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By G. P. A. Howe

"A computer model of the rutile, ilmenite and zircon industry was developed jointly by Associated Minerals Consolidated and Consolidated Gold Fields for exploring marketing strategies and making predictions over a ten-year period. The industry is described briefly and the reasons for modelling it and choosing a deterministic approach explained. The economic structure of the model and its level of complexity are discussed. The necessity and techniques for convenient input and clear output, the team composition and the method of work are discussed.The reasons for the choice of FORTRAN, large computers, remote batch terminals and the vital importance of fast turn-round are discussed.Costs in staff time and computing are given, with an assessment of the reasons for the success of the model. The model is used on a regular basis to aid management decisions."

Jan 1, 2014

In the investigation described here, it was found that the main effect of temperature is on the rate of flotation, and that adsorption of the reagent is not rate controlling. Above 10°C, the flotation rate of pyrite and gangue increases almost exponentially with a rise in temperature. Below that temperature, the flotation rate of pyrite shows a sudden marked decrease, that of gangue increases, and the sulphur grades are significantly poorer. In the flotation of pyrite, the mass transfer of the pyrite from the pulp to the troth is thought to be the ratecontrolling step, whereas the flotation of gangue is controlled by the combined effect of the stability and velocity of the froth and the viscosity of the elutriating medium. The latter is probably the controlling effect at temperatures below 10°C. Little difference was noted in the recoveries (provided no time limit was set) with changes in temperature; hence adequate recoveries can be obtained at Iow temperatures by the introduction of longer residence times for the pulp. The adverse effects of Iow temperatures on grades can be overcome only by additional cleaning or by heating of the pulp.

Jan 1, 1984

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 P. M. Swash

A mineralogical investigation of the main causes of refractoriness of some metalurgicaly complex gold ores in South Africa is reported. It is shown that this refractoriness is related to the presence of submicroscopic gold, carbonaceous material, pyrhotite, and base-metal sulphides. Gold ores can be classified according to their content of these components. Electron-microprobe analysis shows that gold occurs in arsenopyrite and pyrite, the gold contents of which can be up to 2700 gft. The gold and arsenic contents of these minerals are closely corelated. Furthermore, within zoned arsenopyrite grains, the concentration of gold closely folows that of arsenic. Mossbauer spectroscopy caried out on samples of concentrate from the Barberton area indicates that the submicroscopic gold within the sulphides is in a non-metalic form. The mineralogical examination of beneficiation products is important, since it sheds light on some fundamental aspects of the behaviour of the ore and gangue components during milling and flotation. Such basic information will lead ultimately to a better understanding of the problems in the beneficiation of these ores. Investigations have shown that the overmiling of the auriferous arsenopyrite and the disseminated nature of the sulphide mineralization are the main problems during beneficiation.

Jan 1, 1988

By D. van Heerden, M. F. Breed

"Successful development of projects or life-of-mine strategies requires an understanding of the relative sensitivity of value drivers such as grade, tonnage, energy costs, direct operational costs, and recoveries. For example, the results could vary significantly depending on the grade strategy, given a specific orebody amenable to open pitting.Pit optimization is a very powerful tool widely used in the industry to determine the pit shell with the most attractive value potential. Based on the input parameters utilized, the pit optimization process determines the stripping ratio, mineable reserves, and pit shape, and effectively calculates a cut-off grade, assumed to be the optimal cut-off grade.Once the initial pit optimization process is completed, the need may arise to align the optimization results with the company strategy by further optimizing other criteria, such as maximizing short-term cash flow. This paper describes and discusses the selection of an alternative cutoff grade as a strategic intervention. It involves changing the cut-off grade, effectively increasing the head grade to gain a strategic advantage aligned with the company strategy, with a clear understanding of the financial value impact. With this knowledge, it is clear that pitoptimization establishes the basis for future analysis and refinement.IntroductionIt is common for companies to select the optimal pit shell defining the mineral reserve without much further consideration. However, companies may consider various strategies to optimize the long-term value of the project or to optimize the short-term cash flow. Analysis of the entire life-of-mine value estimation process shows that the selection of a cut-off grade and other parameters should be based on careful analysis. Determining the optimal cut-off grade of ore at a different period during the life of mine to maximize the value is often one of the most difficult challenges for a company.A cut-off grade is the lowest grade that mining activities will target. As a result the average mining grade, which drives the value of a project, will always be higher than the cutoff grade applied.According to Bascetin and Nieto (2007) cut-off optimization is still not widely practised. Cut-off grade optimization is an effort to maximize the value of a project by understanding the capacity constraints in the mine, mill, and the market. At any point during the life of mine, any or all of the limitations on tonnage mined, tonnage milled, and product sold may be constraining the system. To ensure cut-off optimization is done correctly, the capacity constraints must be independent of the cut-off grade."

