A Study on the Effect of Coal Metamorphism on the Adsorption Characteristics of a Binary Component System: CO₂ and N₂

At present, there is little research on the multicomponent gas adsorption characteristics of coal with different metamorphisms. In this study, DH (low metamorphism), FGZ (medium metamorphism), and DSC (high metamorphism) coal samples were selected as the microscopic research objects, and the molecular models of them were constructed by means of elemental analysis, ¹³C NMR, and X-ray. The adsorption characteristics of coal with different metamorphisms under the binary component system (CO₂ and N₂) were explored by experiments and simulations at 298 K and 1000 kPa. The results showed that in the binary component system gas environment, the adsorption strength of CO₂ is stronger than that of N₂. DH has the highest isosteric heat of adsorption, and the adsorption strengths of CO₂ and N₂ is stronger than that for FGZ and DSC. The adsorption amounts of CO₂ and N₂ by three coal molecules are ranked as DH > FGZ > DSC. The sequence of adsorption selectivity of CO₂/N₂ is DH > FGZ > DSC > 1, which demonstrates the stronger competitiveness of CO₂ than N₂. The adsorption selectivity of CO₂/N₂ for DH is stronger than that for DSC. However, with the increase of the CO₂ component, the adsorption selectivity of CO₂/N₂ for DH has a great influence, while DSC is relatively stable. The simulation results display a good agreement with the experimental results. The research can improve the accuracy and efficiency of inert injection measures and has guiding significance for the prevention and control of coal spontaneous combustion accidents by inert injection.