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By M. Bailey-McEwan

The application of refrigeration on deep South African gold mines is mostly achieved through the medium of chilled water which is produced in central installations either on surface or underground. The amount of refrigeration has been increasing rapidly over recent years, and the total installed capacity on all gold mines now exceeds 1000 MW(R), with annual running costs exceeding R100 million for electricity alone. Hence, there are strong incentives to design such installations for optimal cost-effectiveness. The duty required of these installations varies considerably, owing to daily and seasonal climatic changes and the varying nature of the water demand. It has long been recognized that a computer program to predict installation performance as a whole under any given conditions would be highly desirable. An interactive computer program, CHILLER, is described which enables the user to build an installation, consisting of any configuration of cooling towers, water storage reservoirs and packaged water chilling machines. Externally-dictated conditions such as the weather and chilled water demand must be specified, and all quantities under control of the installation, including internal water flow rates and compressor capacity regulators, must be set. The time-varying performance of the installation can then be simulated. Examples are given of the application of the program in the design of a new installation, and in evaluating the effect of any modifications to existing installations.

Jan 1, 1987

By S. A. Abdel Sabour

Strategic decisions in the mining industry are made under multiple technical and market uncertainties. Therefore, to reach the best possible decision, based on information available, it is necessary to integrate uncertainty about the input variables and model financial risk of the project?s merit measures. However, this provides few useful insights to decision-makers unless accompanied by modelling management responses to uncertainty resolutions. It is widely acknowledged that conventional decision-support methods based on static, no-change, discounted cash flow (DCF) techniques such as net present value (NPV) and internal rate of return (IRR) tend to provide inaccurate value estimates. This could mislead the strategic decision-making process and result in significant value losses. This paper aims to model financial risk related to uncertainty about market variables such as metal prices and foreign exchange rates. Other sources of risk that are related, for example, to geology and production costs are not considered in this work. The article outlines a flexible financial model that integrates uncertainty about market variables and management flexibility to react to uncertainty resolutions into mine project valuation using a real-options valuation technique based on Monte Carlo simulation. Significance of information generated from this simulation-based flexible valuation model to the strategic decision-making process is tested using an illustrative case study of a Canadian mining project. The project is a typical multi-metal, open pit mine that produces copper and gold. In this case, there are three uncertain market variables, which are: copper and gold prices and US$/CAN$ exchange rate. Financial valuations are carried out using both the conventional static DCF method and a flexible real-options model. In the flexible model, management flexibility to decide whether to go ahead with the next expansion or terminate production operations is integrated. Results show how the flexible financial model can enhance the decision-making process.

Jan 1, 2009

By P. J. How, T. O. Hagan, M. F. Handley

Inelastic deformation of highly stressed rock in deep mines needs to be quantified in both time and space. Since most deformation occurs by shear, continuous monitoring of discontinuities in the rock from boreholes holds promise. The casing. Al interpretations of shear movements are based on a simple relation between shear displacement and the resulting change in tilt of the sensor. A prototype has been constructed and has undergone laboratory trials with satisfactory results. Underground trials will commence shortly. The instrument as designed has the potential for other applications, both in the civil-engineering and mining industries. paper describes an instrument that is both cheap and reliable, and capable of monitoring such shear movements continuously. The principle of operation is based on two capacitive gravity sensors mounted orthogonaly to each other in a sealed aluminum

Jan 1, 1988

By T. Puhakka

Simulation is a way to obtain quickly today future information on how planned systems will most likely behave in various selected situations. This information may then be used to optimize the system and its components and maximize the performance and output. Simulation is a way to fine-tune the layout, match the mobile fleet and optimize the schedule and the way of working to meet the desired production requirements. Simulation provides a glimpse of the upcoming operation, ‘future today’ and helps to predict its restrictions and sensitivity to various aspects. OptiMine™, the Sandvik Tamrock Corp. and CyberCube Oy developed simulation tool is designed to simulate underground rock flow and match suitable technology with various layout options. This tool can be used to view what-if situations and determine what kind of impact mastered changes have to production. The findings of critical points in the layout and working procedures at an early stage of a new mine can help to optimize the layout and material flow. OptiMine™is modular based simulation tool that combines the supplier machine knowledge and traffic guidance with mine operational know-how and mine environment. It is developed to work in a way that an effect of an individual incident, such as the effect of one additional turn in a continuous loading cycle to the daily capacity can be identified. The reported output can be used for economical impact evaluation of selected options. This paper discusses the use of simulation in general and the way the OptiMine™ simulation tool operates and how it may be used for operation, technology and material flow optimization.

