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By D. F. Williams

The modelling, simulation, and design of processes for the recovery of gold from solution by absorption on carbon require the combination of a suitable rate expression with a description of the flow conflguration of the system. By the use of a suitable rate expression from the literature, methods are presented for the design of multi-stage countercurrent absorption systems corresponding to the commonly used carbon-in-pulp and carbon-in-column contacting systems. The sensitivity of the recovery to various design parameters is illustrated. These results have important implications in the choice and design of equipment.

Jan 1, 1985

By J. A. L. Napier

One of the most important characteristics of tabular mine stress analysis is the need to represent the complex evolution of mining face positions and the accompanying induced stress changes in the rock mass. Integration of seismic activity with numerical modelling requires flexible and efficient solution schemes in which both off-reef damage and large-scale fault slip can be effectively represented. A new approach is investigated in which the stope closure and ride variables can be found using a moving least squares estimator. Some advantages of this approach over traditional element-based tessellation schemes are identified. At the same time, shortcomings of this method are noted when the displacement discontinuity variable is approximated by a polynomial shape function. Difficulties and possible solutions to the shape function formulation near excavation edges are discussed. Une des caractéristiques les plus importantes de l’analyse des contraintes minières tabulaires est la nécessité de représenter la complexe évolution des positions du front de taille et des changements concomitants des contraintes occasionnées dans la masse rocheuse. L’intégration de l’activité sismique avec la modélisation numérique requiert des projets souples et efficaces qui permettent la représentation des dommages hors-filon et des glissements de faille à grande échelle. Une approche nouvelle est étudiée qui permet de trouver la fermeture de la taille et les variables de montage en utilisant un estimateur par les moindres carrés mobile. Certains des avantages de cette approche sur les traditionnels projets basés sur une structure en mosaïque sont identifiés. En même temps, les défauts de cette méthode sont notés lorsqu’on calcule la variable de discontinuité du déplacement approximativement par une fonction de forme polynomiale. Les difficultés et solutions possibles à la formulation de la fonction forme près des bords d’excavation sont discutés. Eine der wichtigsten Charaketeristika der taublaren Grubenspannungsanalayse ist die Notwendigkeit, die komplexe Entwicklung der Abbaupositionen und der damit verbundenen induzierten Spannungsänderungen der Gesteinsmasse neu vorzulegen. Die Integration der seismischen Tätigkeit mit einem numerischen Modell erfordert flexible und effiziente Lösungsschemata, in denen sowohl Schäden ausserhalb des Riffs als auch Verwerfungen großen Ausmaßes effektiv dargestellt werden. Ein neuer Vorstoß wird untersucht in welchem die Strossenschliessung und Schneisenvariablen unter Verwendung des Schätzwertes der kleinsten quadratischen Abweichungen (Gaussscher Schätzwert) gefunden werden. Einige Vorteile dieser Annäherung im Vergleich zu der traditionellen Element-basierenden Tessellation sind identifiziert. Gleichzeitig werden Unzulänglichkeiten dieser Methode vermerkt, wenn die Verschiebungsdiskoniuitätsvariable durch eine polynomische Formfunktion angepaßt wird. Schwierigkeiten und mögliche Lösungen zur Formfunktionsformulierung nahe Exkavationsrändern werden besprochen.

Jan 1, 2003

By A. Cambitsis

We show that the prioritization of business improvement and performance management decisions may be significantly improved by taking into account the systemic effects of changes made in a single process area. To do so we build a model of a mining value chain, taking into account consequential downtime that arises from downstream and upstream starvation and choking effects of each activity. Introducing the concept of internal capacity, this approach yields insight into the relative importance of key metrics such as loading and hauling rates. We suggest that a holistic view of this type should be a core component of business improvement and performance management decisions.

Jan 1, 2012

By W. Bleloch

In the process described, hydrogen is used to generate high-temperature steam and oxygen in the molten bath. Steel is decarburized to low levels to produce a pearlite-free steel suitable for deep drawing. The process makes use of the favourable thermodynamics in the reactions between steam, carbon, and iron, as well as providing high-temperature oxygen for the decarburizing reaction. The process can easily be incorporated in existing BOF (basic oxygen furnace) plant but can also be contemplated as a greenfield process.

