Stage inhibition characteristics of composite inhibitor in process of inhibiting coal spontaneous combustion

In order to solve the defects of weak inhibitory effect and short action time of single inhibitor, sodium bicarbonate was selected as physical inhibitory component and high-efficiency antioxidant tea polyphenol as chemical inhibitor based on the resistance characteristics of the two substances at different stages, and carried out experimental research on the optimization of composite inhibitor.Using TG-DSC and FTIR experiments, combined with oxidative kinetic analysis methods and peak fitting technology, the effects of composite chemicals on the characteristic parameters and microscopic groups of coal oxidation process were analyzed.The high efficiency inhibition effect of composite inhibitor on coal spontaneous combustion was verified from macro and micro aspects, and its micro inhibition mechanism was revealed. The results show that the six characteristic temperatures of the inhibited coal samples are higher than that of the raw coal, the mass loss is reduced, the heat absorption of coal increases in the low temperature oxidation process, the heat release of the coal body decreasesat the high temperature stage, and the flammability index and comprehensive combustion index are significantly reduced. The apparent activation energy of coal samples in the four stages of the oxidation process is improved, and the optimal ratio of composite inhibitor is obtained by analysis (sodium bicarbonate: tea polyphenol=3∶1). By quantitatively analyzing the change law of the active functional groups of the raw coal and the inhibitory coal samples during the oxidation process, it is concluded that the addition of the composite inhibitor reduces the active groups (hydroxyl, methyl and methylene) in the coal and the coal-oxygen complex. The content of reaction intermediates (carboxyl group, carbonyl group) and the content of stable functional group ether bondsalso increase. In the process of coal oxidation at low temperature, sodium bicarbonate thermally decomposes to form CO2, which achieved physical inerting and inhibited coal spontaneous combustion through the competitive adsorption effect of CO2-O2 on the surface. In the process of coal combustion at high temperatures, hydroxyl groups in tea polyphenols consume active groups on the surface of coal and form ether bonds, which can inhibit the spontaneous combustion of coal by interrupting the chemical reaction process.