Evaluation of Pressure Filtration of Coal Refuse Slurry: A Fractional Factorial Design Approach

Pressure filtration provides an opportunity for dewatering coal refuse sufficiently to reduce or possibly eliminate the need for a slurry impoundment. In this study, pressure filtration was performed in a lab-scale unit to evaluate the dewatering nature of coal refuse slurry, which was obtained from a coal preparation facility. Evaluation of the process was performed using a fractional factorial design with cake moisture as the response and pressure, pH, and solids concentration as the variables of interest. Results indicated a decrease in cake moisture with increase in solids concentration and pressure, and an increase in cake moisture with pH. With pH playing a significant role in dewatering coal refuse slurry, zeta potential measurements were performed at different pH values to confirm the likeliness of agglomeration at lower pH. Filtrate flux values from the current test matrix were compared with the flux values of a bench-scale pressure filter, and a logarithmic relationship between the filtrate fluxes of the two units was developed. Results also indicated that for lower values of filtrate flux, the flux per discharge port remained constant during the scale-up from bench-scale to lab-scale units.