Gas/liquid two-phase flow with perforated hollow filament spacer to enhance the filtration performance in spiral wound membrane module

Abstract

In brackish water and seawater desalination process, flat sheet and spiral wound membrane modules are commonly used to remove particulate pollutants and/or inorganic ions. In these membrane modules, feed spacer is used to construct the flow channel, enhance the flow field and corresponding filtration performance. However, two negative effects also occur for the spacer. One is the high pressure drop due to flow around the filament. The other is the stagnant zone near the filament, which results in localized fouling. In this paper, a new perforated hollow filament spacer was proposed. Gas/liquid two-phase flow was used to mitigate the membrane fouling. Filtration experiments were performed by microfiltration of SiC suspension. Results showed that compared with conventional spacer, the hollow filament spacer can improve the steady permeate flux by 56 %, with lower pressure drop. Particle deposition on membrane surface was effectively retarded, without localized fouling observed. Gas/liquid Flow patterns in the membrane channel were studied with high-speed photography. With the increase of Gas/liquid ratio, the flow pattern changes from bubble flow, slug flow to churn flow. The best filtration improvement performance was obtained with slug flow pattern. This hollow filament spacer is expected to mitigate the membrane fouling and improve permeate flux in the membrane-based desalination process.