JP2008034127A - Fuel cell system and its shutdown processing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To shorten time required for suction of fuel gas at the time of operation shutdown processing of a fuel cell and suppress deterioration progress of a catalyst at the fuel electrode. <P>SOLUTION: At the time of shutdown processing of a fuel cell system 10 provided with a fuel cell 20 which generates power by electrochemical reaction of an oxidizing gas and a fuel gas, a compressor 40 to supply the oxidizing gas to the fuel cell 20, an oxidizing gas supply passage 41 to connect the compressor 40 and the fuel cell 20, a fuel gas supply passage 31 to supply the fuel gas to the fuel cell 20, and an oxidizing gas exhaust passage 42 and a fuel gas exhaust passage 33 to discharge oxidizing off-gas and fuel off-gas discharged from the fuel cell 20, the compressor 40 is reverse rotated with a valve 65 installed at the downstream of a junction of the oxidizing gas exhaust passage 42 and the fuel gas exhaust passage 33 in closed state, and the oxidizing gas passage and the fuel gas passage in the fuel cell are both decompressed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fuel cell system and a stop processing method thereof. More specifically, the present invention relates to an improvement in fuel cell stop processing technology.

  In general, a fuel cell (for example, a polymer electrolyte fuel cell) is configured by stacking a plurality of cells each having an electrolyte sandwiched between separators. In addition to such a fuel cell, a piping system for supplying and discharging reaction gas (fuel gas and oxidizing gas) to the fuel cell, a power system for charging and discharging electric power, a control system for overall control of the system, etc. A fuel cell system is configured.

In such a fuel cell system, the fuel gas (hydrogen gas) remaining in the fuel electrode (anode) and the fuel gas piping system permeates the electrolyte membrane during the operation stop state, and the oxidizing gas system such as the air electrode (cathode). When the system is restarted in such a situation, a chemical reaction may occur with the supplied oxidizing gas, or the exhaust hydrogen concentration may increase. Therefore, when the fuel cell is stopped, the air compressor of the oxidant gas piping system is reversely rotated to make the inside of the system have a negative pressure, the fuel gas (hydrogen gas) in the fuel gas system is sucked in advance, and the water is removed. Such a technique is disclosed (for example, see Patent Document 1).
JP 2005-259440 A

  However, in the case of the technique as described above, the time required for gas suction during the stop process may be long. Further, when air is mixed into the anode side, the catalyst may deteriorate at the fuel electrode.

  Therefore, the present invention provides a fuel cell system and a stop processing method thereof that can shorten the time required for fuel gas suction during the stop processing of the fuel cell and can suppress the progress of catalyst deterioration at the fuel electrode. Objective.

  In order to solve this problem, the present inventor has made various studies. As described above, reducing the pressure of the fuel gas system when the fuel cell (or fuel cell system) is stopped is a desirable technique for suppressing the phenomenon that the exhaust hydrogen concentration becomes high at the time of restart. However, conventionally, there has been a situation where it is difficult to sufficiently reduce the pressure due to the fact that the measurement result of the pressure sensor includes an error or there is a response delay of the valve. That is, the normal pressure reduction method is not sufficient, and a lot of hydrogen may remain in the fuel gas system of the fuel cell. Accordingly, as a result of further studies, the present inventor who has focused on such points has come up with an idea that leads to the solution of such a problem.

  The present invention is based on such an idea, and includes a fuel cell that generates power by an electrochemical reaction between an oxidizing gas and a fuel gas, a compressor that supplies the oxidizing gas to the fuel cell, and an oxidizing gas supply channel that connects the compressor and the fuel cell. And a fuel gas supply channel for supplying fuel gas to the fuel cell, and an oxidizing gas discharge channel and a fuel gas discharge channel for discharging the oxidizing off gas and the fuel off gas discharged from the fuel cell. In FIG. 5, the valve that is closed during the stop process of the fuel cell and prevents the gas from flowing back into the oxidant gas channel and the fuel gas channel in the fuel cell that has been depressurized includes the oxidant gas discharge channel and the fuel gas discharge flow. It is provided in the downstream of the junction of a path | route. Further, during the stop process of the fuel cell, both the oxidizing gas channel and the fuel gas channel in the fuel cell can be decompressed by rotating the compressor in the reverse direction with the valve closed.

  In such a fuel cell system, by closing a valve provided downstream of the junction point of the exhaust gas and fuel gas discharge flow path, excess oxidizing gas (air) is not taken into the gas piping system. Can be. Therefore, it is possible to shorten the time required for gas suction during the stop process (for example, the compressor driving time).

