Maceral Liberation and Distribution of Bituminous Coal for Predicting Maceral-Separation Performance

The success of gravitational separation of coal macerals for a given coal is dependent on the liberation and distribution of macerals. On a basis of four coals of varying ranks from high-volatile bituminous coal to low-volatile bituminous coal, this article presents the maceral liberation and distribution under various crushing degrees and predicts the maceral separation performance with various separation techniques. The determination of the Hardgrove Grindability Index of maceral concentrates was also performed. The liberation and distribution results show that vitrinite tends to be concentrated in particles with lower density and finer size, and good liberation performance of high-volatile bituminous coal is achieved by crushing to -3 mm. The medium-volatile bituminous coal behaved differently than the other three coals, which is confirmed by the relationship between HGI and coal rank as well as maceral composition. The prediction results show that there is good performance for high-volatile and low-volatile bituminous coals using the technique of crushing to -3 mm + density-based separation while good separation performance of medium-volatile bituminous could be achieved using a technique of 50 x 0.5 mm + density-based separation, not necessarily crushing. This study provides theoretical support of rational utilization of the coking coals using maceral separation.