Quantitative analysis of oxidation characteristic indicators of coal with different metamorphic degrees

In order to study the changes of oxidation characteristics of coal with different degrees of metamorphism, the oxidation process of non-sticky coal (BN), gas-fat coal (QF) and 1/3 coking coal (1/3JM) was tested and analyzed by temperature programmed experiment system, the apparent activation energy of different oxidation stages was determined, and the change characteristics of spontaneous combustion limit parameters of coal were quantitatively calculated. The results show that the apparent activation energy of coal with low metamorphism is lower than that of coal with high metamorphism. The average apparent activation energy of BN, QF and 1/3JM coal samples is 39.90, 65.28 and 69.43 kJ/mol, respectively. The apparent activation energy of coal is positively correlated with its metamorphism, and the spontaneous combustion risk of coal with low metamorphism is higher; the apparent activation energy of the same coal at different stages is also different. The apparent activation energy of BN, QF and 1/3JM coal samples at stage 1 is 55.28, 75.05 and 80.79 kJ/mol, respectively, and that of stage 3 is 23.23, 59.07 and 61.50 kJ/mol, respectively, which decreases with the depth of oxidation reaction; the extreme temperature points of the three coal spontaneous combustion limit parameters are 50.3, 61.5 and 59.7 ℃, respectively. The extreme point temperatures of low-metamorphic coals are lower than those of high-metamorphic coals; under the same conditions, the minimum floating coal thickness and lower oxygen volume fraction of low metamorphism coal are smaller, the upper air leakage intensity is larger, and the spontaneous combustion is more likely to occur.