GAS HOLDUP AND LIQUID VELOCITY IN AIRLIFT BIOREACTORS CONTAINING VISCOUS NEWTONIAN LIQUIDS

Gas holdup and liquid circulation velocity meassurements were made for a range of liquid viscosities in a 22 l external loop airlift column and 250 l pilot-scale concentric cylinder airlift bioreactor. The resu lts showed that for a fixed superficial gas velocity, liquid circulati on velocity decreased monotonically with increasing liquid viscosity. The gas holdup for a fixed gas flow rate showed an initial increase wi th liquid viscosity followed by a decrease when liquid viscosity incre ased beyond a critical value. These observations could not be describe d satisfactorily using the available models of gas holdup and liquid c irculation.