SCALE-UP OF MIXING IN GASSED MULTI-TURBINE AGITATED VESSELS

A mixing model previously developed for the determination of mixing ti me in gassed tanks stirred by multiple Rushton turbines (Vasconcelos e t al., 1995) was verified for the additional scales of 0.39, 0.56 and 0.72 m vessel diameter. It is now shown that the single adjusted param eter previously required by the model, the air-induced axial velocity parameter nu(ax), is scale-independent with an invariant value of 7 x 10(-2) m/s. Model simulations, with tank and turbine diameters and the number of stages as the only required parameters, deviate 5% on avera ge from the experimentally determined mixing time t(0.05) The model is thus a valuable tool for scale-up of this type of vessels.