Petrography of beneficiated heat altered coals from damodar valley coalfields, India

In Indian coalfields huge amount of naturally baked coals occur in various parts of the country and do not find judicious utilization potential in industries due to heterogeneously intermixed mineral matters with organic matrix. The macerals and their heat altered products occur in the form of isotropic and anisotropic carbons in association of some proportions of partially unaltered macerals. This ratio changes in different seams based on quality of original coal, tectonic conditions and pressure-temperature conditions prevailing in the coal seams during magma induration in the form of concordant sills and discordant dykes. In the present paper two case studies have been presented having different types of parent coals to observe the potential of beneficiation techniques for liberation of mineral matters and different carbon forms. In one case study Burragarh colliery in Jharia Coalfield having coking coal derived natural cokes and in another case samples were drawn from Damagoria colliery, which inhabits semi-coking coals. In the washed fractions at 50,25,13,06,03,0.5 mm at specific gravities 1.40 to 2.0, detailed petrographic studies including microtextures and microstructures were carried. Yield of washed coals and contents of macerals in both the case studies were found different. As a result their industrial utilization potential is also different.