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By R. T. Jones

Base metals and platinum group metals can be collected in metallic alloy form, via a wide variety of smelting processes. The recovery, or degree of collection, of the valuable metals is a function of the extent of reduction in the furnace, which, in turn, is indicated by the fraction of iron present in the feed materials that report to the alloy. An equation has been developed that relates the recovery of various metals (such as Ni, Co, Cr, and PGMs) to the recovery of Fe. This recovery equation (for each metal) is characterized by a single parameter (K?) that can either be empirically fitted to the data, or expressed in terms of the equilibrium constant and the ratios of the activity coefficients involved. Data from a number of varied DC arc furnace campaigns are presented to illustrate this behaviour.

Jan 1, 2009

By M. Q. W. Jones

This paper summarizes important features of a compilation of thermal properties of stratified rocks from Witwatersrand gold mining areas. The database consists of more than 1000 thermal conductivity measurements, more than 700 density measurements, and nearly 100 heat capacity measurements. Most important rock types and stratigraphic units are well represented. Heat capacity does not differ significantly from one rock type to another, and density is relatively uniform although particular rock types are characterized by distinct average values. Different rock types also have distinct thermal conductivities, but this parameter varies by a factor of four to five. Primary factors controlling the thermal properties are mineral composition, degree of metamorphism, and porosity. In addition, the temperature dependence of thermal conductivity and heat capacity of quartzite may significantly decrease the thermal diffusivity of this rock at deep mining levels.

Jan 1, 2003

By A. C. Lawrence

A new approach to the -study of human factors in stope productivity by A. C. LAWRENCE B. Econ., D. Com. (S.A.) (Member) The extent of the improvement in mean performance which could be achieved by reducing the variance between stoping gangs is examined, and it is shown that a worthwhile gain would result if variance were reduced by as little as 5 to 15 per cent. The problem of identifying human factors which contributed towards variance in gang performance was examined in one gold mine. A total of 342 'observations' on 49 stoping gangs were gathered, each observation consisting of a set of figures for 36 variables for one gang for one week. The variables included 'stope factors' such as face length, 'gang factors' such as the ethnic composition of the gang, and 'supervisory factors' such as the experience of the miner. These variables were related to 'tons trammed per week' as a measure of work performance. The findings showed that certain of the predictor variables accounted for 66 per cent of the variance in gang performance and about two thirds of this could be attributed to gang and supervisory factors, that is to the 'human factors'. The method suggests a basis for a new approach to the identification of human factors and is a promising step towards optimizing gang performance.

By Du Sichen, K. Mukai, S. Seetharaman

Viscosities of slags constitute an important physical property needed for an understanding of the mass transfer phenomena in metallurgical processes. Viscosity is also the key that leads to a better understanding of the structure of slags. It is well known that the viscosities of silicate slags decrease with the addition of basic oxides due to the breaking of the silicate network. The measurements of slag viscosities often pose experimental challenges, especially to the choice of materials. The keynote lecture takes up the experimental problems and the various techniques adopted. Dynamic viscosity measurement, as a powerful tool towards an understanding of the kinetics of some high temperature reactions, is brought out. A number of semi-empirical models have been developed to estimate the slag viscosities in the case of multi component slags. A critical survey of these models is presented in the lecture. Earlier models by Riboud et al., Urbain et al. and Mills et al. have been developed further into a new generation of models. Some of the current important models are (1) Model by Iida et al. (2)CSIRO model (3) Pyro research Model (4) Model by Tanaka et al. (5) Model approach by Reddy et al. and (6) KTH-model. The predictions and capabilities of the various models are compared. Estimations of viscosities from thermodynamic data and prediction of liquidus temperatures from viscosities are presented. The concept of surface viscosities with reference to slags and viscosities of two-phase mixtures are also taken up in the presentation.

Jan 1, 2004

?Longhole blast hole drilling? techniques are not new to the mining industry. Appropriate mechanization and improvement of the techniques and application has evolved from the industry requirements. Today safety and economics play a larger role in the excavation of ore passes, ventilation passes, and relatively small inclined excavations in the conventional gold and platinum industry. The application of dropraise drilling from the top or from the bottom is discussed investigating the current techniques available, DTH application, advantages and disadvantages, limiting factors, typical layouts and proposals, the drop raising technique and future applications. Similarly, the application of longhole blast hole drilling in tabular and massive orebodies is discussed with emphasis on the DTH application, advantages and disadvantages, limiting factors, typical layouts, the long hole stoping techniques and future applications.

