Gas turbine fed with natural gas, introduced as a primary link of the coal-fired power plant for preheating the feed water, ensures positive energy and ecological effects. The energy effect has been expressed by means of the incremental energy efficiency, defined as the ratio of the increase of power to the chemical energy of the consumed gas. The reduction of CO2 emission has been also characterized by means of the incremental index. Formulae have been derived and numerical examples included.

gas turbine, combined power plant