Synergistic inhibition effect and mechanism of an inhibitor for entire process inhibition of coal spontaneous combustion

Traditional coal spontaneous combustion (CSC) inhibitors, while effective, have limitations such as frequent application or short-term efficacy. To this end, we developed a slow-release and water-soluble synergistic inhibitor (SWSI) to achieve long-term CSC inhibition. The SWSI was formulated by integrating synergistic antioxidants (SA) composed of ascorbic acid (AsA) and Fe-superoxide dismutase (Fe-SOD) dissolved in a super absorbent polymer (SAP) encapsulated within hydrogel microcapsules. The effectiveness of SWSI was evaluated through simultaneous thermal analysis and in-situ free radical tests. The formulation optimization demonstrated that AsA and Fe-SOD had the maximum synergistic inhibition effect at a 1:1 molar ratio. The optimal SA: SAP ratio of 3:1 achieved the lowest oxygen consumption rate and highest inhibition rate. The encapsulation formulation, consisting of 3% SA, 6% PAM, 1% CaCl₂, and 0.5% citric acid, generated the highest swelling ratio. Simultaneous thermal analysis and in-situ free radical tests indicated that SWSI greatly increased feature temperatures and the apparent activation energy, lowered reaction heat, and substantially reduced free radical concentration in the full oxidation process. The newly developed SWSI offers a significant advancement in long-term CSC prevention by integrating physical and chemical inhibition, which provides sustained and effective inhibition throughout the entire oxidation process.