Jan 1, 1987

By F. P. Agterberg, A. G. Fabbri

"A statistical analysis was done on the locations of 718 copper and 1 257 gold deposits in Abitibi. This area of about 20 000 square miles is one of the better-explored metal-producing areas of Canada.Patterns of clusters were studied by harmonic analysis. Several two-dimensional power spectra showed a number of distinct peaks. Sets of crest lines for patterns of interfering waves were constructed on the basis of these peaks. They pass through elongated clusters of deposits which are spaced more or less equally. For copper these periodic regularities in location may coincide with geological structures largely of Archean age (major fractures and sedimentary belts indicating synclinal structures). A directional relationship with swarms of diabase dykes of known ages and distinct attitudes indicates that the gold mineralization is, in part, younger than the copper mineralization."

Jan 1, 2014

By P. F. S. Jackson, A. Strasheim

In the survey "Analysis of South African raw bullion" the distribution of trace elements within the bullion have been shown to be distinctively dependent on the extraction process. In general the amalgamation process produces the more impure bullion with respect to trace elements. Some chemical and physical explanations are given for the differences that have been observed in the raw bullion as received at the Rand Refinery. The value of the spark source mass spectrographic technique in the study of the elemental impurities in bullion is demonstrated.

By D. A. Singer, J. C. Griffiths

"One of the most useful approaches to a complex problem is to model the system which gives rise to the problem and to perform simulations through the model to find appropriate solutions. The Engel Model may be used as such a simulator to investigate the problem of the exploration for natural resources.The Engel Model is based on a two-stage search procedure in which a known area (A) which contains m prizes is subjected to search by n coverings. During the first-stage search the sensor system records signals which may be a response from prizes (that is, true signals) or may be false. Signals tend to cluster around a prize and a cluster size consists of s signals. If a circle of radius R is drawn around each signal some will overlap and the overlap from s signals contains a prize. The cost of a single covering in which each point of the area comes under observation once, is designated E1. Second-stage detailed search is expensive and is confined to areas of overlap of s circles; it leads to the location of prizes. Second-stage search of the whole area costs Ea units. The expected value, V, of a prize is known and its development cost is E3 units.The sensor system characteristics are defined by the circle of radius R around a signal, which should be small compared with the total area A and enters the model as a parameter a x R2/A. The probability of a false signal during a single covering of a circle of radius I is a known constant, A.This model was applied to the search for uranium ore bodies using two different types of occurrence. In the first, the Wyoming Basin type, the area is relatively large (A = 1 496 square miles) and a few (m = 4) large prizes occur (expected value V = $30 million). In the second area, which represents the Ambrosia Lake region of New Mexico, the area is smaller (A = 212 square miles) and contains many (m = 200) smaller prizes (expectedvalue of a prize V,$2 million). The three costs, E1, E2, E3, are adjusted to the different circumstances in the two areas.Simulations were performed using n = 1 to 40 coverings with cluster sizes s = 0 to 19; the radius R was varied from 0.52 to 3 miles (and, therefore, a = 0.002 to 0.133 0, respectively, dependent on the area of interest). The value of A was varied from 0.01 to 0.10.Profitable programs were found over a wide range of the parameters; the two areas required different strategies to achieve maximum profit. In the Ambrosia Lake region a few passes (n = 4 to 6) with small cluster sizes (s = 2 to 6) are more profitable, whereas in the Wyoming Basin region a large number of passes (n = 35 to 40) and cluster sizes of s = 5 to 10 are most profitable.As pointed out by Allais (1957) the larger prizes are the most important in deciding the successful outcomes of exploration programs, and the profit margin in the search for a few large prizes is sufficient to yield success over a wide range of programs. Such programs require very large investments if they are to be successful.To refine the Engel Simulator as a decision-maker in selecting the most profitable exploration programs it is necessary to obtain firm estimates of the sensor system characteristics, that is, of R, a and ? (lambda)."

