Coal-Clay Triboelectrification

Experimental results are presented for the triboelectrification of coal-clay specimens in air at 20°C and 20.7 kPa. The coal was a vitrinite from Hat Creek, BC, and the clays were relatively pure kaolinite and montmorillonite. The cumulative charge after 100 contacts was much greater for kaolinite than montmorillonite in contact with the coal; however, the curves intersect each other after 10-30 contacts. Further work is under way to try to explain the unusual buildup in charge by an analysis of the volumetric charges and conductivity of the dry clays. The triboelectrification of coal-clay mixtures will play a major role in any contemplated electrostatic beneficiation of much of the coal which will be mined in Western Canada.