Drop sizes in an agitated liquid‐liquid system

The relationship between drop size and location in an agitated liquid‐liquid system was investigated, with a new sampling method in which the dispersion was sampled in a specially designed trap and immediately encapsulated by a polymer film. The liquid‐liquid system used was water and a mixture of isooctane and carbon tetrachloride with a density closed to that of the water. Dispersed phase holdup was varied from 0.025 to 0.34 volume fraction. For this system, which has low mutual sulubility and high interfacial tension, there is almost no dependence of drop size on location for the mixing geometries studied. This was due to the fact that the coalescence rate is low compared to the circulation time. An increase in impeller speed and drop size decreased the coalescence rate while an increase in holdup increased it. The mean drop diameter was related to the Weber number and holdup by an equation. By comparison of mean drop diameters obtained using different impellers, it was shown that the criterion of equal power per volume can be used for estimating drop size when going from one mixing geometry ot another, not too different, geometry at moderate impeller speeds.