JP2010027443A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system in which a bypass passage and a bypass valve for opening and closing the bypass passage can be eliminated. <P>SOLUTION: The system includes an anode gas channel 76 for feeding an anode gas to an anode of a fuel cell 1, a CO-reducing potion 77 for reducing the concentration of CO contained in the anode gas, a cathode gas channel 80 for feeding a cathode gas to a cathode, an inlet opening/closing portion 85 for opening and closing the inlet side of the cathode, and an exit opening/closing portion 87 for opening and closing the exit side of the cathode. At the time of starting the system, a control portion 5 carries out primary control for feeding the anode gas to the anode while closing the inlet opening/closing portion 85 and the exit opening/closing portion 87, and then carries out secondary control for feeding the cathode gas to the cathode in accordance with the power generation amount of the fuel cell while feeding the anode gas to the anode. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fuel cell system.

  The fuel cell system is a fuel cell having an anode and a cathode, an anode gas passage for supplying anode gas from the reformer to the anode of the fuel cell, and a reformer provided upstream of the anode of the fuel cell. A CO reduction section for reducing the CO (carbon monoxide) concentration contained in the anode gas, a cathode gas passage for supplying a cathode gas containing oxygen to the cathode of the fuel cell, and an inlet side of the fuel cell cathode being opened and closed An opening / closing portion for opening / closing, an outlet opening / closing portion for opening / closing the outlet side of the cathode of the fuel cell, and a control portion for controlling the inlet opening / closing portion and the outlet opening / closing portion.

At the start of the operation of the fuel cell system, the composition of the anode gas generated by the reformer is not always sufficiently stable, and the anode gas may contain CO exceeding a predetermined concentration. It is not preferable to supply the anode gas containing CO to the anode of the fuel cell that is operating for power generation. This is because when the fuel cell is in a power generation operation, the catalyst held on the anode deteriorates due to CO poisoning. Thus, a bypass system is provided in the conventional system (Patent Document 1). When the composition of the anode gas produced by the reformer is not always stable at the start of system operation, the anode of the fuel cell is bypassed by flowing the anode gas through the bypass passage, We do not let you supply. This suppresses deterioration of the anode catalyst of the fuel cell due to CO poisoning. The bypass path described above requires a bypass valve that closes the bypass path so that the anode gas does not flow through the bypass path during normal operation of the system.
JP 2005-174745 A

  The technique according to Patent Document 1 described above suppresses deterioration of the anode catalyst of the fuel cell during power generation due to CO poisoning, but the anode gas bypasses the anode of the fuel cell when the system is started. A bypass path that flows and a bypass valve that opens and closes the bypass path are required.

  The present invention has been made in view of the above circumstances, and provides a fuel cell system capable of eliminating a bypass passage for the anode gas to bypass the anode of the fuel cell and a bypass valve for opening and closing the bypass passage. The task is to do.

(1) A fuel cell system according to aspect 1 includes a fuel cell having an anode and a cathode, an anode gas passage for supplying an anode gas that may contain CO to the anode of the fuel cell, and an anode of the fuel cell. A CO reduction unit that is provided upstream to reduce the concentration of CO contained in the anode gas, a cathode gas passage for supplying a cathode gas containing oxygen to the cathode of the fuel cell, and an inlet side of the cathode of the fuel cell A fuel cell system comprising: an inlet opening and closing part; an outlet opening and closing part for opening and closing an outlet side of the cathode of the fuel cell; and a control part for controlling at least the inlet opening and closing part and the outlet opening and closing part.
At the start of operation of the fuel cell system, the control unit (i) supplies the anode gas to the anode of the fuel cell with the inlet opening / closing unit and the outlet opening / closing unit closed and the fuel cell cathode sealed. (Ii) After that, with the inlet opening / closing part and the outlet opening / closing part being opened, the anode gas is supplied to the anode of the fuel cell, and the cathode gas is fueled according to the power generation amount of the fuel cell. A second control for supplying the cathode of the battery is performed.

  As described above, at the start of operation of a fuel cell system (hereinafter also referred to as a system), the control unit supplies anode gas to the anode of the fuel cell. However, the inlet opening / closing part and the outlet opening / closing part of the cathode are closed, and the cathode is sealed. Therefore, at the time of starting the system, the anode gas is supplied to the anode of the fuel cell without bypassing the anode of the fuel cell. Therefore, there is an advantage that the bypass passage and the bypass valve that are conventionally required for bypassing the anode of the fuel cell can be eliminated, and the complication of the piping is suppressed.

Here, considering that water (2H ₂ + O ₂ → 2H ₂ O) is generated by a power generation reaction in the fuel cell, 2 moles of H ₂ and 1 mole of O ₂ are stoichiometrically equivalent. I can say that. As described above, at the start-up of the system, the anode gas is positively supplied to the anode while the cathode is sealed and the supply of the cathode gas to the cathode is restricted. For this reason, compared with the number of moles of anode active material (hydrogen) supplied to the anode, the number of moles of cathode active material (oxygen) at the cathode is stoichiometrically reduced or depleted. Therefore, in the first control, according to the molar ratio, the molar ratio of O ₂ is less than 1 with respect to the molar ratio 2 of H ₂ . That is, when the system is started, the cathode is maintained in an oxygen-reduced state such as an oxygen-deficient state. Here, the oxygen reduction state means that the number of moles of oxygen as the cathode active material in the cathode is stoichiometrically reduced or lacked compared to the number of moles of the anode active material (hydrogen) supplied to the anode. Means state.

  As described above, according to this aspect, since the oxygen at the cathode is stoichiometrically in an oxygen-reduced state such as an oxygen-deficient state at the time of starting the system, the increase in the cathode potential is limited and the OCV is excessively excessive. The rise is suppressed.

  The open circuit voltage (hereinafter also referred to as OCV) is an open circuit voltage in which the anode and cathode of the fuel cell are not electrically connected (the fuel cell and the power load are not electrically connected). ) Is the voltage difference between both terminals of the fuel cell. The OCV has a higher voltage than a normal power generation voltage generated by the fuel cell in a state where the anode and the cathode of the fuel cell are electrically connected via a power load. When the fuel cell potential rises excessively above the equilibrium electrode potential of the catalyst, the fuel cell catalyst (especially the cathode catalyst) proceeds with an oxidation reaction between oxygen and hydrogen that permeates the electrolyte from the anode to the cathode, There is a possibility that the catalyst of the fuel cell (particularly the catalyst of the cathode) is electrochemically deteriorated. For this reason, it is preferable to avoid that OCV rises excessively as much as possible.

  Further, when the fuel cell is generating electric power, when the anode gas containing CO is supplied to the anode of the fuel cell, the CO poisoning of the anode catalyst cannot be ignored. However, as long as the power generation of the fuel cell is restricted, even if an anode gas containing CO is supplied to the anode of the fuel cell, the reversibility of the CO poisoning of the catalyst of the anode of the fuel cell increases, The CO poisoning of the catalyst is suppressed.

  Furthermore, even when an anode gas containing CO in addition to the anode active material is positively supplied to the anode of the fuel cell at the time of starting the system, oxygen at the cathode is in an oxygen-reduced state such as an oxygen-deficient state. Therefore, the power generation reaction of the fuel cell is limited. As a result, there is an advantage that CO poisoning of the catalyst at the anode of the fuel cell is suppressed.

  According to the present specification, the cathode of the fuel cell is the oxidant electrode and the anode is the fuel electrode. The anode gas is a gas supplied to the anode. The cathode gas is a gas supplied to the cathode. The inlet opening / closing portion is an element for opening and closing the inlet side of the cathode of the fuel cell, and may be provided in the fuel cell itself, such as a valve, or provided in a passage leading to the cathode inlet of the fuel cell. It may be done. The outlet opening / closing unit is an element for opening and closing the outlet side of the cathode of the fuel cell, and includes a valve and the like, and may be provided in the fuel cell itself or provided in a passage connected to the outlet of the cathode of the fuel cell. May be. The CO reduction unit is an element that is provided upstream of the anode of the fuel cell and reduces the concentration of CO contained in the anode gas generated by the reformer. The CO reduction unit can be formed of at least one of a CO shift unit, a CO oxidation unit, and a methanation reaction unit, and in short, it only needs to have a function of reducing the CO concentration.

  The aspect 1 can employ at least one of the following preferred embodiments.

It is preferable that a reforming device for generating an anode gas to be supplied to the anode of the fuel cell from the reforming fuel by a reforming reaction is provided upstream of the CO reduction unit as an anode gas supply source. When a large number of fuel cell systems are provided, the reformer may be shared. Preferably, the reformer includes a burner for combusting combustion fuel with combustion air, and a reforming section that is heated by the burner so as to be suitable for a reforming reaction to generate anode gas. A storage unit such as a tank for storing anode gas to be supplied to the anode of the fuel cell may be provided upstream of the CO reduction unit as an anode gas supply source.
-At the time of starting the system, the CO reduction action is not sufficient because the temperature of the CO reduction part is relatively low before the completion of warming up of the CO reduction part. In this case, the concentration of CO contained in the anode gas supplied to the anode of the fuel cell may increase, and the risk of CO poisoning of the catalyst at the anode increases. On the other hand, after the warm-up of the CO reduction unit is completed, the CO reduction effect is good because the temperature of the CO reduction unit is relatively high. In this case, the CO concentration contained in the anode gas supplied to the anode of the fuel cell becomes relatively low, and the risk of CO poisoning of the catalyst at the anode is reduced. Therefore, preferably, the control unit executes the first control before the completion of warming-up of the CO reduction unit, and performs the second control after completion of warming-up of the CO reduction unit while limiting the power generation reaction of the fuel cell. And promote the power generation reaction of the stack. As a result, in the first control, the risk of CO poisoning of the catalyst at the anode is reduced.

