Thermal effect and kinetic analysis of secondary spontaneous combustion of pre-oxidized coal

Abstract

In order to study the secondary spontaneous combustion of coal treated with different pre-oxidation temperatures, pre-oxidized coals with different temperatures were prepared by temperature programmed device. The changes of functional groups of pre-oxidized coals were measured by Fourier transform infrared spectroscopy(FTIR). The thermal effect in the process of secondary spontaneous combustion of pre-oxidized coal samples was studied by differential scanning calorimetry, and the kinetic parameters of exothermic reaction were calculated. The results show that with the increase of pre-oxidation temperature, the characteristic temperatures in the process of coal secondary spontaneous combustion increase in varying degrees, and the heat absorption first increases and then decreases, while the maximum exothermic value, exothermic heat and activation energy in exothermic stage all show an upward trend, indicating that the exothermic reaction of coal is more intense after pre-oxidation. Pre-oxidation only changed the content of functional groups in coal, but did not affect the types of functional groups. After pre-oxidation, the -OH, -C=C- and -CH functional groups in coal decreased with the increase of pre-oxidation temperature, while -C-O-, -COOH, substituted benzene, -CH3 and -CH2- increased with the increase of pre-oxidation temperature. On the whole, after pre-oxidation, the active structure in coal increases and the risk of spontaneous combustion increases.

Keywords

• differential scanning calorimetry
• thermal effect
• kinetics
• activation energy
• fourier transform infrared spectroscopy (ftir)