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By F. Enslin

Heavy metals and sulphates in acid mine drainage (AMD) can beadsorbed onto bentonite clay, leaving clean water and a heavy metal loaded clay precipitate as products. Due to the toxicity of heavy metals, the clay could not be disposed of safely in the past. A method was thus required to remove the heavy metal content from the clay. Acid leaching was proposed to liberate the heavy metals from the loaded clay. Sulphuric, nitric and hydrochloric acid were considered as lixiviants. Loaded clay samples were leached over a range of pH values from 1 to 3.5 to identify an optimum leaching condition. From the results it was found that metals can berecovered from loaded bentonite clay by means of acid leaching and the optimum pH for heavy metal liberation was found to be 2.5, with uranium as an exception, being optimally leached at a pH of 3. This allows for the possibility of selective leaching. Furthermore, X-ray diffraction analyses indicated that the clay structure did not deteriorate significantly during acid leaching, suggesting that the bentonite could be reused. The treatment of AMD with bentonite clay, and subsequent acid leaching of the clay, is a sustainable solution, and current outcomes could possibly lead to industrial implementation of the process during water purifying and metal recovery from waste streams. Keywords: Acid mine drainage, bentonite, heavy metals.

Jan 1, 2010

The environmental impact of solid waste materials is closely linked to their potential to produce a hazardous leachate once deposited in a landfill. This potential is conventionally assessed with simple laboratory batch leach tests, which find more and more frequent application also in the minerals and metals industry. Such tests are intended to help distinguish between high and low risk wastes, but are completely unsuitable to allow quantitative prediction or modelling of the long-term leachate generation potential. In the present approach the leachate generation process is perceived as a combination of bulk convective transport, stagnant zone and inner particle diffusion, as well as reaction kinetic effects. Model equations are formulated accordingly. A modelling frame work, WASTESIM, has been developed at UCT, which allows flexible combination of the model components and simulation of leach scenarios. Quantitative model parameters are obtained from a systematic laboratory study on the waste material in question. The combined assessment and modelling approach is demonstrated with a study on Cr (VI) leaching from a ferro-chromium slag material. Although not straightforward, the approach is particularly useful in determining long-term liabilities in the context of waste disposal sites with considerably more reliability than has previously been possible. Keywords: waste deposits, waste leaching, heap leaching, environmental, risk assessment, Cr (VI), ferro-chromium, slag.

Jan 1, 2000

By J. N. Van der Merwe

The results of over 900 coal strength tests done during the period 1993?1994 for the SIMRAC project COL021A were re-analysed with a view to find a method to delineate areas or seams that can be grouped together for analyses of coal strength and strength decay characteristics. It was confirmed that the strength of a coal specimen increases linearly with increasing diameter-to-length ratio and decreases exponentially with increasing size of specimen. However, by extrapolation of the data, it was shown that beyond a diameter of approximately 2 m, the size effect is insignificant. For larger specimens, the diameter-to-length ratio (referred to as the width-to-height ratio for full scale mine pillars) alone continues to influence the strength. The slope of the linear strength vs. diameter-to-length ratio relationship is independent of the size of the specimen and is not unique for coals from different mines. However, the intercept of that relationship is unique and is a function of specimen size. This offers a previously unknown method to distinguish between the coals from different mining areas and coal seams. Ranked from weakest to strongest, the samples tested from the different mines are in the order shown below, which roughly corresponds to the judgement of practising rock engineers in the field: ?Sigma ?ZAC ?Goedehoop ?Kriel ?Bank ?Blinkpan ?Secunda ?Greenside Arnot ?Khutala ?Delmas

Jan 1, 2003

By C. Yi, M. Onifade, B. Genc, S. Dineva, T. Zvarivadza, M. Khandelwal

Deep hardrock mines worldwide increasingly face rockbursts as mining depths increase. These events result from the accumulation and sudden release of stress, causing rockmass damage and posing major safety and operational challenges. This paper focuses on destress blasting as a critical strategy to mitigate rockburst hazards. Although limited practical experience exists in Swedish deep hardrock mines, international case studies demonstrate that, when well implemented, destress blasting redistributes peak stresses by promoting controlled fracturing around mining excavations. The success of such techniques is highly dependent on site-specific factors such as stress regime, rockmass brittleness, structural geology, and blast layout. Although destress blasting is especially effective in massive, brittle rock under high stress, typical conditions for strainburst prone environments, its design cannot rely solely on numerical models. Simulations can offer preliminary evaluation of stress redistribution trends and guide early design assessments but their current limitations, including sensitivity to input data and simplified fracture mechanics, mean they are best used as supplementary tools rather than final decision-makers. Field trials, supported by microseismic analysis and fracture mapping, remain essential for validation. The study critically synthesises international experiences and presents a structured framework for destress blasting design, offering practical and academic perspectives aligned with Swedish geological conditions to support safer and more efficient application in deep hardrock mines.

