Gas-liquid dispersion in stirred tanks is a commonly used industrial process, e.g., bio-pharmaceutical or fine-chemical manufacturing. While CFD models have been used to predict gas holdup, bubble size distribution and mass transfer coefficients, there have been fewer studies on deploying the CFD models to range of operating conditions. This study focuses CFD simulation at different rotational speed (rpm) and gas flow rates to create a comprehensive “Simulation Design Space” for mass transfer co-efficient (Kla). Mass transfer co-efficient is experimentally obtained by measuring Dissolved Oxygen (DO) concentration by absorption in pure water. In current study, simulation model is developed numerically to calculate DO through multiphase and multispecies CFD simulations. Population balance model is coupled with the Eulerian multiphase-multispecies model to predict the bubble size distribution and oxygen distribution. The study also looks into effects of turbulence on drag co-efficient which is a key factor in predicting an accurate bubble size distribution and gas hold-up. Simulation best practices are developed and then deployed for validation of the model against experimental data [1] on wide range of operating conditions.
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Bubble size distribution on planes between baffles
| Variation of gas holdup with gas flow rate
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1. M. Laakkonen et al., Chemical Engineering Science 62 (2007) 721 – 740
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