| Summary: | 碩士 === 國立清華大學 === 化學工程學系 === 89 === Liquid mixing characteristics were studied for the airlift reactor operating with net draft tube. The experimental reactor had a working volume of 26 L, column diameter of 0.13 m, and total height of 2 m. Experiments were carried out using air, water (or CMC solution), and polystyrene particles. Mixing in the liquid phase was assessed by the tracer-response technique and fast conductivity measurements.
It was found that the flow pattern in an airlift reactor with net draft tube was similar to that in bubble columns instead of traditional airlift reactor. The mixing time decreased and the axial dispersion coefficient increased with increasing net mesh number. Moreover, the axial dispersion coefficient increased while rising superficial gas velocity except the transition from bubbly to churn-turbulent flow regime. The better diameter ratio of draft tube to column was 0.6, and the reactor with higher draft tube had better mixing performance. However, the top section had slight influence on liquid mixing, and the dispersion coefficient didn’t change with the reactor. Furthermore, adding solids and increasing liquid viscosity would enhance the mixing efficiency. In addition, the correlation between dispersion coefficient and these variables was established and the observed values were in agreement with the calculated values with a deviation of 30 %.
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