JP2009129879A - FUEL CELL SYSTEM AND CONTROL METHOD FOR FUEL CELL SYSTEM - Google Patents

Abstract

To reduce or prevent the deterioration of a membrane electrode assembly in reducing or removing residual hydrogen when a fuel cell is stopped.
In a residual hydrogen reduction process, a control unit 50 seals first and second anode sealing valves V1, V2, increases a discharge amount of a refrigerant pump P3, and circulates a refrigerant pipe 310. Increase the flow rate. The control unit 50 maintains the increased refrigerant flow rate until the difference between the initial refrigerant temperature Ti and the refrigerant temperature Tc detected via the temperature sensor 52 becomes less than the determination value Tr. As a result, the internal temperature of the fuel cell 10 is lowered, the water vapor present in the anode is condensed to form water droplets, the membrane electrode assembly is sufficiently wet, and the deterioration of the membrane electrode assembly during the subsequent current sweep is reduced. Or it can be prevented.
[Selection] Figure 1

Description

  The present invention relates to a fuel cell system and a fuel cell system control method when the fuel cell is stopped.

  In a fuel cell system, it is known that hydrogen remaining on the anode reacts with an oxidizing gas and causes an electromotive reaction even after the operation of the fuel cell is stopped, that is, after supply of fuel gas to the fuel cell is stopped. Since the electric power generated by this electromotive reaction is not consumed by the external load, the potential difference between the anode and the cathode of the membrane electrode assembly increases, and there is a problem that the electrolyte membrane and the catalyst deteriorate due to the high potential.

In order to solve this problem, for example, a technique for consuming residual hydrogen remaining in the anode when the operation of the fuel cell is stopped is known (for example, Patent Document 1).
JP 2006-134741 A

  However, since the residual hydrogen consumption process is generally performed in an environment where the hydrogen concentration or hydrogen amount after the operation is low, the hydrogen concentration distribution on the anode side of the membrane electrode assembly is not uniform. Therefore, in a part of the membrane electrode assembly, hydrogen contributing to the electromotive reaction is insufficient, carbon constituting the electrolyte membrane and the catalyst layer is consumed for the electromotive reaction, and the electrolyte membrane and the catalyst layer are deteriorated. There was a problem.

  The present invention has been made to solve at least a part of the above-described problems, and an object of the present invention is to reduce or prevent deterioration of a membrane electrode assembly in reducing or removing residual hydrogen when the fuel cell is stopped. And

  In order to solve at least a part of the above problems, the present invention adopts the following various aspects.

  A first aspect of the present invention provides a fuel cell system. According to a first aspect of the present invention, there is provided a fuel cell comprising a membrane electrode assembly, a residual hydrogen reduction processing means for reducing or removing residual hydrogen at an anode of the fuel cell when the fuel cell is stopped, and the residual hydrogen Wet maintaining means for keeping the membrane electrode assembly of the fuel cell in a wet state during the reduction process.

  According to the first aspect of the present invention, the membrane electrode assembly of the fuel cell can be kept in a wet state during the residual hydrogen reduction treatment, so that when the residual hydrogen is reduced or removed when the fuel cell is stopped, Deterioration of the electrode assembly can be reduced or prevented.

  In the first aspect of the present invention, the residual hydrogen reduction treatment is performed by sweeping a current from the fuel cell, and the wetness maintaining means reduces the internal temperature of the fuel cell to reduce the membrane electrode. The joined body may be maintained in a wet state. In this case, when the internal temperature decreases, the water vapor inside the fuel cell is condensed in the membrane electrode assembly, and the membrane electrode assembly can be in a sufficiently wet state.

  In the first aspect of the present invention, the wetness maintaining means includes a cooling means for circulating the refrigerant to cool the fuel cell, and increases the refrigerant circulation amount by the cooling means to increase the inside of the fuel cell. The temperature may be lowered. In this case, the internal temperature of the fuel cell can be lowered by increasing the refrigerant circulation rate.

