Search Documents

By R. H. Steel

Ingot casting and wire drawing In Iron Age Southern Africa by R. H. STEEL (Visitor) This paper describes the experiments that were conducted in 1974/1975 on two related aspects of Iron Age copper technology in Southern Africa: ingot casting and wire drawing. Three types of ingot were successfully cast: the St Andrew's Cross ingot, the marale ingot, and the musuku. It is suggested that the 'studs' on the musuku are not the remains of broken-off rods as previously proposed by other investigators, but that the ridged pattern is an ornamental feature. Copper wire was successfully drawn with similar tools and according to the procedures described in the literature on African Iron Age wire drawing. It is concluded that these accounts are generally accurate and that the pre-European metal workers are worthy of respect for the results they achieved with primitive methods.

Jan 11, 1975

By S. Vorberg, B. Fischer, U. Glatzel, R. Völkl, D. Lupton, M. Wenderoth

Owing to their excellent oxidation and corrosion resistance, Pt and its alloys are being used preferentially at elevated temperatures and in aggressive environments. For example, an important application field is the glass industry. Alongside the discovery of new potential application fields, the knowledge of material properties is essential for computer simulations, design configuration, process optimization, research and development or quality assurance purposes. Due to the importance for technical applications high-temperature properties have been investigated for currently available Pt-base alloys with ongoing improvements. For the determination of tensile creep test data up to 3000°C, including precise strain measurement, special experimental equipment has been developed at the University of Applied Sciences Jena, Germany. An overview of the existing and newly obtained mechanical property data on pure Pt, solid-solution strengthened Pt-Rh alloy, oxide dispersion-hardened materials Pt DPH and Pt 10%RhDPH as well as cutting-edge results on Pt-base superalloys hardened by intermetallic precipitates will be presented and discussed. Furthermore, some important application examples for the abovementioned Pt-materials will be given.

Jan 1, 2006

Branch Minutes of the General Meeting held at President Steyn Gold Mine canteen on Wednesday, 10th May, 1978, at 4.00 p.m. Erratum We apologize to Mr J. G. Taylor for the error in one of his qualifications. Bio-engineering monograph The selection of papers presented at the International Bio-engineering Conference at the University of Cape Town organized by the South African Institution of Mechanical Engineers and held in April 1977, and which are appearing in The South African Mechanic al Engineer during April to June this year, will shortly be available in book form. Mathematics The Institute of Mathematics and Its Applications is planning the following conferences and symposia: The Nand F Proposals in Relation to Mathematics, 1st July, 1978: London School of Pharmacy. NIM reports Report no. 1917 The instrumental neutron-activation analysis of granites from the Bushveld Complex. (31st Mar., 1978.) Report no. 1951 Potentialities and limitations of four-parameter equations for the correlation of formation constants of metal-ion complexes in aqueous solution.(15th May, 1978.) Report no. 1963 An evaluation of the methods used at the National Institute for Metallurgy for the analysis of base-metal concentrates. (28th Apr., 1978.) Report no. 1964 The separation, by anion exchange, of noble metals on substituted cellulose. (28th Apr., 1978.) Guide To The Preparation Of Papers For Publication In The Journal Of The South African Institute Of Mining And Metallurgy The following notes have been compiled to assist authors in the preparation of papers for presentation to the Institute and for publication in the Journal.

Jan 1, 1978

By D. F. Malan, W. J. Theron

Practical mining aspects should be considered when conducting pillar designs for bord-and-pillar layouts. The current methodology for pillar design will result in increasing pillar sizes with depth. This affects the extraction ratio and will result in onerous ventilation requirements when cutting large pillars. A holistic approach, including all mining engineering requirements, is required to ensure that the rock engineering designs are optimized to ensure efficient mining operations and sustainable production. Bord widths should not only be a function of the rock mass ratings, but should also be selected to fit the specifications of the mechanized equipment. The use of a ‘squat pillar’ formula for hard rock is discussed in the paper and the formula based on the exponents of the Hedley and Grant pillar formula, is explored. The effect of abutments and geological losses on average pillar stress is also explored. These factors must be considered when designing layouts at increasing depths.

