Mathematical Modeling of Gas Separation in Flat-sheet Membrane Contactors

Gas-liquid membrane contactors offer several practical advantages including high surface area per unit volume; independent control of gas and liquid velocities without any flooding, loading, weeping, or foaming, pre-determined gas–liquid interfacial area, membrane modules, capability of linear scale-up; low corrosion problems, and low operation and capital costs. Two common types of membrane contactors are extensively utilized for gas separation. However, most studies have focused on the hollow-fiber membrane contactors. The main advantage of flat-sheet membrane contactors is that not only any type of membrane can be formed into flat-sheet membrane module but also fabrication of flat-sheet membranes is also easier compared to other types of membranes. A mass transfer model was developed in this study to investigate the performance of flatsheet membrane contactors for gas absorption. The model was based on the behavior of gas and liquid phases in the membrane contactor by taking the distribution of gas concentration as well as the gas and liquid velocity profiles along the flowing direction into account. Both chemical and physical absorptions were considered. The model also uses computational fluid dynamics of mass and momentum transfer in both gas and liquid phases in the membrane contactor. An appropriate numerical method based on the finite element method was applied to solve the model equations. The model predictions were validated against the experimental data obtained from literature for the absorption of CO 2 . The results were in good agreement with the experimental data with different values of flow rates. The model predictions indicated that the removal of CO 2 was increased with increasing the liquid velocity in the membrane contactor. On the other hand, increasing temperature and gas velocity in the flat-sheet membrane contactor showed an opposite effect on the removal of CO 2 . It is indicated that the proposed model well predicts the mass transfer within the flat-sheet membrane contactors.