February 16, 2005

Knowlton, T.M., S.B.R. Karri, A. Issangya, Powder Technology 150 (2005) 72-77.


The scale-up of fluidized beds is not an exact science. However, using proven techniques based on experience and mathematical and/or design models can minimize risk and uncertainty when scaling up fluidized beds. Scaling, which maintains that certain dimensionless groups be matched in different sized units in order for hydrodynamic similarity to be achieved, is different than scale-up, and generally can not be applied to pilot plants used for scale-up. Scaling is typically more useful to be applied to cold model studies that can be used to improve the operation of an existing plant. Deep fluidized beds of Group A materials can cause significant gas bypassing leading to poor gas-solids contacting. Because commercial beds are generally deeper than beds used in pilot plants, care must be taken to ensure that beds that do not exhibit gas  bypassing in smaller units, do not have gas bypassing in commercial systems.