Nov 27, 2024

By J. J. Cilliers, I. K. Craig, J. D. le Roux, K. Hadler

An analysis of the state-observability characteristics of a dynamic tank-to-tank model of a flotation bank indicates that the concentrate-flow rate of each tank can be estimated from accurate measurements of the pulp height in each tank and the final tailings flow-rate exiting the final tank. Therefore, there is an opportunity to construct an observer (model-based soft-sensor) which can estimate the concentrate flow-rate of tanks in a flotation bank. The concentrate flow-rate, i.e. mass pull, is generally measured by means of froth image analysers on industrial plants. A model-based soft-sensor will not only provide a means to validate froth image analyser results, but could potentially substitute them as they are less expensive to implement and maintain. Keywords: Concentrate flow-rate, estimation, flotation, modelling, observability, soft-sensor

Jan 1, 2020

By N. Wagner, P. den Hoed, J. D. Steenkamp, S. Soqinase

In pyrometallurgical processes, metal oxides are reduced from molten slag through carbothermic reduction. It is of interest to evaluate the reactivity of the carbonaceous materials towards substances such as slag. Characterization techniques such as coal petrography can provide insight into the influence of feed coal properties and how they potentially dictate reductant performance. This study aimed to compare the petrographically determined organic composition of coal to reductant reactivity. Two South African medium-rank C bituminous coals and one anthracite sample were investigated together with high-carbon ferromanganese industrial slag. The reductant reactivity tests were conducted at 1500°C in a muffle furnace to assess the potential of carbonaceous reductant in reacting with the main slag components. SEM-EDS was applied to understand the extent of MnO (and to a lesser extent, SiO2) reduction from the slag. Coal 2, consisting of a greater proportion of vitrinite (59.5 vol% on a mineral matter-free basis and 54.7 vol% including mineral matter) was the most reactive reductant. The anthracite sample, with the highest inert maceral proportions (71.8 vol% including mineral matter and 76.8 vol% on a mineral matter-free basis), was the least reactive reductant.

Feb 6, 2023

By D. Gregurek

The complexity of metallurgical processes in the non-ferrous metals industry. especially changes in the process conditions in combination with a diversity of metal processing furnaces, requires a precise knowledge of the system for the selection of refractory products. However, particular importance is still focused on the specific refractory consumption being as low as possible. The addition of recycling material with a high amount of impurities and the increase of low-grade ore concentrates used in the base-metals industry also entails a significant change of slag chemistries, process temperatures, etc., which influence the performance of already approved linings. This acknowledgement of process changes with decreased brick lifetimes provided the motivation for RHI AG to develop high-performance refractory bricks especially for non-ferrous metals applications. The internal laboratory tests with fayalitic slag showed very promising results compared with our approved magnesia-chromite bricks for this application. In order to identify suitable refractory products and to improve the life of the refractory lining, innovative product development has to be undertaken. In addition, the practical corrosion testing methods and facilities available within the RHI Technology Center, such as the induction furnace and the rotary kiln test equipment, allows the best possible understanding of brick wear at a laboratory scale. Based on the results of the test work, the optimal refractory solution can be recommended for a field trial at the customer?s site.

Jan 1, 2012

By M. S. Shishvan, J. R. van Duijvenbode, L. M. Cloete, M. W. N. Buxton

Geochemical and mineralogical datasets from Tropicana Gold Mine, Australia, have been used to define ore fingerprints. VNIR/SWIR spectral data were represented by four normalised wavelength regions and were clustered to form spectral classes. Sequentially, these spectral class proportions within a block and collocated XRF data were clustered to form material types (fingerprints). The material types were related to an Equotip-BWi correlation. These correlations can be used to extrapolate a hardness signature and generate a BWi proxy for different blocks. The combined fingerprints and BWi proxy can assist as a tool for enhancing the prediction of comminution behaviour. They can explain specific domain-related hardness variations. For example, one material type could be separated into a softer (~15-18 kWh/t), and harder (>20 kWh/t) material blend. This was accomplished using the commonly overlooked VNIR region at 605 nm. This outcome has significance for blending strategies.

