چكيده به لاتين
Abstract:
In recent years, valuable information on polarization layer formation and flux decrease during time has been obtained from membrane process modeling studies. Oil in water emulsion separation by membrane process has been one important research topic due to wide spread problem of water pollution by oil especially in oil field areas. In this thesis, capability of computational fluid dynamics (CFD) in gathering required information was applied to develop a microscopic model for investigating oil droplet behavior immersed in water on a membrane surface. Then experimental design tools were used to investigate the effect of different operational and physical variables on critical permeation pressure as an indicator of droplet behavior. Critical permeation pressure was reported according to statistical analysis by a second order polynomial which deviates -7% with CFD prediction under optimum operational and physical conditions. Then, in order to decrease membrane fouling by oil droplet, dielectrophoresis (DEP) force capability in oil droplet repulsion from membrane surface was applied. DEP effect on process performance improvement was confirmed theoretically by microscopic electrofiltration model development. After model validation by available experimental information in the literature, comprehensive study of critical voltage as a representative of droplet behavior in presence of DEP was started. Analysis of variance on the experimental design outcome, resulted in a second order polynomial for square root of critical voltage which deviates about -4% from CFD prediction at optimum conditions. In order to assess DEP effect in real experimental system, an experimental setup with a module suitable for electrofiltration was designed and fabricated. This experimental setup proved DEP effect on process performance improvement and flux increase under constant operational condition and different values of applied voltage. By considering operational pressure, cross flow velocity, oil concentration and applied voltage as system variables, flux and rejection were studied as response functions. After appropriate experimental design and analysis of variance, functionality of each response function from variables were obtained which showed 3.4% and 6% deviations under steady conditions respectively.
Keywords: Oil in Water Microfiltration, Electrofiltration, Dilecetrophoresis, Critical Permeation Presuure, Critical Detachment Voltage, Single Droplet Modeling, Computational Fluid Dynamics, Experimental Design
