In the present work, self-agitated impellers, as a novel type of internals, have been proposed for improving hydrodynamic and mass transfer characteristics of external-loop airlift reactors. The influence of inserted self-agitated impellers, in the riser section, in various liquid phases and with different sparger types, on main hydrodynamic parameters, was studied. The results show that the insertion of impellers led to significant bubble breakage and decrease in mean bubble size, particularly in pseudoplastic liquid. Obtained riser gas holdup values were up to 47% higher, in comparison to the configuration without impellers. Higher improvements were obtained with single orifice, given that this is the least effective gas distributor. Even though impellers represent an obstacle to the flow, relatively low reduction (about 10%) in downcomer liquid velocity was observed, for all investigated cases. Having this in mind, the benefit of inserting self-agitated impellers for improving the performance of external-loop airlift reactors was apparent. (C) 2016 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.
