Mass transfer and gas-liquid circulation in an airlift bioreactor with viscous non-Newtonian fluids

Abstract

In an internal loop airlift reactor of 55 l working volume, gas-liquid volumetric oxygen mass transfer coefficient k L a, gas holdup ϵ G and liquid circulation time t c were measured with the solution of carboxymethyl cellulose to simulate the performance of a reactor with highly viscous broth. Electric conductivity and oxygen probes were used to measure the local gas holdup, liquid circulation time and oxygen mass transfer coefficient in the individual sections of the reactor (riser, downcomer and separator) and the total reactor respectively. The values of k L a in the riser, downcomer and separator sections of the reactor were also estimated and compared with that in the total reactor. The results showed that both k L a and ϵ G increased with increasing gas velocity while t c decreased with increasing gas velocity. Correlations and comparisons with work reported in the literature are also presented. Data showed that the methods developed for k L a measurements in the individual and total reactor were application to the studies of internal loop airlift reactors.