A study on dynamic stability of medium in air dense medium fluidised bed separator

Abstract

The air dense medium separation uses a dense fluidised medium of air and fine magnetite particles for beneficiation of any material. Depending on the differences in the density of heavier and lighter solids with respect to the density of the medium, separation takes place. For dry separation, creating and sustaining the air dense medium is a complex process which requires intensive investigation. The dynamic stability of the medium plays the important role in the sharpness of the separation and the system operates under particulate fluidisation system. The different geometrical dimension of laboratory models were fabricated for this study. The magnetite powder below 45-micron size was used as solid medium. The compressed air at different airflow rate was used as fluid medium. Dense medium was created by suspending solid particles in an upward direction of flow of air. The study on dynamic stability of medium was determined by the values of the following physical parameters i.e., harmonic mean diameter of particles size distribution, true and bulk density of magnetite powder, porosity of the bed, pressure drops at the air distributor and bed density of the fluidised bed. Based on experimental data, four dimensionless groups i.e., Froude number, Reynolds number, ratio of density of fluid and solids and aspect ratio of the system are used to characterise the quality of fluidisation.