  Further, according to the fuel cell system of the present invention, air can be prevented from being mixed into the fuel electrode (anode), so that deterioration of the anode catalyst can also be suppressed. Incidentally, if the gas piping system is not depressurized to a negative pressure, both hydrogen cross-leakage to the air electrode (cathode) and combustion at the cathode may occur, but this point is reduced to a negative pressure. If this is done, although the combustion may occur temporarily, the cross leak can be suppressed, and the breakage due to the freezing of moisture can be suppressed. Further, in such a fuel cell system, the oxidant gas passage and the fuel gas passage can be decompressed simultaneously and uniformly during decompression (for example, during reverse rotation of the compressor) due to the stop processing. It is possible to dry the system by removing water in a shorter time than when sucking separately.

  The valve in the fuel cell system as described above is, for example, a check valve. When a check valve is used, the valve can be closed in conjunction with the operation of the compressor without performing valve control.

  The valve may alternatively be an oxidizing gas pressure regulating valve. In this case, it is not necessary to provide a separate valve for control during the stop process.

  Further, the valve as described above is preferably provided on the upstream side of the gas-liquid separator for gas-liquid separation of the oxidation off-gas and the fuel off-gas. For example, when the liquid separated by the gas-liquid separator is at the same pressure as the atmospheric pressure, if the valve is disposed on the downstream side of the gas-liquid separator, the oxidizing gas flow path in the fuel cell and It becomes impossible to prevent the gas from flowing back into the fuel gas passage. In this respect, in the case of the configuration as described above, since the hydrogen suction efficiency can be maintained or increased without causing a backflow of gas, the time required for gas suction during the stop process can be shortened. .

  The stop processing method according to the present invention includes a fuel cell that generates electric power by an electrochemical reaction between an oxidizing gas and a fuel gas, a compressor that supplies the oxidizing gas to the fuel cell, and an oxidizing gas supply channel that connects the compressor and the fuel cell. And a fuel gas supply channel for supplying fuel gas to the fuel cell, and an oxidizing gas discharge channel and a fuel gas discharge channel for discharging the oxidizing off gas and the fuel off gas discharged from the fuel cell. During the stop process, the compressor is reversely rotated with the valve provided downstream of the junction of the oxidant gas discharge channel and the fuel gas discharge channel closed, and the oxidant gas channel and fuel gas flow in the fuel cell are rotated. The road is decompressed together.

  According to the present invention, the fuel gas can be efficiently sucked during the fuel cell operation stop process, so that the time required for the sucking can be shortened. Further, the catalyst can be prevented from progressing at the fuel electrode by sufficiently sucking the fuel gas.

  Hereinafter, the configuration of the present invention will be described in detail based on an example of an embodiment shown in the drawings.

  1 to 3 show an embodiment of a fuel cell system according to the present invention. The fuel cell system 10 according to the present invention includes a fuel cell 20, an air compressor 40, an oxidizing gas supply channel 41, a fuel gas supply channel 31, a cathode offgas channel (oxidizing gas discharge channel) 42, The system includes an anode off gas (fuel gas discharge passage) 33 (see FIG. 1). In the present embodiment, a valve 65 is further provided downstream of the junction of the cathode offgas passage (oxidizing gas discharge passage) 42 and the anode offgas (fuel gas discharge passage) 33, and the valve 65 is used for the operation stop processing. The fuel gas suction is efficiently and sufficiently performed.

  In the following, first, the overall configuration of the fuel cell system 10 will be described, and then the configuration and the like related to the operation stop process will be described.

  FIG. 1 shows a schematic configuration of a fuel cell system 10 in the present embodiment. Here, an example in which the fuel cell system 10 is used as an in-vehicle power generation system for a fuel cell vehicle (FCHV) is shown. It can also be used as an onboard power generation system, or as a stationary power generation system. The fuel cell (fuel cell stack) 20 has a stack structure in which a plurality of single cells are stacked in series, and is composed of, for example, a solid polymer electrolyte fuel cell.

  The fuel cell system 10 according to the present embodiment includes a fuel gas piping system and an oxidizing gas piping system connected to the fuel cell 20. The fuel gas piping system includes a fuel gas supply source 30, a fuel gas supply channel 31, a fuel cell 20, a fuel gas circulation channel 32, and an anode off-gas channel (fuel gas discharge channel) 33. (See FIG. 1).