Sep 1, 2021

By G. Drennan, A. Cameron

"South African mining operations depend on the skilled professionals produced through the tertiary education sector. In geoscience courses at the University of the Witwatersrand, which lead into the mining sector, there has been a significant increase in student intake over the past 15 years. This increase has been characterized by a radical shift in demography: in classes where white male students once formed the majority, black female students are now in the majority. This demographic shift appears closely linked to policies addressing issues of social justice and transformation in post-apartheid South Africa. We document this change and consider the role played by employment equity legislation (as in the Mining Charter) and corporate social investment strategies in the mining industry, notably through bursaries offered to black female students. We also look at the changing needs of the industry, where the critical need for managerial skills, not just technical knowledge, is highlighted through data from surveys of past students and industry managers. Our findings indicate the need for a curriculum adjustment to meet these changing requirements, as well as more rigorous selection criteria for bursars than simply gender, race, and appropriate matric results. IntroductionThe South African economy has historically been linked to mining and the exploitation of mineral resources. South African mining operations are dependent on the professional labour that is produced through the tertiary education sector, with critical thinking, teamwork, and the art of negotiation having been identified as the crucial skills required for this industry (Sideropoulos, 2014). Over the past three decades the South African system of education has gone through a period of dysfunction that it is struggling to rectify (Maphai, 2014). This has impacted on the levels of academic preparedness of students applying for places in higher education. Concurrently, government and university policies have widened access to higher education in response to the need to address issues of social injustice and transformation related to South Africa’s history of apartheid. As a result, the number of students admitted to universities has increased dramatically. In the School of Geosciences at the University of the Witwatersrand (Wits), the increase in student numbers has been accompanied by a significant change in demographics: classrooms which in the past were dominated by white males have given way to classrooms in which black females are often in the majority. This demographic shift is related to legislation such as the Mineral and Petroleum Resources Development Act and the Broadbased Socio-Economic Empowerment Charter, developed to reshape the socio-economic and equity frameworks of the country (Botha and Cronje, 2015). Requirements aimed at transformation in terms of management, skills development, and employment equity, together with corporate social investment (CSI) requirements, have resulted in bursaries being made available to attract students from designated groups, which in turn has increased the number of black students, and notably black female students, taking courses in geosciences. However, due to the economic downturn, instability in the mining industry has recently resulted in the downsizing of some mines, with international investors pulling out of South Africa. This instability resulted in devastating strikes across all sectors of the mining industry (Stewart, 2013) and in Marikana, an important platinum mining area, the strike culminated in a deadly shoot-out between miners and police. The resulting tensions spilled over into the gold mining sector, resulting in further strike action, shaft closures, and retrenchments. These challenges have implications not only for the mining industry in South Africa, but for the tertiary education providers whose graduates would have been absorbed into the mine-related workforce."

Jan 1, 2017

By J. Petersen, K. Shaik1, H. Kolev, Z. Cherkezova-Zheleva

Sperrylite is one of the most abundant platinum minerals globally, valued for its economic importance but also known for its highly refractory nature, making it difficult to process via the conventional route. This study explores the oxidative leaching of sperrylite using a cyanide–ferricyanide system, with a key focus on characterisation of the mineral and surface speciation under varied leaching conditions using x-ray photoelectron spectroscopy. The parameters investigated include the effect of sodium cyanide concentration, the use of potassium ferricyanide as an oxidant, copper sulphate pentahydrate as a catalyst, as well as the effects of temperature and particle size. A limited set of leaching tests was carried out to study the surface chemistry rather than optimising dissolution conditions. This approach identified mineral oxidation states and shifts in binding energies, prior to and post leaching. XPS analysis of sperrylite’s surface chemistry identified key species, comprising the bulk Pt(II)–As (≈73 eV) and As(–I)–Pt (≈41.8 eV) states, together with surface oxidation products Pt(II)–O (≈72 eV), Pt(IV)–O (≈74.5 eV), As(III)–O (≈43 eV) and As(V)–O (44.5 eV). Leaching led to the removal of pre-existing oxides on the ultra-finely ground sample, exposing the underlying bulk species. In contrast, the crystalline sample with an initial low concentration of oxides, generated higher amounts of fully oxidised species after leaching, reflecting greater surface reactivity.

