Identification of Spontaneous Heating in Large Coal Stockpiles and Its Protective Measures

Abstract

Mine fire is a major problem faced by industries all over the world. Thousand million tonnes of coal are burnt and lost every year due to coal mine fire. It is concluded from the researches that coal catches fire due to spontaneous combustion i.e. natural and time-dependent phenomena. The propensity of Indian coals to catch fire is said to be between 9 to 12 months. Coal when exposed to air, react with oxygen and gradual self-heating of coal takes place. This interaction of coal with oxygen is an exothermic process, liberating heat. Therefore, there is a gradual accumulation of heat. In the case of the stockpile, a large amount of heat is accumulated as compared to dissipation. Thus, the accumulated heat enhances the coal temperature continuously and reaches to a point where self-heating occurs in a self propellant manner. This point of accumulation is termed as a hotspot and acts as an ignition point in piles. If we are able to know the mechanism of the spontaneous heating and its formation, then steps can be adapted to retard its propagation-cum transmission within the stockpile or in the mine. A huge amount of nature reserves can be saved. This project deals with the study of spontaneous heating liability of coals, and the process of heat generation in coal stockpile. Coal samples are collected from different coalfields in India. The in-situ properties of coal are studied through proximate analysis, crossing point temperature method (C.P.T) and wet oxidation potential (W.O.P) analysis. Numerical simulation of spontaneous heating is done by ANSYS software (Transient Thermal Analysis – T.T.A). The suggestive preventive measures are given on the basis of results obtained from different experiments including Differential thermal analysis and Flammability Test.