fuel reformer to be generated and an off-gas combustion chamber for treating off-gas with an evaporator, various supply devices for supplying oxidant gas, fuel gas, pure water, and the like to the fuel cell power generation module A control unit for controlling the instrument is provided.

  By the way, in order to prevent the deterioration of the fuel cell stack when the power generation operation of the solid oxide fuel cell is stopped, a small amount of oxidant gas, fuel gas or pure water is used immediately after the power generation operation is stopped. Stop control is performed to reduce the temperature of the fuel cell power generation module while continuing the supply. However, in such stop control, it is necessary to supply fuel gas that does not contribute to power generation over a long period of time, so that there is a problem that fuel gas is wasted. Therefore, techniques for solving this problem are disclosed in various documents.

  For example, in the solid oxide fuel cell of Patent Document 1, when stopping the power generation operation, supply of fuel gas and extraction of electric power are stopped, and evaporation of pure water continues in the evaporator after the power generation operation is stopped. As described above, the pure water is intermittently supplied to the fuel cell stack, and the inside of the fuel cell stack is filled with water vapor, thereby suppressing the pressure drop on the fuel electrode side of the fuel cell stack and the oxidant gas. Has been disclosed.

JP 2013-225484 A

  In the solid oxide fuel cell of Patent Document 1, pure water supplied to the fuel cell power generation module generates water from a water supply source such as tap water through a filter. However, in a conventional solid oxide fuel cell, so-called water is produced in which condensed water is recovered by cooling water vapor contained in the exhaust gas from the fuel cell power generation module, and purified water is purified to produce pure water. Independent operation may be performed. In the case of a solid oxide fuel cell having this water self-sustaining operation function, consuming pure water for a long time after stopping power generation operation may cause water self-sustained operation to fail. There is a demand to suppress the consumption of pure water as much as possible.

  On the other hand, there are solid oxide fuel cells that can forcibly stop the supply of oxidant gas, fuel gas, pure water, etc. immediately after the power generation operation is stopped, but the temperature of the fuel cell power generation module is somewhat When the fuel cell stack is lowered, a pressure difference is generated between the inside of the fuel cell stack and the off-gas fuel chamber, and the oxidant gas remaining in the off-gas fuel chamber flows back into the fuel cell stack. There is a risk that the gas concentration distribution inside the stack is biased to generate local batteries and damage the fuel cell stack.

  An object of the present invention is to provide a solid oxide fuel cell that can prevent the fuel cell stack from being damaged while suppressing the consumption of fuel gas and pure water as much as possible when the power generation operation is stopped. It is.

  The solid oxide fuel cell according to claim 1 is a solid state in which a reformed fuel gas generated by steam reforming a fuel gas and an oxidant gas are supplied to a fuel cell stack of a fuel cell power generation module to perform a power generation operation. In the oxide fuel cell, when stopping the power generation operation in the fuel cell power generation module, the power extraction from the fuel cell power generation module is stopped, and the fuel gas and the oxidant gas to the fuel cell power generation module are When the supply of pure water for steam reforming is stopped, and then the temperature of the fuel cell power generation module falls below the first set temperature, the fuel gas, the oxidant gas, and the steam reforming It is characterized by comprising a power generation operation stop control means for supplying pure water intermittently at respective set amounts.

  The solid oxide fuel cell according to claim 2 is the invention according to claim 1, wherein the power generation operation stop control unit is configured to reduce the temperature of the fuel cell power generation module after a predetermined temperature drop after the temperature falls below a first set temperature. The fuel gas, the oxidant gas, and the pure water for steam reforming are supplied, respectively.

  According to a third aspect of the present invention, there is provided the solid oxide fuel cell according to the first or second aspect, wherein the first set temperature is such that the oxidant gas starts to flow backward into the fuel cell stack in the fuel cell power generation module. It is characterized in that it is a temperature at or near that temperature.

  The solid oxide fuel cell according to claim 4 is the invention according to any one of claims 1 to 3, wherein each set amount of the fuel gas and the pure water for steam reforming is the fuel cell power generation module. The inside of the fuel cell stack is set to be more than the amount that can be filled with the reformed fuel gas generated from the fuel gas and the pure water for steam reforming.

  According to the first aspect of the present invention, when stopping the power generation operation in the fuel cell power generation module, the power generation operation stop control means stops taking out the power from the fuel cell power generation module and supplies fuel to the fuel cell power generation module. When the supply of gas, oxidant gas and pure water for steam reforming is stopped and then the temperature of the fuel cell power generation module falls below the first set temperature, fuel gas, oxidant gas and steam reforming The pure water for use is supplied intermittently at each set amount.

