Chemically enhanced filtration and dewatering of narrow-sized coal particles

An experimental study of the filtration and dewatering of fine coal with and without additives was carried out. Filtration and dewatering behavior were determined using a vacuum filtration cell. The variables studied included the driving force, solids concentration, filter area, particle size and slurry pH. The effects of several flocculants, surfactants and hydrophobing additives (oils) on final moisture content of the filter cakes were determined. The investigations included determination of the rates of filtration and dewatering, assessment of the effects of additive type (anionic, cationic and nonionic), and establishment of optimum dosage of additives. Overall, it was found that the filtration and dewatering behavior were enhanced by increased driving force, higher initial slurry concentration, larger filtration area, larger particle size and lower slurry pH. Among surfactants and flocculating additives the anionic types were found to do the best job of filtration enhancement. At optimum dosages, the final cake moisture contents were reduced by 3.6% and 5.8% by weight using the appropriate surfactant and flocculant, respectively. However, the best filtration enhancements were achieved by addition of oils, which yielded cake moisture reductions of approximately 10% by weight.