Jun 27, 2025

The paper reviews the results emanating from an experiment conducted in Bochum?Germany in which various international rope inspection authorities were requested to assess the conditions of a corroded rope sample as well as a rope sample containing internal fatigue breaks. Both samples were of the multi-layer low rotation construction.

Jan 1, 2000

By M. Paricheh, M. Rahmanpour

"The cost efficiency and high reliability of semi-mobile or combined in-pit crushing-conveying (IPCC) and truck systems, compared to conventional truck-shovel systems alone, make them more attractive for use in modern mining operations. Semi-mobile systems, which are the most common systems in open-pit mining, combine the advantages of both systems such that fewer trucks are required, operating costs are lowered, and the operation is environmentally sound. One major aspect of utilizing this system is determining the location of the in-pit crusher and the timing of relocations. Facility location models are rarely used in the mining sector, but these models may be used for solving the in-pit crusher location problem. To this end, the main parameters affecting the IPCC location in open pit mines are reviewed and examples given of how they are applied to a dynamic location-relocation problem. Subsequently, the model is implemented for Sungun copper mine in Iran and the number and the exact time of relocations of the IPCC units determined. IntroductionNowadays, compared to the last century, metal prices are more volatile, average and cut-off grades have decreased, and stripping ratios increased. From a mining engineering point of view, many ore deposits with simple access and low capital and operating costs have been exhausted. The remaining deposits are located at depth, with no easy access, which requires high initial capital costs (Osanloo, 2012). Mining at great depths and high tonnages is possible only through open pit mining. Today, more than 80% of open pit mines in the world use a shovel-truck system for loading-hauling operations (Osanloo, 2010).With increasing depth, haulage distances increase and the number of loads per truck decreases. As a result, fuel, tyre, and depreciation costs per ton increase. Owing to these factors, open pit mining at great depth (300 to 1000 m) using shovel-truck systems faces some technical and economic problems. In-pit crushing-conveying (IPCC) systems have been known in the mining industry for many decades. The idea was introduced in 1956 in Germany. Today, the cost efficiency and high reliability of IPCC make it more appealing than conventional shovel-truck operation, especially in longer life projects with lengthy transportation distances and high production rates (Koehler, 2003). Since 1956, different aspects of this system have been reviewed by many researchers. Barua and Lanergan (1985) developed a computer program that compares the tonnage aspects of various conveyor layouts. They believed that to maximize the economic benefit of lower haulage costs associated with in-pit conveying, one must first minimize the cost of the flatter slope, which is expressed in terms of additional stripping or tied-up ore. Dos Santos and Stanisic (1987) evaluated the design of a high-angle conveyor at the Majdanpek copper mine. Then, Sturgul (1987) applied GPSS (general purpose simulation system) to find the best location of an in-pit crusher."

Jan 1, 2017

By B. J. du Plessis

Automation of the conventional grinding circuits of Palabora Mining Company (PMC) required that adequate instrumentation and a control system had to be put in place, after which extensive testing had to be done to evaluate different grinding control strategies. The objective was either to optimize the particle size from the grinding circuit, or to increase milling circuit throughput while maintaining particle size at existing levels. Prior to automation of the process as described below the circuits were controlled manually. No on-line information on cyclone feed densities, cyclone feed flow or cyclone overflow particle size was available. This type of control relied heavily on interpretation of the process parameters by the operator and on his ability to make informed decisions on what the set points should be. An integral component of the automation process was the installation of a SCADA package (SysCad SDX) for implementing the on-line control strategy. A self-correcting model for prediction of cyclone particle size was developed and implemented on the SDX. The model is calibrated using values from the particle size analysers while they are operational. If the particle size analysers choke or fail for any reason, the model continues to provide a good estimate of the particle size. This technique ensures that a continuous particle size indication is available compared to the intermittent reading from the instrument. The continuous signal allows particle size to be used as a process variable for control purposes. A strategy was developed and implemented which allows for the production of a controlled grind size from the conventional milling circuit to the flotation circuit. The grinding control strategy allows for the control of particle size from the individual cyclone overflows. This strategy allows the operator of the process to increase or decrease production rate by specifying a coarser or finer grind size required for flotation.

