Hydrodynamics and mass transfer studies in a novel external-loop airlift reactor

Abstract

A novel external-loop airlift reactor in combination with a fluidized bed was proposed in this work. The gas sparger located in the upper section of the riser allowed the heavy solid particles to fluidize in the lower section of the riser, and also separated the gas-liquid and solid-liquid contact. The reactor, with high degree of design flexibility, is expected to handle fragile cells which are shear-sensitive. Studies were carried out using three different types of solid particles with three different solid loading in the reactor. The solids-free standard external-loop airlift reactors with different H/D ratio were also investigated for comparison. The gas holdup, liquid circulation velocity, liquid mixing time, and the fluidized-bed expansion were studied. Several models reported were applied to the hydrodynamic performance of the reactor. The oxygen transfer in the liquid was also measured and the k(L)a(L) value was obtained using a dynamic technique. Empirical correlations describing the proposed reactor are presented in this paper and very good agreement could he found.