Mixing characteristics of unbaffled bioreactor with levitating radial impeller

In the pharmaceutical and biotechnology industries, ensuring the cleanliness and sterility of the process environment is of utmost importance. To achieve this, some commercially available bioreactors are designed as unbaffled vessels with an eccentrically mounted, magnetically driven impeller. Contrary to the well-studied nature of turbulent mixing in standard baffled reactors, the mixing performance in such atypical vessels has not been thoroughly explored in the literature. This study aims to fill the knowledge gap on this subject by focusing on the mixing time in an atypical reactor using two experimental techniques, conductometry, and decolorization. The conductometric results demonstrate that the mixing times of the atypical reactor remain similar to the baffled configurations up to a height-to-diameter ratio of 1.2. Above this ratio, mixing times rapidly increase. Based on the experimental results, correlations for the design of standard and atypical vessels with small radial impellers have been proposed, also concerning the liquid height. Furthermore, the decolorization experiments in the atypical reactor revealed the formation of the segregated vortex region, in which the homogenization process takes up to four times longer period than is required for the remainder of the reactor volume. The impact of this vortex formation on the vessel mixing characteristics is discussed.

Automated summary

In the pharmaceutical and biotechnology industries, ensuring the cleanliness and sterility of the process environment is crucial. The study focuses on the mixing time in an atypical reactor using two experimental techniques, conductometry and decolorization, and fills the knowledge gap on the mixing performance in such vessels. The experimental results propose correlations for the design of standard and atypical vessels and highlight the impact of segregated vortex formation on vessel mixing characteristics.