Powder flow patterns

Powder flow patterns in wet granulation can be studied using positron emission particle tracking. Eventually, this and similar techniques can be used to validate various mathematical and statistical models of the process. 

Powder Flow Patterns and Scaling of Mixing Powder flow properties have a significant impact on high-shear mixing, particularly... 

Scale-up and Operation As discussed above, scale-up of high-shear mixers is difficult due to complex powder flow patterns, wide variations in shear rates among mixers, and competition among granulation rate processes. Ideally, the following should be preserved with scale-up. 

Powder flow in high-shear mixers is not fluidized and powder flow patterns are much harder to predict than in a fluidized bed. 

Relative All height is also often varied with scale. This often reflects the small-size batches required for early-stage clinical trials and the desire to maximize production rate (by maximizing batch size) at full scale. Varying relative fill height is very dangerous, as it can have a major impact on powder flow patterns. 

Thus, to maintain a similar powder flow pattern during scale-up, the Froude number should be kept constant, i.e.. 

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