Cloud height in solids suspension agitation

The focus of this work is the experimental determination of cloud height (the height to which solids are suspended) in an agitated slurry as a function of the agitation intensity, solid physical properties, impeller type (pitched-blade or high efficiency), and system geometry. Cloud height is not strongly dependent on impeller type or solid physical properties, except fbr extremely rapidly-settling particles. However, it is dependent on the impeller diameter to tank diameter ratio (D/T), impeller off-bottom clearance to tank diameter ratio (C/T), and solids loading. The use of multiple impellers allows solids to be suspended to higher levels in tall batches. An intermediate impeller separation leads to optimal performance in terms of the power requirement to achieve a desired cloud height. Lower impeller separations do not yield significant performance improvements over a single impeller, while higher impeller separations lead to poor performance caused by "zoning" between the impellers.