The Stage Inhibition Characteristics Of Composite Inhibitor In The Process Of Inhibiting Coal Spontaneous Combustion

The inhibitor is the primary means of inhibiting spontaneous coal combustion hazards.Considering the disadvantages of weak inhibitory effect and short action time of the single inhibitor,this paper used sodium bicarbonate as the physical inhibitory component and high-efficiency antioxidant tea polyphenols as the chemical inhibitor based on the different phases of the inhibitory characteristics of the two substances,and carried out an experimental research on the optimization of composite inhibitor.The high efficiency inhibition effect of composite inhibitor on coal spontaneous combustion was verified at macro and micro levels using thermogravimetric-differential scanning calorimetry combined experiments and in-situ Fourier infrared spectroscopy experiments,and its micro inhibition mechanism was revealed.The characteristic temperature,combustion chara cteristics parameters,exothermicity,kinetic parameters and other oxidation characteristics parameters of the coal samples with different propo rtions of composit e inhibitors were analysed and compared by TG-DSC experiments.The results show that the composite inhibitor has a significant inhibitory effect on coal spontaneous combustion.Sodium bicarbonate mainly acted in the water evaporation and mass gain through oxyg en adsorption stages during the coal oxidation process.Tea polyphenols acted on the pyrogenic decomposition and combustion stages during the coal oxidation process.All six characteristic temperatures of the inhibited coal were increased and the mass loss was reduced compared to the original coal.The heat absorption of the inhibited coal increased during the low-temperature oxidation process,and the heat release decreased during the high-temperature stage.Both the flammability index and the comprehensive combustion index ar e significantly reduced.The apparent activation energy of the inhibited coal samples in the fou r stages of the oxidation process were increased.The optimum proportion of the composite inhibitor(sodium bicarbonate–tea polyphenols)was 3:1.The infrared spectra of the coal samples before and after inhibiting were fitted by in situ Fourier infrared spectroscopy experiments to quantify the changes of characteristic groups in the coal during oxidation.It is concluded that the composite inhibitors reduced the content of active groups(hydroxyl,methyl,and methylene)and intermediate products(carboxyl,carbonyl)in the coal,and increased the content of the more stable functional group ether bonds.In the process of coal low-temperature oxidation,sodium bicarbonate thermally decomposed to generate CO₂.Through the surface CO₂–O₂ competitive adsorption effect,physical inerting inhibited the spontaneous combustion of coal.During the high-temperature combustion of coal,the internal hydroxyl groups of tea polyphenols consumed active groups on the coal surface and formed ether bonds,which inhibited the progress of chemical reactions.The research in this paper provides new ideas for the development of fire-fighting technology with inhibitor,and has important theoretical guiding significance for further development of coal spontaneous combustion disaster prevention and control.