  Therefore, by intermittently supplying the reformed fuel gas generated from the fuel gas and pure water inside the fuel cell stack of the fuel cell power generation module, compared with the continuous supply of fuel gas and pure water. Thus, while suppressing the consumption of fuel gas and pure water as much as possible, it is possible to prevent the local concentration of cells from being generated due to the bias in the gas concentration distribution inside the fuel cell stack, and to prevent damage to the fuel cell stack. be able to.

  In addition, after the temperature of the fuel cell power generation module becomes equal to or lower than the first set temperature, the reformed fuel gas flowing out from the fuel cell stack is supplied by simultaneously supplying the fuel gas and pure water and simultaneously supplying the oxidant gas. It can be diluted below the ignition limit concentration by oxidant gas.

  According to the second aspect of the invention, the power generation operation stop control means is provided for the fuel gas, the oxidant gas, and the steam reforming whenever the temperature of the fuel cell power generation module decreases by a predetermined temperature after the temperature falls below the first set temperature. Therefore, the fuel cell power generation module can be quickly cooled while suppressing the deviation of the gas concentration distribution inside the fuel cell stack.

  According to the invention of claim 3, the first set temperature is a temperature at which the back flow of the oxidant gas starts into the fuel cell stack in the fuel cell power generation module or a temperature in the vicinity thereof. By not supplying fuel gas or pure water, the consumption of fuel gas or pure water is reliably suppressed until the temperature drops below the first set temperature at which the gas concentration distribution inside the fuel cell stack starts to become uneven. be able to.

  According to the invention of claim 4, the set amount of each of the fuel gas and the pure water for steam reforming is such that the fuel gas and the pure water for steam reforming are disposed inside the fuel cell stack in the fuel cell power generation module. Is set to be more than the amount that can be filled with the reformed fuel gas generated from the fuel cell, so that the fuel cell stack can be reliably damaged by reliably preventing the backflow of the oxidant gas into the fuel cell stack. Can be prevented.

1 is a schematic configuration diagram of a solid oxide fuel cell according to an embodiment of the present invention. It is a schematic block diagram of a fuel cell power generation module. It is a control flowchart of power generation operation stop control. It is a diagram which shows the change with respect to time of the temperature of a fuel cell power generation module, and the total supply amount of fuel gas, a pure water, and oxidizing agent gas.

  Hereinafter, modes for carrying out the present invention will be described based on examples.

First, the overall configuration of the solid oxide fuel cell 1 will be described.
As shown in FIG. 1, a solid oxide fuel cell 1 includes a fuel cell power generation module 2, a reforming air supply device 3, a power generation air supply device 4, a fuel gas supply device 5, an exhaust heat recovery device 6, a pure air A water supply device 7, a power conditioner unit 8, a control unit 9, etc. are provided, and the DC power generated by the fuel cell power generation module 2 is converted to AC power via the power conditioner unit 8 and output to the outside. .

  As shown in FIG. 1, the solid oxide fuel cell 1 is configured by housing various instruments, various pipes, and the like in an outer case 11. Inside the outer case 11 is an upper power generation chamber 11A in which the fuel cell power generation module 2 is accommodated by a frame member 12, auxiliary equipment such as various supply devices 3 to 5, 7 and exhaust heat recovery device 6, and power condition. It is partitioned into a lower auxiliary machine chamber 11B in which the na unit 8, the control unit 9 and the like are housed.

  The solid oxide fuel cell 1 includes, for example, a hot water storage and hot water storage device that stores hot water after heat exchange by the heat exchanger of the exhaust heat recovery device 6, the hot water storage hot water supply device, and the solid oxide fuel cell 1. However, a fuel cell cogeneration system can be configured by combining with a heat recovery circuit for circulating hot water and the like, but detailed description of the configuration other than the solid oxide fuel cell 1 is omitted. .

Next, auxiliary machines such as various supply devices 3 to 5 and 7 and exhaust heat recovery device 6 will be described.
As shown in FIG. 2, the reforming air supply device 3 takes in fuel reforming air from the outside into the reforming air blower, and the taken-in air passes through the reforming air passage 13 to the fuel cell. The power generation air supply device 4 supplies the power to the evaporator 22 and the fuel reformer 23 of the power generation module 2, takes air from the outside into the power generation air blower, and uses the taken air as the oxidant gas to generate power. The air is supplied to the air heat exchanger 25 of the fuel cell power generation module 2 through the passage 14.

