Fuel cell system

A fuel cell system comprising:

• a hydrodesulfurizer that removes a sulfur compound in a raw material;
• a fuel cell that generates power by electrochemical reaction using a fuel gas and an oxidizing gas, the fuel gas being obtained by reforming the raw material desulfurized with the hydrodesulfurizer;
• a heater that heats the hydrodesulfurizer by utilizing the heat of an exhaust gas circulated in the fuel cell system including the fuel cell;
• an introduction passage disposed to guide the exhaust gas to the heater;
• a gas supply unit that supplies a cooling gas to the exhaust gas, the cooling gas being a gas not utilized in the power generation in the fuel cell system, the fuel cell system being configured such that a mixture gas of the exhaust gas and the cooling gas supplied from the gas supply unit is passed through the inside of the heater;
• and
• a heat exchanger configured to heat the oxidizing gas to be supplied to the fuel cell by utilizing the heat of the exhaust gas,
• wherein the introduction passage is disposed to guide the exhaust gas heat-exchanged in the heat exchanger to the heater,
• the gas supply unit is configured to supply the cooling gas to a portion of the introduction passage located downstream from the heat exchanger and upstream from the heater, and
• the exhaust gas includes a combustion exhaust gas produced by the combustion of excess fuel gas and excess oxidizing gas unused in the power generation in the fuel cell.