Inhibitory performance and mechanism analysis of modified fly-ash inhibitor on the coal spontaneous combustion: A combined study of laboratory experiments and molecular dynamic simulation

To effectively inhibit the occurrence and development of coal spontaneous combustion (CSC), ammonium polyphosphate was grafted onto fly ash cenospheres (FAC) through co-condensation, acid-base modification, and amidation to prepare a modified fly ash inhibitor (PMFAC) in this study. Then, SEM, TG-FTIR, in-situ FTIR, and molecular dynamics simulation were synthetically utilized to explore the inhibition effect and mechanism of PMFAC on CSC. The results demonstrated that the nitrogen- and phosphorus-containing compounds were successfully attached to the surface of PMFAC, which are effective components for inhibiting CSC. Besides, PMFAC effectively increased the characteristic temperatures in CSC process, and an addition of 45 % PMFAC increased the ignition point by 16 °C. The inhibitors can significantly inhibit the production of CO2, CO, CH4, and H2O during the CSC process. Additionally, PMFAC also had a strong inhibitory effect on hydroxyl, alkyl, and carbonyl groups involved in the reaction process. The Eα increased progressively with the increase of PMFAC concentration, with the largest growth rate reaching 64.4 %. The main reaction path of •OH/•O/O2 consumption during CSC under the action of PMFAC was obtained through molecular dynamics simulations. The research results have important theoretical and engineering significance for preventing CSC in goaf.