  The fuel gas supply device 5 takes fuel gas from a gas supply source (not shown) into a fuel booster blower, desulfurizes the boosted fuel gas through a desulfurizer, and passes the desulfurized fuel gas through the fuel gas supply passage 15. To the evaporator 22 and the fuel reformer 23 of the fuel cell power generation module 2.

  The exhaust heat recovery device 6 is provided in the middle of the exhaust passage 16 and uses the hot water flowing through the exhaust heat recovery circuit to remove exhaust heat from the exhaust gas discharged from the fuel cell power generation module 2 flowing through the exhaust passage 16. to recover. The pure water supply device 7 recovers the condensed water generated by cooling the exhaust gas by the exhaust heat recovery device 6, removes impurities from the condensed water, stores the pure water generated, and then passes through the pure water supply passage 17. This is supplied to the evaporator 22 and the fuel reformer 23 of the fuel cell power generation module 2.

  The power conditioner unit 8 is for converting the electric power generated by the fuel cell power generation unit 2. For example, the DC power generated by the fuel cell power generation module 2 can be used in a normal house. It converts into AC power of 100V, and outputs it to a distribution board via wiring. The control unit 9 is constituted by a microcomputer or the like, and receives signals from various sensors and executes operation control of various instruments.

Next, the fuel cell power generation module 2 will be described.
As shown in FIGS. 1 and 2, the fuel cell power generation module 2 is heated by the fuel cell stack 21, the evaporator 22 and the fuel reformer 23, the offgas combustion chamber 24, and the combustion gas in the offgas combustion chamber 24. It includes an air heat exchanger 25 and the like, and generates electricity by chemically reacting the reformed fuel gas and the oxidant gas reformed by the fuel reformer 23 in a high temperature environment in the fuel cell stack 21. is there.

  Various appliances of the fuel cell power generation module 2 are covered with a heat insulating material 26 made of gypsum board and housed in a rectangular parallelepiped case member 27 made of a thin steel plate. The arrangement structure of various instruments will be briefly described. As shown in FIG. 2, the evaporator 22, the fuel reformer 23, the air heat exchanger 25, and the like are arranged in the upper part inside the case member 27, and the fuel The battery cell stack 21 is disposed at the lower part.

  The fuel cell stack 21 is configured by arranging a plurality of fuel cells 21a. Each fuel battery cell 21a is formed in a cylindrical shape, and includes a solid electrolyte such as zirconia, an inner fuel electrode and an outer oxygen electrode provided so as to sandwich the solid electrolyte. The reformed fuel gas is supplied from the fuel reformer 23 through the manifold 28 to the fuel electrode side (inside each fuel cell 21 a) of the fuel cell stack 21, and the oxygen electrode side (of the fuel cell stack 21 ( The oxidant gas is supplied from the air heat exchanger 25 to the outside of each fuel battery cell 21a, and these are electrochemically reacted in a high temperature environment to generate DC power.

  The evaporator 22 generates water vapor for mixing with fuel gas from pure water and supplies it to the fuel reformer 23. The fuel reformer 23 has a reforming catalyst such as nickel or platinum, and mixes and reacts the desulfurized fuel gas and steam (with reforming air at start-up) (steam reforming, partial oxidation reforming). Etc.) to generate a reformed fuel gas, and this reformed fuel gas is supplied to the fuel electrode side of the fuel cell stack 21.

  The off-gas combustion chamber 24 is for burning the remaining fuel gas generated by the power generation of the fuel cell stack 21, and each discharge on the fuel electrode side and the oxygen electrode side of the fuel cell 21 a of the fuel cell stack 21. Connected with the side. In the off-gas combustion chamber 24, high-temperature exhaust gas is generated by burning the reaction fuel gas discharged from the fuel electrode side and the air containing oxygen discharged from the oxygen electrode side, and the fuel reforming is performed with the exhaust gas. After heating the mass device 23 and the like, it is discharged to the outside through the exhaust passage 16.

  The exhaust gas discharged from the fuel cell power generation module 2 is heat-exchanged with the hot water circulating in the exhaust heat recovery circuit in the heat exchanger of the exhaust heat recovery device 6 provided in the exhaust passage 16 to be heated. After being reduced, it is discharged outside. The water vapor contained in the exhaust gas is cooled by heat exchange and becomes condensed water.