Jan 1, 2016

By S. Özgen

In this study, the possibility of beneficiation of chromite tailings in the Uckopru/Fethiye-Turkey region by a combination of hydrocyclone and multigravity separator (MGS) was investigated. The two significant operational parameters of hydrocyclone, which were diameter of the apex and diameter of the vortex, and the three significant operational parameters of the MGS, which were drum speed, tilt angle, and wash water, were varied and the results were evaluated with the central composite rotatable design. In order to produce a chromite concentrate by hydrocyclone and MGS, mathematical model equations were derived by computer simulation programming, applying the least-squares method using Minitab 15. Second-order response functions were produced for the grade and recovery of chromite concentrates.

Jan 1, 2012

By D. D. Marsden

The paper briefly outlines the history of the successful development of vegetating techniques for mine-residue deposits. It seeks to place on record the major roles played by M.J. Mrost, who initiated and systematically developed the concept, and W.H. Cook, who continued the trials and successfully directed a stupendous large-scale project. The vegetating techniques currently practised are outlined, and it is concluded that vegetating is still the only surface-stabilizing technique of any significance that is employed throughout the world.

Jan 1, 1987

By D. A. Viljoen

An account is given of the development of man's interest in the recovery and working of minerals from Palaeolithic times to the present. This is followed by a discussion of future production trends for the more important minerals, and of likely technological developments in the recovery of various minerals. The crucial importance of energy minerals is stressed, as are several other factors of significance to a flourishing minerals industry: manpower, education, financial climate, Industrial health and safety, and preservation of the environment.

Jan 1, 1979

By C. Zangerl, K. F. Evans, S. Loew

ABSTRACT: Settlements above fractured crystalline rock masses are rarely observed and in the past, geotechnical engineers would not expect substantial subsidence to occur in association with a deep tunnelling project. However, recent high precision levelling measurements along the Gotthard pass road in central Switzerland, have revealed up to 12 cm of subsidence along sections that pass several hundred metres above the Gotthard highway tunnel. Large-scale consolidation resulting from tunnel drainage and pore pressure changes in the rock mass are believed to be the contributing mechanism. This paper presents results from an extensive numerical modelling study focussing on the processes responsible for this subsidence. Results derived from 2-D discontinuum (i.e. distinct-element) and continuum (i.e. finite-element) modelling show that both discrete fracture deformation (i.e. fracture closure and shear) and poro-elastic consolidation of the intact rock matrix equally contribute to the observed magnitudes and shape of the surface subsidence trough. RÉSUMÉ: Des tassements aux dessus de massifs cristallins sont rarement observés et par le passé les géotechniciens ne prévoyait pas de subsidence significative associée avec des projets de tunnel profond. Cependant, de récentes campagnes de nivellement haute précision le long de la route du Col du Gotthard (Suisse centrale), ont mis en évidence des subsidences atteignant 12 cm sur des sections passant plusieurs centaines de mètres au-dessus du tunnel routier du Gotthard. Le mécanisme invoqué pour expliquer ce phénomène est la consolidation à grande échelle due au drainage du tunnel et aux variations de pression de pore dans le massif rocheux. Cet article présente les résultats d’une modélisation numérique intensive mettant l’accent sur les processus responsables pour la subsidence. Ces résultats obtenus grâce à des modèles 2-D discontinus (p. ex. éléments distincts) et continus (p. ex. éléments finis) montrent que la déformation sur des fractures discrètes (fermeture de fractures, cisaillement) ainsi que la consolidation poro-élastique de la roche intacte contribuent également aux magnitudes et aux géométries de subsidence observée en surface. ZUSAMMENFASSUNG: Beachtliche Oberflächensenkungen in einem kristallinen Gebirge, deren Ursache im Vortrieb eines mehrere hundert Meter tiefgelegenen Tunnels liegt, wurden bisher nicht erwartet und beobachtet. Dennoch wurden nach dem Bau des Gotthardstrassentunnels, entlang der Gotthardpassstrasse Oberflächensenkungen mit einem Maximalbetrag von 12 cm bei der Auswertung von Präzisions-Nivellements entdeckt. Dieser Maximalbetrag wurde in einem granitischen Gneis gemessen. Die örtliche Übereinstimmung zwischen dem maximalem Senkungsbetrag und dem maximalem Wasserzufluss zum Tunnel, und die zeitliche Abfolge von Tunnelbau und auftretenden Oberflächensenkungen lassen hydromechanisch gekoppelte Prozesse als Ursache dieser Gebirgsverformungen vermuten. In dieser Arbeit werden die Ergebnisse ausgedehnter prozessorientierter numerischer Simulationen präsentiert. Resultate aus den 2-D Diskontinuum (d.h. distinct-element) und Kontinuum (d.h. finite element) Simulationen zeigen, dass beide Verformungsmechanismen, d.h. an diskreten Brüchen und der intakten Gesteinsmatrix, gleichbedeutend für die beobachteten Senkungsbeträge und der Form des Setzungstroges verantwortlich sind.

