Mass Transfer and Mixing in an Ejector-Induced Downflow Slurry Bubble Column
2013
Sivaiah, Mekala | Majumder, Subrata Kumar
The downflow slurry bubble column reactor is gaining importance as a simple and inexpensive means of achieving efficient multiphase contact and mass-transfer operations. Knowledge about the effects of solids on gas–liquid–solid systems is minimal in the literature. In the present work, the effect of the presence of solids on the mass-transfer characteristics for gas–liquid–solid system is experimentally investigated in a downflow slurry bubble column with an internal diameter of 0.05 m. The mass-transfer coefficient was evaluated using the electroreduction of ferricyanide ions as the model reaction. The effects of superficial slurry velocity, gas velocity, slurry viscosity, and gas holdup on the mass-transfer coefficient were analyzed. The experimental results showed that the mass-transfer coefficient in the column is influenced more by the superficial slurry velocity than the superficial gas velocity. In this work, the mass-transfer efficiency in the gas–liquid–solid downflow bubble column reactor was analyzed for different concentrations of the slurry (0.1–1.0 wt %) and different sizes of the particles (2.21–96.0 μm). Empirical correlations were developed for the downflow slurry system with the different variables to interpret the mass-transfer phenomena. The developed correlation for mass-transfer efficiency as a function of quality of mixedness was also interpreted by the information entropy theory. The present analysis on mass-transfer characteristics and models for predicting the mass-transfer coefficient can provide insight into a further understanding of multiphase reactors in industrial applications.
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