Crushing coal during mining significantly increases the contact area of combustible components with atmospheric oxygen. The heat released during coal oxidation can lead to an increase in the temperature of the coal accumulation and the appearance of places of spontaneous combustion. For the timely prevention of endogenous fires, it is required to know the incubation period of spontaneous combustion, which is necessary for the coal accumulation to reach the critical temperature. Based on this parameter, the category of coal propensity to spontaneous combustion is established, and measures are developed to reduce the endogenous fire hazard.
The known method for estimating the incubation period does not sufficiently consider the influence of the environmental parameters on coal heating. The discrepancy between the calculated and actual duration is observed for coal at a negative temperature, for example, in the mines, and the open-casts in the permafrost areas, as well as in the warehouses in winter on a significantly large territory of Russia. Studies showed that a decrease in temperature significantly reduces the rate constant of oxygen sorption by the coal, and the release of heat in the coal accumulation. The process of spontaneous combustion of coal also slows down due to additional heat losses for the phase transition of water from solid to liquid state.
For improving the accuracy of calculating the incubation period of spontaneous combustion of coal at negative temperatures, it is proposed to consider the specific heat of melting ice, and to determine the oxygen sorption rate constant at a constant temperature from –10 to –20 ° C.
The influence of negative temperatures of coal accumulation increases the incubation period of spontaneous combustion of coal by 2–3 times allowing to reduce the cost of measures to prevent endogenous fires.
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