Shell and lumen side flow and pressure communication during permeation and filtration in a multibore polymer membrane module

Abstract

This study reveals the importance of the module geometry on the flow field and pressure distribution during membrane permeation for multibore membranes. The pathways of permeation are unraveled within a custom-made single multibore membrane module. For this, we combine flow velocimetry of magnetic resonance imaging (MRI) with computational fluid dynamic (CFD) simulations and permeation experiments. First, a systematic simulation study identifies flow patterns based on simplified geometry features that are supported experimentally through flow-MRI measurements. This comprehensive study shows how small geometric deviations from the idealistic assumptions result in unexpected fluid flow on the shell and lumen side in the module. Second, the influence of those non-ideal flow patterns during the filtration of silica particles are revealed by MRI. The results indicate heterogeneous silica deposition due to geometry induced flow fields. Contrary to the idealized assumption, the subsequent backwashing is also influenced by those deposition patterns. Hence, unavoidable non-idealities of membrane positioning during the construction of the module influence the performance of the membrane filtration. With this study, we stimulate to analyze and pioneer new strategies to fully recover the membrane's performance after filtration cycles during backwashing based on a precisely designed backwash optimized permeate channel geometry in membrane modules.

In-situ investigation of wetting patterns in polymeric multibore membranes via magnetic resonance imaging

“…Measurements in the tomograph are carried out in the x-y-plane, being the cross-section of the membrane module. All images are obtained using a 2D spin-echo pulse sequence adapted from our previous studies [16,26,43]…”

“…Hence, flow patterns inside the membrane change, which causes unfavorable pathways limiting the liquid mass transport by increased pressure drop. [16] 3. Materials and methods…”

“…Single fiber wetting. and modules towards small pressure disturbances [16,17]. Pressure disturbances increase with non-uniformity in flow which can be induced by changing packing density [44][45][46].…”

“…Those improved tensile properties allow multibore membranes for industrial-scale applications in drinking water production and seawater desalination [1,4,5], as well as wastewater and surface water filtration [2,[6][7][8]. Multibore membranes have been subject to many studies regarding optimized geometry [2,4,7,9,10], membrane material [11][12][13], and experimental flow distribution [14][15][16][17][18], as well as flow distribution via computational fluid dynamics (CFD) [16,19,20]. Especially the flow distribution across a multibore membrane has been proven to be very sensitive to nonidealities such as bending, skin damages, or excentric positioning.…”

“…Especially the flow distribution across a multibore membrane has been proven to be very sensitive to nonidealities such as bending, skin damages, or excentric positioning. In turn, this altered flow distribution causes distinct changes in flow patterns across the whole module [16,17].…”