Date of Award

Spring 1988

Document Type

Thesis

Degree Name

Master of Science in Engineering Science- (M.S.)

Department

Chemical Engineering, Chemistry and Environmental Science

First Advisor

Piero M. Armenante

Second Advisor

Henry Shaw

Third Advisor

Dana E. Knox

Abstract

An investigation on the minimum agitation speed required to achieve complete dispersion in liquid-liquid systems has been carried out. A model based on the momentum balance for a droplet and on Kolmogoroff's theory of isotropic turbulence was used for the prediction of the role of the most important variables on the minimum agitation speed. The equation so derived can be expressed in terms of a number of non- dimensional groups (such as Re, Ar, and Su). For geometrically similar systems the equation contains only one adjustable parameter ( to be determined experimentally) in the form of the proportionality constant correlating Re with the other non-dimensional groups. The equation was tested against the experimental results previously reported in the literature by several investigators. The agreement between predicted and experimental values appears to be good. In addition, only one numerical value of the correlating parameter is required to explain all the different experimental results which were reported in previous investigations, and tested here. The overall correlation coefficient is equal to 0.98. Even better agreement is found if single sets of consistent data are considered. Experiments were also conducted to further test the validity of the equation, using five different impellers, four tank sizes, and three impeller sizes. In addition, the effect of impeller clearance off the dispersed phase, liquid height, phase volume ratio, and fluid properties were also investigated. These results were correlated using regression methods, but this introduced a second constant in the equation. A novel method to determine the minimum agitation speed for dispersing an organic phase in water was also used. A comparison between our data and the model appears favorable and is also provided.

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