Assessment of the moisture storage characteristics of lignite focusing on lignite type, moisture forms and drying mechanism

To further study the occurrence form of moisture in coal, better understand the dehydration mechanism and the interaction between water and coal structure, as well as improve the utilization rate of lignite, non-isothermal and isothermal dehydration experiments were carried out on Zhaotong, Yimin and Zhundong coal samples under different initial conditions. The results showed that the dehydration rate of lignite is related to the temperature and initial water content. The effective moisture diffusion coefficient rises with an increase in temperature and water content. This indicated that the higher the temperature, the easier it is for water removal. In the isothermal dehydration experiment, the activation energy decreases with the increase of water content, indicating that the coal sample with large water content is easier to dehydrate, whilst the opposite result was obtained in non-isothermal dehydration experiment. According to the different drying mechanisms and characteristics at different stages, the total water content of lignite can be divided into four parts: chemical bound water, transitional bound water, physically bound water and free water. The removal mechanism and influencing factors of each have been analyzed in depth. The removal difficulty and required energy consumption is found to be successively reduced.