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By D. F. Malan, J. C. Esterhuyse

In this study we explore the use of a novel numerical modelling approach to study the effect of pillar reinforcement on pillar stability. Case studies in the literature indicate that tendons, strapping of the pillars, and shotcrete or thin spray-on liners are commonly used to reinforce pillars. No clear methodology exists to select the type of support or to design the capacity of the support required, however. This has led to ongoing collapses in some mines in spite of heavy support being used to reinforce unstable pillars. A limit equilibrium model with confinement on the edge of the pillar was used to simulate the interaction of the support with the failing pillar. The model correctly predicts that an increase in confinement will lead to a decrease in the extent of pillar failure. As the displacement discontinuity boundary element method allows for the efficient solution of largescale bord-and-pillar layouts, the effect of pillar confinement can now be studied on a mine-wide scale. Accurate calibration of the limit equilibrium model is, however, required before this method can be used for the design of effective pillar support.

May 3, 2023

By Sönke Schmachtel

Several possible physico-chemical properties of composite electrodes for oxygen evolution are presented to describe experimental data for which a mathematical model had been developed. On this basis, local electrical and electrochemical properties of a composite electrode were investigated with conductive atomic force microscopy (CAFM) and scanning electrochemical microscopy (SECM). It could be shown by CAFM measurement that the boundary between matrix and catalyst particles seemed to have special advantageous electrical properties. The SECM measurements showed the presence of mass transport phenomena with increased surface concentrations, whilst the thickness of the Nernst diffusion layer was very small. An intermediate was detected and assigned to be hydrogen peroxide. From all species involved in the oxygen evolution reaction (H2O2, H+ and O2), it was concluded that local active spots exist on the electrode on which hydrogen peroxide reacts to oxygen and protons. A two?step two-material process was suggested to explain the whole oxygen evolution mechanism.

Jan 1, 2008

The aspect ratio (mill diameter/mill length) of autogenous and semi autogenous mills varies widely and can be as high as three or as low as 0.5. The literature on the subject of what effect aspect ratio has on grinding mill performance or energy efficiency is almost non-existent. However, at the design stage of many grinding circuits the subject is often vigorously debated amongst metallurgists. In this paper the performance characteristics of mills with different aspect ratios are examined to determine whether process performance characteristics are a function of aspect ratio and whether high aspect ratio mills are any more or less energy efficient than low aspect ratio units. Data from both pilot and full-scale mills are used for this purpose in open and closed circuit configurations.

Jan 1, 2007

1. New books Specialty steels and hard materials, edited by N. R. Comins and J. B. Clark. Oxford, Pergamon, 1983.482 pp. Hardcover £55.50. Papers presented at an international conference on advances in flow measurement techniques, edited by H. S. Stephens and B. Jarvis. BHRA Fluid Engineering (Cranfield, Bedford, MK43 OAJ, England), 1982. £36. Papers presented at Fourth European Conference on Mixing, edited by H. S. Stephens and D. Goodes. BHRA Fluid Engineering (Cranfield, Bedford, MK43 OAJ, England), 1982. £36. Papers presented at an international conference on hydrocyclones, edited by H. S. Stephens and G. Priestley. BHRA Fluid Engineering (Cranfield, Bedford, MK43, OAJ, England), 1982. 248 pp. £27. Controlled atmospheres for heat treatment, by R. Nemenyi. Oxford, Pergamon, 1983. 225 pp. Hardcover 20, flexicover £7.50. Electrochemical techniques in corrosion testing and research, edited by J. S. Scully. Oxford, Pergamon, 1983. 150 pp. Flexicover £9.45 2. Book reviews Off highway truck haulage, by the Newman Combined Group. Parkvine (Victoria), Australasian Institute of Mining and Metanurgy, 1982. Reviewer: B. J. Vorster Elsevier's mineral and rock table, compiled by P. Lof. Reviewer: A. Wedepohl Field geologists' manual, by B. A. Berkman. Monograph Series No. 9, Australasian Institute of Mining and Metanurgy, 1982.295 pp. Reviewer: R. A. G. Cuipers 3. Mintek reports Report M56 A computer programme for the evaluation of process routes in the production of ferrochromium. Report M61 An atomic-absorption programme for the Apple 11 Plus computer. Report M63 A general-purpose data logger. Report M65 A preliminary survey of the corrosivity of water in gold mines. Report M66 A review of corrosion inhibitors: theory and practice. Report M67 The determination of total cyanide in solutions containing uranium and gold. Report M68 The suitability of Doppler flowmeters for use in the minerals-processing industry. Report M70 The preparation and certification of two reference materials of South African manganese ore. Report M78 A n evaluation of the Leeds laboratory-scale flotation cell. Report M79 The determination, by X-ray-fluorescence spectrometry, of gold and uranium on resin. Report M80 The installation and commissioning of a Siemens SRS200 sequential X-ray-fluorescence spectrometer. Report M81 The application of the inductively coupled plasma system to the simultaneous determination of precious metals. Open-pit and strip mines The South African Institute of Mining and Metallurgy and the Mining Alumni Society of the University of Pretoria are organizing an International Conference on The Planning and Operation of Open Pit and Strip Mines in Pretoria from 9th to 13th April, 1984. Other Institutes co-sponsoring the Conference are The Canadian Institute of Mining and Metallurgy, The Institution of Mining and Metallurgy, and The Society of Mining Engineers of AIME.

