A comparative study on the characterisation and combustion behaviour of high ash coals from two different geographical origins

Abstract

The ultimate use of coal is primarily dependent on the composition, distribution, modes of occurrences of the minerals and their association with the organics. Therefore, an adequate knowledge of the minerals, macerals and their ignition behaviour is inevitable for the subsequent utilisation of coal in various aspects. Here, we present a comparative characterisation and combustion study of two high ash non-coking coals (AH and BL) with ash yield of 42.42 and 45 wt% on dry basis and gross calorific value of 3620 and 3363 kcal/kg respectively. Both coals are rich in vitrinite with moderate liptinite and the volume percentage of inertinite is comparatively lower than the vitrinite. Both coals are rich in alumino-silicate minerals and Fe and Ti oxide are present in moderate concentrations. They have crystalline forms with discrete grain boundaries which make them susceptible for beneficiation. The fractionation characteristics like low slagging and fouling potential, high silica ratio and low base to acid ratio suggest that the two coals are feasible for their successive utilisation in thermal power plants. Concerning the macerals’s reactivity; BL coal has a comparatively lower TG peak temperature and burnout temperature than the AH. Also BL sample has relatively more volatile matter. Both coals have high ash fusion temperatures but BL coal ash consists of high proportion of refractory minerals e.g. SiO2, Al2O3 and TiO2. Hence, BL coal has better amenability for easy ignition and its combustion characteristics are expected to be improved than the AH.