Evaluation of Reduction Potential of Selected Heavy Metals from an Indian Coal by Conventional Coal Cleaning

Coal preparation can play an important role in reducing the emissions and discharges of toxic heavy metals that occur during utilization of coal. To evaluate the reduction potential of selected heavy metals by coal cleaning through gravity separation, a detailed study was conducted on a run-of-mine noncoking coal of the Indian origin. Different sizes of the crushed coal were subjected to float sink tests at specific gravities in the range of 1.30 to 1.80. Characterization data obtained from this study indicated that mercury, cobalt, and copper were dominantly associated with ash-forming constituents of the coal. Some elements, for example, selenium and cadmium, were found to be concentrated in the coal organic matrix. Characterization data also indicated that if the coal is washed at 1.70 specific gravity, the clean coal of improved quality will contain lesser concentrations of the toxic heavy metals. However, enrichment of selenium and cadmium was observed in the washed coal as compared to the feed coal.