No abstract available. / Thesis (Ph.D.)-University of Natal, 1975.

While the significant effect that the froth phase has on the performance of a flotation operation has recently been widely recognised, little work has been published which promotes an understanding of the physical processes occurring in the froth phase. A more intimate understanding of these processes and their relative importance and interactions would lead to a more rational design of froth chambers and froth removal methods, with resultant improvements in flotation plant performance. In pursuit of this understanding the following investigations were performed: (1) In a specially designed cell the variation of mineral grade with height above the froth-slurry interface - as affected by gas rate, frother concentration, the presence of froth baffles (to minimise mixing) and final product removal rate - was measured. A mathematical model was formulated to assist in the interpretation of this data. (2) The residence time distribution of a 2-phase froth (air and water without solid particles) was measured as a function of froth height, gas rate and frother concentration. Small polystyrene balls were used as a tracer. The results were interpreted using two theoretical models: (a) a streamline model which involved the solution of the 2 - dimensional Laplace equation for frictionless flow of froth in the froth chamber; (b) a semi-phenomenological model which relates the froth residence time distribution to cell dimensions, gas rate and froth stability. On the basis of insights gained in these investigations, a number of objectives which should be met by froth removal methods were formulated: (1) froth removal efficiency should be maximised, i.e. there should be no stagnant zones in the froth; (2) froth stability should be optimised; (3) the minimum residence time of froth elements in the froth phase should be maximised. One novel method of froth removal was designed, and this and a number of other methods of froth removal were compared experimentally. It was found that substantial improvement in flotation performance could be obtained by (1) sprinkling the froth with water, which removed entrained particles and improved froth stability; (2) inserting a baffle in the froth phase near the concentrate weir which increased the minimum residence time of a froth element in the froth phase, thereby improving the drainage of entrained particles from the froth; and (3) placing a froth scraper near the back of the cell, thus ensuring that no stagnant froth zones developed. / Thesis (Ph.D.)-University of Natal, Durban, 1979.

When designing or optimizing flotation circuits in mineral processing plants, it is necessary to have accurate values of the flotation kinetics to ensure the correct mass pulls and material balances on the plant. Previous studies have shown that rate constants measured by single cell batch testing can cause a shift in the recovery—grade curve. The shift in the recovery—grade curve is the result of poor separation in conventional laboratory flotation devices. This project involved the development and modelling of a flotation device that provides a better separation than a conventional batch flotation cell. The device is called a semi—batch flotation apparatus (SBFA) because it simulates the operations of a pilot plant in a laboratory environment. It also provides dynamic data which facilitates the evaluation of model parameters. The SBFA tested a synthetic ore made from limestone, talc and silica. The synthetic ore was used as it was economical and easy to analyze. The results from the SBFA were compared to results obtained from conventional batch flotation tests; by using recovery—grade curves to assess the degree of separation achieved from both devices. The SBFA separated the limestone from the gangue (silica and talc) much better than the batch tests. For instance the final grade for a concentrate obtained from a single cell batch test was 20 % limestone while the final grade for a concentrate obtained from the SBFA was between 40 % and 70 % limestone. The improvements in separation can be attributed to the multistage design of the SBFA which has a pulp recycle between the stages. A model has been developed for the SBFA. The model fitted the experimental data well with a correlation coefficient close to unity. The cumulative recoveries predicted from the SBFA model was compared to the actual cumulative recoveries, by using a global set of parameters (&2 and RMAX)- The investigation showed that the model had problems in fitting the data for the early periods of the experiments because of the complex interaction between the stages in the SBFA. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2008.

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This study was carried out to investigate the flotation and leaching behaviour of bornite and chalcopyrite when they are together as principal sulphide minerals. Bench scale flotation performance was examined both in the absence and in the presence of a collector, PEX. In the absence of a collector, chalcopyrite floated significantly better than bornite. In the presence of a collector there was a reversal in selectivity, with bornite recovery presiding over that of chalcopyrite. Chalcopyrite recovery was marginally improved from the collectorless flotation case while bornite experienced vastly improved recoveries in the presence of a collector to surpass the recovery of chalcopyrite. The gap between floatability of bornite and chalcopyrite became more prominent under oxygen-deficient conditions induced by nitrogen flotation, which significantly decreased flotation rate of both minerals, but the floatability of bornite was still much higher than that of chalcopyrite. It is suggested that galvanic interactions promote the interaction of bornite with a collector while retarding interactions of chalcopyrite with the collector. Collectorless flotation of chalcopyrite observed under oxidizing conditions using air is thought to be prevalent even in the presence of a collector obscuring the selectivity of the process. Leaching of the mixtures of bornite and chalcopyrite at mass ratios of 1:1, 1:3 and 3:1 are performed under various conditions to investigate the possible changes in leaching behaviour in relation to galvanic interactions. Leaching at 90°C in the presence of 0.1 M ferric ions in 0.1 M sulphuric acid provided the best results with 90% copper extraction from the mixtures in 6 hours. Observed copper extractions suggested increased copper extraction from chalcopyrite with this approach. The introduction of cupric and ferrous ions into solution, together with variation of solution potential made it difficult to assess in details on the effects of galvanic interactions due to these parameters being known to improve copper extraction from chalcopyrite. Galvanic interactions together with the presence of cupric ions were held mainly responsible for the increased copper extraction. / Thesis (Master, Mining Engineering) -- Queen's University, 2014-01-11 00:25:35.365