Fluidization of coated cohesive powders

According to the Geldart classification, group C powders are too cohesive to fluidize because of the strong inter-particle adhesion forces. In previous work by our group, it was found that dry particle coating can be used to deposit a very small amount of nano-sized particles with high degree of precision onto group C cohesive particles to significantly improve their flowability. In this work, dry particle coating is utilized to improve the fluidizability of cohesive group C powders. A new model taking account into the effect of Surface Area Coverage (SAC) of the coated nano-sized particles is proposed to examine the effect of coating on adhesion of cohesive powders. A series of experiments are performed to investigate the improvement in the fluidizability of group C powders (e.g., cornstarch and aluminum) as a result of dry particle coating by a small amount of nano-sized particles. The effect of various parameters such as, surface area coverage (SAC), guest particle size and host particle size are systematically investigated, indicating that each parameter plays an important role on the fluidization behavior of cohesive powders. The study shows that dry particle coating can improve the fluidizability of cohesive powders dramatically and it appears that such a coating can transform the behavior of group C powders to that of group A powders.