Review on Beneficiation of Indian Coal Using Solvents

It is well known that Coal is an important fossil fuel and is used as a major source of energy in power plants and blast furnaces, but minerals in coal inhibit the effective utilization of coals. These are kind of troublesome materials in the cumbustors by forming the ash during combustion of coal. Industrial demand of coal with minimum ash content so that it can be efficiently used in metallurgical process, or, power plants. This paper reviews the removal of ash-forming minerals of coal using solvents by chemical techniques. Solvents, like N-Methyl-2-pyrrolidone (NMP), 1-methyl naphthalene (MN), Dimethylformamide (DMF), Dimethyl sulfoxide (DMSO) can be used to reduce the ash content of coal. However, polar solvents have been proved to extract greater amounts of coal and reduce ash to a greater extent than non-polar solvents, particularly for lower rank or subbituminous coals. However, if non-polar solvents are used, then traces of polar additives can also increase the extraction of coal as well as cause greater reduction of the ash content. The degree of ash reduction depends not only on the solvent used, but also on the extraction temperature, time and rank of coals.