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By A. Hoogervorst

Cyanide is a key contributor to the efficiency of gold extraction. Public perceptions of cyanide are emotive and following some publicised incidents involving cyanide, the gold mining industry established a voluntary cyanide code for the manufacture, transport and use of cyanide in the production of gold. The paper describes the development of the code, its content and the third party auditing of the code as a means of establishing and maintaining benchmark standards. In adhering to the cyanide code requirements, there are overlaps with other management systems such as ISO 14001 and OHASA 18001 and the paper seeks to show how existing mine systems can readily accommodate cyanide code compliance and that operating and auditing the cyanide code can assist in the integration of mine heath, safety and environmental management systems.

Jan 1, 2009

By M. Karsten

Platinum mines in the Bushveld Complex are located in areas with a high geothermal gradient. This means that, compared to, for example, gold mines of the Witwatersrand region, high rock temperatures are encountered at relatively shallower depths. Thus air cooling and refrigeration need to be considered at early stages in mine development. Another factor that influences air cooling and ventilation requirements is the use of trackless diesel equipment for loading and hauling broken rock. At shallower depths it will be more cost-effective to locate the cooling and ventilation equipment on surface, whereas for deeper mines the more cost-effective option is to locate cooling equipment underground. For intermediate depths, trade-off studies need to be undertaken to determine the optimum mix between more cooling and less air or more air and less cooling, as well as the optimum location for this cooling equipment. Factors that are taken into account include power requirements, positional efficiency, and additional infrastructure requirements. Traditionally the approach has been to ventilate ?all of the mine all of the time?. However, with increasing power costs and growing pressure to ensure sustainability, this strategy must be modified to apply ventilation and cooling on demand. In other words, both cooling and ventilation equipment should be operated only when needed and should be adjusted to the demand at the time. Obviously there will be areas that will need to be ventilated (and cooled) continuously (for example, for dilution of flammable gases), but this can be built in to the overall strategy. In addition, in devising ventilation on demand (VoD) strategies, occupational criteria relating to exposure to gases, noise, and heat need to be taken into account. This paper discusses options available for implementing energy-efficient ventilation and cooling systems and suggests ways of changing traditional thinking in the overall ventilation and cooling of mines. Efficient ventilation and cooling designs can play a major role in improving sustainability and reducing energy costs and carbon footprint.

Jan 1, 2012

By B. Friedrich, A. Birich

Gold has been a metal of special importance for mankind for several thousand years. Its outstanding chemical resistance is an important property of this noble metal, but becomes a disadvantage when it comes to gold recovery. The established processes are based on highly aggressive and toxic reagents. Different alternative leaching reagents with a significantly lower toxicity proved to be promising alternatives in the last decades. Major research activities in this field focused on gold ores, so that leaching of secondary resources were not described sufficiently. Based on literature research and extensive experimental investigations, a reagent assessment was conducted for hydrometallurgical gold recovery from electronic waste. It was found that besides thiourea and halides, thiosulfate in particular represents an alternative of major relevance. A variety of different electronic waste (e-waste) specimens were investigated to identify suitable leaching conditions. As a result, an almost complete and selective gold recovery in less than 48 hours from different electronic waste types and components was achieved by thiosulfate leaching. Within the experiments conducted, it was found that the leaching behaviour of cyanide alternative lixiviants differ strongly from leaching of primary ores. Keywords: Gold leaching, cyanide alternative, thiosulfate, electronic waste

