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Open cast mining has been practiced in South Africa since the late1970s under near ideal geotechnical conditions. In the past decade, with the exhaustion of the traditional South African coal fields, geotechnical conditions have deteriorated. In addition, the nature of the open cast coal mining industry is changing from the conventional strip mining of virgin coal seams to the extraction of underground coal pillars by buffer blasted highwalls. These industry changes have resulted in the need to re-examine the manner in which geotechnical engineering is applied to highwall design. This paper proposes a geotechnical design rationale for open cast highwalls. Furthermore, the rationale takes cognizance of the various geotechnical hazards associated with conventional strip mining and pillar extraction by buffer blasted highwalls. The need to use geotechnical domain models and blasting geotechnics, as proactive tools for rock fall reduction, are also discussed.

Jan 1, 2001

By D. Strachan

Installation of support in known poor ground intersections during reaming operations requires rapid access to stabilize the shaft wall and thus to prevent the loss of the shaft through scaling. This is especially relevant to shafts of long dimension where the duration from time of exposure to time of support installation is lengthy This paper deals with the innovative methodology employed at Harmony?s No. 8 Shaft 17/24 level sub ventilation shaft to rapidly support a shale intersection between 23 and 24 Level by employing a single deck stage suspended from the reamer head by means of Skyjack winches.

Jan 1, 2009

By J. Chirasha

Keywords: Pyrometallurgy, ferrochrome, smelting, investment, Zimbabwe Four smelting plants currently make up the ferrochrome smelting capacity in Zimbabwe. Zimbabwe Alloys and Zimasco represent more then ninety per cent of Zimbabwe?s ferrochrome smelting capacity, while Maranatha and Oliken contribute the difference. Very limited investment in the sector (even for the expansion of existing smelters) has been experienced over many years, despite the fact that about 95% of the world?s chrome ore resources are in the Bushveld Igneous Complex of South Africa and the Great Dyke of Zimbabwe. The Bushveld has a greater quantity but a lower grade than the Great Dyke. A ten per cent increase in Zimbabwean ferrochromium production has been recorded in the past ten years, showing an almost stagnant capacity investment.

Jan 1, 2011

By R. Hope, C. van Heerden

In any process or organization inefficiencies are costly. In times of abundance this reality often does not receive much attention. During such times the focus is rather on increasing capacity to increase production. However, there is a growing awareness in the world of tougher economic, social as well as environmental conditions, and enterprises find themselves facing greater demands for accountability towards shareholders, the environment and the public, as well as growing competition for market share and limited global resources. This reality is no different in ensuring a sustainable mineral sands operation. In order to achieve this, any operation needs to be stripped of all process as well as operational inefficiencies. In this context it has become essential for any Mineral Separation Plant (MSP) to have the necessary process monitoring and control systems in place to continually monitor and optimize the production of on-spec products and maximize operational efficiency and consistency. The MSP Grade Control Solution developed by Crusader Systems and running on top of the CSense platform contributes towards these goals by improving the consistent production of on-grade product. This allows the process to operate closer to the maximum allowable product grade constraint, which in turn maximizes production.

Jan 1, 2003

By P.J. Terbrugge

Open pit slope design has conventionally been effected as a bottom-up function utilizing available geotechnical information. This results in a decision criterion based on probability of failure and factor of Safety with a risk assessment being carried out on the proposed design slopes. The design approach recommended reverses the process using fault event tree decision methodology. The consequences of this approach are that acceptable risk criteria have to be determined by mine owners. Slopes are then designed by the technical staff to achieve these corporate goals. Benefits that arise from the process are that the owners take a proactive decision on the risk-benefit relationship allowing the technical staff to optimize the geotechnical exploration programme and design.

Jan 1, 2006

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 C. Ntsele

Stirred milling technologies have firmly established themselves in concentrator circuits as energy-efficient alternatives to tumbling ball mills. High and continued increases in electricity costs, coupled with the ever-increasing power consumption by primary grinding circuits due to declining head grades of ore-bodies, provides a compelling case for these technologies. Additionally, the ability to successfully deploy stirred milling in coarse grinding applications extends the range of use in concentrators, thus increasing the opportunity matrix for energy optimization in a flowsheet. This paper therefore details methodologies and strategies that can be applied to evaluate the optimum stirred milling solution for different concentrator applications. These methods and strategies will focus specifically on the two major stirred mill machine types; namely, gravity-induced (VERTIMILL? grinding mill and Nippion-Eirich tower mill) and fluidized (SMD, Isamill?, Knelson-Deswik mill, etc. ). Finally, case studies from circuits across industry and laboratory tests will be used to illustrate the energy benefit from the use of stirred mills.

