Comparative thermal behavior, Rock-Eval signature and kinetics of distinct thermally mature vitrain, fusain lithotypes and coals from India

Thermal and chemical properties of coals, and the lithotypes they contain, provide useful insight to their combustion and reaction behaviors. Analysis of thermal properties, proximate parameters, Rock-Eval signatures, and petrographic characteristics of vitrain, fusain lithotypes, and bulk coal samples of distinct ranks from Raniganj (high volatile bituminous A rank, HvbA) and Jharia (medium volatile bituminous rank, Mvb) basins (India) reveal contrasting features. The HvbA bulk coal is identified as the most reactive. HvbA and Mvb vitrains display comparable reactivities despite their distinct thermal maturities. Mvb vitrain generates spiky pyrograms, due to melt formation and bubble bursting typical of coking vitrains. Mvb fusian is more prone to self-heating, being characterized by an exothermic thermogram peak due to its greater propensity to adsorb oxygen. In contrast, HvbA fusain, with higher VM and ash, displays least reactivity. These features mean that Mvb coals require higher temperatures for ignition and consume more energy than HvbA coals. Multi-heating-rate Rock-Eval S2 pyrograms show excellent Arrhenius equation simulation fits for the HvbA and Mvb bulk coals and lithotypes, enabling determination of activation energies (E) and pre-exponential factors (A). Distinctive E and A values of the HvbA bulk coal are a consequence of its high liptinite content.