Thermodynamic Study of Coupled Steam-Gas Turbine Plant With Steam Extraction and Injection

A type of coupled steam–gas turbine plant is proposed here. It is composed of a regenerative extraction steam turbine and a steam injected gas turbine. Extracted steam of the regenerative extraction steam cycle is not used to heat water through the regenerative feed–water heater as in conventional plant, but injected into a gas turbine to augment the output of the gas turbine, while the exhaust gas of the gas turbine now displaces the extracted steam to heat the feed water of the steam turbine plant. The proposed repowering turbine plant has two merits: the further utilization of extraction steam and the elimination of the complicated waste heat recovery boiler of a conventional steam injected gas turbine plant, in favor of a gas–to–water heat exchanger.