Modelling of Mixing in Stirred Bioreactors 3. Mixing Time for Aerated Simulated Broths

Abstract

The mixing time is one of the most useful criterion for mixing intensity of 
fermentation broths and for scale-up of biosynthesis processes. This parameter value depends mainly on the rheological characteristics of the broths, bioreactor construction and fermentation conditions.

This paper presents the experiments on mixing efficiency for aerated media for a laboratory stirred bioreactor with double turbine impeller. The effects of stirrer rotation speed, air volumetric flow rate and stirrers position on the shaft on mixing time for aerated water and simulated broths (CMCNa solutions) were analyzed. Compared with non-aerated broths, the results indicated that the variation of mixing time with the considered parameters are very different, due to the complex flow mechanism of gas-liquid dispersion, mechanism which is changed by changing the broths properties or fermentation conditions.