DESCRIPTION OF AGGLOMERATE GROWTH

Wet agglomeration processes have predominantly been investigated by ch anging operation variables of process-scale experiments. So far, most fundamental work concentrated on the strength of the liquid bonds in t he agglomerate and its relation to the process. Previous studies on th e relationship between droplet size and agglomerate size in fluid bed agglomeration indicated that, besides agglomerate strength, liquid dis tribution determines the agglomerate properties to a large extent. Thi s paper focuses on the mechanism of growth of a single agglomerate ori ginating from one droplet of binder liquid. A model is introduced whic h describes agglomerate growth as a function of time. We discern two s tages of growth of an agglomerate. Initially, fast growth takes I,lace by wetting of the powder particles by a droplet, which result in the formation of an initial agglomerate. This stage of fast growth is foll owed by a second stage of slower growth, which results from drainage o f binder liquid from the initial agglomerate to the outer layers of th e growing agglomerate. This model predicts agglomerate growth and the final agglomerate size by taking into account the particle sie distrib ution, the viscosity, the surface tension, the contact angle, the poro sity, the wetting saturation and the residual saturation. Experimental results were in good agreement with the model. (C) 1998 Elsevier Scie nce S.A. All rights reserved.