Jan 1, 1983

By F. Shi , D. Lay, C. Antonio

High Voltage Pulse (HVP) technology has the potential to transform traditional mineral processing practice in the mining industry. HVP pre-treatment has been shown to enable ore preconcentration, achieve ore pre-weakening and improve mineral liberation. In order to improve the efficiencies of these novel HVP applications, it is essential to understand how HVP operational factors affect ore breakage in HVP pre-treatment. A two-level fractional factorial experiment using two rock samples, a gold-copper ore and a basalt sample, was performed to determine which factors have statistically significant influences on breakage probability, size reduction, and energy efficiency, and which factors have insignificant influences. Operational factors investigated include applied voltage, electrode gap, number of pulse discharges, the number of rocks being processed per batch, and rock size. In total, 1920 batch tests were conducted. For ore breakage characterised in terms of breakage probability and the degree of size reduction during HVP pre-treatment, the dominant factors were identified to be the number of pulse discharges, voltage, and the number of particles present in the processing zone. As all these three factors are related to the specific energy, it is concluded that the specific energy is the most important factor controlling ore breakage in HVP treatment. In terms of the efficiency by which spark energy is transferred from the generator energy, the factors found to have the most dominating influence were the particle size, the number of rock particles present in the processing zone and the voltage. Increasing the values of these factors reduced the loss of HVP energy during the energy transfer process. The factorial experiment using the two ore samples with vastly different mineralisation produced similar results. This proves that the dominant factors affecting HVP breakage are generally applicable to different ores types. Keywords: High voltage pulse, ore breakage, factorial experiment, specific energy

Jan 1, 2020

By M. G. Atmoret

It seems to me to be particularly appropriate that this topic should be discussed at the first prize-giving function of this kind. As you know, this presentation of awards to young mining engineers and metallurgists is to be an annual event, and never before in the dynamic and rapidly changing climate of the South African metallurgical industry has it been more necessary for young, and perhaps older, practitioners to consider the future of their profession and their role in the industry. I look forward with interest to the time, five to ten years from now, when I shall recall my crystal-gazing of tonight to see how far wrong I have been.

