Molecular simulation of supercritical CO2 extracting organic matter from coal based on the technology of CO2-ECBM

Abstract

Supercritical CO2 (ScCO2) can affect the adsorption of coalbed methane (CBM) by changing the pore structure. In order to explore the mechanism of ScCO2 extracting organic matter from coal at the micro scale, molecular simulation was used to study it. During the simulation, the temperature and the pressure were set 307.65 K and above 7.5 MPa, respectively, and the organic matter molecules were selected in the Wiser model. According to the analysis of simulation results: The greater the difference between the solubility parameters of ScCO2 and coal organic molecules, the worse their blending, and the more difficult it is for ScCO2 to extract organic small molecules from coal. Pressurization promotes the irregular movement of particles in the equilibrium blend system, and makes the properties inside the system gradually tend to be uniform. Therefore, Pressurization facilitates the stability of the thermodynamic properties of the blend system and increases the possibility of ScCO2 extracting coal organic matter. The synergistic effect of high pressure and the number of organic molecules is beneficial to the extraction of organic matter from coal by ScCO2, and the blend system with the extract is stable in thermodynamic properties. This study provides a theoretical basis for the application of CO2-ECBM.