Study on the mechanism of temperature-responsive composite inhibitors in suppressing coal spontaneous combustion at different reaction stages

Temperature is one of the main causes of spontaneous coal combustion. To improve the flame retardant performance, CaCl 2 , ammonium polyphosphate (APP), and calcium phosphate (CaHP) were compounded to control the temperature response of different stages of coal spontaneous combustion through physical and chemical synergy. Simultaneous thermal analysis, thermogravimetric-Fourier infrared spectroscopy (TG-FTIR), in-situ FTIR and electron paramagnetic resonance (EPR) were used to study the multi-temperature stage synergistic inhibition of coal spontaneous combustion. The results show that the proposed method is effective. By obtaining the characteristics of the spontaneous combustion reaction stage of coal in advance, the method of configuring an appropriate composite inhibitor can effectively realize the intelligent control of the temperature response of coal spontaneous combustion. The ignition point of long-flame coal increased by 37.15 °C. The inhibition rate of the gas phase products was more than 20%, and the inhibition rate of the functional groups was more than 30%. It has a good quenching effect on free radicals and can effectively inhibit the oxidation activity of active free radicals such as ·H, ·HO, and ·O. The results provide experimental and theoretical support for the study of temperature-responsive composite flame retardants for coal with different metamorphic degrees.