Gas turbine combined plant, method of operating the same, and steam-cooling system for gas turbine hot section

Abstract

A gas turbine combined plant, a method of operating the same, and a steam-cooling system for a gas turbine hot section are provided, whereby the generation of thermal stress can be utmost reduced. A gas turbine hot section steam cooling system (,) is designed to cool a hot section (,) of a gas turbine unit (,) by the steam of an exhaust heat recovery boiler (,) and to supply the steam after cooling into a steam turbine (,). The system (,) comprises: a temperature detectors (,) for detecting the outlet temperature of the steam of the gas turbine hot section and the outlet temperature of the steam of the exhaust heat recovery boiler, respectively, at the start-up time of the gas turbine; and a shielding valve (,) disposed to a pipe (,) supplying the steam after cooling the gas turbine hot section to the steam turbine for shielding the steam after cooling in the case where there is a substantial difference between the both temperature levels. A regulating valve (,) is disposed to the pipe (,) connecting the gas turbine hot section to a condenser (,) such that the steam after cooling may be recovered to the condenser in the case where there is a substantial difference between the both temperature levels.