JP2009123512A - Fuel cell system and scavenging method of fuel cell stack - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system and a scavenging method of a fuel cell stack capable of scavenging treatment and capable of restraining excess drying of an electrolyte film. <P>SOLUTION: The fuel cell system (100) includes a fuel cell stack (40) with one or more cells (41) equipped with reaction gas flow channels (1a, 5a) laminated, a scavenging means (20) supplying scavenging gas to the reaction gas flow channels, and current control means (10, 30, 50, 51) controlling power generation current of the fuel cell stack. The current control means controls the power generation current so that a moisture content of an electrolyte film (3) is kept at a given value or more when the scavenging gas is supplied to the reaction flow channels by the scavenging means. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fuel cell system and a scavenging method for a fuel cell stack.

  A fuel cell is a device that generally obtains electric energy using hydrogen and oxygen as fuel. Since this fuel cell is excellent in terms of environment and can realize high energy efficiency, it has been widely developed as a future energy supply system.

  In this fuel cell, since water is generated with power generation, a technique for supplying scavenging gas to the reaction gas flow path in order to discharge residual water of the fuel cell has been proposed. However, it is necessary to suppress excessive drying in the polymer electrolyte membrane. Therefore, a technique is disclosed in which scavenging treatment is performed in a state where the fuel cell is operated at a predetermined low load when the fuel cell is stopped to suppress excessive drying of the electrolyte membrane (see, for example, Patent Document 1).

Japanese Patent Laying-Open No. 2005-251576

  However, since the scavenging process ends when the dry-up of the fuel cell is detected in the technique of Patent Document 1, the electrolyte membrane may be dried too much.

  An object of the present invention is to provide a fuel cell system and a fuel cell stack scavenging method capable of performing scavenging treatment and suppressing excessive drying of an electrolyte membrane.

  A fuel cell system according to the present invention controls a fuel cell stack in which one or more cells each having a reaction gas channel are stacked, a scavenging means for supplying a scavenging gas to the reaction gas channel, and a power generation current of the fuel cell stack Current control means, and when the scavenging gas is supplied to the reaction gas flow path by the scavenging means, the current control means controls the generated current so that the moisture content of the electrolyte membrane of the cell is maintained at a predetermined value or more. It is characterized by controlling. In the fuel cell system according to the present invention, it is possible to perform the scavenging process of the reaction gas flow path and suppress excessive drying of the electrolyte membrane.

  The current control means may change the generated current according to the moisture content of the electrolyte membrane. Further, the scavenging means may change the supply amount of the scavenging gas in accordance with the moisture content of the electrolyte membrane. Further, the current control means may control the generated current so that the moisture content of the electrolyte membrane is within a predetermined range. In this case, the moisture content of the electrolyte membrane can be controlled to a desired value.

  The current control means may cause the fuel cell stack to generate electric power after the moisture content of the electrolyte membrane becomes a predetermined value or less after the supply of the scavenging gas by the scavenging means. In this case, moisture is not discharged into the flow path until the electrolyte membrane starts to dry. Therefore, the scavenging efficiency of the reaction gas channel is improved.

  The scavenging means may stop the supply of the scavenging gas when the rate of decrease in the moisture content of the electrolyte membrane becomes a predetermined value or less. In this case, scavenging is finished after the amount of water discharged and the amount of water generated are balanced. Therefore, the moisture content of the electrolyte membrane can be controlled to a desired value.

  The fuel cell system according to the present invention further includes detection means for detecting a change amount per unit time of the resistance of the fuel cell stack, and the scavenging means has a change amount per unit time of the resistance of the fuel cell stack equal to or less than a predetermined value. The scavenging gas supply may be stopped when In this case, scavenging is finished after the amount of water discharged and the amount of water generated are balanced. Therefore, the moisture content of the electrolyte membrane can be controlled to a desired value. The cell may be a polymer electrolyte fuel cell.

  A scavenging method for a fuel cell stack according to the present invention includes a scavenging step for supplying a scavenging gas to a reaction gas channel of a fuel cell stack in which one or more cells each having a reaction gas channel are stacked; And a current control step of controlling the power generation current of the fuel cell stack so that the moisture content of the electrolyte membrane of the cell is maintained at a predetermined value or higher when supplied to the path. In the scavenging method for a fuel cell stack according to the present invention, it is possible to perform a scavenging process for the reaction gas flow path and to suppress excessive drying of the electrolyte membrane.

