Single shaft combined cycle power plant start-up method and single shaft combined cycle power plant

A start-up method of a single shaft combined cycle power plant comprising:

• a gas turbine that is driven by combustion gas and discharges exhaust gas;
• an exhaust heat recovery boiler that uses the exhaust gas from the gas turbine as a heat source and includes:
• a high-pressure drum for generating high-pressure steam;
• a low-pressure drum for generating low-pressure steam having a pressure lower than that of the high-pressure steam;
• an intermediate-pressure drum that generates intermediate-pressure steam having a pressure lower than the pressure of the high-pressure steam and higher than the pressure of the low-pressure steam;
• and
• a reheater that generates high temperature reheated steam;
• a high-pressure steam turbine that is coaxially arranged with the gas turbine and driven by the high-pressure steam fed from the high-pressure drum via a high-pressure steam control valve;
• a low-pressure steam turbine that is coaxially arranged with the high-pressure steam turbine;
• a power generator that is coaxially arranged with the low-pressure steam turbine;
• an intermediate-pressure steam turbine that is coaxially arranged with the high-pressure steam turbine and the low-pressure steam turbine, and driven by the high temperature reheat steam from the reheater;
• a low-pressure turbine steam supply system that has a low-pressure main steam control valve and that feeds a mixture of steam from the low pressure drum through the low-pressure main steam control valve and steam that has been adiabatically expanded in the intermediate-pressure steam turbine;
• a start-up boiler that generates auxiliary steam;
• a start-up time auxiliary steam supply pipe that connects the start-up boiler with the low-pressure turbine steam supply pipe at an upstream side relative to the low-pressure main steam control valve and feeds the auxiliary steam at start-up time;
• an auxiliary steam flow control valve that controls a flow rate of steam fed from the start-up time auxiliary steam supply pipe to the low-pressure turbine steam supply pipe;
• and
• a low temperature reheat system that feeds steam from the high-pressure steam turbine together with the intermediate-pressure steam from the intermediate-pressure drum to the reheater, wherein
• during a time period from when the gas turbine is started up to when a rotation speed of the gas turbine reaches a rotation speed allowing self-sustained operation using the combustion gas, the auxiliary steam from the start-up boiler is fed to the low-pressure steam turbine via the low-pressure turbine steam supply system by controlling a valve opening degree of the auxiliary steam flow control valve to allow the low-pressure steam turbine to generate a drive force to thereby perform speed-up control in a unified manner for the gas turbine, the high-pressure steam turbine, the intermediate-pressure steam turbine, the low-pressure steam turbine, and the power generator.