Liquid—Solid Mass Transfer in Aerated Suspensions

Abstract

Liquid—solid mass transfer coefficients, k s were determined using ion exchange resin beads of various diameters in a bubble column. The viscosity of the liquid phase was varied from 1 to 55 mPa s by applying aqueous solutions of glycol, glucose, and polyethylene glycol. The k s values increased with the gas velocity up to about 6 cm/s, but are constant at higher gas throughputs. This indicates that in bubble columns the amount of energy dissipated cannot be increased arbitrarily, but tends to an upper limit. In higher viscosity media the particle diameter has only a minor influence on k s. The k s values foloow film-penetration theory; in higher viscosity media (viscosities above 20 mPa s) the film model seems to predominate. The measured data can be well correlated by the Reynolds number defined by Kolmogoroff's theory of isotropic turbulence. However, this does not necessarily imply the validity of that theory. The k s data are in reasonable agreement with results reported for other systems and in two-phase (liquid—solid) stirred tanks.