USE OF SURFACTANTS TO AID THE DEWATERING OF FINE CLEAN-COAL

Vacuum filtration of clean coal slurries and flocculated slurries with cationic, anionic and nonionic surfactants has been investigated. Sig nificant reductions in filter cake moisture content were obtained for all types of surfactant. The most effective surfactant was CTAB. The f inal moisture content of filter cakes was reduced from 21 to 11.7 wt% by using a moderate dosage of flocculant followed by surfactant pretre atment. Measurements of electrophoretic mobility, surface tension, ads orption, dewatering kinetics and kinetics of adsorption of surfactants were carried out. A direct correlation exists between the point of ze ro charge and residual moisture reduction in the filter cake. Test res ults show that surface tension by itself does not give much indication of the effectiveness of surfactants as dewatering agents. The enhance ment in filtration dewatering characteristics has been attributed to t he changes that surfactant adsorption causes in the wetting characteri stics of the coal surface. (C) 1998 Elsevier Science Ltd. All rights r eserved.