Evaluation of the hydrodynamic behavior of powders of varying cohesivity in a fluidized bed using the FT4 Powder Rheometer

The hydrodynamic properties of surface treated powders were investigated using the FT4 Powder Rheometer® through aeration studies. Powders of varying Sauter mean diameter were selected to reveal the effect of intrinsic cohesion on the ability to fluidize the powder. The studies were used to explore the following concepts: (1) repeatability of the measurements, (2) ability to discern powder column expansion, (3) estimation of the minimum fluidization velocity based on pressure drops, and (4) evaluation of the various stages of fluidization. Surface treatment showed significant improvement and uniform, particulate fluidization for the larger particle sizes. Estimations of minimum fluidization velocity in an agitated environment were deduced from pressure drop curves and showed significant differences for the smaller particles sizes, however converged towards the theoretical value for the larger particle sizes. The various stages of powder column fluidization from fixed bed to entrainment were also evident through experimentally determined bed expansion curves.