Novel Findings on the Role of Polyphenolic Antioxidants in the Entire Process of Coal Spontaneous Combustion: Promotion of Coal Combustion at High-Temperature Stage

Current research on phenolic inhibitors primarily focuses on their suppression effects during the low-temperature oxidation stage of coal, while their role in postignition scenarios remains unexplored. This study investigates the thermal behavior and oxidation kinetics of bituminous coal mixed with tea polyphenols (TP) and tert-butylhydroquinone (TBHQ) during intense combustion. The results reveal that the addition of phenolic antioxidants exhibits a significant promoting effect on combustion, characterized by a lower ignition temperature and a higher extinction temperature. Kinetic analysis indicates that the apparent activation energy of the mixtures decreases with increasing conversion rates. The average activation energies for coal-TBHQ, coal-TP, and coal-TBHQ-TP systems are 177.99, 92.58, and 70.45 kJ/mol, respectively, with the ternary coal–TBHQ–TP system demonstrating the lowest activation energy. Molecular dynamics simulations further analyze key parameters, including system pressure, temperature, potential/kinetic energy, cluster evolution, radial distribution function (RDF), and indicator gas variations. After the system reaches a stable state, compared with the c0 system, the kinetic energy of the c3 system increases by 4000 kcal/mol, and the reduction in potential energy increases by 62 kcal/mol. When the simulation time reaches 1000 fs, the number of atoms in the largest molecular structure in the c3 system is 4 less than that in the c0 system, and the number of remaining oxygen molecules in the system decreases by 15. The findings suggest that the combustion process of the TBHQ–TP-added sample (c3) is more intense compared to the untreated sample (c0).