Insights on water temporal-spatial migration laws of coal gasification fine slag filter cake during water removal process and its enlightenment for efficient dewatering

Abstract Coal gasification fine slag is a kind of industrial waste produced from coal gasification process, and high-moisture coal gasification fine slag filter cake has brought challenges to environment and coal energy suatainable development. It is an important prerequisite for the development of fine slag efficient dewatering technology to investigate the water migration laws during the water removal process. In this study, the volume of water was ~56.95% of the filter cake according to the advanced micro-CT analysis which shows the spatial distribution information of water. The non-freezable water in the gasification fine slag filter cake occupied ~13 wt% which requires more energy to achieve the removal of this part of water. The larger water pore in the filter cake evolved into smaller pores in the drying process was confirmed which provides information for water migration behavior among pores. During the heating process, the change of weak hydrogen bonds intensity is more obvious than that of strong hydrogen bonds at the initial stage, implying that the different types of water have differences in the removal process. The hydrogen bond energy at 85 °C exceeds 40 kJ/mol, which is twice of that at 80 °C, indicating that more effective dewatering energy would be required in the future to remove water with strong hydrogen bonds. The investigations of water migration behavior and dewatering energy consumption provide potential guidance for efficient dewatering of gasification fine slag, which benefits to the environment and energy security.