PARTICLE GROWTH IN A CONTINUOUSLY OPERATED FLUIDIZED BED GRANULATOR

Abstract

Fluidized bed spray granulation offers several advantages compared to commonly used drying processes as spray drying, e.g. free flowing dust free coarse particles with a narrow particle size distribution can be produced in a single processing step. Especially for large production units a continuous operation is desirable. Unfortunately, there is still a lack of understanding concerning the mechanisms of particle formation and growth leading to difficulties in planning and operating such continuous granulators. Hence, experiments were performed to investigate the influence of process parameters on the growth process in a continuously operated fluidized bed granulator. Furthermore, a model was developed taking into consideration the particle exchange between nozzle jet and fluidized bed as well as the wetting and drying processes. The processes inside the jet are modeled in analogy to a wet scrubber. This modeling approach predicts an increase of growth rate with particle size. The prediction is in good agreement with experimental findings.

Keywords:

• Deposition
• Fluidized bed
• Granulation
• Growth
• Nucleation

ACKNOWLEDGEMENTS

This publication is part of a research project supported by the Forschungsvereinigung für Luft- und Trocknungstechnik (FLT), sponsored by the German Ministry of Economic Affairs (AiF-Nr. 11886). We thank the Institute of Mechanical Process Engineering and Mechanics, University of Karlsruhe (TH) for placing the optical particle counter at our disposal.