Selective pressure kettle boiler for rotor air cooling applications

A system for use in a combined cycle power plant including a gas turbine and a steam turbine, the system comprising:

• a single kettle boiler that selectively receives feedwater from both a first source and a second source, a pressure of the feedwater in the first source being less than a pressure of the feedwater in the second source;
• and
• a valve system comprising:
• first and second inlet valves upstream from the kettle boiler that selectively deliver feedwater from the respective first and second sources to the kettle boiler;
• and
• first and second outlet valves downstream from the kettle boiler that selectively deliver steam from the kettle boiler to respective first and second steam receiving units;
• wherein, during a first mode of operation of the combined cycle power plant:
• the first inlet valve is open and the second inlet valve is closed such that feedwater from the first source is delivered into the kettle boiler but feedwater from the second source is not delivered into the kettle boiler;
• rotor cooling air extracted from a compressor section of the gas turbine is cooled with the feedwater in the kettle boiler from the first source and delivered back into a turbine section of the gas turbine, wherein at least a portion of the feedwater from the first source is evaporated in the kettle boiler by heat transferred to the feedwater from the rotor cooling air to create first steam;
• and
• the first outlet valve is open and the second outlet valve is closed such that the first steam is delivered from the kettle boiler into the first steam receiving unit but not to the second steam receiving unit;
• and
• wherein, during a second mode of operation of the combined cycle power plant:
• the first inlet valve is closed and the second inlet valve is open such that feedwater from the second source is delivered into the kettle boiler but feedwater from the first source is not delivered into the kettle boiler;
• rotor cooling air extracted from the compressor section of the gas turbine is cooled with the feedwater in the kettle boiler from the second source and delivered back into the turbine section of the gas turbine, wherein at least a portion of the feedwater from the second source is evaporated in the kettle boiler by heat transferred to the feedwater from the rotor cooling air to create second steam;
• and
• the first outlet valve is closed and the second outlet valve is open such that the second steam is delivered from the kettle boiler into the second steam receiving unit but not to the first steam receiving unit.