Local volumetric mass transfer coefficients in sections of multiple-impeller stirred tank reactors: Data analysis

0569764 - ÚCHP 2024 RIV GB eng J - Journal Article
Žák, A. - Zedníková, Mária - Moucha, T.
Local volumetric mass transfer coefficients in sections of multiple-impeller stirred tank reactors: Data analysis.
Chemical Engineering Research and Design. Roč. 190, FEB 2023 (2023), s. 829-841. ISSN 0263-8762. E-ISSN 1744-3563
Institutional support: RVO:67985858
Keywords : Gas-liquid mass transfer * fermenters design * hydrodynamics * impellers pumping intensity
OECD category: Chemical process engineering
Impact factor: 3.9, year: 2022
Method of publishing: Open access with time embargo

The analysis of local values of volumetric mass transfer coefficient, kLa, was performed to identify the effects of local hydrodynamics on the mass transfer rate in multiple-impeller stirred tank reactors. The database of kLa values measured by Dynamic Pressure Method was analysed. The database provides data for two vessel sizes (laboratory and pilot-scale reactor), a wide range of operational conditions (gas flow rate, impeller speed), various
impeller geometries and sizes and four different batches including viscous media. The local kLa values in multiple impeller configurations were measured in several positions corresponding to the individual impeller regions. The overall kLa value averaged through the whole volume is considered as the best representation of the correct kLa value. Different hydrodynamic effects on mass transfer rate were obtained in the two end regions. In the bottom region, the local kLa values increase with impeller speed faster than the overall kLa. The opposite behaviour was obtained in the uppermost region corre-sponding to the decrease of power consumption and the mass transfer rate with increasing surface aeration under high impeller speeds. The best representation of the overall kLa value was obtained in the middle position of the vessel, where the exchange flows bring the liquid saturated to different measure from the end regions. Even if the local kLa data in individual impellers' regions are shifted to the average values due to the inter-impeller exchange flows, the differences between them are still significant. We show the local kLa values by the combination of the data measured at different liquid level heights. The results can be used in the fermenter design with various impeller combinations.
Permanent Link: https://hdl.handle.net/11104/0341099