JP2012069440A - Operation stop method of fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an operation stop method of a full cell system capable of suppressing fuel cell deterioration as much as possible with a simple and compact configuration.SOLUTION: An operation stop method of a fuel cell system 10 comprises: a first step of making a fuel cell stack 12 generate power while supplying a hydrogen gas and air to the fuel cell stack 12; and a second step of stopping the supply of the hydrogen gas when detecting a stop command of the fuel cell stack 12, and making the fuel cell stack 12 generate power while supplying the air to the fuel cell stack 12. When a fuel gas pressure reaches a lower limit setting value based on an anode-side pressure actually measured in advance, the power generation of the fuel cell is stopped in the second step.

Description

  The present invention relates to a method for shutting down a fuel cell system including a fuel cell that generates electricity by an electrochemical reaction between an oxidant gas and a fuel gas.

  In a fuel cell, a fuel gas (a gas mainly containing hydrogen, for example, hydrogen gas) and an oxidant gas (a gas mainly containing oxygen, for example, air) are supplied to an anode electrode and a cathode electrode to be electrochemical. It is a system that obtains direct-current electric energy by reacting with. This system is incorporated in a fuel cell vehicle for in-vehicle use as well as stationary use.

  For example, in a polymer electrolyte fuel cell, an electrolyte membrane / electrode structure (MEA) provided with an anode electrode and a cathode electrode on both sides of an electrolyte membrane made of a polymer ion exchange membrane is sandwiched between a pair of separators. Yes. A fuel gas passage for supplying fuel gas to the anode electrode is formed between one separator and the electrolyte membrane / electrode structure, and between the other separator and the electrolyte membrane / electrode structure. Is formed with an oxidant gas flow path for supplying an oxidant gas to the cathode electrode.

  By the way, when the fuel cell is stopped, the supply of the fuel gas and the oxidant gas is stopped, but the fuel gas remains in the fuel gas flow channel, while the oxidant gas remains in the oxidant gas flow channel. ing. Therefore, especially when the stop period of the fuel cell becomes long, the fuel gas and the oxidant gas may permeate the electrolyte membrane, and the fuel gas and the oxidant gas may be mixed.

  Thus, for example, a fuel cell system disclosed in Patent Document 1 is known. As shown in FIG. 10, the fuel cell system includes a fuel cell 1, an anode gas supply line 2 and a cathode gas supply line 3 for supplying hydrogen gas and air to the fuel cell 1, and an anode outlet of the fuel cell 1. An anode circulation line 2a and a cathode circulation line 3a for circulating the gas and the cathode outlet gas respectively upstream; a purge line 4 for purging the fuel cell 1 and each of the lines 2, 2a, 3 and 3a with an inert gas; And a shut-off means 5 for shutting off the output electric circuit of the fuel cell 1 when the operation is stopped.

  The anode gas supply line 2 includes an inlet shutoff valve 6a and a blower 7a arranged in this order in an inlet pipe A1 connected to an anode side inlet of the fuel cell 1 from a hydrogen tank (not shown) which is a hydrogen storage device. ing. Further, a purge valve 6b and an outlet shut-off valve 6c are arranged in series in this order in an outlet line A2 connected to a fuel regeneration device (not shown) from the anode side outlet of the fuel cell 1.

  The anode gas supply line 2 opens the inlet shut-off valve 6a, the outlet shut-off valve 6c, and the purge valve 6b during the operation of the fuel cell 1, and the hydrogen gas sent from the hydrogen tank is sent to the fuel cell 1 through the blower 7a. To the anode electrode 1A.

  The cathode gas supply line 3 includes an inlet shutoff valve 6d and a blower 7b arranged in this order in an inlet pipe C1 connected to a cathode side inlet of the fuel cell 1 from an air tank (not shown) filled with compressed air. ing. In addition, an outlet shutoff valve 6e is provided in the outlet pipe C2 connected from the cathode side outlet of the fuel cell 1 to a generated water separator (not shown).

  The cathode gas supply line 3 opens the inlet shut-off valve 6d and the outlet shut-off valve 6e during the operation of the fuel cell 1, and the air sent from the air tank is supplied to the cathode 1C of the fuel cell 1 through the blower 7b. Supply.

