An efficient solar-aided waste heat recovery system based on steam ejector and WTA pre-drying in solar/lignite hybrid power plants

Abstract

An efficient solar-aided waste heat recovery system based on steam ejector and WTA pre-drying was proposed. In the proposed system, solar energy collected by parabolic trough collector is used to generate a little high-grade steam, inducing steam waste heat in steam ejector and producing large amount of medium-grade drying steam. By absorbing waste heat in steam ejector and integrating with coal pre-drying, the solar energy could be considered amplified in the steam ejector and converted into the dried coal’s heating value. The results reveal that, for a typical 1000 MW lignite-fired power plant, 46.6 MWth of steam waste heat could be recovered efficiently by collecting 21.6 MWth of solar energy. The proposed system could produce 36.2 MWe of additional power with 1.62% of thermal efficiency increase. The cost of solar generated electricity of the proposed system is 0.028 USD/kWh, which is significantly lower than that of the conventional parabolic trough concentrating solar plants and solar-aided power generation system. The off-design performance reveals that the proposed system could solve the fluctuation of solar energy by dried coal storage.