Continuous fluidized bed spray granulation (CFBSG) plays an important role in many special chemistry and food industry applications. It is used for the production of granular, high-quality, free-flowing, low-dust, and low-attrition solids with applications as particle catalysts or absorbents, waste water granules, organic or inorganic salt minerals, pharmaceuticals, etc. The process involves different kinetics such as formation of seeds, growth, breakage and agglomeration. The equations of these kinetics are usually nonlinear, and this property in combination with external product classification and recycling of particle fractions can lead to self-sustained oscillations. For large process units the cycle time is in the order of hours. During the cycle the size distribution of the granules will change periodically. This will lead to permanent fluctuations in the product quality, which is usually not desired for single product plants.

Therefore, it is crucial to know how the various process parameters affect these patterns of behavior, so that oscillations can be systematically avoided.

In this paper the theoretical study of stability and self-sustained oscillations of CFSBG is further extended by means of numerical bifurcation methods (Fig.). Granulometric stability boundaries in the parameter space were predicted. For the analysis a new mass based population balance model for fluidized bed spray granulation has been developed. In addition, only mass based interaction fluxes between the process units have been defined, so that the efficiency of the model was significantly increased. In addition, the coupling of the population balance with a heat and mass transfer model to calculate transient progressions of temperatures, humidities and of particle wetting is discussed and experimental and simulation studies are explained.

Figure: Numerical bifurcation analysis with DIVA

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