  The anode circulation line 2a opens the circulation cutoff valve 6f when the inlet cutoff valve 6a and the outlet cutoff valve 6c of the anode gas supply line 2 are closed due to the shutdown of the fuel cell 1, and the fuel cell 1 The anode outlet gas is sucked by the blower 7 a and functions to circulate upstream of the fuel cell 1.

  On the other hand, the cathode circulation line 3 a opens the circulation cutoff valve 6 g when the inlet cutoff valve 6 d and the outlet cutoff valve 6 e of the cathode supply line 3 are closed due to the stop of the operation of the fuel cell 1. The cathode outlet gas functions to be sucked by the blower 7b and circulated upstream of the fuel cell 1.

  In this Patent Document 1, when the operation is stopped, the supply of the reaction gas to the cathode side is shut off by the inlet shut-off valve, the cathode side exhaust gas is circulated upstream via the circulation line, and the cell reaction in the fuel cell is continued. By consuming oxygen in the cathode side exhaust gas, an inert gas of nitrogen gas is used for purging the cathode side and the anode side in the fuel cell.

Japanese Patent Laid-Open No. 2004-22487

  In the above-mentioned Patent Document 1, the anode gas supply line 2 and the cathode gas supply line 3 are provided with an anode circulation line 2a and a cathode circulation line 3a for circulating the anode outlet gas and the cathode outlet gas of the fuel cell 1 respectively upstream. It has been. Furthermore, in the cathode circulation line 3a, a tank 8 which is a gas volume part is disposed in order to accumulate nitrogen gas which is an inert gas.

  Then, by continuing the cell reaction in the fuel cell 1 and consuming oxygen in the cathode side exhaust gas, an inert gas such as nitrogen gas is used for the cathode side and anode side purge in the fuel cell 1. Yes. For this reason, there exists a problem that the structure of the whole fuel cell system becomes complicated and enlarged, and cost increases.

  An object of the present invention is to solve this type of problem, and to provide a method for stopping the operation of a fuel cell system that can suppress deterioration of the fuel cell as much as possible with a simple and compact configuration. To do.

  The present invention relates to a fuel cell that generates electricity by an electrochemical reaction between an oxidant gas supplied to the cathode side and a fuel gas supplied to the anode side, and an oxidant gas supply device that supplies the oxidant gas to the fuel cell. The present invention relates to a method for stopping operation of a fuel cell system comprising a fuel gas supply device for supplying the fuel gas to the fuel cell.

  In this operation stop method, the supply of the fuel gas is stopped when the first step of generating the fuel cell while supplying the oxidant gas and the fuel gas to the fuel cell and the stop command of the fuel cell is detected. On the other hand, there is a second step of generating the fuel cell while supplying the oxidant gas to the fuel cell.

  In the second step, when the fuel gas pressure on the anode side is reduced to the lower limit set value based on the anode side pressure actually measured in advance, the power generation of the fuel cell is stopped.

  In this operation stop method, the lower limit set value is preferably an anode-side critical pressure at which the anode-side potential starts increasing when the fuel gas pressure is reduced.

  Further, in the second step, the operation stop method measures the anode side pressure, calculates the water vapor partial pressure, and subtracts the water vapor partial pressure from the anode side pressure to obtain the fuel gas pressure. preferable.

  Furthermore, in this operation stopping method, in the second step, it is preferable to supply the oxidant gas to the fuel cell with a low oxygen stoichiometry lower than the oxygen stoichiometry during normal power generation.

  In this operation stop method, it is preferable that the low oxygen stoichiometric oxidant gas is set to about 1.

  In the present invention, since electric power is generated by the fuel gas remaining in the fuel cell and the supplied oxidant gas, the hydrogen concentration of the fuel gas in the fuel cell is lowered. Therefore, hydrogen does not permeate from the anode side through the electrolyte membrane to the cathode side, and the reaction between the hydrogen and oxygen does not occur. For this reason, deterioration of the electrolyte membrane can be satisfactorily suppressed.

