Method for cleaning steam system of combined cycle plant

A method for cleaning a steam system of a combined cycle plant including a gas turbine, a heat recovery steam generator configured to generate steam by utilizing heat of an exhaust gas exhausted from the gas turbine, a steam turbine driven by the steam from the heat recovery steam generator, a condenser configured to convert the steam exhausted from the steam turbine back to water, a condensate pump configured to raise a pressure of the water from the condenser, a main steam line configured to guide the steam generated in the heat recovery steam generator to the steam turbine, a steam stop valve provided in the main steam line and configured to stop an inflow of the steam into the steam turbine, a bypass line branched from a position closer to a side of the heat recovery steam generator than the steam stop valve in the main steam line is and connected to the condenser, a bypass valve provided in the bypass line, a condensate line configured to guide the water inside the condenser to the condensate pump, and a water supply line configured to guide the water whose pressure is raised by the condensate pump to the heat recovery steam generator, the method comprising:

• an intermittent operation processing step;
• and
• a commissioning processing step performed after the intermittent processing step,
• wherein the intermittent operation processing step includes
• a no-load operation step of supplying a fuel to the gas turbine, and performing a no-load operation on the gas turbine in a state where the steam stop valve and the bypass valve are closed,
• a pressure accumulating step of generating the steam in the heat recovery steam generator by utilizing the heat of the exhaust gas from the gas turbine, and accumulating the steam in a pressure accumulating region which is a portion closer to a side of the heat recovery steam generator than the steam stop valve in the main steam line is and a portion closer to the heat recovery steam generator side than the bypass valve in the bypass line is, during the no-load operation step,
• an intermittent blowing step of stopping fuel supply to the gas turbine, opening the bypass valve, and causing the steam inside the pressure accumulating region to flow into the condenser, after the pressure accumulating step, and
• a post-intermittent blowing foreign matter removing step of removing foreign matter inside the condenser and inside the condensate line after the intermittent blowing step, and
• the commissioning processing step includes
• a commissioning step of supplying the fuel to the gas turbine, and performing commissioning on the gas turbine, in a state where the steam stop valve is closed and in a state where the bypass valve is open,
• a continuous blowing step of generating the steam in the heat recovery steam generator by utilizing the heat of the exhaust gas from the gas turbine, and causing the steam from the heat recovery steam generator to flow into the condenser via a portion of the main steam line and the bypass line, during the commissioning step, and
• a post-commissioning foreign matter removing step of removing the foreign matter inside the condenser and inside the condensate line after a fuel supply to the gas turbine is stopped, after the commissioning step.