Evaluation of a pilot-scale, plate-and-frame filter press for dewatering thickener underflow slurries from bituminous coal-cleaning plants

Laboratory testing was conducted to evaluate the performance of a pilot-scale, plate-and-frame filter press for dewatering bituminous coal slurries. The fully automated filter press is manufactured by T.H. Minerals and is equipped with a hydraulic system, which operates the plate and diaphragm feed pumps. The filter press is capable of achieving an operating pressure of up to 1035kPa. The unit contains a single set of plates having a filtration area of 0.450.45m. Thickener underflow samples were collected from two bituminous coal-cleaning plants located in Pennsylvania. The first sample (Plant 1) was nominal -840μm and had an ash value of 39.2%. It contained approximately 34% of -25μm material with an ash value of 64.5%. The second sample (Plant 2) was nominal -150μm and had an ash value of 17.5%. It contained approximately 65% of -25μm material with an ash value of 20.9%. Testing was conducted to evaluate the effects of filter time, air-drying time, and air-blow pressure on filtrate flow, filtrate solids content, final cake moisture, and filter press unit capacity. For Plant 1, product moistures ranged from 23.5% to 25.6% with filtrate solids content ranging from 1% to 2% solids by weight. The unit capacities ranged from 45kg/hr/m² to 70kg/hr/². For Plant 2, product moistures ranged from 16.1% to 21.6% with filtrate solids less than 0.1% by weight. The unit capacities ranged from 117kg/hr/² to 168kg/hr/². In both cases, low cake moistures were associated with lower unit capacities. The results indicate that the filter press is capable of producing handleable filter cakes without the use of additional flocculants.