

@mastersthesis {6798,
	title = {Modeling of {Concentration} {Polarization} {Effects} and {Mineral} {Salt} {Scaling} in a {Reverse} {Osmosis} {Membrane} {Module}},
	year = {2011},
	note = {3472627},
	school = {University of California, Los Angeles},
	type = {phdPh.{D}.},
	address = {Ann Arbor},
	abstract = {Mineral scaling on membrane surfaces is an impediment to high recovery operation of reverse osmosis (RO) desalination. Mineral scaling is the result of mineral crystallization that occurs when the concentration of sparingly soluble salts, at the membrane surface, rises above their saturation concentration. The concentration field is governed by the combined fluid dynamics and mass transfer in the membrane channel. Accurate description of mineral scale formation is paramount for the development of scale monitoring and mitigation strategies. Accordingly, the present work focused on developing a quantitative finite-element modeling framework to elucidate the relationships among the mechanisms of mineral crystal nucleation and growth and detailed fluid flow and concentration fields in RO channels. The concentration field throughout a given RO channel, considering different channel geometries including the impact of channel spacers, was determined from the solution of the coupled mass transfer and fluid motion equations. This concentration polarization (CP) model included the effects of channel entrance and exit effects, as well as variability in the local permeate water flux due to osmotic pressure variations. Numerical model simulations revealed significant decrease in the rates of mass transfer near the channel walls and fluid outlet as well as in the proximity of channel spacers. Predicted zones of high solution saturation levels, at the membrane surface (with and without the presence of spacers), were corroborated by corresponding accumulation of mineral scale observed in membrane scaling experiments. Experimental analysis of direct observations of the nucleation and growth of mineral crystals of gypsum (selected as a model sealant), along with details of the concentration field (obtained from the CP model), enabled the development of a quantitative method for assessing the effectiveness of the modes of action (i.e., nucleation and growth retardation) of anti-scaling chemical additives. The CP model was coupled with data-driven models of crystal nucleation and growth kinetics to yield a mineral scaling model that enabled, for the first time, a priori predictions of the detailed local evolution of mineral scaling on the RO membrane and the associated permeate flow decline that closely matched experimental observations. The present modeling framework provides a detailed and quantitative approach, based on the fundamentals of fluid flow, mass transfer and crystallization kinetics, suitable for the design, optimization and operation of improved RO desalination processes.},
	keywords = {0542:Chemical engineering, Applied sciences, Chemical engineering, Concentration polarization, Desalination, Fluid dynamics, Gypsum scaling, Membranes, Mineral salts, Osmosis, Reverse osmosis, Studies},
	url = {http://search.proquest.com/docview/892720404?accountid=14270},
	author = {Lyster, Eric Michael}
}
