Oxygen-lean thermokinetics and early-warning of Laojunmiao non-caking coal in Xinjiang coalfield

Coalfield fire zones in Xinjiang exhibit oxygen-lean conditions caused by persistent endogenous combustion, which alters the spontaneous-combustion behavior of coal. This study investigated the thermokinetic characteristics of Laojunmiao non-caking coal under three oxygen-lean atmospheres (3%, 9%, and 15% O 2 ) and one atmospheric reference condition (21% O 2 ) using thermogravimetric-differential scanning calorimetry and temperature-programmed heating experiments. Five characteristic temperatures and three main oxidation stages were identified. With increasing oxygen concentration, thermal decomposition and oxidation shifted to lower temperatures, heat release intensified, the maximum exothermic peak moved 30–40 ℃ lower, and mass loss increased from about 84% to more than 92%. The full-process average activation energy obtained by the Kissinger method increased from 79.12 kJ/mol at 3% O 2 to 95.78 kJ/mol at 15% O 2 and then decreased to 92.77 kJ/mol at 21% O 2 . In combination with the stage-resolved Flynn-Wall-Ozawa/Kissinger-Akahira-Sunose(FWO/KAS) results, heat-release behavior, and index-gas evolution, approximately 15% O 2 was identified as a kinetic transition concentration from oxygen-limited oxidation to more active coal oxidation. Carbon monoxide dominated under strongly oxygen-lean atmospheres, whereas carbon dioxide and hydrocarbons formed earlier and in larger amounts when the oxygen concentration increased to 15% O 2 or the atmospheric reference level. An eight-stage early-warning index was established for the Laojunmiao fire zone, providing a basis for oxygen-control strategies and spontaneous-combustion prevention in Xinjiang coalfields.