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By A. S. Macfarlane

The introduction of new technology into mining operations is seen as a strategic necessity by many mining companies, in order to improve safety and to improve operational effectiveness. Many attempts have been made in recent years to introduce new technologies into mining operations in southern Africa. Amongst these are noteworthy successes, as well as some disappointing failures. Often, the reason for failure does not lie with the technology itself, but with the work system into which the technology is introduced. Such failures may come with a significant opportunity cost, and have a detrimental effect on future development, simply because the system has not been adequately engineered, and the risks have not been adequately assessed and managed. This paper examines the reasons for such failures, and proposes a methodology to be followed to ensure successful and sustainable implementation of new technologies, such as to reduce technical and financial risk to the company, and to energize the workforce into ensuring the initial objectives of the project are met. The paper also focuses on the application of appropriate technology, and the development of technological applications which are commensurate with the level of development of the work environment into which it is introduced. The paper therefore focuses on the application of risk management, change management, systems engineering and feasibility analysis as being key elements of a successful and holistic technology implementation programme.

Jan 1, 2001

By J. H. Potgieter

The method used to assess the reactivity of lime was evaluated to gauge it usefulness as a quality control tool. The effect of particle sizes, different lime and water masses for a fixed s:l ratio and the same for various s:l ratios on the reactivity values obtained, were investigated. An attempt to introduce the amount of grit produced during the slaking reaction as an additional measure of limeís quality and reactivity, proved to be unsuccessful. It was also found that the relative amount of lime slaked during the different tests was independent of the reactivity value of the lime. The investigation confirmed the usefulness of the accepted test procedure as are liable method to measure the reactivity of lime, despite various reservations expressed from a theoretical point of view.

Jan 1, 2002

To the members of The South African Institute of Mining and Metallurgy We have audited the annual financial statements set out on pages 239 to 245. These financial statements are the responsibility of the Institute?s Council. Our responsibility is to report on these financial statements. We have conducted our audit in accordance with generally accepted auditing standards. These standards require that we plan and perform the audit to obtain reasonable assurance that, in all material respects, fair presentation is achieved in the financial statements. The audit included an evaluation of the appropriateness of the accounting policies, an examination, on a test basis, of evidence that supports the amounts and disclosures included in the financial statements, an assessment of the reasonableness of significant estimates, and a consideration of the appropriateness of the overall financial statement presentation. We consider that our auditing procedures were appropriate in the circumstances to enable us to express our opinion presented here. In our opinion these financial statements fairly present the financial position of the Institute at30th June, 1997, and the results of its operations for the year then ended in conformity with generally accepted accounting practice.

Jan 1, 1997

Council for 2001/2002 President A.A.B. Douglas President-elect S.J. Ramokgopa Vice-presidents Senior F.M.G. Egerton Junior Prof. T.R. Stacey Immediate Past-president Dr L.A. Cramer Honorary Treasurer J.A. Cruise

Jan 1, 2002

By H. G. Denkhaus

Comment on ?The evaluation of rock brittleness concept on rotary blast hole drills? in the Journal of SAIMM, vol 102. no. 1. pp. 61?66 Comment on ?Correlation of specific energy with rock brittleness concepts on rock cutting? in the Journal of SAIMM, vol 103. no. 3. pp. 163?171by R. Altindag Foreword Some thirty years ago it was almost customary that articles in South African technical and scientific journals were followed up by discussions in which the reader(s) expressed criticism and/or added to the information contained in the article. This custom has obviously died out, be it that the articles are nowadays of such a high standard that nothing can be added or be it that the receivers of the Journal suffer from an information inflation and do not read the articles anymore. I now have the temerity to offer a discussion to an article that recently appeared in the journal, namely ?The evaluation of rock brittleness concept on rotary blast hole drills? by R. Altindag (J.S. Afr. Inst. Min. Metall., vol, 102(2002), pp. 61?66.

Jan 1, 2003

Tracey Khanna, Assistant Editor of UK?s Mining Magazine discusses some of the new and important environmental challenges, physical and social, that are facing mining companies. The tide of public opinion has turned strongly against those companies which are unable to show that they are practising responsible environmental stewardship. This is, no doubt, in part due to the recent focus of the international media on environmental issues and constantly improving means of communications, which has brought the whole subject of mining and the environment to those who, in the past, had only a limited awareness of the industry. Mining companies today face new and important challenges with regard to the environment, both physical and social. New technology and a greater understanding of waste management techniques has helped to bring about improved handling and disposal of mines wastes, so reducing some of the impacts. However, improved technology has also brought about the economic viability of exploiting increasingly lower-grade ore from open pits, resulting in a greater visual impact.

