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By B. Kenealy

A typical deep shaft is President Steyn No. 2 in the Free State, where 9 tonnes of ore are hoisted at about 15 metres per second from 2378 metres below surface. The skips and attachments each weigh 7 tonnes and they are connected by 43 tonnes of rope, so that to hoist the 9 tonnes of payload, a total of 66 tonnes is accelerated from stand still to 55 km/h for each cycle, using an average of 3185 kilowatts of power in the process. The cycle time for the hoisting is 3.22 minutes. The peak power consumption is 6954 kilowatts, which determines the size of the motor used. Is this the right approach? Are larger skips moving at higher speeds the answer? Is there another way?

Jan 1, 1996

By J. C. Mostert, P. N. Roberts

Electric smelting at Rustenburg Platinum Mines Limited of nickel - copper concentrates containing platinum-group metals By J. C. MOSTERT Pr. Eng.. B.Sc. (Stellenboseh). M.Sc. Met. Eng. (Fellow) and P. N. ROBERTS Pr. Eng.. B.Sc. Eng. (Rand) (Fellow) The processes involved in the smelting in an electric furnace of nickel-copper concentrates containing platinumgroup metals are described. These are concentrate drying, pelletizing, pellet drying, and flux and pellets proportioning, followed by smelting of the concentrate in a submersible-electrode electric furnace, which is discussed in more detail. The furnace matte is blown in a converter to the white-metal stage and is cast in moulds, whilst the slag is granulated, ground, and floated for recovery of valuable metals and afterwards pumped to the tailing dam.

By N. C. Joughin

Potential for the mechanization of stoping in gold mines by N. C. JOUGHIN B.Sc. Eng., Ph.D. (Rand) (Member) The basic requirements for stoping machines are identified first by examination of the mining rates and productivities attained in conventional stoping, and then by examination of a series of problem areas associated with the shape of the reefs, rockbreaking, rockhandling, and the support and design of the machines. Some of the more important machines being developed are described briefly, and their principal features are compared with the basic requirements identified in the first part of the paper. An estimate of the potential demand for the different types of machines is given.

Jan 1, 1976

By J. A. L. Napier

An essential requirement for the planning of the global capacity of a mine is a knowledge of the functional relationship between the production level and the capital expenditure necessary to establish that level. An underlying mechanism connecting capital expenditure and mine production capacity is proposed in terms of a characteristic profile of the expenditure that both precedes and succeeds production expansion. By the assignment of a representative shape to this profile, the capital expenditure of individual mines can be modelled. The empirical values describing the characteristic profile are computed for a number of gold mines, and an attempt is made to explain variations in the model coefficients from mine to mine in terms of physical parameters such as shaft depth, shaft concentration, and average rate of depth increase during the life of the mine.

Jan 1, 1981

By P. G. Henderson

Coalbrook Collieries has produced approximately 2 million tons of coal by retreat longwalling since April 1976. Strata control. support. stone intrusions. coal conveyance, and the inflow of goaf and water between the face supports have been the major operational problems experienced to date. The progressive percentage availability of the total system (moves between panels excluded) for the first three panels mined was 40 per cent. Satisfactory solutions have been evolved for these problems. and the availability in the present panel (fourth panel) has increased to approximately 60 per cent. It is envisaged that longwalling will become the most economical method of ensuring optimum heat values, greater recovery. and reduced geographic expansion. as well as safer roof conditions. at Coal brook.

Jan 1, 1980

By J. H. Bulloch

This paper describes detailed fractographic analyses of several specimens that had undergone corrosion-fatigue tests at high stress ratios in simulated pressurized water-reactor environments. The distribution and morphology of non-metallic manganese sulphide inclusions are shown to strongly affect the growth of environmentally assisted cracks (EAC), and certain features suggest that a hydrogen-assisted mechanism is responsible for the observed EAC growth. The incidence of transient EAC growth in isolated regions suggests that the critical conditions that trigger this type of growth are the 'right' local chemistry at the crack tips and imposed mechanical conditions.

Jan 1, 1987

[COUNCIL FOR 1992/93 President J.P. Hoffman President Elect Dr H. Scott-Russell Vice Presidents Senior J.A. Cruise Immediate Past President R.D. Beck Junior D.A.J. Ross-Watt Honorary Treasurer J.A. Cruise Members of Council Dr N.A. Barcza B.R. Broekman G.A. Brown P.M. Craven Prof. R.J. Dippenaar J.R. Dixon* A.A.B. Douglas B.R. Fleetwood Dr R.V.R. Handfield-Jones P.R. Janisch * co-opted P.J. Knottenbelt R.P. Mohring J.L. Nel* K.C. Owen P.D.K. Robinson K.A. van Gessel D.J. van Niekerk C.J.C.J. van Vuuren* P.M.T. White]

Jan 1, 1993

Council and Standing Committees - 1982/83 President: Prof. A. N. Brown Vice Presidents: Prof. R. P. King and J. D. Austin Honorary Treasurer: Prof. D. G. Krige Immediate Past President: G. Y. Nisbet Members of Council: B. C. Alberts, R. H. English, P. T. Fewell, C. E. Fivaz, J. S. Freer, Prof. G. G. Garrett, J. J. Geldenhuys, Dr A. K. Haines, P. N. Harris, H. E. James, Dr B. K. Loveday, Dr J. Lurie, D. G. Malan, G. Pienaar, B. E. Protheroe, Dr 0. K. H. Steffen, G. C. Thompson, Dr H. Wagner, Dr P. T. Wedepohl. Chairman, Witbank/Middelburg Branch: H. C. van Zyl.

