Application of CFD to Analyze the Hydrodynamic Behaviour of a Bioreactor with a Double Impeller

Ebrahimi Ebrahimi,Villegas Villegas,Chiappetta Chiappetta,Tamer Tamer,Ein-Mozaffari Ein-Mozaffari

doi:10.3390/pr7100694

Ebrahimi Ebrahimi, Villegas Villegas + Show 3 more

Open Access

https://doi.org/10.3390/pr7100694

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Journal: Processes	Publication Date: Oct 3, 2019
Citations: 23	License type: CC BY 4.0

Affiliation: Toronto Metropolitan University, Sanofi (Canada)

Abstract

Stirred bioreactors are commonly used unit operations in the pharmaceutical industry. In this study, computational fluid dynamics (CFD) was used in order to analyze the influence of the impeller configuration (Segment–Segment and Segment–Rushton impeller configurations) and the impeller rotational speed (an operational parameter) on the hydrodynamic behaviour and mixing performance of a bioreactor equipped with a double impeller. A relatively close agreement between the power values obtained from the CFD model and those measured experimentally was observed. Various parameters such as velocity profiles, stress generated by impellers due to the turbulence and velocity gradient, flow number, and mixing time were used to compare the CFD simulations. It was observed that the impeller’s RPM could change the intensity of the interaction between the impellers when a Segment–Rushton impeller was used. In general, increasing the RPM led to an increase in total power and the stress acting on the cells and to a shorter mixing time. At a constant RPM, the Segment–Rushton impeller configuration had higher total power and stress acting on cells compared to the Segment–Segment impeller configuration. At lower RPM values (i.e., 50 and 100), the Segment–Segment impeller provided a shorter mixing time. Conversely, at the highest RPM (i.e., 150) the Segment–Rushton impeller had a shorter mixing time compared to the Segment–Segment impeller; this was attributed to the high level of turbulence generated with the former impeller configuration at high RPM.

Highlights

Stirred fermenters are widely applied in the pharmaceutical industry to produce pharmaceutical compounds
The objective of this study is to demonstrate the application of computational fluid dynamics (CFD) in investigating the effect of the impeller configuration and impeller rotational speed on the hydrodynamic behaviour and mixing performance of a stirred fermenter equipped with a double impeller
The CFD simulation results are used in order to compare the hydrodynamic behaviour and mixing performance of various simulation cases outlined above

Summary

Introduction

Stirred fermenters (stirred bioreactors) are widely applied in the pharmaceutical industry to produce pharmaceutical compounds. The use of these unit operations has become the leading solution for production of microbial cells at an industrial scale [1]. A stirred fermenter needs to be designed and operated in order to achieve the following: i. To achieve a uniform/homogenous mixing; the uniform mixing guarantees a homogeneous cell suspension and the concentration of nutrients and oxygen (if the process is aerobic) in the culture medium. This increases the fermenter yield [2]

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