Search Documents

By D. A. Viljoen

The ore mined at Black Mountain is of a complex nature, being composed of both magnetic and massive sulphides, which have greatly varying metal values. Because of this, there is need for a rapid method of assaying for the continuous monitoring and control of the process streams, and the Outokompu Courier onstream analysis system and the Proscon process-control computer systems have therefore been installed. Geostatistics In view of the continuing demand, the Department of Mining and Mineral Sciences in association with Special Courses Division, Department of Adult Education and Extramural Studies, both of the University of Leeds, will offer two further courses on A Practical Introduction to Geostatistics in 1981, each covering ten working days. The courses will run from 30th March to 10th April and 14th to 25th September.

Jan 1, 1980

By B. E. Protheroe, C. Allen, A. Ball

The results of laboratory abrasive and abrasive-corrosive tests carried out on a range of carbon, Iowalloy, and stainless steels are compared with underground tests conducted on similar materials on prototype shaker conveyors carrying gold-bearing quartzitic rock. The dry-abrasion resistance of all the steels was found to be better than that of mild steel. When the added effect of corrosion was tested, the stainless steels proved to be much superior to proprietary abrasion-resistant alloys both in the laboratory and underground. The ferritic stainless grades were shown to be superior on the basis of cost per unit of volume lost. This investigation has shown that laboratory tests on materials can provide valuable information on their possible performance in situ, and can thus be used to replace lengthy experiments on site.

Jan 1, 1981

By R. L. Paul

Although it is often said that South Africa does not have suitable deposits, or the potential to develop mines on a small scale, a recent survey by the Chamber of Mines1 showed that, out of a sample of 641 producers, 41 per cent had between 10 and 19 employees, and a further 29 per cent had between 20 and 29 employees. This goes to show that minerals-related small, medium, and micro-enterprises (SMMEs) do exist, and can play an important role in the development of rural industries in South Africa. Nchaka Moloi of the Department for Mineral and Energy Affairs defined the various categories of SMMEsas shown in Table I2. An enterprise could be placed in a certain category as long as two of the variables, employees, capex or production applied.

Jan 1, 1997

The aspect ratio (mill diameter/mill length) of autogenous and semi autogenous mills varies widely and can be as high as three or as low as 0.5. The literature on the subject of what effect aspect ratio has on grinding mill performance or energy efficiency is almost non-existent. However, at the design stage of many grinding circuits the subject is often vigorously debated amongst metallurgists. In this paper the performance characteristics of mills with different aspect ratios are examined to determine whether process performance characteristics are a function of aspect ratio and whether high aspect ratio mills are any more or less energy efficient than low aspect ratio units. Data from both pilot and full-scale mills are used for this purpose in open and closed circuit configurations.

Jan 1, 2007

By M. T. G. Davis, J. V. Cleasby, H. J. Wright

Mining practice in the Kimberley Division of De Beers Consolidated Mines Limited by J. V. CLEASBY. B.Sc.. A.R.S.M. (Fellow). H. J. WRIGHT. B.Se.. M.Sc.. (Fellow). And M. T. G. DAVIES. B.Sc. (Visitor) T his paper highlights the changes that are taking place at De Beers Consolidated Mines Limited in mining methods, mechanization, and employment practices. De Beers has four underground mines in Kimberley itself (Dutoitspan, Bultfontein, De Beers, and Wesselton), and two open-cast mines outside Kimberley (Finsch and Koffiefontein). Emphasis is placed on the new method envisaged for Koffiefontein when it becomes an underground mine. The paper also includes notes on chemical drilling and on winding practices.

Jan 12, 1975

PREFACE During the past year, the Council of the SAIMM undertook a major strategic-planning exercise to review all its current activities, and to redefine its scope and objectives in the light of changing circumstances. The following are the four main concerns that prompted Council to take stock of the situation. (1) Over the past five years, the SAIMM has become heavily involved in a variety of new activities. (There are many examples, of which the expansion in book publications and the establishment of physical metallurgy as a third major discipline with its own colloquia and schools are perhaps the most important.) While these new activities have considerably broadened the SAIMM's scope, they have resulted in a significant increase in the day-to-day workload of the President, Office Bearers, and Council members, and of the secretarial staff based at Kelvin House.

