Influence of zone formation on stability of continuous fluidized bed layering granulation with external product classification

• Stability of fluidized bed spray granulation processes is influenced by zone formation.
• Stability was studied for a wide range of possible process configurations and operating conditions.
• The corresponding model was formulated and analyzed theoretically.
• Results were validated by dynamic simulation.

Continuous fluidized bed layering granulation with external product classification and a sieve-mill cycle can show instability in the form of self-sustained nonlinear oscillations of the particle size distribution. In the present study, the stability and bifurcation analysis of this process is presented. The underlying process models explicitly account for compartmentalization of the fluidized bed into a granulation and a drying zone, which is an important feature of many technical processes. Implications for plant operations are discussed with the help of stability diagrams as a function of zone size, residence time within different zones, the addition of external seeds and particular properties of the sieve-mill cycle.

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