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Title: A comparative study of impeller performance in solid-gas-liquid mixing
Author: Ibrahim, Shaliza Binti
Awarding Body: University of Birmingham
Current Institution: University of Birmingham
Date of Award: 1991
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The mixing characteristics of the Chemineer HE-3, the Lightning A310 and the Ekato InterMIGs impellers have been compared to the 6-blade Rushton turbine and mixed-flow impellers pumping upward (6MFU) and downward (6MFD) in one, two and three phase systems, at 0.29 m cylindrical vessel diameter. The unaerated power number of the 3-blade axial flow HE-3 and A310 is about 0.3 in the high Reynolds number regime (Re > 1000), and for InterMIGs Po is 0.65. These values are low compared to those for the 6DT (4.6) and 6MFU/D (~1.5-1.6). The impeller clearance from the base influences the value of Po, but the liquid viscosity plays a role in determining the extent of the effect from the clearance. The InterMIGs did not exhibi t any effect of clearance on the Po over the whole range of Re studied. Solids distribution in solid-liquid systems is directly governed by the flow of liquid in the agitated vessel. Hence, the clearance and liquid viscosity also have important effects on solid suspension. Generally, solids are more easily suspended at a low impeller clearance from the base and at low viscosities. The former, due to less energy loss from liquid entrainment before the solids are reached, and the latter, due to less drag in the flow and more turbulence. However, too low a clearance can be disadvantageous for certain impeller geometries due to enhanced accumulation; while a higher liquid drag may be useful for maintaining solids in suspension. Another factor studied was the base geometry, and the modified cone-and-flllet geometry was found to be more efficient for eliminating sedimentations on the base. The axial flow impellers at the optimum D/T were the most energy efficient to use for solids suspension. The optimum D/T is 0.35 to 0.39 at 0.001 and 0.01 Pa s. At 0.1 Pa s and higher, the optimum ratio is higher.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available