Characteristics and concepts of washing low volatile coking coals of jharia coalfields

Indian coals of Gondwana origin are heterogeneous in nature and constitute about seven percent of the world’s proven coal reserves. As on today, the total reserves of coal in india is 277 billion tones. Out of which about 83% constitute non-coking coal, 14% coking coal and the rest are others. Coking coal is an essential input for production of Iron & Steel through blast furnace route. To save steel industry facing acute dependence on imported coking coal, domestic availability of coking coal in desired quality has become imperative. The good quality coking coals of the upper seams are fast depleting leaving behind the inferior quality lower seam coal. The lower seam coals presently being mined are mostly low volatile coking coal (LVC). They constitute about 50% of the total coking coal reserves in India. These coals are characterized by high raw coal ash content and poor washability characteristics. In India, the first attempt to beneficiate the coking coals had come in to the horizon mainly to meet the requirements of steel industries and a chain of coking coal washeries had come in to existence since earlier 1950’s. Of the existing coking coal washeries, only three are less than 20 years old, whereas most are 40-50 years old. Beneficiation of the lower seam coals in the existing washery circuits (2 or 3 product) does not yield requisite quality demanded by the steel sector of the country and thus almost entire production is being supplied to the thermal power stations. This paper presents the detailed laboratory investigations in terms of characterization and washability followed by pilot plant studies carried out on typical high ash, difficult-to –wash LVC coal samples of Jharia coalfields from both Eastern & Western sector and suggests the concept of beneficiation for the improvement in the quality of ROM coal. The coking propensities and the petrographic analysis of the clean coal strongly support its use for the metallurgical purposes