KSEF R&D Excellence: Improving Densification of Fine Coal Refuse Slurries to Eliminate Slurry Ponds

Increased mechanization in the underground coal mining has increased the volume of refuse (tailings) 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 attention ofGovemment as well as industry to look for a solution to avoid the spillage of slurry in the future. The proposed program will evaluate a new technique known as "Paste Thickening Technology", marketed by Eimco, which utilizes a DEEP CONE Thickener to discharges the waste slurry as a paste. The paste material could be stacked up at a low repose angle and would dry over a period oftime, thus avoiding the storage of slurries in ponds. The proposed study will be conducted as joint program between University of Kentucky Center for Applied Energy Research, Department of Mining Engineering, DORR-OLNER EJMCO and two coal companies, on two types of coal waste slurries obtained from different preparation plants. The .laboratory studies will involve characterization of slurries for their composition, particle size distribution, pH, zeta potential, and rheology (viscosity). Flocculation studies ofthe slurries will be conducted with respect to addition of various types offlocculants and percent solids in the slurries. Rhelogy ofthe flocculated material will be studied to identify the yield stress for various solid concentrations. This infonnation will be used to detennine the optimum solids concentration of solids in the slurry to obtain a thickened paste type product. Later on, a pilot-scale study using a 5£1diameter DEEP CONE thickener at one of the coal preparation site will be conducted, to obtain technical and economic data for a commercial installation and operation. It is anticipated that the out come of the study will be an effective and economical process for safe disposal of fine coal refuse and eliminating the old age problem of slurry pond spillage.