  Preferably, in the first control, the control unit discharges the anode gas supplied to the anode inlet of the fuel cell from the anode outlet of the fuel cell, and then supplies the anode gas to the burner via the anode off-gas passage. Can be burned with combustion air. When the system is started, the composition of the anode gas produced by the reformer is not necessarily stable, and the concentration of CO contained in the anode gas may be high. Therefore, in the first control, the control unit causes the anode gas to be supplied to the anode inlet of the fuel cell (oxygen-reduced state such as an oxygen-deficient state at the cathode), but after discharging it from the anode outlet of the fuel cell, Anode gas can be supplied to the burner via the anode off-gas passage and burned with combustion air in the burner. In the first control, as described above, the cathode of the fuel cell is in an oxygen-reduced state such as an oxygen-deficient state, the power generation reaction of the fuel cell is limited, and CO poisoning of the anode catalyst is suppressed. .

  Preferably, the outlet opening / closing part can be a check valve provided on the outlet side of the cathode of the fuel cell. In this case, the check valve causes the cathode off-gas discharged from the cathode of the fuel cell to flow in the direction of being discharged from the cathode, and prevents the reverse flow. Therefore, the outside air containing oxygen can be prevented from entering the cathode of the fuel cell from the outlet opening / closing part. As a result, it is possible to prevent outside air from entering the cathode of the fuel cell between the time when the system is stopped and the time when the system is next started. Therefore, the cathode tends to be maintained in a state where oxygen is reduced or depleted. Therefore, at the next start-up, the cathode is easily maintained in an oxygen-reduced state such as an oxygen-deficient state. The oxygen reduced state means a state in which the oxygen concentration is lower than the oxygen concentration inherent in the cathode gas.

  -Preferably, the cathode gas conveyance source which supplies cathode gas to the cathode of a fuel cell is provided in the inlet side of the cathode of a fuel cell, and an inlet opening / closing part can be provided in the cathode gas conveyance source. As a result, it is possible to prevent the outside air containing oxygen from entering the cathode of the fuel cell from the inlet opening / closing section from the time when the system is stopped until the next startup. As a result, when the system is started, the inside of the cathode of the fuel cell is easily maintained in a state where oxygen is reduced or eliminated. Here, examples of the cathode gas transfer source include a pump, a fan, a blower, and a compressor.

  -When the system is shut down, when anode gas is present at the anode of the fuel cell and cathode gas is present at the cathode, if the anode and cathode of the fuel cell are not electrically connected, There is a possibility that the open circuit voltage (hereinafter also referred to as OCV) rises excessively beyond a predetermined value. Therefore, in the first control, when the OCV of the fuel cell rises above a predetermined value, the cathode gas is present at the cathode, and the anode gas is supplied with a sufficiently low CO concentration (for example, 10 ppm or less in PEFC). In addition, in a state where the fuel cell and the power consumption unit are electrically connected, it is preferable that the power generated in the fuel cell is consumed by the power consumption unit. In this case, an excessive increase in the OCV of the fuel cell is suppressed. Furthermore, the oxygen concentration inside the cathode is reduced more than before power consumption due to the power generation reaction of the fuel cell during power consumption. As a result, an oxygen reduced state is formed at the cathode. Thus, in the first control, it is possible to form an oxygen reduced state such as an oxygen deficient state at the cathode. The predetermined voltage value serving as the reference can be appropriately set according to the system, the material of the fuel cell catalyst, and the like.

  Preferably, when the operation of the fuel cell system is stopped, the control unit (i) closes the outlet opening / closing unit of the fuel cell cathode and opens the inlet opening / closing unit, and the inside of the fuel cell cathode is large. Control of supplying a cathode gas containing oxygen to the cathode so as to have a high pressure exceeding atmospheric pressure, and (ii) after that, the inlet opening / closing part is closed while the outlet opening / closing part is closed. (Iii) After that, the cathode gas is present at the cathode of the fuel cell, the anode gas is supplied to the anode, and the fuel cell and the power consuming unit are electrically connected to each other. In the connected state, the power generated in the fuel cell is consumed by the power consuming unit. Thus, the control unit performs control to reduce the oxygen concentration inside the cathode more than before power consumption while suppressing an excessive increase in the OCV of the fuel cell. In this case, oxygen remaining inside the cathode is consumed and reduced by a power generation reaction during power consumption. For this reason, if the cathode gas is air, the concentration of the inert nitrogen gas increases at the cathode. Accordingly, the cathode of the fuel cell is sealed until the next start-up of the system with the inert nitrogen gas sealed.

  Here, it is preferable that an inert nitrogen gas having a pressure exceeding the atmospheric pressure on the high pressure side is sealed inside the cathode of the fuel cell. In this case, since the internal pressure of the cathode is higher than the atmospheric pressure, the outside air containing oxygen is effectively suppressed from entering the cathode of the fuel cell, and the oxygen reduction state of the cathode is maintained well until the next start-up. Is done.

  Here, according to the present specification, the power consuming unit refers to an element capable of consuming the power generated in the fuel cell, and a discharge load provided separately from the power load driven by the power generated by the fuel cell, or , Heaters, system accessories, or power storage units such as capacitors and storage batteries. Examples of the auxiliary machines include a passage opening / closing unit such as a valve, a fluid conveyance source such as a fan, a pump, a blower, and a compressor.

(2) A fuel cell system according to aspect 2 includes a fuel cell having an anode and a cathode, an anode gas passage for supplying an anode gas that may contain CO to the anode of the fuel cell, and an anode of the fuel cell. A CO reduction unit that is provided upstream to reduce the concentration of CO contained in the anode gas, a cathode gas passage for supplying a cathode gas containing oxygen to the cathode of the fuel cell, and an inlet side of the cathode of the fuel cell A fuel cell system comprising: an inlet opening and closing part; an outlet opening and closing part for opening and closing an outlet side of the cathode of the fuel cell; and a control part for controlling at least the inlet opening and closing part and the outlet opening and closing part.
When the operation of the fuel cell system is stopped, the control unit closes the inlet opening / closing unit and the outlet opening / closing unit of the cathode of the fuel cell to seal the cathode, and the cathode gas exists in the cathode of the fuel cell, and When the anode gas is supplied to the anode and the fuel cell and the power consuming unit are electrically connected, the power consumption of the fuel cell is consumed by the power consuming unit. Control is performed to reduce the oxygen concentration inside the cathode more than before power consumption, while suppressing an excessive rise.

  According to this aspect, when the operation of the system is stopped, the inside of the cathode of the fuel cell is brought into a state in which oxygen is reduced or depleted by a power generation reaction during power consumption. Then, until the next power generation operation of the system, the inside of the cathode is maintained in a state where oxygen is reduced or eliminated. As a result, the power generation reaction of the fuel cell is suppressed even when the anode gas is positively supplied to the anode of the fuel cell when the system is next started. As a result, when the anode and cathode of the fuel cell are not electrically connected, an excessive increase in OCV is reduced. In addition, when the anode and cathode of the fuel cell are electrically connected, CO poisoning of the catalyst held on the anode of the fuel cell is suppressed.

(3) A fuel cell system according to aspect 3 includes a fuel cell having an anode and a cathode, an anode gas passage for supplying an anode gas that may contain CO to the anode of the fuel cell, and an anode of the fuel cell. A CO reduction unit that is provided upstream to reduce the concentration of CO contained in the anode gas, a cathode gas passage for supplying a cathode gas containing oxygen to the cathode of the fuel cell, and an inlet side of the cathode of the fuel cell A fuel cell system comprising: an inlet opening / closing portion; an outlet opening / closing portion for opening / closing an outlet side of a cathode of the fuel cell; and a control portion for controlling at least the inlet opening / closing portion and the outlet opening / closing portion. When the operation of
(I) In the state where the outlet opening / closing part of the cathode of the fuel cell is closed and the inlet opening / closing part is opened, the control unit applies the pressure to the cathode so that the pressure inside the cathode of the fuel cell exceeds the atmospheric pressure to the high pressure side. Control for supplying the cathode gas, and (iii) control for bringing the inside of the cathode to a high pressure exceeding atmospheric pressure by closing the inlet opening / closing portion in a state in which the outlet opening / closing portion is closed, and (iii) after that, In a state where the cathode gas exists in the cathode and the anode gas is supplied to the anode, the fuel cell and the power consuming unit are electrically connected, and the power generated in the fuel cell is consumed by the power consuming unit. Control is performed to reduce the oxygen concentration inside the cathode from before the power consumption while suppressing an excessive increase in the open circuit voltage (OCV) of the fuel cell.

  According to this aspect, when the operation of the fuel cell system is stopped, the oxygen remaining inside the cathode of the fuel cell is consumed by the power generation reaction at the time of power consumption, so the oxygen concentration of the cathode is relatively low. Become. Therefore, the cathode of the fuel cell is maintained in the oxygen-reduced state until the next power generation operation of the system. For this reason, the deterioration of the cathode catalyst due to oxygen is suppressed.

  Here, after the control to reduce the oxygen concentration inside the cathode of the fuel cell as compared with before power consumption as described above, the inside of the cathode of the fuel cell is nitrogen having a pressure exceeding the atmospheric pressure to the high pressure side. It is preferable to enclose gas. In this case, the cathode pressure is higher than atmospheric pressure. For this reason, it is possible to effectively suppress the outside air containing oxygen from entering the cathode of the fuel cell. Furthermore, it is possible to use inexpensive ones having low sealing properties for the inlet opening / closing portion and the outlet opening / closing portion. Of course, it is also possible to use an expensive one having high sealing performance.

  According to the present invention, in the first control at the time of starting the system, the anode gas is supplied to the fuel cell in a state where the inlet opening / closing portion and the outlet opening / closing portion of the fuel cell cathode are closed and the cathode of the fuel cell is sealed. Supplied to the anode. As described above, in the first control, since the anode gas is supplied to the anode of the fuel cell, the bypass passage for bypassing the anode of the fuel cell and the bypass valve for opening and closing the bypass passage can be eliminated.

  Further, in the first control at the time of starting the system, the anode gas is actively supplied to the anode of the fuel cell, but the cathode is maintained in a sealed state, so that the power generation reaction of the fuel cell is limited. The Therefore, CO poisoning of the anode catalyst is suppressed, and the durability of the catalyst is improved.

