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By L. Woollacott, R. P. King

This paper presents data collected from full-scale plants in order to verify the predictions of a new simulator of CIP or CL operations. Good agreement was found between the experimental data and the simulator predictions. The simulator is able to predict the effects of many of the complex operating phenomena in GIP and CL plants that previous simulation techniques could not describe. This is illustrated by predictions of how factors, such as the manner of carbon transfer, concurrent leaching, and gold loading on eluted carbon, can affect the performance of an adsorption plant.

Jan 1, 1990

By M. Akyüzlü

The equilibrium between carbon-saturated Fe-Cr-Si-C alloys and SiO2-CaO-MgO-A2O3-CrO2-FeOy slags was studied under atmospheres of argon and carbon monoxide at temperatures of 1500 and 1600°C. The equilibrium distribution of chromium, silicon, and iron between the slag and the metal phases was determined for different compositions of both phases under different atmospheres and temperatures. It is shown that silicon transfer from the slag to the metal increases with increasing temperature, decreasing carbon monoxide partial pressure, decreasing carbon content of the metal, increasing chromium-to-iron ratio of the metal, increasing silica content of the slag, and decreasing lime-to-alumina ratio of the slag. Some activity calculations were made for the experiments conducted at 1600OC in a carbon monoxide atmosphere. It is also shown that a decrease in the iron content and an increase in the slag basicity decrease the chromium content of the slag. A major proportion of the chromium present in the slag was found to be in the divalent state under the highly reducing conditions prevailing in the experiments. The chromous capacities of these slags were calculated and were found to decrease with increasing basicity.

Jan 1, 1992

By N. Saldía, C. Riveros, R. Hills, S. Barrera

The transport of tailings composites provided by different sources is a field of study where a limited amount of research has been conducted. Nevertheless, such systems are important sources of operational difficulties, especially in the case of high clay content tailings. The case presented in the present paper consists of a free surface flow pipeline transporting a composite of two different tailings with high clay content. It has presented operational difficulties such as partial blockages and upstream box and air intake overtopping events. In the present paper, the causes of these difficulties are identified. These include lack of complete mixing of the different tailings, multi-layered flow with low velocity and high yield values with high frictional losses. The pipeline characteristics and performance are analysed in three stages: design, initial operation and enhanced operation, the latter accomplished by means of increasing turbulence in the box located upstream from the pipeline. The last section of the pipeline and another distribution pipeline system located downstream from the pipeline have performed well. The cause of different behaviour of both systems is also assessed.

Jan 1, 2007

By L. M. Falcon

Cassiterite is considered to be the only economically significant tin mineral in the earth's crust, and in its purest form has a tin content of 78,6 per cent. South Africa has limited deposits of the mineral, and by its exploitation contributes about 2 per cent of the world's production. This paper gives a brief history of tin mining in South Africa, which dates back almost 3000 years. Over the intervening years, many tin-mining operations have flourished and as quickly disappeared. At present there are only three tin mines in operation, and a description is given of the methods of mining, concentrating, and smelting that are used. The properties and uses of tin are listed, together with relevant statistics.

Jan 1, 1985

By A. García-Gutiérrez, A. Aragón-Jerónimo, R. Salazar-Mendoza

A theoretical analysis of a two-region solid-liquid flow system in horizontal pipes is presented, which considers a stationary bed of drill cuttings as a porous medium (-region) below of a two-phase dispersed flow (-region).The method of volume averaging was applied in this study to derive a rigorous mathematical model in which each variable is precisely defined. This model includes the volume-averaged transport equations for both the two-phase dispersed flow and the porous medium regions and terms from a macroscopic forces balance. The solution of the two-region model allowed evaluation of the behaviour of pressure gradient as a function of velocity, total volume fraction of cuttings and the relationship of the height of the stationary bed and pipe diameter. The solution is based on a backward finite difference explicit scheme. The simulated physical system is a pipe of 4.135 m in horizontal length and 0.0508 m in diameter. A one-dimensional, mesh-centred grid, consisting of 100 nodes, is used. The numerical results were compared with experimental data on slurry flows and a good agreement was found. Keywords: two-phase, cuttings transport, solid-liquid flow, drilling modelling, volume averaging.

