Evaluating Indian high-ash coals for coal-water slurry applications: A focus on rheology and characterization

Various types of coals are found in the earth's crust. In the Indian scenario, most of the coal is of high ash, so it is necessary to identify and categorize them for utilizing them efficiently to the maximum possible extent. Transportation; and burning raw chunks of coal efficiently is cumbersome, so it must be converted into slurry form to overcome these problems. So far, as per our knowledge, very little work has been done on Indian high-ash coal. This study aims to identify the best of the three different Indian high-ash coals (taken from one of the most coal-rich regions of India) through various characterizations and rheological analysis. The rheological analysis of CWSs confirmed a pseudo-plastic behavior (shear thinning). 52 % CWS prepared using SJ coal showed most acceptable apparent viscosity of 250–500 mPa·s at shear rate of 100 s⁻¹ and 30 °C. Herschel–Bulkley rheological model was used to fit rheological data, showing agreement with the experiments performed. Overall results indicate that Sijua (SJ) coal, and its slurries exhibit: higher carbon content, lower ash content, greater hardness, low density, better coking properties, few oxygen-containing compounds, better viscosity, and higher pH values compared to Madhuban (MB) and Pathardih (PTD) coals and their slurries. Therefore, SJ coal was identified superior among three coals taken in this study, as it seems able to generate high energy with less residual ash while PTD coal seems least favourable for the above-mentioned characteristics.