Jan 1, 2020

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 D. Farrow

Future development of kimberlite mines is now focused on mining at deeper levels. The consequences are increased difficulty and costs of the mining operations. The decisions on investments require accurate resource evaluation and quantification of the risk. In the decision process the first step consists in choosing the number of boreholes sampling the pipe relative to the level of uncertainty that can be accepted. The uncertainty in the volumes of rocks of different types can be assessed as soon as we can estimate these volumes from a given borehole layout and calculate the error by means of its variance for instance. In theory this can be achieved by using geostatistical techniques (‘transitive theory’), but in practice the calculation of the error on volumes can be achieved in very particular cases, assuming some regular sampling patterns. A different approach has been chosen based on simulations, giving maximum flexibility to reproduce the reality of the sampling procedure. The idea is to simulate the geometry of several ‘possible’ pipes with their internal geology and estimate them by kriging. Several experimental errors are obtained on which risk analysis can be performed. The aim is to find a feasible method to perform the simulations with reasonable chance to correctly represent the reality, without data on the pipe extension. The methodology applied is based on some hypotheses that can be assessed by the geologist as well as by the geostatistician. The procedure assumes a geological model based on current knowledge including appropriate geostatistical variation. What make these simulations specific and powerful in this case comes from the fact that the boundaries between the different rock-types can be simulated using a transformation of the real 3D space into a 2D space defined by means of polar coordinates. Ultimate transformations to account for smoother variations with morphological transformations allow the generation of realistic pipe geometries on which sampling pattern can be used to evaluate the estimation errors. By estimating the simulated pipe geometries with different boreholes layouts a risk curve expressing the uncertainty in the volumes of the different rock-types versus the number of holes can be developed.

Jan 1, 2003

By D. Duncanson, R. J. Davidson, C. G. S. Schmidt, G. A. Brown, J. D. Taylor, N. W. Hanf

The development of a cyanidation route for the treatment of gold-plant gravity concentrates is described. This work was carried out as a natural consequence of earlier improvements to the recovery of gold in the gravity sections of existing gold plants. Concern about the environmental aspects of the conventional amalgamation process was further motivation in the development of an alternative procedure. It was found that the partial pressure of oxygen in solution was the most critical reactionrate determining factor. The rate of gold dissolution was shown to be controlled by the reaction rate below approximately 25°C and by diffusion above that temperature. Thus, the efficiency of pulp agitation and oxygen partial pressure permitted a high degree of control over the rate of gold dissolution. The use of oxygen rather than air significantly increased the dissolution rate of both gold and silver. The solubilities of sodium, calcium, and potassium aurocyanide complexes under simulated reaction conditions were studied, and it was established that the values for the sodium and calcium complexes were limited, requiring the use of lower pulp densities and higher reaction temperatures for the treatment of very high-grade concentrates. The presence of excessive amounts of tramp iron in such concentrates of up to 25 per cent by mass was found to result in poor gold dissolution owing to the cementation of gold under certain reaction conditions. The maintenance of high oxygen partial pressures, together with high cyanide concentrations, high pH levels, and the presence of calcium in the system, all aided in passivating the tramp iron. Copper, gold, and iron were shown to be the main cyanide-consuming elements. Optimum gold dissolution was obtained in a closed bench-scale reactor incorporating a flotation-machine type of agitator for effective pulp agitation and oxygenation, the oxygen being recirculated. The reactor was designed to operate under a very small positive pressure. After reaction times of 2 to 6 hours at temperatures in the region of 30°C, both the gold and the silver dissolution averaged 99,S per cent. In the case of very high-grade concentrates, it was shown that gold could be floated in the same reactor by drawing off the flotation concentrate through a port in the reactor. A flotation recovery of 87,4 per cent of the gold in 3,9 per cent by mass was obtained. The recovery of osmiridium from cyanide-leach residues and the electrowinning of gold from the pregnant liquors were also considered as processing aspects in the treatment of gold-plant belt concentrates. Final table tailings with a gold concentration of 10to 12 gft were obtained. The results of the investigation strongly suggested that an alternative cyanidation route for the treatment of gold-plant concentrates was technically feasible, provided the system included effective agitation and oxygenation. In the case of lower-grade concentrates, cyanidation followed by the electrowinning of gold appears to be the simplest route, while, for high-grade concentrates, flotation and smelting of the concentrate followed by cyanidation of the flotation tailings are suggested. The use of oxygen rather than air for sparging the pulp would depend largely on the grade of material to be treated. A preliminary comparison of the costs related to the amalgamation and cyanidation processes for the recovery of gold from such concentrates indicated very similar capital and operating costs. It was concluded that other considerations, e.g. toxicity, safety, and lower labour requirements, were more important than such small cost differences. Furthermore, the 'opening' of the gold-plant gravity circuit, which would be made possible by a cyanidation route, would further reduce the operating costs because of the subsequent decrease in the tonnage to be treated.

