Study on the Stage Characteristics and Action Mechanism of Low-Concentration CO<sub>2</sub> in Inhibiting Coal Spontaneous Combustion
Ge Huang, Wei Gao, Fengwei Dai, Xun Zhang, Hanzhong Deng, Gang Bai
Abstract
High Resolution Image Download MS PowerPoint Slide This study examined the inhibitory mechanism of low-concentration CO 2 on coal spontaneous combustion using adiabatic oxidation experiments, thermogravimetric–differential scanning calorimetry (TG–DSC), and in situ Fourier transform infrared spectroscopy (FTIR). The analysis focused on heat release behavior, gas evolution, and functional group transformations in atmospheres containing 16% O 2 and 2–8% CO 2 . The results indicate that CO 2 inhibits coal oxidation by occupying surface-active sites and promoting endothermic desorption during heating, which extends the spontaneous ignition period by 38–110%. During the slow oxidation stage (ambient temperature to 70 °C), CO 2 significantly suppresses O 2 adsorption and aliphatic functional group oxidation, delays gas evolution, and extends the heating duration by 40–121%, accounting for 86–90% of the total ignition delay. In the accelerated oxidation stage (70–150 °C), increased CO 2 desorption partially offsets the exothermic effect; however, the reduced efficiency of active site blocking decreases the inhibition rate to 30–69%. In the intense oxidation stage, CO 2 desorption exceeds 90%. Although radical quenching still reduces the heat release rate by 16–20%, oxygen deficiency becomes the dominant limiting factor, rendering CO 2 inhibition largely ineffective. Overall, the effective suppression of coal oxidation at low temperatures highlights the potential of using flue gas as a cost-effective and environmentally sustainable fire prevention strategy.