Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2010. / Full text also available online. Scroll down for electronic link.

Thesis (M.S.)--University of Missouri-Columbia, 2004. / Typescript. Includes bibliographical references. Also available on the Internet.

Backmixing of the continuous phase was studied in liquid-liquid spray columns of various geometries, for various flowrates of the two phases, and for various drop size distributions. The dispersion or eddy diffusion model was used to characterize the axial mixing of the continuous phase. Axial concentration profiles were measured upstream, with respect to the continuous phase, from a distributor of sodium chloride tracer (soluble in the continuous phase only). The steady state form of the model was utilized to calculate axial eddy diffusivities from these results. The tracer studies showed that the axial eddy diffusivity is independent of the continuous phase flowrate and the column height. Axial eddy diffusivities between 7-ft.²/hr. and 31-ft.²/hr. were obtained in a 1½-in. I. D. column. Low dispersed phase flowrates and large drop sizes resulted in high axial eddy diffusivities. Increasing the column diameter to 3-in. resulted in superficial axial eddy diffusivities between 6.3 and 17.3 times larger. The hold-up of dispersed phase was measured by means of a piston sampler. The hold-up increases approximately linearly with increasing dispersed phase superficial velocity and tends to be slightly higher for increased continuous phase superficial velocities. A smaller drop size resulted in an increased hold-up. Drop size distributions were measured. They always show two peaks, one at 0.02-in. diameter, and the other at a much larger size, the actual value of which depends on the nozzle tip diameter used to disperse the drops. The mixing cell-packed bed analogy was used to predict Peclet numbers in a spray column. The agreement between these and measured Peclet numbers is good for drops of about 0.15-in. equivalent diameter but becomes progressively worse as the drop size is reduced. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

An experimental investigation was undertaken to study the factors affecting phase separation in a specially constructed, laboratory scale mixer-settler. Two phase systems were used: 1. A laboratory prepared HSLIX64N-copper phase system, similar to that used in commercial copper solvent extraction processes. 2. A phase system obtained directly from the uranium extraction circuit of the Key Lake Mining Corporation, Sask., millsite. A settler scale-up criterion relating dispersion band thickness to specific settler flow of dispersed phase, was found to have considerable merit. Besides being dependent on specific settler flow, the dispersion band thickness was found to be a function of the phase ratio (for system 2 only), dispersion introduction level (for system 2 only), and temperature. Mixing intensity had no appreciable effect with either system. Microscopic examination of the dispersion produced with system 2 revealed the existence of double dispersions; that is, drops within drops. A photomicroscopic technique was used to undertake a drop size investigation of the dispersion produced with system 2. Drop size was found to be independent of dispersion throughput, a weak function of impellor speed and a relatively strong function of the phase ratio. With the exception of organic continuous operation with system 1, it was possible, based on the holdup and drop size profile within the dispersion band, to distinguish two horizontal sublayers within the dispersion band. In the "even concentration sublayer", comprising the majority of the dispersion band, the holdup and average drop size is nearly constant throughout. In the "dense concentration sublayer", both the holdup and the average drop size increase sharply as the coalescence front is approached. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

No description available.

No description available.

No description available.

No description available.

No description available.

No description available.