Segregation and Process Features in a Teeter Bed Separator as Revealed by High Speed Videography and Image Processing

Abstract

Gravity concentration in a liquid fluidized bed floatex density separator (FDS) was investigated through high speed videography and image analysis. Process performance in terms of yield and grade of the product for fine coal beneficiation in the FDS was established experimentally. The feed coal (-1.18 mm) with 36% ash was enriched to 24% ash at a mass yield of 65%. Coarsest underflow with a d50 of 700 µm was obtained at 5.8 kPa bed pressure, 120 kg/h feed rate and 12 lpm teeter water flow. The lowest SG50 of 1.62 was obtained at 5.4 kPa, 15 lpm and 80 kg/h. At 9 lpm water flow, steady state was achieved in 400 sec when the voidage and suspension density distributions became constant. From the suspension density distribution, the SG50, 1.69 under this set of conditions, was estimated with reasonable accuracy. Increase in teeter water was shown to increase the time required for attaining steady state. It was established that particle size distribution at the bottom of the bed in the column offers a good indication of the separation performance. The influences of the operating variables on the axial steady state profile of the suspension density and voidage were also established. Image analysis is shown to be quite useful in collecting quantitative transient and steady state data that may be difficult to obtain otherwise. The process performances were adequately described using such transient and steady state observations.