Jan 1, 1983

By G. J. Wright, M. J. Neale

As machines become more complex and vital to our way of life, any disturbance or failure of their proper functioning tends to have serious consequences. To prevent such failures, increasing attention is being paid to techniques for the monitoring of machinery condition or 'health'. Of the many methods available, examination of the lubricant and any particles it contains forms a basis for interpretation of the conditions of operation, and the rate and severity of degradation of the moving parts, in a machine. Many techniques of wear-debris analysis, such as spectrographic oil analysis and ferography, are available indicate the composition, shape, size, and concentration of contaminants in a lubricant. This paper reviews the important aspects of wear-debris analysis as an integral component of machinery condition monitoring, and gives an insight into the selection of appropriate techniques and the information that can be obtained from each.

Jan 1, 1987

By P. Stevenson

Correlations for the critical velocity needed to hydraulically convey particles in horizontal, or near-horizontal, pipes are either explicitly dependent upon the shear stress imparted by the fluid upon the surface of the particle bed, or require a velocity and hydraulic diameter. Often such approaches are modified to account for pipe inclination by the introduction of simple factors. However, we assert that the physics that underpins the hydraulic conveying of particles in steep pipes (such as a directionally drilled oil well) is dissimilar to that which governs particle behaviour in horizontal pipes. In steeply inclined systems, a sliding sediment induces an upward counter flow and hence an autogenous contribution to the shear rate. The physics underpinning particle hydraulic conveying in steep systems is explored using the separation results of Laskovski et al.10

Jan 1, 2007

By M. A. Ford

This paper reviews the history, sources, mineralogy, extraction metallurgy, conversion, and enrichment of uranium in South Africa. Over the past 40 years extraction plants were built at 27 sites, an9.over 140 kt of uranium have been produced. Older plants have had to adapt to changing market conditions, no single technology has had the opportunity to become entrenched, and costs have been reduced to a third of those of the original flowsheet. The research efforts aimed at developing the country s nuclear raw materials have been particularly rewarding, as they have enabled South Africa to become a world leader in the extraction of uranium from low-grade ores and to develop methods for uranium enrichment and the production of nuclear fuels.

Jan 1, 1993

By A. J. Duncan, Bath M. D., E. R. Rudolph

Some factors influencing gold recovery by gravity concentration by M. D. BATH,. M.A.Se. (Met.) British Columbia (Visitor) A. J. DUNCAN,. B.Sc. (Hons.) Rhodes, M.S.A.C.I. (Visitor) E. R. RUDOLPH,* M.Se. (Eng.) Rand (Member) Recent studies have shown that the overall extraction of gold from Witwatersrand ores is increased as the proportion of gold reporting to the amalgamation circuit is increased. Testwork has therefore been carried out with a view to improving recovery by gravity concentration. In this paper, the history of gold recovery by gravity concentration is reviewed, and methods and machines at present in use are briefly described. The results of plant and laboratory tests are presented, and the limitation of existing concentrators is discussed. A pilot plant is being built for the testing of improvements to the existing concentrators and of several new devices, particularly the Reichert-cone concentrator.

By C. J. Van Niekerk

When gold plant residues are cycloned for producing a coarse product for backfilling the gold and uranium values are upgraded in the backfill product. Gravity concentration, wet high intensity magnetic separation and froth flotation were investigated as first-stage recovery processes to recover these economic values from backfill prior to placement underground. This paper addresses the recovery of values from flotation concentrates and also details the economic feasibility of a treatment route including flotation, followed by roasting of flotation concentrate to liberate gold entrapped in pyrite and reverse gold leaching of the calcine so produced.

Jan 1, 1988

By Monica M. Cole

The Empress nickel/copper deposit west of Gatooma in Rhodesia occurs within gabbro and amphibolite, disposed at the contact of a granodiorite stock (Barebottom Hill) and the surrounding greenstones of the Archaen Bulawayan System. The orebody has a pipelike form and a poor surface expression due to plantation of the area by Miocene (Africa) and later Victoria Falls erosion cycles. Barebottom Hill represents a monadnock remnant in the geomorphological surfaces while traces of the once larger Empress orebody have been removed. Limitations in soil geochemistry necessitated both studies of the vegetation ecology and the biogeochemistry of the area, both of which were anomalous. The use of geobotany was found to be restricted but biogeochemistry offers a most effective prospecting tool and was found to define the sub-outcrop of the ore-body more precisely than soil geochemistry since these methods reflect and differentiate anomalies emanating from bedrock mineralisation and those due to surface phenomena.