  Moreover, when the fuel gas pressure on the anode side is reduced to the lower limit set value based on the anode side pressure actually measured in advance, the power generation of the fuel cell is stopped. As a result, it is possible to prevent deterioration of the fuel cell without causing a rapid increase in the anode side potential due to a shortage of fuel gas. Accordingly, it is possible to suppress deterioration of the fuel cell as much as possible with a simple and compact configuration.

1 is a schematic configuration diagram of a fuel cell system in which an operation stop method according to an embodiment of the present invention is implemented. It is circuit explanatory drawing which comprises the said fuel cell system. It is a timing chart explaining the said operation stop method. It is a flowchart explaining the said operation stop method. It is explanatory drawing of the relationship between an anode side pressure and an anode side electric potential. FIG. 6 is an explanatory diagram of a relationship among the anode side pressure, the anode side potential, and a hydrogen gas temperature. It is operation | movement explanatory drawing of the said fuel cell system. It is operation | movement explanatory drawing of the said fuel cell system. It is explanatory drawing of the nitrogen substitution state in the said fuel cell system. 2 is an explanatory diagram of a fuel cell system disclosed in Patent Document 1. FIG.

  As shown in FIG. 1, a fuel cell system 10 in which an operation stop method according to an embodiment of the present invention is implemented includes a fuel cell stack 12 and an oxidant gas supply device that supplies an oxidant gas to the fuel cell stack 12. 14, a fuel gas supply device 16 that supplies fuel gas to the fuel cell stack 12, a battery (power storage device) 17 that can be connected to the fuel cell stack 12, and a controller 18 that controls the entire fuel cell system 10. With. The fuel cell system 10 is mounted on a fuel cell vehicle such as a fuel cell vehicle. The battery 17 can normally travel in a fuel cell vehicle, and has a voltage of about 20 A to about 500 V, for example, and a higher voltage and a higher power capacity than a 12 V power source 98 described later.

  The fuel cell stack 12 is configured by stacking a plurality of fuel cells 20. Each fuel cell 20 includes, for example, an electrolyte membrane / electrode structure (MEA) 28 in which a solid polymer electrolyte membrane 22 in which a perfluorosulfonic acid thin film is impregnated with water is sandwiched between a cathode electrode 24 and an anode electrode 26. .

  The cathode electrode 24 and the anode electrode 26 have a gas diffusion layer made of carbon paper or the like, and porous carbon particles carrying platinum alloy (or Ru or the like) on the surface are uniformly applied to the surface of the gas diffusion layer. And an electrode catalyst layer formed. The electrode catalyst layers are formed on both surfaces of the solid polymer electrolyte membrane 22.

  The electrolyte membrane / electrode structure 28 is sandwiched between the cathode side separator 30 and the anode side separator 32. The cathode side separator 30 and the anode side separator 32 are comprised by a carbon separator or a metal separator, for example.

  An oxidant gas flow path 34 is provided between the cathode side separator 30 and the electrolyte membrane / electrode structure 28, and a fuel gas is provided between the anode side separator 32 and the electrolyte membrane / electrode structure 28. A flow path 36 is provided.

  The fuel cell stack 12 communicates with each other in the stacking direction of the fuel cells 20 to supply an oxidant gas, for example, an oxidant gas inlet communication hole 38a for supplying an oxygen-containing gas (hereinafter also referred to as air), a fuel gas, For example, a fuel gas inlet communication hole 40a for supplying a hydrogen-containing gas (hereinafter also referred to as hydrogen gas), a cooling medium inlet communication hole (not shown) for supplying a cooling medium, and an oxidant gas outlet for discharging the oxidant gas A communication hole 38b, a fuel gas outlet communication hole 40b for discharging the fuel gas, and a cooling medium outlet communication hole (not shown) for discharging the cooling medium are provided.

  The oxidant gas supply device 14 includes an air pump 50 that compresses and supplies air from the atmosphere, and the air pump 50 is disposed in the air supply flow path 52. The air supply channel 52 is provided with a humidifier 54 that exchanges moisture and heat between the supply gas and the exhaust gas, and the air supply channel 52 is connected to the oxidant gas inlet of the fuel cell stack 12. It communicates with the communication hole 38a.

