Construction of molecular structure model of bituminous coal and study on adsorption characteristics of C2H4 and C2H2

The abandoned coal in goaf will adsorb the gases ethylene (C₂H₄) and acetylene (C₂H₂) produced by coal oxidation, which makes the concentration data of the indicator gas inaccurate. Therefore, the adsorption law of coal and C₂H₄ and C₂H₂ gas is explored. The macromolecular structure model of coal was established and optimized by simulation, and the gas adsorption process was simulated by means of grand canonical Monte Carlo method. The adsorption quantities and adsorption sites of single component and binary component gases C₂H₄ and C₂H₂ in coal under different temperatures and pressures were analyzed. The results show that the molecular formula of S7 and W12 coal samples is C₁₃₆H₉₂O₃₀N₂S and C₁₂₉H₈₇O₂₈N₂S, respectively. When C₂H₄ and C₂H₂ are adsorbed at the same temperature, the adsorption pressure is positively correlated with the adsorption capacity, and the adsorption capacity increases rapidly with the increase of pressure, and then tends to be flat. With the same pressure, the adsorption capacity of C₂H₄ and C₂H₂ is unfavorable with the increase of temperature. The adsorption sites of C₂H₂ are more than those of C₂H₄. When C₂H₄ and C₂H₂ gas are used as indicator gases alone, they will be adsorbed by the left coal in the goaf, which makes the on-site monitoring gas concentration data inaccurate, resulting in the delay of the early warning time to a certain extent.