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Analyzing the Effect of Using Axial Impellers in Large-Scale Bioreactors
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  • Sören Bernauer,
  • Philipp Eibl,
  • Christian Witz,
  • Johannes Khinast,
  • Timo Hardiman
Sören Bernauer
Sandoz GmbH

Corresponding Author:[email protected]

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Philipp Eibl
Technische Universitat Graz
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Christian Witz
Technische Universitat Graz
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Johannes Khinast
Technische Universitat Graz
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Timo Hardiman
Sandoz GmbH
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In high-performance industrial fermentation processes, stirring and aeration may account for significant production costs. Compared to the widely applied Rushton impellers, axial-pumping impellers are known to yield a lower power draw and at the same time improve mixing. However, their lower gas dispersion capability requires stronger agitation, compromising these benefits. Diverse advanced impeller forms have been developed to cope with this challenge. We apply alternating radial and axial impellers and demonstrate strong gas dispersion and energy-efficient mixing for the first time in a large-scale (160 m 3) bioreactor, based on experimental and CFD simulation data. For equal operating conditions (stirrer speed, aeration rate), this setup yielded similar gas hold-ups and better mixing times (-35 %) compared to a classical Rushton-only configuration. Hence, applying a radial impeller on an upper level for improving gas dispersion maintains the benefits of axial impellers in terms of reducing energy demand (up to -50 %). We conclude that this effect is significant only at large-scale, when bubbles substantially expand due to the release of the hydrostatic pressure and have time to coalesce. The work thus extends current knowledge on mixing and aeration of large-scale reactors using classical impeller types.
31 Jan 2022Submitted to Biotechnology and Bioengineering
31 Jan 2022Submission Checks Completed
31 Jan 2022Assigned to Editor
26 Feb 2022Reviewer(s) Assigned
26 Apr 2022Review(s) Completed, Editorial Evaluation Pending
26 Apr 2022Editorial Decision: Revise Minor
02 May 20221st Revision Received
04 May 2022Submission Checks Completed
04 May 2022Assigned to Editor
11 May 2022Reviewer(s) Assigned
19 Jun 2022Review(s) Completed, Editorial Evaluation Pending
19 Jun 2022Editorial Decision: Accept
Sep 2022Published in Biotechnology and Bioengineering volume 119 issue 9 on pages 2494-2504. 10.1002/bit.28163