Optimum Size of Crushing Run-of-Mine Coals Prior to Washing for Metallurgical Use

For convenience of handling and operation, r.o.m. coals are normally crushed to some suitable size before treatment in washeries. This initial crushing often helps to release part of the dirt bands associated with coal. But crushing the coal to too small a size also brings in new problems. The apparent increase in the recovery of clean coal resulting from finer crushing is largely offset by a number of other factors. In this paper some of these important factors and other various considerations, which decide the optimum size of crushing raw coking coals prior to washing, are briefly discussed. On the basis of a critical study of the washability characteristics of the coking coals of the Jharia and Bokaro coalfields,the coals are classified into three categories. The size to which each category of these coals should be crushed, and the general schemes for their treatment have also been suggested here by the authors