Entrainment behaviour of high-density Geldart A powders with different shapes

Atomised and milled Ferrosilicon with average particle diameters of 38 and 50 µm respectively were fluidised with air at ambient conditions. The entrainment rate of the more spherical atomised particles was on average six times that of the irregularly shaped milled particles over the range of superficial velocities investigated. In an attempt to decouple the effect of particle size from shape, the bed was divided into theoretically isolated bins based on the distributions of particle sizes. This indicated that the atomised particles had a higher entrainment rate for particles smaller than approximately 25 µm whereas the opposite was true for particles greater than this size. None of the entrainment correlations investigated was able to predict the switch in entrainment behaviour as a function of particle sphericity and diameter. Furthermore, the traditional critical particle diameter associated with cohesive Geldart A particles was not observed for either of the two particle shapes. It is therefore concluded that neither the hydrodynamic nor Van der Waals forces acting on the particles can adequately explain the entrainment rate behaviour of differently shaped high-density Geldart A particles.

Atomised and milled Ferrosilicon particles were fluidised in air at ambient conditions. The spherical atomised particles had an average entrainment rate of six times higher than the irregular milled particles. It was concluded that neither the hydrodynamic nor Van der Waals forces can adequately explain these results.Figure optionsDownload as PowerPoint slideFigure 1: Comparison of the entrainment rates for the different solid mixtures. Solid lines represent the average values for the individual mixtures