  The fuel gas supply source 30 is configured by a hydrogen storage source such as a high-pressure hydrogen tank or a hydrogen storage tank (which may include a storage alloy), for example. The fuel gas supply flow path 31 is a gas flow path for guiding the fuel gas discharged from the fuel gas supply source 30 to the anode (fuel electrode) of the fuel cell 20, and the gas flow path includes a tank valve from upstream to downstream. H201, high pressure regulator H9, low pressure regulator H10, hydrogen supply valve H200, and FC inlet valve H21 are provided. The fuel gas compressed to a high pressure is reduced to a medium pressure by a high pressure regulator H9 and further reduced to a low pressure (normal operating pressure) by a low pressure regulator H10.

  The fuel gas circulation passage 32 is a return gas passage for recirculating unreacted fuel gas to the fuel cell 20, and includes an FC outlet valve H22, a hydrogen pump 63, and a check valve from upstream to downstream. Each H52 is disposed. The low-pressure unreacted fuel gas discharged from the fuel cell 20 is appropriately pressurized by the hydrogen pump 63 and guided to the fuel gas supply channel 31. The check valve H52 suppresses the backflow of the fuel gas from the fuel gas supply channel 31 to the fuel gas circulation channel 32. The anode off-gas channel 33 branched in the middle of the fuel gas circulation channel 32 is a gas channel for exhausting the hydrogen off-gas discharged from the fuel cell 20 to the outside of the system. A valve H51 is provided.

  The tank valve H201, the hydrogen supply valve H200, the FC inlet valve H21, the FC outlet valve H22, and the purge valve H51 described above supply fuel gas to the gas flow paths 31 to 33 or the fuel cell 20, or Is a shut valve for shutting off the valve, and is constituted by, for example, an electromagnetic valve. As such an electromagnetic valve, for example, an on / off valve or a linear valve capable of linearly adjusting the valve opening degree by PWM control is suitable.

  The oxidizing gas piping system of the fuel cell 20 includes an air compressor 40, an oxidizing gas supply channel 41, and a cathode offgas channel (oxidizing gas discharge channel) 42. The air compressor 40 compresses air taken in from the outside air via the air filter 61 and supplies the compressed air as an oxidizing gas to the cathode (air electrode) of the fuel cell 20. The oxygen off-gas after being subjected to the cell reaction of the fuel cell 20 flows through the cathode off-gas flow path 42 and is exhausted outside the system. This oxygen off gas is in a highly moist state because it contains moisture generated by the cell reaction in the fuel cell 20. The humidification module 62 exchanges moisture between the low-humid state oxidizing gas flowing through the oxidizing gas supply channel 41 and the high-humid state oxygen off-gas flowing through the cathode off-gas channel 42 to oxidize the oxygen supplied to the fuel cell 20. Humidify the gas moderately. The back pressure of the oxidizing gas supplied to the fuel cell 20 is regulated by a pressure regulating valve A4 disposed near the cathode outlet of the cathode offgas passage 42. Further, the cathode offgas passage 42 communicates with the diluter 64 downstream thereof. Further, the anode off-gas passage 33 communicates with the diluter 64 downstream thereof, and is configured to exhaust the hydrogen off-gas outside the system after being mixed and diluted with the oxygen off-gas.

  A part of the DC power generated by the fuel cell 20 is stepped down by the DC / DC converter 53 and charged to the battery (secondary battery) 54. The traction inverter 51 and the auxiliary inverter 52 convert the DC power supplied from the fuel cell 20 and / or the battery 54 into AC power and supply the AC power to each of the traction motor M3 and the auxiliary motor M4. . Incidentally, the auxiliary motor M4 is a generic term for a motor M2 for driving a hydrogen pump 63, which will be described later, a motor M1 for driving the air compressor 40, and the like. In other words, it may function as M2. In the following description, those driven by one or both of the fuel cell 20 and the battery 54 are collectively referred to as a load.

  The control unit 50 obtains the system required power (the sum of the vehicle travel power and auxiliary power) based on the accelerator opening detected by the accelerator sensor 55, the vehicle speed detected by the vehicle speed sensor 56, etc., and the fuel cell 20 becomes the target power. Control the system to match. Specifically, the control unit 50 adjusts the rotation speed of the motor M1 that drives the air compressor 40 to adjust the supply amount of the oxidizing gas, and adjusts the rotation speed of the motor M2 that drives the hydrogen pump 63 to adjust the fuel gas. Adjust the supply amount. Further, the control unit 50 controls the DC / DC converter 53 to adjust the operation point (output voltage, output current) of the fuel cell 20 and adjust the output power of the fuel cell 20 to match the target power.

