Nucleation, growth and breakage phenomena in agitated wet granulation processes: a review

A regime map of granule growth behavior is proposed based on granule deformation during collision and the granule liquid content measured as the maximum pore saturation. The granule deformability on collision is represented by a deformation number, which is a ratio of granule impact energy to the plastic energy absorbed per unit strain. Granule growth regimes such as steady growth, induction, nudeation, crumb, and slurry are defined. Ttus regime map qualitatively explains the variations in granulation behavior. Laboratory drum granulation experiments were used to test the regime map. Experiments were performed in a 0.3-m-dia. drum using three sizes of glass ballotini (19, 31, and 60 μm) with water andglycerol as liquid binders. Increasing granule yield stress by decreasing particle size and increasing binder viscosity caused the system to move from steady growth to induction behavior as predicted by the regime map. Preliminary validation with literature data was also encouraging. More work, however, is required to better quantify the boundaries bet\veen different growth regimes and to investigate the effect of process agitation intensity. Tfiis regime map has great potential to help design and control granulation systems, because it is based on properties of the powder/binder system that can be measured or estimated without performing any granulation tests.

P.C. Knight

Papers

An investigation into the effects of binder viscosity on agglomeration behaviour