  The oxidant gas supply device 14 includes an air discharge channel 56 that communicates with the oxidant gas outlet communication hole 38b. The air discharge channel 56 communicates with a humidifying medium passage (not shown) of the humidifier 54, and is supplied to the fuel cell stack 12 from the air pump 50 through the air supply channel 52. A back pressure control valve 58 with an adjustable opening is provided for adjusting the pressure of the air. The back pressure control valve 58 is preferably a normally closed type (closed when not energized) back pressure valve.

  The air discharge channel 56 communicates with the dilution box 60. In the air supply flow path 52 and the air discharge flow path 56, on-off valves 61a and 61b are disposed in the vicinity of the oxidant gas inlet communication hole 38a and the oxidant gas outlet communication hole 38b.

  The fuel gas supply device 16 includes a hydrogen tank 62 that stores high-pressure hydrogen. The hydrogen tank 62 communicates with the fuel gas inlet communication hole 40 a of the fuel cell stack 12 via a hydrogen supply flow path 64. The hydrogen supply flow path 64 is provided with a shutoff valve 65 and an ejector 66. The ejector 66 supplies the hydrogen gas supplied from the hydrogen tank 62 to the fuel cell stack 12 through the hydrogen supply flow path 64 and exhaust gas containing unused hydrogen gas that has not been used in the fuel cell stack 12. Then, the gas is sucked from the hydrogen circulation path 68 and supplied again as fuel gas to the fuel cell stack 12.

  The off gas passage 70 communicates with the fuel gas outlet communication hole 40b. A hydrogen circulation path 68 communicates with the off gas flow path 70, and a dilution box 60 is connected to the off gas flow path 70 via a purge valve 72. A discharge flow path 74 is connected to the discharge port side of the dilution box 60, and a storage buffer 76 is disposed in the discharge flow path 74. An exhaust passage 78 is connected to the storage buffer 76.

  As shown in FIG. 2, one end of a bus line 80 is connected to the fuel cell stack 12, and the other end of the bus line 80 is connected to an inverter 82. A drive motor 84 for three-phase vehicle travel is connected to the inverter 82. Note that two bus lines 80 are substantially used, but are described as one bus line 80 in order to simplify the description. The same applies to the other lines described below.

  An FC contactor 86 is disposed on the bus line 80 and an air pump 50 is connected thereto. One end of a power line 88 is connected to the bus line 80, and the battery 17 is connected to the power line 88 via a DC / DC converter 90 and a battery conductor 92. The power line 88 is provided with a branch power line 94, and a 12 V power source 98 is connected to the branch power line 94 via a downverter (DC / DC converter) 96. Note that the 12V power source 98 only needs to have a voltage lower than that of the battery 17, and is not limited to 12V.

  As shown in FIG. 1, a pressure sensor 100 for detecting an anode side gas pressure (anode side pressure) in the hydrogen supply channel 64 in the vicinity of the fuel gas inlet communication hole 40 a of the fuel cell stack 12, A temperature detection sensor 102 for detecting the anode side gas temperature is provided.

  The operation of the fuel cell system 10 configured as described above will be described below.

  First, during operation of the fuel cell system 10, air is sent to the air supply passage 52 via the air pump 50 that constitutes the oxidant gas supply device 14. The air is humidified through the humidifier 54 and then supplied to the oxidant gas inlet communication hole 38 a of the fuel cell stack 12. This air is supplied to the cathode electrode 24 by moving along the oxidant gas flow path 34 provided in each fuel cell 20 in the fuel cell stack 12.

  The used air is exhausted from the oxidant gas outlet communication hole 38 b to the air exhaust flow path 56 and is sent to the humidifier 54 to humidify the newly supplied air, and then through the back pressure control valve 58. Introduced into the dilution box 60.

  On the other hand, in the fuel gas supply device 16, the shutoff valve 65 is opened so that the pressure is reduced from the hydrogen tank 62 by a pressure reducing valve (not shown), and then the hydrogen gas is supplied to the hydrogen supply flow path 64. This hydrogen gas is supplied to the fuel gas inlet communication hole 40 a of the fuel cell stack 12 through the hydrogen supply channel 64. The hydrogen gas supplied into the fuel cell stack 12 is supplied to the anode electrode 26 by moving along the fuel gas flow path 36 of each fuel cell 20.

