Abstract:Lignite has the characteristics of high moisture and low heat value, thus it could improve the quality of lignite through predrying treatment, and then improve the thermal efficiency of boiler and reduce the coal consumption of power generation. Taking a certain lignitefired 600MW super critical direct aircooled generating unit as an example, this paper built a thermoeconomic analysis model for steam extraction predried lignitefired power system. Under the condition of fixed main steam flow, when the moisture(as received basis) of lignite decreased from 38.4% to 15.0%, the thermal efficiency of boiler increased from 91.5% to 92.9%, which saved wet lignite 22g/(kW·h).

Keywords:coalfired power station, direct aircooled generating unit, lignite predrying, thermoeconomy