Jan 1, 1977

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

By P. Stevenson

Correlations for the critical velocity needed to hydraulically convey particles in horizontal, or near-horizontal, pipes are either explicitly dependent upon the shear stress imparted by the fluid upon the surface of the particle bed, or require a velocity and hydraulic diameter. Often such approaches are modified to account for pipe inclination by the introduction of simple factors. However, we assert that the physics that underpins the hydraulic conveying of particles in steep pipes (such as a directionally drilled oil well) is dissimilar to that which governs particle behaviour in horizontal pipes. In steeply inclined systems, a sliding sediment induces an upward counter flow and hence an autogenous contribution to the shear rate. The physics underpinning particle hydraulic conveying in steep systems is explored using the separation results of Laskovski et al.10

Jan 1, 2007

By C. Musingwini, C. Beaumont

"Kansanshi mine, located in northwestern Zambia, uses conventional openpit mining to produce primarily copper, with gold as a by-product. The ore is extracted from a deposit with highly complex mineralogical suites that are difficult to process, sometimes leading to poor recoveries. The mine was using an ore classification system called ‘Mat-Type’, which classified various ore types into 22 different quality categories, ranging from poor to good quality. Ore with poor recovery was classified as ’poor quality’ ore and directed to long-term stockpiles. Due to a lack of proper integration between the technical and functional areas forming the mine value chain, Mat-Type unintentionally misclassified ore. A geometallurgical analysis was therefore undertaken to review Mat-Type and a new geometallurgical ore classification system, called ‘OXMAT ’, was developed to replace Mat- Type.When implemented, OXMAT eliminated nine of the 22 ore categories and the remaining 13 ore categories could now be more accurately and consistently defined, leading to a significant change in the quantity of ore being mined. OXMAT demonstrated that within a defined test volume of the geological model, waste tonnes could be reduced by 19% while ore tonnes could be increased by 17%. This paper therefore demonstrates the value created through integrated geometallurgical modelling. IntroductionKansanshi mine is located in northwestern Zambia, approximately 10 km north of the provincial capital Solwezi and about 160 km west of Nchanga mine in the Central African Copperbelt (Broughton and Hitzman, 2002). The location of Kansanshi mine relative to other major copper deposits in the Copperbelt is indicated in Figure 1.Kansanshi mine uses conventional openpit mining methods to exploit copper- and gold-bearing veins hosted in a structurallycontrolled mineral deposit. Mining is carried out in two areas of the deposit, the Northwest and Main pits. A third area of the deposit, called Southeast Dome, is currently not being exploited (Figure 2)."

Mar 1, 2019

By D. R. Arnold

Discussion of the above paper by D. R. ARNOLDt This paper is the result of an excellent piece of work performed as a service to hyUrometallurgy in general and to the South African uranium industry in particular, and the authors are to be congratulated, Authors' reply Dr Arnold is correct in saying that the present Senbrix resins, which are based on the experimental heavy resins first developed at the National Institute for Metallurgy (NIM), need not necessarily show the same poor performance with respect to cobalt poisoning as the NIM prototypes. Oceanology International The next 01 World Conference is to be held Brighton, England, from 2nd to 7th March, 1980. The programme will concern technical advances in the offshore oil and gas industries, and is expected to include 140 papers from 20 countries.

Jan 1, 1979

By S. Ganguly, R. Kononov

Carbothermal reduction of manganese oxides and manganese ores in the solid state was studied in hydrogen, helium and argon at different temperatures, ore compositions and carbon to manganese oxide ratios. Wesselsore (South Africa) and two grades of the Groote Eylandt ore (Australia) with different level of impurities were examined. Ores were characterised by XRD, X-ray fluorescence, optical microscopy and scanning electronmicroscopy. Isothermal and temperature programmed carbothermal reduction experiments were conducted in a fixed bed reactor in a vertical tube furnace, with on-line monitoring of gas composition by the CO-CO2 infrared sensor. The reduced samples were characterised by XRD, SEM and LECO analyses. Extent of reduction was calculated using data on the off-gas composition, and LECO carbon and oxygen contents in the reduced sample. Manganese oxides in the ore were reduced to a-Mn and carbides Mn23C6 and Mn7C3 depending on the carbon to ore ratio. The reduction rate of manganese ores in hydrogen was higher than in helium and argon. Key words: Manganese, Carbothermal Reduction, Hydrogen, Argon, Carbon Monoxide, Helium, Kinetics.

