A process for treating coal by the technique of heavy media

摘要

A process for improving coal by removing gangue (stone, shale, iron pyrites and the like) associated with the extracted coal as it leaves the crushers before subsequent treatment. The process described suspends the run-of-mine coal in a heavy medium, such as perchloroethylene, for a short period of time at ambient temperature or below (i.e. suspension times of 5 to 30 minutes at temperatures from 90 degree C to below -10 degree C) then allowing the solids to sediment out or float in a substantially still environment depending upon whether their inherent densities are respectively greater or less than the density of the heavy medium. After sedimentation the floating solids (largely coal having a low sulphur and ash content) are separated from the heavy medium in one flow and the sunken solids (mainly gangue) are separated as a second flow. Both these solids are washed with hot water (90 degree C to 100 degree C) and the azeotropic vapour formed is removed from the water and heavy medium mixture. The solids moistened with water are separated from the mass of hot water and are delivered for subsequent treatment or dispatch. The solids, both the coal and the gangue, have a heavy medium content of less than approximately 400 parts of heavy medium per million parts by weight of solids.