Preparation and properties of hydrotalcite microcapsules for coal spontaneous combustion prevention

Microcapsule materials are a new type of composite fire-extinguishing material that show good effects in preventing the spontaneous combustion of coal. In this paper, polyethylene glycol 6000 (PEG6000) was selected as the wall material, and hydrotalcite (LDHs) was selected as the core material. Microencapsulated LDHs samples with different core-to-wall ratios were prepared by melting dispersion and condensation. Scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS), Fourier transform infrared spectroscopy (FTIR), thermogravimetry/differential scanning calorimetry (TG/DSC) and other experiments were used to characterize the surface morphology, dispersion, coating, pyrolysis and other characteristics of the microcapsules. On this basis, the microcapsules were mechanically mixed with a coal sample to prepare a chemically inhibited coal sample. Based on TG/DSC experiments, the effect of microcapsules with different core-to-wall ratios on the characteristics of coal spontaneous combustion was studied. Combined with thermokinetic parameters, the inhibition mechanism of the microcapsules with different core-to-wall ratios on coal spontaneous combustion was analyzed. The results showed that LDH-PEG6000 microcapsules were successfully prepared. The thermal reactivities and inhibition mechanism of microcapsules with different core-to-wall ratios were different, and the best effect was obtained when the core-to-wall ratio was 1:5. This microcapsule material can reduce the weight loss rate and heat release of coal, increase the critical temperature and maximum weight loss rate temperature by 8.8 °C and 33.6 °C, respectively, and increase the apparent activation energy of water evaporation and gas desorption stage by 13.42 kJ/mol and the thermal decomposition stage and combustion stage by 88.64 kJ/mol. Resistance microcapsules can effectively inhibit the coal spontaneous combustion reaction In addition, this research provides new ideas for solving the problem of coal spontaneous combustion in the goaf caused by the fully mechanized top coal caving technology and enriches the technical means of fire prevention.