Jan 1, 2000

By B. J. Vorster

AngloGold South Africa region currently consists of twelve gold plants. These plants use a combined total of $20 million of cyanide per annum. Of this, the major portion (60%) is consumed at two Ergo dump retreatment plants. Historically the primary motivation for cyanide control at Ergo has been one of leach/cost optimization. However, more recently, with the increased public awareness of cyanide in the environment, a secondary but increasingly important motivation for control has been to ensure that only the minimum amount of cyanide is added to the process whilst not compromising leach performance. Following a brief overview of the Ergo process, the methodology in determining the amount of cyanide to be added is described. The paper then traces the developments in cyanide control from very basic manual systems to the current automated control system. In line with the increasingly sophisticated control systems, developments also took place in regards to the method of cyanide analysis. The development of these analysers is also discussed. Whilst cyanide is one of the major drivers, if not the major driver of gold dissolution, it cannot be viewed in isolation particularly with respect to the relationship between cyanide and oxygen as ascertained from the Elsner?s well-known equation. Consequently, in order to control cyanide addition, knowledge of the relative cyanide/oxygen profiles is necessary. Various means investigated at Ergo for pulp oxygenation have therefore been included for the sake of completeness. Finally a comparison is made of the control achieved from the current system compared to the original manual system. The knowledge and experience gained at Ergo is now being used to draw up guidelines for the installation and optimization work at the other AngloGold plants. The net effect of this will be reduced cyanide consumption for the region, which also, apart from the obvious economic benefit, translates into a reduced environ-mental risk.

Jan 1, 2001

By D. François-Bongarçon

When it comes to sampling theory, a bad sampler is a bad sampler, no matter what, and a sampler is either bad or good. It also is of critical economic importance to tell and understand the difference, especially in a metallurgical plant. In this paper, the grand principles of Sampling Theory are first recalled, then the most popular types of sample cutters for plants are critically reviewed. It is concluded that the industry has a lot of progresses to make in that direction, although improvements usually pay for themselves very quickly.

Jan 1, 2002

By B. Kenny

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

Jan 1, 1999

By X. Yu

Although many investigations of the deformation behaviour of rocks have been carried out, most of them are carried out in compression. In all rock engineering practice it is usually assumed that the deformation of rocks in tension is the same as that in compression. However, data from numerous researchers have shown that this assumption is not correct for some rocks. A new loading frame for testing rocks in compression and direct tension has recently been developed by the authors, with the capacity to conduct both compression and tensile tests on the same rock sample. The results obtained show that the ratios between the average Young?s modulus in compression (ECA) and in direct tension (ETA) are 1, 1.16, 2 and 6 respectively in four rock types tested. For Poisson?s ratios, analogous relations were obtained. It was observed that, in all cases, the tangent Young?s modulus intension reduces with an increase in the applied tensile stress, while the behaviour of Poisson?s ratio is similar, but shows greater variability. The difference between the Young?s modulus of rocks in tension and that in compression could lead, large errors in calculating induced stresses around underground openings, as well as in determining the Brazilian tensile strength of rocks. This may have a significant influence in rock engineering and therefore more investigation is necessary into the tensile deformation behaviour of rocks and its influence.

Jan 1, 2005

Existing processes for the recovery of platinum group metals (PGM) from UG-2 ores place stringent requirements with regard to chromite content upon feed material to the plant. An alternative hydrometallurgical process for which this is not an issue is proposed that involves reductive roasting of the ore followed by leaching with HCl/chlorine, ion exchange, and recovery of PGM from the ion exchange eluate by reduction. Problems associated with leaching of PGM are discussed and results of laboratory testwork for each of the process steps are given.

Jan 1, 2004

By S. Sun

Recent studies on the physico-chemical properties of molten slags and oxide solid solutions of interest is reviewed. The review covers redox and phase equilibria in slags, viscosity, diffusivity, electrical conductivity, kinetics of interfacial reactions between slags and CO-CO2, interfacial properties and phenomena. Some highlights from ongoing work on modelling phase diagrams, component activity, viscosity and electrical conductivity of multi-component slags will be presented and results compared with published experimental data on slags with or without suspended solid phases.