Jan 1, 2003

By G. Nino de Guzman, L. C. Woollacott

The isotherms that are usually taken to represent the force 'driving' the adsorption in carbon-in-pulp processes may change from contactor to contactor. This paper reports on an investigation into the extent to which this Isotherm shift is Influenced by the changes in oxygen and cyanide concentration that occur in operating plants. The impact of the isotherm shift on the reliability of simulation results is examined.

Jan 1, 1993

By M. H. Marsden, R. A. Laybourne, J. D. Flint

Operations of the strip mine at Arnot Colliery are described, and the improved volumetric extraction of the in situ coal reserves that has been obtained by the application of strip-mining techniques is highlighted. An account is given of the major problems encountered during the early stages of the operation with particular reference to overburden removal. coal and parting handling, and transportation. The techniques used in dealing with the problems and the current degree of success in overcoming them are outlined.

Jan 1, 1980

By H. Knorre, A. Griffiths, R. Higgins, S. Gos

Hydrogen peroxide is gaining acceptance as a reagent for the treatment of mining effluents containing cyanide. In this paper some of the chemical and environmental aspects of treatment with hydrogen peroxide are discussed, and one way of improving the economics of the process is described. This is known as selective detoxification, which involves the oxidation of the less stable (cyanide) complexes while not affecting the more stable complexes, which contribute very little to the concentration of free cyanide or to the toxicity of the treated water.

Jan 1, 1987

By R. P. King

An Analytical Solution to the Batch comminution Equation R. P. King, Pr. Eng., B.Sc. (Eng.), M. Se. (Eng.), Ph.D. (Visitor). An analytical solution to the batch-grinding equation is presented in terms of the generalized hypergeometric series and the confluent hypergeometnc function. This solution is valid for selection functions that are describe~ piece-wise by functional forms of the type KOXB and by normalized breakage functions of the type B(x,x') = (x/x')x. These functional forms are sufficiently general to Include most practical cases. In particular, they can be used to describe selection functions that have a maximum.

By G. W. Holl, E. G. Fairon

A review of some aspects of shaft design by G. W. HOLL, Pr. Eng., Associate of the Mine Managers Association of South Africa (Fellow)- and E. G. FAIRON, Pr. Eng., F.S.A.I.E.E., M.I. Cert. M.E.E., M.I.Mech. E., (Visitor) The reasons for the choice of vertical shafts in preference to inclined shafts of comparable capacity are set out, and the conclusion that the former are superior in virtually all circumstances is substantiated. The shapes of vertical shafts sunk during the past sixty years are recorded, and the shapes of those sunk during the past decade are analysed. From this analysis it is clear that circular and elliptical (and quasi-elliptical) shafts are the shafts of the future and that the rectangular shape will conceivably become obsolete. The determination of the size of shaft is discussed and it is forecast that shafts of a diameter of 13 metres and over will probably be sunk without difficulty in the years to come. The depth of the shaft is determined intrinsically by the Mines and Works Regulations applicable to factors pf safety of winding ropes and the design of the winding system. The Blair winder is the most suitable winder for hoisting rock, men, and material from a depth of, say, 3000 metres on an economic basis. Tertiary shafts will, therefore, be unnecessary in future deep-level mining projects at the limit of depth now envisaged. A few other factors relating to shaft design are described.