Jan 1, 1986

By J. C. Coetzee

In this article, a case is made for the importance of the transfer and management of tacit knowledge to ensure continued sustainable competitive advantage within the pyrometallurgical industry in South Africa. The state of knowledge management (KM) is assessed through a theoretical and empirical study. The empirical part of the study was conducted by means of a survey questionnaire. An important prerequisite within the research entailed determining the current state of KM within the pyrometallurgical industry, and the findings are presented throughout this article. The research argues for initiatives to address the high turnover of pyrometallurgical knowledge workers. This industry needs to entrench tacit knowledge and therefore address the problems associated with the continuous loss of inherent specialized knowledge. Appropriately, emphasis is placed on identifying initiatives required to embed and retain not only human capital lost through mobility, but rather retaining tacit knowledge through a practical KM framework.

Jan 1, 2012

By R. Heunis

The hazard of rock bursts and rock falls as experienced in South African gold mines is examined in the light of recent research findings. The problem areas include high fatality rates, losses in production and equipment, and a detrimental influence on the recruitment of labour. The nature of the hazard is analysed, and it is shown that rock bursts are strongly related to the spatial rate of energy release by mining but that rock falls are not. The role of blasting and geological discontinuities is discussed. Practical rock-burst control strategies are compared, including the use of stabilizing pillars, back-filling and, in particular, techniques for reducing the frequency and severity of accidents resulting from large rock bursts. The latest stope-support experiments and their potential implications to mining are consid~red. It is concluded that a better understanding of the rock-burst and rock-fall hazard has resulted from the industry's research efforts. The findings can be applied towards obtaining an improved underground environment for men and machines.

Jan 1, 1980

By S. M. Spottiswoode

A simple method for the application of excess shear stress (ESS) analysis to the mining of planar reefs is examined. The potential for seismicity associated with mining is expressed as the calculated increase in ESS on a regular grid of points 50 m above the reef, and is compared with observed seismicity around a deep-level, relatively geologicaly-undisturbed gold mine. Thirty regions were studied, involving over 2000 seismic events with magnitudes greater than 1,5 on the Richter scale and associated with almost 2 million square metres of stoping. The total seismicity, measured either as the number of seismic events or as the total radiated energy, corelated more closely with changes in ESS than with ERR. The incidence of rockbursts also favoured the ESS model. Corelation coeficients of around 0,8 for seismicity and ESS indicated that the assumptions inherent in the method used are collectively reasonable. The total seismicity in each region was found not to be strongly controlled by the presence of dykes and faults, although numerous individual seismic events were located close to such features.

Jan 1, 1988

By S. K. Lahiri, K. C. Ghanta

Design of industrial slurry pipelines is usually performed by applying semi-empirical procedures, requiring a significant experimental study for each project. The mechanisms of suspension flow are not yet completely understood and existing predictive models cover only some aspects of uniform or closely graded particle slurry flows. This paper presents a computational technique for prediction of the velocity and concentration profile in slurry pipelines based on computational fluid dynamics. This model gives numerical solutions for the concentration and velocity distributions in the pipeline cross-section. The model prediction and experimental concentration and velocity profiles were found to be in good agreement. Keywords: pressure drop; concentration profile; particle diffusivity; slurry flow.

Jan 1, 2007

By Isobel Clark

This paper reviews some of the traditional methods of reserves estimation based on lognormal distribution with or without an additive constant. In the rush to computerize mine planning and grade control generaly, proven estimation methods, such as Sichel's t, seem to have been overlooked. By use of a personal microcomputer, the traditional methods were investigated thoroughly, the results being tested against existing tables and figures. The fitting of a lognormal distribution, including estimation of the additive constant, is discussed, and the calculation of Sichel's t estimator and its associated confidence limits is described in detail. Payability calculations for a lognormal distribution are also covered briefly. The advantages of personal computers, particularly speed and ease of use, are emphasized. This low-cost approach permits detailed investigation of some of the assumptions and approximations inherent in the established methods of calculation. Several disturbing discrepancies are revealed in various factors, and some generalized statements made by previous authors are found to be over-simplistic. Full details are given of acceptable approximations and computer algorithms, and concern is expressed over the possible loss of proven methods under the welter of new, sophisticated computer software.