Mar 6, 2026

By N. C. Joughin

A simplified economic model is derived for the financial return from a new gold mining project. The model is used to analyze the effects of changes in the mining rate, capital costs, working costs, value of the reef and the stoping width. The most effective avenues for improving the return from a new project are indicated. It is shown that those technological innovations which would improve the return significantly, and therefore make it possible to open more mines, are the use of smaller mines, means for improving the mining rate to capital costs ratio for smaller mines, planning and control of mines by computer simulation, an improved mine valuation procedure and means for mining at a decreased stope tramming width.

Jan 1, 2014

By L. Bloch

Most mine safety initiatives in South Africa are doomed to limited success because of one simple fact: they are a-historical and un-cultural and do not deal with the serious ?legacy issues? that still negatively impact on safety, production, and relationships. We in the SA mining industry continually use imported, foreign safety concepts and systems that will not work fully in a South African context. ?The 4th Wave: Culture-Based Behavioural Safety?, as developed by Lance Bloch, an international award-winning clinical psychologist with 12 years? experience in the mining industry - focused mostly on Platinum - is making waves. He has been very successful in creating people-centred, empowered, high-performance safety cultures wherever he has worked. Not only does the 4th Wave transform the corporate culture of a mine, improving safety and production and building an environment of Ubuntu, but it also uses people?s cultures as a means of winning hearts and minds in the battle for safe production. Powerful relationships are built through engagement at all levels, leading to all being focused on the best needs of the company and its constituents as a whole. The programmes are no less than nation-building - something most necessary in the industry, with the pressures from community, unions, the DMR, and politicians. This presentation will describe and discuss the 4th Wave as an advance on previous safety technology and programmes, as particularly relevant to platinum mining in South Africa today.

Jan 1, 2012

By E. Schoeman

Ion exchange resins were investigated for the effective recovery of platinum, palladium, and gold from a pregnant cyanide heap leach solution. Screening results indicated that strong-base anion exchange resins proved to be most effective in the recovery of these metal cyanides. Gold was selectively recovered with the use of Minix, while effective recovery of gold, platinum, and palladium over the base metals, copper, and iron, was achieved with Amberlite PWA-5. Successful elution of these metal cyanides was possible from both Minix and Amberlite PWA-5, using a 2M potassium thiocyanate solution at ambient temperature. Acidic thiourea was unable to elute platinum from either Minix or Amberlite PWA-5. Effective elution of palladium and gold were, however, achieved with use of acidic thiourea. Using these results, two conceptual flow diagrams for the recovery of these metals from cyanide solutions are proposed.

Jan 1, 2012

By N. Tatalias, P. Ilunga, M. Lampi, J. Edwards, K. Valkama, M. Nicolle, D. Samal

"Developing a greenfield mining project is a complex exercise: doing so in an increasingly volatile, uncertain, and ambiguous global economy adds significantly to this complexity. In the context of an elevated cobalt price, this paper outlines the metallurgical and process development of the Mutoshi copper–cobalt project for copper cathode and cobalt hydroxide production in the Democratic Republic of Congo. Chemaf has a long production history on the Copperbelt, a region widely perceived to be tough to operate in. This history stretches back to 2001, during which time the company has developed two copper–cobalt processing facilities. The experience gained in the development and operation of these two facilities has been used extensively in the Mutoshi copper–cobalt project. The metallurgical test work, process design, and project delivery approach are presented. Additionally, the decisions taken to minimize risk and maximize upside to the project are discussed. IntroductionChemaf (Chemicals of Africa), a mining company located in Katanga province of the Democratic Republic of Congo (DRC), has been operating since 2001 with two major copper– cobalt processing facilities: the Usoke and Etoile plants. In 2016, Chemaf acquired the Mutoshi mine, which belonged to Gecamines and had been explored by Anvil Mining since 2004 under a joint venture with Gecamines. Chemaf appointed African Mining Consultants Ltd (AMC) to undertake a preliminary economical assessment, then develop a JORCcompliant Mineral Resource estimate and finally a full life-of mine feasibility study. Both a Mineral Reserve and Mineral Resource were developed and the final life-of-mine feasibility study is to be published shortly. A metallurgical test work programme was initiated and carried out by Chemaf’s research and development laboratory with assistance from the Chemaf process team. After completion of the initial test work, Chemaf developed a process design criteria document for a 20 kt/a copper cathode and 8 kt/a cobalt in hydroxide production plant, followed by a flow sheet and supporting METSIM mass balance. As the drilling progressed, the plant design capacity was revised to 16 kt/a cobalt production. The life of the mine at this production rate is over 40 years."

