Analysis of the fluidization behavior and application of a novel spouted bed apparatus for spray granulation and coating

Spouted beds are well known for their good mixing of the solid phase and for their intensive heat and mass transfers between the fluid phase and the solid phase. Nearly isothermal conditions are enabled which is of advantage for the treatment of granular solid materials in granulation, agglomeration or coating processes. In this work the hydrodynamic behaviour of a novel spouted bed apparatus with two horizontal and slit-shaped gas inlets is investigated by high-frequency recordings of the gas phase pressure fluctuations over the entire bed. The hydrodynamic stable operation domain, which is of importance for operating the apparatus, will be identified and depicted in the Re-G-Ar-diagram by Mitev [1]. Another focus of this work is the simulation of the spouting process by application of a continuum approach in FLUENT 6.2. The effect of the frictional stresses on the hydrodynamic behaviour is examined by performing simulations with and without consideration of friction. The angle of internal friction fi in Schaeffer`s [10] model will be varied and the simulation results will be compared with experiments. It was found that the influence of friction is not very big by application of the quite simple and empirical frictional viscosity model by Schaeffer [10] basing on soil mechanical principles. Also the simulation results under negligence of friction were similar to those under consideration of friction. Another part of this work is the industrial application of the novel spouted bed in granulation and coating processes. Compared to classical fluidized beds, a much narrower particle size distribution, a higher yield and a higher product quality was obtained in the novel spouted bed