Particle transport and separation in inclined channels subject to centrifugal forces

A novel experimental system was established in order to investigate the effect of centrifugal forces on the hydrodynamic transport of particles through planar channels inclined at 70° to the axis of rotation. The device, consisting of a fluidized bed housing attached to a system of parallel inclined channels, was mounted inside a 2 m diameter centrifuge. Fluidization water was directed to the outer periphery of the system, entering the base of the housing. The water then flowed in a direction towards the centre of the centrifuge, through an open chamber 150 mm long, and then through the system of planar channels, 160 mm long. The channels had a perpendicular spacing of z=1 mm. The water then emerged via an overflow weir, 400 mm from the centre of the centrifuge. Semi-batch elutriation experiments were conducted on a silica feed, 0–0.060 mm in diameter, achieving separations defined in terms of the particle diameter, d, and centrifugal acceleration gG, where g is the magnitude of the acceleration due to gravity. The throughput advantage achieved using G=73 over a conventional fluidized bed with G=1 ranged from 845 to 3094. The extraordinary results were in reasonable agreement with the theoretical throughput advantage described in the paper. It was concluded that the hydrodynamic benefits of the inclined channels and the centrifugal force multiplied. The centrifugal force produced further synergy with the system hydrodynamics, resulting in the suppression of the effects of particle size, and hence a powerful separation on the basis of the particle density. This physical arrangement offers the potential to separate ultrafine particles in coal and mineral processing on the basis of density, offering an alternative to flotation.

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► We incorporate a fluidized bed with inclined plates in a centrifuge.
► Capacity advantage arising from the G forces and plates multiply.
► Data confirm the high capacity of the elutriator.
► The high shear rate in the inclined channels promotes inertial lift at high G forces.
► System provides a powerful basis for separating particles by density.