Effect of impeller blade height on the drop size distribution in agitated dispersions

Abstract

A common method to achieve a contact of two liquid phases - required for many chemical engineering operations – is the dispersion of one into the other by mechanical agitation. The drop size distribution in such an agitated dispersion is a result of the dynamic equilibrium existing between the breaking and coalescing drops. A comparison has been made of drop diameters produced by four disk type impellers differing only in blade height (DW= 1, 2, 4 and 6 cm). Measurements in situ at 200, 250, 300, 350, 400, 450 rpm and at holdup fractions 0.02, 0.05, and 0.07, showed that the Sauter mean drop diameters increased up to 140 % as the impeller blade height decreased from 6 to 1 cm. Plots of ln α32 vs. ln N, lnα32 vs. ln DT and ln α32 vs. ln αmax gave straight lines.