Electrostatic separation of ultrafinely ground low-rank coals

ABSTRACT Low-rank coals have an as mined ash content in the range of 10 to 30 per cent. It has been well documented that ash in these coals occurs as organically bound inorganics and as finely divided minerals which are dispersed throughout the coal structure. Consequently, burning some of these coals in conventional power plants may result in slagging of furnace walls and added costs for pollution abatement equipment. Coal cleaning by dry methods has special appeal where coal is utilized as dry solids since moisture removal after treatment and water pollution control are not required. Utilizing the differences in the electrostatic properties of finely ground coal and minerals is not commercially available but is one dry method with potential for further development. This method depends on the deflection of small particles by an electrical field with the positively charged particles moving in the direction of the field while the negatively charged particles move in the opposite direction. A key factor in ...