Recovery of dissolved methane through a flat sheet module with PDMS, PP, and PVDF membranes

Abstract

A degassing contactor using a flat sheet membrane module (FM) was operated in sweep gas mode to study the performance of several commercial polymer membranes, both dense (polydimethylsiloxane, PDMS) and microporous (polypropylene, PP, and polyvinylidenefluoride, PVDF), for the recovery of dissolved methane from water. Non-steady state experiments were conducted at different liquid (QL, 3.5–40.5 L h−1) and gas flow rates (QN2, 0.05–15.00 L h−1). In the case of PDMS, PP, and when PVDF was operated at moderate high QL (≥21 L h−1), similar methane removal efficiencies (RE) were obtained. In the case of PVDF operated at relatively low QL (3.5 L h−1), a lower RE was observed. A model for the mass transfer of methane has been selected that is adequate in predicting the experimental results. These results concluded that the mass transfer resistance was mainly located in the liquid phase. Microscopy and especially contact angle measurements were used to monitor the structural and surface stability on the membranes. The membranes were altered during the operation, especially for QL ≥ 21 L h−1, showing a decrease (PDMS and PP) or an increase (PVDF) in hydrophobicity and even cleavages (PDMS). The combination of the FM and contact angle technique has demonstrated to be very versatile and useful for monitoring the variation of the membrane properties during operation.