  High pressure part (section of tank valve H201 to hydrogen supply valve H200), low pressure part (hydrogen supply valve H200 to FC inlet valve H21), FC part (FC inlet valve H21 to FC outlet valve H22), circulation part (FC outlet valve H22) To each check valve H52) are pressure sensors (state detecting means) P6, P7, P9, P61, P5, P10, P11 for detecting the pressure of the fuel gas and temperature sensors (state for detecting the temperature of the fuel gas). Detection means) T6, T7, T9, T61, T5, T10 are arranged. The role of each pressure sensor will be described in detail. The pressure sensor P6 detects the fuel gas supply pressure of the fuel gas supply source 30. The pressure sensor P7 detects the secondary pressure of the high pressure regulator H9. The pressure sensor P9 detects the secondary pressure of the low pressure regulator H10. The pressure sensor P61 detects the pressure in the low pressure portion of the fuel gas supply channel 31. The pressure sensor P5 detects the pressure at the inlet of the fuel cell 20. The pressure sensor P10 detects the pressure on the input port side (upstream side) of the hydrogen pump 63. The pressure sensor P11 detects the pressure on the output port side (downstream side) of the hydrogen pump 63.

  The fuel electrode pressure detection means P5 is for detecting the pressure at the fuel electrode (anode), and is constituted by, for example, a pressure gauge. In the present embodiment, this fuel electrode pressure detection means P5 is disposed in the low pressure portion of the fuel gas supply flow path 31, more specifically, between the FC inlet valve H21 and the fuel cell 20 (see FIG. 1). . The fuel electrode pressure detection means P5 is further connected to the ECU 13 so as to transmit data relating to the detected pressure value to the ECU 13.

  ECU13 is the control means comprised by the electronic control apparatus (Electric Control Unit). The ECU 13 according to this embodiment includes a stack temperature detecting unit 11 that detects the temperature of the fuel cell 20, a standing time measuring unit 12 that measures a time from when the operation of the fuel cell 20 is stopped until it is restarted, and a fuel pole pressure. It is connected to each of the detection means P5, and acquires data on the stack temperature, the standing time, and the fuel electrode pressure (anode pressure). These data are used, for example, in estimating the anode nitrogen concentration (concentration of nitrogen in the anode including the one that has passed through the electrolyte membrane and reached from the cathode to the anode). Although not shown in detail in FIG. 1, the ECU 13 is also connected to the control unit 50, and the output of the fuel cell 20 is limited when necessary according to, for example, the estimated anode nitrogen concentration. .

  Subsequently, in the fuel cell system 10 of the present embodiment, a configuration for efficiently and sufficiently sucking the fuel gas during the operation stop process of the fuel cell 20 (or the fuel cell system 10) will be described (FIG. 2 and the like). reference).

  In this fuel cell system 10, a check valve 65 is provided downstream of the junction of the cathode offgas passage (oxidizing gas discharge passage) 42 and the anode offgas passage (fuel gas discharge passage) 33. For example, in the case of this embodiment, the check valve 65 is disposed on the downstream side of the diluter 64 described above (see FIG. 1). The check valve 65 functions as a valve for preventing the gas from flowing back into the oxidant gas flow path and the fuel gas flow path in the fuel cell 20 that has been decompressed during the stop process of the fuel cell 20. . If such a check valve 65 is used, the fuel gas (hydrogen gas) in the anode and the fuel gas piping system can be efficiently and sufficiently sucked when the pressure in the gas piping system is reduced. .

  In the present embodiment, the air compressor 40 described above is rotated in the reverse direction to reduce the pressure of the gas piping system and suck the fuel gas (see FIG. 2). Although other devices can be used, it is preferable to use the existing air compressor 40 not only for supplying the oxidizing gas but also for sucking the fuel gas in terms of cost reduction and system miniaturization.

  In the fuel cell system 10 of the present embodiment, a gas-liquid separator 66 is provided on the downstream side of the check valve 65 described above, and a muffler 67 for absorbing sound during exhaust is further provided on the downstream side thereof ( (See FIGS. 1 and 2). If there is liquid (moisture) in the muffler 67, the efficiency of sound absorption is reduced, so the gas-liquid separator 66 separates the discharged gas into gas and liquid in the preceding stage, and sends only the gas to the muffler 67. The separated liquid is discharged to the outside of the gas-liquid separator 66 as it is.

