Patent ID: 8001760

Claim:
A combined cycle plant including a compressor for compressing intake air taken in via an air intake duct, a gas compressor for compressing a fuel gas, a combustor for burning compressed air compressed by the compressor and the fuel gas compressed by the gas compressor, a gas turbine driven by a combustion gas obtained by combustion in the combustor, a waste heat boiler for recovering heat in an exhaust gas discharged from the gas turbine to generate steam, a steam turbine driven by steam generated by the waste heat boiler, and a condenser for condensing exhaust steam discharged from the steam turbine into water, a heat exchanger disposed in the air intake duct; a steam supply pipe for supplying steam generated in the waste heat boiler to the heat exchanger; a steam control valve interposed in the steam supply pipe; a return pipe for returning water discharged from the heat exchanger to the condenser; a drain tank interposed in the return pipe, and a water level control valve which is disposed in the return pipe nearer the condenser than is the drain tank; a temperature detector for detecting a temperature of intake air taken into the compressor; a water level detector for detecting a water level within the drain tank; and a control device for adjusting a degree of opening of the steam control valve so that the temperature detected by the temperature detector becomes a preset temperature, and also adjusting a degree of opening of the water level control valve so that the water level detected by the water level detector becomes a set water level which has been set beforehand.