Jan 1, 2001

High pressure grinding technology has gained further interest in various industries. So far in the mining industry, machines are in operation in diamond mines and iron ore applications. In gold and copper ore processing, test work has been conducted showing considerable operational and process benefits. Similar benefits can be expected from HPGR applications in the platinum industry due to the preferred ore breakage along grain boundaries, thus liberating the PGE particles. This paper will provide an update on the state of high pressure grinding roll technology. Developments in the design of high pressure grinding rolls, for minimized maintenance requirements and availability just as high as conventional mills, will be presented. Plant flow sheets and concepts will be discussed, which allow for a reduction of capital and operating cost in comparison to existing two-stage milling circuits.

Jan 1, 2004

By J. H. Schubert

Mintek has developed a level-control system, FloatStar, for use in flotation circuits. Instead of controlling levels separately in each unit, the controller monitors levels throughout the circuit. It can thus take account of the global effects of any control actions. A collaborative project between Mintek and Karee Platinum Mine has begun, looking at aspects of flotation control. Karee plant was chosen as the site for this work because of its good existing control infrastructure. As a first stage of the joint project FloatStar was installed. Analysis during installation and running of the FloatStar has illustrated how circuit design and measurement technology can affect process control. Severe interactions have been observed in the levels of adjacent banks. The effect of FloatStar on flotation performance was tested and an improvement in level control was observed. Similarly, a faster settling of the plant after start-ups was observed. Both the improved level control and faster start-ups lead to higher platinum recovery.

Jan 1, 1999

By C. N. Harman, N. S. S. Rama Rao

Production of Ferro-alloys through submerged electric arc furnace involves use of electric power as one of the major inputs. Hence the production by this power intensive process can be made economically more competitive if the specific power requirement for smelting each ton of the product is brought down. This becomes all the more necessary where the power cost is comparatively high, like in India. Since the day FACOR started production of Ferro Chrome in 1968, briquetted chromite fines along with lumpy ores were used as feed. Subsequently the increase in the proportion of briquettes and reduction in lumpy ore helped in increasing the use of chromite fines and also brought down the specific power requirement. Meantime FACOR had been closely watching the technical development of use of sintered pellets in Outokumpu and SRC Processes which need still lower specific power. But the high capital requirement for a pelletisation plant kept FACOR from introducing pellets feed to their Ferro chrome furnaces. So this was postponed to be adopted in future. In February 2004 in the ?1st Ferro-Alloys India?, a paper [1] was presented by Dr. Amit Chatterjee. In the questions period after the presentation of the paper there came up a discussion in which it was revealed that with the Indian high grade chrome ores it was not possible to make sufficiently strong pellets, unless a larger percentage of bentonite is used as binder. This is because the Indian high grade Chrome ores have different mineralogy of gangue content compared to low grade ores in Finland and South Africa. Higher usage of bentonite gives rise to higher slag volume and this would result in increased specific power. Since FACOR had plans to go in future for sintered pellets feed, this gave rise to a doubt on success of pelletisation for Indian high-grade chrome ores. This prompted FACOR to take up experimental production of sintered chromite pellets and use of the same in one of their existing furnaces for production of high carbon Ferro chrome. The results are encouraging and are summarized in the paper.

Jan 1, 2007

By Ö. Uysal

This study deals with the presentation of the mechanized longwall mining project introduced some years ago to increase productivity and output of Aegean Lignite Establishment (ELI) owned by Turkish Coal Enterprises (TKI.) and the comparison of this method with a planned alternative new mining method called ?shortwall mining? where continuous miners will be introduced as primary coal excavation machines. Following the planning phase, production costs have been calculated for both mining methods on the basis of a panel having a height of 7.5 m. In addition to cost analysis, both methods have been evaluated using ?the multi-dimensional objective system?. In this evaluation the value synthesis has been carried out according to scoring models. Lastly, the advantages and disadvantages of both production methods have been stated by analysing them according to related criteria. In the light of outputs gathered from the analyses, it has been determined that the shortwall mining method will out perform the longwall method. Keywords: continuous miner, shortwall mining, longwall mining, multi-dimensional objective system.

