Heat Effect of Oxidation of Aliphatic Hydrocarbon Groups on the Piecewise Characteristics and Spontaneous Combustion Tendency of Coal

Structure models of methyl and methylene were established and their reaction were analyzed. Gibbs free energy change and enthalpy change of the reactions were calculated using quantum chemistry analysis method. The results indicate that oxidation of aliphatic hydrocarbons can release heat of about 400 to 500 kJ/mol which is much larger than the reaction of oxygen-containing functional groups. Self-heating processes of coal was then divided into two stages. The chemical calculation results of aliphatic hydrocarbons are compared with the heat flow, oxygen consumption, gas production, and the results of the reaction of oxygen-containing functional groups. Their composition in coal was analyzed and it was concluded that the number of oxygen-containing functional groups determines the tendency of spontaneous combustion of coal, and the oxidation of aliphatic hydrocarbons is the key to an immediate increase in the temperature of coal.