Research on the Retardant Effect of Deep Eutectic Inhibitor for Coal Spontaneous Combustion

To address the challenges of rapid water loss and insufficient long-term inhibition efficiency of conventional inhibitors in the high-temperature environments of deep goafs, a novel, environmentally friendly Deep Eutectic Inhibitor (DEI) was synthesized. This DEI utilizes citric acid (Ca) and proline (Pr) as the hydrogen bond donor and acceptor, respectively, with ascorbic acid (VC) and propyl gallate (PG) serving as antioxidants. A moisture retention evaluation model based on Fick’s law of diffusion was established to systematically investigate the liquid-domain stability of the DEI across a temperature range of 30 °C to 120 °C. The results demonstrate that the DEI exhibits superior moisture retention capabilities under high-temperature conditions, with the relative moisture retention peaking in the 80–110 °C range. Mechanistically, the formation of a robust hydrogen bond network effectively counteracts moisture evaporation driven by thermal kinetic energy. Furthermore, the DEI demonstrated significant inhibition effects on four coal samples with varying degrees of metamorphism. Tests on oxidative heat release characteristics revealed that DEI treatment delayed the initial oxidation temperature of the coal. Kinetic analysis further indicated that during the critical oxidation stage (200–300 °C), the apparent activation energy of the treated coal samples increased by 10.28–18.9 kJ/mol, effectively suppressing the spontaneous combustion process. This study contributes to the development of high-efficiency and eco-friendly fire prevention materials for coal mines.