Jan 1, 2012

By G. Konak

In-pit crusher location selection has had an important role recently, since increasing diesel prices. One way of reducing the haulage costs is to shorten the truck haulage distance by bringing the truck dump point into the pit. This study covers the work done on the optimum crusher location definition for a company that produces aggregate near Izmir, a city of Turkey located in the west. This paper will discuss the effects of pit geometry and mine access requirements on optimum crusher location selection that are mainly based on the establishment of minimum haulage distance. The method will be introduced first and then the computer algorithm developed for this study will be discussed later in the paper. Keywords: in-pit crushing, optimum location selection, optimizing haulage, computer aided design.

Jan 1, 2007

By P. W. van Deventer

?Soil quality is the capacity of a soil to function, within ecosystem and land use boundaries, to sustain biological productivity, maintain environmental quality, and promote plant, animal and human health?. In the long-term, vegetative rehabilitation of mining wastes aims at, as far as possible, the proper ecological integration of the reclaimed area into the surrounding landscape, which is sustainable and requires minimal maintenance. A certain succession pattern is therefore needed. Recent ecological concepts recognize the role of the substrate?s quality and nutrients in affecting the rates and directions of succession patterns. Although pedogenesis and eventually soil quality in mine waste are not well known, monitoring of soil quality parameters in kimberlite mine tailings reveal a remarkable establishment and or improvement of specifics oil quality indicators. During the same time the vegetative cover?s total functionality as well as reproductive ability improved. Functions of soil, and thus soil quality, can be assessed at the field, farm, ecosystem, pedosphere, and global scale. It is recognized, however, that management of soil becomes increasingly difficult at larger scales, but for demarcated mine waste sites it is possible to ameliorate and manage and assess soil functions and quality. Therefore the significance of the study is the following: soil functions and quality become inseparable from the idea of system sustainability, and are considered as key indicators of ecosystem sustainability on rehabilitated mine tailings material.

Jan 1, 2008

By B. M. Loftus

An investigation into the use of impinging stream (jet) reactors for the leaching of a free milling ore produced an increase in gold recovery by 10% while decreasing leaching time by up to 90%.Tests on refractory ores demonstrate no apparent improvement in recovery. However, leaching kinetics are dramatically increased when these ores are subjected to jet reaction prior to agitation.

Jan 1, 1997

Escalating energy and electricity costs have become one of the largest drivers of expenditure in mining operations. Over the last eight years, energy costs have tripled when expressed as a percentage of total expenses in South African mines. In an effort to manage and reduce electricity costs, energy management strategies can be developed, inefficient operating units replaced, and the operation of energy-consuming components of ventilation systems optimized. Power consumption on mines is controlled mainly by three strategies, namely load clipping, by which energy use is reduced for certain parts of the day; load shifting, by which energy use is shifted to other parts of the day; and energy efficiency, by which energy use is reduced permanently. In this paper several projects that were implemented using the first two strategies of load clipping and load shifting are investigated. The actual and potential savings that can be achieved by implementing such energysaving interventions are presented. To reduce the operating costs of ventilating and cooling underground mines permanently, system optimization studies must be completed. Methods that can be used to reduce energy usage by optimizing cooling and ventilation systems are described, and network simulation models that accurately reflect the current and planned ventilation conditions are discussed. These models are then used to examine various options for improving the overall ventilation and cooling strategy. Different optimization scenarios can be simulated, and this assists the design engineer in obtaining the most energy-efficient system that will satisfy design workplace conditions. The final outcome is a reduction in operating costs, which can result in better operating margins and an extension of the life of mine.

