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By A. Lane

The socio economic risks of mining in South Africa have been emerging for some time now, and have been brought into sharp relief by recent events in the platinum sector. The slow pace of social upliftment in the country has lead to widespread social unrest with consequent calls for different forms of resource nationalism. Fundamentally, the key stakeholders are not fully aligned, and are not engaging productively. This poses significant above-the-ground risk to mining companies. Measuring social impact, deploying inclusive solutions and engaging effectively with stakeholders are three ways in which mining companies can mitigate this risk.

Jan 1, 2013

By A. Feather

The Minataur? Process (Mintek Alternative Technology for Au Refining) is a novel route for the production of high-purity gold using solvent extraction. Following the successful demonstration of the process on a pilot-plant scale, a full-scale 24 t/a production plant has been commissioned at Harmony Gold Mine in Virginia, Free State. The commercial implementation of this process represents not only a significant advance in gold-refining technology, but may be instrumental in initiating important changes in the legislation regulating the marketing of gold in South Africa. Gold of either 99.99% or 99.999% purity can be produced from intermediate process products having a wide range of gold contents. The process comprises oxidative leaching of the solid feed, followed by selective solvent extraction of the gold from the leach liquor to reject impurities, and precipitation of high-purity gold powder. This paper outlines the process, presents selected results of two pilot-plant trials in which 5 kg/d of high-purity gold was produced from silver-refining anode slime and gold-electrowinning cathode sludge, and provides some details of the cost benefits.

Jan 1, 1997

By F. Peer

This Technical Note was presented as a poster at the Western Cape Mineral Processing Symposium held in August 2001 The cleaning of fine coal (-1000 µm) in today?s coal preparation plants is an economically important factor. Coals with high ash contents are, in general, commercially undesirable. Current well-known techniques for treating fine coal include froth flotation and spirals. The primary critical factor with regards to spirals is the efficiency of the process whereas that of flotation, is the cost of there agents used. Research into enhanced gravity separation techniques has resulted in several commercially available enhanced gravity separators. This project was based on a preliminary investigation into the feasibility of one such separator, to effectively treat fine (-500 µm) coal. Experimental variables included particle size and speed of rotation of the said instrument. The performance of the separator was compared to the results obtained from liquid density separations done for the two coal fractions evaluated. From the results obtained in this preliminary study it appears that the piece of equipment investigated does not measure up to expectations. Recommendations for further investigation include the evaluation of the instrument on other South African coals to obtain conclusive results.

Jan 1, 2002

By M. F. Wells

The method used to salvage South Deep?s Main Shaft after it was flooded by an inrush of water at about 450 m below collar on 1 May1996 is described. The individual techniques employed in the salvage were all proven technology, but the combination in which they were applied is considered to be novel. The operation involved the following activities in order of occurrence. ?the dewatering of the shaft with submersible pumps ?the placement of a French drain on the shaft bottom muck pile ?the positioning of large diameter heavy walled draft tubes, and smaller tightening up, grout intrusion and reverse flow pipes ?the casting and curing of a structural concrete plug; the capping of the draft tubes; the intrusion of several thousand tons of cement grout into the aquifer by pressure induced reverse flow ?the sealing of the aquifer ?extensive probe drilling and sealing of the zone around the inrush point with cement and other specialized grouts ?the mining out of the plug and the re-establishment of normal sinking routines.

Jan 1, 1999

By K. Ding

The thermodynamic activity of MnO was measured in MnO-CaO-MgO-SiO2 slags that are typically encountered in the production of manganese-containing stainless steels. A gas equilibration-quenching technique was employed in measuring the activities. Activities of Mn in Pt-Mn alloys were redetermined at 1600ºC, which reconfirmed earlier results of strong negative deviations. MnO activities were then measured by equilibrating slags of various compositions based on a statistical experimental design procedure with Pt-Mn alloys under controlled partial pressure of oxygen in MnO saturated platinum crucibles at 1600ºC. Activities of MnO were found to increase with increasing concentration of MnO, basicity and CaO to MgO ratio. Two multi-coefficient regression models were developed to predict the activities and activity coefficients of MnO in slags at 1600ºC. Keywords: activity, MnO, slag

