Enhanced water removal from low-rank coal via flash evaporation: Insights into dewatering performance, upgrading effects, and energy analysis

Low-rank coal has vast reserves and is widely used in power plants. Nevertheless, its high moisture content reduces coal's heating value and power generation efficiency. This study explores an innovative steam flash-drying method, examining the impact of temperature, particle sizes, and heating duration on moisture removal. Investigations were conducted to assess the reabsorption behavior and changes in the heating value of the dried products, aiming to validate the method's suitability for coal upgrading applications. Additionally, the energy consumption of the drying process was thoroughly analyzed. The results showed that the drying effect exhibited a positive correlation with the steam pressure/temperature, and the particle size was an important factor affecting the dewatering effect, among which the drying effect of the 13-0 mm particles was the best, with a dewatering ratio of 70%. The holding pressure time exhibits minimal influence on dehydration effectiveness. Steam flash drying removed 73.5% of free water and 23.5% of bound water. Moisture reabsorption was virtually nonexistent within 96 hours of storage. The lower heating value of the coal was increased from 19.9 MJ/kg to 23.65 MJ/kg by drying. The energy consumption of steam drying was 1711 kJ/kg H2O. The results of this study verified the feasibility of steam flash steaming for low-rank coal drying and provided technical support for the safe, efficient, and low-energy quality improvement of low-rank coal resources.