Abstract: A combined cycle power unit (10) including a gas turbine (16), a heat recovery steam generator (HRSG) (34) to generate steam from an exhaust flow (24) of the gas turbine (16), and a steam turbine (64) driven by the steam generated from the HRSG (34). Steam generated in an evaporator (50) in the HRSG (34) is conveyed through an upstream superheater stage (46a) and a downstream superheater stage (46b) in the HRSG (34). The steam is then conveyed from the downstream superheater stage (46b) to the steam turbine (64). Between the upstream and downstream superheater stages (46a, 46b), the steam flow from the upstream superheater stage (46a) is throttled to a lower pressure to form a reduced pressure steam flow prior to entering the downstream superheater stage (46b) where the steam is reheated to an elevated temperature at the reduced pressure.

Abstract: A system and method for increasing the responsiveness of a duct fired, combined cycle power generation plant (12) via operating one or more gas turbine engines (14) at a part load condition less than 100 percent load, one or more steam turbine engines (16), and one or more supplemental burners (18) providing additional heat to a heat recovery steam generator (20) upstream from the steam turbine engine (16) is disclosed. The combination of the steam turbine engines (16) and supplemental burners (18) operating together with gas turbine engines (14) at a part load condition enables the system to quickly change output to accommodate changes in output demand of the duct fired, combined cycle power generation plant (12). By operating the one or more gas turbine engines (14) at a part load condition, the gas turbine engines (14) are able to be used to increase net output of the combined cycle power generation plant (12) faster than relying on increasing output via duct firing.

Abstract: A combined cycle power unit (10) including a gas turbine (16), a heat recovery steam generator (HRSG) (34) to generate steam from an exhaust flow (24) of the gas turbine (16), and a steam turbine (64) driven by the steam generated from the HRSG (34). Steam generated in an evaporator (50) in the HRSG (34) is conveyed through an upstream superheater stage (46a) and a downstream superheater stage (46b) in the HRSG (34). The steam is then conveyed from the downstream superheater stage (46b) to the steam turbine (64). Between the upstream and downstream superheater stages (46a, 46b), the steam flow from the upstream superheater stage (46a) is throttled to a lower pressure to form a reduced pressure steam flow prior to entering the downstream superheater stage (46b) where the steam is reheated to an elevated temperature at the reduced pressure.

Abstract: A system and method for increasing the responsiveness of a duct fired, combined cycle power generation plant (12) via operating one or more gas turbine engines (14) at a part load condition less than 100 percent load, one or more steam turbine engines (16), and one or more supplemental burners (18) providing additional heat to a heat recovery steam generator (20) upstream from the steam turbine engine (16) is disclosed. The combination of the steam turbine engines (16) and supplemental burners (18) operating together with gas turbine engines (14) at a part load condition enables the system to quickly change output to accommodate changes in output demand of the duct fired, combined cycle power generation plant (12). By operating the one or more gas turbine engines (14) at a part load condition, the gas turbine engines (14) are able to be used to increase net output of the combined cycle power generation plant (12) faster than relying on increasing output via duct firing.