Solid oxide fuel cell system

A fuel cell system comprising:

• a fuel cell;
• a gas reformer supplying a fuel gas to the fuel cell;
• a gas-water supply unit for supplying separately a reformer gas, an oxygen-containing gas and water to the gas reformer;
• a sensor for detecting a change in a condition of the fuel cell system while water is being supplied;
• a gas-water supply control unit for switching from supplying the water to supplying the oxygen-containing gas on the basis of the change detected by the sensor.

A method in a fuel cell system for supplying gas and water to a gas reformer which supplies a fuel gas to a fuel cell to generate an electric power, the method comprising steps of:

• supplying water and a reforming gas to the gas reformer to carry out a reforming reaction;
• detecting a change in condition of the fuel cell system while the water is supplied;
• and
• switching from water to oxygen-containing gas to the gas reformer on the basis of the change so as to maintain the reforming reaction to form the fuel gas.

A fuel cell system comprising:

• a fuel cell;
• a gas reformer connected to the fuel cell;
• a reforming gas supply unit for supplying a reforming gas to the gas reformer;
• a water supply unit for supplying water to the gas reformer in a normal operation of the fuel cell;
• an oxygen-containing gas supply unit for supplying an oxygen-containing gas to the gas reformer;
• wherein the oxygen-containing gas is supplied to the gas reformer when a shortage or possible shortage of the supplied water occurs.

A fuel cell system comprising:

• a fuel cell;
• a gas reformer supplying fuel gas to the fuel cell;
• a reforming gas supply unit for supplying reforming gas to the gas reformer;
• a water supply unit for supplying water to the gas reformer;
• an oxygen-containing gas supply unit for supplying oxygen-containing gas to the gas reformer;
• and
• a gas-water supply control unit controlling the water supply unit and the oxygen-containing gas supply unit;
• wherein the gas-water supply control unit allows the water supply unit to supply water to the gas reformer in a normal operation of the fuel cell, and allows the water supply unit to stop the water and the oxygen-containing gas supply unit to supply oxygen-containing gas to the gas reformer.

A method for operating a fuel cell system which comprises a fuel cell to generate an electric power and a gas reformer to supply fuel gas to the fuel cell, the method comprising:

• a steadily operating step of supplying water to carry out a reforming reaction with water and reforming gas;
• a switching step of introducing oxygen-containing gas to the gas reformer and stopping the water;
• an working step of perform engineering or maintenance work on supply-water line;
• and
• a resuming step of reintroducing water to the gas reformer and stopping the oxygen-containing gas after the work is finished.