Oxygen mass transfer into aerated CMC solutions in a bubble column

Area of Science:

• Biochemical Engineering
• Chemical Engineering
• Fluid Dynamics

Background:

• Volumetric mass transfer coefficients (k(L)a) in carboxymethyl cellulose (CMC) solutions within bubble column bioreactors show inconsistent literature values.
• Accurate k(L)a determination is crucial for optimizing bioreactor performance and scale-up.

Purpose of the Study:

• To re-investigate oxygen mass transfer in CMC solutions using a bubble column bioreactor.
• To determine k(L)a and liquid phase dispersion coefficients.
• To develop a correlation for k(L)a applicable to different flow regimes and fermentation broths.

Main Methods:

• Experiments were conducted in a 14-cm-i.d. x 270-cm-height bubble column using various spargers.
• The axial dispersed plug model was fitted to experimental oxygen concentration profiles to determine k(L)a and dispersion coefficients.
• CMC solutions and Penicillium chrysogenum fermentation broth were utilized.

Main Results:

• Liquid phase dispersion coefficients for CMC solutions were higher than predicted by existing correlations.
• k(L)a values were generally lower than those reported in previous studies.
• A correlation for k(L)a in developing and established slug flow was developed, showing dependence on gas velocity and effective viscosity.
• This correlation demonstrated high accuracy when applied to Penicillium chrysogenum fermentation broth.

Conclusions:

• The study provides new insights into oxygen mass transfer in CMC solutions, highlighting the influence of flow regime and rheological properties.
• The developed correlation offers a reliable method for predicting k(L)a in slug flow regimes, particularly for bioprocesses.
• The findings contribute to a better understanding and design of bubble column bioreactors for fermentation applications.