Jan 1, 2007

By S. Pathak, B. Nilsen

Abstract: In recent years, probabilistic approach with the calculation of probability of failure instead of a factor of safety against failure is emerging in practice. The main objective of the paper is to discuss a probabilistic approach in rock slope stability analysis for Himalayan conditions. Due to the fragile geology brought about by the tectonic movements along the hill slopes, dramatic variations of the topography and intensive surface runoff during every monsoon season, serious slope failures occur frequently in Himalayan region. Slope failures have also been triggered by seismic activities. The probabilistic approach is applied to stability analysis for a road cut along the Desander back slope of the Kali Gandaki hydropower project in Nepal. It is concluded that the probability approach offers a more accurate grasp of the actual condition than any factor of safety. Zusammenfassung: In den letzten Jahren ist es mehr gewöhnlich geworden, ein stochastisches Verfahren und eine Berechnung von der Wahrscheinlichkeit eines Zusammenbruchs statt einer Berechnung von Sicherheitsfaktoren zu verwenden. Das Hauptziel dieses Artikels ist das stochastische Verfahren in Stabilitätsanalyse von Gebirghängen, welches an Himalayische Verhältnisse angewandt worden ist, zu diskutieren. Wegen der spröden Geologie die durch tektonische Bewegungen entstanden ist und den dramatischen topographischen Variationen sowie viel Oberflächenwasser während des Monsuns, kommen in der Region des Himalayas oft mehrere erhebliche Abhangszusammenbrüche vor. Abhangszusammenbruche ist auch von seismische Aktivität ausgelöst worden. Das stochastisches Verfahren ist auch benutzt worden, um die Stabilität von einem Wegschnitt in dem Desander Gebiet von dem Kali Gandaki Wasserwerk-Projekt zu analysieren. Die schlussfolgerung ist, dass die Ergebnisse eines stochastisches Verfahren die wirkliche Verhältnisse eines Abhangs besser beschreibt als der Sicherheitsfaktor. Résumé:- Ces dernières années, une approche probabiliste basée sur le calcul d’une probabilité de cassure au lieu d’un facteur de sécurité préventif d’une cassure est de plus en plus utilisée. L’objectif principal de ce papier est de discuter une approche probabiliste de la stabilité de versants rocheux en himalaya. Due à la fragile géologie causée par les mouvements tectoniques sur les versants de collines, aux dramatiques variations de topographie, ainsi qu’au lessivage intense du relief à chaque mousson, de sérieux glissements de terrains se produisent fréquemment en Himalaya. Les glissements de terrain sont aussi déclenchés par l’activité sismique. Cette approche probabiliste est appliquée aux analyses de stabilité d’une section de route le long du versant arrière Desander du projet « hydropower » du Kali Gandaki au Népal. On en conclut que l’approche probabiliste offre une estimation plus précise des conditions actuelles que n’importe quel facteur de sécurité.

Jan 1, 2003

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

For the past 12 years, the Universities of Stellenbosch and Cape Town have hosted an annual symposium to discuss research topics in Minerals Processing. Since 1987, this meeting has been held under the auspices of the Western Cape Branch of the South African Institute of Mining and Metallurgy, and has enjoyed much national and international support. In 1993, in place of the usual Symposium, the Branch and Universities collaborated with CSM Associates Ltd and Minerals Engineering Journal is organizing the international Minerals Engineering '93 Conference in Cape Town.

Jan 1, 1993

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 M. G. Adamson, B. D. H. Phillips

This paper describes a procedure that has been found successful in the planning and execution of practical trials of mechanized-mining equipment. The procedure is illustrated by reference to development trials of a rockslotting machine with pneumatic or hydraulic drills that were conducted on South African gold mines.