  Here, an example of the stop processing method of the fuel cell system 10 based on the above-described configuration will be described with reference to a flowchart (see FIG. 3).

  After starting the stop process accompanying the stop of the operation of the fuel cell system 10 (or the fuel cell 20), first, the air compressor 40 is reversely rotated (step 1). In such a case, the gas is sucked and flows backward, and the oxidizing gas piping system (the oxidizing gas supply channel 41 and the cathode offgas channel 42) is in a reduced pressure state. Further, in the case of the fuel cell system 10 of the present embodiment, the check valve 65 is closed as the oxidizing gas piping system is depressurized in this way (step 1).

  Next, the purge valve H51 is opened (step 2). Thereby, the fuel gas piping system (the anode off-gas flow path 33, the fuel gas circulation flow path 32, and further a part of the fuel gas supply flow path 31) is decompressed. Therefore, the hydrogen gas remaining in the anode and the fuel gas piping system is sucked into the oxidizing gas system so as to sequentially pass through the anode offgas channel 33, the diluter 64, the cathode offgas channel 42, and the oxidizing gas supply channel 41. (See FIG. 1 and the like).

  Next, when a certain time has passed (step 3), the purge valve H51 is closed (step 4). Here, the stop process is performed for a certain period of time. Alternatively, for example, the stop process may be performed until the pressure at any point in the system reaches a predetermined value or less (step 3). Thereafter, the air compressor 40 is stopped (step 5). Terminate the stop process. At this time, the hydrogen pump 63 and the like are also stopped as necessary.

  As described so far, according to the fuel cell system 10 of the present embodiment, the fuel gas can be efficiently sucked when the fuel cell system 10 (or the fuel cell 20) is stopped. Time can be shortened. In addition, it is possible to suppress the progress of catalyst deterioration at the fuel electrode by sufficiently sucking the fuel gas.

  In the present embodiment, since the check valve 65 is used, the valve can be closed in conjunction with the operation of the air compressor 40 without performing valve control.

  Further, in the present embodiment, since the check valve 65 is arranged upstream of the gas-liquid separator 66, there is an advantage that the fuel gas can be sucked efficiently and sufficiently. That is, since the liquid separated by the gas-liquid separator 66 is discharged out of the apparatus as it is, if the check valve 65 is disposed on the downstream side of the gas-liquid separator 66, the check Even if the valve 65 is closed, external air may flow from the gas-liquid separator 66. In this respect, in the case of the configuration of the present embodiment, it is possible to suppress the inflow of external air and maintain or enhance the suction efficiency of hydrogen gas.

  Further, according to the fuel cell system 10 described above, it is possible to simultaneously and uniformly depressurize the oxidizing gas piping system and the fuel gas piping system during decompression (for example, during reverse rotation of the air compressor 40). In this case, if moisture is removed and the system is dried in a shorter time than sucking the gases separately, it can be expected that the low-temperature startability at the time of restart is improved. By the way, if only hydrogen gas is sucked from the gas piping system, 1) the oxidizing gas flow rate at the cathode is once increased and diluted, and 2) a hydrogen gas processing device is added to improve performance (for example, hydrogen gas Any of the following measures may be required: a catalyst combustor that burns on the catalyst is installed in the flow path), and 3) that the hydrogen gas is discharged little by little over time. In this respect, according to the fuel cell system 10 of the present embodiment, if the gas is sucked at once using the air compressor 40, hydrogen is combusted at the cathode, so that there is an advantage that the pressure can be reduced or reduced to a negative pressure in a short time.

  The above-described embodiment is an example of a preferred embodiment of the present invention, but is not limited thereto, and various modifications can be made without departing from the scope of the present invention. For example, in the present embodiment, the check valve 65 is exemplified as a valve for efficiently sucking in hydrogen gas (see FIG. 1 and the like). However, other valves can be used as a matter of course. A valve or an on-off valve operable from the outside may be used. Alternatively, a relief valve that does not require valve control and has a relatively low cost may be used.

  Alternatively, the pressure adjustment valve A4 can be used instead of the check valve 65. For example, the pressure regulating valve A4 in the above-described embodiment is disposed between the fuel cell 20 and the humidification module 62 (see FIG. 1), but if this is disposed downstream of the diluter 64, the number of parts is reduced. And is preferable in that the cost can be reduced. This is particularly useful in such a fuel cell system 10 because the response of adjustment by the pressure adjustment valve A4 may not be high depending on the system.

