Application of Computational Fluiddynamics (CFD) to Modeling Stirred Tank Bioreactors

Abstract

The stirred and aerated tank fermentor is still the most important type of bioreactor for industrial production processes. The agitator or agitators are required to perform a wide range of functions: adequate momentum, heat and mass transfer, and mixing as well as gas-dispersion and homogenization of suspensions. As these various operations make different demands, optimization of the individual tasks would result in different design of the impellers. Therefore, agitators used in practice always reflect compromises. Conventional impellers used in fermentation are typically classified into axial and radial flow impellers. Examples of the two groups are illustrated in Fig. 7.1. Of the many impeller geometries, the six-blade disk impeller (Rushton turbine) with gas sparging below the impeller is most often used in standard configurations. However, an interest in using high-flow, low-power-number agitators such as Intermig (Fig. 7.2a), Lightnin A315 (Fig. 7.2b), Prochem Maxflow T (Fig. 7.2c), and Scaba 6SRGT (Fig. 7.2d) has been developed and improved performance of fermentation processes has been reported with such alternative designs [1-3].