Patent ID: 8715874

Claim:
A fuel cell system comprising: a fuel cell including an anode, a cathode, and an electrolyte membrane disposed between the anode and the cathode, the fuel cell being configured to generate electrical power through electrochemical reactions between a fuel gas supplied to the anode and an oxidant gas supplied to the cathode; an oxidant gas supplying device configured to supply the oxidant gas to the cathode of the fuel cell; an oxidant gas backpressure regulating device configured to regulate the pressure of the oxidant gas at the cathode of the fuel cell according to a valve opening, the oxidant gas backpressure regulating device being disposed downstream of an oxidant gas outlet of the fuel cell; a first pressure detecting device configured to detect the pressure of the oxidant gas at the cathode of the fuel cell; and a controller comprising a microcomputer and a control program for controlling the fuel cell system during a start-up fuel gas disposal process, the controller being programmed to perform the following operations during startup: control the oxidant gas supplying device to supply the oxidant gas at a standard oxidant gas flow rate, wherein the standard oxidant gas flow rate is an optimum value determined based on a power consumption of the oxidant gas supplying device, a noise and vibration of the oxidant gas supplying device, and a startup time; control the valve opening of the oxidant gas backpressure regulating device to a first target valve opening, wherein the first target valve opening is a fixed minimum valve opening amount that allows for a non-zero flow rate of oxidant gas that is less than the standard oxidant flow rate to be exhausted from the cathode; and control the valve opening of the oxidant gas backpressure regulating device to a second target valve opening which is greater than the first target valve opening when the pressure of the oxidant gas detected by the first pressure detecting device reaches an elevation target pressure wherein the second target valve opening is a fixed value sufficiently large that an amount of oxidant gas equal to or larger than the standard oxidant gas flow rate is exhausted from the cathode; thereby diluting with oxidant gas any fuel gas that has permeated through the membrane from the anode to the cathode during a previous shut-off period of the system.