Jan 1, 1987

The results of small-scale resin-in-pulp pilot-plant investigations at Grootvlei Proprietary Mines Ltd, President Brand Gold Mining Co. Ltd, and Western Areas Gold Mine Co. Ltd are reported. At each mine, a pulp was fed simultaneously to a carbon-in-pulp plant, allowing a direct comparison of the metallurgical performance of the two processes. With the Grootvlei pulp, gold was extracted more efficiently by resin than by carbon owing to the Iow concentration of competing base-metal cyanide complexes in solution. With the Western Areas pulp, the reverse was true because of the high concentrations of copper and nickel in solution. Finally, with the President Brand pulp, resin-inpulp was significantly superior to carbon-in-pulp owing mainly to the inherently slow rate of gold extraction from calcine by activated carbon. Results are presented that show the efficiency of the elution of gold and other elements with a variety of reagents from the loaded resins arising from these three campaigns. At Western Areas, a detailed investigation enabled a preliminary cost evaluation to be made of three techniques for the elution of strong-base resins.

Jan 1, 1984

By R. P. King

The flotation behaviour of phoscorite from the Phosphate Development Corporation was measured in a pilot plant, the flotation cells in the plant being varied in configuration so as to operate with or without circulating loads. The ore was floated in a batch cell so that the parameters for a kinetic model could be estimated, and these parameters were then used in a flotation-plant simulator, which is based on the kinetic model, in the prediction of the performance of a pilot flotation plant operating on phoscorite. The simulator predictions compare well with the measured performance of the ore in the pilot plant, but the comparison shows that the kinetic model is not completely adequate for the prediction of performance in continuous flotation plants. The model is weakest in its ability to model the behaviour of the froth phase. The flotation behaviour of the ore could be adequately described when it was assumed that the apatite and gangue each consist of floatable and unfloatable components. The effect of particle size on the specific flotation-rate constant of apatite was found to have a maximum at 85 µm and to fall to zero at 400 µm that for the gangue had a maximum at 50 µm and was zero at 350 µm.

Jan 1, 1978

Scrap printed circuit boards were selectively smelted at 1 200°C to produce a metallic alloy having three phases. These phases were identified as a lead-rich phase, a low tin content alpha bronze phase, and a high tin delta phase. Electrochemical leaching studies on this alloy were done in 1 mol/dm3 sulfuric acid or in 2 mol/dm3 hydrochloric acid (adjusted to an ionic strength of 3 mol/dm3). The lead rich phase was more strongly passivated in sulfate media, and in this medium the high tin content delta bronze was more resistant to corrosion than the lower tin alpha bronze phase. In chloride medium the lead phase and both bronze phases corroded readily, but with current densities about an order of magnitude lower than in sulfate medium (static conditions) for the bronze phases. The high tin delta bronze phase was found to form a passivating layer in sulfate media. A similar layer was not seen in chloride medium. The leaching studies in sulfate medium also showed the existence of an alpha bronze phase of lower tin content in the centres of the alpha phase grains. This phase was quite resistant to leaching in sulfate medium.

Jan 1, 2009

By R. Hoare

TSG Consulting works with many of the major global mining companies using simulation modelling as an integral component in their development team's processes to determine which combination of infrastructure options, operating performance and operating rules best achieve project goals. All systems can be divided into a series of subprocesses. Conventional management and design practices focus on the optimisation of these system components. However, the interaction between subprocesses means that improvements made to the individual components do not necessarily translate into total system performance improvement. TSG Consulting advocates a `total integrated system approach' to understanding the behaviour and performance of complex interacting systems. In a constraint-based integrated set of processes, the instantaneous system capacity is limited by the subsystem component capacity that is the bottleneck at that point in time. Additionally, real world stochastic and dynamic influences tend to have knock-on effects across subsystem boundaries. This necessitates the requirement for simulation modelling to develop and validate solutions that are sufficiently robust to deliver sustainable outcomes. The key to maximising production is to understand the causes and effects the inherent variability has on component performance, subprocess performance and most importantly, the total integrated system performance. The correct use of simulation modelling techniques allows study teams to evaluate the relative merits of different capacity enhancement proposals. Put simply, when done well, simulation modelling provides a quantitative and rational process to enhance the knowledge and insight needed to make informed decisions.

