Dispersion in stirred vessels

Abstract

The three-dimensional problem of drop breakage in stirred vessels can be successfully reduced to a single dimensional framework using Voigt element, retaining the essential features of the breakage process Recent models successfully employ it to predict the maximum stable drop diameter, dm=, for aet on- rheologically complex dispersed phases, but also when surfactants or drag-reducing agents are present 10 the continuous phase.

The effect of the dispersed phase hold up on dmax shows trends contrary to expectation This can be explained only by invoking two new mechanisms of drop breakage, each giving its own dmax. The observed dmax therefore is the minimum of the three dmax values gjven by the three mechanisms.

A multistaged model, developed recently, explains the reducing influence of the dispersed phase viscosity, J-Ld, at hIgh I-Ld values It also explains how the interfacial tension continues to influence dmax under these extreme conditions.

A new model for breakage frequency based on unequal breakage and eddy Size distribution existing in the vessel is able to predict not only the breakage frequency, but also the daughter droplet size distribution.