HYDRODYNAMICS AND MASS-TRANSFER STUDIES IN A NOVEL EXTERNAL-LOOP AIRLIFT REACTOR

A novel external-loop airlift reactor in combination with a fluidized bed was proposed in this work. The gas sparger located in the upper se ction of the riser allowed the heavy solid particles to fluidize in th e lower section of the riser, and also separated the gas-liquid and so lid-liquid contact. The reactor, with high degree of design flexibilit y, is expected to handle fragile cells which are shear-sensitive. Stud ies were carried out using three different types of solid particles wi th three different solid loading in the reactor. The solids-free stand ard external-loop airlift reactors with different H/D ratio were also investigated for comparison. The gas holdup, liquid circulation veloci ty, liquid mixing time, and the fluidized-bed expansion were studied. Several models reported were applied to the hydrodynamic performance o f 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 pap er and very good agreement could be found. (C) 1997 Elsevier Science S .A.