Jan 1, 2007

The Copperbelt areas of Zambia and the Democratic Republic of Congo (DRC) have recently been seeing the development of a significant number of new projects. Due to the current economic climate, some of these projects have been delayed but the region remains an important resource for copper and cobalt for future years. Many of these projects will utilize an agitation leach followed by solvent extraction and electrowinning to recover both copper and cobalt. The flowsheet route for copper is fairly well established while the processing options for cobalt vary considerably depending on the final product (metal or salt) the operator wishes to make. The mineralogy of ores in the area is typically associated with high gangue acid consumption during the leaching process. This has resulted in acid availability to the area being constrained and acid prices have risen accordingly. Agitation leach circuits, typically, have a tight water balance which needs to be maintained and a bleed of process liquor needs to be continuously removed from the circuit in order to maintain this balance. This bleed, typically, contains fairly high levels of acid and requires neutralization prior to tailings disposal or secondary metal recovery. It is, therefore, desirable to minimize the acid concentration in this bleed stream in order to decrease total acid requirements and neutralization costs for the process plant. An in depth case study by Cognis and Bateman Engineering evaluated three different flowsheets with the aim of determining relative operating costs between the three alternatives, together with differences in plant capital cost requirements.

Jan 1, 2009

By L. W. Helle

In this investigation, which was conducted at the Metallurgical Research Plant, Lulea, Sweden, a series of experiments were carried out using a water-model to simulate the gas rinsing of a ladle containing liquid metal. The factors examined include the effect of gas flowrate, the position of a porous plug or lance, the immersion depth of the lance, and the geometry of the bath at the time of complete mixing. Mixing times were recorded by conductivity measurements. The results showed that there is a threshold level for mixing above which no advantage is to be gained from an increase in the gas flowrate. It is suggested that the results can be applied to rinsing ladles in working situations, the levels being approximately 270 dm3/min for 40 t ladles and 780 dm3/min for 150 t heats. The optimum siting of the lance or porous plug is a position that is three-quarters of the internal radius from the centre of the ladle with the lance penetrating as deeply as possible into the ladle. The best design of liquid bath is that having a diameter-to-height ratio of I. An equation was developed for the calculation, by dimensional analysis, of the time required for mixing during gas rinsing, and a comparison of the calculated mixing times with the results from production trials shows a satisfactory agreement (with a correlation factor of 0,91). Thus, an equation is available for the calculation of the stirring time needed to completely mix the bath in production situations.

Jan 1, 1981

By E. Uslu

The kinetics of the reduction of chromite from the LG-6 layer of the Bushveld Complex in Fe-Cr-C alloys were studied in the temperature range 15OO°C to 1680°C under an inert argon atmosphere. The rotating cylinder technique was used, and the rotational speed of the chromite cylinder ranged from 0 to 1000 r/min. The melt consisted of 30 to 80 per cent chromium and 2 to 8 per cent carbon. The initial chromium-te-iron ratios of the melts varied between 0,42 and 4,95. The reduction of chromite spinel was analysed in terms of the decarburization of the metal. It was found that decarburization increased with an increase in the temperature, the carbon content of the bath, and the rotational speed of the cylinder up to 400 r/min, after which it remained almost constant. Decarburization also increased with an increase in the chromium content up to about 50 per cent chromium but, at higher chromium contents, it decreased. In the early stage of the reduction, up to about 30 minutes of reaction time, the liquid-state mass transfer of oxygen was found to be the most likely rate-determining step. The apparent activation energy was calculated to be 84,864 kJ per mole of oxygen. In the later stage, diffusion of iron and/or chromium in the solid state is the most likely rate-determining step. The apparent activation energy for the diffusion was calculated to be 471,18 kJ/mol.

