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Influence of drying conditions on layer porosity in fluidized bed spray granulation

Rieck, C., Hoffmann, T., Bück, A., Peglow, M., Tsotsas, E.
Powder technology 2015 v.272 pp. 120-131
air, aluminum oxide, coatings, drying, fluidized beds, glass, heat, models, particle size distribution, porosity, powders, sodium benzoate, spraying, temperature
Particle coating experiments were performed in a lab-scale fluidized bed with varying process parameters, such as spraying rate and air inlet temperature, leading to different drying conditions. Porous (γ-Al2O3) and non-porous (glass) initial particles were sprayed with a sodium benzoate solution. For each experiment, the particle size distribution as well as the layer porosity was measured. The results show a dependency of the layer porosity on the drying conditions, represented by the drying potential of the fluidization gas. The obtained relationship is expressed as a linear correlation, which can be used in process models. Apart from the experimental results, a model based on population balances and heat and mass balances is presented. Simulations performed using the obtained empirical correlation are in good agreement with experimental data.