Thermokinetic characteristics of coal spontaneous combustion of Jurassic coal from China

Jurassic coal samples from two coal mines were selected for oxidative thermal energy experiments. By using a temperature-programmed experimental system, the variation of gaseous products was obtained, and the changes in thermal energy release with temperature were measured. Thermokinetic parameters, such as apparent activation energy (E_a) and pre-exponential factor (A), of the coal samples under four different heating rates, were determined by thermogravimetric analyzer. The results showed that during the low-temperature oxidation stage, the index gas (CO) used to characterize the spontaneous combustion state of the coal body was roughly the same as the temperature curve of the two samples with the temperature change, but the critical temperature was different. The WD sample produced less CO gas. However, the maximum and minimum exothermic strengths of the two samples showed similar to temperature change curves. The characteristic temperatures for coal were discovered using different heating rates. For the WD sample, the characteristic temperature varied according to the heating rate. For the same type of sample, the TG and DTG curves lagged with an increase in heating rate. Characteristic temperatures T1−T5 had an increasing tendency with an increase in heating rate. As one of the integral methods, Coats-Redfern integral method was adopted to capture the thermokinetic parameters of the samples. The straight line fitting by this method was higher. The heating rate conditions increased from 2 to 15 °C min^-1 when the oxygen concentration was 21 vol%, the apparent activation energy of the samples decreased with an increase in the heating rate.