(Embodiment 1)
Hereinafter, Embodiment 1 of the present invention will be described with reference to FIGS. 1 and 2.

(overall structure)
In FIG. 1, a fuel cell system (hereinafter also simply referred to as a system) 100 is for stationary installation in a general household, a business store, a building, or the like, and a fuel cell stack 1 having a cooling passage through which a coolant flows. The main cooling circuit 2 that cools the stack 1 by flowing the coolant through the cooling passage 10 of the stack 1 and the package 6 (housing) having the accommodation chamber 60 that accommodates them. The membrane electrode assembly of the stack 1 is an ion conductive membrane sandwiched between an anode (fuel electrode) and a cathode (oxidant electrode) (for example, a solid polymer type such as a fluorocarbon type or a hydrocarbon type, or an inorganic material type) Electrolyte sheet) and may be a sheet type or a tube type. The anode has a catalyst. The cathode has a catalyst. The catalyst can be a noble metal such as platinum.

  As shown in FIG. 2, the stack 1 is connected to a discharge load 54 (power consumption unit) via a switching element 53 such as a semiconductor switch. The stack 1 is connected to a power load 57 (home power load) via an inverter 55 and a breaker 56 (switching unit). The power load 57 is operated by the power of the stack 1 or the power of the commercial power source 58. Instead of the player 56, a relay may be used.

  According to the present embodiment, as shown in FIG. 1, the outlet temperature sensor 21, the heater 29, the first heat exchanger 22, the first heat exchanger 22, the outlet 10 p to the inlet 10 i of the cooling passage 10 of the stack 1 in the main cooling circuit 2. One pump 23 (first transport source), an anode condenser 24, and an inlet temperature sensor 20 are provided in series. The heater 29 warms the coolant when the temperature of the coolant flowing through the main cooling circuit 2 is excessively low, such as when the stack 1 is started. During steady operation of the stack 1, the heater 29 is basically turned off.

  When the first pump 23 is actuated, the cooling water of the main cooling circuit 2 receives heat at the anode condenser 24, passes through the inlet temperature sensor 20, flows from the inlet 10 i of the stack 1 to the cooling passage 10, and receives heat from the stack 1, It is discharged from the outlet 10p through the cooling passage 10, and further flows through the temperature sensor 21, the heater 29, and the first heat exchanger 22 in this order. For this reason, the heat generated when the stack 1 generates power is recovered in the cooling water of the main cooling circuit 2. Further, the heat of the anode gas generated in the reformer 70 is recovered in the cooling water of the main cooling circuit 2 through the anode condenser 24. The cooling water for the main cooling circuit 2 is a liquid having a low electrical conductivity.

  The anode gas supply system 7 that supplies anode gas (for example, fuel such as hydrogen-containing gas) to the anode that is the fuel electrode of the stack 1 will be described. The anode gas supply system 7 includes a reformer 70 having a reforming unit 70a and a burner 71 that heats the reforming unit 70a so as to be suitable for the reforming reaction, and an air pump 72 that supplies combustion air to the burner 71 ( A combustion air carrier source), a fuel pump 73 (fuel carrier source) that supplies fuel (hydrocarbon gas such as natural gas) to the reforming unit 70a and the burner 71, and a reforming unit 70 to reform the evaporation unit An anode gas passage that connects a water pump 74 (reformed water transport source) that supplies water (pure water), the outlet 70p of the reformer 70, and the anode inlet of the stack 1 via the anode condenser 24 and the anode inlet valve 75. 76 (fuel passage).

Here, the anode gas generated by the reformer 70 is supplied to the anode (fuel electrode) of the stack 1 through the anode gas passage 76. A CO reduction unit 77 is provided on the outlet side of the reformer 70. The CO reduction unit 77 includes a CO shift unit 78 having a catalyst that promotes a shift reaction that reduces the concentration of CO contained in the anode gas generated by the reformer 70 by the shift reaction of Formula (1); The CO gas contained in the anode gas that has passed through the shift unit 78 is oxidized by the equation (2) to form a CO oxidation unit 79 having a catalyst that promotes an oxidation reaction that further reduces the CO concentration. CO is not preferred because it affects the performance of the stack 1 catalyst. A temperature sensor 78t that detects the temperature of the CO shift unit 78 is provided. A temperature sensor 79 t that detects the temperature of the CO oxidation unit 79 is provided.
Formula (1): CO + H ₂ O → H ₂ + CO ₂ (exothermic reaction)
Formula (2): CO + 1 / 2O ₂ → CO ₂ (exothermic reaction)
A cathode gas supply system 8 that supplies a cathode gas (for example, an oxidant gas such as an oxygen-containing gas such as air) to the cathode that is the oxidant electrode of the stack 1 will be described. The cathode gas supply system 8 includes a cathode gas passage 80 (oxidant passage) connected to the cathode inlet of the stack 1, a pump 81 (cathode gas conveyance source) provided in the cathode gas passage 80, and a humidifier 82. The humidifier 82 includes a humidification path 82a, a moisture absorption path 82b, and a moisture holding member 82c that partitions the humidification path 82a and the moisture absorption path 82b. When the pump 81 is operated, the cathode gas is humidified by the humidification path 82 a of the humidifier 82 and then supplied to the cathode (oxidant electrode) of the stack 1.

  As shown in FIG. 1, a cathode inlet valve 85 (cathode inlet opening / closing portion) for opening and closing the cathode inlet side of the stack 1 is provided in the cathode gas passage 80. A cathode outlet valve 87 (cathode outlet opening / closing part) for opening and closing the cathode outlet side of the stack 1 is provided in the cathode offgas passage 96.

  The anode off gas discharge system 90 will be described. The off gas means the surplus gas remaining in the stack 1 without being used for the power generation reaction. As shown in FIG. 1, the anode offgas discharge system 90 includes an anode offgas passage 91 that connects the anode outlet of the anode of the stack 1 and the burner 71, an anode outlet valve 92 provided in the anode offgas passage 91, and an anode offgas passage. And an anode off-gas condenser 93 provided at 91. Here, since the anode off-gas discharged from the anode outlet of the stack 1 contains a combustible component, the moisture is reduced by the moisture absorption path 82b and the anode off-gas condenser 93, and then supplied to the burner 71 and burned.

  The cathode offgas discharge system 95 will be described. As shown in FIG. 1, the cathode gas discharge system 95 is provided in the cathode offgas passage 96 and the cathode offgas passage 96 through which the cathode offgas discharged from the cathode outlet of the stack 1 flows through the moisture absorption passage 82 b of the humidifier 82. A cathode off-gas condenser 97. Here, the cathode off-gas discharged from the cathode outlet of the stack 1 is further exhausted by the moisture absorption path 82b of the humidifier 82 and the cathode off-gas condenser 97 to be exhausted.

  As shown in FIG. 1, the exhaust heat recovery system 120 includes a second pump 122 (water conveyance source), an anode offgas condenser 93, a cathode offgas condenser 97, a combustion exhaust heat exchanger 125, and a second heat exchanger 127. A circulation circuit 128 that circulates is provided. When the second pump 122 is activated, cooling water (refrigerant) circulates in the circulation circuit 128, and the heat of the anode offgas condenser 93, the cathode offgas condenser 97, and the combustion exhaust heat exchanger 125 is recovered. Thereby, the cooling water flowing through the circulation circuit 128 is heated.

  The hot water storage system 130 will be described. As shown in FIG. 1, the hot water storage system 130 is sequentially arranged in the hot water storage tank 131 for storing hot water, the hot water storage circuit 132 that connects the discharge port of the hot water storage tank 131 and the suction port of the hot water storage tank 131, and the hot water storage circuit 132. It has the 3rd pump 133 (water conveyance source), the 2nd heat exchanger 127, and the 1st heat exchanger 22. When the third pump 133 is activated, the water flowing through the hot water storage circuit 132 is heated via the second heat exchanger 127 and the first heat exchanger 22. That is, the heat recovered by the exhaust heat recovery system 120 is recovered as hot water in the hot water storage circuit 132 by the second heat exchanger 127. The heat recovered in the main cooling circuit 2 is recovered as hot water in the hot water storage circuit 132 by the first heat exchanger 22. The control unit 5 outputs control signals for controlling the pumps 23, 122, 133, 81, 72, 73, 74, valves 75, 92, 85, 87, 102, and the heater 29, respectively.

During power generation operation, with the anode and cathode of the stack 1 being electrically connected via an electrical path, an anode gas containing hydrogen is supplied to the anode and a cathode gas containing oxygen is supplied to the cathode as follows. Power generation reaction occurs. Electrons (e ⁻ ) generated by the power generation reaction at the anode flow to the cathode through the power path and contribute to the cathode reaction. The cathode reaction produces water.
Anode power generation reaction ... H ₂ → 2H ⁺ + 2e ⁻
Cathode power generation reaction 2H ⁺ + 1 / 2O ₂ + 2e ⁻ → H ₂ O
(Part explanation)
Now, the main part of this embodiment will be described. First, a description will be given of the start of system operation. Before the start of system operation, the cathode inlet valve 85 and the cathode outlet valve 87 are closed, and the cathode of the stack 1 is sealed. Similarly, the anode inlet valve 75 and the anode outlet valve 92 are closed, and the anode of the stack 1 is sealed.

  At the start of operation of the system, the control unit 5 operates the air pump 72 to supply combustion air to the burner 71 with the cathode inlet valve 85 and the cathode outlet valve 87 closed, and the anode inlet valve 75 and The anode outlet valve 92 is opened. Next, the fuel pump 73 is operated to supply the gaseous reforming fuel to the reforming device 70 and the gaseous combustion fuel (the same as the reforming fuel) to the burner 71. As a result, the fuel supplied to the burner 71 burns and the reformer 70 is heated to a high temperature so as to be suitable for the reforming reaction. Thereafter, the control unit 5 operates the water pump 74 to supply the reforming water to the reforming device 70. As a result, in the reformer 70, the hydrocarbon-based reforming fuel is steam reformed. Therefore, an anode gas containing hydrogen as a main component is generated in the reformer 70. Here, the anode inlet valve 75 and the anode outlet valve 92 are opened. For this reason, the anode gas is positively supplied to the anode of the stack 1. At this time, the cathode inlet valve 85 and the cathode outlet valve 87 are closed, and the cathode is sealed. For this reason, at start-up, the molar ratio of oxygen present at the cathode of the stack 1 is stoichiometrically much smaller than the molar ratio of hydrogen continuously supplied to the anode of the stack 1.

