Background: Solid suspension in liquids is an important unit operation generally encountered
in the process industry. In the present work solid−liquid suspensions are explored in an
agitated vessel with different liquids using two radial impellers namely Rushton turbine and straight
blade; two axial impellers namely pitched blade turbine and A320. The critical impeller speed (Njs)
at which all solid particles get suspended and the relevant power requirements (Pjs) are evaluated.
The effect liquid viscosity on these two parameters is investigated.
Conclusion: Results show that critical impeller speed and power consumption decreases as
liquid viscosity increases. The critical impeller speed was found to be highest for straight
blade impeller and lowest for pitched blade turbine. A320 impeller showed strong dependence
of viscosity on critical impeller speed. In addition, the power consumption was found to
be least for A320 impeller among the impellers investigated in this study.
Keywords: Impeller type, impeller clearance, liquid viscosity, solid suspension, critical impeller speed,
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