Performance evaluation of water vapor permeation through perfluorosulfonic acid capillary membranes

Abstract

Abstract Perfluorosulfonic acid membranes perform water vapor permeation at a high level. Few studies, however, have described the water vapor permeance of dehumidification membranes. In this study, therefore, perfluorosulfonic acid capillary membranes used in commercial membrane dehumidifiers were examined to clarify the measurement conditions that are used to evaluate water vapor permeation performance. The measurement conditions include an operating temperature of 10 – 40 °C, a feed gas relative humidity (RH) of 0 – 90%, and a total feed side pressure of 0.2 MPaG. Water vapor permeation was evaluated by measuring slight changes in the RH of sweep gas on the permeate sides using countercurrent modules with an effective membrane length of 80 mm. Regarding the RH of the feed gas, the difference between feed-in and sweep-in RH was set to 20% or less to minimize the water vapor pressure difference across the membranes. The water vapor flux was higher under high operating temperatures and high levels of feed gas RH. On the other hand, the water vapor permeance increased with increasing feed gas RH but decreased with increasing operating temperature. Under conditions of 10 °C and feed-in RH of 90%, a high water vapor permeance of 1.6 × 10−5 mol / (m2 s Pa) was obtained. To verify the dependence of water vapor permeation performance on the feed gas species used, measurements were carried out using air, N2, He, and CO2 as the feed gases. The water vapor permeation performance showed no dependence on feed gases of air, N2, or He, but permeation was decreased when CO2 gas was used.