Study on the characteristics of secondary oxidation and the key reactive groups of fire area coal by different cooling rates

In order to reveal the effects of different cooling rates (slow and rapid) on the secondary oxidation characteristics of coal in coalfield fire area (primary heating to 180°C). Simultaneous thermal analysis (TG-DSC), programmed heating and in situ Fourier transform infrared (FTIR) experiments were used. Thermodynamic analysis as well as Pearson and gray correlation analyses were used to analyze the low-temperature oxidation processes in raw coal and in coal from the fire area that underwent different cooling rates. The results showed that there was a significant difference of coal. The maximum cumulative heat release of raw coal was 35.942 J. The slow cooling (SC) and rapid cooling (RC) coals were only 17.188 and 23.761 J. At 200°C, the CO production of the raw coal was 8,432 ppm, and the SC and RC coals were 521 and 1,166 ppm higher than it, respectively. In the correlation analysis, it was found that the key reactive groups in SC coal were -CH 2 and -COOH, whereas in RC coal it was -CH 2 . There are two fundamental reasons for the difference: (1) SC coal accumulated more -COOH groups. (2) The -CH 2 groups of RC coal are more easily oxidized than those of SC coal.