  The first aspect of the present invention further includes an oxidizing gas supply device for supplying an oxidizing gas to the cathode of the fuel cell, wherein the wetness maintaining means increases the supply amount of the oxidizing gas by the oxidizing gas supply device. The internal temperature of the fuel cell may be lowered. In this case, the internal temperature of the fuel cell can be lowered by increasing the amount of oxidizing gas.

  In the first aspect of the present invention, the wetness maintaining means includes a wet gas supply device for supplying a wet gas to the anode of the fuel cell, and the wetness maintenance means supplies the wet gas by the wet gas supply device. By doing so, the membrane electrode assembly may be maintained in a wet state. In this case, the membrane electrode assembly can be maintained in a wet state by increasing the amount of water vapor in the fuel cell.

  The second aspect of the present invention provides a control method for a fuel cell system when the fuel cell is stopped. According to a second aspect of the present invention, the membrane electrode assembly of the fuel cell is maintained in a wet state, and residual hydrogen in the anode of the fuel cell is reduced.

  According to the second aspect of the present invention, advantages similar to those of the first aspect of the present invention can be obtained. The second aspect of the present invention can be implemented in various aspects in the same manner as the first aspect of the present invention. Furthermore, the second aspect of the present invention can also be realized as a computer program recorded on a computer-readable medium such as a computer program, CD, DVD, or HDD.

  Hereinafter, a fuel cell system according to the present invention will be described based on examples with reference to the drawings.

First embodiment:
FIG. 1 is an explanatory diagram schematically showing the configuration of the fuel cell system according to the first embodiment. The fuel cell system FC1 according to the first embodiment includes a fuel cell 10, a hydrogen source 20, an oxidizing gas blower P2, a heat exchanger 30, a load 40, and a control unit 50.

  The fuel cell 10 has an anode supplied with fuel gas and a cathode supplied with oxidizing gas. In this embodiment, a polymer electrolyte fuel cell is used, and the fuel cell 10 includes a membrane electrode assembly (MEA) having an anode catalyst layer and a cathode catalyst layer on each surface of the electrolyte membrane. It has. In addition to the anode catalyst layer and the cathode catalyst layer, an anode gas diffusion layer and a cathode gas diffusion layer may be provided.

  The electrolyte layer can be formed of a solid polymer electrolyte membrane, for example, a proton conductive ion exchange membrane made of a fluororesin containing perfluorocarbon sulfonic acid. Each catalyst layer includes a catalyst that promotes an electrochemical reaction, such as platinum or an alloy made of platinum and another metal. Each catalyst layer may be formed by being applied to the surface of the electrolyte layer, or may be formed integrally with each gas diffusion layer by supporting a catalyst metal on each gas diffusion layer. For each gas diffusion layer, a member having conductivity and gas permeability, for example, a carbon porous body and carbon paper can be used.

  The fuel cell 10 includes a fuel gas supply unit 10a and a fuel off-gas discharge unit 10b at the anode, and an oxidation gas supply unit 10c and an oxidation off-gas discharge unit 10d at the cathode. The fuel cell 10 further includes a refrigerant supply unit 10e and a refrigerant discharge unit 10f.

  The hydrogen source 20 is a hydrogen storage unit for supplying hydrogen as a fuel gas, and a high-pressure hydrogen tank is used in this embodiment. In addition, a hydrogen storage alloy, a hydrogen storage unit using carbon nanotubes, or a hydrogen storage unit that stores liquid hydrogen may be used.

  The fuel gas supply unit 10 a of the fuel cell 10 and the hydrogen source 20 are connected by a fuel gas supply pipe 110. The fuel gas supply pipe 110 is provided with a pressure control valve 21, a first anode sealing valve V 1, and a pressure sensor 51. The pressure control valve 21 adjusts the pressure of the fuel gas supplied from the hydrogen source 20 to the fuel cell 10 to a predetermined pressure. The first anode sealing valve V1 allows the fuel gas to be supplied to the fuel cell 10 when the valve is open, and stops the supply of the fuel gas to the fuel cell 10 when the valve is closed.

