Hydrodynamic characterization of mixer-settlers

An experimental study has been done on the hydrodynamics of a stage mixer-settler to obtain an appropriate design. Immiscible phases can be separated by liquid-liquid extraction processes. Evaluation of extraction efficiency, mass transfer coefficient in dispersed phase, distribution coefficient, and effect of different operational parameters are the most important problems in mixer-settler design. Hence, in this paper several tests are performed to investigate full factorial design of experiments. Since each test was repeated seven times, the repeatability of the test is confirmed (P = 1 bar and t = 25 degrees C). Sauter diameter is determined by photographing both the mixer and settler in each test; Dispersion wedge is determined by photographing the settler. The Sauter diameter is compared with the Calderbank model; finally, a model is suggested. Holdup quantity is measured by a vacuum pump at the end of each test. Another aim of this paper is evaluation of separation mechanism under different impeller speeds and volume fractions. The effect of impeller speed in constant ratio of phases, flow rate, and hold up are evaluated, and the effect of phase flow rate ratios in constant impeller speed on extraction efficiency, mass transfer coefficient and distribution coefficient are determined. (C) 2008 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.