Comparison of the efficiency of the variants of a primary gas turbine supplementing a coal-fired power plant

Thermodynamic effects of four variants of the installation of a primary gas turbine supplementing a coal-fired power plant have been determined. The variants differ in the utilization mode of the heat recovery boiler of the gas turbine, which may be used to preheat the feed water of the steam power plant, but also for a secondary superheating of the steam. The introduction of an additional gas turbine expanding the working fluid down to a pressure lower than the ambient one with an additional compressor installed after the heat recovery boiler has been considered too. The reduction of exergy losses in the heat recovery boiler has been accepted as the main purpose of changing the scheme of the system. The new variants have been compared by means of the incremental energy efficiency of the gas turbine, characterizing the utilization degree of natural gas in the complex system.