| Summary: | Bibliography: pages [144]-152. === The methodology was developed to characterise the complex MF2 circuit at Impala Platinum Ltd. The circuit was divided into individual units and each unit was evaluated over a period of time. The performance of each unit in terms of platinum, palladium, rhodium and chromite recoveries was determined by sampling around the unit. The changes in ore floatability characteristics were monitored by carrying out batch flotation tests on samples taken from the feed to each unit. The mixing in the units was characterised by performing residence time distribution studies on the units. The batch flotation results were modelled using a distributed rate approach. The model yielded parameters which were associated with three floatability classes, viz. a fast floating, a medium floating and, a slow floating class and a class for valuable minerals which did not float. The model was not able to discriminate between mineralogical and particle size effects on flotation rates. This would be an important prospect of a future investigation. The rate constants associated with each floatability fraction obtained from the batch flotation together with residence time distribution results were used in association with the actual recoveries from each unit. These factors were used to simulate the performance of the circuit. The same model was used for all the units and the differences in cell design as indicated by hydrodynamics, aeration rate, etc. were accounted for in the· mixing parameters and flotation rates. This procedure to simulate plant performance was successfully applied to three different circuits thus confirming its validity. The difference in the three simulated circuits was in the cleaning stages. Among other things, the simulation shows that the best ·platinum, palladium and rhodium recoveries could be obtained if the greatest cleaning capacity was situated in the secondary stage of the circuit. Although the changes in the circuit configuration could be simulated to establish the effect on the platinum, palladium and rhodium recoveries, the chromite recovery could not be simulated. This is due to the fact that chromite is mainly floated by entrainment which is not incorporated into the model. Since the chromite recovery is crucial for the design of optimum cleaning circuits in the flotation of UG-2 ore, research needs to be done to quantify the entrainment phenomenon.
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