Jan 1, 2006

By J. G. Bruwer

Paper written on project work carried out in partial fulfilment of B Eng Met Surface coatings persisting on zircon particles, after being leached in an acidic solution, are believed to be the cause of zircon misplacement during the electrostatic separation of heavy mineral beach sands. Electrostatic separation is employed to separate non-conductive zircon particles from more conductive rutile particles. Surface coatings on zircon particles are believed to render the non-conductive zircon particles more conductive, resulting in the contamination of the more conductive rutile stream with zircon particles. Resistivity measurements, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) were performed to compare the surface characteristics of zircon particles found in the different product streams following electrostatic separation. XPS analysis showed that no significant difference exists in the outermost layer of the zircon particles found in the different streams. SEM analysis showed the existing surface coatings on zircon particles from different product streams to have similar chemical compositions. Resistivity measurements confirmed the results obtained from both the XPS and SEM analysis; no significant differences in the resitivities were observed. From the results obtained it suggests that surface coatings present on zircon particles are unlikely the primary cause of zircon misplacement. Zircon losses can possibly be a result of machine related aspects. Key words: XPS; SEM; resistivity measurements; electrostatic separation; heavy mineral sands.

Jan 1, 2007

By S. M. Rupprecht

"SynopsisOver the last decade in South Africa, there has been a significant increase in the number of mining operations, both open pit and underground, which use independent contractors to carry out mining activities. Often mine owners will choose the contractor option without fully understanding the consequences of undertaking this option. Traditionally, contract mining has come at a cost premium of about 15% to 20% compared to an owner mining scenario. However, due to the large number of junior mining companies entering the mining arena in South Africa contract mining rates have increased, with cost premiums as high as 50% being reported. This paper looks at the merits of owner mining versus contract mining and describes under what conditions it may be favourable to select the one option over the other. In addition, the methodology of entering into contract negotiations with the objective of establishing a fair and sustainable relationship is discussed.IntroductionOver the last decade in South Africa, there has been a significant increase in the number of mining operations, both open pit and underground, which use independent contractors to carry out mining activities. Surface mining, for example, may use contractors to conduct drilling and blasting operations or load and haul operations. Underground mining may contract out work such as shaft sinking, mining, support, construction work, cover drilling, sweeping and vampings. Common surface operations such as mineral beneficiation, waste disposal, security, and product transport may also be outsourced to contractors.Many companies have a business model that utilizes contractors for the entire mining cycle, maintaining a small head office to provide direction and control. The difficulty with this option is that often mining companies will choose the contractor option without fully understanding the implications."

Jan 1, 2015

By L. Rademan

The kinetic leaching behaviour of a low-grade surface gold ore and a high-grade reef ore were evaluated to determine the achievable gold recovery from these ores and particularly mixtures of these ores. The reef ore material has a head grade of 13.40 g/t with a relative standard deviation of 3%, and the unprocessed surface ore material a head grade of 0.43 g/t with a relative standard deviation of 15.6%. It is concluded that the kinetic leaching behaviour of these free milling gold ores during cyanidation, is not influenced by mixing of reef and surface ore material. No statistically significant relationship exists between the achievable recovery by direct cyanidation and the head grade of the material fed. No ideal ratio of surface ore to reef ore could be established. It is recommended that these materials should be processed simultaneously to minimize the costs, security risks, and losses incurred in transportation.

Jan 1, 2012

By M. Wong-Kian, L. A. Cornish, A. van Bennekom

Samples of four different satellite materials were prepared by either hot isostatic pressing (HIP) of the powder or tungsten inert-gas welding of rod onto a 316 L stainless-steel substrate. The samples were subjected to a series of comparative erosion corrosion tests, and generally the Hipped samples experienced between 13 and 24 per cent less loss in mass than the equivalent welded alloys. Resistance to erosion corrosion increased with increasing carbon, chromium, and tungsten contents. Metallographic studies indicated the differences in carbide content between the different satellite materials, and the differences in morphology between the Hipped and welded samples. Finer and more homogeneous microstructures were

Jan 1, 1995

By R. E. Robinson

A novel variation of the GYPCIX process for the treatment of the acid mine effluent water from Grootvlei is described, in which a number of valuable by products can be obtained and the product water can be used for a variety of different purposes. A conceptual case study is presented in which the important cost parameters are described and certain critical path activities are indicated in order to derive a Return on Investment evaluation according to methods previously published. The study indicates that the treatment costs can be dramatically reduced, provided that proper utilization of the by products is taken into account. There are many possible uses for the water. However, by far the most advantageous contribution to the RDP and the best return on capital is derived if the water is used to establish small-lot farming activities providing work opportunities for thousands of people and contributing several hundred million Rands to the GDP. Vastly improved social conditions will be generated in an area of Gauteng that is in danger of rapid deterioration and a contribution will be made to maintaining mining activities in this area. The environmental impact is positive.

