Numerical simulation of CO2 condensation process from CH4-CO2 binary gas mixture in supersonic nozzles

Supersonic separation technology is a technique potentially applicable in separating CO2 from natural gas. An Euler-Euler two-fluid model is developed to predict the spontaneous condensation process of CO2 in CH4-CO2 binary gas system during supersonic expansion using the nucleation theory and droplet growth model. The proposed model is validated by the experimental data obtained from literature and the effects of inlet temperature, pressure and gas composition on the condensation process are analyzed. The simulation results show that the homogeneous nucleation of CO2 occurs intensively within a short period in the diverging part of the nozzle and the mass fraction of condensed phase increases continuously until the nozzle outlet. The onset of the condensation occurs earlier and more CO2 can be condensed out of the gas mixture at lower inlet temperature, higher inlet pressure and bigger CO2 feed concentration.