Gas Permeation Behaviors of Highly Permeable Thermally Rearranged (TR) Hollow Fiber Membranes in Flue Gas System

In gas separation processes using membranes, for example CO₂/N₂ or O₂/N₂separation, membrane performance itself as represented by permeability (or permeance) and selectivity is important in deposal capacity and quality of resultant gas (purity). Particularly, process optimization achieved by controlling operation variations such as feed flow rate, stage-cut, pressure ratio, operation temperature, etc. plays a critical role influencing separation factor and overall operation cost in mixed gas separation system. In addition, the understanding of gas transport mechanism in presence of water vapor is essential in a process where water cannot be removed before it is in contact with membranes.

In this study, we fabricated highly permeable thermally rearranged polybenzoxazole (TR-PBO) hollow fiber membranes and their modules to examine gas permeation performance in mixed gas system similar to real flue gas exhausted from post-combustion process. The optimal operation condition for CO₂ capture application was identified from simulation data. Additionally, we proposed a conceptual transport mechanism in TR-PBO hollow fiber membranes under humidified condition. Separation factor showed an increase with higher water vapor content without severe permeation flux drop. Moreover, the TR-PBO membrane modules under permeate vacuum condition showed improved gas separation performance with no permeation flux drop.