Fuel cell system and scavenging method therefor

A fuel cell system comprising:

• a fuel cell stack in which a cathode gas and an anode gas are respectively supplied to a cathode gas passage and an anode gas passage so as to generate electric power;
• a scavenging gas supply device for supplying a scavenging gas to the fuel cell stack;
• an anode scavenging gas passage through which the scavenging gas for scavenging the anode gas passage flows;
• an anode scavenging control valve, which is provided at the anode scavenging gas passage, and opened when scavenging of the anode gas passage is started;
• a scavenging gas pressure control device for controlling the pressure of the scavenging gas;
• and
• a control part for controlling operations of the scavenging gas supply device, the anode scavenging control valve, and the scavenging gas pressure control device, wherein the control part controls the pressure of the scavenging gas by using the scavenging gas pressure control device in such a manner that when the anode scavenging control valve is opened, the pressure of the scavenging gas at the upstream side with respect to the anode scavenging control valve becomes lower than the pressure of the scavenging gas during the scavenging of the anode gas passage.

A scavenging method of a fuel cell system, wherein:

• the fuel cell system includes:
• a fuel cell stack in which a cathode gas and an anode gas are respectively supplied to a cathode gas passage and an anode gas passage so as to generate electric power;
• a scavenging gas supply device for supplying a scavenging gas to the fuel cell stack;
• and
• a scavenging switching valve for performing switching between first scavenging for performing scavenging by supplying the scavenging gas to one of the cathode gas passage and the anode gas passage, and second scavenging for performing scavenging by supplying the scavenging gas to the other one of the cathode gas passage and the anode gas passage;
• and
• the method comprises the steps of:
• performing the first scavenging;
• controlling the pressure of the scavenging gas by making the pressure of the scavenging gas at the upstream side with respect to the scavenging switching valve be lower than the pressure of the scavenging gas during the first scavenging;
• and
• switching the scavenging switching valve.