Comparison of models to measure volumetric mass transfer coefficients in bubble columns reactors
Onkar N. Manjrekar, Yujian Sun, Milorad P. Dudukovic
Chemical Reaction Engineering Laboratory (CREL), Department of Energy, Environmental and Chemical Engineering, Washington University in Saint Louis, MO 63112
Successful estimation of gas-liquid mass transfer coefficient is a key in design of multiphase reactors. In literature, the models used to measure volumetric mass transfer coefficient assume either the liquid phase to be completely mixed, or use axial dispersion model for the liquid phase. In the present work, gas-liquid mass transfer coefficients are evaluated in bubble column reactor covering bubbly to churn-turbulent flow regime. It was observed that when completely mixed model is used for liquid phase at low superficial gas velocities model does not fit experimental data well. Hence, a new model is proposed in which liquid phase is assumed to be well mixed, and the additional equation for gas phase is included. The gas phase is assumed to be in the plug flow. This new model is capable of explaining experimental data in at low as well as at high superficial gas velocities. Volumetric mass-transfer coefficients are measured using the dynamic gas disengagement technique with both step-up and step-down method. Discussion of results of different models to measure volumetric mass transfer coefficients would be presented.