Jan 1, 2005

By J. P. Theron

Paper written on project work carried out in partial fulfilment of Phd.(Process Engineering) degree Process modelling is an essential element in the development of advanced (model-based) process control systems, accounting for up to 80% of the cost of development. Often, models based on historic process data are the only viable option when dealing with processes that cannot be modeled cost-effectively from first principles. Despite major advances that have recently been made in the field of nonlinear process modeling, some basic idea of the dynamic behaviour of a process system is important prior to system identification. While many process systems seem unlikely to be linear, the possible nonlinear aspects of their dynamics are not necessarily supported by the data. This may have significant implications for subsequent system identification or interpretation of the data. For example, it is quite possible that an underlying nonlinear deterministic signal may be obscured by a high degree of measurement or process noise, to the extent that it may be critical in the choice of model to fit to the data. The method of surrogate data analysis has recently been proposed as a means to classify the underlying dynamics of complex systems, and in this paper the use of Fourier transform surrogates to classify process systems is explored. Keywords: modelling, process control, simulation, surrogate data analysis, nonlinear systems.

Jan 1, 2004

By D. Bessinger

The present paper provides a brief overview of the thermodynamics of titania rich slags, an outline of the Multi-Phase Equilibrium (MPE) package and its application to ilmenite smelting. Through assessment of published experimental data on various systems containing TiOx, it was found that despite considerable scatter in measured phase equilibria data for the binary Ti2O3-TiO2system,the behaviour of binary and higher order titania rich slags and oxide solid solutions phases could be represented by solution models in the MPE package. Results from the applications of the MPE model on the stability of solid phases and slag-refractory interactions will be presented and discussed. Parallels will be drawn between the predictions by the model and observations made during pilot plant tests. Key words: Thermodynamics, titania slags, ilmenite smelting, phase equilibria, refractory.

Jan 1, 2003

The Skorpion Zinc Project demonstrated the viability of the production of zinc from non-sulphide (commonly called ?zinc-oxide?) ores, using the leach/solvent extraction/electrowinning process route. The success of Skorpion raised the profile of a number of other zinc oxide deposits, considered to be similar. However, a study of three such deposits demonstrates that the application of whole-ore-leaching may be limited and that the concentration of zinc, or at least the separation from acid-consuming gangue minerals, prior to leaching is essential to the successful recovery of zinc from these deposits. The recovery of zinc is dependent on an understanding of the geology of the deposit, the mineralogical association of zinc minerals with gangue minerals (Boni, 2005) and limitations of mining practice. Flow sheet development and the associated metallurgical test work to derive an economically viable treatment route from two of these deposits are discussed. Key parameters affecting zinc recovery by gravity separation and flotation are presented, demonstrating that even minor differences in mineralogy have a profound impact on zinc recovery and reagent consumption. The study also deals with the determination of appropriate design parameters through metallurgical mapping of the dense media separation process.

Jan 1, 2008

By B. Kenny

The aim of this paper is to provide an overview of existing forms of subcontracting in the South African mining industry. A descriptive framework is developed to understand different subcontracting arrangements. We argue that, in order to do so, it is important to distinguish between labour broking and gang subcontracting. Data resulting from a research project (including an analysis of historical sources, interviews with contractors and focus group interviews with mineworkers) is presented to highlight the implications of changing formations of subcontracting for the South African mining industry in the late 1990s. Apart from the subcontracting of ?traditional? functions, such as shaft sinking, access development, catering and hostel maintenance, contractors are now used in ?core? mining activities. In some instances, whole shafts are ?outsourced? to outside agencies. It is argued that certain of the subcontracting arrangements have serious implications for the ability of the mining industry to improve health and safety standards. Some of the practices can potentially result in conflict between different categories of workers, and, as a result, instability in the industry.

Jan 1, 1999

By T. F. J. Hälbich

Namakwa Sands aims to conserve environmental resources and prevent or minimize environmental impacts from its operations. The challenge faced by Namakwa Sands is the rehabilitation of the arid winter rainfall Strandveld and lowland Succulent Karoo vegetation zones affected by its mining activities. Extensive experimentation with different rehabilitation methods resulted in the development of an effective rehabilitation programme. The use of topsoil as a seed bank and shade-cloth as windbreaks have significantly aided the rehabilitation process. The aim of the programme is to stabilize the soil environment so as to allow the germination and development of the local plant species. The ability to control wind erosion is critical to the success of the rehabilitation effort. A programme of biodiversity audits has been started to measure the recovery of plant species in the rehabilitated area. The principle of continuous improvement, coupled to site-specific rehabilitation studies, is applied to enhance the rehabilitation programme.