  As described above, at the start of operation of the fuel cell system, the control unit 5 performs the first control, and supplies the anode gas to the anode of the stack 1. However, when the system is started, the composition of the anode gas is not necessarily stable and the CO concentration may be high. Therefore, it is not preferable to generate the power generation reaction by supplying the anode gas to the anode of the stack 1.

  Therefore, according to the present embodiment, the anode gas is positively supplied to the anode of the stack 1 in the first control at the time of starting the system, but the cathode inlet valve 85 and the cathode outlet valve 87 of the cathode of the stack 1 are closed. The cathode is sealed. As a result, in the first control, the number of moles of oxygen inside the cathode of the stack 1 is significantly reduced stoichiometrically compared to the number of moles of hydrogen supplied continuously to the anode of the stack 1. Or it is made deficient. As a result, the power generation reaction in the stack 1 is suppressed in the first control. Therefore, the catalyst of the stack 1 can be suppressed from being poisoned by CO.

  Note that, as long as the stack 1 is not generating power, even if an anode gas containing CO is supplied to the anode of the stack 1, CO poisoning of the catalyst of the stack 1 is suppressed. On the other hand, when the stack 1 is generating electric power, when the anode gas containing CO is supplied to the anode of the stack 1, the influence of the CO poisoning of the catalyst of the stack 1 tends to increase.

  According to the above-described embodiment, the anode gas supplied to the anode from the inlet of the stack 1 at the time of starting the system hardly contributes to the power generation reaction in the stack 1 and passes through the anode outlet valve 92 to the anode off-gas passage 91. Then, the water is discharged as it is, and the moisture is reduced by the anode off-gas condenser 93. Thereafter, the moisture is supplied to the burner 71 of the reformer 70 and burned by the combustion air in the burner 71.

  It is also conceivable to form a bypass passage that connects the anode gas passage 76 and the anode offgas passage 91 so as to bypass the anode of the stack 1. According to this method, the anode gas generated by the reformer 70 is allowed to pass through the bypass passage, thereby bypassing the anode of the stack 1 and flowing out to the anode off-gas passage 91, and the moisture is reduced by the anode off-gas condenser 93. Then, the fuel is supplied to the burner 71 and burned by the combustion air by the burner 71. However, this system requires a bypass path and may require a bypass valve that opens and closes the bypass path, leading to increased costs and complicated piping. In this regard, according to this embodiment, there is an advantage that the bypass passage and the bypass valve for opening and closing the bypass passage can be eliminated.

  According to the present embodiment, when the temperature of the reformer 70 is stabilized at the time of starting the system, the stability of the composition of the anode gas generated by the reformer 70 is also improved, and the concentration of CO contained in the anode gas is reduced. To do. Therefore, the control unit 5 shifts from the first control to the second control, opens the cathode inlet valve 85 and the cathode outlet valve 87 and operates the pump 81 to supply the cathode gas to the cathode of the stack 1. At this time, the anode gas is supplied to the anode of the stack 1. Thus, in the second control, the control unit 5 supplies the cathode gas flow rate corresponding to the power generation amount requested of the stack 1 to the cathode of the stack 1. Thereby, the stack 1 generates power well in the second control. In this case, as described above, the stability of the composition of the anode gas is improved and the CO concentration is lowered, so that CO poisoning of the catalyst of the anode of the stack 1 is suppressed.

  Note that, according to the present embodiment, the anode gas is actively supplied from the inlet of the stack 1 to the anode without detouring at the time of starting the system. For this reason, when the start-up time is long, the moisture of the ion conductive membrane in the membrane electrode assembly of the stack 1 may be reduced, and the proton conductivity of the ion conductive membrane may be lowered. However, since the anode gas generated by the steam reforming in the reformer 40 contains steam, there is no particular problem.

(Embodiment 2)
Since this embodiment basically has the same configuration and the same function and effect as those of the first embodiment, FIGS. 1 and 2 are applied mutatis mutandis. At the time of starting the system, the temperature of the CO reduction unit 77 is not necessarily sufficient, and it takes time to warm up the CO reduction unit 77. Before the warming-up of the CO reduction unit 77 is completed, the temperature stability of the reformer 70 is not necessarily sufficient, and in addition, the CO reduction unit 77 has a low CO temperature, so that the CO reduction action in the CO reduction unit 77 is not sufficient. There is a risk of not. In this case, the CO concentration contained in the anode gas may be high when the system is started.

  On the other hand, after the warming-up of the CO reduction unit 77 is completed, the temperature of the CO reduction unit 77 is high, and thus the catalyst activation temperature region of the CO reduction unit 77 is obtained. The CO concentration contained in the anode gas that has passed through the CO reduction unit 77 is low. Therefore, the control unit 5 reduces the oxygen of the cathode before the CO reduction unit 77 is warmed up (when the CO concentration contained in the anode gas supplied to the anode may be higher (than a predetermined value)). The above-described first control in the state is executed, and the power generation reaction of the stack 1 is limited.

  On the other hand, after the warming-up of the CO reduction unit 77 is completed (when the CO concentration contained in the anode gas supplied to the anode is considered to be low (below a predetermined value)), the control unit 5 The second control is performed with the open state, and the power generation reaction of the stack 1 is promoted.

  Further explanation will be added. That is, before starting the operation of the system, in the first control, the cathode inlet valve 85 and the cathode outlet valve 87 are closed and the cathode is sealed. Similarly, the anode inlet valve 75 and anode outlet valve 92 are closed and the anode is sealed.

  At the start of operation of the system, the controller 5 closes the cathode inlet valve 85 and the cathode outlet valve 87 and seals the cathode before the CO reduction unit 77 is warmed up. As described above, the air pump 72 is operated to supply combustion air to the burner 71, the anode inlet valve 75 and the anode outlet valve 92 are opened, and the fuel pump 73 is operated to reform the reforming fuel. 70, combustion fuel is supplied to the burner 71. As a result, the combustion fuel supplied to the burner 71 burns, so that the reformer 70 is heated to a high temperature so as to be suitable for the reforming reaction. Thereafter, the control unit 5 operates the water pump 74 to supply the reforming water to the reforming device 70. As a result, in the reformer 70, the gaseous hydrocarbon-based reforming fuel is steam reformed, and an anode gas (hydrogen-containing gas) containing hydrogen as a main component is generated. Here, the anode inlet valve 75 and the anode outlet valve 92 are opened. Therefore, the anode gas is supplied to the anode without bypassing the anode of the stack 1. At this time, as described above, since the cathode inlet valve 85 and the cathode outlet valve 87 are closed, the ingress of the cathode gas is suppressed. As a result, the oxygen concentration at the cathode of the stack 1 is the oxygen concentration inherent in the cathode gas. Is maintained in a reduced state.

  As described above, at the start of operation of the fuel cell system, the control unit 5 performs the first control and positively supplies the anode gas to the anode of the stack 1. At the time of starting the system, the composition of the anode gas is not necessarily stable, so there is a possibility that the CO concentration becomes high, and it is not preferable to supply the anode of the stack 1 to actively generate a power generation reaction.

  Therefore, according to the present embodiment, when the system is started, anode gas is actively supplied to the anode of the stack 1, but the cathode inlet valve 85 and the cathode outlet valve 87 of the cathode of the stack 1 are closed and the cathode is sealed. It is in a stopped state. That is, the oxygen concentration at the cathode of the stack 1 is lower than the oxygen concentration inherent in the cathode gas (air). For this reason, at the start-up of the system, the number of moles of oxygen inside the cathode is significantly reduced or depleted compared to the number of moles of hydrogen contained in the anode gas supplied to the anode. It is supposed to be in a state. As a result, the power generation reaction in the stack 1 is greatly limited when the system is started. Therefore, CO poisoning of the anode catalyst is suppressed.

  For this reason, the anode gas supplied to the anode from the inlet of the stack 1 does not contribute much to generation of a power generation reaction (that is, does not significantly reduce the hydrogen concentration), and passes through the anode outlet valve 92 to the anode off-gas passage 91. Then, after the excess water is reduced by the anode off-gas condenser 93, it is supplied to the burner 71 and burned by the combustion air in the burner 71.

  According to the above-described embodiment, when the time elapses when the system is started, the temperature rising temperature of the reformer 70 is stabilized, the temperature rising temperature of the CO reduction unit 77 is also stabilized, and the temperature of the CO reduction unit 77 is increased. The machine is also completed. That is, after the warming-up of the CO reduction unit 77 is completed, the temperatures of the reformer 70 and the CO reduction unit 77 rise, the catalyst of the reformer 70 and the catalyst of the CO reduction unit 77 are activated, and the reformer 70 and The CO reduction action in the CO reduction part 77 becomes good, and the CO concentration contained in the anode gas is greatly reduced.

  Therefore, the control unit 5 shifts from the first control to the second control. In the second control, the cathode inlet valve 85 and the cathode outlet valve 87 are opened while the anode inlet valve 75 and the anode outlet valve 92 are kept open. Further, the pump 81 is activated to supply cathode gas (air) to the cathode of the stack 1. Thus, the control unit 5 supplies the cathode gas to the cathode of the stack 1 according to the amount of power required for the stack 1 and generates power in the stack 1.

  According to the present embodiment as described above, it is not necessary for the anode gas to bypass the stack 1 when the system is started up, as in the above-described embodiment. Therefore, there is an advantage that the bypass passage and the bypass valve for opening and closing the bypass passage can be eliminated.

  FIG. 3 shows an example of a flowchart of the control performed by the control unit 5 when the system is activated. The flowchart is not limited to this. First, the start-up of the operation of the fuel cell system will be described. As described above, in the state before starting the operation of the system, the cathode inlet valve 85 and the cathode outlet valve 87 are closed and the cathode is sealed. In this case, the cathode is preferably in an oxygen-deficient state. The anode inlet valve 75 and anode outlet valve 92 are closed and the anode is sealed.

