Characterization of a multi-impeller bioreactor using a staged model
Thesis/Dissertation
·
OSTI ID:7271713
Oxygen gas-to-liquid mass transfer is often the limiting rate in batch bioprocesses which occur in aerated and agitated reactors. The accessment of oxygen absorption, with the intention of boosting the rate, currently relies on information gathered from the gas inlet and outlet streams, and on dissolved oxygen tension monitored at a single point. These limited measurements are correlated with agitation power and aeration rate which results in lumped, macroscopic parameters. Modifications are then proposed based only on this narrow view of the system. This research project has taken a different approach. A multi-impeller bioreactor has been mathematically divided into smaller compartments around which oxygen transfer rates have been monitored and modeled. After making interior measurements the overall oxygen transfer rate has been resolved into components, i.e. that which occurred in the upper and lower halves of a twin-impeller, aerated reactor. A low density yeast bioprocess served as the oxygen sink. Operating conditions in the 400-liter liquid volume ranged from agitation rates of 100 to 300 RPM and aeration rates of 100 to 250 SLPM. The oxygen transfer rate and the mass transfer coefficients were compared, and throughout the range, the lower compartment was found to be the most effective in oxygenating the medium. The lowest turbine used less power to transfer often twice as much oxygen to the liquid relative to the upper turbine. Greater gas dispersion, in the lower compartment was easily created and sustained due to the close location of the turbine to the sparger. The observed differences challenged the conventional belief that increased agitator power is the solution to high oxygen demand, when in fact an increase in the number of spargers may be more efficient.
- Research Organization:
- Virginia Univ., Charlottesville, VA (USA)
- OSTI ID:
- 7271713
- Country of Publication:
- United States
- Language:
- English
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