Sep 1, 2001

By J. R. de Wet

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. Flowsheet development and the associated metallurgical testwork 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 A. Hinde, M. H. Moys

Tailings from metallurgical plants, when deslimed with hydrocyclones, provide a valuable source of material for the backfilling of mines. The effectiveness of this material as a support medium is a sensitive function of its particle- size distribution and water content. It is therefore important that the hydrocyclone-classification plants used to prepare the backfill are operated efficiently, and that the effects of feed disturbances on the composition of the backfil are minimized. This paper addresses the problem of the design, control, and optimization of classification plants to satisfy this need. The development of a computer program to simulate the dynamic behaviour of a hydrocyclone circuit of any given configuration is described. The use of the simulator to investigate the relative performance of conventional and innovative control strategies for single-stage and two-stage circuits is discussed in depth. The results of simulation studies are presented that indicate there is considerable scope for improving the performance and cost-effectiveness of backfill-classification plants.

Jan 1, 1991

P.W.D. ROSTER OF CONSULTING ENGINEERS (Extract from a letter from the Secretary for Public Works) In recent years a large number of professional engineers has entered the consulting field. Although the names of most of these have been placed on the Department's roster of consulting engineers either as a result of representations made by the South African Association of Consulting Engineers or by applying direct to the Department there are still some who seem to think that canvassing through an influential person is necessary to obtain commissions from the Department. The Department's roster is open to all registered professional engineers who are suitably experienced to undertake consulting work and commissions are awarded strictly on merit. I shall appreciate it, therefore, if registered professional engineers who wish to be considered for commissions by the Department could be advised that they must apply, in the first instance, to be placed on the Department's roster. On receipt of such an application a questionnaire listing all the information required by the Department will be forwarded to the applicants for completion and returning to the Department for record purposes. All names which appear on the roster are taken into account when a commission has to be awarded, due consideration being given to factors such as geographical position, seniority, capability and compatibility. AMERICAN SOCIETY OF MINING ENGINEERS 1970 FALL MEETING AND EXHIBIT The Secretary for Commerce has passed to us a letter received from the American Society of Mining Engineers, reading as follows: "We would be delighted to have South Africa attend our meeting next year and to exhibit some of their mining equipment in our Technological Information Exchange. The 1970 SME Fall Meeting and Exhibit will be held in St. Louis, Mo., October 21-23, 1970, at the Kiel Auditorium. The AIME WorId Conference on Lead & Zinc Mining and Metallurgy will be an integral part of our meeting-and an added incentive to attend. It should be understood that we discourage the showing of actual mining equipment and encourage the manufacturers and suppliers to send their engineers to man the booths. We hope that the exhibits will endeavour to put across their story by means of photographs, drawings, models and literature, rather than by display of prototypes of the actual equipment. We will be happy to welcome manufacturerers from South Africa as well as the mining engineers who, from time to time, have registered at our meetings." For further particulars, interested parties may write to the Society of Mining Engineers, 345 East 47th Street, New York, N.Y. 10077, D.S.A.

By D. F. Williams

The modelling, simulation, and design of processes for the recovery of gold from solution by absorption on carbon require the combination of a suitable rate expression with a description of the flow conflguration of the system. By the use of a suitable rate expression from the literature, methods are presented for the design of multi-stage countercurrent absorption systems corresponding to the commonly used carbon-in-pulp and carbon-in-column contacting systems. The sensitivity of the recovery to various design parameters is illustrated. These results have important implications in the choice and design of equipment.

Jan 1, 1985

The rising tide of environmentalism has adversely affected many mineral producers, but it has also provided them with a number of opportunities for mineral applications. These markets are as diverse as water treatment, waste disposal, and flue-gas desulphurization. Whilst legislation is forcing up the industry's environmental standards, the advent of environmental management provides an opportunity for producers to display its 'green' credentials. The picture painted of the extractive industry by environmentalists is undeservedly black, because the more efficient a producer is, the more effectively that producer conserves the very resources he exploits. The 1993 IM Forum examined these issues and how they affect the mineral producer, and this publication comprises the papers presented at that meeting.

