Study on the differences in the oxidation characters of two chinese coals

Abstract

The adiabatic oxidation test indicates that the self-heating rate of candle coal (YM) is higher than that of non-coking coal (DFS) in the initial stage, whereas it is lower than that of DFS coal in the later stage. These differences were analyzed based on the ¹H NMR spectra of the THF extracts, obtained under ultrasonic irradiation. Some active groups were found in these two coals, and some structural models were designed according to the ¹H NMR spectra of the THF extracts. The activation energies (E) and the enthalpy changes (ΔH) of the typical groups were calculated (by Gaussian 09W) to explain the differences in the oxidation characters for the two coals in this study. The results showed that the activation energy (E) for the reaction of , of which the YM coal contained more, and ArCH₂Ar and , of which the DFS coal contained more, was 4.33 kJ mol⁻¹, 37.53 kJ mol⁻¹, and 81.54 kJ mol⁻¹ and the change in the enthalpy values was 48.03 kJ mol⁻¹, 272.76 kJ mol⁻¹, and 78.01 kJ mol⁻¹, respectively, which can explain the differences in the oxidation of these two coals in the low-temperature stage. In conclusion, the differences in the self-heating rate are attributed to the different chemical structures and reactivity of the compounds present in the coals.