Nov 1, 2018

By J. L. Havenga

South Africa produces about 400 Kt zircon (ZrSiO4) per annum. This represents about 30 percent of the global demand. However, very little is beneficiated locally and more than 95 percent is exported with little or no value addition. Zircon is a very inert material and needs to undergo high-temperature alkaline melting processes to produce valuable zirconium products. The conversion of zircon to plasma-dissociated zircon (PDZ) produces a chemically reactive species (ZrO2.SiO2) which consist of finely divided submicron monoclinic ZrO2 crystals dispersed in a SiO2 matrix. In this paper, an in-flight, non-transferred arc pilot plasma plant with a capacity of 100 kg/h and which consists of three 150 kW DC plasma torches, is described. The optimization of the plant, which includes the use of different zircon concentrates, the influence of particle size, feed rates, plasma gas, and energy utilization, is discussed.

Jan 1, 2012

By J. L. Havenga

South Africa produces about 400 Kt zircon (ZrSiO4) per annum. This represents about 30 percent of the global demand. However, very little is beneficiated locally and more than 95 percent is exported with little or no value addition. Zircon is a very inert material and needs to undergo high-temperature alkaline melting processes to produce valuable zirconium products. The conversion of zircon to plasma-dissociated zircon (PDZ) produces a chemically reactive species (ZrO2.SiO2) which consist of finely divided submicron monoclinic ZrO2 crystals dispersed in a SiO2 matrix. In this paper, an in-flight, non-transferred arc pilot plasma plant with a capacity of 100 kg/h and which consists of three 150 kW DC plasma torches, is described. The optimization of the plant, which includes the use of different zircon concentrates, the influence of particle size, feed rates, plasma gas, and energy utilization, is discussed.

Jan 1, 2012

Since 2001, the Hybrid Stress Blast Model (HSBM) project members have developed a software suite to model the complete blasting process from non-ideal detonation to muck pile formation. To preserve the physics and improve solution time, the breakage engine uses a combination of analytical models and 2D axisym-metric finite differences to model near-field crushing, coupled to 3D discrete lattice fracturing and distinct element numerical methods to model throw and muck pile development. The model has been validated by comparison with laboratory and field tests in kimberlite. Multiple blasthole simulations are used to demonstrate how changes to blasting parameters can influence downstream efficiencies. Case studies of wall control blasting show that the presplit design must balance the two opposing effects of increased damage with increased charge and decreasing attenuation of the seismic waves with decreasing charge. Modelling of decoupled explosives needs further development. Reducing the charge towards the back of the trim blast results in a much more significant decrease in back damage than altering the timing. The model demonstrates how separation along the weaker planes in a jointed rock can coarsen the fragmentation, leading to inefficient beneficiation, and extends the damage to a distance of at least twice the burden behind from the blasthole, severely compromising the wall stability.

Jan 1, 2012

By B. Orgilbayar, B. Unursaikhan, S. Sukhbat, Ts. Zagarzusem, D. Baasanjav, L. Jargalsaikhan, E. Otgonjargal, N. Sugir-Erdene, Ts. Soyolmaa

This study has investigated the efficacy of the gravity beneficiation method based on gravitation and centrifugal forces for manganese ore. Powdered samples of manganese ores from the Unagad deposit in Mongolia were analysed for their element and mineralogical composition using ICP-MS and X-ray powder diffraction (XRD). The analysis presented the mineralogical compositions of the ores as hydro goethite, manganese minerals and magnetite, gangue minerals as quartz, albite, orthoclase and microcline of manganese ore. Manganese minerals are white in colour and have micro-veinlet, fine grained-aggregates associated with gangue minerals. The most important manganese minerals are hausmannite, pyrolusite, rhodochrosite, and manganosite. The composite of feed containing 17.31 % Mn and 36.3 % SiO2 was processed in a shaking table. In the experiment, a concentrate assaying 41.37% Mn was obtained from this composite with 65% recovery. In another experiment, f80=0.074 mm particle size ore was used in the MGS concentration test. A concentrate containing 38.34 % Mn with 75.2% recovery was produced in this experiment. The results showed that it is possible to obtain concentrate through gravity processing of manganese ore, which is an economically beneficial process for producing a product of a standard requirement. Keywords: Manganese ore, gravity separator, centrifuge, shaking table 1. Introduction

