Study on the Reoxidation Characteristics of Soaked and Air-Dried Coal

Abstract

After coal seam mining, the residual coal is soaked with the accumulated water in goaf, and its spontaneous combustion characteristics were changed after air-dried. To study the reoxidation characteristics of soaked and air-dried coal, temperature-programmed experiments were carried out, and the cross point temperatures and index gases were investigated. Results showed that the cross point temperature of raw coal (146.3 °C) was reduced to 137.1 °C after it was pre-oxidized at 90 °C. The cross point temperature of water-soaked, and air-dried coal (96 h) was 122.5 °C, while the cross point temperature of water-soaked, air-dried (96 h) and pre-oxidized (90 °C) coal was 111.5 °C. Although CO was produced in the initial slow oxidation phase, it was found that C2H4 and C3H8 were not generated. In the rapid oxidation stage, different pretreatments affected the gas generation and the overall oxidative degree was consistent with the cross point temperature. The generation temperature and the concentration of C2H4 and C3H8 were decreased after the coal was water-soaked, air-dried, and pre-oxidized. Furthermore, the high-energy chemicals and functional groups were studied, which could be used to explain the physical experiment oxidation characteristics of different coals.