Theoretical Study of Supercritical CO2 Lignite-fired Power Plant Integrated With Heat Pump Pre-drying Lignite System

Lignite has high water content, and direct combustion for power generation has problems of low efficiency and large investment. Therefore, the supercritical CO2 lignite-fired power plant integrated with heat pump pre-drying lignite system was proposed and the coupled thermal calculation model for the supercritical CO2 cycle power cycle and the heat pump pre-drying lignite system was established. Then, based on a 660 MW reference case, the thermodynamic performances of the lignite direct-fired power plant and the lignite-fired power plant integrated with heat pump pre-drying lignite system are compared and analyzed. The results show that the heat pump drying lignite can increase the power generation efficiency by 1.44% and reduce the standard coal consumption rate by 8.06 g·(kWh)−1. Exergy analysis further shows that the heat pump drying lignite reduces the combustion exergy destruction of the boiler by 4.47% and reduces the boiler exhaust exergy loss by 0.35%, which increases the exergy efficiency of the lignite-fired power plant by 1.29%. And the reduction of the combustion exergy destruction and exhaust exergy loss of the boiler is the main reason for the energy saving. The higher the dryer efficiency, the lignite drying degree and heat pump COP, the more significant the energy-saving effect of the lignite-fired power plant integrated with heat pump pre-drying lignite system. © 2023 Science Press. All rights reserved.