Jan 1, 2003

By M. K. G. Vermaak

There are practical indications that flotation recovery of palladium bismuth tellurides is poor. This work tested whether this can be caused by a lack of interaction of the collector with the telluride. Impedance measurements, voltammetry and Raman spectroscopy were performed to determine the interaction of dithiocarbonate collectors (KEX) with Pd-Bi-Te. Impedance measurements showed lower capacitance values in solutions containing KEX, indicating the formation of a continuous surface layer. Anodic and cathodic polarization diagrams show the mixed potential to be higher than the reversible potential of the xanthate-dixanthogen equilibrium reaction; hence the formation of dixanthogen on the surface is possible. Electrochemically controlled in situ Raman spectroscopy did indicate the presence of bulk diethyl dixanthogen on the surface. Raman spectroscopy has confirmed the co-presence of xanthate with dixanthogen, indicating that xanthate retains its molecular integrity when it adsorbs on the surface of the Pd-Bi-Te. As a result, the mineral surface is expected to be hydrophobic and alack of collector interaction with the mineral is not the reason for the low PGM recoveries experienced. Keywords: Raman spectroscopy; Pd-Bi-Te; ethyl xanthate; platinum flotation; Great Dyke; Pd-bearing bismutho-tellurides and moncheite.

Jan 1, 2004

By B. Samanta

This paper investigates the performance of the neural network technique in a placer deposit situated at the Nome district in Alaska. Initially a single neural network model was constructed to estimate the gold grade. However, at a later stage, an ensemble model consisting of multiple networks was also constructed via the Adaboost algorithm. The reason behind the use of the ensemble model of the Adaboost algorithm was to examine if the ensemble model provided superior performance to the single neural network. As indicated by other studies, Adaboost did not have a better performance than a single neural network in this specific application. This may be due to the high noise inherent in the gold data used in this project. Consequently R2 values of gold prediction are also poor for both the single and multiple networks.

Jan 1, 2005

By P. J. Bhonde, R. D. Angal

Conventionally low carbon ferromanganese is manufactured globally by refining high carbon ferromanganese in liquid state. This process is an expensive and lengthy technique. Hence, the present work was undertaken with the objective of understanding the feasibility and kinetics of the solid state refining of ferromanganese. The process involved transformation of carbon rich carbides viz. Mn3C2, Mn7C3 into metal rich carbide i.e. Mn15C4, Mn23C6 by subjecting the alloy powder to a flowing stream of carbon dioxide. Effect of the process governing parameters such as time, temperature, particle size, pressure on the extent of decarburization was studied. Without any loss of manganese in the form of fumes or slag, it was observed that, there was substantial reduction, viz. 65 per cent in the total carbon content, by this technique. Subsequently, the process was investigated to find out the mechanism of carbon removal. Depending upon the temperature and the particle size, it was found that the rate controlling mechanism changes from chemical reaction control to product layer (ash) diffusion control. The activation energy for each of the aforesaid mechanism was computed. The values thus obtained substantiated the aforesaid mechanisms.

Jan 1, 2004

By J. F. Curtis

In the synopsis, the author concludes that ?high levels of seismicity do not coincide with high rockburst rates?. Implicit to an appreciation of this statement is the necessity of a common understanding of what is understood by the terms: ?high level of seismicity? and ?high rockburst rates?. With respect to the former term there is no difficulty in that the level of seismicity is traditionally measured in terms of the Richter Scale. The latter term however presents a problem in that the author defines it as a particular sort of seismic event?viz: ?Rockburst? is understood as a seismic event that causes damage to an underground excavation with subsequent injury, loss of material/equipment or production shifts? (p. 322). No scale is given of the amount of: ?excavation damage ?level of injury ?material/equipment loss ?production shifts lost whether separate or cumulative, for a particular seismic event to be classified as a rockburst. A further difficulty arises in that in common usage the words ?rockburst?, ?seismic event? and ?earthquake? are all used to describe the same event.

Jan 1, 1999

By P. M. Cole

An unprecedented expansion of the global zinc industry is currently under way. While most new projects and plant upgrades remain committed to traditional processing technologies, recent advances in zinc solvent extraction (SX) have created opportunities for new process routes for both primary and secondary materials. The first commercial plant to use zinc SX for the mainstream processing of a low-grade ore is under construction and promises to become one of the lowest cost zinc producers. Several other oxide and sulphide projects in various stages of feasibility are considering the inclusion of SX in their process flowsheet. Zinc SX has also proved advantageous in the reprocessing of secondary materials, particularly for the treatment of zinc residues and furnace dusts. This review focuses on recent installations and projects underdevelopment that feature zinc SZ as the key separation step.

