Flotation performance analysis on coal washery rejects

Abstract

The coal washery rejects cause major environmental problems in various parts of the globe. Nearly 1 Mt of coal rejects discarded as waste, is accumulated per annum in India, during washing or cleaning of raw coal. Cleaning coal, especially washery rejects, has posed a major challenge to the recovery of fine coal. Froth flotation is a better choice for processing coal washery rejects. In this study, flotation studies are attempted on the coal slurry received from Sudamdih coal washery, Jharkhand, India. A statistical design package (Minitab V17) was used to study the effect of process variables like collector and frother dosages on the responses. Regression equations for froth height, froth density, recovery and ash content of clean coal were developed. The coefficient of correlation (R2) values between the experimental and the predicted values of the flotation responses was found to be greater than 0.98 for all the models. Clean coal product was analyzed for recovery, froth height, and ash content by varying pulp densities. Results show that the coal slurry sample could be evaluated with acceptable recovery via flotation. Clean coal with an ash content of 17.2% is obtained with a 70% recovery from 35.5% ash. The cleaned coal can be used in powder coal-consuming industries.