Jan 1, 1978

By R. C. W. Webber-Youngman

The mining industry in South Africa faces real challenges with regard to the reduction of safety-related incidents. The purpose of this paper is to highlight the need for alternative interventions in addition to other safety improvement strategies already employed on mines. It furthermore supports an existing paradigm: incident investigations. An investigation into fatalities in the South African mining industry shows that although great progress has been achieved through the reduction in fatalities in all sectors of the industry over the last few years, more can and should be done to achieve status of ?zero harm?. Fatalities and lost time injuries on mines result not only in large financial losses, but also in disruptions of mining operations in general through Section 54 stoppages to resolve the situation. The approach of the paper is therefore not to try and prove whether there is high fatality rate and/or lost time injuries, but in what way incident reconstruction simulations (IRS) can have an impact in the future prevention of such incidents. The challenge therefore lies in the utilization of pro-active systems that would show employees the possible outcomes of being exposed to certain hazards. In real life, these incidents cannot be re-enacted and in most cases we can only learn through the previous mistakes of others. A virtual reality (VR) education and training system will enable employees to be ?exposed? to different hazards in a safe environment, and simulation, in a ?forgiving? environment, of the possible consequences of unsafe acts. According to the Occupational Safety and Health Act (OSHA), unsafe acts and unsafe conditions are indirect causes of safety-related incidents, but there are also direct causes; for example, unplanned release of energy and/or hazardous material, and basic causes, for example, management safety policies, personal factors, and environmental factors. The administrative workload associated with any incident investigation places a large burden on the investigation team, and in most cases other employees are informed through vague administrative processes what the ?real cause? for the incident/accident was. New preventative strategies are often put in place without showing the employees what the real causes of the incident/accident were. This can be mitigated through the use of interactive VR simulations/animations of the hazards that they are exposed to and how to deal with them. If VR interventions are not used as proposed by this paper, the real causes and consequences of almost all fatalities and lost time injuries may never be fully understood. This paper also emphasizes what potential impact IRS could have on the prevention of future mine incidents as part and parcel of a pro-active risk prevention strategy. The intention is therefore not to replace any other risk prevention strategies, but to visually enhance the reality of the incident. Keywords virtual reality, risk management, incident reconstruction simulations, interactive safety training, usability context analysis, mine safety.

Jun 1, 2013

By G. Chunnett

Platinum metal prices have risen significantly during the past 18 months, and have remained at elevated levels. Driving these bullish prices are sustained jewellery demand, mainly from the Far Eastern markets, and ongoing autocatalyst usage in response to ever more demanding global environmental legislative requirements. Within South Africa, the areas north and south of the Steelpoort River in the Eastern Bushveldare well known for their significant resources of platinum. The bulk of the resources have lain dormant in anticipation of the very situation that is currently occurring in the marketplace. Anglo Platinum is the largest primary platinum producer in the country, and is uniquely positioned to take advantage of the current elevated metal prices and shortfall in supply of platiniferous metals. In addition to its production capabilities, Anglo Platinum holds an extensive portfolio of mineral reserves and resources which underpin its ability to implement expansion projects to continue growth in platinum group metal production. It also has access to, and is actively expediting, the exploration of a range of properties where the company can further expand current production capacity or supplemented depleted production levels.

Jan 1, 2006

By J. Danoczi

South Africa is running out of fresh water and is looking at ways to improve water usage. This report addresses how a diamond mine in Gauteng has improved the utilization of its water resources. In the past, water from the local river was deemed the most suitable to use in the grease recovery plant but subsequent tests on the water from the slimes dam have shows that this water source is in fact more suitable for diamond recovery. Utilizing the slimes dam water provides a more stable water source than the local river while also reducing the impact of the mine on the water resources in the area.

