Experimental investigation on using antioxidants to control spontaneous combustion of lignite coal

To investigate the effects of antioxidants on the microstructure and characteristic parameters of coal during the oxidation process of coal, three antioxidants (tea polyphenols, resveratrol, and β-carotene) at different mass ratios (1 wt%, 3 wt%, 5 wt%, and 7 wt%) were selected to treat raw coal samples. Fourier transform infrared spectroscopy was conducted to explore the changes in functional group content before and after antioxidant treatment of coal samples. The results show that the content of functional groups in coal had a trend of decreasing and then increasing with a rising mass fraction of antioxidants, and the optimum mass ratio of antioxidants was predicted. On this basis, the effects of antioxidants on characteristic temperature points and gas products of coal samples were determined by the thermogravimetric-infrared experiment. The test results show that the critical temperature and dry cracking temperature of the antioxidant-treated coal samples increased to different degrees compared to the raw coal during the low-temperature oxidation stage. Meanwhile, the concentration and yield of CO, CO2, and CH4 of the antioxidant-treated coal samples showed a decreasing trend compared to raw coal. The chemical kinetics method was used to determine the apparent activation energy in the process of coal oxidation. The apparent activation energies of TP, Res, and β-Car inhibited coal samples in the stage of water evaporation and gas desorption increased by 39 %, 30 %, and 26 %, respectively, compared with the raw coal, while the apparent activation energies in the oxygen absorption and weight gain stage were respectively increased 19.4 %, 12.9 %, and 14.3 % higher than raw coal. The ability of antioxidants to inhibit the spontaneous combustion of coal is TP > Res > β-Car. The results enrich the research on antioxidant inhibition of coal spontaneous combustion and provide a theoretical basis for preventing coal spontaneous combustion.