  Further, the arrangement of the pressure regulating valve A4 may be changed as described above, and the check valve 65 as described above may be additionally provided. In such a case, it is possible to further effectively reduce the pressure by effectively suppressing the inflow of outside air by the action of both the pressure regulating valve A4 and the check valve 65. Or when using the relief valve mentioned above, it is good also as arrange | positioning the pressure regulation valve A4 downstream of the diluter 64. FIG.

  In the present embodiment, the cathode offgas flow path (oxidation gas discharge flow path) 42 and the anode off gas (fuel gas discharge flow path) 33 are combined in the diluter 64. Of course, it is possible to apply the present invention even in a configuration in which the merging is performed upstream of 64. When the junction point and the diluter 64 are thus separated, the check valve 65 can be disposed between the junction point and the diluter 64. In such a case, the suction amount is smaller. There is also an advantage that it can be completed.

  Further, the check valve 65 described in the present embodiment is automatically closed by rotating the air compressor 40 in the reverse direction. However, the valve is closed using a valve that can be operated from the outside. Of course, the air compressor 40 may be rotated in reverse after the operation. In short, during reverse rotation of the air compressor 40, at least during the state in which the check valve 65 is closed, the fuel gas (hydrogen gas) in the fuel gas piping system is efficiently sucked by suppressing the inflow of external air. Is possible.

  Further, in the present embodiment, hydrogen gas is sucked using the anode off-gas flow path (fuel gas discharge flow path) 33 and the cathode off-gas flow path (oxidation gas discharge flow path) 42 which are existing piping systems. However (see FIG. 2), it is also possible to suck the hydrogen gas into the oxidizing gas system by using a new bypass 68 connecting the fuel gas system and the oxidizing gas system (see FIG. 4).

It is a figure which shows the structure of the fuel cell system in this embodiment. It is a figure which shows a fuel cell system roughly focusing on a gas piping system. It is a flowchart which shows an example of the stop processing method of a fuel cell system. It is the schematic which shows another example of the fuel cell system concerning this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Fuel cell system, 20 ... Fuel cell, 31 ... Fuel gas supply flow path, 33 ... Anode off-gas flow path (fuel gas discharge flow path), 40 ... Air compressor (compressor), 41 ... Oxidation gas supply flow path, 42 ... Cathode off gas flow path (oxidation gas discharge flow path), 65 ... Check valve (valve provided downstream of the junction of the oxidation gas discharge flow path and the fuel gas discharge flow path)

Claims (6)

A fuel cell that generates electricity by an electrochemical reaction between an oxidizing gas and a fuel gas, a compressor that supplies the oxidizing gas to the fuel cell, an oxidizing gas supply channel that connects the compressor and the fuel cell, and a fuel gas that is supplied to the fuel cell A fuel cell system comprising: a fuel gas supply flow path for supplying the fuel gas; and an oxidation gas discharge flow path and a fuel gas discharge flow path for discharging the oxidation off-gas and fuel off-gas discharged from the fuel cell.
Valves that are closed during the stop process of the fuel cell and prevent the gas from flowing back to the oxidant gas flow channel and the fuel gas flow channel in the fuel cell that have been decompressed include the oxidant gas discharge channel and the fuel gas discharge flow. A fuel cell system, which is provided downstream of a junction of roads.   The oxidant gas passage and the fuel gas passage in the fuel cell are both decompressed by reversely rotating the compressor while the valve is closed during the stop process of the fuel cell. The fuel cell system described.   The fuel cell system according to claim 2, wherein the valve is a check valve.   The fuel cell system according to claim 2, wherein the valve is an oxidizing gas pressure regulating valve.   5. The fuel cell system according to claim 1, wherein the valve is provided upstream of a gas-liquid separator for gas-liquid separation of the oxidizing off-gas and the fuel off-gas.   A fuel cell that generates electricity by an electrochemical reaction between an oxidizing gas and a fuel gas, a compressor that supplies the oxidizing gas to the fuel cell, an oxidizing gas supply channel that connects the compressor and the fuel cell, and a fuel gas that is supplied to the fuel cell At the time of stop processing of the fuel cell system, comprising: a fuel gas supply channel for supplying the fuel gas; and an oxidizing gas discharge channel and a fuel gas discharge channel for discharging the oxidizing off gas and the fuel off gas discharged from the fuel cell, The compressor is reversely rotated with the valve provided downstream of the junction of the oxidant gas discharge channel and the fuel gas discharge channel closed, and both the oxidant gas channel and the fuel gas channel in the fuel cell are depressurized. A stop processing method for a fuel cell system.

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