Jan 1, 2003

By M. Berjak, D. M. Hawkins, V. E. Marting, R. B. MacGillivray

Contributions to discussion V. E. Marting (Associate Member): The authors of this paper should be congratulated in having pioneered the application of the Sharapov predictor to local data, and in having made a valuable contribution to South African experience in the quantitative treatment of geological information using a digital computer. Although the existing set of three programmes has been described as a 'suite' it does not represent an integrated system in the accepted sense since the communication between runs is made in the form of punched card files to enable the mining engineer to exercise discretion and control over the data entered at each phase. Although the authors are justifiably proud of the successful results obtained through the application of this method, I feel that it is my duty to comment that the computer aspect of the work has not reached full development and is deserving of the financial support needed to increase its widest usefulness. At the present moment a routine to detect 'missing information' has not been commissioned. Due to the lack of documentation the use of the programmes is restricted since the format for the submission of data is known only to the authors. It is very unlikely that a profitable return on the development costs will be enjoyed before the programme is fully documented and made available to wider use. My criticism of the present incomplete state of the work is being voiced purely with the intent of focussing on the significance of this project and the fact that it is deserving of development on an industry basis. It should be noted that at the economical cost of R4.00 per sq ft of computer print-out, a mining engineer can hardly afford to miss the opportunity of using the programmes on other (e.g. metalliferous) mineral deposits of tabular formation. Since the publication of this paper I have had an opportunity to see the results of the programmes developed by Drs M. D. G. Salamon and F. Deist for designing bord and pillar workings. The basic data for these latter programmes are extracted from iso-line plans drawn conventionally by geologists, a task that could be considerably expedited through the use of Mr Hawkins' programmes. It appears that the efforts of these respective teams are complementary and it is in the interests of the industry that these individual components should eventually form part of an integrated system. E. Margo* (Member): This paper is a good example of how and where the backroom scientist-in this case the mathematical statistician-can aid the mining engineer to develop not only more accurate means for dealing with valuation problems but to develop a tool that can also cope with changed geological specifications.

Jan 1, 1969

By C. Sima, M. Legoabe

Keywords: Pyrometallurgy, furnace, platinum Mortimer Smelter is one of the three smelting operations in the Anglo Platinum Group. It is located in the Limpopo Province, approximately 100 km north of Rustenburg, and approximately 15 km west of Northam. The smelter operation is the smallest of the three smelting operations in the group, with a smelting capacity of 170 kt/annum. The operation consists of a Larox filtration plant, a Drytech flash drying plant, a modified Elkem / Hatch 19.5 MVA furnace, and a 60 t/h matte crushing plant. The operation does not convert its furnace matte, and hence the final sulphide rich matte is transported to and processed further at the Anglo Platinum Converting Process (ACP) within the Waterval Smelter Complex in Rustenburg. Furnace slag is granulated, and processed through a slag mill, or transported to a slag dump.

Jan 1, 2006

By F. M. L. Mulaudzi

Behaviour studies of metal dusting processes and associated filamentous carbon formation were undertaken on Alloys 600, 601, and 800 using a simulated metal dusting environment of 25C0-70H2-5H20 (vol.%) at 650°C. These samples were studied visually and by optical microscopy, scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX), transmission electron microscopy with energy-dispersive X-ray spectroscopy (TEM-EDX) and x-ray diffraction (XRD). Visual examination and SEM surface observation showed that Alloy 800 suffered metal dusting attack at an early exposure reaction period. The coke deposit amounts increased significantly with reaction time from 168 hours to 336 hours in Alloys 600, 601, and 800. Alloy 800 showed pitting after 168 hours' exposure, and the degree of pitting increased after 336 hours. XRD showed all these alloys had a common austenitic phase, with Alloy 800 also having ferritic metal particles. Alloy 800 after 168 hours' exposure had a complex phase mixture on the surface, consisting of ferritic Fe and austenitic FeNi phases. For coke deposit, there were also Fe304, Fe3C and graphitic carbon. The existence of Fe, Ni, and Cr metal particles, and also graphitic carbon in coke deposits, was confirmed by EDX analyses.

Jan 1, 2013

By Y. Z. Ma

This paper presents a matrix formulation of factorial kriging, and its relationships with simple and ordinary kriging. Similar to other kriging methods, factorial kriging can be applied to both stationary and intrinsic stochastic processes, and is often used as a local operator. Therefore, the concepts of intrinsic random function and local stationarity are first briefly reviewed. Kriging is presented in a block matrix form in which the kriging solution is useful not only for understanding the relationships between simple and ordinary kriging methods, but also the relationships between interpolative kriging and factorial kriging. When used as a signal/noise-filtering method, factorial kriging is especially useful for multiscale modelling. Examples for general signal analysis and geophysical data signal filtering are given to illustrate the method..