Jan 1, 2008

By D. G. Almond

Low-grade, complex mineral deposits have resulted in the need for complicated large-throughput processing plants delivering increased productivity, reliability, and utilization, together with reducing operational costs. Complex mineralogy has resulted in complicated process flow sheets designed to recover minerals as efficiently as possible. In addition, the remote location of many minerals¬-processing plants, continuously rising energy costs, and fierce competition pose significant challenges to the modern mine, compounded by a global scarcity of qualified and experienced operational personnel. Over the last decade the Internet and automation technologies have undergone major advancements. Automation technologies, solutions, and concepts that existed, but were considered risky or unreliable prior to the year 2000, have now gained acceptance and matured. Furthermore, new technologies and different collaboration schemes have appeared, offering innovative solutions to the mining industry to address many of the challenges described. These advancements in reliable remote systems that access technology through the Internet provide significant opportunity to support mining operations, enhance process performance, provide engineering services, and proactively anticipate and execute maintenance services. This paper references a global survey of automation trends in the mining industry and the potential for an intelligent collaborative environment using automation technologies to exploit opportunities in operating the plant of the future, increasing effectiveness, and reducing operational costs. A variety of possibilities are described, including asset management solutions, remote access capabilities, performance monitoring solutions, advanced process control technologies, and the formation of an intelligent collaborative environment. A real example where this technology is used to support the operation and maintenance at a cement plant in Egypt is given to underpin the concepts described in this paper.

Jan 1, 2013

By S. C. Everett, I. S. Schache, P. A. Bannister, G. F. Balderson

The Pooncarie Project is located in the Murray Basin region of Australia. This region is a potential new mineral sands province. Due to the geological environment and the lithology of the deposit, these deposits have some technical challenges that need to be addressed prior to their successful development. Within the Pooncarie Project the Ginkgo deposit will be developed first. The technical challenges it presents include its geographical isolation, the requirement to remove substantial quantities of overburden as well as the processing issues raised by the highly weathered nature of the ilmenite family of minerals. Ore characterization bench scale testwork and bulk sample pilot plant programmes have been carried out and the data obtained used to design flowsheets for both the wet plant and mineral separation plant circuits with the flexibility to enable these plants to handle the variable heavy mineral assemblage. In addition to the solving of the processing challenges, technical issues such as removal of overburden for the minimum unit cost, the use of hyper saline water in the dredge pond and the provision of infrastructure, have had to be addressed. None the less, the orebodies making up the Pooncarie Project have many positive features including low slimes content, good rutile and zircon grades and the ability to recover most of the ilmenite family of minerals into acceptable TiO2pigment feedstocks. The development of the project is set to proceed with the establishment of mining operations on the Ginkgo orebody feeding a mineral separation plant at Broken Hill. The initial shipment of products is expected to occur in early 2005.

Jan 1, 2003

By V. Léveillé

As new legislation drives metallurgical plants to lower SO2 emissions, plant managers face the challenge of keeping their costs under control. The Cansolv® SO2 Scrubbing System has been broadly adopted in the non-ferrous industry as a cost-effective solution for smelter operators to meet the new SO2 emissions targets. The Cansolv® SO2 Scrubbing System is an a mine-based regenerable process that selectively absorbs SO2 from a variety of gases, including dilute smelter gases, such as furnace and converter gases. The system produces a pure, water-saturated SO2 by-product stream, which can then be directed to the front end of a sulphuric acid plant for conversion to sulphuric acid. When deployed in a smelter complex, the Cansolv® SO2 Scrubbing System may also be used to process acid plant tail gas, allowing single absorption sulphuric acid plants to achieve emissions an order of magnitude lower than that of a double absorption acid plant with a lower capital investment. Depending on inlet gas temperature, SO2 emissions in the treated gas can be controlled to as low as 55mg/Nm3. This paper will describe some of the applications where customers have or are planning to use the Cansolv® SO2 Scrubbing System, as well as which features and cost advantages for the treatment of smelter gases were important in the technology choice.