  First, if the start-up operation of the system is instructed, the control unit 5 operates the air pump 72 to supply combustion air to the burner 71 as the first control, and further energizes the glow discharger for ignition. Then, the control unit 5 opens the anode inlet valve 75 and the anode outlet valve 92 (steps S104 and S106). Further, the fuel pump 73 is operated to supply gaseous reforming fuel to the reformer 70, and gaseous combustion fuel is supplied to the burner 71 (step S108). As a result, the burner 71 is ignited and the fuel supplied to the burner 71 burns, so that the reformer 70 is heated to a high temperature so as to be suitable for the reforming reaction.

  Furthermore, the control unit 5 determines whether or not the reformer 70 is ready for steam generation (step S110). If the reforming device 70 has been heated and preparation for steam generation is complete (YES in step S110), the control unit 5 operates the water pump 74 to supply reforming water to the reforming device 70 (step). S112). As a result, in the reformer 70, the hydrocarbon-based reforming fuel is steam reformed, and an anode gas containing hydrogen as a main component is generated. At this time, although the cathode is sealed, the anode inlet valve 75 and the anode outlet valve 92 are already opened, so the anode gas is supplied to the anode of the stack 1 (first control).

  The control unit 5 determines whether or not the warming-up of the CO reduction unit 77 is completed, that is, whether or not the CO reduction unit 77 is equal to or higher than a predetermined temperature using the temperature sensors 78t and 79t (Step S114). If the temperature of at least one of the temperature sensors 78t and 79t is equal to or higher than a predetermined temperature, the warm-up is completed, and if it is lower than the predetermined temperature, the warm-up is completed. If the temperature of the CO reduction unit 77 is not sufficiently high and the warming-up of the CO reduction unit 77 is not completed (NO in step S114), the control unit 5 supplies the anode gas to the anode of the stack 1 while It waits, implementing 1st control until warming-up of the reduction part 77 is completed.

  In the first control described above, since the anode inlet valve 75 and the anode outlet valve 92 are opened, the anode gas generated by the reformer 70 is supplied to the anode of the stack 1. However, since the cathode inlet valve 85 and the cathode outlet valve 87 are closed, the power generation reaction is limited as described above. Therefore, the anode gas does not contribute much to the power generation reaction, and is supplied from the anode off-gas passage 91 to the burner 71 and burned by the burner 71.

  If the result of determination in step S114 is that the warming-up of the CO reduction unit 77 has been completed (completion of step S114), the CO concentration contained in the anode gas that has passed through the CO reduction unit 77 is reduced satisfactorily (for example, 10 ppm or less). Therefore, the control unit 5 opens the cathode inlet valve 85 (step S116) and opens the cathode outlet valve 87 (step S118) in order to shift from the first control to the second control. Next, the pump 81 is operated (step S120), and the cathode gas is supplied to the cathode of the stack 1. Between step S102 to step S122 described above, the anode and cathode of the stack 1 are in an open circuit state that is not electrically connected to the power load 57.

  Note that the control unit 5 determines the value of the OCV, and if the value of the OCV is excessively low, the system is abnormal, so the system is stopped (step S126). If the value of OCV is higher than the predetermined value, control unit 5 electrically connects stack 1 and power load 57, that is, electrically connects the anode and cathode of stack 1 via power load 57. Then, the power generation operation of the system is started (step S124), and the process returns to the main routine.

(Embodiment 3)
Since this embodiment basically has the same configuration and the same operation and effect as those of the first and second embodiments, FIGS. 1 and 2 are applied mutatis mutandis. According to the present embodiment, when the system operation is stopped, the control unit 5 electrically disconnects the stack 1 and the power load 54 and opens the stack 1 in an open circuit state. While the valve 92 is opened to supply the anode gas to the anode of the stack 1, the cathode inlet valve 85 and the cathode outlet valve 87 are closed to seal the cathode gas (air) of the cathode.

  At this time, the OCV of the stack 1 may gradually increase. In this state, when the value of OCV becomes excessively higher than the predetermined voltage value, the control unit 5 turns on the discharge switching element 53 to electrically connect the stack 1 and the discharge load 54. As a result, the power generated in the stack 1 is actively discharged and consumed by the discharge load 54 (power consumption unit). As a result, an excessive increase in the OCV value of the stack 1 is suppressed. Furthermore, since the power generation reaction of the stack 1 proceeds at the time of discharge, the oxygen inside the cathode is reduced and consumed more than before power consumption.

  In other words, when discharging is performed by the discharge load 54, the control unit 5 opens the anode inlet valve 75 and the anode outlet valve 92 to positively supply the anode gas to the anode of the stack. For this reason, the oxygen concentration inside the cathode is reduced and consumed compared to the hydrogen concentration inside the anode. For this reason, when the system is stopped, an oxygen-deficient state (oxygen-reduced state), that is, a nitrogen gas-enriched state is well formed at the cathode of the stack 1.

  As described above, when an oxygen-deficient state (oxygen-reduced state, nitrogen-enriched state) is formed at the cathode of the stack 1 when the system is stopped, the control unit 5 turns off the switching element 53 and discharges by the discharge load 54. And the anode inlet valve 75 and the anode outlet valve 92 are closed to seal the anode gas (hydrogen-containing gas) to the anode. At this time, the closed state of the cathode inlet valve 85 and the cathode outlet valve 87 is maintained until the next activation of the system. For this reason, the oxygen-deficient state (nitrogen-enriched state) at the cathode is well maintained until the next start-up of the system.

  Furthermore, according to the above-described embodiment, when the system is activated, the control unit 5 can be implemented in the same manner as in Embodiments 1 and 2 described above. That is, according to the present embodiment, an oxygen-deficient state (nitrogen-enriched state) of the cathode is formed at the previous stop of the system and is maintained until the next start-up of the system. As a result, the next time the system is started, the control unit 5 opens the anode inlet valve 75 and the anode outlet valve 92 in a state where the reformer 70 is operating, and positively supplies the anode gas to the anode of the stack 1. Supply. At this time, the controller 5 closes the cathode inlet valve 85 and the cathode outlet valve 87 of the cathode of the stack 1 and maintains the oxygen-deficient state (nitrogen-enriched state) at the cathode. For this reason, at the time of starting the system, the number of moles of oxygen inside the cathode of the stack 1 is greatly depleted compared to the number of moles of hydrogen contained in the anode gas supplied to the anode of the stack 1. The power generation reaction in the stack 1 is limited.

  As a result, even when an anode gas that may contain CO is positively supplied to the anode of the stack 1 at the time of starting the system, the power generation reaction in the stack 1 hardly occurs, and CO poisoning of the catalyst of the anode does not occur. It is suppressed. That is, the anode gas flows out as it is to the anode off-gas passage 91 through the anode outlet valve 92 with little power generation reaction, and after the moisture is reduced by the moisture absorption passage 82b and the anode off-gas condenser 93, the anode gas is supplied to the burner 71. Supplied and burned by the burner 71 with combustion air.

  As described above, also in the present embodiment, as described above, the control unit 5 performs the same control as in the first and second embodiments when the system is started. That is, the anode gas that may contain CO supplied from the inlet of the stack 1 to the anode hardly contributes to the power generation reaction and suppresses CO poisoning of the anode catalyst. Further, the anode gas flows out into the anode off-gas passage 91 through the anode outlet valve 92, lowers the moisture by the anode off-gas condenser 93, is supplied to the burner 71, and is burned by the combustion air in the burner 71.

  Also in this embodiment, the advantage which can abolish a bypass path and a bypass valve similarly to Embodiment 1 and 2 mentioned above is acquired.

  FIG. 4 shows an example of a flowchart of control executed by the control unit 5 when the system is stopped. The flowchart is not limited to this. That is, when stopping the operation of the system, the control unit 5 shifts the stack 1 from the normal operation state to the minimum load state (minimum power generation amount) (step S202). That is, the control unit 5 reduces the number of revolutions (drive amount) per unit time of the fuel pump 73, the water pump 74, and the pump 81, and suppresses the flow rates of the anode gas and the cathode gas per unit time. Further, a power generation stop command is output, and the electrical connection between the power load 57 and the stack 1 is interrupted (step S204). In this case, the OCV may become excessively high.

Further, the control unit 5 minimizes the reforming fuel and the reforming water supplied to the reformer 70, and shifts the reformer 70 from the reforming operation to the minimum load operation (step S206). At the lowest load operation, the anode gas is still produced although the flow rate is reduced. )
Next, the controller 5 closes the cathode outlet valve 87 (step S208), waits for a predetermined time (step S210), and then closes the cathode inlet valve 85 (step S212) to seal the cathode. Thereafter, the control unit 5 stops the operation of the pump 81 and stops the supply of the cathode gas (step S214). If the valves are closed in this order, the cathode gas is sealed in the cathode as much as possible, the pressure of the cathode gas sealed in the cathode is increased as much as possible, and excessive negative pressure of the cathode is suppressed or prevented. The Therefore, there is an advantage that the negative pressure resistance design of the stack 1 becomes easy.

  Since the anode inlet valve 75 and the anode outlet valve 92 are opened and the reformer 70 is warming up, the anode gas generated by the reformer 70 is supplied to the anode of the stack 1. Here, since the cathode gas (air) remains on the cathode of the stack 1 and the electrical connection between the power load 57 and the stack 1 is interrupted, the OCV of the stack 1 may increase excessively. . Therefore, it is determined whether or not the OCV value Vc is less than a first predetermined value Vx (eg, 0.3 volts) (step S216). The first predetermined value Vx can be appropriately set according to the type of system, the material of the catalyst of the stack 1, and the like. If the OCV value Vc exceeds the first predetermined value Vx (for example, 0.3 volts) to the high voltage side (NO in step S216), the control unit 5 turns on the switching element 53, and the stack 1, the discharge load 54, Are electrically connected, and the power of the stack 1 is discharged by the discharge load 54 and consumed (step S218). Thereby, an excessive increase in OCV is suppressed, and electrochemical deterioration of the catalyst of the stack 1 is suppressed.

