COMBINED CYCLE POWER GENERATING PLANT AND METHOD OF SUPPLYING COOLING STEAM FOR GAS TURBINE IN SAME

摘要

A combined cycle power generating plant comprising in combination a gas turbine plant (10) and a steam turbine plant (40), wherein a cooling steam is appropriately controlled in temperature to thereby provide a turbine which can be manufactured with the use of easily available materials. Steam from a medium pressure evaporator (26) is supplied into a cooling steam supply path (14), through which an exhaust gas from a high pressure turbine (41) is supplied to a high temperature portion (11a) of a gas turbine as a cooling steam, to be mixed with the exhaust gas, whereby the cooling steam is lowered in temperature without reduction in the overall efficiency to enable use of a material of degraded heat resisting performance as a material for formation of the gas turbine high temperature portion (11a) which is in contact with a portion being cooled, so that a relatively inexpensive, easily available material can meet design and manufacture requirements.