Molecular Dynamics Evaluation of Removal of Acid Gases from SNG by Ionic Liquid

A process for removing acid gas from synthetic natural gas based on ionic liquids (ILs) at room temperature is proposed. The structural properties, such as the radial and special distribution functions, and the dynamic properties, such as the self-diffusivity, are computed by molecular dynamics simulation methods. The microscopic characteristics are related to the macroscopic properties. The effects of different alkyl chain lengths and anionic ILs on the absorption process are studied. The ILs are proven to have good adsorption effects on acid gases, and the optimum IL, namely, [bmim][Tf2N], is determined. The structure–property relationships between the ILs and the dissolution diffusion are the basis for designing novel ILs. The design process is simulated by Aspen Plus. The results show that the process has good removal effects and that three key stream concentrations are increased compared with those based on a traditional solvent process. The capture rate of CO2 is 97.6%, the removal rate of H2S is 94.2%, and the CH4 concentration is 98.0%. The sensitivity analysis provides a decision-making basis for designers. Each index of product gas meets the requirements of GB 17820-2018, which enables these gases to be used in remote heating and power applications through the storage and transportation of the existing natural gas infrastructure.