Jan 1, 2004

By S. T. Johansen, C. Colomb, B. Ravary

Combustion and thermal NOx formation have been modelled using the Computational Fluid Dynamics (CFD) commercial code Fluent 6.1. The aim was to predict and give a better understanding of the combustion in electric arc furnaces for the production of ferro-silicon and silicon metal. Another important objective was to assess the impact of a number of operating parameters on the NOx formation. The CFD tools used are de-scribed with a special focus on models for species and turbulence transport. Sensitivity studies have been carried out to study the influence of several parameters: sub-models, process gas composition and distribution at the charge surface and influence of the presence of SiO. The main conclusions are: ?Using the combination of a realistic design, boundary conditions and models, the simulated NOx level is in quantitative agreement with measurements. The presence of water vapor is particularly important because of its influence on the specific heat of the mixture and resulting temperature. ?Release of significant amounts of SiO from the charge surface results in an important increase of NOx, even if we applied a simplified combustion model for SiO gas. However, because of lack of thermal and compositional data for blowing situations (when SiO flows directly from the arc cavity through open channels to the charge surface), no quantitative validation is possible. The way SiO is distributed (uniformly or as a jet) has a limited impact on the result in our computations.

Jan 1, 2007

By M. J. Nicol

Mr Vegter has analysed, in some depth, the approximations made in the treatment of the kinetic data presented in the original by ourselves (ref.1) and has come to the conclusion that ?under the experimental conditions used by Adams and Nicol (1986) the steady-state assumption was inaccurate?. We are acutely aware of the fact that the experimental method adopted does not permit the attainment of a true steady-state in the elution reactor. However, this does not eliminate the attainment of a pseudo steady-state by a suitable choice of the experimental parameters with the accompanying simplification of the analysis of the data with the aim of drawing the reader?s attention to the most important objective of the paper viz. the effect of various operating parameters on the rate of elution of gold.

Jan 1, 1997

By D. W. Dew

Billiton Process Research has carried out extensive research over the past four years to develop new process technology using bioleaching for extraction of copper and nickel from their sulphide concentrates. Continuous pilot scale and laboratory batch testwork has been carried out with adapted mesophile bacterial cultures at40°C?45°C, moderate thermophile cultures at 50°C?55°C and thermophile cultures at 65°C?85°C. Pilot scale work has demonstrated the commercial viability of mesophile cultures for bioleaching of secondary copper sulphide and nickel sulphide concentrates. Moderate thermophiles offer benefits in terms of reduced cooling requirements for commercial reactors and, in the case of bioleaching of nickel concentrates, some selectivity over bioleaching of pyrite. Continuous pilot scale testwork has shown that thermophiles achieve efficient bioleaching of primary copper sulphide and nickel sulphide concentrates, giving much higher recoveries than achieved by bioleaching with a mesophile or moderate thermophile culture.

Jan 1, 2000

By M. A. W. Bryson

Platinum group metals are extracted almost exclusively in South Africa from three very different zones in the Bushveld Igneous Complex, called the Plat, Merensky, and the UG-2 reefs. The Plat reef is currently being exploited only by Anglo American Platinum, whereas the Merensky reef is exploited by them, Impala Platinum, Northam, and Lonplats. The UG-2 reef, on the other hand, is also processed by these producers, but Kroondal and Barplats have operations that exclusively treat ore from this reef. At present the extraction of pgms from ores in South Africa follows the traditional route of upgrading to a concentrate in a minerals processing circuit, further upgrading to a matte in a smelter, and final upgrading and separation of the individual metals in a refinery. Thus all operations that extract pgms require a minerals processing circuit, the design and performance of which is a topic of much interest, as it is a poorly understood and not a very efficient process in relative terms, compared to the other processes. Recoveries across the minerals processing circuit of between 75 and 90% are the norm.