Next, power generation operation stop control when the power generation operation of the fuel cell power generation module 2 related to the present invention is stopped will be described.
When stopping the power generation operation in the fuel cell power generation module 2, the control unit 9 stops taking out the power from the fuel cell power generation module 2, and also supplies the fuel gas, the oxidant gas, and the steam reforming to the fuel cell power generation module 2. The supply of quality pure water is stopped, and when the temperature of the fuel cell power generation module 2 falls below the first set temperature (for example, 400 ° C.), the fuel gas, the oxidant gas, and the steam reforming It is possible to execute power generation operation stop control for supplying pure water intermittently at each set amount.

  Further, the control unit 9 performs the fuel gas, the oxidant gas, and the pure water for steam reforming whenever the temperature of the fuel cell power generation module 2 decreases by a predetermined temperature (for example, 50 ° C.) after the temperature becomes equal to or lower than the first set temperature. , And when the temperature of the fuel cell power generation module 2 becomes equal to or lower than a second set temperature (for example, 100 ° C.), the power generation operation stop control for stopping the intermittent supply can be executed.

  As shown in FIG. 2, the module temperature sensor 31, which is one of various sensors that transmit a detection signal to the control unit 9, has a middle stage of one fuel cell 21 a among the plurality of fuel cells 21 a. Provided in the department. The module temperature sensor 31 detects the temperature of the fuel cell power generation module 2 and transmits it to the control unit 9. The mounting position of the module temperature sensor 31 can be changed as appropriate as long as the temperature of the fuel cell power generation module 2 can be detected.

  Next, the power generation operation stop control that is automatically executed by the control unit 9 when the power generation operation is stopped will be described based on the flowchart of FIG. 3. In the figure, the symbol Si (i = 1, 2,...) Indicates each step. This power generation operation stop control program is stored in the control unit 9 in advance. FIG. 4 illustrates a change in the temperature of the fuel cell power generation module 2 when the power generation operation stop control is executed. In FIG. 4, the total supply amount and the time interval of the fuel gas, the oxidant gas, and the pure water merely show a change tendency, and do not show specific values.

  In the flowchart of FIG. 3, when this control is started, first, in S1, it is determined whether or not a stop condition for power generation operation is satisfied based on a user operation, detection signals of various sensors, and the like. If the conditions for stopping the power generation operation are satisfied, the determination in S1 is Yes, the process proceeds to S2, and the determination returns in S1 if No.

  Next, when the power generation operation in the fuel cell power generation module 2 is stopped in S2, the power extraction from the fuel cell power generation module 2 is stopped, and the fuel gas, oxidant gas, and water vapor to the fuel cell power generation module 2 are stopped. The supply of the pure water for reforming is stopped, and the process proceeds to S3.

  Next, in S3, the control unit 9 reads the detection signal of the temperature sensor 31, calculates the temperature of the fuel cell power generation module 2 (temperature of the fuel cell stack 21) based on this detection signal, and proceeds to S4. Then, it is determined whether or not the temperature of the fuel cell power generation module 2 is equal to or lower than a first set temperature (for example, 400 ° C.). If the temperature of the fuel cell power generation module 2 is equal to or lower than the first set temperature, the determination in S4 is Yes. Then, the process proceeds to S5, and S3 and S4 are repeated when the determination of S4 is No.

  The first set temperature is a temperature at which the reverse flow of the oxidant gas starts into the fuel cell stack 21 in the fuel cell power generation module 2 or a temperature in the vicinity thereof. That is, immediately after the power generation operation is stopped, there is no pressure difference between the inside of the fuel cell stack 21 and the off-gas combustion chamber 24, and the oxidant gas and the fuel reformed gas are not diffused and the gas concentration distribution is stable. Below, the temperature of the fuel cell power generation module 2 gradually decreases.

  However, when the temperature of the fuel cell power generation module 2 decreases to some extent, a pressure difference is generated between the inside of the fuel cell stack 21 and the offgas combustion chamber 24, and the oxidant gas remaining in the offgas combustion chamber 24 is reduced. As a result of the diffusion, the back flow into the fuel cell stack 21 starts. The temperature at which the reverse flow of the oxidant gas is started (the temperature at which the oxidant gas is absorbed and diffused inside the fuel cell stack 21) depends on the capability of the fuel cell power generation module 2, so The calculated temperature is set as the first set temperature.

