| Description |
Specific gravity washability curves used in the coal industry to define the theoretical gravity separation efficiency can be used in the same way for evaluation of preconcentration operations in the metal mining industry. These theoretical metal recovery/gangue rejection curves, which establish the maximum in gravity separation efficiency, can be determined from 3D image analysis by high resolution X-ray computed tomography (HRXCT) rather than by sink-float analysis using heavy liquid fractionation. In this way, the tedious, time-consuming, and toxic use of heavy liquids for laboratory sink-float analysis is avoided In this thesis research, the low-grade sulfide ores samples, Cadia and Ballarat samples (1.7x1.18 mm) (sulfide grade ~1%) received from mines in Western Australia (as a part of AMIRA P420F project) were scanned using HRXCT and the 3D images were reconstructed. The 3D image data were then analyzed using image processing software to obtain mineral composition analysis of each particle in the packed particle bed for each sample. Further, theoretical mineral recovery/gangue rejection curves for gravity preconcentration of the Cadia and Ballarat samples (1.7x1.18 mm) were obtained using the mineral composition analysis data. In order to evaluate the efficiency of gangue mineral rejection in dense media cyclone experiments for the Cadia low grade sulfide ore, results were compared to the theoretical HRXCT recovery/rejection curves. It was found that an excellent separation of the Cadia sample by the dense media cyclone was achieved, close to that expected from HRXCT analysis. Finally, to understand the nature of the dense media cyclone separation, the grain size distribution of the sulfide minerals phases was determined. It was found that the pyrite grains were finely dispersed in the gangue mineral phase of the Cadia samples. In this way the lower recovery of pyrite, when compared to the recovery of other sulfide minerals, can be explained. |
