Study of Washability Characteristics of Some Indian Coals

Abstract

Coal is the prime fossil fuel in India and continues to play a vital role in the energy sector. Coal accounts for 60% of the commercial energy needs and 70% of electrical power in India comes from coal. Indian coals being of drift origin, contains large quantities of impurities which are intimately mixed, and poses serious challenges during utilization in industries. Coal is the least clean fossil fuel with respect to both local and global environment issues. The environmental impacts include those of the mining industry and coal transportation – on the landscape, rivers, water tables and other environmental media. Beneficiation of coal helps in not only improving the performance of power plants, but also reduces the transportation cost besides reducing the adverse effect on environment. In the present work, an attempt has been made to study the washability characteristics of different Indian coals by carrying out float-and-sink analysis. A total of 10 number of coal samples were collected from different coalfields using the channel sampling procedure. In addition, the proximate analysis, calorific value and hardgrove grindability index has also been determined in the laboratory by following standard procedures. It was found that Most of the coal samples contain high percentage of ash except the coal samples from NEC., which has the lowest ash content. The calorific value of the coal was increased after carrying out the float-and-sink method of coal washing. The MCL-2 and MCL-5 coal sample may be used without cleaning. At low specific gravities the yield of clean coals for most of the coal samples are very low. The amount of near gravity material present for most of the coals except NEC Coal sample is also very high, which makes the washing problem difficult to extremely difficult. The NEC coal sample is simple to moderate to wash compared to other coal samples used in this study. The CCL-2 coal sample may be washed with moderate difficulty.