Jan 1, 2009

A high volume of slimes which are separated out during the mining of heavy mineral sands has a high environmental impact and results in great capital as well as operational expenses. The presence of clay minerals drastically increases the slimes volume that needs to be catered for due to its low settling capability as well as swelling characteristics. By adding coagulants in the form of cations and organics, one can improve the settling rate of the minerals as well as the degree of solid bed compaction. The addition of flocculant, which is currently used in industry to improve settling rate, is detrimental to solid bed compaction. By combining the cations and flocculant one can dramatically improve the solid bed compaction. This combination is, however, detrimental to the settling rate of kaolinite-rich slimes but improves the settling rate of smectite-rich slimes. Organics can also be used to produce a clear supernatant and improve the settling rate.

Jan 1, 2010

By K. Thambi

"A recent amendment to Section 36(11)(e) of the Income Tax Act, 53 of 1968 (Tax Act) now extends the allowable deduction of ‘capital expenditure’ incurred by mining companies pursuant to the Mineral and Petroleum Resources Development Act 28 of 2002 (MPRDA). In terms of the Taxation Laws Amendment Bill 2016 (TLAB 2016), the allowable deduction has been extended to include expenditure incurred on infrastructure in terms of Social and Labour Plan (SLP) requirements as per the MPRDA. Interestingly, what necessitated the amendment was the need to recognize SLP requirements and to circumvent administrative difficulties for mining companies and the South African Revenue Services (SARS) in differentiating the use of developmental infrastructure by employees or the community. The successful implementation of such a deduction hinges on a sound SLP system. However, given the challenges within the current SLP system, this amendment could be considered somewhat premature. IntroductionSection 36(11) of the Income Tax Act 58 of 1962 (Tax Act) enabled mining companies to deduct certain capital expenditure in lieu of its other sections. In particular, it made provision for mining companies to deduct capital expenditure incurred pursuant to the Mineral and Petroleum Resources Development Act 28 of 2002 (MPRDA), but excluding capital expenditure incurred in respect of infrastructure or environmental rehabilitation. As such, mining companies could only deduct such capital expenditure that related directly to their employees and not to the wider community (Clegg, 2018).In terms of the Taxation Laws Amendment Bill 2016 (TLAB, 2016) (South Africa, 2016a), the recent amendment to Section 36 extends the relief provided under section 36(11)(e) to include capital expenditure incurred on infrastructure in terms of the Social and Labour Plan (SLP) requirements of the MPRDA. In other words, the capital expenditure incurred by the mining company for the benefit of the people living in mining communities. To qualify for such a deduction, the infrastructure erected or developed by the mining company should reflect what was agreed between the mining company and the Department of Mineral Resources (DMR) as per the SLP requirements of the MPRDA (TLAB 2016)."

May 1, 2019

By H. Zhong, S. Wang, Q. Sun

The flotation performance of 2-(benzylthio)-acetohydroxamic acid (BTHA) to diaspore was first evaluated by micro-flotation tests. The adsorption mechanism was further investigated through adsorption experiments, molecular dynamics simulation, zeta potential and X-ray photoelectron spectroscopy (XPS). The results demonstrated that BTHA had a stronger ability to collect diaspore in comparison with another diaspore collector, benzohydroxamic acid (BHA), especially under the condition of weak alkalinity, the flotation recovery can reach 90%. The more negative interaction energy (ΔE) between BTHA and diaspore from molecular dynamics simulation results revealed that BTHA had an easier adsorption ablity onto diaspore than BHA, which matched with adsorption results. The zeta potential and XPS revealed that Al atoms might bond with -C(=O)NHOH by formation of Al-O bonds. Keywords: Diaspore, flotation; adsorption; 2-(benzylthio)-acetohydroxamic acid

Jan 1, 2020

By Z. Botha

Sheryl Sandberg, the COO of Facebook, published a book titled 'Lean In', where she invites women to sit at the table. In summary, to 'sit at the table' entails not only embracing opportunity, but to actively seek out opportunities in leadership positions. Sandberg points out that, unfortunately, apart from institutional obstacles, a woman's own perceived limitations have a negative impact on her leadership ambitions. To create an environment where diversity will flourish, where everyone has a seat at the table and everyone has a voice, safety must be established first. To establish safety within a diverse team, there is power in relationships and connections. This study will first and foremost review theories in literature as to why diversity and inclusion are so important and the value that diversity brings to our industry. The study also recommends a few focus areas for improving diversity and inclusion in the industry.

