Simulation study on the part-load performance of steam pre-dried lignite-fired power system

Conventional lignite-fired power plants, firing lignite directly, have many shortcomings, including low efficiency and high investment. The pre-drying of lignite, using steam extracted from steam turbines as heat source, is a potential way to increase the power generation efficiency. Based on a 600MW reference case, the system simulation models were developed with Aspen Plus and validated in this paper. Then, the part-load performance of power systems was simulated and analyzed. Results show that the pre-drying could increase the combustion temperature of lignite, and decrease the acid dew point and flow rate of flue gas. The power generation efficiency of pre-dried lignite-fired power system decreases with the power load, and the descent rate of efficiency is bigger than that of conventional lignite-fired power system. As a result, the pre-drying of lignite is not energy saving when the power load ratio is smaller than 50%.