Comparison of spontaneous combustion behaviors of tar-rich and tar-inclusive coals

Abstract

As an unconventional hydrocarbon resource integrating coal, oil, and gas properties, tar-rich coal holds promise for advancing green and low-carbon utilization in the coal industry. The thermogravimetry and differential scanning calorimetry with different heating rates were employed to identify the combustion characteristics and oxidation reaction kinetics of coals. The research finds that the lower thermal thresholds accelerate tar-rich coal’s transition to ignition. At low heating rates, pyrolysis dominates tar-rich coal mass loss, the average activation energy for the pyrolysis of tar-rich coal exceeds that for tar-inclusive coal by more than 22.2 kJ·mol⁻¹. During the entire exothermic process, the E value of tar-rich coal in the thermal decomposition stage is 15·kJ-mol⁻¹ higher than that of tar-inclusive coal. In the combustion stage, the activation energy of tar-rich coal is 5 kJ·mol⁻¹ lower than that of tar-inclusive coal. This indicates that the hydrogen-rich structure makes its decomposition process have a higher activation energy, and the small molecules produced during the decomposition enable tar-rich coal to enter the combustion stage more quickly and efficiently. It provided a certain basis for the in situ thermal decomposition mining of tar-rich coal, ultimately facilitating the safe and sustainable utilization of this hybrid energy resource.