Evaluation of bench-scale pressure filtration when dewatering coal refuse slurry

Bench-scale pressure filtration testing was carried out to dewater coal refuse slurry. The test slurry was obtained from the thickener underflow stream of an operating coal preparation facility in Pennsylvania, which was processing bituminous coal. The slurry was being discharged into a slurry impoundment. Pressure filtration offers an option for dewatering the solids sufficiently to reduce or possibly eliminate the need for an impoundment. Moreover, filtration allows additional water to be recovered and reused in the cleaning facility, reducing the need for make-up water. Pressure filtration testing was carried out using approximately 90 mL slurry samples at pressures ranging from about 480 kPa to 900 kPa. Other test variables included slurry pH and temperature. Filtrate samples were collected as a function of time. For selected tests, the iron concentration of the filtrate was measured. The results indicated that filtration performance was affected by pressure and temperature. In addition, pH had a significant effect on filtration, with higher filtration rates and higher iron concentrations occurring at low pH values.