Jan 1, 1995

The peak in Sulphur price late 2008 caused again intensified investigation into the decomposition of sulphates and spend acid. One option is the recycling of sulphur from spend acid, which already started more than 40 years ago in the field of spend acid from organic processes in refineries and acrylic glass manufacturing. Since this acid couldn't be neutralized and discarded due to high organic contents, another source of SO2 to produce sulfuric acid is the decomposition of metal sulfates. The decomposition of metal sulfates was investigated at the next peak in Sulphur price in the 80?s. The first major scale pilot tests and studies of gypsum decomposition were carried out for clients in Florida. The decomposition of gypsum was quite often mainly influenced by the strategic decision of some countries to get own and independent acid production. In other cases the industry doesn?t have enough space to dump the gypsum. Therefore the company was also forced to convert the gypsum into ?saleable? products to avoid these residues. Other projects were made for the recycling of iron-sulfates from the pigment industry. The motivations for these projects were not only given by acid price. For the German pigment industry it was no longer permitted in the 80?s to dump the iron sulphate residues into the sea. These regulations forced the industry to develop new technology, which allows converting of the FeSO4-residues into iron oxide and acid. Therefore economical and mainly environmental factors influenced the decision of the companies to develop and to build these plants. Beside the above mention iron- and calcium-sulphates many other process exist, which produce metal sulphates as an intermediate product. These cases are not forced by environmental or strategic factors. In cases like Ni, Co or Mn-decomposition the main product of the plant is treated in the decomposition plant and later on used as ferrous-alloys. These final products are higher in price compared to e.g. CaO, which exclude the high-energy consumption for the endothermic chemical decomposition reaction. The reaction of SO2 generation based on acid or sulfate decomposition takes place in the range of 1000°C. The energy demand of the endothermic reaction is considerable and leads due to the high fuel-combustion off-gas stream to a diluted SO2 gas. Energy prices are usually increasing at the same time like sulphur. Sulphuric Acid based on decomposition is therefore more expensive than as acid based on sulphur combustion. The paper describes fluid bed technology and possible process concepts for decomposition plants. Additionally the thermodynamic background of the decomposition process and the main influence factors are provided to receive a better understanding of this technology.

Jan 1, 2009

The peak in Sulphur price late 2008 caused again intensified investigation into the decomposition of sulphates and spend acid. One option is the recycling of sulphur from spend acid, which already started more than 40 years ago in the field of spend acid from organic processes in refineries and acrylic glass manufacturing. Since this acid couldn't be neutralized and discarded due to high organic contents, another source of SO2 to produce sulfuric acid is the decomposition of metal sulfates. The decomposition of metal sulfates was investigated at the next peak in Sulphur price in the 80?s. The first major scale pilot tests and studies of gypsum decomposition were carried out for clients in Florida. The decomposition of gypsum was quite often mainly influenced by the strategic decision of some countries to get own and independent acid production. In other cases the industry doesn?t have enough space to dump the gypsum. Therefore the company was also forced to convert the gypsum into ?saleable? products to avoid these residues. Other projects were made for the recycling of iron-sulfates from the pigment industry. The motivations for these projects were not only given by acid price. For the German pigment industry it was no longer permitted in the 80?s to dump the iron sulphate residues into the sea. These regulations forced the industry to develop new technology, which allows converting of the FeSO4-residues into iron oxide and acid. Therefore economical and mainly environmental factors influenced the decision of the companies to develop and to build these plants. Beside the above mention iron- and calcium-sulphates many other process exist, which produce metal sulphates as an intermediate product. These cases are not forced by environmental or strategic factors. In cases like Ni, Co or Mn-decomposition the main product of the plant is treated in the decomposition plant and later on used as ferrous-alloys. These final products are higher in price compared to e.g. CaO, which exclude the high-energy consumption for the endothermic chemical decomposition reaction. The reaction of SO2 generation based on acid or sulfate decomposition takes place in the range of 1000°C. The energy demand of the endothermic reaction is considerable and leads due to the high fuel-combustion off-gas stream to a diluted SO2 gas. Energy prices are usually increasing at the same time like sulphur. Sulphuric Acid based on decomposition is therefore more expensive than as acid based on sulphur combustion. The paper describes fluid bed technology and possible process concepts for decomposition plants. Additionally the thermodynamic background of the decomposition process and the main influence factors are provided to receive a better understanding of this technology.

