Investigation of Competitive Adsorption Properties of CO/CO₂/O₂ onto the Kailuan Coals by Molecular Simulation

To reveal the CO, CO₂, and O₂ adsorption properties of two bituminous coals at different pressures and temperatures, the molecular unit-cell structures of two types of bituminous coal are constructed (C₁₁₈₀H₉₆₀O₁₂₀N₂₀ and C₁₁₆₀H₈₆₀O₈₀N₂₀) by Fourier transform infrared (FTIR) spectroscopy. The bituminous coal molecular FTIR spectroscopic curve is calculated by quantum chemistry, and the results are consistent with the experimental curve. The isothermal adsorption curves of the single-component gases CO, CO₂, and O₂ conform to the Langmuir equation from 20 to 60 °C. The adsorption simulations are mainly performed using grand canonical Monte Carlo (GCMC) methods. The amount of adsorption decreases with increasing temperature at the same pressure, and CO₂ can be the first to reach adsorption saturation at the same temperature. The CO₂/CO adsorption selectivity for binary gas mixtures has apparent advantages in low-pressure or shallow buried coal seams. The adsorption selectivity of O₂/CO varying under different pressures is not obvious. The high amount of CO inhibits the adsorption capacity of CO₂ and O₂. In other words, the effect of injecting CO₂ to control fire extinguishing in bituminous coal seams with high abnormal CO concentrations is not significant.