Jan 1, 2004

By M. Machikicho, N. R. Shoko, J. Chirasha

Keywords: Pyrometallurgy, furnace, ferrochromium, alloys, Zimbabwe Zimbabwe Alloys was founded in 1949 by a consortium led by the John Brown Group. It was the first ferrochrome plant in Africa. The establishment of the refinery was necessitated by an increase in world stainless steel demand and the need to reduce cost by shipping alloy rather than chrome ore. The location of the refinery in Gweru was influenced by a number of factors, not least of which were the abundance of chrome ore deposits, access to inexpensive power from Kariba, the availability of reductant coke from Hwange, accessibility to ports (as the town was well served with rail and road networks second to none in the country), and of course cheaper labour costs. The production of Low Carbon Ferrochrome (LCFeCr) was commissioned in 1953 and produced from an Open Arc Furnace with a Submerged Arc Furnace producing Ferrosilicon Chrome (FeSiCr) that is used as a reductant in the production of LCFeCr. An experimental furnace was commissioned in 1958 to help with efficiency and control on larger furnaces. A second Submerged Furnace was commissioned in 1963. Three other Submerged Arc Furnaces were built between 1967 and 1974. Several mines were acquired between 1974 and 1984, as a strategic move to ensure the growth of the refinery. A briquetting plant was commissioned in 1977, enabling the use of friable ores to enhance the capacity of ore supplies and ore cost management. A plant to recover alloy from slag was established in 1994 to capitalize on market demand without large capital outlay that would be required to build other furnaces to increase capacity. Zimbabwe Alloys has created employment opportunities throughout the years. There have been direct employment opportunities at both the refinery and the mining divisions. With time, indirect employment was realised both upstream and downstream of the refining process, enhancing the livelihood of numerous people. Zimbabwe Alloys' involvement with various labour skills has, of necessity, enabled it to develop a culture of safety at work, home, and play. Zimbabwe Alloys has contributed to society by participating and funding various local initiatives primarily to impact positively on societal needs. The latest development was in 1996, when Zimbabwe Alloys entered into a Technical Transfer Agreement with Japan Metals and Chemicals to improve the efficiencies and hence the profitability of the LCFeCr production process. A significant quantity of various alloys has been produced since inception, and significant foreign currency has been earned for the country. This was in spite of challenges that included the cyclic nature of market prices, the upheavals of sanctions affecting the macro-economic environment, and the challenges related to the deteriorating grade of chrome ore and reductant coke.

Jan 1, 2006

By A. Burger Pintér

To be meaningful the sharing of ideas about the National Environmental Management Act (NEMA) and social issues within the context of Mining and Metallurgy (M&M) requires an honest scrutiny of the M&M/social environment relationship, both past and present. It is not a secret that this relationship has been and is fraught with difficulties. Thus from all perspectives (M&M, society and environmental and social consultants) such a dissection, that highlights the realities, both good and bad, is uncomfortable. For this section of the colloquium to have any value, the honest but difficult approach needs to be taken.

Jan 1, 2000

To the members of The South African Institute of Mining and Metallurgy We have audited the annual financial statements set out on pages 269 to 276. These financial statements are the responsibility of the Institute?s Council. Our responsibility is to report on these financial statements. We have conducted our audit in accordance with generally accepted auditing standards. These standards require that we plan and perform the audit to obtain reasonable assurance that, in all material respects, fair presentation is achieved in the financial statements. The audit included an evaluation of the appropriateness of the accounting policies, an examination, on a test basis, of evidence that supports the amounts and disclosures included in the financial statements, an assessment of the reasonableness of significant estimates, and a consideration of the appropriateness of the overall financial statement presentation. We consider that our auditing procedures were appropriate in the circumstances to enable us to express our opinion presented here. In our opinion these financial statements fairly present the financial position of the Institute at 30th June, 1999, and the results of its operations for the year then ended in conformity with generally accepted accounting practice.

Jan 1, 1999

A physical modelling study has been carried out to simulate the slag-metal dispersion induced by a high-strength bottom gas injection. Water and kerosene were utilized to simulate metal and slag respectively. A water model of CLU (Creusot-Loire Uddeholm)vessel was used with three different nozzle orientations, namely, off-centre, triangular off-centre and centre. The gas flow rates changed from 0.00599 m3/s to 0.01081 m3/s. Height of heavy and light phases was kept fixed at 0.23 m and 0.02 m respectively. The dispersed phase hold-up was determined at various axial and radial distances, gas flow rates, and tuyere configurations. The observations revealed that at a fixed gas injection rate, as the vertical distance increased in the centerline, straight off-centre orientation resulted in greater dispersed phase hold-up values than those of the centre configuration and the triangular off-centre orientation. The dispersed phase hold-up was found to increase with gas injection rate and decreased with axial distance. The variation of the dispersed phase hold-up with the dimensionless axial distance and the gas injection rate was correlated by using the modified Froude number. The experimental values of the dispersed phase hold-up were found to be in reasonable agreement with the correlated values obtained from the modelling equations. The findings of the present study may be utilized in the ferroalloy refining vessels in terms of designing tuyere locations for optimum processing conditions.

Jan 1, 2004