Modeling concentration polarization and permeate flux in water and gas membrane separation processes /
Kathleen, Foo,
Modeling concentration polarization and permeate flux in water and gas membrane separation processes / Foo Kathleen - xvi, 181 pages : illustration ; 1 CD-ROM
Faculty of Chemical and Process Engineering Technology
Thesis (Doctor of Philosophy) -- Universiti Malaysia Pahang – 2024
Includes bibliographical references
Concentration polarization (CP) is an inherent problem in membrane operation and is prone to cause fouling, whether in water or gas membrane separation processes. This phenomenon can decrease the efficiency of membrane separations, especially for advanced high-permeability membranes. Hence, the primary aim of the study is to simulate and discuss CP phenomena and the mechanisms of CP reduction to enhance mass transfer and permeate flux performance in water (i.e., reverse osmosis desalination) and gas membrane separation processes. Recent studies found that introducing an external shear force through a forced slip velocity can minimize CP and enhance flux performance in water desalination process, typically for a spiral wound membrane (SWM) module that is widely used in commercial operations. However, the previous studies are limited to a single geometry of spacer filament, one of the fundamental components responsible for separating membrane sheets to create flow passage while minimizing fouling in SWM modules. Hence, the first objective of the study is to investigate the effect of spacer design in terms of geometry profiles (circular and elliptical) and configurations (2- and 3-layer spacers) on CP reduction and flux enhancement in membrane desalination driven by unsteady forced-slip using computational fluid dynamics (CFD). Results demonstrate that employing a forced-slip with a submerged circular spacer leads to the highest flux increase (up to 40%) compared to other geometries, suggesting a preference for the simple circular profile of spacers to maximize vortex-shedding-induced flux enhancement in water desalination process using SWM modules. Recent studies also highlighted the potential of using membrane-based method as a less intensive approach for desalination of hypersaline brine. Nevertheless, there is limited discussion concerning the performance of SWM in terms of flux and energy consumption for desalination of the high-salinity water using conventional reverse osmosis module. Hence, a multi-scale analysis is conducted to evaluate and compare the performance of reverse osmosis module between seawater and hypersaline brine at various operating conditions. Results indicate that an inlet pressure of at least 75 bar is recommended to minimize energy consumption for hypersaline brine desalination, with significant energy reduction influenced by high pressure recovery and pump efficiencies. While film theory (FT) has been developed to describe CP in membrane systems, no study to date has discussed the accuracy and limitation of the film theory model for predicting CP in membrane gas separation. Therefore, an analysis is performed comparing the film theory against a more rigorous numerical solution via CFD. The results show that the analytical solution proves reliability in membrane gas applications characterized by low CP under high crossflow and low flux conditions. Furthermore, an analysis of the impact of gas mixing by coupling spacers into membrane gas separation channel reveals that the effectiveness of spacer-flux-to-pressure-loss-ratio (SPFP) reaches a peak owing to the trade-off between flux and pressure drop at 5
THE0009951 (Local)
Faculty of Chemical and Process Engineering Technology--Dissertations
Universities and colleges--Dissertations
Theses--Dissertations
Modeling concentration polarization and permeate flux in water and gas membrane separation processes / Foo Kathleen - xvi, 181 pages : illustration ; 1 CD-ROM
Faculty of Chemical and Process Engineering Technology
Thesis (Doctor of Philosophy) -- Universiti Malaysia Pahang – 2024
Includes bibliographical references
Concentration polarization (CP) is an inherent problem in membrane operation and is prone to cause fouling, whether in water or gas membrane separation processes. This phenomenon can decrease the efficiency of membrane separations, especially for advanced high-permeability membranes. Hence, the primary aim of the study is to simulate and discuss CP phenomena and the mechanisms of CP reduction to enhance mass transfer and permeate flux performance in water (i.e., reverse osmosis desalination) and gas membrane separation processes. Recent studies found that introducing an external shear force through a forced slip velocity can minimize CP and enhance flux performance in water desalination process, typically for a spiral wound membrane (SWM) module that is widely used in commercial operations. However, the previous studies are limited to a single geometry of spacer filament, one of the fundamental components responsible for separating membrane sheets to create flow passage while minimizing fouling in SWM modules. Hence, the first objective of the study is to investigate the effect of spacer design in terms of geometry profiles (circular and elliptical) and configurations (2- and 3-layer spacers) on CP reduction and flux enhancement in membrane desalination driven by unsteady forced-slip using computational fluid dynamics (CFD). Results demonstrate that employing a forced-slip with a submerged circular spacer leads to the highest flux increase (up to 40%) compared to other geometries, suggesting a preference for the simple circular profile of spacers to maximize vortex-shedding-induced flux enhancement in water desalination process using SWM modules. Recent studies also highlighted the potential of using membrane-based method as a less intensive approach for desalination of hypersaline brine. Nevertheless, there is limited discussion concerning the performance of SWM in terms of flux and energy consumption for desalination of the high-salinity water using conventional reverse osmosis module. Hence, a multi-scale analysis is conducted to evaluate and compare the performance of reverse osmosis module between seawater and hypersaline brine at various operating conditions. Results indicate that an inlet pressure of at least 75 bar is recommended to minimize energy consumption for hypersaline brine desalination, with significant energy reduction influenced by high pressure recovery and pump efficiencies. While film theory (FT) has been developed to describe CP in membrane systems, no study to date has discussed the accuracy and limitation of the film theory model for predicting CP in membrane gas separation. Therefore, an analysis is performed comparing the film theory against a more rigorous numerical solution via CFD. The results show that the analytical solution proves reliability in membrane gas applications characterized by low CP under high crossflow and low flux conditions. Furthermore, an analysis of the impact of gas mixing by coupling spacers into membrane gas separation channel reveals that the effectiveness of spacer-flux-to-pressure-loss-ratio (SPFP) reaches a peak owing to the trade-off between flux and pressure drop at 5
THE0009951 (Local)
Faculty of Chemical and Process Engineering Technology--Dissertations
Universities and colleges--Dissertations
Theses--Dissertations