Scale-Up of Fluidized Bed Granulators

Particle growth in a fluidized bed is closely related to the particle mixing and the flow pattern in the bed. This dictates that the hydrodynamics of the scaled bed should be the same as the small imit, i.e., hydrodynamic similarity. Basic fluidized bed hydrodynamics are described in Chapter 9. 

the excess gas velocity u — M f and the bed height L are the key process parameters that control bubbling behavior in the bed. 

Several rules exist for scaling up a bubbling fluidized bed under the condition of hydrodynamic similarity. Fitzgerald and Crane (15) proposed that the following dimensionless numbers be kept constant during scale-up  

In this approach, experiments on the smaller scale are performed with model materials, i.e., model gas (different from the larger-scale one) and model solid particles (different particle density, size, and size distribution). For readers interested in following Fitzgerald s scale-up rules, a detailed calculation procedure can be found in Kunii and Levenspiel s book (13), illustrated with an example. 

In a series of publications, Glicksman et al. (16-18) divided the scale-up into two regimes, namely, inertia-dominated and viscous-dominated flow regimes. In viscous-dominated flow regime, where particle Reynolds number based on fluid density is 4, i.e., when, the (dpupa/p 4, dimensionless numbers that need to be kept constant are 

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