Gas-Liquid Interfacial Area, Bubble Size and Liquid-Phase Mass Transfer Coefficient in a Three-Phase External Loop Airlift Bubble Column

M. Yoshimoto, S. Suenaga, K. Furumoto, K. Fukunaga and K. Nakao

Abstract
The interfacial area a was measured by the sulfite oxidation method in a three-phase external loop airlift bubble column suspending completely the different concentrations of ion exchange resin particles in aqueous carboxymethyl cellulose (CMC) solutions with a wide range of viscosity. The column had been previously studied for the circulating liquid velocity UL, gas holdup εG and volumetric gas-liquid oxygen transfer coefficient kLa in the two- and three-phase systems. The average bubble size dB and oxygen transfer coefficient kL were obtained as dB = 6 εG/a and kL = (the previous kLa)/a, respectively. The similar studies were carried out in the internal loop airlift and normal bubble columns for comparison. The a values in the external loop airlift were found to be little affected by the column height and particles concentrations, and to decrease with increasing viscosity. All the three columns showed a linear dependence of a on εG. A simple correlation of a, dB or kL was proposed as a function of εG and viscosity for the external loop airlift as well as both internal loop airlift and normal columns. A well-known relationship between kL and dB was confirmed to hold independent of column types and operating conditions for a given two or three phase system.

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Keywords
External loop airlift, three phase flow, suspended solid particles, interfacial area, bubble size, oxygen transfer coefficient