Jan 1, 2014

By C. Atilla Öztürk

Determining the cutability and mechanical properties of rocks is vital for the feasibility studies of a mine or tunnel projects. Many scientists have investigated the correlation between these parameters in order to predict specific energy (SE) and other important rock cutability properties for many years. On the other hand, textural properties of rocks have been quantified in detail by Howarth and Rowlands (1987). Hence, it was possible to correlate mechanical and textural properties of rocks by using a parameter known as the texture coefficient (TC). The main objective of this study was to use the test results taken from a research project carried out by Bilgin and Shahrair1tocorrelate the mechanical and cutability properties of rocks with textural properties of rocks. For this purpose, uniaxial compressive strength (UCS), uniaxial tensile strength (UTS), cone indent or (CI),point load index (PLI), unit volume weight (?), porosity, SE, and normal and cutting force values, were correlated with textural properties of rocks. Hence it was possible to make illuminating interpretations about the relationships between the mechanical and cutability with the textural properties of rocks. Keywords: Cutting properties, mechanical properties, specific energy, texture coefficient.

Jan 1, 2004

By N. Sahay

Improvement in work place environment by conventional methods viz., installation of higher capacity fan, fans in parallel operation or booster fan is a risky proposition in many coal mines in India because of difficult geo-mining condition such as shallow depth, multi seam workings having thin parting and inter connected goaves one above the other. The situation is further worsened if the mines have fire affected sealed off area connected to different ventilation circuits. On many occasions circulation of more air quantity by increasing fan pressure have resulted in initiation of spontaneous heating. To address these problems, authors have made some improvement in conventional Dynamic Balancing of Pressure Technique and worked out few ventilation schemes which are aimed for neutralization of pressure differential across sealed off area at the same time having improvement in ventilation in the mine. The excess pressure differential across sealed off area is mainly caused by introduction of higher capacity fan. Similar situation prevailed in one of the mines of Jharia Coalfield, India. The problem was solved by application of the above technique. In this paper, brief description of the technique, the problem in the mine, results of investigation, computer simulation studies of various schemes and methodology adopted for implementation of the technique in the mine have been discussed in some detail. Keywords: Dynamic Balancing of Pressure Technique, Spontaneous heating, Work place environment.

Jan 1, 2003

By T. Watanabe, S. Hayashi, M. Hayashi, K. Nagata, H. Fukuyama

Chemical states of fluorine in CaO-SiO2-CaF2glasses in a composition range of CaO/SiO2=0.5?1.3 and 5?25 mol%CaF2have been investigated by 19F solid-state NMR with and without MAS. The isotropic chemical shifts of the glasses are close to those of cuspidine crystal (59.4 and64.3 ppm with respect to C6F6) and CaF2crystal (58.6 ppm). The fluoride ions are coordinated with four or less than four calcium ions in this composition range. The chemical shifts move to the lower frequency with an increase in the CaF2content, whereas those are not affected by theCaO/SiO2ratio. The ionic distance between calcium and fluoride ions increases with an increase in the CaF2content. The chemical state of fluorine is not disturbed by the degree of polymerization of the silicate network. Comparing the MAS and static NMR spectra, the second moment attributed to 19F-19F dipole-dipole interaction has been estimated. The values of the glasses range over 3.1?7.3107Hz2andthose are larger than the calculated value of cuspidine crystal. This indicates that fluoride ions form Ca-F clusters in the glasses and that the size of clusters increases with increasing the CaF2content. Keywords: chemical state of fluoride ion, CaO-SiO2-CaF2glass, solid state 19F NMR spectroscopy

Jan 1, 2004

By M. Dworzanowski

Beneficiation, in the context of this paper, has two distinct definitions. From an economic perspective, beneficiation relates to adding value to a mined raw material. From a metallurgy perspective, beneficiation relates to processes used to upgrade the mined raw material. Clearly then, ?economic beneficiation? is dependent on ?metallurgical beneficiation?. South Africa possesses the world?s largest mineral resources by value and is a significant global producer of many mined commodities. Significant metallurgical beneficiation of ores does occur in South Africa. The role of metallurgy in economic beneficiation will be examined in terms of current practice and the potential for expansion. South Africa?s main mining commodities will be covered ? namely gold, platinum, coal, iron ore, manganese, chromium, vanadium, copper, nickel, titanium, zirconium, uranium, and diamonds.

