Siemens Aktiengesellschaft

Helmut Stierstorfer

Erich Schmid

Uwe Lenk

Werner Schwarzott

Carl Lockwood

Hermann Br{umlaut Over (u)}ckner

A combined-cycle power plant includes a steam turbine having at least one low-pressure stage and a high-pressure stage, a feed-water preheater associated with the high-pressure stage, a bypass line connected in parallel with the feed-water preheater, a gas turbine operable with both gas and oil as fuel and having a flue-gas side, and a waste-heat steam generator disposed downstream of the gas turbine on the flue-gas side for generating steam for the steam turbine.

Combined-cycle power plant with feed-water preheater bypass

A steam generator, in particular a waste-heat steam generator, includes first and second evaporator heating surfaces located in an elongate gas flue for hot gas. A first supply line for feed water is throughflow-connected on an inlet side to the first evaporator heating surface, while the second evaporator heating surface is throughflow-connected on an inlet and an outlet side to a low-pressure drum. The low-pressure drum is provided with a second supply line for feed water. The first supply line has a first treatment point and the second supply line a second treatment point. Each of the treatment points serves for adding and/or extracting chemicals for water treatment, so that each evaporator heating surface can receive only feed water which is conditioned according to regulations applying to that evaporator heating surface. A method for operating the steam generator is also provided.

Steam generator, in particular waste-heat steam generator, and method for operating the steam generator

A method for operating a combined-cycle power plant includes utilizing heat contained in an expanded working medium of an associated gas turbine operable with both gas and oil as fuel, to generate steam for an associated steam turbine having at least one high-pressure stage. After a change of the operation of the gas turbine from gas to oil, feed water to be supplied to the high-pressure stage is divided into a first and a second partial stream, and only one of the partial streams is preheated. Particularly high plant efficiency may be achieved with the method, irrespective of the fuel being used for the gas turbine, at a low outlay in terms of apparatus and operational requirements. A combined-cycle power plant that is particularly suitable for carrying out the method includes a bypass line connected in parallel with a feed-water preheater associated with the high-pressure stage.

Method for operating a combined-cycle power plant

For achieving a high plant efficiency, a waste-heat steam generator, in particular for a combined-cycle power plant, has a number of heating surfaces heatable by a flue gas and carrying a medium to be heated. The steam generator can be operated at critical or supercritical pressures and has a once-through evaporator connected in countercurrent to the flue gas provided on a medium side. The evaporator is followed by a preheater and preceded by a superheater on a flue-gas side.

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Erlangen, Germany

Helmut Stierstorfer