  In the current control step, the generated current may be changed according to the moisture content of the electrolyte membrane. In the scavenging step, the supply amount of the scavenging gas may be changed according to the moisture content of the electrolyte membrane. Further, in the current control step, the generated current may be controlled so that the moisture content of the electrolyte membrane is within a predetermined range. In this case, the moisture content of the electrolyte membrane can be controlled to a desired value.

  In the current control step, after the supply of the scavenging gas is started, the fuel cell stack may generate power after the moisture content of the electrolyte membrane has become a predetermined value or less. In this case, moisture is not generated until the drying of the electrolyte membrane starts. Therefore, the scavenging efficiency of the reaction gas channel is improved.

  The scavenging method of the fuel cell stack according to the present invention may further include a stop step of stopping the supply of the scavenging gas when the rate of decrease in the moisture content of the electrolyte membrane becomes a predetermined value or less. In this case, scavenging is finished after the amount of water discharged and the amount of water generated are balanced. Therefore, the moisture content of the electrolyte membrane can be controlled to a desired value.

  The scavenging method of the fuel cell stack according to the present invention further includes a detection step of detecting a change amount per unit time of the resistance of the fuel cell stack, and the stop step includes a change amount per unit time of the resistance of the fuel cell stack. It may be a step of stopping the supply of the scavenging gas when it becomes a predetermined value or less. In this case, scavenging is finished after the amount of water discharged and the amount of water generated are balanced. Therefore, the moisture content of the electrolyte membrane can be controlled to a desired value. The cell may be a polymer electrolyte fuel cell. The cell may be a polymer electrolyte fuel cell.

  According to the present invention, scavenging treatment can be performed and excessive drying of the electrolyte membrane can be suppressed.

  Hereinafter, the best mode for carrying out the present invention will be described.

  FIG. 1 is a schematic diagram showing an overall configuration of a fuel cell system 100 according to a first embodiment of the present invention. As shown in FIG. 1, the fuel cell system 100 includes a fuel gas supply means 10, a scavenging means 20, an oxidant gas supply means 30, a fuel cell stack 40, a load 50, a switch 51, an ammeter 52, an ohmmeter 53, and a control. Means 60 are provided.

  The fuel gas supply means 10 is an apparatus that supplies fuel gas to the fuel gas flow path of the fuel cell stack 40 in accordance with instructions from the control means 60. For example, hydrogen gas can be used as the fuel gas. The scavenging means 20 is a device that supplies scavenging gas to the fuel gas flow path and the oxidant gas flow path of the fuel cell stack 40 in accordance with instructions from the control means 60. As the scavenging gas, for example, an inert gas can be used. The oxidant gas supply means 30 is a device that supplies oxidant gas to the oxidant gas flow path of the fuel cell stack 40. Air or the like can be used as the oxidant gas.

  The fuel cell stack 40 has a structure in which one or more cells 41 are stacked. In this embodiment, the cell 41 is a solid polymer fuel cell. Details of the cell 41 will be described later. The load 50 is a device that consumes electric power generated in the fuel cell stack 40. The load 50 changes the power consumption according to the instruction of the control means 60. The switch 51 is a device that turns on and off the power supply to the load 50 in accordance with an instruction from the control means 60. The ammeter 52 is a sensor that detects the generated current of the fuel cell stack 40, and gives the detection result to the control means 60. The resistance meter 53 is a sensor that detects the cell resistance of the fuel cell stack 40, and gives the detection result to the control means 60. The ohmmeter 53 may detect the cell resistance of a specific cell 41 or may detect the total cell resistance of a plurality of cells 41.

  The control means 60 comprises a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory) and the like. The control means 60 controls each part of the fuel cell system 100 based on the detection results of the ammeter 52 and the ohmmeter 53.

  Next, details of the cell 41 will be described. FIG. 2 is a schematic cross-sectional view of the cell 41. As shown in FIG. 2, the cell 41 has a structure in which a separator 1, a fuel electrode 2, an electrolyte membrane 3, an oxygen electrode 4, and a separator 5 are laminated in order. The separators 1 and 5 are made of a conductive material such as stainless steel. Grooves are provided on the fuel electrode 2 side of the separator 1 and the oxygen electrode 4 side of the separator 5. The groove part of the separator 1 functions as the fuel gas flow path 1a. The groove part of the separator 5 functions as the oxidant gas flow path 5a. The fuel gas channel 1a and the oxidant gas channel 5a may be a porous channel provided between the separator and the gas diffusion layer.

