Simulation for off-design performances of flue gas pre-dried lignite-fired power system

To investigate off-design characteristics of the lignite-fired power system integrated with flue gas drying, a whole-system boiler-turbine coupling simulation model is developed. The model is verified with the parameters under design conditions. It is found that flue gas pre-dried lignite-fired power system is endowed with remarkable energy-saving potential compared with the conventional lignite-fired power system. The plant thermal efficiency of a 600 MW unit increases by 1.56% (absolute variation) under design condition, and the standard coal consumption rate decreases by 9.58 g·(kW·h)^-1 accordingly. The off-design characteristics are simulated with variable power loads and lignite pre-drying degrees. The variation tendencies of the boiler operating parameters and system standard coal consumption rate are analyzed. The simulation shows that with the decreasing power load, the standard coal consumption rate increases; with the decreasing pre-drying degree, the theoretical combustion temperature and hot flue gas extracting ratio decrease, and the boiler exhaust temperature increases, which lead to a decreasing boiler thermal efficiency and an increasing coal consumption rate.