Desliming of dense minerals in fluidized beds

This paper applies Drift Flux theory for the first time to explore the relationship between the liquid and solids flow through fluidized beds in the context of desliming of dense minerals. At low solids fluxes the process is not flux curve constrained. Here continuity considerations indicate the net liquid flux through the lower bed is upwards, ideal for the removal of slimes from the underflow product. Moreover, the liquid split to the underflow is also lower, further reducing the slimes content of the underflow. At higher solids fluxes the net liquid flux becomes downwards and eventually the system becomes flux curve constrained. Under these circumstances slimes entrainment to the underflow increases significantly. In order to operate at these higher solids fluxes, and achieve efficient desliming, Split Fluidization should be used. Here additional fluidization liquid is added at a higher elevation, producing a net liquid flux in the upwards direction through the zone above the Split Fluidization entrance level. Desliming experiments covering a range of solids fluxes were conducted to investigate the effects of increasing solids flux and Split Fluidization. This study shows that a system of parallel inclined channels, a key feature of the Reflux Classifier, permits the introduction of this additional liquid while preventing the ultra fine product from being entrained to the overflow reject stream, thus permitting the efficient removal of slimes. Experiments were conducted using an iron ore feed with particles smaller than 0.50 mm in diameter. Efficient desliming at a relatively high solids feed flux of 20 t/m²h was achieved, but to efficiently deslime at 40 t/m²h significant Split Fluidization was found to be essential.