Thesis

A passive and active acoustic study of bubbles related to bioprocess monitoring

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Awarding institution
  • University of Strathclyde
Date of award
  • 2010
Thesis identifier
  • T12660
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Abstract
  • Bioprocesses are operated sub-optimally due to a lack of real-time physical and chemical information and the complexity and variability of biological materials. Currently, optical techniques are favoured for in-line and at-line monitoring of bioprocesses while chromatographic techniques are used as an off-line assay method. In-line probes require contact with the fermentation broth, which raises sterility issues. Therefore, the development of measurement techniques that can be applied non-invasively is attractive. Acoustic measurements can be invasive or non-invasive and can be used to obtain physical property information, e.g. bubble size. Therefore, the overall aim of this work is to utilise some of the developments made in passive and active acoustics and apply this to the study of bubbles in the area of bioprocess monitoring. For this work acoustic emission and active acoustic techniques have been investigated. Acoustic emission was used to characterise bubble size by Minnaerts theory. A Design of Experiments approach was used to investigate the effects of the sparger diameter, flow rate and viscosity on bubble production. It was found that using acoustic emission bubbles can be characterised in terms of their resonancefrequency, where resonance frequency was inversely proportional to bubble diameter. Also it was shown that increasing viscosity increased repeatability. Repeatability was found to be as low as 0.9 %. Following this a test cell was developed for the active acoustic characterisation of bubbles in water. By using active acoustics, bubbles can be characterised in terms of the frequency spectra of the received signal and the area under the spectra. Using active acoustics it was found that for bubbles of estimated diameter of 1, 2 and 4 mm the area under the spectra increased linearly with increasing bubble diameter. The lowest repeatability obtained was an RSD of the peak area of 6.8 %.
Resource Type
DOI
Date Created
  • 2010
Former identifier
  • 819275

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