Prediction of the CH4-CO2 mixture properties using SAFT-VR Mie equation of state and molecular dynamics simulations

M Sharifipour and A Nakhaee, MOLECULAR PHYSICS, 122 (2024).

DOI: 10.1080/00268976.2024.2313036

This paper conducts a computational investigation of the phase behaviour of CH4-CO2 binary system, utilising the SAFT-VR Mie equation of state alongside molecular dynamics (MD) simulations. Molecular parameters for pure CH4 and CO2 compounds were obtained by fitting the SAFT-VR Mie EOS to vapour pressure and saturated liquid density experimental data. The research first validates the SAFT-VR Mie EOS on thermodynamic properties and vapour-liquid equilibria for different compositions, pressures, and temperatures of pure CH4, CO2, and CH4-CO(2 )mixtures with the newly extracted parameters. The study confirms the EOS's accurate prediction of coexistence properties, including pressure, density, and phase- equilibrium curve. MD simulations were performed using the LAMMPS software package, with Mie force field parameters derived from this study for non-bonded interactions. Simulations were conducted using three other force fields (OPLS-UA, UFF, and GAFF) to compare their performance with our approach. The simulation results were compared to laboratory data, or REFPROP, in the absence of laboratory data. The results showed a relatively good agreement, indicating that combining SAFT-VR Mie EOS and MD simulations is a reliable predictive tool for designing gas processing and gas storage applications involving CH4-CO2 mixtures. This approach also mitigates the need for expensive and hazardous high-pressure laboratory techniques. GRAPHICS

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