Jan 1, 2009

By T. F. Cho, B .. O. You, K. S. Yoon, K. S. Won

Discontinuity Orientation Measurement (DOM) drilling system capable of retrieving the reference line-marked core log, which can be used for determining the relative positions and orientations of discontinuity planes along the borehole axis, has been developed. Accuracy of the borehole joints data measured from the reference-lined core and, eventually, the significance and applicability of DOM drilling system for site exploration are verified by comparing with the spatial characteristics of joints investigated by implementing borehole image-taking instruments in the same borehole. Enhancement of boring efficiency has been also confirmed by performing twin drilling operations, one with DOM drilling system and the other with a conventional drilling machine equipped with D-3 core barrel, on two neighbouring sites of 5 m apart. Ein DOM(Diskontinuitätsorientierungsmessung)-Bohrsystem, das durch Grundlinien markierte Bohrprobelog extrahieren kann und die relativen Lagen und die Orientierungen der sich im Bohrloch verbreitenden Flächen bestimmen kann, ist entwickelt worden. Die Wichtigkeit des DOM-Bohrsystems und dessen Anwendbarkeit auf die Erforschung auf dem Bohrplatz werden dadurch bewiesen, dass man die Genauigkeit der Daten der Bohrlochsspalte, die durch die die Grundlinie zeichnende Bohrprobe gemessen werden, mit dem räumlichen Eigenschaften der Spalte vergleicht, die durch die Bildaufnahme des gleichen Bohrlochs nachgeforscht werden. Un system de sondage, Discontinuity Orientation Measurement (DOM), capable de récupérer des carottes markés en une ligne de référence a été dévelopé. Il peux être utilisé pour déterminer les positions relatives et les orientations des plans de discontinuité le long de l’axe de trou de sonde. Leur signification et applicabilité pour une caractérisation de site est verifiée par une comparaison de la précision des données a propos des joints mesurés a partir des carottes markés et les carac-téristigues spatiales des joints enquêtés par le camera de sondage

Jan 1, 2003

By C G. Robinson, B. K. Loveday, J. C. Paynter

"A method of optimizing the design of a processing plant has been developed which minimizes capital and operating costs for average stripping ratios and ore characteristics. Models were developed to describe the operating characteristics and costs involved in various operations such as up-grading, leaching and solid-liquid separation.The options available in up-grading policy and the relation between the cut-off grade and the costs incurred subsequently in the treatment of the ore formed the basis of the optimization. To arrive at an optimum plant configuration and a set of operating parameters, the interrelation between grinding size, leaching temperature, leaching time, and various plant recycle options was investigated."

Jan 1, 2014

By H. -U. Lim, C. -H. Kim

The sixth underground pumped powerhouse cavern is under construction now in Korea. For the stability analysis of the five underground powerhouses, finite element method was used. For this analysis, in-situ rock stresses were measured by overcoring method and horizontal to vertical stress ratio was calculated 1.07-1.32 at four sites. Rock mass strength and elasticity were assumed from intact rock properties. The ratio of elasticity of rock mass was 0.16-0.55 of intact rock core elasticity. In general, elasto-plasticity with Mohr-Coulomb failure criterion was applied and the input cohesion and internal friction angle were approximately 0.12-0.22, 0.6-0.87 of intact rock strength parameters, respectively. Der sechste Untergrund-gepumpt-Powerhouse-Cavern ist jetzt im Bau in Korea. Für die vergan-gene Stabilitätsanalyse des fünf unterirdischen Powerhouses in Gebrauch wurde ein begrenztess Elementsmethode benutzt. Für die Analyse wurden In-Situ Felsenspannungen von overcoring Methode gemessen und Horizontale zu senkrechtem Spannungsverhältnis waren als 1.07-1.32 an vier Stellen kalkuliert. Felsenmassenkraft und Elastizität wurden von unversehrtem Felsenei-gentümern angenommen. Das Verhältnis der Elastizität von Felsenmasse war 0.16-0.55 von un-versehrter Felsenkernelastizität. Im allgemeinen wurde Elasto-Plasticity mit Ausfallskriterium des Mohr-Coulombs verwendet. Die Eingabebindekraft und die innere Reibungswinkel waren unge-fähr 0.12-0.22, 0.6-0.87 von unversehrtem Felsenkraftsparametern, jeweilig. En Coree, la sixieme centrale souterraine de la pompe d'accumulation dans la caverne est en construction. La methode d'element fini a ete utilisee pour analyser la stabilite de cinq dernieres centrales en service. Dans cette analyse, la reaction de la roche sur place etait mesuree par la methode d'overcoring et celle du rapport horizontal-vertical etait calculee de 1.07-1.32 en quatre places. L'intensite et l'elasticite de la masse de roche ont ete estimees de la roche intacte. Quant a l'elastic-ite, sa masse de roche etait 0.16-0.55 fois que celle de la roche intacte. En general, elasto-plasticite avec le critere de defaut Mohr-Coulomb etait utilisee et sa cohesion d'energie et son angle de friction interieure etaient supposees respectivement 0.12-0.22, 0.6-0.87 fois que la parametre de l'intensite de roche intacte.