  A fuel off gas discharge pipe 111 is connected to the fuel off gas discharge portion 10 b of the fuel cell 10. The fuel off-gas discharge pipe 111 is provided with a second anode sealing valve V2. The second anode sealing valve V2 allows the fuel off gas to be discharged from the fuel cell 10 in the open state, and stops the fuel off gas from the fuel cell 10 in the closed state. A fuel gas circulation pipe 112 is connected to the downstream part of the first anode sealing valve V1 in the fuel gas supply pipe 110 and the upstream part of the second anode sealing valve V2 in the fuel off-gas discharge pipe 111. Therefore, it is possible to re-inject the fuel off gas to the anode. The fuel gas circulation pipe 112 is provided with a fuel gas circulation pump P <b> 1 for reintroducing the fuel off gas flowing from the fuel off gas discharge pipe 111 into the fuel gas supply pipe 110.

  An oxidizing gas supply pipe 120 is connected to the oxidizing gas supply unit 10 c of the fuel cell 10, and the oxidizing gas blower P <b> 2 and the fuel cell 10 are connected via the oxidizing gas supply pipe 120. An oxidizing off-gas discharge pipe 121 is connected to the oxidizing off-gas discharge unit 10 d of the fuel cell 10. The oxidizing off gas exhaust pipe 121 is provided with a cathode valve V3 used for adjusting the cathode pressure in cooperation with the oxidizing gas blower P2.

  An output terminal (not shown) of the fuel cell 10 is connected to a load 40 used when reducing or removing the residual hydrogen concentration or residual hydrogen amount at the anode, that is, at the time of power generation for consuming residual hydrogen at the anode. A switch 53 for connecting or disconnecting the load is disposed between the terminal of the fuel cell 10 and the load 40. The load 40 may be an auxiliary machine for operating the fuel cell 10, for example, an oxidizing gas blower P2. Further, a secondary battery that stores the generated electric power instead of the auxiliary machine may be connected.

  The refrigerant supply unit 10 e and the refrigerant discharge unit 10 f of the fuel cell 10 and the heat exchanger 30 are connected via a refrigerant pipe 310. A refrigerant pipe 310 between the refrigerant discharge part 10f of the fuel cell 10 and the heat exchanger 30 is provided with a temperature sensor 52 for detecting the refrigerant temperature and a refrigerant pump P3 for circulating the refrigerant in the refrigerant pipe 310. Has been.

  The control unit 50 controls the movement of the fuel cell system FC1 according to the input request output, and includes a CPU, a memory, and an input / output interface (not shown). The controller 50 is connected to the first and second anode sealing valves V1 and V2, the cathode valve V3, the pressure sensor 51, the temperature sensor 52, the switch 53, the fuel gas circulation pump P1, and the oxidation via an input / output interface (not shown). A gas blower P2 and a refrigerant pump P3 are connected to each other via a control signal line.

  The operation of the fuel cell system FC1 will be briefly described. The high-pressure hydrogen stored in the hydrogen source 20 is depressurized to a predetermined pressure by the pressure control valve 21, and then supplied to the anode of the fuel cell 10 through the fuel gas supply pipe 110 and the fuel gas supply unit 10a. During normal operation, the first anode sealing valve V1 and the second anode sealing valve V2 are opened and closed by the controller 50, respectively. Of the fuel gas supplied into the fuel cell via the fuel gas supply unit 10a, the fuel off-gas (anode off-gas) including the fuel gas not subjected to the electromotive reaction is supplied to the fuel off-gas discharge unit 10b and the fuel off-gas discharge pipe. It flows to the fuel gas circulation pipe 112 through a part of 111. The fuel off-gas that has flowed to the fuel gas circulation pipe 112 is led to the fuel gas supply pipe 110 by the fuel gas circulation pump P1, and is reintroduced into the fuel cell 10 together with hydrogen from the hydrogen source.

  Note that a further valve may be provided immediately downstream of the fuel off-gas discharge unit 10b, and during normal operation, the valve may be closed to operate the fuel off-gas within the fuel cell 10. . In this case, the valve and the second anode sealing valve V2 are periodically opened, and the fuel offgas having a high impurity concentration is released into the atmosphere via the fuel offgas discharge pipe 111. When the fuel off gas is stopped and operated within the fuel cell 10, the second anode sealing valve V2 may be in either the valve open state or the valve closed state.