  When the discharge is performed as described above, the power generation reaction in the anode and cathode of the stack 1 proceeds. Therefore, the oxygen concentration inside the cathode in the sealed state is reduced as compared with that before power consumption, and the cathode is in an oxygen-deficient state ( Nitrogen-rich state) is set well.

  If the result of determination in step S216 is that the OCV value Vc is less than the first predetermined value Vx (eg, 0.3 volts) (YES in step S216), the control unit 5 stops the minimum load operation of the reformer 70. The operation of the water pump 74 and the fuel pump 73 is stopped. As a result, the supply of the reforming fuel and the reforming water to the reforming device 70 is stopped. Even if the operation of the reforming device 70 is stopped, the air pump 72 is still operating, and combustion air is supplied to the reforming device 70 as cooling air, and cooling of the reforming device 70 is promoted.

  Further, the control unit 5 closes the anode inlet valve 75 and the anode outlet valve 92 (steps S222 and S224). Therefore, the supply of the anode gas to the anode of the stack 1 is stopped. Here, if the temperature of the reforming apparatus 70 that has been stopped is lower than the predetermined temperature (YES in step S228), the operation of the air pump 72 is stopped to end the cooling of the reforming apparatus 70, Stop supplying the combustion air as cooling air to the reforming device 70 (step S230), stop the temperature cooling process of the reforming device 70, and stop the operation of system auxiliary equipment to stop the system. (Step S232).

  Now, according to the present embodiment, when the OCV value Vc exceeds the first predetermined value Vx (for example, 0.3 volts) when the system is stopped, the signal is input to the control unit 5, and the control unit 5 Performs interrupt processing (FIG. 5). Therefore, as shown in FIG. 5, when the OCV value Vc exceeds a first predetermined value Vx (for example, 0.3 volts), the control unit 5 turns on the switching element 53, the stack 1, the discharge load 54, and the like. Are electrically connected, and the power of the stack 1 is discharged by the discharge load 54 (step S302). At the time of discharging, the power generation reaction at the anode and cathode of the stack 1 proceeds, so that the oxygen concentration inside the cathode is reduced as compared with that before power consumption. Therefore, the cathode is set in an oxygen-deficient state (nitrogen-enriched state).

  The control unit 5 determines whether or not the OCV value Vc is less than a first predetermined value Vx (eg, 0.3 volts) (step S304), and the OCV value Vc is set to a first predetermined value Vx (eg, 0.3 volts). If it is less than (volt), the stack 1 and the discharge load 54 are electrically cut off, and the discharge is stopped (step S306). However, the OCV may recover over time. Therefore, the control unit 5 waits for a predetermined time (step S308), compares the OCV value Vc with a second predetermined value Vy (for example, 0.5 volts) (step S310), and the value Vc is the second predetermined value Vy. If it is above (NO in step S310), the control unit 5 turns on the switching element 53 again, electrically connects the stack 1 and the discharge load 54, and discharges the power of the stack 1 again by the discharge load 54. It is consumed (step S302). As a result of the determination in step S310, if the OCV value Vc is less than the second predetermined value Vy (for example, 0.5 volts) (YES in step S310), the OCV is low, so the control unit 5 returns to the main routine. . The first predetermined value Vx, the second predetermined value Vy, and the predetermined time can be appropriately set according to the fuel cell system.

  Thus, according to the present embodiment, when the OCV value Vc rises excessively in a state where the stack 1 and the power load 57 are cut off when the system is stopped, the stack 1 and the discharge load 54 are electrically connected. Then, discharge is performed by the discharge load 54. As a result, the power generation reaction of the stack 1 proceeds, the oxygen concentration inside the cathode is reduced more than before power consumption, and the cathode is in an oxygen-deficient state (nitrogen-enriched state). Therefore, when the system is stopped, the cathode is set in an oxygen-deficient state (nitrogen-enriched state).

  As described above, the closed state of both cathode inlet valve 85 and cathode outlet valve 87 is maintained until the next start-up of the system. For this reason, the oxygen-deficient state (nitrogen-enriched state) at the cathode of the stack 1 is well maintained until the next start-up of the system.

  As described above, according to the present embodiment, when starting the system, the control unit 5 can be implemented in the same manner as in the first and second embodiments. That is, according to the present embodiment, when the system is stopped, the control unit 5 positively forms an oxygen-deficient state (nitrogen-enriched state) at the cathode of the stack 1. The control unit 5 maintains the closed state of the cathode inlet valve 85 and the cathode outlet valve 87, thereby favorably maintaining the oxygen-deficient state (nitrogen-enriched state) at the cathode of the stack 1 until the next startup of the system. As a result, when the system is started next time, the control unit 5 opens the anode inlet valve 75 and the anode outlet valve 92 and supplies anode gas that may contain CO to the anode of the stack 1. The cathode is maintained in an oxygen deficient state (nitrogen rich state) until the next start-up of the system. As a result, even when anode gas is positively supplied to the anode of the stack 1 at the time of starting the system, the power generation reaction in the stack 1 is suppressed, and CO poisoning of the anode of the stack 1 is suppressed.

  Also in the present embodiment, as described above, the control unit 5 performs the same control as in the first and second embodiments when the system is started. That is, the anode gas supplied to the anode from the inlet of the stack 1 flows out to the anode off-gas passage 91 through the anode outlet valve 92 without generating a power generation reaction in the stack 1, and the moisture is reduced by the anode off-gas condenser 93. Then, the gas is supplied to the burner 71 and burned by the combustion air in the burner 71. As described above, since the anode gas supplied to the anode gas of the stack 1 at the start-up of the system can suppress generation of a power generation reaction in the stack 1, CO poisoning of the catalyst at the anode is suppressed.

(Embodiment 4)
Since this embodiment basically has the same configuration and the same function and effect as the first, second, and third embodiments, FIGS. 1 and 2 are applied mutatis mutandis. When the operation of the system is stopped, the control unit 5 operates the pump 81 with the cathode outlet valve 87 closed and the cathode inlet valve 85 opened to supply the cathode gas to the cathode of the stack 1. Thereafter, the controller 5 closes the cathode inlet valve 85 with the cathode outlet valve 87 closed. As a result, the inside of the cathode of the stack 1 is filled with the cathode gas (air). The pressure of the cathode may be a high pressure exceeding atmospheric pressure or about atmospheric pressure.

  In this case, the cathode gas is present at the cathode of the stack, and the anode gas is supplied to the anode. For this reason, when the anode and the cathode of the stack 1 are electrically cut off, the OCV of the stack 1 may become excessively high.

  Therefore, when the OCV of the stack 1 becomes excessively high, the control unit 5 turns on the discharge switching element 53 and electrically connects the stack 1 and the discharge load 54 as described above. As a result, the electric power generated in the stack is actively discharged by the discharge load 54 and consumed. An excessive increase in OCV is suppressed during discharge. Further, since the power generation reaction of the stack 1 proceeds at the time of discharge, the oxygen inside the cathode is consumed, and the oxygen concentration at the cathode is greatly reduced as compared to before power consumption. In this way, oxygen remaining inside the cathode is consumed by the discharge, so that the concentration of the inert nitrogen gas is increased at the cathode. That is, the inside of the cathode of the stack 1 is almost nitrogen gas. According to the present embodiment, whenever the OCV of the stack 1 becomes excessively high, the discharge switching element 53 is turned on and the discharge load 54 is discharged. As a result, the oxygen inside the cathode is consumed and made deficient.

  When the discharge is performed a predetermined number of times, the cathode pressure drops as much as oxygen is consumed. Therefore, the control unit 5 may replenish the cathode of the stack 1 with cathode gas (air) by opening the cathode inlet valve 85 with the cathode outlet valve 87 closed and operating the pump 81. In this case, the rotational speed (drive amount) per unit time of the pump 81 can be increased more than the steady operation (rated operation) of the system, but may be the same as the steady operation.

  As described above, the consumption of oxygen by discharge and the replenishment of the cathode gas to the cathode can be alternately performed a predetermined number of times (a plurality of times). Thereby, the inside of a cathode can be made into the high voltage | pressure exceeding atmospheric pressure. However, the inside of the cathode may be under atmospheric pressure.

  In this state, the cathode inlet valve 85 and the cathode outlet valve 87 are closed until the next startup of the system. Therefore, the oxygen-deficient state (nitrogen-enriched state) at the cathode is well maintained until the next start-up of the system.

  As described above, according to the present embodiment, after the control for depleting the oxygen concentration inside the cathode of the stack 1 is performed, the gas sealed in the cathode is substantially nitrogen gas. Therefore, the inside of the cathode of the stack 1 corresponds to a state in which nitrogen gas is sealed. In this case, it is preferable that the pressure of the cathode is higher than the atmospheric pressure in consideration of suppressing the outside air from entering the cathode. Considering a pump, a valve, etc., the cathode pressure can be, for example, less than 3 atmospheres.

  This is because the inside of the cathode is nitrogen-enriched. Even if the period from the stop of the system to the next start-up becomes longer, it is possible to effectively suppress the outside air containing oxygen from entering the cathode of the stack 1. If the pressure of the cathode is higher than atmospheric pressure, the entry of outside air is further suppressed. Therefore, the oxygen-deficient state (nitrogen-enriched state) at the cathode is well maintained until the next start-up of the system.

  As described above, when the system is stopped, the cathode pressure can be increased to atmospheric pressure (1 atm) or more, so that the atmosphere containing oxygen can be prevented from entering the cathode. Therefore, the cathode outlet valve 87 and the cathode inlet valve 85 are not required to have an excessive sealing property, and there is an advantage that an inexpensive valve can be used. Of course, an expensive valve having a high sealing property may be used.

