Abstract
A laboratory study of the formation of airborne respirable dust by the dropping of broken bituminous coal from a belt conveyor is described. It was found that about 10% of the respirable dust adhering to the broken coal becomes airborne owning to dislodgment upon impact. The specific formation of airborne dust is correlated empirically with the volume fraction of the falling coal, which is determined by the belt speed, the thickness of the coal layer on the belt surface, the material density, the bulk density, the angle of repose, the size of the broken coal, and the height of fall. Results are interpreted in terms of the shock dislodgement of dust particles adhering to the broken coal, and the dispersion of the dislodged particles by the surge of air from the space gaps in the impacting pieces.