  The atmosphere (air) taken in by the oxidizing gas blower P2 is supplied to the cathode of the fuel cell 10 through the oxidizing gas supply pipe 120 and the oxidizing gas supply unit 10c. The cathode pressure during operation of the fuel cell 10 can be adjusted by adjusting the discharge amount of the oxidizing gas blower P2 and the valve opening angle of the cathode valve V3.

  The hydrogen supplied to the anode is separated into hydrogen ions (protons) and electrons by the anode catalyst layer, the hydrogen ions move to the cathode through the membrane electrode assembly, and the electrons pass through the external circuit to the cathode catalyst layer. Move to. The hydrogen ions that have moved to the cathode react with oxygen supplied to the cathode and electrons that have passed through the external circuit in the cathode catalyst layer, thereby generating water. By this series of reactions, a current for driving the load can be obtained.

  The refrigerant in the refrigerant pipe 310 takes away some of the heat generated in the fuel cell 10 due to the electromotive reaction and releases part of the heat in the heat exchanger 30. That is, the refrigerant is circulated between the fuel cell 10 and the heat exchanger 30 by the refrigerant pump P3, whereby the fuel cell 10 is cooled (or maintained) to a predetermined temperature.

  The residual hydrogen reduction process in the fuel cell system FC1 will be described with reference to FIGS. FIG. 2 is a flowchart showing a processing routine executed in the residual hydrogen reduction processing. FIG. 3 is an explanatory diagram schematically showing the internal state of the fuel cell before the start of the residual hydrogen reduction process. FIG. 4 is an explanatory view schematically showing the state inside the fuel cell after performing the wet process in the residual hydrogen reduction process. FIG. 5 is an explanatory diagram schematically showing the state inside the fuel cell after execution of the current sweep process in the residual hydrogen reduction process.

  The residual hydrogen reduction process is performed when the operation of the fuel cell 10 in the fuel cell system FC1 is stopped, and is generally performed in the fuel cell system FC1 in which a so-called intermittent operation is performed. The controller 50 waits until the required output becomes less than the reference required output (step S100: No), and when the required output becomes less than the reference required output (step S100: Yes), the first anode sealing valve V1 and the second The anode sealing valve V2 is closed. Further, the control unit 50 operates the fuel gas circulation pump P1. As a result, the anode of the fuel cell 10 is shut off from the outside, and the anode gas discharged from the anode circulates and flows in the circulation system formed by the fuel gas circulation pipe 112. The reference required output means, for example, a required output (required power) that does not require operation of the fuel cell 10 and can be supplied by other power storage means such as a secondary battery. That is, it is a required output capable of stopping the operation of the fuel cell 10.

  At this time, as shown in FIG. 3, the inside of the fuel cell 10 is in a state where oxygen is present on the cathode side and residual hydrogen is present on the anode side. The electrolyte membrane 100, the anode catalyst layer 100a, and the cathode catalyst layer 100c forming the membrane electrode assembly are in a normal wet state.

  When the first and second anode sealing valves V1 and V2 are sealed, the control unit 50 increases the coolant flow rate and detects the coolant temperature, and records it as the initial coolant temperature Ti (step S120). Specifically, the control unit 50 increases the discharge amount of the refrigerant pump P3 to increase the flow rate of the refrigerant circulating in the refrigerant pipe 310, and sets the refrigerant temperature detected via the temperature sensor 52 as the initial refrigerant temperature Ti. Store in memory.

  The control unit 50 stands by until the difference between the initial refrigerant temperature Ti and the refrigerant temperature Tc detected via the temperature sensor 52 becomes less than the determination value Tr (step S130: No). Here, the determination value Tr is a temperature difference required for water vapor present at the anode of the fuel cell 10 to condense into water droplets. As shown in FIG. 4, the water vapor condenses on the membrane electrode assembly (mainly the anode catalyst layer 100 a), and the membrane electrode assembly is sufficiently wetted as shown as the wet part 102. As the determination value Tr, a determination temperature may be used instead of the temperature difference. For example, the determination temperature may be a temperature at which condensation of water vapor can be expected with reference to the operating temperature during normal fuel cell operation.

