Magnetically Stabilized Fluidized Beds for Solids Separation by Density

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Abstract
Systems for the dry separation of solids by density difference are described. They consist of a magnetically stabilized fluidized bed (MSB) as a host medium in which heavy solids sink and light solids float. The magnetic stabilization produces a fluidized medium with the absence of gas bubbling and thus enhances the separations efficiency by preventing remixing of the feed solids to be separated. The MSB can be maintained with an apparent bulk density between that of solids in a mixture to be separated by adjusting the gas fluidization velocity. Several experiments have been conducted using both batch and continuous MSBs to separate a solids mixture consisting of coal and limestone. In the continuously operated experiments using this binary feed, recoveries of 90% of the feed solids at over 90% purity were obtained. Preferred operating conditions for the MSB are discussed which result in minimizing the effects of bed yield stress and viscosity on the separations efficiency. Configurations for the separation of multicomponent feeds are also proposed.