Jan 1, 2014

By H. L. Monro

Contribution by B. K. Martust I congratulate the author on his interesting paper. In my view, the establishment of the level at which South African gold output is at some kind of optimum is an interesting though somewhat academic exercise. Contribution by D. M. Hawkins* The thesis of the paper is a very interesting one, but, before it is used as the basis of any firm proposals to restructure the mining industry, which changes may be irreversible, one should be very sure that the basis of the calculations is sound. Contribution by P. J. Niewenhuizen* The hypothesis advanced by Mr Monro that the demonetization of gold in August 1971 introduced a major new policy variable, namely the supply-pricejdemand-price relationships, into the decision making process touches on a matter that has never really been given serious thought by the industry. Contribution by B. G. Kingsman* As a co-worker on the development of an econometric model for supply and demand in the world gold market with Mr H. L. Monro, it would perhaps be useful for me to make some comments on the various points raised in the discussions on his paper.

Jan 1, 1984

By M. A. Reuter, N. J. Bartie

Metals make modern societies function, and increasingly, various high purity precious and special metals endow sustainability-driving technologies with specific functionalities. These metals become heavily intertwined within products, complicating end-of-life treatment. To counteract the resulting downcycling and potential depletion of scarce resources, maximising both the quantities and qualities of materials recovered during primary extraction and recycling, processes should be a priority in the pursuit of sustainable circular economy. Adopting a process simulation approach; a digital twin for the life cycle of cadmium-telluride solar photovoltaic (CdTe PV) modules was created. The system comprises an integrated metallurgical production system that produces, among others, cadmium, tellurium, selenium, zinc, copper, and lead, all of which are required to manufacture PV modules. System-wide resource efficiency and environmental impacts are assessed using exergy analysis and life cycle assessment, respectively. Simulation of this large and complex product life cycle at a high level of detail allows for the evaluation of potential system-wide effects of various production, recycling and residue exchange scenarios aimed at maximising the sustainability of the entire system. It diminishes the need to make arbitrary choices about allocation methods for the distribution of environmental impacts in multipleoutput production systems. Furthermore, it demonstrates the key importance of metallurgy in achieving circular economy. Keywords: Circular economy, sustainability, simulation, metallurgy, CdTe photovoltaics, life cycle assessment

Jan 1, 2020

By R. T. Jones

Keywords: Pyrometallurgy, DC arc furnace, myths, history, hollow electrode, radiation, resistance, flicker, AC DC arc furnaces are widely used for steel scrap melting as well as for reductive smelting of ore fines. Industrial smelting applications include the smelting of chromite to produce ferrochromium, the smelting of ilmenite to produce titania slag and pig iron, and the recovery of cobalt from non-ferrous smelter slags. A number of myths and misconceptions are widely held, especially regarding: the age of the technology, the use of a hollow electrode, arc stability and shape, arc and bath radiation, interaction between the arc and molten slag, electrical behaviour of arcs and slags, a comparison between AC and DC furnaces, DC reactors, the lifespan of bottom electrodes, and the applicability of DC arc furnaces to various metallurgical systems.

Jan 1, 2011

By P. M. Mashaba, S. O. Bada

An advanced high internal phase water-in-oil (HIP W/O) emulsion binder and flotation with an internal dispersed water phase of 95 vol% was used to beneficiate South African weathered coal from discard dumps. Five coal samples with calorific values ranged from 8.48 MJ/kg to 20.94 MJ/kg were utilized. The performance of the HIP W/O emulsion was compared to that of kerosene in terms of the physicochemical properties of the clean coal products. A 5 kg/t emulsion binder addition produced a high-quality coal concentrate with 11.76% ash and a heating value of 28.61 MJ/kg from a sample containing 29.34% ash. Using the same dose and coal sample, kerosene resulted in a clean coal concentrate with 17.47% ash and a calorific value of 26.42 MJ/kg. Further samples were also beneficiated using 5 kg/t of W/O emulsion. The highest increase in calorific value was achieved from the beneficiation of a sample containing 48.71% ash, from 8.48 MJ/kg to 18.16 MJ/kg. It has been established that emulsion binders can upgrade coal samples dumped many decades ago.