  When the difference between the initial refrigerant temperature Ti and the refrigerant temperature Tc is smaller than the determination value Tr (step S130: Yes), the controller 50 returns the refrigerant flow rate to the normal flow rate (step S140). Specifically, the control unit 50 returns the discharge amount of the refrigerant pump P3 to the normal discharge amount.

  The controller 50 increases the discharge amount of the oxidizing gas blower P2 and adjusts the cathode valve V3 to a closed state or an appropriate valve opening state, thereby increasing the cathode pressure Pc to a predetermined pressure (step S150). As a result, as shown in FIG. 4, the amount of oxidizing gas that moves from the cathode to the anode via the membrane electrode assembly is increased (so-called crossover amount can be increased). The hydrogen concentration can be reduced. Further, as the amount of oxidizing gas present in the anode increases, the same gas species gradually exists on both sides (anode and cathode side) of the membrane electrode assembly.

  The control unit 50 closes the switch 53, connects the terminal of the fuel cell 10 and the load 40, and sweeps current from the fuel cell 10 (step S160). As a result, an electromotive reaction occurs, and the hydrogen remaining on the anode is consumed. Therefore, together with the crossover of the oxidizing gas from the cathode, the same gas species exists on both sides (anode and cathode side) of the membrane electrode assembly, and the electromotive reaction gradually stops. Therefore, it is possible to suppress or prevent partial battery formation and local high voltage generation that cause deterioration of the membrane electrode assembly.

  In general, the amount of hydrogen remaining on the anode is small when the fuel cell 10 is stopped, and a portion with a high hydrogen concentration and a portion with a low hydrogen concentration are mixed on the membrane electrode assembly, and the hydrogen distribution is not uniform. Therefore, in the conventional configuration, at the time of the current sweep, carbon constituting the anode catalyst layer 100a and the electrolyte membrane 100 is consumed in place of the hydrogen that does not exist in the portion where the hydrogen concentration is low.

  However, in this embodiment, by reducing the internal temperature of the fuel cell 10, the water vapor in the anode is condensed, and the anode catalyst layer 100a and the electrolyte membrane 100 are kept in a sufficiently wet state as shown in FIG. Yes. As a result, the anode catalyst layer 100a is mainly in a sufficiently wet state, so that even in a portion where the amount of hydrogen is small, water is decomposed and protons are generated as shown in FIG. As a result, consumption of carbon constituting the anode catalyst layer 100a and the electrolyte membrane 100, that is, deterioration of the membrane electrode assembly can be suppressed or prevented.

  The control unit 50 continues the current sweep until the anode pressure Pa detected by the pressure sensor 51 becomes less than the determination pressure Parf (step S170: No), and when the anode pressure Pa becomes less than the determination pressure Paref (step S170: Yes). ), The switch 53 is opened to stop the current sweep (step S180). Here, the determination pressure Parf is the pressure of the anode in a state where the hydrogen concentration (or residual hydrogen amount) in the anode is sufficiently low (small). That is, based on the pressure, it is determined whether or not the amount of residual hydrogen at the anode has become sufficiently small or less than a predetermined amount.

  The controller 50 reduces the discharge amount of the oxidizing gas blower P2, adjusts the cathode valve V3 to a closed state or an appropriate valve opening state, and changes the cathode pressure Pc to a normal pressure (step S190). This processing routine ends.

  As described above, according to the fuel cell system FC1 according to the present embodiment, prior to the current sweep for consuming the residual hydrogen remaining in the anode, the membrane electrode assembly (electrolyte membrane and catalyst layer) during the current sweep. ) To maintain a wet state. Specifically, by lowering the temperature of the fuel cell 10 (anode), water vapor present in the anode is condensed to sufficiently wet the membrane electrode assembly. As a result, even in a portion where the hydrogen concentration (hydrogen distribution) is low, only water is consumed in the electromotive reaction, and consumption of carbon constituting the anode catalyst and the membrane electrode assembly, that is, the electrolyte membrane and the membrane electrode junction. Deterioration of the body can be suppressed or prevented.