  The fuel electrode 2 includes a fuel gas diffusion layer 2a and an anode catalyst layer 2b. The fuel gas diffusion layer 2a is disposed on the separator 1 side, and the anode catalyst layer 2b is disposed on the electrolyte membrane 3 side. The fuel gas diffusion layer 2a is a layer for allowing the fuel gas to permeate the anode catalyst layer 2b and has conductivity. The fuel gas diffusion layer 2a is made of, for example, carbon paper. The anode catalyst layer 2b is a catalyst layer that promotes protonation of hydrogen and has conductivity. The anode catalyst layer 2b is made of, for example, platinum-supported carbon.

  The oxygen electrode 4 includes an oxidant gas diffusion layer 4a and a cathode catalyst layer 4b. The oxidant gas diffusion layer 4a is disposed on the separator 5 side, and the cathode catalyst layer 4b is disposed on the electrolyte membrane 3 side. The oxidant gas diffusion layer 4a is a layer for allowing the oxidant gas to permeate the cathode catalyst layer 4b and has conductivity. The oxidant gas diffusion layer 4a is made of, for example, carbon paper. The cathode catalyst layer 4b is a catalyst layer that promotes the reaction between protons and oxygen, and has conductivity. The cathode catalyst layer 4b is made of, for example, platinum-supporting carbon. The electrolyte membrane 3 is made of a solid polymer electrolyte having proton conductivity, for example, a perfluorosulfonic acid type polymer.

  Next, power generation control of the fuel cell stack 40 by the control means 60 will be described with reference to FIGS. 1 and 2. First, the control means 60 controls the switch 51 so that the switch 51 is turned on. Next, the control means 60 controls the fuel gas supply means 10 so that the fuel gas is supplied to the fuel gas flow path 1a. The fuel gas passes through the fuel gas diffusion layer 2a and reaches the anode catalyst layer 2b. Hydrogen contained in the fuel gas is dissociated into protons and electrons via the catalyst of the anode catalyst layer 2b. The protons conduct through the electrolyte membrane 3 and reach the cathode catalyst layer 4b.

  The control means 60 controls the oxidant gas supply means 30 so that the oxidant gas is supplied to the oxidant gas flow path 5a. The oxidant gas passes through the oxidant gas diffusion layer 4a and reaches the cathode catalyst layer 4b. In the cathode catalyst layer 4b, protons and oxygen react via the catalyst. Thereby, electric power is generated and water is generated. The generated power is consumed at the load 50.

  Next, scavenging control by the control means 60 will be described with reference to FIGS. 1 and 2. Scavenging control is performed when power generation is stopped. First, the control means 60 controls the scavenging means 20 so that the scavenging gas is supplied to the fuel gas flow path 1a and the oxidant gas flow path 5a. In this case, moisture in the fuel gas channel 1a, the fuel gas diffusion layer 2a, the oxidant gas channel 5a, and the oxidant gas diffusion layer 4a is removed, and moisture contained in the electrolyte membrane 3 of the cell 41 is removed. .

  On the other hand, the control means 60 causes the fuel cell stack 40 to generate power in accordance with the power generation control. In this case, a predetermined amount of water generated by power generation is supplied to the electrolyte membrane 3. Therefore, by appropriately controlling the amount of scavenging gas and the generated current value, the moisture remaining in the fuel gas channel 1a, the fuel gas diffusion layer 2a, the oxidant gas channel 5a and the oxidant gas diffusion layer 4a is removed. In addition, excessive drying of the electrolyte membrane 3 can be suppressed. As a result, the oxidant gas and the fuel gas can be efficiently supplied to each cell 41 at a low temperature startup such as below freezing, and the output of the cell 41 at the startup can be ensured.

  In the present embodiment, the control means 60 controls the generated current of the fuel cell stack 40 based on the detection result of the ammeter 52 so that the moisture content of the electrolyte membrane 3 is maintained at a predetermined value or more. The generated current of the fuel cell stack 40 can be controlled by controlling the power consumption of the load 50. In this embodiment, the moisture content of the electrolyte membrane 3 can be estimated or calculated based on the detection result of the ohmmeter 53. This is because there is a correlation between the moisture content of the electrolyte membrane 3 and the cell resistance of the cell 41 in which the cell resistance decreases when the moisture content increases and the cell resistance increases when the moisture content decreases.