By A. Ward, A. Smith, D. Harpley

Methods for the prediction of seepage quality from waste-disposal facilities are evaluated for input to the design of desalination treatment facilities. This is done by reference to a waste dump seeping into a near-surface aquifer, the contaminated seepage being collected by scavenger wells. As the quality of contaminated water intercepted by the wells will vary with both space and time, it is necessary for predictive methods to accommodate such variations. One-dimensional and two-dimensional predictive solute transport models are described and applied to the seepage and scavenger-well example mentioned above. The advantages and disadvantages, interims of overall applicability, data requirements, and possible accuracy, are described and discussed. While one-dimensional models have the advantages of speed, simplicity, and cost, the frequent requirement of prediction in both space and time necessitates more complex, two-dimensional simulation.

Jan 1, 1987

In a gold CIP/CIL circuit, adding new circuit water to a final tails thickener and then directing the thickener overflow to the head of the circuit significantly reduces the cyanide concentration at the TSF discharge spigot. The new water is used to dilute the final tails. The dilution and recycle of the tails in this manner may have the added benefit of reducing reagent consumption, in some cases to the point where the reagent savings justify the expenditure and Cyanide Code compliance is achieved at no extra cost. Potential circuit configurations and water recycles can be modelled by splicing a flowsheeting and thermodynamics package, such that changes to the composition of the water can be reduced to chemical speciation with a Gibbs free energy minimisation enabling a complete understanding of the circuit water chemistry.

Jan 1, 2007

In Chapter 1 we mentioned that up to three components are considered to represent the variability of regionalized variables : a deterministic component, a correlated component, and a random component. In Chapter 2 we considered some of the models based on the assumption of randomly distributed values: the random component was assumed to be the only one present. In Chapters 3 to 11, more general but also more complex models were described, based on the assumption that the values were correlated with the possible presence of random noise. In this chapter we introduce a model used to analyse non- stationary data, for which a deterministic component (or drift) must be assumed. This model will be used for estimation purposes, and the corresponding optimal linear estimation procedure is known as universal kriging. The theory of universal kriging is much more complex than the theory of kriging. Fortunately, in the majority of mine valuation problems the drift can be ignored and the simpler form of kriging can be used.

Jan 1, 1978

By C. R. Speers

The induced elastic stresses in the sidewalls of gold-mining tunnels at a depth of 4000 m in the Witwatersrand exceed the peak compressive strength of even the best-quality quartzite rocks. Laboratory tests measuring post-yield stress versus strain response show that brittle fracture occurs, followed by a loss in strength associated with strain-softening behaviour. Numerical modeling based on an assumed Mohr-Coulomb criterion fitted to the test results shows that large ongoing deformations of the sidewall occur, leading to total tunnel failure without adequate support. A methodology is presented to enable a quick assessment to be made of support requirements in terms of ground characteristic curves for numerically derived pressure versus displacement. From these curves, estimates can be made of the force levels for cable bolting and of the thickness and strength requirements for shotcrete linings. As an example of its application, the methodology is used in a comparison of the relative stability efficiencies of a square-shaped tunnel and a horizontal ellipse-shaped tunnel.

Jan 1, 1996

By J H. Sullivan

Contents Background information Locality of Kumba?s Iron Ore Mines Sishen?s Product Specifications Geological Description of boreholes Sample Preperation Block delineations Production Geology Process Laboratory information Turnover times reached Inter Laboratory Comparisons Quality control activities in lab Purpose of laboratory Results attained Standard samples Monitoring of processes with QA/QC standards Mean paired difference of duplicates Duplicate samples Conclusion

Jan 1, 2005

By A. J. Barrett

Backfilling at Vaal Reefs during the experimental phase has been carried out using cyclone-separated tailings which are transported underground hydraulically by means of a borehole. The selected tailings are piped from the borehole to the stope and then, after the addition of a flocculant, deposited in place via single or multiple nozzles. The successful performance of the backfill/stope system relies not only on the actual quality of the placed material, but also on the effective operation of stope filling. The success of stope filling relates to the complex, time- dependent interaction of backfill, stope and barricade materials, and the transport and placement procedures used. A comprehensive laboratory testing programme was carried out on backfill materials at Vaal Reefs in conjunction with the experimental stope- filling operation. The range of testing techniques corresponds to the requirements of each stage of the backfilling process. Where necessary, new or alternative techniques were sought during the course of the experiment to satisfy and facilitate better understanding of the different processes. These techniques comprise both routine quality control testing and research-oriented testing. The laboratory testing techniques appropriate to each stage of the backfill process are briefly discussed. This paper presents the main conclusions of the study and identifies areas for further research.

Jan 1, 1988