Temperature modulated membrane transport phenomena
Aachen (2019, 2020) [Dissertation / PhD Thesis]
Page(s): 1 Online-Ressource (xiv,192 Seiten) : Illustrationen, Diagramme
Temperature strongly affects the transport phenomena that govern membrane separation. It impacts the hydrodynamics near the membrane surface, the interaction forces between solutes, surfaces and solvents, and the microporous structure of the membrane itself. The large number of properties affected by temperature offers a vast playground to use temperature to enhance separation performances. Direct heating of membranes enables a local temperature change and control of the heat input. This thesis elucidates how direct membrane heating can positively influence membrane transport phenomena and presents novel applications that arise from the direct heat input. A synthesis approach to fabricate electrically conductive porous hollow fiber membranes made of silicon carbide is presented. The inorganic membranes can be heated by Joule heating. The applied electric power enables to control the temperature of the membrane. The synthesized fibers are used to induce thermally driven convection in the membrane module that is superposed with the forced convection of the membrane permeation. The resulting mixed convection flow patterns improve the shear rate and the shear stress at the membrane surface and reduce the concentration boundary layer. The thesis further assesses the influence of temperature on colloidal interactions in a particle-laden flow through a membrane pore. The temperature dependency of van der Waals, electrostatic double layer, and Lewis acid-base forces are studied for each interaction individually. The combined interaction potential is used to numerically demonstrate that temperature can both, enhance and lower particle deposition depending on the applied material system. The heatable silicon carbide fibers are tested in three promising applications: As a fouling prevention tool in aqueous microfiltration, as responsive membranes modified with thermo-responsive polymers, and in an electrical swing adsorption process for CO2 capture. The three applications show the broad application potential of direct membrane heating for enhanced performances. Furthermore, the knowledge gained within this thesis is not restricted to Joule heating or porous ceramic membranes but transferable to other heating concepts and membranes.
Rösener, Theresa Birgitta Maria
Benes, Nieck E.