Study of the susceptibility of coal for spontaneous combustion using adiabatic oxidation method

Largest contributor for fires in a coal mill is due to presence of combustible materials in pulverisers. Dry coal that is accumulating or settling in pulveriser components can spontaneously ignite. Aim of this study was to investigate the effect of moisture content, relative humidity of airflow, airflow rates, coal size fractions, nitrogen suppression and prior oxidation on the susceptibility of coal for spontaneous combustion. Adiabatic oxidation method was adopted whereby spontaneous heating potential was measured according to total temperature rise (TTR) while considering temperature rise versus time. Results demonstrated that humidity of air is an important factor in deciding whether heating will progress or not. Particle size affected the TTR values whereby oxidation rate of coal increased with decrease in particle size up to a critical diameter below which dependence ceases. Total temperature rise recorded in the test varied with storage time. Findings of this study have identified factors responsible for spontaneous heating and could be incorporated in design of coal mills to prevent damage to equipment.