The consequences of granulate heterogeneity towards breakage and attrition upon fluid-bed drying.

High-shear granulated lactose granulates were dried in a fluid-bed dryer at various conditions. Granules were characterized by water content and size analysis. It is shown that the drying process is very dynamic in terms of growth and breakage phenomena. Granular size heterogeneity, composition and water content determine the granule behavior upon drying. Large granules consist of small primary particles and contain more water than small granules that consist of large primary particles. This differentiates the drying rate and extent of size reduction of the different granule size classes. The results enable a critical evaluation of process control and process monitoring. Understanding of granule behavior and continuous monitoring of the fluid-bed drying process enables process and product optimization.