Molecular Simulation Study Of The Structure Of Shendong Inertinite And The Interaction Of CH₄, CO₂ And H₂O

The study of adsorption of coalbed methane by energy efficiency is a hot spots, but most experimental methods are traditional ideas, and they are difficult to recognize the adsorption mechanism of gases on coal from microscopic scale. In this paper, experimental methods were combined with models to build macromolecular structure model of Shendong inertinite (SI), and analyse the adsotption of the CH4,CO2,and H2O, then the adsorption mechanism in molecular level could be known. The following results were obtained:1.The spatial crossing macromolecular structure model of SI was obtained after the optimization of the plain model by Molecular Mechanics and Molecular Dynamic, which based on the structure parameters from the analysis of the experiment of 13C NMR. And the consistence of simulated IR spectrum and density (1.14 g/cm3) with the experimental results showed that SI was reasonable. 2.The simulation of saturated adsorption of pure CH4, CO2, H2O on SI by Grand Canonical Monte Carlo (GCMC), the following results were obtained:1) In the same condition,the size order of saturated adsorption was: H2O> CO2> CH4.2) Through the simulation of saturated adsorption of pure CH4, CO2, H2O on SI, it is found that adsorbate molecules were first adsorbed on the edge of SI molecules, and after that in the pores.Adsorbate molecules were both sides of the molecular chain in the SI, and some of the local concentration of adsorbate molecules, such as the adsorption of methane, and the spatial arrangement was similar to the ethane; carbon dioxide molecule was arranged in Cross-form.3.Through the simulation of adsorption of pure CH4, CO2, H2O on SI applying the molecular dynamics when the tempreture is 298.15 K and the pressure is 0.001 GPa, the following results were obtained:1) The size order of simulated adsorption isotherm for pure CH4, CO2 and H2O in the same tempreture and fugacity was: CH4 CO2> CH4.2) The tempreture and the adsorption was linear negative in the same fugacity, and it was difficult that the adsorption of CH4, CO2 and H2O on coal in the high-temperature region.3) A threshold about 8 MPa was appeared while the single-component CO2, CH4 and H2O adsorption when the pressure was less than 8 MPa, as the pressure increases, the single-component adsorption was increased, but when the pressure was greater than 8 MPa, with pressure increasing, the adsorption was decrease moreover, at the same temperature and pressure conditions, the impact on H2O adsorption by pressure was greater than CO2 and CH4 .4) Through the analysis of isosteric heat ,the adsorption of pure CH4, CO2 and H2O on SI was physical adsorption5.Through the simulation of the adsorption isotherm of binary CH4/CO2, CH4/H2O and CO2/ H2O on SI, the following results were obtained:1) The size order of advantage of sorbates in competitive adsorption was: H2O> CO2> CH4.2) In the same tempreture and fugacity ,The size order of advantage of sorbates in competitive adsorption was: CH4