A novel view into aerated stirred tanks: magnetic resonance imaging

The understanding of hydrodynamics and aeration processes in stirred tanks is crucial for reactor optimization and scale-up. Classic means of characterizing these phenomena rely on optical access, excluding system with high aeration rates, suspended particles or non-opaque fluids, or only provide local point-information using intrusive probes [1]. In contrast, Magnetic resonance imaging (MRI) is able to investigate such opaque systems and provide novel, non-invasive insights into small-scale bioreactor systems [2]. Because the signal in MRI originates from the spins of 1H nuclei of fluids, it can provide contrast between these fluids and the MRI-silent gas phase. Moreover, the flow of liquids can be directly measured using phase contrast velocimetry, without the need for tracer particles. In this work, we extended MRI of commercially-relevant bioreactors to a larger scale of 250 ml, using a unique vertical MRI system which allows samples of diameters up to 400 mm and height of 3 m to be investigated. The contrast information allows the extraction of spatially resolved gas distribution, enabling the calculation of residence time and determination of stirrer efficiency. Using MR velocimetry, three-dimensional flow maps of whole vessels can be reconstructed, which reveal changing flow patterns with varying aeration rates and stirrer speeds. Both approaches will provide temporal averaged data with a spatial resolution up to 1 x 1 x 2 mm³. This data will improve our fundamental physical understanding of the hydrodynamics in reactor systems and provide datasets for the validation of numerical models as well as empirical models for stirred tank reactors.

Subjects

MRI

Stirred tanks

aeration

two phase

DDC Class

660.284: Chemical Reactors

530.42: Fluid Physics

537: Electricity and Electronics

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https://creativecommons.org/publicdomain/zero/1.0/

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publishedVersion

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BioProScale_Till_Präsi.pdf

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Main Article

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4.54 MB

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A novel view into aerated stirred tanks: magnetic resonance imaging