Jan 1, 2003

By E. L. Thyse, P. Bepswa

The Western Cape Mineral Processing Facility (WCMPF) is a collaborative educational initiative between the Department of Process Engineering at the University of Stellenbosch and the Chemical Engineering Departments at the University of Cape Town and the Cape Peninsula University of Technology. The primary objective of the WCMPF is to facilitate the education, development and graduation of suitably qualified engineering graduates and diplomats for the mining and mineral processing industries. In recent years the WCMPF has embarked on a number of initiatives aimed at improving the quality of mineral processing education which include, more importantly the introduction of novel ?end to end? or ?integrated? practicals. The practicals are developed around a specific mineral theme or route, which more than often includes the development of several new pilot plant practicals demonstrating key unit operations or processes in the selected mineral theme or route. The most recent mineral processing pilot plant practical programme is developed around the beneficiation of heavy mineral sands. The programme consist of the following developed pilotplant practicals: the online electrostatic separation of free flowing mineral sands using a Roche Mining Carrara high tension roll separator incorporating a Blue Cube Systems MQi in-line mineral quantifier; the production of titania-rich slag and pig iron from the smelting of ilmenite and anthracite in a 60 kW direct current (DC) plasma arc furnace as well as the mineralogical characterization of the feed and products; the continuous closed-circuit ball milling and screen classification of titania-rich slag. This paper illustrates the important role of a well-designed heavy mineral sands beneficiation pilot plant practical programme in facilitating the education and development of suitably qualified personnel for the mining and mineral process industries.

Jan 1, 2007

By D. W. Boydell, E. B. Viljoen

A flowsheet incorporating rotary-drum filtration for the solid-liquid separation step, followed by solvent extraction for uranium purification, is used as a standard against which four flowsheets are compared. These flowsheets employ either counter current decantation or belt filtration for solid-liquid separation, and either solvent extraction or continuous ion exchange plus solvent extraction for the purification step. Sales revenue, taxation, capital expenditure, and operating costs are estimated. These factors are taken into account in the calculation of an incremental net present value for each circuit by the discounting of cash flows at 25 per cent per year over a projected life of 15 years. For the material used in these examples, the highest net present value results from the circuit that employs belt filtration followed by continuous ion exchange and solvent extraction.

Jan 1, 1978

By J. Githiria, C. Musingwini

"Cut-off grade is a decision-making criterion often used for determining the quantities of material (ore and waste) to be mined, ore processed, and saleable product. It therefore directly affects the cash flows from a mining operation and the net present value (NPV) of a mining project. A series of different cut-off grades that are applied over the life of mine (LOM) of an operation defines a cut-off grade policy. Due to the complexity of the calculation process, previous work on cut-off grade calculation has mostly focused on deterministic approaches. However, deterministic approaches fail to capture the uncertainty inherent in input parameters such as commodity price and grade-tonnage distribution. This paper presents a stochastic cut-off grade optimization model that extends Lane’s deterministic theory for calculating optimal cut-off grades over the LOM. The model, code-named ‘NPVMining’, uses realistic grade-tonnage realizations and commodity price distribution to account for uncertainty. NPVMining was applied to a gold mine case study and produced an NPV ranging between 7% and 186% higher than NPVs from deterministic approaches, thus demonstrating improved project value from using stochastic optimization approaches. Background on cut-off grade calculation and optimizationCut-off grade is a decision-making criterion that is generally used in mining to distinguish ore from waste material. Consequently, it is used to determine the quantities of material (ore and waste) to be mined, ore processed, and saleable product. A series of different cutoff grades that are applied over the life-ofmine (LOM) of a mining operation defines the cut-off grade policy for that particular operation. The cut-off grade therefore directly affects the cash flows to be produced and the net present value (NPV) of a project at the mine planning or feasibility study stage."