  The used hydrogen gas is sucked into the ejector 66 from the fuel gas outlet communication hole 40b through the hydrogen circulation path 68, and is supplied again to the fuel cell stack 12 as fuel gas. Accordingly, the air supplied to the cathode electrode 24 and the hydrogen gas supplied to the anode electrode 26 react electrochemically to generate power.

  On the other hand, the hydrogen gas circulating in the hydrogen circulation path 68 is likely to contain impurities. For this reason, the hydrogen gas mixed with impurities is introduced into the dilution box 60 when the purge valve 72 is opened. This hydrogen gas is discharged to the storage buffer 76 after the hydrogen concentration is lowered by being mixed with the air off-gas.

  Next, a method for stopping the operation of the fuel cell system 10 will be described below along the timing chart shown in FIG. 3 and the flowchart shown in FIG.

  First, the hydrogen gas supply on the anode side is stopped in advance, and a discharge test is performed by drawing current while flowing air to the cathode side, and the hydrogen gas partial pressure (fuel gas pressure) on the anode side is determined to determine whether the hydrogen gas is insufficient. This is used as a reference, that is, a judgment reference for increasing the anode side potential (the unipolar potential of the anode electrode 26), and is reflected in the discharge control stop control described later.

  Actually, when a discharge test was performed using the fuel cell stack 12 incorporated in this embodiment, it was found that the hydrogen gas partial pressure P1 on the anode side and the anode side potential had the relationship shown in FIG. . For this reason, as long as the hydrogen gas partial pressure P1 is maintained at the lower limit set value P1L or more, the anode-side potential does not rapidly increase. This lower limit set value P1L is the anode-side critical pressure.

  The hydrogen gas partial pressure P1 is a value obtained by subtracting the water vapor partial pressure P3 from the anode side pressure P2. Therefore, the water vapor component P3 corresponding to the detected temperature is calculated from the map of the temperature and the water vapor partial pressure P3. P1 is calculated.

  FIG. 6 shows the relationship among the anode side pressure P2, the hydrogen gas temperature, and the anode side potential. A lower limit set value P1L of the hydrogen gas partial pressure P1 is set based on the anode side pressure P2L at which the anode side potential starts to rise rapidly (P2L−P3 = P1L).

  Therefore, in the fuel cell system 10 mounted on a fuel cell vehicle (not shown), when an ignition switch (not shown) is turned off, an operation stop process of the fuel cell system 10 is started (step S1 in FIG. 4).

  For example, after a predetermined time including a failure detection time has elapsed since the ignition switch was turned off, the discharge process is started (step S2). Specifically, the shutoff valve 65 is closed, while the back pressure control valve 58 is closed when the opening degree control is stopped (see FIG. 7).

  Further, the air pump 50 constituting the oxidant gas supply device 14 is considerably decelerated compared with that during normal operation, and supplies the oxygen stoichiometric gas in the oxidant gas at a low oxygen stoichiometry lower than that during normal power generation. To do. The low oxygen stoichiometry is set to around 1. Note that the air pump 50 may be driven at a rotational speed equivalent to that during normal operation as necessary. At this time, the oxygen stoichiometry is not limited to the low oxygen stoichiometry.

  On the other hand, the fuel cell stack 12 continues to generate power, and the generated voltage (FC voltage) is set to a higher voltage than during normal power generation, and the current (FC current) extracted from the fuel cell stack 12 It is set to a value that prevents hydrogen gas, which is a fuel gas, from passing through the molecular electrolyte membrane 22 and moving from the anode side to the cathode side. Here, in FIG. 2, the FC contactor 86 and the battery conductor 92 are turned on, and the electric power obtained when the fuel cell stack 12 generates power is stepped down by the DC / DC converter 90 and then charged to the battery 17. The

  As described above, in the fuel cell stack 12, low oxygen stoichiometric air is required, while power generation is performed in a state where the supply of hydrogen gas is stopped due to the shutoff of the shutoff valve 65. The power generated by the fuel cell stack 12 is discharged to the battery 17 (battery DCHG in FIG. 3). Accordingly, when the power generation voltage of the fuel cell stack 12 drops to a predetermined voltage, that is, the voltage N1 (V) that cannot be supplied to the battery 17 (substantially the same voltage as the voltage of the battery 17), the power generation is supplied only to the air pump 50. The

  Thereby, in the fuel cell stack 12, the hydrogen concentration on the anode side decreases, while the oxygen concentration on the cathode side decreases. Therefore, the air pump 50 is turned off and the battery conductor 92 is turned off.