  FIG. 3 shows an example of the change in cell resistance of the cell 41. FIG. 3 is a diagram illustrating the relationship between the scavenging time and the cell resistance of the cell 41. In FIG. 3, the horizontal axis represents the elapsed time after the start of scavenging, and the vertical axis represents the cell resistance of the entire fuel cell stack 40. As shown in FIG. 3, the cell resistance maintains a low value in a predetermined period after the start of scavenging. During this period, it is considered that moisture staying in the fuel gas channel 1a, the fuel gas diffusion layer 2a, the oxidant gas channel 5a, and the oxidant gas diffusion layer 4a is discharged.

  Thereafter, the cell resistance increases with time. In this period, it is considered that moisture is discharged from the electrolyte membrane 3 and the moisture content of the electrolyte membrane 3 is reduced. Thereafter, if the fuel cell stack 40 is not generating power, the cell resistance continuously increases, but in this embodiment, the cell resistance converges to a predetermined value. This is presumably because the amount of water generated during power generation and the amount of water discharged from the electrolyte membrane 3 are balanced. Therefore, it is considered that the moisture content of the electrolyte membrane 3 is maintained at a predetermined value. The control unit 60 may control the switch 51 so that the switch 51 is turned off after the cell resistance has converged, and may control the scavenging unit 20 so that the supply of the scavenging gas is stopped. The control means 60 may control the generated current of the fuel cell stack 40 so that the moisture content of the electrolyte membrane 3 is within a desired range. In this case, the moisture content of the electrolyte membrane 3 can be controlled to a desired value.

  As described above, the total cell resistance of the fuel cell stack 40 converges by continuing the power generation. In this case, the cell resistance of each cell 41 also converges. Thereby, in the case where a plurality of cells 41 are stacked on the fuel cell stack 40, variation in cell resistance between the cells 41 can be suppressed. The convergence value of the cell resistance is constant regardless of the moisture content of each electrolyte membrane 3 before the start of scavenging. Moreover, the convergence value of the cell resistance changes according to the magnitude of the generated current during scavenging. Therefore, the cell resistance of each cell 41 can be controlled to a desired value by controlling the generated current during scavenging. Moreover, the moisture content of each part of each electrolyte membrane 3 converges. Thereby, the dispersion | variation in resistance distribution in each cell 41 can be suppressed. As a result, the occurrence of variations in the power generation distribution in each cell 41 is suppressed.

  Note that the control means 60 may control the switch 51 so that the power generation of the fuel cell stack 40 is stopped until the cell resistance becomes larger than a predetermined value after the start of scavenging. The predetermined value in this case may be set, for example, around the resistor R1 where the cell resistance starts increasing in FIG. In this case, water generation by power generation is not performed until the drying of the electrolyte membrane 3 starts. Therefore, the water staying in the fuel gas channel 1a, the fuel gas diffusion layer 2a, the oxidant gas channel 5a, and the oxidant gas diffusion layer 4a is efficiently discharged. Therefore, scavenging efficiency is improved.

  Further, the control means 60 may change the generated current of the fuel cell stack 40 in accordance with the moisture content of the electrolyte membrane 3 (cell resistance of the cell 41). For example, when the moisture content of the electrolyte membrane 3 is large, the power generation current of the fuel cell stack 40 is set small, and when the moisture content of the electrolyte membrane 3 is small, the power generation current of the fuel cell stack 40 is set large. Also good. In this case, the water content of the electrolyte membrane 3 can be controlled to a desired value without greatly changing.

  Further, the control means 60 may change the amount of scavenging gas supplied by the scavenging means 20 in accordance with the moisture content of the electrolyte membrane 3 (cell resistance of the cell 41). For example, when the moisture content of the electrolyte membrane 3 is large, the supply amount of the scavenging gas may be set large, and when the moisture content of the electrolyte membrane 3 becomes small, the supply amount of the scavenging gas may be changed small. In this case, the water content of the electrolyte membrane 3 can be controlled to a desired value without greatly changing.