Jan 1, 2014

By J. D. Austin, D. G. Kringe

Rates of return realized on investments in the gold mines of the newer goldfields outside the Witwatersrand were calculated and analysed over various time intervals and on various bases. It is shown that these rates of return are strongly correlated with changes in the gold price and cannot be equated with the returns that are expected when investments are made, and that the changes in gold price also affect the rates of return on the Johannesburg Stock Exchange as a whole. These correlations are used, together with a limited application of the Capital Asset Pricing Model, to suggest the expected levels of threshold returns in real terms for new mining projects, for projects on existing mines, and for share valuations.

Jan 1, 1980

By I. M. W. Preston

A new shaft system was required to replace stope face for the North Section of Harmony Mine and to allow for systematic opening up of the North Eastern Section. Owing to the economic circumstances at the time the project started, it became vital to alter the original planning and to sink the service shaft first. The MATLA coal-sinking headgear, a novel presinking arrangement, allowed sinking to continue to 108 m concurrently with the erection of the permanent sinking headgear and sinking winders. It is estimated that this arrangement resulted in a saving of two months on the overall project.

Jan 1, 1983

By S. Schutte, J. Pelders, F. Magweregwede, S. Ngobese, W. Botha

A people-centric, systematic approach that involves different stakeholders is considered necessary to successfully address changes associated with modernizing the South African mining industry. In this paper we discuss the inclusion of various South African mining industry stakeholders, particularly the employees, in equipment design and development processes. Data was acquired through a literature review and inputs from South African mining industry stakeholders through focus group discussions, interviews, and an online survey. It was suggested that some of the areas that could be improved by the inclusion of employees in the process are design quality, ergonomics, equipment acceptance by the workforce, safety, efficiency, skills, insight into context of use, and early design iterations and identification of problems. Among the issues considered to be barriers to inclusion were lack of buy-in, lack of resources, difficulty in manufacturers accessing the mines, difficulties in involving too many people, intellectual property concerns, and unavailability of mine employees due to their key responsibilities. Identified critical factors in the equipment design and development process include iterative design, stakeholder participation throughout the process, needs analysis through consultation, and change management. A guideline was developed for worker inclusion in equipment design and development that could be used by the South African mining industry. The study identified several economic and social benefits of including stakeholders in the early stages of design and development. It is recommended that the South African mining industry considers using the developed guideline.

Apr 5, 2023

By Richard F. Link, Jr. Koch

"A mathematical simulation model has been devised to guide the layout of surface or underground mine workings, drill stations, and drill holes that are established in order to search for tabular ore bodies. The ore bodies may be contained within veins, sedimentary beds (including reefs), or other tabular structures.Programmed for a time-shared digital computer, the model contains both stochastic and deterministic variables. Stochastic or natural variables include the number of ore shoots and their sizes, orientations, locations and values. Deterministic or controllable variables include (i) locations and costs of workings (for underground exploration); (ii) drill station locations and costs; and (iii) drill hole azimuths, inclinations, lengths and deflections (if any).For various assumptions about the natural variables, the model is run while the controllable variables arc changed deliberately. Thus, layouts are devised to determine the percentages of the total number of assumed ore shoots found at different costs. In order to choose among the various layouts, cost-effectiveness measures are calculated."

Jan 1, 2014

By J. Svoboda, W. J. C. Venter, R. N. Guest

SYNOPSIS Wet high-intensity magnetic separation was examined as a method for the recovery of copper and lead from Tsumeb flotation tailings. Bench-scale and pilot-plant tests were conducted and, despite the very low magnetic susceptibilities of all the complex copper and lead minerals, copper and lead recoveries of over 60 per cent and almost 50 per cent respectively were obtained at a combined copper and lead grade of up to 13,5 per cent. The recoveries were found to be practically independent of magnetic induction in the range 0,5 to 2,2 T, and the grade of the magnetic concentrate decreased with increasing magnetic induction. The grade of the magnetic concen¬trate improved when the flowrate of the slurry was increased, and desliming was found to have a profound effect on the. metallurgical process. Particles smaller than 10 µm were not recovered, and their presence in inefficiently deslimed samples impaired the overall performance of the magnetic separation

