Research on the combustion characteristics of coal with different degrees of high-temperature oxidation

In view of the possibility of reignition of coal through inhibited oxidation reactions after contact with oxygen, the oxidation characteristics of coal at different oxidation degrees were studied using a self-built oxidation experiment system as well as ESR and FTIR instruments. The results indicated that the oxygen consumption rate and formation rate of carbon and oxygen gases increased rapidly in the range of 210°C to 430°C, the oxidation rate slowed down when the coal was pre-oxidized at 180°C, and the oxidation rate reached the maximum at 330°C as well as 380°C. When the final temperature of the coal samples reburning at 230°C and 330°C was 430°C, the difference among g factor, line width, and free radical concentration was the largest. With the increase in oxidation degree, the maximum difference of C-O peak area was 14.3%, the maximum difference of OH area was 1.1%, and the maximum difference of C=O area was 18.8%. When the peak area ratio of functional groups turned over, the preoxidation temperature was higher than 230°C. With the increase of the preoxidation temperature, the oxidation activity of coal was enhanced, and spontaneous combustion was more likely to occur. The research findings hold theoretical significance for ensuring safe fire zone opening procedures and preventing reignition in coal mine fire areas.