Clean Coal Processes: Development of a Novel Process for Disposing Fine Coal Refuse Slurries to Eliminate Slurry Ponds

Increased mechanization in the underground coal mining industry has increased the volume of waste (refuse) generated by coal preparation plants. The fine refuse slurry, composed of coal and mineral matter, is usually disposed off in a holding pond (impoundment), which has to be maintained and monitored continuously. Incidents of impoundment breakthrough have drawn the attention of government as well as industry to look for a solution to avoid the spillage of slurry in the future. The proposed program would develop a new thickener that will discharge the waste slurry as a paste. The paste material could be stacked at a low-repose angle and would dry over time, thus avoiding the storage of slurries in ponds. The proposed study would be conducted as a joint program between the University of Kentucky and two coal companies, on two types of coal waste slurries obtained from different preparation plants. The laboratory studies would involve characterization of slurries for their composition, particle-size distribution, pH, zeta potential, and rheology (viscosity). Flocculation studies of the slurries would be conducted with respect to addition of various types of tlocculants and percent solids in the slurries. Rhelogy of the tlocculated material would be studied to identify the yield stress for various solid concentrations. This information would be used to determine the optimum solids concentration of solids in the slurry to obtain a thickened paste-type product. Later on, a pilot-scale study at one of the coal preparation sites would be conducted to obtain technical and economic data for a commercial installation and operation.