Fuel cell system

Abstract

A fuel cell system includes: a fuel cell having an anode and a cathode; an oxidant gas flowpath supplying the oxidant gas to the fuel cell and discharging the oxidant gas from the fuel cell; a first shut-off valve disposed upstream from the fuel cell and having a first valve body; a second shut-off valve disposed downstream from the fuel cell and having a second valve body; a cathode control unit for sealing the cathode; and a scavenging unit for scavenging the anode by supplying the oxidant gas to the anode, wherein the cathode control unit, before scavenging the anode by using the scavenging unit, unseals the cathode by opening the first shut-off valve and the second shut-off valve. The fuel cell system is capable of preventing the valve bodies pressed against seat sections from being frozen even below the freezing temperature, and capable of avoiding a situation unable to restart a turned-off state of the fuel cell system.

1 . A fuel cell system comprising:
 a fuel cell having an anode to which fuel gas is supplied, and a cathode to which oxidant gas is supplied;   a first oxidant gas flowpath through which the oxidant gas is supplied to the fuel cell;   a second oxidant gas flowpath through which the oxidant gas is discharged from the fuel cell;   a first shut-off valve disposed upstream from the fuel cell and connected to the fuel cell through the first oxidant gas flowpath, the first shut-off valve having a first valve body;   a second shut-off valve disposed downstream from the fuel cell and connected to the fuel cell through the second oxidant gas flowpath, the second shut-off valve having a second valve body;   a cathode control unit for sealing the cathode by closing the first shut-off valve and the second shut-off valve after electro-chemical reaction is stopped from progressing in the fuel cell; and   a scavenging unit for scavenging the anode based on a predetermined condition by supplying the oxidant gas to the anode while stopping the electro-chemical reaction from progressing in the fuel cell, wherein   the cathode control unit, before scavenging the anode by using the scavenging unit, unseals the cathode by opening the first shut-off valve and the second shut-off valve.   
   
   
       2 . The fuel cell system as claimed in  claim 1 , further comprising a valve lock unit for locking the first valve body of the first shut-off valve and the second valve body of the second shut-off valve in open state after unsealing the cathode. 
   
   
       3 . A counter-freeze control method for a fuel cell system, the fuel cell system comprising:
 a fuel cell having an anode to which fuel gas is supplied, and a cathode to which oxidant gas is supplied;   a first shut-off valve connected to and disposed upstream from the fuel cell, the first shut-off valve having a first valve body;   a second shut-off valve connected to and disposed downstream from the fuel cell, the second shut-off valve having a second valve body;   a cathode control unit for sealing and unsealing the cathode by using the first shut-off valve and the second shut-off valve,   the method comprising the steps of:   stopping an electro-chemical reaction, which has been previously under way, from progressing in the fuel cell;   closing the first shut-off valve and the second shut-off valve to seal the cathode;   measuring temperature in the fuel cell;   determining whether the cathode control unit performs a counter-freeze-scavenging process based on the measured temperature, residual water remaining in the anode and the cathode being discharged by supplying oxidant gas to both the anode and the cathode in the counter-freeze-scavenging process;   unsealing the cathode by opening the first shut-off valve and the second shut-off valve;   maintaining the first valve body and the second valve body open; and   performing the counter-freeze-scavenging process.   
   
   
       4 . The method as claimed in  claim 3 , wherein
 the fuel cell system further comprises a valve lock unit which locks the first valve body and the second valve body in open state after the cathode is unsealed, and wherein   the valve lock system is used in the step of maintaining the first valve body and the second valve body in open state.