Abstract
The interplay between fluid dynamics, mass transfer and chemical reaction in bubbly flows is not yet sufficiently understood. In order to determine the reaction kinetics without mass transfer limitations a new reactor concept has been developed. As an example for industrial relevant reactions, the non-catalyzed oxidation of toluene with oxygen was investigated. For a simplified reaction network rate expressions and corresponding kinetic coefficients have been identified. The reaction kinetics was used to numerically study the impact of the bubble wake on conversion and selectivity. The oxidation of toluene was found to be too slow for being affected by the bubbly flow. This has been confirmed by experiments in a technical size bubble column at industrial conditions. Numerical studies show that only reactions with a rate constant in the range of 0.1 < Da1 < 1000, the so-called mixture-masked range, are influenced by the flow pattern behind a rising bubble. Slow reactions can be treated as bulk phase reactions, while fast reactions take place exclusively in the vicinity of the bubble surface, thus are not biased by the non-ideal mixing in the bubble wake. In the mixture-masked range, transport barriers from the stationary bubble vortex have a significant influence on the course of the reaction.
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Acknowledgements
This work was funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation)—priority program SPP1740 “Reactive Bubbly Flows” (237189010) for the project NI 932/9-2 (256634524).
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Gast, S., Tuttlies, U., Nieken, U. (2021). Determination of Intrinsic Gas-Liquid Reaction Kinetics in Homogeneous Liquid Phase and the Impact of the Bubble Wake on Effective Reaction Rates. In: Schlüter, M., Bothe, D., Herres-Pawlis, S., Nieken, U. (eds) Reactive Bubbly Flows. Fluid Mechanics and Its Applications, vol 128. Springer, Cham. https://doi.org/10.1007/978-3-030-72361-3_10
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DOI: https://doi.org/10.1007/978-3-030-72361-3_10
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