Mar 1, 2019

By J. A. L. Napier

One of the most important characteristics of tabular mine stress analysis is the need to represent the complex evolution of mining face positions and the accompanying induced stress changes in the rock mass. Integration of seismic activity with numerical modelling requires flexible and efficient solution schemes in which both off-reef damage and large-scale fault slip can be effectively represented. A new approach is investigated in which the stope closure and ride variables can be found using a moving least squares estimator. Some advantages of this approach over traditional element-based tessellation schemes are identified. At the same time, shortcomings of this method are noted when the displacement discontinuity variable is approximated by a polynomial shape function. Difficulties and possible solutions to the shape function formulation near excavation edges are discussed. Une des caractéristiques les plus importantes de l’analyse des contraintes minières tabulaires est la nécessité de représenter la complexe évolution des positions du front de taille et des changements concomitants des contraintes occasionnées dans la masse rocheuse. L’intégration de l’activité sismique avec la modélisation numérique requiert des projets souples et efficaces qui permettent la représentation des dommages hors-filon et des glissements de faille à grande échelle. Une approche nouvelle est étudiée qui permet de trouver la fermeture de la taille et les variables de montage en utilisant un estimateur par les moindres carrés mobile. Certains des avantages de cette approche sur les traditionnels projets basés sur une structure en mosaïque sont identifiés. En même temps, les défauts de cette méthode sont notés lorsqu’on calcule la variable de discontinuité du déplacement approximativement par une fonction de forme polynomiale. Les difficultés et solutions possibles à la formulation de la fonction forme près des bords d’excavation sont discutés. Eine der wichtigsten Charaketeristika der taublaren Grubenspannungsanalayse ist die Notwendigkeit, die komplexe Entwicklung der Abbaupositionen und der damit verbundenen induzierten Spannungsänderungen der Gesteinsmasse neu vorzulegen. Die Integration der seismischen Tätigkeit mit einem numerischen Modell erfordert flexible und effiziente Lösungsschemata, in denen sowohl Schäden ausserhalb des Riffs als auch Verwerfungen großen Ausmaßes effektiv dargestellt werden. Ein neuer Vorstoß wird untersucht in welchem die Strossenschliessung und Schneisenvariablen unter Verwendung des Schätzwertes der kleinsten quadratischen Abweichungen (Gaussscher Schätzwert) gefunden werden. Einige Vorteile dieser Annäherung im Vergleich zu der traditionellen Element-basierenden Tessellation sind identifiziert. Gleichzeitig werden Unzulänglichkeiten dieser Methode vermerkt, wenn die Verschiebungsdiskoniuitätsvariable durch eine polynomische Formfunktion angepaßt wird. Schwierigkeiten und mögliche Lösungen zur Formfunktionsformulierung nahe Exkavationsrändern werden besprochen.

Jan 1, 2003

By P. R. Jochens, D. D. Howat, M. S. Rennie

The slags arising from ferrochromium plants were simulated by additions of CaO and Fe2O3 (6 per cent each), Cr2O3 (7 and 12 per cent), and Fe2O3 and Cr2O3 together (6 and 12 per cent respectively) to slags in the MgO-Al2O3-SiO2 system. These additions were made to slags having an SiO2 content of 45 per cent and an MgO-to-Al2O3 ratio of 4 to 3 or 3 to 4. The effect of these oxide additions on the liquidus temperatures, electrical conductivities, and viscosities was determined. The additions of CaO and Fe2O3, although having little effect on liquidus temperatures, decreased viscosity and increased electrical conductivity. The addition of Cr2O3 raised the liquidus temperatures considerably, and tended to decrease viscosity in the temperature range 1 700 to 1 800°C and to increase electrical conductivity.

By H. M. Friede, R. H. Steel

Notes on Iron Age copper-smelting technology in the Transvaal by H. M. FRIEDE, Ph.D. and R. H. STEEL (Visitors) Earlier reports on Iron Age copper metallurgy and copper-smelting techniques in the Transvaal are surveyed, and a description and tentative classification of the copper furnaces are given. The analyses of furnace slags and sherds of glazed crucibles from archaeological sites of the Transvaal and the neighbouring Orange Free State pro. vide evidence of copper smelting there in Iron Age times. . An investigation conducted by the Department of Archaeology of the University ofthe Witwatersrand provided information on the details of furnace construction and smelting processes, on the composition of the materials used and produced, and on the making and handling of tools and accessories, such as bellows and tongs, needed by Iron Age smelters. Three models (the KaondejVenda furnace, the Rooiberg crucible furnace, and the Uitkomst furnace) were constructed and operated as a demonstration of Iron Age copper smelting as it was practised in the Transvaal.

Jan 11, 1975