Jan 1, 2020

By C. van Buuren, R. F. Sandenbergh, P. J. Pieterse

Gold extraction from double refractory ores using conventional cyanidation has proved challenging due to the presence of carbon within the ore. Carbon particles may adsorb leached gold resulting in gold losses to tailings, i.e. preg-robbing the gold. Some of the preg-robbed gold may be recovered by the application of the HiTeCC process on CIL tailings. The process developed by Metso Outotec involves caustic conditioning of the tailings followed by high temperature desorption and simultaneous adsorption onto virgin activated carbon of the aurodicyanide. The aim of this paper was to develop a model for the HiTeCC process which could be used to support design and optimisation of the process, based on the adsorption characteristics of the preg-robbing and activated carbons. It was found that accurate experimental isotherms can be used to predict the behaviour of preg-robbing adsorbents. Comparing the sorption isotherms for preg-robbing ores and activated carbon indicated similar dependencies on temperature and ionic composition. Applying boundary layer diffusion models coupled with experimentally determined isotherms for preg-robbing ore and activated carbon, the HiTeCC process was successfully simulated at experimental and plant scale. Gold recovery of the HiTeCC process is most sensitive to the temperature of desorption and gold loading of the activated carbon, with increased temperature improving recovery. The gold loading of the activated carbon in the process should always be maintained lower than that of the normalised pregrobbing carbon gold loading to ensure favourable conditions for adsorption onto the activated carbon. Caustic conditioning stabilises adsorption and is therefore not necessary during the desorption stages of the process, but potentially improves recovery during adsorption. Keywords: Preg-robbing, refractory gold ores, HiTeCC, aurodicyanide

Jan 1, 2020

By M. M. Bwalya, F. K. Mulenga

"SynopsisThe application of the attainable region (AR) technique to the analysis of ball milling is currently limited to batch data. This paper introduces the use of the technique to continuous milling.To this end, an industrial open milling circuit processing a platinum ore was surveyed. Samples were collected and later characterized by means of laboratory batch testing. On site, several milling parameters were varied systematically so as to collect data for modelling purposes. These paramters included ball filling, slurry concentration, and feed flow rate. After data analysis, a simulation model of the open milling circuit was developed under MODSIM®, a modular simulator for mineral processing operations. The mill was then simulated and the data generated was analysed within the AR framework.Initial findings reveal an opportunity to gain valuable insight by studying milling using the AR technique. From an exploratory perspective and inasmuch as this study is concerned, feed flow rate, ball size, and ball filling were identified as being pivotal for the optimization of open ballmilling circuits. Mill speed, on the other hand, had only a limited effect on the production of particles in the size range -75 +10 µm.IntroductionGlasser and Hildebrandt (1997) propounded the attainable region (AR) as a technique for the analysis of chemical engineering reactor systems. Results have since been produced and tested on both the laboratory and pilot scales. The method results in a graphical description of chemical reactions by considering the fundamental processes taking place in the system, rather than the equipment. From the plotted graphs, the process and the reactors can be synthesized optimally into a flow sheet.The use of the AR method still has a long way to go as far as mineral processing is concerned. For instance, several articles have reported the application of the AR technique to ball milling: Khumalo et al. (2006, 2007, 2008); Khumalo (2007); Metzger et al. (2009, 2012); Metzger (2011); Katubilwa et al. (2011); Hlabangana et al. (2012). Their main shortcoming has been the exclusive use of laboratory batch grinding data.To address this deficiency, Mulenga and Chimwani (2013) proposed a way by which the technique could be extended to continuous milling. In effect, the batch milling characteristics of a platinum-bearing ore (Chimwani et al., 2013) were used and scaled up to an open milling circuit. Then, with simplifying assumptions, an attempt was made to optimize the residence time of particles inside the mill. Later, Chimwani et al. (2014a) presented some optimization examples involving various milling parameters. The sequence of published articles then paved the way for the study of industrial milling systems with the AR methodology."

Jan 1, 2015