A Novel Lignite Pre-drying System Incorporating a Supplementary Steam Cycle Integrated with a Lignite Fired Supercritical Power Plant

Abstract

A novel lignite pre-drying system incorporating a supplementary steam cycle integrated with a lignite fired supercritical power plant was proposed and thermodynamically evaluated using the EBSILON Professional software. Differing from the conventional pre-drying systems, the steam bleed for the dryer in the proposed system is drawn from the intermediate pressure turbine and put through a separated turbine called T-turbine. With the T-turbine installed, the superheating requirement of the bleed for the dryer and for some regenerative heaters is significantly reduced, thus leading to a further increase in the lignite fired power plant efficiency. The simulation results show that the net power plant efficiency improved by 2.6% and the cost of electricity reduced by up to 1.26 $/MWh can be achieved, compared with the reference case. The exergy destruction can also be significantly reduced in the proposed lignite pre-drying system. The concept of the novel integrated system may provide a promising method for lignite pre-drying in the future generation lignite power plants.