  Next, in S <b> 5, the control unit 9 controls the power generation air supply device 4, the fuel gas supply device 5, the pure water supply device 7, and the like, so that the fuel cell power generation module 2 is supplied with fuel gas, oxidant gas, and water vapor. The pure water for reforming is supplied at each set amount, and the process proceeds to S6.

  The set amount of each of the fuel gas and the pure water for steam reforming is the reforming amount generated from the fuel gas and the pure water for steam reforming inside the fuel cell cell tack 21 in the fuel cell power generation module 2. It is set to be more than the amount that can be filled with fuel gas.

  Specifically, the set amount of each of the fuel gas and the pure water for steam reforming is such that the amount of the reformed fuel gas generated therefrom is about 1.5 times the internal volume of the fuel cell stack 21. However, the value is not particularly limited to this value, and can be appropriately changed as long as the inside of the fuel cell stack 21 can be filled with the reformed fuel gas by one supply. Further, it is desirable that the set amount of the oxidant gas is set to such an amount that the reformed fuel gas becomes the ignition limit concentration or less when mixed with the reformed fuel gas flowing out from the inside of the fuel cell cell tack 21. .

  Next, the control unit 9 reads the detection signal of the temperature sensor 31, calculates the temperature of the fuel cell power generation module 2 (the temperature of the fuel cell stack 21) based on this detection signal, proceeds to S7, and proceeds to step S7. It is determined whether or not the temperature of the battery power generation module 2 has decreased by a predetermined temperature (for example, 50 ° C.). If the temperature of the fuel cell power generation module 2 has decreased by a predetermined temperature, the determination of S7 becomes Yes, and the process proceeds to S5. Then, S5 to S7 are repeated.

  That is, as shown in FIG. 4, the temperature of the fuel cell power generation module 2 is in a high temperature state of 700 ° C. or higher during the power generation operation, but gradually increases immediately after the power generation operation is stopped (time t1). When the temperature of the fuel cell power generation module 2 reaches the first set temperature (time t2), the fuel cell power generation module 2 is supplied with fuel gas, oxidant gas, and pure water for steam reforming, respectively. Supply in set amount.

  Thereafter, each time the temperature is lowered (time t3 to t8), fuel gas, oxidant gas, and pure water for steam reforming are supplied in respective set amounts. By doing so, fuel gas, oxidant gas, and pure water for steam reforming can be intermittently supplied to the fuel cell power generation module 2 due to a decrease in the predetermined temperature.

  For this reason, after the temperature of the fuel cell power generation module 2 drops to the first set temperature at time t2, the inside of the fuel cell stack 21 can be constantly filled with the reformed fuel gas. The interval at which the fuel gas, the oxidant gas and the pure water are supplied to the fuel cell power generation module 2 becomes longer as the temperature of the fuel cell power generation module 2 decreases, so that the total amount supplied to the fuel cell power generation module 2 is also increased. Decrease in hours.

  When the determination in S7 is No, the process proceeds to S8, where it is determined whether or not the temperature of the fuel cell power generation module 2 is lower than a second set temperature (for example, 100 ° C.), and the temperature of the fuel cell power generation module 2 is the second. If the temperature is lower than the set temperature, the determination in S8 is Yes, and this series of control is terminated. If the determination in S8 is No, the process proceeds to S6. In addition, after this series of control is completed, the inside of the fuel cell power generation module 2 is brought to room temperature while purging the remaining water vapor by supplying the oxidant gas and reforming air to the fuel cell power generation module 2. It may be cooled.

Next, the operation and effect of the solid oxide fuel cell 1 of the present invention will be described.
When stopping the power generation operation in the fuel cell power generation module 2, the control unit 9 (power generation operation stop control means) stops taking out the power from the fuel cell power generation module 2 and also supplies the fuel gas to the fuel cell power generation module 2. When the temperature of the fuel cell power generation module 2 becomes equal to or lower than the first set temperature, the fuel gas, the oxidant gas, and the steam reforming are stopped. The pure water for use is supplied intermittently at each set amount.

  Therefore, by continuously supplying the reformed fuel gas generated from the fuel gas and pure water into the fuel cell stack 21 of the fuel cell power generation module 2, the fuel gas and pure water are continuously supplied. In comparison with the fuel cell stack 21, the consumption of fuel gas and pure water can be suppressed as much as possible, and the concentration of gas inside the fuel cell stack 21 can be prevented from being biased to generate local batteries. Damage can be prevented.

