Dense-medium cyclone model based on the pivot phenomenon

Size-by-size partition curves for mineral separation in dense-medium cyclones pivot about a single characteristic point. This is defined for stable, non-segregating media by the medium density and the proportion of the medium reporting to the underflow. The pivot point departs from these values for unstable, conventional media. The phenomenon can be represented by an equation with two parameters defining pivot point coordinates and two the Ep value. On the basis of experiments in a 200 mm cyclone using ferrosilicon media, simple regression equations were developed for the separation parameters in terms of operating conditions (the coefficients were likely to be site-specific). The experiments successfully decoupled the effects of medium density and viscosity and showed that the value of Ep was independent of the former but strongly dependent on the latter. A classification model was used to predict the density of the underflow medium, a knowledge of which is required to determine the pivot parameters. The model correctly reflects the performance trends observed in dense-medium cyclone operation and has the potential to be generalised to a wide range of industrial practice.