Collection of Czechoslovak Chemical Communications - digital archive 

Abstract

The mean volumetric hold-up of the dispersed phase and the limiting flow rates of phases in five sizes of experimental vibrating plate extractors VPE were measured and the results compared with the relations of Richardson and Zaki, Míšek and Ishii and Zuber for the relative phase velocity. The experiments were performed with the system toluene-water, toluene dispersed. All the relations were found to describe the dependence of hold-up on flow rates very well. They also allowed a satisfactory estimation of the limiting phase velocities. Within the range of the experimental conditions the characteristic velocity as well as the limiting phase velocities could be approximated by linear functions of the frequency of vibrations. For the columns studied no influence of column size on limiting velocities was detected. The deviations of individual columns from geometrical similarity, however, brought about an appreciable effect both on the hold-up and on the flooding rates. This phenomenon has been explained in terms of longitudinal hold-up profiles, the shape of which depends on the boundary conditions in the particular column. This explanation was corroborated by case studies using a polydisperse mathematical model which show that even in the presence of hold-up profiles the effect of phase velocities on the mean hold-up can be correlated by means of the investigated relations with constant parameters and that the parameters depend on the hold-up profiles form.