By G. A. Bezuidenhout

Lonmin Platinum installed a concentrated mode dual-alkali scrubber at the smelter in Marikana in 2002. The dual-alkali scrubber was the technology of choice at that time as a sulphur fixation plant, due to the perceived benefits of handling both the high SO2 concentrations of converter off-gas and the swings in SO2 concentration that are linked to Peirce-Smith operation. Owing to current and impending legislative requirements for air quality and waste, Lonmin is currently considering additions to the dual-alkali plant, but is also evaluating alternative technologies for sulphur fixation. This paper reviews the decision of Lonmin to install a concentrated mode dual-alkali scrubber and presents plant performance achieved. It also describes the important control variables and sensitivities of the plant, and the final product that is produced by the operation of the plant. The legislative requirement that drives the Lonmin technology evaluation is also discussed.

Jan 1, 2012

By K. Bryan, O&apos

A 10-year program to integrate crushing and screening models into daily flowsheet design practice has proven successful. A Circuit Analysis Program (CAP) is used worldwide to design and evaluate new and existing crushing flowsheets. To gain user acceptance of CAP and maximize effectiveness, model development, simulation flexibility, ease of use, and developing international access are key issues. These issues have been resolved effectively resulting in flowsheet simulations to assist in justifying increased capital investment. CAP is presently utilized in Canada, United States, and South Africa with intentions to expand to Europe and Asia.

Jan 1, 1987

Stochastic methods are normally invoked / used to assist with the understanding of risks, when there is uncertainty around a particular outcome. Uncertainty implies that there is a risk that the desired outcome will not be realized. Stochastics and probability theory has long held out the promise to answering this need, but has often been maligned because of its misuse. This paper takes a critical look need for Monte Carlo simulation to project risk evaluation and highlights what is considered to be the fundamental issues that should be thoughtfully considered to avoid the abuse of this technique. The upside of avoiding the abuse of this technique will be the wider acceptance by practitioners that it is a credible technique to quantify this important aspect of valuation.

Jan 1, 2007

By N. B. Strydom, H. H. E. Schroder, A. van der Linde

This paper describes a study of the destination of the mercury that is present in the ore during the recovery of gold. It was found that over 96 per cent of the mercury passed through the process untouched. A small amount finds its way into cyanide solution, and is concentrated with gold in Zinc dust as Merrill precipitate. When the precipitate is calcined, the mercury is driven off and finds its way into the atmosphere. However, dilution of the stack gas in the atmosphere appears to be sufficient to prevent hazardous concentrations arising at ground level. No other significant concentrations of mercury were found at any stage of the process. The amount of mercury lost to the atmosphere by this mechanism appears to be less than 200 kg per year throughout the gold-mining industry in South Africa. Virtually no mercury vapour could be detected in the air in the smelt-house. Slight increases in mercury concentrations above background level were observed in soils around the reduction plants and in the discharge or return waters, but no environmental stress is anticipated from these increases.

Jan 1, 1982

By SHM Harkema, MKG Vermaak, D R. Groot

Surface Plasmon Resonance spectroscopy (SPR), combined with cyclovoltammetry, has been successfully used to study the interactions between ethyl xanthate, heptyl xanthate, dithiophosphate and propyl trithiocarbonate flotation collectors and a gold surface. Large, easily measurable responses have been obtained in the potential areas where the thiol collectors are known to interact with gold. The four collector types lead to differing SPR maximum values, with longer alkyl chains resulting in higher SPR responses, and the trithiocarbonate leading to the highest response values. The SPR responses differ considerably from the current density response at very anodic and cathodic potentials. There are indications that thiols might still be adsorbed at potentials as low as -300 mV (vs SHE). Keywords Flotation collectors; thiol collectors; cyclovoltammetry; surface plasmon resonance spectroscopy.

Jan 1, 2005

The kinetics of adsorption of gold di-cyanide onto activated carbon has been investigated extensively over the past two decades. These studies have demonstrated that both film and intra-particle mass transfer affect the kinetics. The dominant mechanism of intra-particle mass transfer has not yet been identified. In the work described, surface diffusion and pore diffusion are considered as possible rate-determining mechanisms of intra-particle mass transfer. Mathematical models are described that incorporate film mass transfer and the respective intra-particle mass transfer mechanism with equilibrium described by a Freundlich isotherm. Rate constants of film mass transfer and pore or surface diffusivities were estimated by the fitting of the respective models to experimental carbon adsorption data. The estimated pore diffusivities, after they had been corrected for the porosity and tortuosity of the carbon, were found in most instances to be higher than the molecular diffusivity of dilute gold di-cyanide in aqueous solution. This situation is not physically viable. The surface diffusion mechanism acting in parallel with the pore-diffusion mechanism is thus responsible for the intra-particle transportation of most of the gold.

Jan 1, 1996