Structure characteristics of dewatered lignite from different drying temperature and time and effects on its behaviors of re-adsorbing moisture

Abstract

By changing the drying temperature and residence time, a series of different degree dewatered lignite samples were prepared in the fixed-bed reactor under inert gas and their adsorbing moisture behaviors were investigated under certain re-adsorption conditions. Using SEM, nitrogen adsorption and in-situ FTIR analysis methods, the structure changes of dewatered lignite were measured and associated with the drying and re-adsorption behaviors. The results show that the higher the drying temperature, the higher the drying efficiency and the more obvious structure change of dewatered lignite. But the moisture re-adsorption amount of dewatered lignite showed different changing trends. Under the drying condition of 140°C and 50min, the total moisture content of coal after moisture re-adsorption was the lowest. Most pores are mesoporous in lignite and the macropore structure collapsed into mesopore during drying. When the drying temperature was higher than 120°C, oxygen-containing functional groups began to decompose; with the increase of drying temperature and time, decomposition rate increased. The hydrophilic strengths of -OH and COOH groups are stronger than that of others.