  Further, after the temperature of the fuel cell power generation module 2 becomes equal to or lower than the first set temperature, the reformed fuel gas flowing out from the fuel cell stack 21 is supplied by supplying the fuel gas and pure water and simultaneously supplying the oxidant gas. Can be diluted to below the ignition limit concentration by oxidizing gas.

  Furthermore, the control unit 9 supplies fuel gas, oxidant gas, and pure water for steam reforming each time the temperature of the fuel cell power generation module 2 decreases by a predetermined temperature after the temperature becomes equal to or lower than the first set temperature. The fuel cell power generation module 2 can be quickly cooled while suppressing the deviation of the gas concentration distribution inside the fuel cell stack 21.

  Furthermore, since the first set temperature is a temperature at which the reverse flow of the oxidant gas starts into the fuel cell stack 21 in the fuel cell power generation module 2 or in the vicinity thereof, the temperature of the fuel cell power generation module 2 is the fuel. By not supplying the fuel gas or pure water until the gas concentration distribution inside the battery cell stack 21 is lowered below the first set temperature at which the bias begins to occur, consumption of the fuel gas or pure water can be reliably suppressed. it can.

  In addition, the respective set amounts of the fuel gas and the pure water for steam reforming are modified in the fuel cell stack 21 in the fuel cell power generation module 2 to be generated from the fuel gas and the pure water for steam reforming. Since it is set to be more than the amount that can be filled with the quality fuel gas, it is possible to reliably prevent the fuel cell stack 21 from being damaged by reliably preventing the backflow of the internal oxidant gas in the fuel cell stack 21. .

Next, a mode in which the above embodiment is partially changed will be described.
[1] In the power generation operation stop control according to the above embodiment, the first set temperature is set to a temperature at which the reverse flow of the oxidant gas starts into the fuel cell stack 21 in the fuel cell power generation module 2 or a temperature in the vicinity thereof. However, it is not necessary to limit to this temperature in particular, and the first set temperature is set to a reusable limit temperature (limit temperature at which ignition is possible) that does not require start-up operation at the time of startup of the fuel cell power generation module 2. May be set.

[2] In the power generation operation stop control according to the above embodiment, fuel gas, oxidant gas and pure water are intermittently supplied to the fuel cell power generation module 2 due to a decrease in the predetermined temperature. It is not necessary to limit, and after the temperature of the fuel cell power generation module 2 becomes equal to or lower than the first set temperature, the fuel gas, the oxidant gas, and the pure water may be intermittently supplied due to the elapse of the set time. .

[3] In the power generation operation stop control of the above-described embodiment, the values of the first and second set temperatures and the predetermined temperature are merely examples, and can be appropriately changed according to the capability of the fuel cell power generation module 2 and the like. It is.

[4] In addition, those skilled in the art can implement the present invention by adding various modifications without departing from the spirit of the present invention, and the present invention includes such modifications. It is.

DESCRIPTION OF SYMBOLS 1 Solid oxide fuel cell 2 Fuel cell power generation module 9 Control unit 21 Fuel cell stack

Claims (4)

In the solid oxide fuel cell that performs the power generation operation by supplying the reformed fuel gas generated by steam reforming the fuel gas and the oxidant gas to the fuel cell stack of the fuel cell power generation module,
When stopping the power generation operation in the fuel cell power generation module, power extraction from the fuel cell power generation module is stopped, and fuel gas, oxidant gas, and pure water for steam reforming to the fuel cell power generation module are stopped. Then, when the temperature of the fuel cell power generation module becomes equal to or lower than the first set temperature, the fuel gas, the oxidant gas, and the pure water for steam reforming are respectively set in amounts. And a power generation operation stop control means for intermittently supplying the solid oxide fuel cell.   The power generation operation stop control means supplies the fuel gas, the oxidant gas, and the pure water for steam reforming each time the temperature of the fuel cell power generation module decreases by a predetermined temperature after the temperature falls below the first set temperature. The solid oxide fuel cell according to claim 1, wherein each is supplied.   3. The first set temperature according to claim 1, wherein the first set temperature is a temperature at which the back flow of the oxidant gas starts into the fuel cell stack in the fuel cell power generation module or a temperature in the vicinity thereof. Solid oxide fuel cell.   Each set amount of the fuel gas and the pure water for steam reforming is generated from the fuel gas and the pure water for steam reforming inside the fuel cell cell tack in the fuel cell power generation module. The solid oxide fuel cell according to any one of claims 1 to 3, wherein the solid oxide fuel cell is set to an amount that can be filled with the reformed fuel gas.