HOLDUP MEASUREMENT IN A SCHEIBEL EXTRACTION COLUMN

ABSTRACT The total holdup of a dispersed organic phase in a rotary-agitated Scheibel liquid-liquid extraction column of the first type is studied experimentally. The column is 2 inches in diameter and contains 11 stages with a 4-inch height packed section and a 1-inch height mixing section. The packed section is made of stainless steel wire mesh packing with a 93.74% free area and acts as a settler for the coalescence of droplets. Three systems are studied: benzene/water, methyl isobutyl ketone (MIBK)/water and 20% TBP-80% kerosene/1?M nitric acid. The effects of different phase flow rates and rotation speeds (300-670?rpm) on the dispersed phase holdup are investigated. The results show that the holdup increases with increasing dispersed phase flow rate but does not vary with continuous phase flow rate. For benzene, the holdup is large at low rotation speeds and decreases with increasing rotation speed until a minimum holdup is reached, after this transition point, the holdup increases with increasing rotation speed. This phenomena is analogous to that found in a pulse column. For MIBK and 20% TBP-kerosene, the holdup always increases with rotation speed in our experimental range and the transition point is not observed as M in benzene. This is attributed to the much larger interfacial tension of benzene-water as compared with the other 2 systems.