The Inhibition Effect of CO 2 -N 2 Composite Gas on Spontaneous Combustion of Coal and the Law of Competitive Adsorption in Coal

The purpose of this study is to study the effect of CO2-N2 composite gas on coal spontaneous combustion index gas and the mechanism of inhibiting coal spontaneous combustion through a competitive adsorption process and to provide theoretical guidance for adopting inert injection fire prevention and control technology in goaf to prevent coal spontaneous combustion. The programmed temperature experiment and gas chromatography were used to analyze the indicator gas after injecting different mixed ratios of CO2 and N2 inert gas. In the whole oxidation heating process (25–300 ℃), the generation of indicator gas and the peak point of gas ratio showed an apparent “Hysteresis phenomenon” and the more significant the proportion of CO2 in the composite inert gas, the more pronounced the “Hysteresis phenomenon.” Even in the CO2-dry air environment, the peak point disappears, indicating that with the injection of N2 and CO2, the coal body is in a more complex gas atmosphere, and a variety of gases are in the process of adsorption and desorption on the inner and outer surfaces of the coal body. The characteristics of the evolution of the spontaneous combustion oxidation process of coal are more complex, directly affecting the coal-oxygen interaction, thus affecting the intuitive combustion oxidation process. Molecular simulation studies the characteristics of coal molecules on CO2, N2, and O2. The results show that the adsorption capacity and adsorption energy of coal molecules on CO2 molecules are more significant than O2 and N2, and there is a competitive adsorption relationship between CO2 and N2 molecules and O2 molecules, and the competitive adsorption capacity of CO2 is more significant than N2. It shows that the composite inert gas can inhibit the coal-oxygen adsorption by competitive adsorption to displace oxygen and achieve the combustion inhibition effect. The experimental and theoretical basis for developing and improving inert gas fire extinguishing technology is provided by studying the index gas after CO2-N2 composite inert gas action and the adsorption capacity and energy in the competitive adsorption process.