Jan 1, 1988

By M. J. U. T. Van Wijngaarden

SYNOPSIS The corrosion characteristics of a new steel, 14Cr, which is a modification of the well-known 3CR12, in aqueous sulphate solution were studied through polarization diagrams and a computer analysis based on the polarization¬resistance technique. It was found that the corrosion rate of 14Cr steel is independent of pH for pH values above 6, but, below a pH value of 4, the corrosion rate increases sharply with decreasing pH. In air-saturated solutions of neutral and mildly alkaline pH, the corrosion rate is approximately 60 µm per year. The 14Cr steel shows a twentyfold improvement in corrosion resistance over that of 3CR12 in sulphate solutions at pH 2,0. This is considered to be due to the beneficial effect of its higher chromium and nickel contents.

Jan 1, 1985

By R. M. Morris, G. A. Matthesius, M. J. Desai

Slow pyrolysis experiments were caried out on samples of coal from north em Natal having a volatile mater content ranging between 10 and 25 per cent by mass and a constant particle-size distribution. The tests were conducted at atmospheric pressure in a helium atmosphere, and ata heating rate of 10 KImin and a final temperature of 1220 K. The pyrolysis products were taken as coke and volatile mater (tar and eight other species), and tMir respective yields were measured. The experimental results were used in the modification of an existing mathematical model and in the derivation of new corelations for some of the parameters of the model, so that the volatile products of a coal can be predicted from ultimate and proximate analyses of the coal. The pyrolysis tests showed good agreement between the model predictions and the experimental results.

Jan 1, 1987

By A. Singh, R. D. Govender

The current method employed to quantify the efficiency of separation of ferromagnetic ores by wet low intensity magnetic drum separators (WLIMS) incorporates the use of a conventional benchscale Davis Tube (DT) operating at a magnetic field intensity that is equivalent to that of the drum’s surface. However, empirical research has indicated that the magnetic force, or force index, rather than the magnetic field intensity, is the critical factor in the operation of the magnetic separator (Murariu and Svoboda, 2002). Furthermore, the current aforementioned practice would yield incorrect information as the magnetic field gradients produced by a typical WLIMS unit differs considerably from that of a bench-scale DT. In light of this, research on magnetite focusing primarily on the scale-up of DT results to pilotscale WLIMS were undertaken. The investigation entailed a comparative study between that of a typical WLIMS circuit and a bench-scale DT. The purpose was to practically evaluate the performance of a WLIMS, bench-marked against the traditional laboratory-scale DT unit. Moreover, the secondary objective was to produce a magnetite concentrate graded at 69% Fe, 95% -45μm, as a suitable source of separation media for use in the Dense Medium Separation (DMS) industry. Fundamental findings of previous works provided a framework for the study, however, a realworld approach was explored. Preliminary testwork conducted at Mintek investigated the performance of a DT and a typical multi-stage laboratory-scale WLIMS circuit (operating at 1000 Gauss at the surface). The results attained indicated that a DT operating at high intensities is comparable to a single rougher WLIMS stage. Additionally, it was observed that the three stage laboratory-scale WLIMS circuit performed similarly to the DT operating at 1000 Gauss. Moreover, piloting testwork was undertaken, carried out in larger 380mm drums, and the results attained showed a strong correlation with laboratory-scale findings. Keywords: Davis Tube, wet low intensity magnetic separation, magnetite

