Kinetics of drops breakup in agitated vessels
L.N. Braginsky and M.A. Belevitskaya
Abstract
The theoretical model which takes the stochastic character of the effect of turbulent pulsations into account and allows for the effect of viscosity of continuous and dispersed phases is proposed for describing the process of drops breakup in turbulent flow. It is shown that under certain conditions an increase in viscosity of the phases may result in decreasing sizes of drops. The equations are also obtained for estimating the maximum value of energy dissipation within the zones of stirrer paddles as a function of the design of the stirrer and vessel, their scales, mixing intensity and statistical data on the drops residence time distribution within various vessel zones. Relationships are obtained for drops size estimating in the systems with SAS, with the proper account taken of the agitation duration. Theoretical studies of dispersion were conducted on six pairs of immiscible liquids, with viscosity varying at 600 times. Measurements of the drop size distribution were conducted in the baffled vessels ranging from 4.5 dm3to 0.25 m3 in volume and provided with stirrers of various types and sizes (17 stirrers altogether), with an agitation duration of up to 2 hours.
The experimental results have confirmed the principal analytical conclusions concerning the effects of energy dissipation, stirrer dimensions, vessel volume and viscosity of continuous and dispersed phases on the kinetics of dispersion. It is shown what the obtained equations can be used for drops size estimating.