Kinetics of balling and granulation

The experimental results of Capes and Danckwerts (C6) and Kanetkar (K1), using a balling drum and a disk granulator, respectively, have shown that the thickness of the snowballed layer is approximately independent of the initial size of the seed pellet. It then follows that the rate of pick up of the loose particulate material is proportional to the surface area of the granule hence, 

Inspection of this equation shows that in the course of the snowballing growth the size distribution curves at various times are simply shifted toward the right on the pellet size scale without any change in their shape, as demonstrated by Capes (C2) for sand pellets snowballed in a pan granulator (Fig. 13). 

For modeling a continuous pelletizer, it is advantageous to formulate the snowballing kinetics in the well-known continuity equation for the pellet species 

Kapur (K3) has formulated a set of kinetic equations for the agglomerate population and crushed material balance as follows  

Clearly, /t0(f) is the total number and is the total volume of the agglomerates in the charge. The latter is approximately independent of time in view of the quasi-steady-state assumption in Eq. (46). Kapur (K3) has shown that an asymptotic similarity solution to Eq. (47) exists in the following form  

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Section V. Kinetics of Balling and Granulation Ouchiyama, N, and Tanaka, T., The probability of coalescence in granulation kinetics, Ind. Eng. Chem., Process Des. Develop. 14, 286 (1975). 

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