Study on the oxidation reaction of gangue-containing coal under different oxygen concentrations

• Spontaneous combustion of coal in goaf areas is a common problem in global mines. • At present, there is a lack of relevant research on gangue containing coal. • The emissions of CO 2 and CH 4 from gangue containing coal are temperature-sensitive. • Significant differences in oxygen consumption rate and activation energy. Gangue Containing Coal, a heterogeneous mixture generated during composite coal seam mining, exhibits oxidation and kinetic characteristics critical to the study of spontaneous combustion of residual coal in goaf areas and the safety of mine operations. This study conducted temperature-programmed gas chromatography experiments under variable oxygen conditions using gangue containing coal samples from the 4–2# coal seam of Wanli No.1 Mine, elucidating its oxidation behavior and kinetic properties under different oxygen concentrations .Key findings include: Under constant oxygen conditions: CO₂ and CH₄ volume concentrations demonstrate significant temperature sensitivity. As temperature increases from 30 °C to 150 °C, both gases exhibit exponential growth (R² > 0.95). Beyond the critical threshold (120 °C), gas production rates enter a decay phase, forming a “thermal-promotion and high-temperature suppression” pattern. Under isothermal conditions (e.g., 80 °C, a representative oxidation zone): Reducing oxygen concentration from 21 % to 5 % decreases CO₂ volume concentration by 92 %, CH₄ by 63 %, and oxygen consumption rate from 0.053 mol·s⁻¹·L⁻¹ to 0.038 mol·s⁻¹·L⁻¹. Concurrently, the reaction activation energy increases from 3.076 kJ·mol⁻¹ to 4.175 kJ·mol⁻¹, indicating enhanced thermal stability under oxygen-depleted environments. These results provide a theoretical foundation for developing spontaneous combustion prevention technologies targeting gangue containing coal in adjacent composite coal seam goafs.