Tar-rich coal is an unconventional hydrocarbon resource that integrates properties of coal, oil, and gas, offering potential for green and low‑carbon utilization in the coal industry. However, its high tendency for spontaneous combustion poses serious safety risks, including mine fires, production interruptions, and toxic emissions. Understanding its combustion behavior is therefore critical for both hazard prevention and resource recovery.
In a study published in ENG. Chem. Eng., researchers from Xi’an University of Science and Technology used thermogravimetry and differential scanning calorimetry at heating rates of 5, 10, 15, and 20 °C·min⁻¹ under dry air to analyze two coal types from northern Shaanxi: tar-rich coal (from Ningtiaota Coal Mine) and tar-inclusive coal (from Chenjiashan Coal Mine). Proximate and ultimate analysis confirmed that tar-rich coal has an H/C atomic ratio exceeding 0.8, indicative of its hydrogen‑rich molecular structure.
Seven characteristic temperature points were identified from the TG‑DTG curves. Tar-rich coal consistently showed lower characteristic temperatures than tar-inclusive coal across all heating rates, with differences ranging from approximately 5 to 17 °C. At a controlled heating rate of 5 °C·min⁻¹, the maximum heat absorption peak temperature of tar-rich coal was 50.4 °C, and the thermal equilibrium temperature was 112.7 °C; for tar-inclusive coal these were 47.2 and 102.4 °C, respectively. The maximum heat transfer peak temperature of tar-rich coal was 454.2 °C, while that of tar-inclusive coal was 476.1 °C. These results indicate that tar-rich coal reaches ignition and undergoes intense combustion at lower temperatures than tar-inclusive coal.
Gaussian deconvolution of the DTG curves resolved four stages: initial mass loss, oxidative mass gain, thermal decomposition, and combustion. For tar-rich coal at low heating rates, the pyrolysis reaction peak had the greatest influence on mass loss. The activation energy was calculated using the enhanced KAS method. During the thermal decomposition stage, the average activation energy of tar-rich coal exceeded that of tar-inclusive coal by more than 22.2 kJ·mol⁻¹. In the combustion stage, the activation energy of tar-rich coal was 5 kJ·mol⁻¹ lower than that of tar-inclusive coal. This indicates that the hydrogen‑rich structure of tar-rich coal makes its decomposition process have a higher activation energy, while the small molecules produced during decomposition enable tar-rich coal to enter the combustion stage more quickly and efficiently.
From a safety perspective, the lower characteristic temperatures and lower activation energy in the combustion stage mean that tar-rich coal can ignite and burn more readily once a fire starts. However, these same properties are advantageous for in‑situ thermal decomposition mining, where efficient combustion and heat release are desired. The findings provide a theoretical basis for both fire prevention strategies and the sustainable exploitation of tar-rich coal as a hybrid energy resource.

DOI
10.1007/s11705-026-2657-3