Jan 1, 1978

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 Gordon Chunnett, Ron Sheets, David Grant

[Power-Point Presentation]

Jan 1, 2005

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

By S. M. Spottiswoode, A. J. Jager, N. C. Gay, J. A. Ryder

The South African mining industry is at present planning to extract orebodies at depths of up to 4 km. To do this cost effectively and, at the same time, ensure safe working conditions for mining, the personnel will require both the development of new strategies and the implementation of current rock-engineering technological developments on a wide scale. This paper covers most of the technological developments likely to be required for mining at very high stresses, but it is clear that improved regional support systems will need to be developed to ensure defective stability of the rockmass during mining operations. Similarly, it is clear that improved strategies for mining in large-scale geologically disturbed areas, where slip on faults or dykes can result in wide-spread rockburst damage, will have to be addressed

Jan 1, 1995

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 G. H. Morton

The tenth international symposium on the application of computer methods in the mineral industry (APCOM) was held in Johannesburg in April; the first time it had taken place outside North America. In the technical sessions fifty-seven papers were presented, providing a review of current work and including some important original contributions. These papers and a full account of the discussion at the symposium will soon be published in a single volume. The Technical Programme The first session of the symposium included an opening address given by Mr J. W. Shilling, President of the Chamber of Mines of South Africa, and a keynote address by Mr K. F. Lane of the Rio Tinto Corporation Limited. Mr Shilling spoke about the history of the South African mining industry and about some of the work of the Chamber of Mines. He stressed the importance of the symposium in familiarising those in mining with computer applications, and expressed his hope that it would stimulate and inspire scientists and engineers in the effort to develop safer and more economic methods of mining. Mr Lane, talking about economic and financial modelling, gave a fascinating account of the experience of RTZ over the last twelve years. In a very honest appraisal of the substantial progress that had been made, he confessed some disappointment not only in the cost and

This paper illustrates the application of numerical modeling methods, in conjunction with limit-equilibrium techniques, to the location of critical slip surfaces in slope-stability problems. Initially, the Spencer slice-based method of analysis is introduced, together with a dynamic-programming algorithm for slip-surface location. This limit-equilibrium method is assessed critically through the use of an illustrative problem. The technique is then extended to locate the critical slip surface for a similar slope, but with more complex constitutive and yield relationships for the material comprising the slope. To this end, the use of the stress field generated from a finite-difference program, together with a dynamic-programming search routine, is presented as an advanced technique of slope-stability analysis for engineers.

Jan 1, 1993

There are presently no suitable underground mine production scheduling optimisation models available for application to sublevel stope mining. Scheduling underground production for maximum return is therefore still a manual process, which generally involves scheduling production from the next available highest cash flow stope within the operational constraints of the project. In most mining operations, the scheduling problem is too large and complex to guarantee truly optimal results through manual scheduling. This paper reviews some general optimisation studies that have been proposed for underground hard rock mining. Furthermore, an example of a mixed integer programming model is presented for a small conceptual sublevel stoping operation. Comparative results of a schedule generated by a mixed integer programming (MIP) production scheduling model and a manually generated model on a nine stope example is presented. Results indicate that the potential benefits of the MIP production scheduling model for the purpose of maximising NPV are significant. Finally, a new constraint was formulated to limit multiple exposures of fill masses for use in an existing MIP production scheduling model. Testing of the formulation took place on the central stope of the nine stope example, which showed that the formulation performed its task without breaking other operational constraints.

Jan 1, 2007

By P. Kind

Design criteria and recent developments in large-capacity Wemco flotation cells by P. KIND, Ph.D. (Clausthal), B.Sc. (Visitor) The scaling-up of the large flotation cells that have been developed during the past few years has been based on hydrodynamic considerations and has resulted in a 500 ft3 cell unit. Plant results on a porphyry copper ore show that the 500 ft3 unit is equivalent to the previously used 300 ft3 model.. . Plant tests on the use of 300 ft3 flotation cells for the recovery of phosphate, particularly from the coarse size fractions, are also described.

Jan 3, 1976

By R. Hemp

This paper describes in broad outline the development of a computer programme for determining the effects of changes in various factors in the condenser water circuit on the operation of a cooling plant. The programme is used to obtain design figures which result in minimum total power consumption. This was done for a range of different upcast air quantities, and the implications of low air quantities for heat rejection are discussed.