Aug 2, 2022

By R. J. Davidson, W. D. Douglas, J. A. Tumilty

SYNOPSIS Two pilot plants operating on different types of carbon were used to generate steady-state adsorption data in the treatment of gold-plant solutions of high and low tenor. A pilot plant comprising three 4 m long columns and using 3 mm extruded activated carbon was used to treat pregnant solutions with a gold concentration of 5 to 8 g/t at pH 10 to 11,5. Column influent was pumped at a super¬ficial flow velocity of 0,5 m/min while the carbon was moved daily so as to effect gold loadings on the carbon of 5 to 10 k /t. With a carbon-bed depth of 12 m, an adsorption efficiency of 99,9 per cent was obtained in a bed depth of 9 m, which was subsequently reduced to 8 m when the depth of the carbon bed was reduced to 8 m. This improvement in efficiency was attributed to the reduced residence time of the carbon from 12 to 8 days. A corresponding decrease in adsorbed silica indicated that some silica fouling of the carbon had occurred. A second pilot plant, comprising a single column 6 m in length and using coconut-shell carbon of 1,0 to 2,4 mm, treated a solution with a gold concentration of 0,7 g/t at pH 8,0. Feed solution was pumped at a superficial flow velocity of 1,0 m/min while carbon was moved every 8 hours to give gold loadings of more than 5 kg/t. An adsorp¬tion efficiency of 99,5 per cent was indicated at steady state. Intermittent washing of the column with dilute hydrochloric acid was shown to have a beneficial effect on the gold adsorption and to reduce the pressure drop across the column. Intermittent washing with dilute sulphuric acid indicated that there had been some passivation of the car¬bon during the treatment of a solution with a gold concentration of only 0,2 g/t. Compared with other adsorption systems, the countercurrent moving bed appears to offer significant advantages in terms of metallurgical efficiency and capital investment. The inability normally associated with moving-bed systems to treat solutions containing suspended solids may be overcome to a degree by the use of relatively coarse extrud¬ed carbon.

Jan 1, 1985

By B. Dias, P. C. Schutte

Work-related musculoskeletal disorders (WMSDs) affect the wellbeing of workers and result in poor quality work, lower work performance and decreased motivation. In contrast to ‘occupational’ diseases where there is a direct cause-and-effect relationship between hazard and disease (e.g., asbestos and asbestosis, lead and lead poisoning), ‘work-related’ diseases are multifactorial, where the work environment and the type of work that is performed contribute significantly to musculoskeletal disorders. WMSD is the term used to describe disorders and diseases of the musculoskeletal system (i.e. muscles, joints, ligaments, tendons and nerves). WMSDs are by definition a work-related phenomenon. The literature shows inarguably that certain jobs and certain work-related factors are associated with a significant risk of contracting a WMSD. It is assumed that repeated movements and postures, static work, continuous loading of the tissue structures or lack of recovery time, trigger or cause a pathological process that then manifests itself as a WMSD. This paper looks at the prevalence of the WMSD condition at three mines in South Africa: a coal, a gold and a platinum mine. Predisposing factors that include work factors, presentation of symptoms and psychological factors will be discussed in the paper.

Jan 1, 2003

By D. Stone, M. Le Roux, Q. P. Campbell, M. Fofana

Float-and-sink analysis is widely used in the coal industry to obtain washability data, yielding important information about beneficiation potential and performance. This method is associated with health and environmental problems, and research into alternative densimetric methods is important. The RhoVol is a new technology developed by De Beers Group Technology South Africa (DebTech) for the image-based generation of densimetric data from ores. The analysis is done on a per-particle basis, within a size range of +3 mm –8 mm. In this paper we compare the established methods used for the float-and-sink analysis of coal with a new method using RhoVol. The aim of the study was to determine the validity of the information obtained from the RhoVol analyser by performing comparative densimetric analysis on three different coal samples. The results showed that the RhoVol method was more rapid, safe, and precise, but tended to consistently underestimate the density of the coal sample, probably due to varying coal porosity.