Jan 1, 1991

One of the main bottlenecks in the carbon-in pulp process for the recovery qf gold is the elution procedure, which typically requires the heading of caustic cyanide eluants to high temperatures for 16 to 24 hours. The present work demonstrates that sodium sulphide solution as an alternative eluant can effect complete elution in about 4 hours at ambient temperatures. Elution efficiencies of around 100 per cent were obtained in 4 hours with a single pass of eluant containing 0,2 M Na2S and 0,4 NaOH about 10 bed-volumes of eluant The initial rate was slow over the first hour of elution, probably because the activated carbon catalysed the oxidation of sulphide to polysulphide. Elution efficiencies of around 100 per cent were also obtained in less than 4 hours during the batch elution of carbon at liquid-to-solid ratio of about 100. Lower liquid to solid ratio resulted in the re-adsorption of gold, probably owing to the oxidation of sulphide to polysulphide, with the resultant formation of gold complexes that were eluted less readily. Improved rates of elution were obtained at higher sulphide concentrations and pH values greater than about 13. Higher temperatures increased the initial elution rate, but lowered the overall extraction efficiency, probably because of the deposition of elemental gold on the carbon. Variation of the ionic strength by the addition of NaCl had no defect on the elution, which confirms that the elution mechanism in the case of sulphide is different from that when cyanide or I1)1droxide is used as the eluant. It is proposed that the elution of gold by sulphide solutions proceeds by means of an initial step that involves the reaction of polysulphide ions with the adsorbed aurocyanide speeds, forming AuCN on the carbon and thiocyanate in solution. This step is followed by the formation of poorly adsorbed complexes with sulphide ions, such as [AUS3-2]-The presence of polysulphides, whether generated in situ by the catalytic oxidation effect of activated carbon or by the addition of elemental sulphur, reduces the elution rate and efficiency dramatically. This is probably due to the formation of complexes such as AUS-3 and AUS-2 , which have a high adsorption affinity.

Jan 1, 1994

By M. Bester, R. Carey, T. Russell, J. van Heerden

"In order to reach the goal of optimal and safe extraction of the mineral reserve, the mining industry is increasingly focusing on reconciliation across the mining value chain to ensure that the mining process occurs in a progressively more predictable manner. This will consequently improve the understanding of mine plans and their associated implementation risks, ultimately leading to increased investor confidence. In terms of geotechnical engineering, mine to design performance assessment is a critical aspect of mine to plan adherence focusing on the complex aspects influencing slope performance. A mine to design reconciliation process therefore needs to systematically track implementation and geotechnical aspects in order to review or update slope design criteria and pit layouts according to the mine planning cycle as the mine is developed. This paper describes the development and implementation of a standardized mine to design reconciliation system for operations utilizing laser scanning technology, analysis tools, as well as associated key performance indicators. Performance is evaluated on final pit boundaries in terms of geometry achieved as well as blast performance evaluation of face conditions. These aspects as well as the resulting catch berm capacity should be captured in an information system, enabling longer term trend analysis and detailed root cause analysis where unsatisfactory outcomes occur. Adverse outcomes should subsequently be incorporated into the mine’s risk management process informing risk mitigation measures including blast design adjustments, slope design changes, or rockfall protection measures. IntroductionIn order to reach the goal of optimal and safe extraction of the mineral reserve, the mining industry is increasingly focusing on reconciliation across the mining value chain to ensure that the mining process occurs in a progressively more predictable manner. This will consequently improve the understanding of mine plans and their associated implementation risks, ultimately leading to increased investor confidence. In terms of geotechnical engineering, mine to design performance assessment is a critical aspect of mine to plan adherence focusing on the complex aspects influencing slope performance. A mine to design reconciliation process therefore needs to systematically track implementation and geotechnical aspects in order to review or update slope design criteria and pit layouts according to the mine planning cycle as the mine is developed."

Jan 1, 2016