  In addition, the wet maintenance in a present Example means the process for maintaining the wet state calculated | required in order to suppress or prevent deterioration of a membrane electrode assembly during a hydrogen reduction process, and continues during an electric sweep. Thus, the membrane / electrode assembly may be maintained in a wet state, or the membrane / electrode assembly may be brought into a sufficiently wet state before electrical sweeping and terminated. The sufficiently wet state means a state where deterioration of the membrane electrode assembly can be reduced or prevented in consideration of the amount of water consumed during the hydrogen reduction treatment.

Second embodiment:
A fuel cell system FC2 according to the second embodiment will be described. FIG. 6 is an explanatory diagram schematically showing the configuration of the fuel cell system FC2 according to the second embodiment. The fuel cell system FC2 according to the second embodiment is structurally different from the fuel cell system FC1 according to the first embodiment in that a humidification source 60 is provided. The remaining configuration of the fuel cell system FC2 according to the second embodiment is the same as that of the fuel cell system FC1 according to the first embodiment, and therefore the configuration of the fuel cell system FC1 according to the first embodiment is similar to that of the fuel cell system FC1 according to the first embodiment. The same reference numerals as those in FIG.

  In the fuel cell system FC2 according to the present embodiment, when performing the wetting process in the residual hydrogen reduction process, the control unit 50 supplies the humidified gas from the humidifying source 60 to the anode instead of increasing the refrigerant flow rate. By increasing the amount of water vapor at the anode, the amount of water condensed on the membrane electrode assembly is increased, thereby making the membrane electrode assembly sufficiently wet.

  According to the second embodiment, the membrane electrode assembly in the anode, that is, mainly the anode catalyst layer 100a and the electrolyte membrane 100 is maintained in a sufficiently wet state during the hydrogen reduction process without increasing the refrigerant flow rate. be able to. In addition, since the humidified gas is supplied, the wet state of the membrane electrode assembly can be predicted more easily, and the wet state management accuracy of the membrane electrode assembly can be improved. Further, the membrane / electrode assembly can be maintained in a wet state by continuously executing it during current sweeping (when hydrogen is consumed).

Other examples:
(1) In each of the above embodiments, the auxiliary machine is driven at the time of the current sweep, but a storage / discharge unit such as a secondary battery or a capacitor may be used instead of the auxiliary machine. That is, the current sweep is realized by connecting the charging / discharging means having a low charge level to the fuel cell 10. Further, the auxiliary machine is not limited to the oxidizing gas blower P2, and may be other auxiliary machines such as the fuel gas circulation pump P1. Furthermore, the current obtained by the current sweep may be used as all or part of the current for operating the auxiliary machine.

(2) In the first embodiment, the temperature of the fuel cell 10 is decreased by increasing the refrigerant flow rate, but the temperature of the fuel cell 10 is decreased by increasing the amount of oxidizing gas supplied by the oxidizing gas blower P2. May be. Since the cathode and the anode are adjacent to each other through the membrane electrode assembly, heat of the anode may be taken away by the oxidizing gas flowing through the cathode to lower the anode temperature. When the anode temperature reduction process is continued even during the current sweep, the current sweep may be assigned to a part or all of the current that drives the oxidizing gas blower P2.

(3) In the above embodiment, a decrease in the internal temperature of the fuel cell 10 due to the condensation of water vapor on the membrane electrode assembly is detected on the basis of the refrigerant temperature. You may determine the fall of the internal temperature of the fuel cell 10 by the time from refrigerant | coolant amount increase. Further, a predetermined time may be corrected based on a plurality of parameters such as the fuel cell temperature, the ambient temperature, and the operation time before stopping.

(4) As another method of reducing the internal temperature of the fuel cell 10, for example, the fuel gas temperature may be reduced immediately before being introduced into the fuel cell 10. Specifically, it is realized by providing a heat exchanger in the vicinity of the fuel gas supply unit 100a.

(5) In the above embodiment, it is determined whether or not the amount of residual hydrogen has been sufficiently reduced by detecting the anode pressure Pa, but it may also be determined based on the time from the current sweep. In other words, under general conditions, a time may be determined in advance from the current sweep until a reduction in the residual hydrogen amount of the anode is expected, and the determination may be performed based on the predetermined time. Furthermore, a predetermined time may be corrected based on a plurality of parameters such as the fuel cell temperature, the ambient temperature, and the operation time before stopping during the residual hydrogen reduction process.