  For this reason, as shown in FIG. 8, the fuel cell stack 12 is generated by the hydrogen gas and air remaining inside. The electric power generated by the power generation of the fuel cell stack 12 is stepped down through the downverter 96, and then charged to the 12V power source 98 (D / V DCHG). If necessary, the electric power is supplied to a radiator fan (not shown). Is supplied.

  While the discharge process is being performed, the controller 18 detects the anode side pressure P2 including the pressure of the hydrogen gas supplied to the fuel cell stack 12 via the pressure sensor 100 (step S3), and detects the temperature. A hydrogen gas temperature (anode side gas temperature) is detected via the sensor 102. The water vapor partial pressure P3 is calculated from the detected hydrogen gas temperature (step S4), and the water vapor partial pressure P1 is calculated by subtracting the water vapor partial pressure P3 from the detected anode side pressure P2.

  Further, it is determined whether or not the calculated hydrogen gas partial pressure P1 is equal to or lower than a lower limit set value P1L of the fuel gas pressure (step S5). When it is determined that the hydrogen gas partial pressure P1 is equal to or lower than the lower limit set value P1L (YES in step S5), the process proceeds to step S6 and the discharge process is completed. Specifically, the back pressure control valve 58 is once opened (atmospheric pressure), and the FC contactor 86 is turned off.

  In this case, in this embodiment, when the ignition switch is turned off, the back pressure control valve 58, the air pump 50, and the shutoff valve 65 are operated. Accordingly, in the fuel cell stack 12, power is generated by the hydrogen gas remaining in the fuel cell stack 12 and the low-oxygen stoichiometric air, and the generated power is supplied to the battery 17 and discharged.

  As a result, the hydrogen concentration decreases on the anode side in the fuel cell stack 12, and the oxygen concentration decreases and the nitrogen concentration increases on the cathode side. Therefore, high concentration nitrogen gas is generated on the cathode side as exhaust gas, and the nitrogen gas is supplied to the dilution box 60 and the storage buffer 76. On the other hand, on the anode side, a negative pressure state is caused by a decrease in the hydrogen concentration, and nitrogen gas permeates from the cathode side to the anode side through the solid polymer electrolyte membrane 22.

  Therefore, hydrogen does not permeate to the cathode side and the reaction between the hydrogen and oxygen does not occur, and in particular, deterioration of the solid polymer electrolyte membrane 22 can be satisfactorily suppressed. As a result, the fuel cell stack 12 and the gas piping connected to the fuel cell stack 12 can be filled with nitrogen gas, which is an inert gas, and the fuel cell 20 can be deteriorated with a simple and compact configuration. The effect that it becomes possible to suppress as much as possible is acquired.

  Moreover, in the present embodiment, the fuel cell stack 12 is generated with only the hydrogen and oxygen remaining in the fuel cell stack 12 in a state where the supply of air is stopped by turning off the air pump 50. (D / V DCHG in FIG. 3).

  Therefore, as shown in FIG. 9, when the fuel cell stack 12 is generated while supplying air via the air pump 50, the nitrogen replacement range in the system is up to the range B and the range C. On the other hand, when the power generation of the fuel cell stack 12 is performed after the air pump 50 is stopped, the replacement range by the nitrogen gas is expanded to the range A on the inlet side of the fuel cell stack 12. Thereby, even if the fuel cell system 10 is stopped for a relatively long period of time, there is an advantage that deterioration of the fuel cell 20 can be prevented as much as possible.

  Further, in the present embodiment, the correlation between the anode-side hydrogen gas partial pressure P1 and the anode-side potential is obtained, and the hydrogen gas partial pressure P1 is used as a criterion for avoiding the increase in the anode-side potential. When the hydrogen gas partial pressure P1 reaches the lower limit set value P1L based on the anode side pressure P2 actually measured in advance, the power generation of the fuel cell stack 12 is stopped.

