Thermo-economic analysis of an efficient lignite-fired power system integrated with flue gas fan mill pre-drying

[EN] Lignite is a domestic strategic reserve of low rank coals in many countries for its abundant resource and competitive price. Combustion for power generation is still an important approach to its utilization. However, the high moisture content always results in low efficiencies of lignite-direct-fired power plants. Lignite pre-drying is thus proposed as an effective method to improve the energy efficiency. The present work focuses on the flue gas pre-dried lignite-fired power system (FPLPS), which is integrated with fan mill pulverizing system and waste heat recovery. The thermo-economic analysis model was developed to predict its energy saving potential at design conditions. The pre-drying upgrade factor was defined to express the coupling of pre-drying system with boiler system and the efficiency improvement effect. The energy saving potential of the FPLPS, when applied in a 600 MW supercritical power unit, was determined to be 1.48 %-pts. It was concluded that the improvement of boiler efficiency mainly resulted from the lowered boiler exhaust temperature after firing pre-dried low moisture content lignite and the lowered dryer exhaust gas temperature after pre-heating the boiler air supply.This work was supported by National Natural Science Foundation of China (NO. 51436006), the National Basic Research Program of China (973 Program, NO.2015CB251504), and the Fundamental Research Funds for the Central Universities.Han, X.; Wang, J.; Liu, M.; Karellas, S.; Yan, J. (2018). Thermo-economic analysis of an efficient lignite-fired power system integrated with flue gas fan mill pre-drying. En IDS 2018. 21st International Drying Symposium Proceedings. Editorial Universitat Politècnica de València. 261-268. https://doi.org/10.4995/IDS2018.2018.739326126