Sep 1, 2013

By J. T. Kalala

Energy consumption and wear of grinding media and liners are the major cost factors in milling plants. Since the beginning of the last century, much effort has been directed at the prediction of the power draw as affected by the mill operating conditions. This paper explores the prediction of the liner wear using the discrete element method (DEM). A mathematical model taking into account adhesion, abrasion and impact wear which occur in dry mills is derived in order to predict the loss of material on liners. The mathematical model is implemented in the DEM code using an objective function in order to produce realistic simulated profiles. Our DEM simulated predictions are compared to published experimental and industrial data. Keywords: modelling; discrete element method; liner wear

Jan 1, 2004

The AMIRA Code of Practice and Guidelines for Metal Accounting was developed in response to demand from a number of sponsor companies, including one major platinum producer. Since its publication in 2007, the Code has become widely accepted in the mining industry world-wide as a guide for best practice in metal accounting. With the changes in the structure of the platinum mining industry in South Africa over the last 10?15 years, in particular, the starting up of a number of small platinum producers who must have their concentrate smelted and the contained valuable metals refined by third parties, the need for metal accounting systems that are accurate and have an acceptable level of precision has become even more critical to the success of a platinum-producing operation. The current state of metal accounting in the industry is discussed, and possible areas for improved accounting and associated metallurgical efficiencies are identified.

Jan 1, 2013

By K. I. Afewu

A modified approach to the implementation of Gy?s sampling theory is discussed and used to design a procedure for sampling crushed gold ore feed to metallurgical process plants. The approach involves calibration of certain ore-specific parameters. These parameters were calibrated for two different crushed gold ores en route to grinding mills in process plants. The model predictions were compared with the predictions from Gy?s original model. Far smaller masses of samples are required by the modified model than by Gy?s model at the same relative variance. The representativeness of the sampling procedure if normally distributed errors are assumed was also calculated. These procedures and evaluations lead to significant savings on cost of handling and preparation of the samples and to a quantifiable degree of confidence in the analytical results for the process plant.

Jan 1, 1998

By S. Hlajoane, L. S. Mokhahlane

The demand for rare earth elements has increased around the world due to their application in a variety of technological advancements. Previous studies have evaluated the potential of the rare earth elements and yttrium (REY) hosted within the Permian coal deposits of the main Karoo Basin (MKB) in Southern Africa. However, not a lot of scientific research has gone into the Triassic coal deposits. The Triassic coals in South Africa were the first coals to be exploited for their thermal use in the 1880s, but the discovery of the higher rank and more abundant Ecca coal deposits led to the Triassic coals remaining largely unexplored. The demand for rare earth elements has sparked interest in these coal deposits as potential sources for valuable minerals. Late Triassic coal deposits in Lesotho have previously not been well documented and these low-rank coals can be a potential source of rare earth elements. This study aims to characterize and evaluate the potential of REY in the Taung coal deposit, southwest of Lesotho. Coal and associated argillaceous samples from the Taung coal deposit were analyzed using microscopic petrography for coal characterization and an inductively coupled plasma mass spectrometry (ICP-MS) to determine the amount of rare earth elements. Taung coal is classified as middle medium rank D bituminous coal. The total REY content in Taung coal and its associated rocks range from 162.9 ppm to 855.1 ppm, which is significantly higher than the upper continental crustal (UCC) average. The average critical REY concentration of samples from the Taung coal deposit is 189.4 ppm, which is three times higher than that of the Chinese Bayan Obo deposit. Samples classified as very promising and promising because of their outlook coefficients, are found to contain up to 77% of critical REY. It is envisioned that the area could be a prime deposit for these REY.

Nov 6, 2024

By L. Bircumshaw

Paper written on project work carried out in partial fulfilment of BSc (Eng) (Chemical) degree This paper details the formulation of a mathematical model for the simulation of a primary bioleach reactor, with specific reference to the leaching of pyrite. The model is based on the direct reaction mechanism, where the leaching of pyrite is said to occur via a two-step process. The process involves the formation of ferrous?iron through the chemical leaching of pyrite and subsequent bacterial oxidation of ferrous-iron back into ferric-iron. At steady state the rate of chemical leaching and bacterial oxidation are linked by the ratio of ferrous-iron to ferric-iron in solution. The extent of conversion of pyrite in the reactor system is described using the segregated flow model, with the exit age distribution of the solid phase being described by the Tanks-in-Series model. The final phase in model formulation involves the inclusion of steady state material balances on the bacteria and fluid phase components. The model is compared to pilot plant data and laboratory data for two different types of pyrite concentrates, with simulation results showing that the model is in good agreement with the data. Author key words: Bioleaching; pyrite; primary reactor; modeling; segregated-flow model; tanks-in series model.

Jan 1, 2006