(Embodiment 5)
In FIG. 6, the present embodiment basically has the same configuration and the same function and effect as the first to fourth embodiments. Hereinafter, the description will focus on the different parts. That is, as shown in FIG. 6, the cathode outlet valve 87 </ b> B is a check valve provided on the cathode outlet side of the stack 1, and is disposed upstream of the moisture absorption path 82 b of the humidifier 82. A check valve is preferable in terms of cost. The cathode outlet valve 87B allows the cathode off gas discharged from the cathode of the stack 1 to flow out in the direction discharged from the cathode (arrow W1 direction), but prevents the flow in the opposite direction (arrow W2 direction). The cathode outlet valve 87B includes a valve port 870 communicating with the cathode off-gas passage 96, a valve body 872 for closing the valve port 870, and a biasing spring 874 that biases the valve port 870 in a direction to close the valve body 872. And have. The biasing spring 874 has a spring force capable of maintaining the inside of the cathode of the stack 1 at a pressure exceeding the atmospheric pressure. For this reason, if the supply pressure of the cathode gas is increased, the inside of the cathode of the stack 1 can be maintained at a pressure exceeding the atmospheric pressure. Therefore, it is possible to suppress the outside air containing oxygen from entering the cathode of the stack 1 from the cathode outlet valve 87B between the time when the system is stopped and the time when the system is next started. As a result, if the cathode outlet valve 87B is closed, the inside of the cathode of the stack 1 is satisfactorily maintained in an oxygen-deficient state (oxygen-reduced state) from the time when the system is stopped until the next start-up of the system. Is done. Also in this embodiment, similarly to the above-described embodiment, there is an advantage that the bypass passage and the bypass valve for opening and closing the bypass passage can be eliminated.

(Embodiment 6)
FIG. 7 shows a sixth embodiment. This embodiment has basically the same configuration and the same function and effect as the first to fifth embodiments. Hereinafter, the description will focus on the different parts. The cathode outlet valve 87B is a check valve provided on the outlet side of the cathode of the stack 1. The biasing spring 874 of the cathode outlet valve 87B has a spring force capable of maintaining the inside of the cathode of the stack 1 at a pressure exceeding atmospheric pressure. The cathode outlet valve 87B is disposed downstream of the moisture absorption path 82b of the humidifier 82. The cathode off gas discharged from the stack 1 contains a large amount of water vapor. The cathode off-gas water vapor is reduced in the moisture absorption path 82b. For this reason, the water vapor amount of the cathode off-gas passing through the cathode outlet valve 87B is reduced. Therefore, the valve diameter of the cathode outlet valve 87B can be reduced, and the advantage that the valve 87B is downsized can be obtained.

(Embodiment 7)
FIG. 8 shows a seventh embodiment. The present embodiment has basically the same configuration and the same function and effect as the first to sixth embodiments. Hereinafter, the description will focus on the different parts. As shown in FIG. 8, the cathode outlet valve 87 </ b> B is disposed downstream of the moisture absorption path 82 b of the humidifier 82 on the cathode outlet side of the stack 1. A pump 81 (cathode gas transfer source) for supplying the cathode gas to the cathode of the stack 1 is provided on the inlet side of the cathode of the stack 1. The cathode inlet valve 85D is incorporated in the pump 81. As a result, if the cathode inlet valve 85D is closed during the period from the stop of the system to the next startup, the outside air containing oxygen can be prevented from entering the cathode from the inlet of the stack 1. As a result, the inside of the cathode of the stack 1 is satisfactorily maintained in an oxygen-deficient state (nitrogen-enriched state) from the time of system shutdown until the next startup. The nitrogen enriched state refers to a state of nitrogen concentration higher than the nitrogen concentration of air. Also in this embodiment, similarly to the above-described embodiment, there is an advantage that the bypass passage and the bypass valve for opening and closing the bypass passage can be eliminated.

(Embodiment 8)
FIG. 9 shows an eighth embodiment. This embodiment has basically the same configuration and the same function and effect as the first to eighth embodiments. A CO reduction unit 77B is provided on the outlet side of the reformer 70. The CO reduction part 77B is formed of a CO shift part 78 and a methanation reaction part 79B. As described above, the CO shift unit 78 reduces the concentration of CO contained in the anode gas generated by the reformer 70 by the shift reaction of Formula (1). The methanation reaction unit 79B further reduces the concentration of CO by methanating CO contained in the anode gas that has passed through the CO shift unit 78 by a methanation reaction with H ₂ . CO is not preferred because it affects the performance of the stack 1 catalyst.
Methanation reaction… CO + 3H ₂ → CH ₄ + H ₂ O (exothermic reaction)
Also in this embodiment, similarly to the above-described embodiment, there is an advantage that the bypass passage and the bypass valve for opening and closing the bypass passage can be eliminated.

(Embodiment 9)
FIG. 10 shows a ninth embodiment. This embodiment has basically the same configuration and the same function and effect as the first embodiment. A CO reduction section 77C is provided on the outlet side of the reformer 70. The CO reduction unit 77C includes a first methanation reaction unit 78C that reduces the concentration of CO contained in the anode gas generated by the reformer 70 by a methanation reaction, and an anode that has passed through the first methanation reaction unit 78C. The second methanation reaction part 79C is formed by methanating CO contained in the gas by a methanation reaction with H ₂ to further reduce the CO concentration. According to this embodiment, similarly to the above-described embodiment, there is an advantage that the bypass passage and the bypass valve for opening and closing the bypass passage can be eliminated.

(Embodiment 10)
Since this embodiment basically has the same configuration and the same operation and effect as those of the first embodiment, FIGS. 1 and 2 are applied mutatis mutandis. At the time of starting the system, the anode gas is actively supplied to the anode from the inlet of the stack 1 without diverting the anode gas. For this reason, when starting time becomes long, the water | moisture content of the ion conductive film in the membrane electrode assembly of the stack 1 may be reduced, and there exists a possibility that the proton conductivity of an ion conductive film may fall. At this time, the anode gas generated by the steam reforming in the reformer 40 contains steam, so that there is no particular problem.

  However, if the anode gas is supplied to the anode for a long time while power generation is limited, the ion conductive film of the stack 1 may move in the drying direction depending on conditions. In this case, at the time of starting the system, the following measures can be adopted in order to suppress excessive drying of the ion conductive film of the stack 1.

  (I) At the time of starting the system, the control unit 5 suppresses the amount of heat generated by the heater 29 when preheating the coolant flowing through the main cooling circuit 2 with the heater 29 as compared with the case of flowing the anode gas to the bypass. In this way, the temperature of the stack 1 is decreased by ΔT1, and drying inside the stack 1 is suppressed.

  (Ii) At the time of starting the system, the reformer 40 is controlled so that the temperature of the anode gas generated by the reformer 40 is increased by ΔT2 as compared with the case where the anode gas is caused to flow through the bypass. Thereby, the amount of water vapor that can be held in the anode gas can be increased.

  (Iii) At the time of starting the system, the S / C ratio (steam / carbon) in the anode gas generated by the reformer 40 is more stable than when the anode gas is caused to flow in a detour, or the stack 1 is operated in a steady state ( The reformer 40 is controlled to be higher than that during rated operation). Since the amount of water vapor in the anode gas increases, the moisture reduction in the ion conductive membrane can be further suppressed. Even in this case, since the anode off-gas condenser 93 for reducing the moisture of the anode gas is provided, the combustibility in the burner 71 is maintained well.

(Other)
The system 100 is not limited to the arrangement and structure of the system shown in FIG. 1, and the arrangement and structure can be changed as appropriate. The humidifier does not necessarily have to be mounted. According to the above-described embodiment, when the value of OCV becomes excessively higher than the predetermined voltage value, the control unit 5 electrically connects the stack 1 and the discharge load 54, and uses the electric power generated in the stack 1 as the discharge load 54. Although it is discharged and consumed positively by the (power consumption part), it is not restricted to this, You may make it store in a capacitor and / or a storage battery.

  The condensers 93, 97, and 24 shown in FIG. 1 may be provided as necessary. The pump 81 and the air pump 72 may be a fan, a blower, or a compressor. The fuel pump 73 may be a fan, a blower, or a compressor. The water pump 74 may be a fan, a blower, or a compressor. The reforming fuel supplied to the reforming apparatus is not limited to gas such as city gas or biogas, but may be liquid fuel such as kerosene, methanol, dimethyl ether, and gasoline. The combustion fuel supplied to the burner is not limited to gas, and may be liquid fuel such as kerosene, methanol, dimethyl ether, gasoline, or solid fuel.

  The present invention is not limited to the embodiments described above and shown in the drawings, and can be implemented with appropriate modifications within a range not departing from the gist. Structures and functions specific to one embodiment can be applied to other embodiments. The following technical idea can be understood from the description of the present specification.

  [Additional Item 1] A fuel cell having an anode and a cathode, an anode gas passage for supplying anode gas to the anode of the fuel cell, and a cathode gas containing oxygen to the cathode of the fuel cell A cathode gas passage, an inlet opening / closing portion for opening / closing the cathode inlet side of the fuel cell, an outlet opening / closing portion for opening / closing the cathode outlet side of the fuel cell, the inlet opening / closing portion and the outlet A fuel cell system comprising a control unit for controlling the opening / closing unit.

  [Additional Item 2] The fuel cell system according to Additional Item 1, wherein a CO reduction unit for reducing the CO concentration contained in the anode gas generated by the reformer is provided upstream of the anode of the fuel cell.

  [Additional Item 3] In Additional Item 1 or 2, when the operation of the fuel cell system is started, the control unit maintains the inlet opening / closing unit and the outlet opening / closing unit in a closed state, and A first control for supplying the anode gas to the anode, and then supplying the cathode gas to the anode of the fuel cell while supplying the cathode gas to the cathode of the fuel cell according to the amount of power generated by the fuel cell; The fuel cell system which implements the 2nd control which supplies to. In the first control, the oxygen concentration at the cathode of the fuel cell is made lower than the oxygen concentration inherent in the cathode gas.

