Comparison of the hydrodynamics and mass transfer characteristics in internal-loop airlift bioreactors utilizing either a novel membrane-tube sparger or perforated plate sparger

Two gas spargers, a novel membrane-tube sparger and a perforated plate sparger, were compared in terms of hydrodynamics and mass transfer (or oxygen transfer) performance in an internal-loop airlift bioreactor. The overall gas holdup ε _T, downcomer liquid velocity V _d, and volumetric mass transfer coefficient K _L a were examined depending on superficial gas velocity U _G increased in Newtonian and non-Newtonian fluids for the both spargers. Compared with the perforated plate sparger, the bioreactor with the membrane-tube sparger increased the values of ε _T by 4.9-48.8 % in air-water system when the U _G was from 0.004 to 0.04 m/s, and by 65.1-512.6 % in air-CMC solution system. The V _d value for the membrane-tube sparger was improved by 40.0-86.3 %. The value of K _L a was increased by 52.8-84.4 % in air-water system, and by 63.3-836.3 % in air-CMC solution system. Empirical correlations of ε _T, V _d, and K _L a were proposed, and well corresponding with the experimental data with the deviation of 10 %.