Fuel cell system and method of running fuel cell system

A method of running a fuel cell system which includes a solid oxide fuel cell, a combustor, a reformer, a first temperature detector, and a second temperature detector configured to detect a temperature of the fuel cell, the method comprising:

• in the solid oxide fuel cell which includes a cathode and an anode, generating power by using, as fuel, air supplied to the cathode, and a hydrogen-containing gas supplied to the anode of the fuel cell;
• in the combustor, generating a combustion exhaust gas by combusting an anode-off gas discharged from the anode of the fuel cell and a cathode-off gas discharged from the cathode of the fuel cell;
• in the reformer, steam-reforming a material, and thereby generating the hydrogen-containing gas supplied to the anode of the fuel cell;
• in the first temperature detector, detecting a temperature of at least one of the combustion exhaust gas and the combustor;
• and
• if the temperature detected by the first temperature detector is lower than a preset threshold while the combustor is forming flame, performing at least one of:
• an operation of increasing a ratio of the air consumed by the cathode of the fuel cell to the air supplied to the cathode of the fuel cell, and
• an operation of decreasing an amount of water supplied to the reformer,
• wherein if the temperature detected by the first temperature detector is lower than the preset threshold, a controller is configured to perform the operation of increasing the ratio of the air consumed by the cathode of the fuel cell to the air supplied to the cathode of the fuel cell such that the temperature detected by the second temperature detector does not exceed a preset fourth threshold, and
• wherein the controller performs the at least one operation if the temperature detected by the first temperature detector is lower than the preset first threshold, and thereafter stops run of the fuel cell system if the temperature detected by the first temperature detector is a temperature lower than the preset first threshold, and is lower than a third threshold which is set in advance at a temperature below which the combustor loses the flame.