Combined cycle power plant having improved cooling and method of operation thereof

A combined cycle power plant comprising:

• a combustion turbine operable to burn a fuel to produce mechanical energy and hot exhaust gas;
• a heat recovery steam generator having a plurality of sections and operable to receive said hot exhaust gas and to produce steam at a plurality of pressures;
• a steam turbine operable to receive said steam and to produce mechanical energy;
• a means for directing a portion of said steam produced in a first of said sections to said combustion turbine to cool a portion thereof;
• a means for recirculating a blowdown flow from said first of said plurality of sections to a second of said sections.

A method of operating a combined cycle power plant having a combustion turbine system, a heat recovery steam generator, and a steam turbine system, the method comprising the steps of:

• providing said heat recovery steam generator with a plurality of sections;
• providing a plurality of boilers;
• operating said combustion turbine system to burn a fuel to produce hot compressed air, mechanical energy, and a flow of exhaust gas;
• directing said flow of exhaust gas through said heat recovery steam generator to produce from said plurality of sections a first plurality of steam flows at a plurality of pressures;
• directing a portion of said hot compressed air through said plurality of boilers to produce a flow of cooled compressed air and a second plurality of steam flows;
• directing said flow of cooled compressed air to cool a portion of said combustion turbine system.

A method of operating a combined cycle power plant having a combustion turbine system, a heat recovery steam generator and a steam turbine system, the method comprising the steps of:

• operating said combustion turbine system to burn a fuel to generate mechanical energy and a flow of exhaust gas;
• directing said flow of exhaust gas to said heat recovery steam generator;
• providing a plurality of sections as part of said heat recovery steam generator, said sections being operable to remove heat from said flow of exhaust gas to produce a plurality of steam flows at a plurality of pressures;
• providing a means for directing a portion of a first of said plurality of steam flows from a first of said plurality of sections to said combustion turbine system for cooling parts thereof;
• maintaining a blowdown flow from said first of said plurality of sections at a rate sufficient to maintain a quality of said first of said plurality of steam flows to a predetermined level;
• recirculating said blowdown flow to a second of said plurality of sections.