Jan 1, 2007

By C. Pohlandt

A literature survey of methods suitable for the determination of cyanides in process streams and effluents is presented. Of the large number of methods published, 92 are examined in detail, emphasis being placed on the selectivity of the methods, i.e. the extent to which they enable one to distinguish between ionic cyanide and metal-cyanide complexes. Methods designed for the determination of 'total cyanide' (i.e. ionic cyanide as well as coordinated cyanide) are evaluated critically. Other aspects of the methods are also considered, such as sensitivity, accuracy, speed, and freedom from interferences.

Jan 1, 1983

By L. Cortez, Á. Magalhães, F. Durão

Methods based on regionalized variables theory, commonly known as geostatistics, have been widely used since more than three decades to predict/estimate spatial distributed data, namely mineral resources, with quite good results. However, some restrictive theoretical assumptions, such as the need of some kind of stationarity of data and the linearity of the predictor/estimator, are often wrong options in many applications. An alternative approach based on a finite mixture modelling, or cluster weighted modelling (CWM) technique, is presented and compared, in its theoretical and practical aspects, with the geostatistical methodology. CWM is a general non-linear framework based on the estimation of joint density functions allowing the calculation of the conditional probability function of the target values given their locations. Validation tests are performed in a 2D case study, where testing data proceeds from a soil contaminated by a heavy metal. The results of ordinary kriging and CWM estimations show a very good agreement with actual data. Keywords: Non-linear regression, Geostatistics, Ordinary kriging, Finite mixture modelling, Cluster weighted modelling.

Jan 1, 2003

By E. F. E. Müller

In a search for suitable reductants for the electro-metallurgical industry. the Fuel Research Institute is conducting investigations Into the charring of coals and the properties of the chars produced. This paper gives a selection of the results obtained as an illustration of the work being done. The research is proceeding.

Jan 1, 1980

The wage structure of graduate White men in 1979, by Adri Kruger, Pretoria, Human Sciences Research Council, 1979.76 pp. R5,00. (Reviewer: D. G. Malan) Financial Times mining international yearbook, edited by WilIiam G. Nightingale. London, Longman, 1980. 750 pp. £24 by surface, £34 by air. (Reviewer: J. D. Austin) Techniques in mineral exploration, by J. H. Reedman. Barking (U.K.), Applied Science Publishers, 1979. 533 pp. $90. (Reviewer: D. L. Kyle) Practical geostatistics, by Isobel Clark. Barking (U.K.), Applied Science Publishers, 1979. 129 pp. £13,75. (Reviewer: D. G. Krige) Uranium: The balance of supply and demand 1978- 1990, by the Uranium Institute. London, Mining Journal Books, 1979. 61 pp. £8,50 by surface,,£9,25 by airmail. (Reviewer: D. J. Crowe) Wear and abrasion in industry The South African Institute of Mining and Metallurgy and the Institution of Metallurgists (South African Branch) is to hold a colloquium on the topic of wear and abrasion of metals in February 1981. Steel rolling The International Conference on Steel Rolling sponsored by The Iron and Steel Institute of Japan will be held in Tokyo, Japan, from 29th September to 4th October, 1980.

Jan 1, 1980

By D. P. Power

The development of an accounting code for the metallurgical industry has been debated for many years. Following the series of tumultuous economic events in the nineties and earlier this century that have affected business, there was much need for legislation to be passed to minimize potential risk. One of the consequences to affect the mining industry was the enhancement of existing geological codes for reporting. In parallel the sponsors of AMIRA have taken the brave step to develop a generic code for metal accounting that embraces the full gamut of industry. In this paper the code will be reviewed in the context of metallurgical accounting as it applies to coal preparation. This paper provides the background for this development and an insight into the mechanism for the debate for the generation of this code. The key elements of the code as it applies to the coal industry are explained but most importantly the key opportunities are highlighted.