Jan 1, 1998

By D. J. Greeff

By making use of genetic programming, empirical models for metallurgical processes can be evolved that are more cost-effective than models determined by means of classical statistical techniques. These methods explore populations of candidate models assembled from sets of variables, parameters and simple mathematical operators, and do not require explicit specification of model structures. The application of the proposed strategies is illustrated by means of a case study pertaining to the leaching of nickeliferous chromite ores. Modelling of the nickel and cobalt extraction from the ores yielded models of similar accuracy compared to those obtained by non-linear regression and artificial neural networks. However, in the case of the iron extraction from the ores, the genetic programming model was significantly more accurate than both the regression and neutral network models.

Jan 1, 1998

Mr K.R. Beard was born on 19th December, 1958. He attended Marist Brothers College, Observatory, and Marist Brothers College, Linmeyer. He was awarded a bursary by SEIFSA (Steel and Engineering Industries Federation of South Africa) and gained the degree of B.Sc. Eng. metallurgy at the University of the Witwatersrand in 1982. He is a member of the Engineers' Society of South Africa. Mr G.A. Brown was born on 27th June, 1934, and matriculated at St John's College. He obtained the degrees of RSc. Eng. (Met.) at the University of the Witwatersrand in 1957, and M. Met. at Sheffield University in 1959. He is a member of the Institution of Mining and Metallurgy (UK) and the Society of Mining Engineers (USA). Or LA. Cramer was born in the USA and, having received a B.Sc. degree in metallurgical engineering from the Colorado School of Mines, he emigrated to South Africa in 1971. He enrolled as a graduate student at the University of Natal and successfully completed both an M.Sc. and a Ph.D. degree in chemical engineering.

Jan 1, 1989

By T. S. Seleka

Laser surface melting has been conducted on a 304 stainless steel (SS) with the aim of enhancing pitting corrosion resistance of the material. This process involves rapid melting of the material?s surface followed by rapid solidification to refine the microstructure. This includes the dissolution of inclusions such as MnS, FeS, CrxCy, and other minor constituents. The microstructures as a result of laser treatment were observed by means of optical microscope and also confirmed by the XRD. The glow discharge optical emission spectroscopy (GDOES) was utilized for chemical analysis. Changes in hardness were observed by using a Vickers microhardness tester. Pitting corrosion tests on laser treated and untreated samples were conducted according to ASTM G48-92 to evaluate mass loss and pitting morphology. Laser surface melting improved the pitting corrosion resistance of this material in a chloride-containing environment.

Jan 1, 2007

By E. V. Lilford

Valuators of mineral properties are faced with a range of valuation methodologies, the most important of which are grouped under the headings of the market approach, the cost approach and the income approach. The way in which value is defined and the detail of the different valuation methodologies is examined here. This paper aims at documenting the variety of valuation procedures and applying each method to a variety of gold projects and comparing the outcomes. Any decision to apply a valuation technique will depend principally on the stage to which the project has been developed. The valuation approach to a greenfield project will be substantially different from that applied to a well-drilled, extensively explored mineral property. Furthermore, a valuation exercise may produce different outcomes for the same gold project depending on which method is applied. In order to investigate the variability in valuation methods and to explore the outcomes of different approaches, a series of five gold projects was analysed. The projects differ in regard to levels of capital application, infrastructural setting, depth below surface, in situ grade, and the stage of development, and were valued using the different methods. The most critical aspect of any valuation is the capacity of the valuer to identify the salient issues and ensure that they are incorporated into the valuation. The danger of simply applying ?black box? solutions to valuation problems without a full understanding of the parameters and the areas of uncertainty is emphasized. The importance of the valuator?s experience, insights into best practice and the ability to recognize and submit to the requirements of compliance within the minerals industry is among the most important characteristics of a valuer.

Jan 1, 2005