University of Oulu

Petri Tervasmäki, Marko Latva-Kokko, Sanna Taskila, Juha Tanskanen, Mass transfer, gas hold-up and cell cultivation studies in a bottom agitated draft tube reactor and multiple impeller Rushton turbine configuration, In Chemical Engineering Science, Volume 155, 2016, Pages 83-98, ISSN 0009-2509,

Mass transfer, gas hold-up and cell cultivation studies in a bottom agitated draft tube reactor and multiple impeller Rushton turbine configuration

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Author: Tervasmäki, Petri1; Latva-Kokko, Marko2; Taskila, Sanna1;
Organizations: 1University of Oulu, Chemical Process Engineering, P.O. Box 4000, FI-90014 Oulun yliopisto, Finland
2Outotec Oyj, Outotec Research Center, P.O. Box 69, FI-23101 Pori, Finland
Format: article
Version: accepted version
Access: open
Online Access: PDF Full Text (PDF, 1.1 MB)
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Language: English
Published: Elsevier, 2016
Publish Date: 2018-07-30


Gas–liquid mass transfer is an important phenomenon in aerobic microbial cultivations, and the mass transfer performance of an industrial reactor strongly affects the overall process economics. Traditionally, industrial and laboratory bioreactors have been agitated with flat disc turbines (Rushton turbines) although there are many variants to this design. In addition, pneumatically agitated reactors such as bubble columns and airlift reactors have been studied and used by the industry.

In this study we utilize an agitated draft tube reactor in cell cultivation and mass transfer studies. A standard reactor geometry agitated with three Rushton turbines was compared to Outotec OKTOP®9000 reactor which is a draft tube reactor agitated with a single impeller located just below the draft tube. The experiments included cell cultivation with Pichia pastoris yeast, determination of overall mass transfer coefficient by dynamic gassing in method and measurement of local gas hold-up by electrical impedance tomography (EIT). In addition, agitation power was estimated from the power consumption of the DC-motor.

OKTOP®9000 reactor was found to have higher kL a values than the STR with similar agitation power and gas flowrate. The overall gas hold-up was similar in both geometries at same power inputs and gas flow rates. However, some significant differences were detected in the distribution of gas phase between the two geometries especially in the axial direction. Also changes in the gas dispersion regime can be detected from the spatial distribution of the gas hold-up measured by EIT. The cell cultivation experiments showed the applicability of this type of agitated draft tube reactor to bioprocesses although a direct comparison with Rushton geometry is not straightforward.

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Series: Chemical engineering science
ISSN: 0009-2509
ISSN-E: 1873-4405
ISSN-L: 0009-2509
Volume: 155
Pages: 83 - 98
DOI: 10.1016/j.ces.2016.07.048
Type of Publication: A1 Journal article – refereed
Field of Science: 215 Chemical engineering
Funding: Petri Tervasmäki acknowledges Fortum Foundation for a personal research grant (201500179).
Copyright information: © 2016. This manuscript version is made available under the CC-BY-NC-ND 4.0 license