Jan 1, 2020

By C. A. Rawlins

Deep underground mines use refrigeration systems to provide a reasonably comfortable ambient environment to increase productivity and to maintain safety as a priority. Deep level gold mines maintain the environment at an acceptable temperature, i.e. 27°C. However, the increasing cost of doing so through refrigeration is becoming a significant factor in the economic viability of mines. This paper discusses of the important facet of energy losses in cooling reticulation systems, laying with the specific emphasis on the subject of chilled water transport pipe insulation and its thermo-dynamic relationships. Aspects relating to the deterioration of open cell-type insulation materials such as polyurethane/styrene foams and the use of Phenolic resins that have good fire retardation properties have been investigated. The thermal conductivities of these insulation media are good (meaning below 0.05 W/°C)However, they are known to be negatively influenced by water vapour ingress and vapour pressure differences that result in the ingress of water into the material by means of absorption, condensation, hygrospicity, permeability and capillary action, to name a few of many. The overall effect on mine cooling efficiency takes in the two forms: first by the loss of refrigeration or increased chill in the water temperature arriving in a given section and second, by a loss in transfer efficiency when the gap between the arriving water temperature and the actual air temperature decreases. Keywords: Conductivity, vapour, insulation, fluid, thermal, temperature, pressure, transport, refrigeration.

Jan 1, 2007

By J. le Grange, M. Tullmin, A. Strauss, F. P. A. Robinson, C. A. O. Henning

An experimental feritic stainless steel with a chromium content of 40 per cent was welded by laser and electron beam (EB) welding processes. These techniques were found to be particularly suited to the welding of this alloy in that the impact toughness of the weld metal and heat-affected zone (HAZ) of the laser welds compared favourably with those of the parent aloy. When the EB process was used, the impact toughness of the weld metal was over 180 J/cm2. Grain growth in the HAZ was minimal for welding with these two processes. Corosion tests, conducted in a solution consisting of 20 per cent sulphuric acid and 100 p.p.m. of potassium thiocyanate, and In a highly corrosive industrial solution, indicated that the laser and EB welds were free of sensitization effects, thus confirming the metalographic results.

Jan 1, 1989

By N. Sinclair

"In open pit dozer bulk push operations, the material left resting against the highwall after blasting poses an issue. This is because dozers cannot physically get in behind the waste to begin the bulk pushing process. Instead, an excavator can be used to side-cast this waste for the dozers to access. An alternative technique is to have the dozers ‘side-cut’ the material, which involves the dozers running parallel to the wall, digging out the material, and eventually rotating their blades to begin bulk pushing. Industry practices suggest the latter technique is less productive and economical than using an excavator. However, such excavator sidecasting ‘economic viability’ assumes that smaller/ancillary type excavators are used (i.e. less than 23 m3 bucket capacity). So, what happens if some mine sites are restricted to using relatively larger excavators (> 23 m3 bucket) that are preferred for higher priority digging tasks? When can they avoid using their excavator? This paper explores multiple scenarios that have been designed and developed to simulate data results, which identify conditions in which the dozer side-cutting technique becomes more economically viable than excavator side-casting in terms of decreased unit cost per loose cubic metre. IntroductionOptimizing the cost of waste removal operations is important for the profitability of opencast coal mines. In the past decade, dozer bulk pushing has emerged and taken over from traditional waste removal operations such as dragline and truck-and-shovel methods at various sites around the world (Beatty, 1994). In a typical bulk push operation, once the bench has been blasted, waste is left resting against the highwall, which can either be cleared using a loading unit or by having the dozers ‘side-cut’ the highwall.Dozers perform most effectively when slot dozing side-by-side, perpendicular to the highwall. However, when dozers are required to remove material off the highwall, they must push parallel to the highwall, rather than perpendicular, hence ‘side-cutting’ the material to ensure a clean face. While dozer sidecutting is possible, it has been found that the majority of mine sites use a loading unit in this situation to avoid dozer inefficiency. Other perceived issues with dozer side-cutting include higher maintenance requirements and safety risks to dozer operators working in close proximity to the highwall."

Jan 1, 2019

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 Roger A. Blais, Michel David

"Matheron's geoslalislical method for the estimation of ore reserves has been developed to the point at which real-life problem may be handled effectively. The steps involved in the method are:(i) obtalning the variogram,(ii) fitting a model, and(iii) producing block estimates.All three steps may cause difficulty, and would-be users need a deep understanding of the theory if failure is to be avoided.To illustrate these points, specific cause are considered:(i) two almost equidimensional porpbyry deposits, one drilled randomly and the other regularly; and(ii) two iron formation, one drilled extensively and being mined, while the other is still at the stage of early estimation."

Jan 1, 2014