Scale-down studies on the hydrodynamics of two-liquid phase biocatalytic reactors

Area of Science:

• Biochemical Engineering
• Chemical Engineering
• Process Scale-up

Background:

• Successful scale-up of two-liquid phase bioconversion relies on maintaining constant interfacial area per unit volume.
• Limited hydrodynamic data and undefined scale-up bases hinder the advancement of these processes.

Purpose of the Study:

• To investigate the hydrodynamics of a whole-cell bioconversion process.
• To define and verify a suitable basis for scaling up two-liquid phase bioconversion reactors.
• To compare scale-up strategies based on constant power input per unit volume versus constant tip speed.

Main Methods:

• Performed experiments in geometrically similar 3-L and 75-L reactors with Rushton turbine impellers.
• Measured power input using an air-bearing technique for single-phase and two-phase mixing.
• Utilized in-situ light-backscattering to measure drop size distributions and Sauter mean diameters (d32) on-line.

Main Results:

• Power number reached a constant value of 11 at Re>10,000 for both single-phase and two-phase systems.
• Drop size diameter (d32) decreased with increasing agitation rate, with values ranging from 30-50 micrometers.
• Constant power input per unit volume proved to be the most effective scale-up basis, yielding identical d32 values and drop size distributions at both scales.

Conclusions:

• Constant power input per unit volume is the optimal scale-up parameter for two-liquid phase bioconversion processes.
• The study provides correlations for predicting d32 values, aiding process design.
• The developed scale-down methodology allows for rapid evaluation of other bioconversion processes, identifying potential scale-up issues early.