Scale-up of Aerated Industrial Multistage Rushton Impeller Bioreactors
with Complex Rheology
Abstract
The power input and gas-liquid mass transfer rank among the most
important industrial fermentation process parameters. The present study
analyzes the power input and gas hold-up as a function of the flow
regime, impeller diameter, and rheological properties in a pilot scale
reactor (160 L) equipped with four Rushton impellers. This leads to four
dimensionless numbers for predicting measurements in pilot and
industrial bioreactors (110 and 170 m3) with a standard deviation of 7
% to 29 %. This is unparalleled for the underlying aerated and
non-Newtonian fermentation broths. Several existing correlation
equations are discussed to be dissatisfying (up to 130 % deviation),
and might be sufficiently valid only within scale or for small scaling
factors. The introduced approach predicts adequately accurate over three
orders of magnitude. Based on these encouraging results, we identified
the Galilei number and the power concept as the central elements in
combination with the consequent dimensional analysis for an efficient
scaling betweeen pilot and industrial scale.