Sep 1, 2022

By Y. H. Hatzor

ABSTRACT: A fully dynamic, two dimensional, stability analysis of a highly discontinuous rock slope is demonstrated in this paper. The studied rock slope is the upper terrace of King Herod’s Palace in Masada, situated on the western margins of the seismically active Dead Sea Rift. The dynamic deformation of the slope is calculated using a fully dynamic version of DDA in which time dependent acceleration is used as input. The analytically determined failure modes of critical keyblocks in the jointed rock slope are clearly predicted by DDA at the end of the dynamic calculation. It is found however that for realistic displacement estimates some amount of energy dissipation must be introduced into the otherwise fully elastic, un-damped, DDA formulation. Comparison of predicted damage with actual slope performance over historic time span window of 2000 years allows us to conclude that introduction of 2% kinetic damping should suffice for realistic damage predictions. This conclusion is in agreement with recent results of Tsesarsky, Hatzor and Sitar (2002) who compared displacements of a single block on an inclined plane subjected to dynamic loading obtained by DDA and by shaking table experiments. Using dynamic DDA it is shown that introduction of a simple rock bolting pattern completely stabilizes the slope. RÉSUMÉ : On présente dans cet article une analyse bidimensionnelle complète de la stabilité d’une pente rocheuse très fracturée. La pente rocheuse étudiée est la terrasse supérieure du Palais du roi Hérode à Massada, située sur la rive Ouest du Rift sismiquement actif de la Mer Morte. La pente est constituée de blocs de dolomite raide présentant une stratification sub-horizontale et des joints sub-verticaux. La déformation dynamique de la pente est calculée en utilisant une version entièrement dynamique de l’Analyse de Déformation Discontinue (DDA) où l’accélération dépendant du temps est utilisée comme donnée. Les modes de rupture déterminés analytiquement des blocs clés dans la pente rocheuse fracturée sont clairement prévus par l’approche DDA à la fin du calcul dynamique. On trouve cependant, que pour obtenir des estimations réalistes du déplacement, il faut introduire un facteur de dissipation énergétique sans lequel la formulation DDA serait totalement élastique et sans amortissement. En comparant l’endommagement prévu avec les caractéristiques de la pente sur une période historique de 2000 ans, nous pouvons conclure que l’introduction d’un amortissement cinématique de 2% suffit pour obtenir de prévisions réalistes. Cette conclusion est conforme aux résultats récents de Tsesarsky, Hatzor and Sitar (2002) qui ont comparé les déplacements d’un bloc isolé sur un plan incliné sous chargement dynamique obtenus avec l’analyse DDA et à partir d’essais sur table vibrante. ZUSAMMENFASSUNG: En utilisant une modélisation DDA dynamique on montre que l’introduction d’un système simple de boulonnage stabilise la pente.In dieser Veroeffentlichung wird eine vollstaendig dynamische, zweidimensionale Stabilitaetsanalyse eines hoechst diskontinuierlichen Steinhangs dargestellt. Der untersuchte Hang ist die obere Terrasse des Herodespalastes in Massada, welche in den westlichen Randgebieten des seismisch aktiven Toten Meer Grabens liegt.Die dynamische Deformation des Berghangs wird mit Hilfe einer vollstaendig dynamischen DDA-Version berechnet, in welcher als Input die zeitabhaengige Beschleunigung eingegeben wird. Die analytisch bestimmten Versagensarten kritischer Schluesselbloecke in diesem zerkluefteten Steinhang werden durch Anwendung von DDA am Ende der dynamischen Berechnung klar vorausgesagt. Es zeigt sich jedoch, dass fuer realistische Dislozierungs-Abschaetzungen ein gewisses Mass an Energieverlust in der sonst vollstaendig elastischen, ungedaempften DDA-Fassung einbezogen werden muss. Der Vergleich des vorhergesagten Schadens mit dem aktuellen Verhalten des Berghangs waehrend einer historischen Zeitspanne von 2000 Jahren erlaubt uns zu schliessen, dass ein Zusatz von 2% kinetischer Daempfung fuer eine realistische Vorhersage des Schadens ausreichen sollte. Diese Schlussfolgerung steht im Einvernehmen mit neuen Ergebnissen von Tsesarsky, Hatzor und Sitar (2002), welche die Dislozierung eines einzelnen Blocks auf geneigter Ebene unter dynamischer Belastung – unter Anwendung von DDA und “shaking table”-Versuchen – verglichen. Mit Hilfe der dynamischen DDA wird gezeigt, dass der Steinhang durch Anwendung einer einfachen Steinschraubenstruktur vollkommen stabilisiert werden kann.

