Variation of macro and microscopic characteristic parameters and kinetics of secondary oxidation of residual coal

Abstract

In order to investigate the spontaneous combustion characteristics of secondary oxidation of residual coal in the mining area, the changes of microscopic and macroscopic parameters during the secondary oxidation of raw and oxidized coals were compared using tests such as infrared spectroscopy and simultaneous thermal analyzer, and the kinetic parameters of secondary oxidation were calculated. The results show that the content of substituted benzene, -C=C-, -CH3, -CH2-, -CH3/-CH2-, -C=O and -COOH groups in the oxidized coal increases, while -CH, -OH and free radical concentrations, g-factor and line width decrease significantly. Compared to raw coal, the secondary oxidation of residual coal has a smaller characteristic temperature and heat absorption and a larger heat release, mass loss rate and overall combustion coefficient. The combustion processes of both raw and oxidized coals are consistent with primary reactions, but oxidized coal has a lower activation energy. On balance, oxidized coal has a greater propensity for spontaneous combustion and a greater risk of spontaneous combustion.

Keywords

• secondary oxidation
• ftir
• free radicals
• thermogravimetry
• differential scanning calorimetry
• kinetics parameters