Performance of the reflux classifier for gravity separation at full scale

The Reflux Classifier (RC) is a fluidized bed separator capable of operating at high hydraulic loadings due to the presence of parallel inclined plates within the system. When the fluidized suspension passes up through the inclined channels formed by the plates, faster settling particles segregate onto the inclined surfaces, and slide back down to the zone below, while slower settling particles pass on through. The parallel inclined plates provide for a much higher sedimentation area. This arrangement is suitable for both hydrosizing and gravity separation. At MEGS01, the results obtained for a pilot-scale study of the RC were reported [Galvin, K.P., Doroodchi, E., Callen, A.M., Lambert, N., Pratten, S.J., 2002. Pilot plant trial of the reflux classifier. Minerals Engineering, 15, 19–25]. Since then Ludowici MPE, in association with the University of Newcastle have developed the technology at the full-scale. The purpose of this paper is to provide details on the performance of the full-scale RC in the gravity separation of a coal and mineral matter feed in the size range of 0.25–2.0 mm. Historically, this feed has been processed using spirals, however, there is a strong trend now in Australia to employ fluidized bed devices, thus allowing significant changes to be made to the cut-point. The performance of the full-scale RC is described in terms of the partition curves for individual size fractions, and in terms of the yield–ash condition on the feed washability curve. It is concluded that the separation performance is equivalent to that obtained at the pilot scale.