Study on the adsorption mechanism and staged inerting method of coal low-temperature oxidation gas under CO2-N2: Experiment and simulation

Coal spontaneous combustion poses a severe threat to mine safety, yet the underlying mechanisms governing CO2-N2 mixed gas injection for fire suppression remain insufficiently understood. This study employs temperature-programmed oxidation-mass spectrometry (TPO-MS) combined with molecular dynamics simulations to investigate gas adsorption behavior and oxygen-depletion kinetics during coal's low-temperature oxidation process. Three critical breakthroughs were achieved: (1) CO2 demonstrates superior adsorption capacity compared to N2, with concentrations exceeding 55 % significantly enhancing O2 displacement while suppressing CH4 liberation; (2) The 37 %N2–55 %CO2-8 %O2 mixture exhibits optimal performance, characterized by peak O2 desorption rates (−1.038 × 10−8), minimized activation energy barriers, and accelerated desorption threshold temperatures (<200 °C), revealing synergistic effects between physical dilution and chemical adsorption; (3) Atomic-scale simulations demonstrate that CO2 adopts a preferential adsorption configuration with 9.2 kcal/mol binding energy, while N2 displays anomalous interfacial behavior at specific concentrations. Based on these findings, a temperature-dependent injection protocol was developed, transitioning from CO2-dominated (N2: CO2 = 3:7) at <100 °C to pure N2 at >240 °C. This work establishes a scientific foundation for intelligent fire prevention systems in mining operations.