Jan 1, 2010

By D. Yu Pleev, V. G. Krivolapov

Mines of Southern Kuzbass working out, basically, coal formations of flat seams. Seams, as a rule, are inclined to self-ignition. Detection at early stages of the centers of endogenous underground fires has great value for safe conducting mountain works. One of methods of detection of an early stage of underground fires in the worked out space is the method of superficial radon survey. In the report the method is de-scribed and examples of superficial radon survey on concrete layers are given.

Jan 1, 2003

By S. Kauvosaari, M. Olofsson, O. Haavisto, M. Kosonen, J. Martikainen

The target in grinding circuit operation is usually to maximise the throughput and energy efficiency while keeping the product particle size on an optimal level for downstream operations. Furthermore, feed ore variations in size and hardness need to be compensated in order to stabilise the process. This is a challenging task for any circuit and requires good instrumentation, combined with careful control design. This study investigates the control of a two-stage iron ore grinding circuit with an AG and pebble mill at LKAB Kiruna KA3 concentrator in northern Sweden. A new control approach based on multivariable model predictive control (MPC) is designed, implemented and evaluated for the circuit. Additionally, advanced instrumentation including a volumetric charge measurement for grinding mills is utilised. The MPC control approach starts with step tests that are used to model the effect of manipulated variables (MVs) like feed rate, water addition and primary mill speed on controlled variables (CVs) such as final product particle size, power consumption and volumetric charge of the mills. In the control implementation phase, the models are then utilissed together with current process measurements and known operating limits to predict optimal future changes for the manipulated variables in order to reach the desired process output values. It is shown that the new control approach improves the stability of the circuit and reduces energy consumption. Keywords: Model predictive control, grinding, optimisation

Jan 1, 2020

By S. Tshikhudo

This paper outlines an investigation into the recovery of saleable fractions of coal from ?as-arising? South Export Plant effluent streams, using Baleen microscreening technology. South Export Plant, a subdivision of BHP Billiton Energy Coal SA (BECSA) Coal Processing, is a two-module plant treating 2000 t/h. The nominally -150 µm coal is untreated and is therefore passed from classifying cyclones to the thickeners for process water recovery. The thickened underflow is pumped into a series of slurry cells for further settling and recovery of supernatant water. The marginal quality, moisture content, and handlebility of this settled material renders it unsuitable for inclusion into saleable products and it is thus stockpiled and trucked to designated pits for disposal. Over the years, stockpiling and trucking has become an overly expensive exercise. In an effort to recover some of this cost, a task team was assigned to investigate less costly options to process slurry across BECSA plants. Various technologies such as froth flotation, sieve bends, and Reflux Classifier were considered, although the results were generally not beneficial ? this could be attributed to weathered/oxidized coal. A decision was made to pursue an alternative approach by testing the suitability of the new ?Baleen Filter?. The concept is to screen out the higher-grade fraction (+50 µm) as saleable product and reject the finer fractions to the slurry ponds. The Baleen Filter was found to effectively screen at an acceptable efficiency between 94% and 99.99%, with a very sharp cut-point (d50 and Ep). The actual yields from the screening results were better than the predicted yields in terms of both mass and energy as predicted from feedstock analysis.

Jan 1, 2014

By D. G. Krige

Some basic considerations in the application of geostatistics to the valuation of ore in South African gold mines by D. G. KRIGE, Pr. Eng., D.Se. (Eng.) Rand (Fellow) There is much room for improvement in the statistical procedures that have been used by gold mines over the past decade in the valuation of their ore reserves. Improvement depends on the establishment of the extent to which the patterns of frequency distributions and the directional variograms for the gold values vary from area to area within each section of a mine. The application of the lognormal distribution and of the De Wijsian variogram model for routine ore-reserve valuations requires detailed study before some of the reservations still held by mathematical statisticians can be met. This paper provides some preliminary evidence of the extent to which these models can be used with confidence, as well as suggesting how they can be applied to their full potential.

Jan 4, 1976