  [Appendix 4] A fuel cell having an anode and a cathode, an anode gas passage for supplying an anode gas to the anode of the fuel cell, and a cathode gas containing oxygen to the cathode of the fuel cell. A cathode gas passage, an inlet opening / closing portion for opening / closing the cathode inlet side of the fuel cell, an outlet opening / closing portion for opening / closing the cathode outlet side of the fuel cell, the inlet opening / closing portion and the outlet A fuel cell system including a control unit for controlling the opening and closing unit, when the operation of the fuel cell system is stopped, the control unit includes the inlet opening and closing unit and the outlet opening and closing unit of the cathode of the fuel cell. While the cathode gas is present at the cathode of the fuel cell and the anode gas is being supplied to the anode, By the power of the fuel cell is consumed by the power unit, the fuel cell the cathode of the fuel cell system the oxygen concentration to implement control for reducing than the previous power consumption. In this case, oxygen at the cathode is actively consumed. When the system is stopped, the cathode can be maintained in an oxygen-reduced state such as an oxygen-deficient state.

  [Additional Item 5] In Additional Item 4, after performing control to reduce the oxygen concentration inside the cathode of the fuel cell as compared to before power consumption, the control unit includes the outlet opening / closing unit of the cathode of the fuel cell. The inlet opening / closing part is opened in a closed state, and the cathode gas is supplied again to the cathode of the fuel cell to increase the internal pressure of the cathode to above atmospheric pressure, and then the outlet opening / closing part and A fuel cell system that maintains the pressure inside the cathode at atmospheric pressure or higher by maintaining the inlet opening / closing portion closed. The pressure drop at the cathode due to the consumption of oxygen can be compensated. In this case, since the outside air containing oxygen is suppressed from entering the cathode, the oxygen-deficient state such as an oxygen-deficient state (a nitrogen gas-enriched state at atmospheric pressure or higher) at the cathode is well maintained, and the next startup It is preferable to maintain the pressure at atmospheric pressure or higher. The outlet opening / closing section and the inlet opening / closing section can be made inexpensive and do not have excessive sealing properties.

  The present invention can be applied to, for example, stationary, vehicle, electrical equipment, electronic equipment, and portable fuel cell systems.

1 is an overall system diagram of a fuel cell system according to Embodiment 1. FIG. 1 is a system diagram of a main part of a fuel cell system according to Embodiment 1. FIG. 4 is a flowchart of control executed by the control unit when the system is activated according to the embodiment. 6 is a flowchart of control executed by the control unit when the system is stopped according to the embodiment. 7 is a flowchart of interrupt control executed by the control unit when the system is stopped according to the embodiment. FIG. 10 is a system diagram of a fuel cell system according to Embodiment 5. FIG. 10 is a system diagram of a fuel cell system according to Embodiment 6. FIG. 10 is a system diagram of a fuel cell system according to Embodiment 7. FIG. 10 is a system diagram of a main part of a fuel cell system according to Embodiment 8. FIG. 10 is a system diagram of a main part of a fuel cell system according to Embodiment 9.

Explanation of symbols

  In the figure, 1 is a stack (fuel cell), 5 is a control unit, 53 is a switching element, 54 is a discharge load (power consumption unit), 55 is an inverter, 56 is a breaker, and 57 is a power load (home power load) 70. Is a reformer, 71 is a burner, 76 is an anode gas passage, 77 is a CO reduction unit, 78 is a CO shift unit, 78 is a CO oxidation unit, 80 is a cathode gas passage, 81 is a pump (cathode gas carrier source), 85 Denotes a cathode inlet valve (inlet opening / closing part), 87 denotes a cathode outlet valve (outlet opening / closing part), 91 denotes an anode off-gas passage, 96 denotes a cathode off-gas passage, 75 denotes an anode inlet valve, and 92 denotes an anode outlet valve.

Claims (10)

A fuel cell having an anode and a cathode; an anode gas passage for supplying an anode gas that may contain CO to the anode of the fuel cell; and an anode gas passage provided upstream of the anode of the fuel cell. A CO reduction section for reducing the concentration of CO contained; a cathode gas passage for supplying a cathode gas containing oxygen to the cathode of the fuel cell; and an inlet opening / closing for opening and closing an inlet side of the cathode of the fuel cell A fuel cell system comprising: a portion; an outlet opening / closing portion for opening / closing the cathode outlet side of the fuel cell; and a control portion for controlling at least the inlet opening / closing portion and the outlet opening / closing portion.
At the start of operation of the fuel cell system,
The controller is
In a state where the inlet opening / closing portion and the outlet opening / closing portion are closed and the cathode of the fuel cell is sealed, the first control is performed to supply the anode gas to the anode of the fuel cell,
Thereafter, the anode gas is supplied to the anode of the fuel cell while the inlet opening / closing portion and the outlet opening / closing portion are opened, and the cathode gas is supplied to the fuel cell according to the amount of power generated by the fuel cell. A fuel cell system for performing a second control to be supplied to the cathode. In Claim 1, the reformer for generating the anode gas supplied to the anode of the fuel cell from the reforming fuel is provided upstream of the CO reduction unit,
The control unit executes the first control before completion of warming-up of the CO reduction unit, and implements the second control after completion of warming-up of the CO reduction unit. 3. The reformer according to claim 1, wherein the reformer is configured to burn a combustion fuel with combustion air, and to generate anode gas from the reforming fuel heated by the burner so as to be suitable for a reforming reaction. And a reforming section for
In the first control, the control unit discharges the anode gas supplied to the anode inlet of the fuel cell from the anode outlet of the fuel cell, and then supplies the anode gas to the burner via an anode off-gas passage. And the fuel cell system burned with the combustion air by the burner.   The cathode gas is present at the cathode of the fuel cell according to any one of claims 1 to 3, wherein the open circuit voltage of the fuel cell rises above a predetermined value when the fuel cell system is stopped. And, in the state where the anode gas is supplied to the anode and the fuel cell and the power consuming unit are electrically connected, the power consuming unit consumes the power generated in the fuel cell. A fuel cell system that performs control to reduce the oxygen concentration inside the cathode from before the power consumption while suppressing an excessive increase in the open circuit voltage of the fuel cell. 4. The fuel cell system according to claim 1, wherein when the fuel cell system is stopped, the control unit closes the outlet opening / closing portion of the cathode of the fuel cell and opens the inlet opening / closing portion. Control for supplying the cathode gas to the cathode such that the inside of the cathode of the fuel cell has a high pressure exceeding atmospheric pressure;
Thereafter, by closing the inlet opening and closing part in a state where the outlet opening and closing part is closed, the control to make the interior of the cathode of the fuel cell exceed atmospheric pressure,
Thereafter, in the state where the cathode gas is present at the cathode of the fuel cell, the anode gas is supplied to the anode, and the fuel cell and the power consuming unit are electrically connected, Implements control to reduce the oxygen concentration inside the cathode from before the power consumption while suppressing an excessive increase in the open circuit voltage of the fuel cell by consuming the power generated in the battery at the power consuming unit. Fuel cell system.   6. The fuel cell system according to claim 5, wherein after the control for reducing the oxygen concentration inside the cathode of the fuel cell than before power consumption, the inside of the cathode of the fuel cell exceeds atmospheric pressure.   7. The outlet opening / closing part according to claim 1, wherein the outlet opening / closing portion is a check valve provided on an outlet side of the cathode of the fuel cell, and the check valve is connected to the cathode of the fuel cell. A fuel cell system that discharges the cathode off-gas discharged in the direction of being discharged from the cathode and prevents the reverse flow.   7. The cathode gas transport source for supplying the cathode gas to the cathode of the fuel cell is provided on the inlet side of the cathode of the fuel cell according to claim 1, A fuel cell system provided in the cathode gas transfer source. A fuel cell having an anode and a cathode; an anode gas passage for supplying an anode gas that may contain CO to the anode of the fuel cell; and an anode gas passage provided upstream of the anode of the fuel cell. A CO reduction section for reducing the concentration of CO contained; a cathode gas passage for supplying a cathode gas containing oxygen to the cathode of the fuel cell; and an inlet opening / closing for opening and closing an inlet side of the cathode of the fuel cell A fuel cell system comprising: a portion; an outlet opening / closing portion for opening / closing the cathode outlet side of the fuel cell; and a control portion for controlling at least the inlet opening / closing portion and the outlet opening / closing portion.
When stopping the operation of the fuel cell system,
The controller is
The inlet opening / closing part and the outlet opening / closing part of the cathode of the fuel cell are closed to seal the cathode, the cathode gas is present at the cathode of the fuel cell, and the anode is at the anode In the state where the gas is supplied and the fuel cell and the power consuming unit are electrically connected, the power consumption of the fuel cell is consumed by the power consuming unit, so that the open circuit voltage of the fuel cell is excessive. A fuel cell system that performs control to reduce the oxygen concentration inside the cathode more than before power consumption while suppressing a significant increase. A fuel cell having an anode and a cathode; an anode gas passage for supplying an anode gas that may contain CO to the anode of the fuel cell; and an anode gas passage provided upstream of the anode of the fuel cell. A CO reduction section for reducing the concentration of CO contained; a cathode gas passage for supplying a cathode gas containing oxygen to the cathode of the fuel cell; and an inlet opening / closing for opening and closing an inlet side of the cathode of the fuel cell A fuel cell system comprising: a portion; an outlet opening / closing portion for opening / closing the cathode outlet side of the fuel cell; and a control portion for controlling at least the inlet opening / closing portion and the outlet opening / closing portion.
When stopping the operation of the fuel cell system,
The controller is
In the state where the outlet opening / closing part of the cathode of the fuel cell is closed and the inlet opening / closing part is opened, the cathode is placed on the cathode so that the pressure inside the cathode of the fuel cell exceeds the atmospheric pressure to the high pressure side. Control for supplying cathode gas;
Control that causes the inside of the cathode to have a high pressure exceeding atmospheric pressure by closing the inlet opening / closing part in a state where the outlet opening / closing part is closed;
Thereafter, in the state where the cathode gas is present at the cathode of the fuel cell, the anode gas is supplied to the anode, and the fuel cell and the power consuming unit are electrically connected, The power consumption unit consumes the power generated in the battery, thereby suppressing an excessive increase in the open circuit voltage of the fuel cell and controlling the oxygen concentration inside the cathode to be lower than that before power consumption. Fuel cell system.

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