Characterization of flow intensity in continuous centrifuges for the development of laboratory mimics

Predicting the recovery of “delicate” biological materials by centrifugation using laboratory centrifuges has been a major challenge to biochemical engineers partly because of the difficulty in accurately quantifying the shear stresses in continuous-flow industrial centrifuges and partly because the clarification and dewatering conditions in the laboratory units do not represent those occurring in industrial centrifuges. In this paper, the flow field in the feed zone of an industrial multichamber-bowl centrifuge is mapped and its profile of energy dissipation rate established using computational fluid dynamics (CFD). A small high-speed rotating-disc device is designed with the capacity to reproduce the CFD-predicted energy dissipation rates in the feed zone. Milliliter quantities of the process material are shear-treated in the device operating at a speed that mimics the local critical flow conditions in the industrial centrifuge. The results are used to assess the impact of flow conditions in the feed zone of the centrifuge on the physical properties of protein precipitates and on their predicted recovery using a laboratory centrifuge. This approach was used to explain the reduction in the performance of the centrifuge from the predicted 88% clarification to the observed 39% clarification of the precipitate particles. The combination of the small high-speed disc device and the laboratory centrifuge is particularly advantageous when dealing with biological products at the early stages of process development for which only small quantities of test material are often available.

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