Jan 1, 2003

By A. Koning

Pressure hydrometallurgy operations require vessels to be lined with an impermeable membrane for corrosion protection and one or more courses of refractory or ceramic brick. Examples of unit operations that utilize composite lining systems include pressure oxidation autoclaves, sulphide precipitation autoclaves, chloride leach reactors, flash vessels, cyclone separators, and direct contact condensers (heater vessels and quench vessels). The refractory lining must satisfy multiple requirements: it must thermally insulate the membrane from process fluid, be structurally stable, provide erosion resistance, be chemically compatible with process fluid, and provide an economic service life. New hydrometallurgical processes are pushing the pressure, and temperature with each new generation of plants. A fundamental understanding of all factors affecting the mechanical stability of the lining system is essential as lining designs move further away from the industry?s experience base. The method of designing a refractory lined vessel is examined taking into account the impact of irreversible chemical swell, operating factors, design factors, and installation factors. The effect of geometry and incorporating additional degrees of freedom to the analysis is explored using two-dimensional and three-dimensional finite element analysis (FEA). The effect of these additional degrees of freedom on the results of the one-dimensional model are discussed. Keywords refractory lining design,autoclave, finite element analysis.

Aug 1, 2013

By H. Moslemi

Metal sulphides are usually semiconductor and their electrical conductivity is low; therefore they are sources of electrons and promote electrochemical reactions. This phenomenon is of significant importance in sulphide flotation. The formation of a hydrophobic surface on the sulphide minerals is the result of various electrochemical reactions. Potential difference in the mineral-liquid interface plays an important role in the kinetics of the reactions, and consequently, on the flotation behaviour of sulphides. The value of the potential difference is influenced by different oxidation-reduction reactions at the interface area, and is measured by a two-electrode system in which an electrode is applied as reference electrode. In this study, we attempted to measure open-circuit potentials of pyrite, pyrrhotite, and steel electrodes with respect to the reference electrode. To verify the results, two reference electrodes, saturated calomel and gold, were used. Time-potential relations with respect to both reference electrodes show that the potential of both pyrite and pyrrhotite increases with time; however, this trend decreases for steel except when at pH 12. The results show a potential drop by an increase in pH value, except for steel, for which the opposite holds. This paper discusses galvanic interactions between minerals and grinding media in the grinding circuits, as well as among other minerals in the flotation processes.

Jan 1, 2012

Geological mapping makes an important contribution to orebody knowledge during the evaluation of structurally controlled gold veins. Orebody knowledge comprises an understanding of mineralization characteristics relevant to evaluation, mining, processing and environmental issues and allows project expectations to be realistically set. Structural interpretation to define continuity and mineralization controls is a key part of geological risk reduction and the reporting mineral resources using the JORC and other codes. The Dolgellau gold belt is a small British field that produced an estimated 150 000 oz from narrow quartz veins. Historical records, recent exploration and production data, published material, and accessible surface and underground exposure provide a valuable case study. Previous mapping has shown the general geometry of vein systems, but tends to accentuate gross geological continuity. Recent work has attempted to determine internal vein architecture and examine the significance of the historical views of ore shoot controls. The work resulted in the definition of vein continuity scenarios for the gold belt and evaluation expectations associated with each. This has, in turn, led to a realistic view of what can be achieved from an evaluation and project development perspective.

Jan 1, 2009