(6) The fuel cell systems FC1 and FC2 in the above embodiments can be mounted on a moving body such as an automobile or a two-wheeled vehicle, or used as a grounded fuel cell system with intermittent operation.

  As mentioned above, although this invention was demonstrated based on the Example and the modification, Embodiment mentioned above is for making an understanding of this invention easy, and does not limit this invention. The present invention can be changed and improved without departing from the spirit and scope of the claims, and equivalents thereof are included in the present invention.

It is explanatory drawing which shows typically the structure of the fuel cell system which concerns on a 1st Example. It is a flowchart which shows the process routine performed in the case of a residual hydrogen reduction process. It is explanatory drawing which shows typically the state inside a fuel cell before the residual hydrogen reduction process start. It is explanatory drawing which shows typically the state inside the fuel cell after execution of the wet process in a residual hydrogen reduction process. It is explanatory drawing which shows typically the state inside the fuel cell after execution of the current sweep process in a residual hydrogen reduction process. It is explanatory drawing which shows typically the structure of the fuel cell system which concerns on a 2nd Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Fuel cell 10a ... Fuel gas supply part 10b ... Fuel off gas discharge part 10c ... Oxidation gas supply part 10d ... Oxidation off gas discharge part 10e ... Refrigerant supply part 10f ... Refrigerant discharge part 20 ... Hydrogen source 21 ... Pressure control valve 30 ... Heat Exchanger 40 ... Load 50 ... Control unit 51 ... Pressure sensor 52 ... Temperature sensor 53 ... Switch 60 ... Humidification source 100 ... Electrolyte membrane 100a ... Anode catalyst layer 100c ... Cathode catalyst layer 102 ... Wetting unit 110 ... Fuel gas supply pipe 111 ... Fuel off-gas discharge pipe 112 ... Fuel gas circulation pipe 120 ... Oxidation gas supply pipe 121 ... Oxidation off-gas discharge pipe 310 ... Refrigerant pipe FC1 ... Fuel cell system according to the first embodiment FC2 ... Fuel cell according to the second embodiment System P1 ... Fuel gas circulation pump P2 ... Oxidizing gas blower P3 ... Refrigerant pump V1 ... First anode Sealing valve V2 ... Second anode sealing valve V3 ... Cathode valve

Claims (6)

A fuel cell system,
A fuel cell comprising a membrane electrode assembly;
Residual hydrogen reduction processing means for reducing or removing residual hydrogen at the anode of the fuel cell when the fuel cell is shut down;
A fuel cell system comprising a wetness maintaining means for keeping the membrane electrode assembly of the fuel cell in a wet state during the residual hydrogen reduction process. The fuel cell system according to claim 1,
The residual hydrogen reduction process is performed by sweeping current from the fuel cell,
The wetness maintaining means is a fuel cell system which maintains the membrane electrode assembly in a wet state by lowering the internal temperature of the fuel cell. The fuel cell system according to claim 2, wherein
The wetness maintaining means includes a cooling means for circulating the refrigerant to cool the fuel cell, and increases the refrigerant circulation amount by the cooling means to lower the internal temperature of the fuel cell. The fuel cell system according to claim 2, further comprising:
An oxidizing gas supplier for supplying an oxidizing gas to the cathode of the fuel cell;
The wetness maintaining means increases the supply amount of the oxidizing gas by the oxidizing gas supply device to lower the internal temperature of the fuel cell. The fuel cell system according to claim 1,
The wetness maintaining means includes a wet gas supply device that supplies a wet gas to the anode of the fuel cell, and the wetness maintenance means supplies the wet gas by the wet gas supply device to thereby form the membrane electrode assembly. A fuel cell system that maintains a wet state. A method for controlling a fuel cell system when a fuel cell is stopped,
Maintaining the fuel cell membrane electrode assembly in a wet state;
A control method for reducing residual hydrogen in the anode of the fuel cell.

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