  Further, the control means 60 may end the scavenging when the rate of decrease in the moisture content of the electrolyte membrane 3 becomes a predetermined value or less. In the present embodiment, the control means 60 ends scavenging when the increase amount per unit time of the cell resistance becomes a predetermined value or less. FIG. 4 is a diagram showing changes per unit time of cell resistance. In FIG. 4, the horizontal axis indicates the elapsed time after the start of scavenging, the left vertical axis indicates the total cell resistance of the fuel cell stack 40, and the right vertical axis differentiates the total cell resistance of the fuel cell stack 40 with respect to time. Variable (dR / dt) is shown. As shown in FIG. 4, the cell resistance hardly changes during a predetermined period after the start of scavenging. Therefore, dR / dt is almost zero.

  Thereafter, the cell resistance increases with time. Therefore, dR / dt also increases. However, after that, the increase in cell resistance decreases. In this case, dR / dt becomes small. Thereafter, the cell resistance converges to a predetermined value. Therefore, dR / dt becomes almost zero again.

  For example, the control means 60 may control the scavenging means 20 to stop the supply of the scavenging gas when dR / dt becomes smaller than the predetermined value after becoming larger than the predetermined value. In this case, scavenging can be terminated after the moisture content of the electrolyte membrane 3 reaches a desired value.

  The control means 60 may change the generated current of the fuel cell stack 40 according to dR / dt. For example, after the start of scavenging, when dR / dt is small, the generated current of the fuel cell stack 40 may be set small, and when dR / dt is large, the generated current of the fuel cell stack 40 may be set large. . In this case, the water content of the electrolyte membrane 3 can be controlled to a desired value without greatly changing.

  Next, FIG. 5 shows an example of a flowchart of the scavenging control by the control means 60. The control means 60 executes the flowchart of FIG. 5 at a predetermined cycle. First, the control means 60 controls the scavenging means 20 so that the scavenging gas is supplied to the fuel gas flow path 1a and the oxidant gas flow path 5a. (Step S1).

  Next, the control means 60 determines whether or not the cell resistance R is smaller than the resistance R1 and dR / dt is larger than a predetermined value A (step S2). The cell resistance R is obtained from the detection result of the resistance meter 53. The resistor R1 is, for example, R1 shown in FIG. The predetermined value A can be set in a range in which the moisture content of the electrolyte membrane 3 does not decrease excessively. When it is not determined in step S2 that the cell resistance R is smaller than the resistance R1 and dR / dt is larger than the predetermined value A, the control unit 60 ends the execution of the flowchart. In this case, scavenging is continued. In this case, the control means 60 may execute step S2 again without ending the execution of the flowchart.

  When it is determined in step S2 that the cell resistance R is smaller than the resistance R1 and dR / dt is larger than the predetermined value A, the control means 60 makes the generated current I of the fuel cell stack 40 become the predetermined value B. Then, the fuel gas supply means 10, the oxidant gas supply means 30, the switch 51, and the load 50 are controlled (step S3). This predetermined value B can be set according to the target moisture content of the electrolyte membrane 3. Next, the control means 60 sets the scavenging continuation flag F to “1” (step S4).

  Next, the control means 60 determines whether or not the scavenging continuation flag F = 1 and dR / dt is smaller than a predetermined value C (step S5). The predetermined value C can be set in a range smaller than the maximum value of dR / dt. If it is not determined in step S5 that the scavenging continuation flag F = 1 and dR / dt is smaller than the predetermined value C, the control means 60 executes step S4 again. Thereby, scavenging and power generation are continued.

  When it is determined in step S5 that the scavenging continuation flag F = 1 and dR / dt is smaller than the predetermined value C, the control means 60 controls the switch 51 so that the switch 51 is turned off and supplies fuel gas. The fuel gas supply means 10 and the oxidant gas supply means 30 are controlled so that the supply of the oxidant gas is stopped. Further, the control means 60 controls the scavenging means 20 so that the supply of the scavenging gas is stopped (step S6). Thereafter, the control means 60 ends the execution of the flowchart.

  Thus, by performing the flowchart of FIG. 5, scavenging processing can be performed and excessive drying of the electrolyte membrane 3 can be suppressed.

  In this embodiment, the fuel gas passage 1a and the oxidant gas passage 5a correspond to the reaction gas passage, and the fuel gas supply means 10, the oxidant gas supply means 30, the load 50, the switch 51, and the control means 60 are provided. The ohmmeter 53 and the control means 60 correspond to the detection means, the step S1 corresponds to the scavenging step, the step S3 corresponds to the current control step, the step S6 corresponds to the stop step, and the step corresponds to the current control means. S2 corresponds to a detection step.