Oct 3, 2023

By F. Magweregwede, S. Khan

Circular economy opportunities for the mining sector are presented in this paper. A literature review was undertaken, followed by qualitative data gathering through survey questionnaires and unstructured interviews, and stakeholder engagements through workshops. The circular economy opportunities were identified and categorised according to the three circular economy principles of designing out waste and pollution, keeping products and materials in use, and regenerating natural systems. Opportunities aligned with the first principle include increased ore extraction efficiency processes, water recovery and recycling, substitution of raw materials, technology and waste utilisation for carbon capture and biotechnology. The second principle includes opportunities such as zero waste-to-landfill strategies, repurposing of mine waste, re-mining of tailings, recycling metals and processing of residues, and urban mining of electronic waste. Opportunities aligned with the third principle include the adoption of renewable energy, green hydrogen production, repurposing of post mining landscapes, and eradication of alien invasive vegetation. Furthermore, the challenges of implementing circular economy in the mining sector are discussed. The current rate of waste generation from mining activities far exceeds the rate of reuse and repurposing. Recycling of large tyres and characterisation of hazardous electronic waste also pose challenges. The most implementable circular economy opportunities in the mining sector are those aligned with the second principle of keeping materials in use. The high impact opportunities aligned with the first principle of designing out waste and pollution, and the third principle of regenerating natural systems, are more difficult to implement as they require large investments.

Dec 15, 2025

By E. Pardo-Igúzquiza, R. A. Olea

The bootstrap is a computer-intensive resampling method for estimating the uncertainty of complex statistical models. We expand on an application of the bootstrap for inferring semivariogram parameters and their uncertainty. The model fitted to the median of the bootstrap distribution of the experimental semivariogram is proposed as an estimator of the semivariogram. The proposed application is not restricted to normal data and the estimator is resistant to outliers. Improvements are more significant for data-sets with less than 100 observations, which are those for which semivariogram model inference is the most difficult. The application is illustrated by using it to characterize a synthetic random field for which the true semivariogram type and parameters are known.

Jan 1, 2015

By E. Snyders

The upgrading process of an inferior grade of zircon to a superior opacifier for ceramic applications was investigated. A calcining process in the presence of mineralizers was used to produce the product in a conventional muffle furnace. A pre-milled inferior grade zircon concentrate, with a relatively high iron and alumina content generally not suitable for high quality ceramic applications, was used in this study. The influence of the upgrading process on the opacifying properties of the zircon material was compared to that of commercially available prime grade zircon opacifier products currently being produced in South Africa. The influence of a calcining step in the presence of mineralizers with regard to the milling characteristics of the treated zircon material was also evaluated in this study. The morphology of the treated and untreated zircon opacifier samples were investigated by SEM micrographs and the colours of zircon samples were characterized on the grounds of the Commission Internationale de l`Eclairage (CIE) standard procedure (CIE L* a* b* measurements) after application on a bisque ceramic tile. It was found that the treatment improved both the milling as well as the opacifying properties of the treated inferior grade zircon concentrate and renders it equivalent to or better than prime grade zircon opacacifiers currently produced. Keywords: ZrSiO4; opacifier; colour; milling; calcining.

Jan 1, 2005

By A. H. Mokken, G. K. I. Blendulf, G. J. C. Young

A study of the arrangements for pulp discharge on pebble mills, and their influence on mill performance by A. H. MOKKEN, B.Sc. (Eng.) (Rand) (Fellow), G. K. I. BLENDULF, M.Sc. (Stockholm) (Member), and G. J. C. YOUNG, B.Sc. (London) (Member) Although used for many years in the gold-mining industry, the conventional pan lifter at the discharge end of a pebble mill has hindered attempts at optimization of speed of rotation and pulp flow. A theoretical approach to flow patterns in pan lifters has pointed to limitations in the capacity of these lifters, with capacity decreasing as speed of rotation is increased. Complete elimination of the pan lifter by the adoption of peripheral or end discharge has resulted in a marked increase in pulp flow and an improvement in power utilization. Assays of the gold content of pulp discharged after a mill stoppage from mills fitted with pan lifters show values well in excess of the current milled grade, which indicates an accumulation of gold particles in the mill and, therefore, a longer retention period. The same could apply to other heavy minerals and metals present in the ore feed or worn off mill linings and metallic grinding media. Examples are osmiridium, fine iron and iron alloys, and copper and sulphide minerals. This phenomenon is attributed to the higher specific gravities of these metals and minerals, causing them to migrate towards the mill shell, from which position they are not readily removed by the lifters at the discharge end of the mill. The close association of gold particles with iron and sulphide minerals in the crevices of mill liners might be conducive to the formation of coatings on the gold. Assays of samples of milled pulp taken from a mill designed for end discharge show a lower accumulation of gold. The accumulation and nature of these gold particles are being studied at present. With increasing diameters of pebble (or autogenous) mills, peripheral or end discharge appears to be the preferred method of pulp removal.

Jan 5, 1975