Impact of concentration polarization on the performance of membrane gas separation processes: application to biogas upgrading

Through the illustrative application of biogas treatment, this paper investigates the impact of concentration polarization on the separation performance of emerging inorganic membranes in membrane gas separation processes. The results show that polarization may significantly reduce the biogas purification rate, although its effects on methane recovery remain moderate. Contrary to previous assumptions, the impact of polarization does not monotonously increase with increasing permeance to CO₂ and selectivity. Material selectivity is shown to not significantly influence the polarization intensity, and the CO₂ permeance at which peak polarization conditions occur is not constant but varies depending on the operating and geometric conditions considered. The impact of polarization impact intensifies with increasing fiber diameter and operating pressure, preventing taking full advantage of the exceptional permeances of inorganic membranes, and therefore, constitutes a major obstacle to their use as an alternative to conventional polymeric fibers.