1 is a schematic diagram showing an overall configuration of a fuel cell system according to a first embodiment of the present invention. It is a typical sectional view of a cell. It is a figure which shows an example about the change of the cell resistance of a cell. It is a figure which shows the change per unit time of cell resistance. It is a figure which shows an example of the flowchart of the scavenging control by a control means.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1a Fuel gas flow path 5a Oxidant gas flow path 3 Electrolyte membrane 10 Fuel gas supply means 20 Scavenging means 30 Oxidant gas supply means 40 Fuel cell stack 41 Cell 50 Load 51 Switch 52 Ammeter 53 Resistance meter 60 Control means 100 Fuel cell system

Claims (16)

A fuel cell stack in which one or more cells each having a reaction gas flow path are stacked;
Scavenging means for supplying a scavenging gas to the reaction gas flow path;
Current control means for controlling the generated current of the fuel cell stack,
The current control means controls the generated current so that the moisture content of the electrolyte membrane of the cell is maintained at a predetermined value or more when the scavenging gas is supplied to the reaction gas flow path by the scavenging means. A fuel cell system.   2. The fuel cell system according to claim 1, wherein the current control means changes the generated current in accordance with a moisture content of the electrolyte membrane.   2. The fuel cell system according to claim 1, wherein the scavenging means changes a supply amount of the scavenging gas in accordance with a moisture content of the electrolyte membrane.   The fuel cell system according to any one of claims 1 to 3, wherein the current control means controls the generated current so that a moisture content of the electrolyte membrane is within a predetermined range.   The current control means causes the fuel cell stack to generate electric power after the moisture content of the electrolyte membrane becomes a predetermined value or less after the supply of the scavenging gas by the scavenging means is started. The fuel cell system according to any one of the above.   The fuel cell according to any one of claims 1 to 5, wherein the scavenging means stops the supply of the scavenging gas when the water content reduction rate of the electrolyte membrane becomes a predetermined value or less. system. A detecting means for detecting a change amount per unit time of the resistance of the fuel cell stack;
7. The fuel cell system according to claim 6, wherein the scavenging means stops the supply of the scavenging gas when the amount of change per unit time in resistance of the fuel cell stack becomes a predetermined value or less.   The fuel cell system according to claim 1, wherein the cell is a polymer electrolyte fuel cell. A scavenging step of supplying a scavenging gas to the reaction gas channel of the fuel cell stack in which one or more cells having the reaction gas channel are stacked;
A current control step of controlling the power generation current of the fuel cell stack so that the moisture content of the electrolyte membrane of the cell is maintained at a predetermined value or more when the scavenging gas is supplied to the reaction gas flow path; A scavenging method for a fuel cell stack, comprising:   The scavenging method for a fuel cell stack according to claim 9, wherein, in the current control step, the generated current is changed in accordance with a moisture content of the electrolyte membrane.   The scavenging method for a fuel cell stack according to claim 9, wherein, in the scavenging step, a supply amount of the scavenging gas is changed in accordance with a moisture content of the electrolyte membrane.   The scavenging method for a fuel cell stack according to any one of claims 9 to 11, wherein, in the current control step, the generated current is controlled so that a moisture content of the electrolyte membrane is within a predetermined range.   13. The fuel cell stack according to claim 9, wherein, in the current control step, after the supply of the scavenging gas is started, the fuel cell stack is caused to generate power after a moisture content of the electrolyte membrane becomes a predetermined value or less. Scavenging method for fuel cell stack.   The fuel cell according to any one of claims 9 to 13, further comprising a stop step of stopping the supply of the scavenging gas when the rate of decrease in the moisture content of the electrolyte membrane becomes a predetermined value or less. The stack scavenging method. A detection step of detecting a change amount per unit time of the resistance of the fuel cell stack;
15. The fuel according to claim 14, wherein the stopping step is a step of stopping the supply of the scavenging gas when an amount of change per unit time in resistance of the fuel cell stack becomes a predetermined value or less. Battery stack scavenging method.   The method of scavenging a fuel cell stack according to any one of claims 9 to 15, wherein the cell is a solid polymer fuel cell.

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