Jan 1, 2002

By M. Nyoka

Consideration of the economic, environmental, and social impacts associated with the life-cycle of a technology is of increasing importance for decision-making in industry. It has been suggested that economic assessment of technology deployment projects requires the translation of associated environmental effects into monetary values. This paper introduces an approach for identifying and evaluating environmental damage in monetary terms. The approach groups the environmental impacts associated with a technology life-cycle system into four main criteria: air, water, land, and mined abiotic resources. The valuation of the impacts on the resources consists of an economic cost benefit analysis (CBA) procedure that comprises four steps: the compiling of an impact inventory, a monetary valuation of the inventory, discounting, and a risk/uncertainty analysis. The monetary valuation step for impacts on air resources is primarily based on published externality costs for Europe and the United States, which are adopted and converted to reflect the South African context. Local opportunity costs are utilized for the other resource criteria. The damage costs are transformed into South African Rand at 2005 prices. The paper demonstrates how the approach may be applied in the assessment of projects in the metallurgical industry. Shortcomings in the approach are identified. For example, not all of the aspects that are considered necessary to assess environmental performances comprehensively can be valued in monetary terms. Also, certain values, specifically those pertaining to opportunity costs, need to be determined on a case-by-case basis. Furthermore, the uncertainties associated with the indicators obtained may strongly influence the usability of the results of an environmental performance assessment, e.g. future damage costs will change with fluctuations in the markets. It is concluded that although such an approach has merit in increasing the understanding of the potential financial implications of a technology?s environmental performance, further research is required to improve the approach described if it is to be used further in the South African metallurgical industry. Damage cost estimates that are specific to South Africa need to be developed to reduce uncertainty, and the combination of both quantitative and qualitative approaches is recommended for comprehensive sustain-ability decision-making.

Jan 1, 2007

By R. M. Whyte

The Konkola Deep Mining Project (KDMP) seeks to exploit the deep level potential of the Konkola Deeps orebody, producing high grade copper concentrates for treatment at the Nkana Smelter and Refinery. As an alternative to smelting, Konkola Copper Mines (KCM) has examined a processing route involving pressure leaching of the Konkola concentrates at Nchanga, with the leach liquor being treated by solvent extraction and electrowinning to produce high purity copper cathode. The solvent extraction circuit would be operated to achieve a high ?delta? copper, thereby providing a strong acid raffinate which can be used in the existing Tailings Leach Plant (TLP) to treat Nchanga oxide copper materials. The main focus of the hydrometallurgical option is to capitalize upon the synergy that exists between the treatment of sulphide copper concentrates (acid producing) and oxide copper ores (acid consuming). The paper discusses the key features of a comprehensive piloting campaign carried out at Anglo American Research Laboratories, which involved the co-treatment of Konkola copper concentrates and Chingola refractory ore in a fully integrated pilot plant circuit.

Jan 1, 2001

By F. T. Cawood

Monitoring of the slopes of surface mines can prevent loss of life, loss of equipment, loss of production and possibly the loss of the mine. The effectiveness of such monitoring depends on the extent to which slopes give adequate advanced warning before failing, and on the ability of the monitoring system to detect such warning. In this paper an overview is given of slope monitoring requirements, from both the geotechnical and survey points of view, as well as the types of equipment and instrumentation that are available. Legal issues relevant to slope monitoring are also dealt with. It is concluded that conventional geotechnical and survey instrumentation will continue to have their place in slope monitoring. However, the slope monitoring scene has changed substantially in recent years. A real and volume-based monitoring equipment is now available and this has provided, and will continue to provide, the means to improve safety, and to enhance productivity in mining. Its benefit to slope management is substantial. In the near future it is expected that data obtained from such equipment will add a much needed new dimension to slope engineering, and be used to improve slope designs and to optimize slope angles.

Jan 1, 2006

Council for 1996/97 President Dr N.A. Barcza President Elect R.P. Mohring Vice Presidents Senior J.R. Dixon Junior M.H. Rogers Immediate Past President D.A.J. Ross-Watt Honorary Treasurer J.A. Cruise

Jan 1, 1997

Ongoing rockpass problems on mines within the South Africa region, prompted AngloGold Ashanti to embark on a risk assessment of major rockpasses. This commenced with the collection of relevant data to identify gaps in the available knowledge and identify existing problems. This was followed by an assessment of rockpass layouts to determine existing and potential interactions with other excavations. An initial risk assessment has been completed and the rockpasses have been ranked in terms of their risk profile. The lack of geological data and an easy and reliable method of surveying rockpasses have been identified as problem areas. Shortcoming is terms of rockpass management procedures have also been identified. Further work is required to quantify the risk in terms of probability of occurrence and consequences.

Jan 1, 2005