Membrane gas separation processes have been developed for diverse gas separation applications that include nitrogen production from air and CO₂ capture from point sources. Membrane process design requires the development of stable and robust mathematical models that can accurately quantify the performance of the membrane modules used in the process. The literature related to modeling membrane gas separation modules and model use in membrane gas separation process simulators is reviewed in this paper. A membrane-module-modeling checklist is proposed to guide modeling efforts for the research and development of new gas separation membranes.

High-fidelity simulations of momentum and mass transfer within a hollow fiber gas separation membrane module are here reported. The simulations capture the potential detrimental effects of poor fiber packing at the bundle–case interface on fluid distribution and performance. Results are presented for both circular and planar fiber bundles. The length over which bundle–case gaps affects flow is determined. The length increases dramatically with increasing fiber packing fraction. As the packing fraction approaches 0.6, the impact extends over the entire bundle diameter for small modules (<1000 fibers). The results clearly demonstrate the detrimental effect of poor packing along the case and can be used to develop module manufacturing guidelines. To reduce computational costs, an equivalent planar bundle module approximation is developed. The approximate simulations agree well with results from full 3-D simulations and can reduce computational costs without sacrificing fidelity.

Numerous surface modification strategies have been developed to improve the fouling resistance of filtration membranes. A novel approach in which a temperature sensitive polymer gel is deposited on the surface is reported. The gel switches from an expanded, lower permeability, fouling-resistant hydrophilic state to a collapsed, higher permeability, fouling-prone hydrophobic state as the temperature is increased. By alternating between these two states, it is hypothesized that fouling can be reduced while minimizing the permeability reduction due to the surface modification. The hypothesis was tested by depositing a hydroxypropyl cellulose (HPC) gel on the surface of the cellulose acetate ultrafiltration membranes (Osmonics SN32) using divinyl sulfone (DVS) as a crosslinker. Unmodified and modified membranes were used to filter yeast and the HPC suspensions. To induce the hydrophobic-hydrophilic transition, the feed was switched alternately between room temperature and 60°C solutions. The experimental results support the hypothesis. Unmodified membranes fouled severely when operated at room temperature, 60°C, or oscillating between the two temperatures. The modified membranes fouled severely at 60°C but little fouling occurred at room temperature or with temperature oscillation. The results suggest that permanent surface modification is not required to reduce the fouling rates. Transient fluctuations in the surface chemistry and the structure are equally effective. Moreover, one can achieve higher filtration rates in transient operation because pores possess a larger effective diameter/higher permeability in the collapsed state than the expanded state.