Improvement of bulk flow properties of powders

Air-assisted gravity discharge is considered as a valuable technique for improving flow properties of powders. This work aims at elucidating the complex phenomena occurring in aerated discharge of solids, with special reference to conditions intermediate between pure gravity flow and efflux from fluidized beds. Experiments have been carried out on different fine materials of different cohesiveness. A progressive transition from gravity flow to aerated gravity flow and to fluid-bed discharge has been detected. Experimental results are compared with existing correlations. Discrepancies detected are related to the relaxation energy of the particle structure.