Long chain alkyl pyridinium salts have been used as collectors for the flotation of chalcopyrite and copper-activated sphalerite. For the ores tested in this study, these reagents have demonstrated improved selectivity and recovery in comparison to conventional xanthates. The best flotation results, in terms of both grade and recovery, were achieved with cetyl pyridinium chloride (CpCl). A distinct advantage of using CpCl instead of a conventional xanthate, such as sodium isopropyl xanthate (NaIpX), is that the kinetics of flotation are much faster. This may be explained by the reduction in the negative ζ-potential of the sulfide mineral upon adsorption of cetyl pyridinium ions, which, in turn, minimizes the electrostatic component of the disjoining pressure of the wetting film. CpCl has also demonstrated a remarkable selectivity despite the fact that both chalcopyrite and the silicious gangue minerals present in the ore are negatively charged. This may be explained by the premise that cetyl pyridinium ions adsorb more strongly on chalcopyrite than on the gangue. Analysis of the adsorption isotherms established for chalcopyrite and quartz supports this view. Several possible mechanisms have been suggested to explain the 'high affinity' type of adsorption observed in the CpCl-chalcopyrite system. / Master of Science

No description available.

No description available.

Froth flotation has been used to concentrate minerals for over a century (Finch and Dobby, 1990) and it is essential for the economical recovery of metals which are present at low concentrations. The traditional flotation cell consists of a stirred tank incorporating air injection. In recent decades columns have appeared to offer advantages for platinum flotation. This project is a comparative study of the use of column and mechanical cells as cleaners for the flotation of an UG-2 (Upper Group 2) platinum ore. A laboratory column cell, 1.8 m high and 60 mm in diameter, was constructed to have the same volume as a conventional 5L Denver mechanical cell. Batch cleaning tests were used to compare the two types of cells, while varying the depressant dosage and conditioning technique. The performance of the column cell when the pulp was recycled was also compared. Finally the effect of doubling the column height, whilst maintaining the same mass percent of solids as in the original column, was investigated. Samples were subjected to acid digestion to determine Copper (Cu) and Nickel (Ni) recovery as an indicator of platinum recovery. Platinum Group Metals and Gold (PGM+Au) assays were performed on samples from a final series of tests that used a different but similar ore sample. The investigations showed that the mechanical cell performed better than the column. The PGM grade in the mechanical cell was 6.5ppm higher for a common recovery of 80% PGM in both cells. The performance of the column cell was only marginally improved when the pulp was recycled. Mass recovery data indicated that the column cell required less depressant for reducing the mass recovery. The corresponding grade recovery curves showed that for a 10 g/t depressant addition, the grade of the concentrate produced in the column cell doubled whilst that of the mechanical cell revealed no significant change. It was suggested in literature (Whitney and Yan, 1996) that the depressant was more effective in a column cell, due to the absence of agitation by an impeller. Platinum recovery data from the final series did not confirm the interesting trend observed with the preliminary tests (Cu/Ni) at a low depressant dosage (10g/t), but marginal improvements were noted at higher dosages. The effect of agitation during conditioning with depressant was also investigated. Gentle conditioning of the depressant, prior to column flotation, resulted in a higher grade and recovery of PGM as compared to conditioning by means of the recirculation pump. The PGM grade when gentle conditioning was employed was 9 ppm higher for a common PGM recovery of 80% for both conditioning techniques. Finally it was found that increasing the column height improved the grade-recovery relationship. The PGM grade obtained by the longer column was 8 ppm higher for a common PGM recovery of 75% in both columns. The performance of the longer column was similar to that of the mechanical cell. Tests were also conducted at a platinum concentrator, to compare the performance of a 378L pilot-plant column (5.5m high and 0.3m diameter), to that of a pilot-plant consisting of six mechanical cells. The pilot test rig of mechanical cells (FCTR) achieved a significantly better recovery than a pilot column. However, by decreasing the column feed flowrate and thereby increasing the residence time, a substantial improvement in the PGM grade and recovery was obtained by the column cell. / Thesis (M.Sc.Eng.)--University of KwaZulu-Natal, Durban, 2012.

A dissertation submitted to the Faculty of Engineering, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science in Engineering Johannesburg, 1992 / Modern methods of mechanised mining and the necessity for the utilization of total reserves have caused the inclusion of more and more impurities in run of mine coal. This fact, together with the limited supply of naturally clean coal fCI gasification, liquefaction and metallurgical purposes, has made some Iorm l){ beneficiation obligatory at many mines not only in South Africa but also in many other countries. One of the South African Coalfields, Waterherg, contains the continent's largest reserves (approximately 46% of South African known reserves). At the Grootegeluk Coal Mine, approximately 15 m tons of coal per annum are mined by opencast methods. The coal is characterised by containing a high proportion of reactive macerals. The Waterberg Coalfield is currently supplying coal for coke manufacture and middlings for power generation. This coal could also be used for other markets, as Waterberg coal is low in oxygen, contains up to 30% volatile matter. Because it contains 90% vitrinite, it is suitable for direct liquefaction, and possibly coal-water mixtures. However the yield of coal suitable for coking or liquefaction (approx 10% ash) is only 12%, with another 24% of 35% ash coal, currently used for power generation. These yields render mining generally uneconomical if making a simple product. The objective of this project is to ascertain whether the yields of washed coal from the Waterberg Coalfield might be increased by using comminution. Thereafter appropriate beneficiation techniques might be employed on different size fractions. Liberation, float and sink, froth flotation and oil agglomeration processes were examined to identify the best way of treating the coal. Work was carried out on the existing clean coal, middlings and discard fractions. The major objective was to optimise the yield of 10-15% ash coal.The results of the experiment indicate that it is possible to obtain low ash coal from middlings, and middlings from discard for power station. The capital and operating costs for improved new plants are calculated by using available factorised data. The results of experiments on both middlings and discards indicate that yields are significantly higher than those currently obtained, but the cost of obtaining such enhanced yields can be too high for normal commercial application. / MT2017

We present an approach to model the dynamic of a copper flotation process. The conventional approach of system identification is applied to model the dynamics. In this research, experiments are performed to collect process data of determined input and output variables. It is followed by data pre-processing to handle outliers and to remove high frequency disturbances. Simulation and validation responses of linear estimated models, which captured the dynamic of the process, are presented. The long term goal is to use estimated models to design a models-based control system.

No description available.

No description available.

No description available.

No description available.