Bubble column reactors (BCRs) are valuable in the biochemical industry for their efficient gas-liquid mass transfer and mixing capabilities. A key performance parameter in BCRs is gas holdup, which can be significantly influenced by components present in fermentation broths. This study investigated the effect of the important fermentation products ethanol, n-propanol, iso-propanol, n-butanol, acetic acid, and lactic acid on gas holdup. These components impact bubble coalescence via the so-called Marangoni effect. This study correlates gas holdup with the dimensionless Marangoni number (Ma) in BCRs. The model proposed by Wang et al. [1] successfully predicts 87% of the measured holdup values within a 10% error margin.
Additionally, correlations for gas holdup distribution are compared, with Schweitzer et al. [2] providing the most accurate local predictions (70% within 10% error). This study provides a comparative overview of gas holdup correlations relevant to BCRs and demonstrates the significance of incorporating the Marangoni effect in predictive models.
Research on local gas holdup in BCRs often requires invasive measurement techniques. X-ray tomography (XRT) enables measurements of gas without disruption of the flow associated with traditional methods such as optical fiber probes. However, noise from X-ray scattering and artifacts from beam hardening still hinder accurate quantification of gas holdup. This study presents a methodology for processing X-ray data to overcome these challenges. X-ray data corrected for scatter and beam hardening results in tomographic reconstructions with a gas holdup profile similar to what was found with an optical fiber probe. This correction methodology can assist other researchers using similar X-ray setups by improving the accuracy of gas holdup measurements in multiphase systems.