Abstract
Gas hold up was measured in mechanically agitated vessels fitted with dual impellers. Different impellers like Pitched blade turbine and Disc turbine were used. 5 different combinations of dual impellers were used. A tank of 0.45 m internal diameter with an impeller diameter of 0.15m was used. Superficial gas velocity was varied from 0.005m/sec to 0.01 m/ sec. Correlations are proposed for gas hold ups for different combinations of impellers. Optimum combination of dual impellers for maximum gas hold up has been identified. The effect of bottom clearance, inter impeller clearance and physical properties like surface tension on gas hold up were also studied for the optimum combination of impellers
Highlights
IntroductionMixing is an important unit operation and has extensive applications in chemical, bio chemical and pharmaceutical industries
2.2 Gas hold up (HG): It is the ratio of gas phase volume to total volume
The interfacial area and mass transfer rate are dependent on holdup
Summary
Mixing is an important unit operation and has extensive applications in chemical, bio chemical and pharmaceutical industries. Multiple impellers are preferred over single impellers to provide better gas utilization, narrow spread in the residence time distribution in the flow systems and higher surface area per unit volume for heat transfer. They provide low shear compared to single impellers due to overall lower speed of operation at equal power levels. They can control the dispersed phase hold up and residence time. Multiple impellers are preferred in shear – sensitive micro organism- enriched fermentation reactors
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