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

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 (gamma-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 anti heat and mass balances is presented. Simulations performed using the obtained empirical correlation are in good agreement with experimental data. (C) 2014 Elsevier B.V. All rights reserved.