Influence of the physicochemical properties on the growth of solid particles by granulation in fluidized bed

Abstract

This work aims at investigating the effects of the physicochemical properties, such as the viscosity and the wettability of a granulating liquid on solid particles surfaces, on the agglomeration kinetics of solid particles in a fluidized bed. A series of batch experiments are carried out in a fluidized bed granulator at 50°C with 2 kg of solid particles. The use of solutions of Sodium CarboxyMethylCellulose (CMC) as binder with different concentrations leads to the study of the viscosity of the solution. The effect of the surface tension is investigated by adding different concentrations of a nonionic surfactant to the binding solution. The effect of the contact angle is then studied by using nonhydrophobic or partly or totally hydrophobic particles. The growth of agglomerates appears to be favored when the interfacial tension increases and the contact angle decreases. The viscosity of the solution has less effect than the interfacial parameters. The results point out that the dominant forces in the granulation process are the capillary forces. When an aqueous solution is pulverized into a fluidized bed containing hydrophobic particles, most of the binder is elutriated and collected in the cyclone. This shows that the main mechanism is in this case spray drying. As this process occurs at low temperature, it is useful for drying thermosensitive solutions.