Estudo da hidrodinâmica de uma coluna de extração Kühni

Abstract

This work aimed at the experimental study of the hydrodynamic behavior of liquid-liquid extraction columns. A section of a pilot scale Kühni column containing 5 stages with 150 mm of diameter has been used. The study has been carried out in the absence of mass transferbetween phases. The binary system water/Exxsol D-80 was employed. In all runs, water has been set as the continuous phase and the column was operated in a closed circuit mode. The hydrodynamics has been assessed regarding the average drop size, drop size distribution andhold-up (total and local). The following operational variables have been investigated: rotor speed (60, 90, 120, 150 and 180 rpm), flowrate of the dispersed phase (1.240 and 2.000 mL/min), flowrate of the continuous phase (1.240 and 2.000 mL/min) and column sections heights (distributor and stages 1, 3 and 5). A photographic method has been applied to measure drop sizes and distributions. It has been observed that drop size distributions follow a lognormal distribution function. Drop sizes were reduced with the increase of rotor speed, thus resulting in narrower size distributions. Empirical correlations proposed in the literature were employed in this study and the calculated diameters were compared to the experimental Sauter diameters. Considerable deviations were obtained and a new correlation was proposed in thiswork, with predictions presenting an 8,2 % deviation. Regarding hold-up measurements, it has been found a significant dependence on the flowrates of the dispersed phase and rotor speed. Smaller drops present longer residence times in the column stages, thus resulting in an increase of the total and local hold-up. The results obtained in this study have contributed to better understand the hydrodynamic behavior of binary systems in sections of a Kühni column.