Particulate processes involve different kinetic processes such as formation of nuclei, their subsequent growth and breakage. In addition, external product classification can play a significant role. A reliable prediction and thorough understanding of potential sources for instability is not only of scientific interest but also an important issue for better process design and process control. The application of these nonlinear dynamics is concerned with fluidized bed spray granulation. Self-sustained oscillations may rise in processes with external product classification. Therefore, focus of this work is on process stability which can be influenced by classifying, milling and recycling of particles and by the production of internal and external seeds. First a brief introduction to the model is given, that couples the particle population state with thermodynamic-, fluiddynamic- and granulation process for a unit with non-classifying product discharge and a screening and milling unit in the seed recycle and builds the core of the software package AVA (R) FBSim (R), used for the experiments. (c) 2005 Elsevier Ltd. All rights reserved.