  At that time, for example, it is conceivable to detect the cell voltage (FC voltage) of the fuel cell 20 and determine the stop timing of the discharge process based on the decrease in the cell voltage. However, factors that cause the cell voltage to decrease include an increase in anode-side potential and a decrease in cathode-side potential, and it may not be possible to determine which factor is responsible.

  Therefore, it is possible to prevent the deterioration of the fuel cell 20 without causing a rapid increase in the anode side potential due to the shortage of fuel gas by determining the increase in the anode side potential based on the hydrogen gas partial pressure P1. Is possible. For this reason, it becomes possible to suppress deterioration of the fuel cell 20 as much as possible with a simple and compact configuration.

  Moreover, in the present embodiment, the hydrogen gas partial pressure P1 is calculated in consideration of the water vapor partial pressure P3. As a result, the hydrogen gas partial pressure P1 can be consumed up to the lower limit, and the residual hydrogen can be reduced as much as possible.

DESCRIPTION OF SYMBOLS 10 ... Fuel cell system 12 ... Fuel cell stack 14 ... Oxidant gas supply device 16 ... Fuel gas supply device 17 ... Battery 18 ... Controller 20 ... Fuel cell 22 ... Solid polymer electrolyte membrane 24 ... Cathode electrode 26 ... Anode electrode 28 ... Electrolyte membrane / electrode structure 30, 32 ... Separator 34 ... Oxidant gas flow path 36 ... Fuel gas flow path 38a ... Oxidant gas inlet communication hole 38b ... Oxidant gas outlet communication hole 40a ... Fuel gas inlet communication hole 40b ... Fuel Gas outlet communication hole 50 ... Air pump 52 ... Air supply channel 54 ... Humidifier 56 ... Air discharge channel 58 ... Back pressure control valve 60 ... Dilution boxes 61a, 61b ... Open / close valve 62 ... Hydrogen tank 64 ... Hydrogen supply channel 65 ... shutoff valve 66 ... ejector 68 ... hydrogen circulation path 70 ... off-gas flow path 72 ... purge valve 74 ... discharge flow path 76 ... storage buffer 78 Exhaust flow path 86 ... FC contactor 90 ... DC / DC converter 92 ... battery conductor 96 ... downverter 98 ... 12V power supply

Claims (5)

A fuel cell that generates electricity by an electrochemical reaction of an oxidant gas supplied to the cathode side and a fuel gas supplied to the anode side;
An oxidant gas supply device for supplying the oxidant gas to the fuel cell;
A fuel gas supply device for supplying the fuel gas to the fuel cell;
A method for stopping operation of a fuel cell system comprising:
A first step of generating electricity in the fuel cell while supplying the oxidant gas and the fuel gas to the fuel cell;
A second step of generating power when the fuel cell stop command is detected, while stopping the supply of the fuel gas while supplying the oxidant gas to the fuel cell;
And having
In the second step, the fuel cell power generation is stopped when the fuel gas pressure on the anode side is reduced to a lower limit set value based on the anode side pressure actually measured in advance. Battery system shutdown method.   2. The fuel cell system according to claim 1, wherein the lower limit set value is an anode-side critical pressure at which the anode-side potential starts to rise when the fuel gas pressure is reduced. 3. How to stop the operation.   3. The shutdown method according to claim 1, wherein in the second step, the anode side pressure is measured, a water vapor partial pressure is calculated, and the water vapor partial pressure is subtracted from the anode side pressure. A method for stopping operation of a fuel cell system, characterized by obtaining a fuel gas pressure.   The operation stop method according to any one of claims 1 to 3, wherein in the second step, the oxidant gas is supplied to the fuel cell with a low oxygen stoichiometry lower than an oxygen stoichiometry during normal power generation. A method for stopping the operation of the fuel cell system.   5. The operation stopping method for a fuel cell system according to claim 4, wherein the oxidant gas of the low oxygen stoichiometry is set to around 1 for the low oxygen stoichiometry.

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