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By D. G. Krige

Using chip sample data and spatial structure parameters from a large mined-out section of a South African gold mine the advantages to be gained from a regular underground borehole drilling programme have been investigated for short- and medium- to long-term planning based on block valuations. The results have been compared with the current position, which relies invariably on the extrapolation of limited peripheral sampling data from raises, gullies or stope faces. Some preliminary work has also been done regarding the implications of such underground drilling on costs used for the present pay limit calculations. The results of the study, though preliminary, show that the net advantage of advance regular underground drilling could be substantial and that a more intensive follow-up research is warranted.

Jan 1, 2003

By R. C. D. Phillis

The management of critical resource inventories is an important productivity lever and a significant risk factor?risk in the sense that poor resource availability lends itself to disempowerment of workers, unsafe work practices, wasted spending (high unit costs),and poor quality of work (including mining waste/rework). Most underground platinum mines experience lost blasts that directly lead to reduced productivity. In most surveyed shafts, 30% of lost blasts can be attributed to shortages of critical material and/or equipment. The problem is prevalent despite the existence of conventional transitory surface and underground stores. This paper discusses the introduction of buffer stores as a complementary materials storage system in order to improve health and safety in mines as well as reduce lost blasts. Both quantitative and qualitative results have shown that buffer stores result in dramatic improvements in productivity and are readily acceptable by stakeholders. Keywords Buffer stores, lost blast.

Jan 1, 2011

By C. G. Anderson

"As demand for copper and precious metals continues to grow, the need to develop new supplies increases. In the imminent future, the new large global ore bodies are more complex, with enargite, tennantite and tetrahedrite as the abundant contained mineralogy. These resources also contain considerable gold and silver. As such, direct treatment by conventional smelting is prohibitive due to the potential environmental impacts and copper quality issues. This paper outlines the effective application and associated economics of industrially proven Alkaline Sulfide Leaching (ASL) hydrometallurgical technology to an enargite concentrate for selective removal and recovery of arsenic, antimony, gold and silver, leaving a clean high-grade copper concentrate. The fundamentals behind the technology are described, along with those of hydrometallurgical arsenic fixation and stabilization. Flowsheets and unit operations are elucidated, along with an in-depth economic analysis. INTRODUCTION Hydrometallurgical methods can be employed for treatment of gold-, arsenic-, antimony-, tin- and mercury-containing materials, concentrates and ores, as well as complex ones containing any number of metals (Conner & Anderson, 2013). The alkaline sulfide leaching (ASL) system is one of these. It is essentially a mixture of sodium sulfide and sodium hydroxide with other meta-stable alkaline species as required. This is a unique hydrometallurgical system beause it is a very selective lixiviant for the distinct leaching of tin, gold, antimony, arsenic, tellurium, silver and mercury (Anderson, 2000, 2001a, 2001b, 2002, 2003, 2012, 2014; Anderson & Twidwell, 2008a, 2008b, 2010; Anderson et al., 2004, 2005; Glazkov & Tseft, 1961; Gnatyshenko & Polyvyanni, 1961; Nadkarni et al., 1975; Nadkarni & Kusik, 1988; Polyvyanni, 1963). Worldwide, ASL technology has been employed industrially in the former CIS, China and the United States for the production of antimony (Anderson et al., 1992, 1994; Anderson & Krys, 1993; Holmes, 1944; Kaloc, 1967; Nordwick & Anderson, 1993; van Stein, 1971)."

Jan 1, 2015

By J. H. Cloete, S. M. Bradshaw, D. K. Chibwe

"Modern tundishes have evolved as vessels to serve as the final step in refining of molten steel by removing inclusions and promoting thermochemical homogeneity.In this study the flow behaviour in a four-strand tundish was investigated by means of a ½-scale water model as well as numerical modelling. The numerical and physical models were used to characterize residence time distribution and calculate properties pertaining to tundish flow regime. Three different tundish configurations were investigated: a bare tundish with no flow control devices, a tundish with a turbulence inhibitor, and a tundish with both a turbulence inhibitor and a dam.The physical and numerical models showed that a tundish without flow control devices is prone to significant short-circuiting. A tundish with a turbulence inhibitor was shown to be successful in preventing shortcircuiting and provided surface-directed flow that might assist the removal of inclusions from the melt. However, it was also observed that the upward-directed flow caused the maximum turbulence kinetic energy near the surface to increase dramatically. The potential for slag entrainment should therefore be considered during the design and operation of tundishes with turbulence inhibitors."

Jan 1, 2015

By G. S. Maré

Tin plating operations are of a complex nature due to the many operational variables that need to be controlled in order to create a product of required quality. The work in this report lays the basics for the control of a halogen plating operation based on the DuPont tinplating set-up with regard to the chemical make-up of the plating solution, as well as operational variables such as temperature and current density. To evaluate these aspects of the process, a rotating cathode Hull-cell set-up was used. This allowed for a laboratory scale plating arrangement that simulates industry closely with regard to chemical and hydro-dynamic considerations. Typical industry accepted standards were obtained for the values of operational variables and a ?baseline? test was conducted employing these standards. All subsequent tests conducted were benchmarked against this baseline result. A large suite of results was obtained in which it was found that changes could be made to the industry accepted norm which would improve on the stability of the operation and therefore the quality of the final tin-plated product. Examples of these results are: an increase in stannous tin concentration, an increase in sodium chloride concentration and a slightly elevated plating temperature. In addition, conditions were found that must be avoided to prevent instability and poor product quality.

Jan 1, 2010

By M. A. van Nierop

Load behaviour in an industrial mill has been measured directly by inserting probes through liner bolts. The data from conductivity probes have indicated the presence of premature centrifuging during manipulation of the load mass. Overloading conditions were also encountered. Overloading and premature centrifuging both reduce the power drawn by the mill. These effects have been successfully modelled.

Jan 1, 1997

By A. E. Lewis

Particle morphology is a term that is used to describe the overall external shape and appearance of particulate solids. From the physical point of view, a precipitated solid is characterized primarily by the size and morphology of the particles (Sohnel andGarside, 1992). If the morphology of the crystal structures is to be related to the processing conditions, then the morphologies need to be quantified in some way. This can be achieved by using surface area measurements as well as fractal dimensions. The key idea is that rugged and indeterminate systems can be described by using a fractional number that describes the ruggedness of the system (Kaye, 1989). In other words, when the complexity of a structure, such as an agglomerate, increases with increasing magnification, it is useful to employ fractal dimensions to describe the structure. Fractal geometry proposes that, instead of attempting to measure the length of an irregular boundary, the rate at which the length of the boundary approaches infinity with increasing resolution should be calculated. Cross-sectional profiles of rugged particles can thus be quantified using the fractal dimension, and a measurement of the ruggedness of the morphology obtained. One of the additional uses of measuring the fractal dimension is that the measured value can be related to the physical properties and formation characteristics of the particle (Kaye and Trottier,1995). The morphology of nickel crystals was quantified with fractal dimension calculations of particle cross-sections. Particle cross-sections were obtained by mounting the particles in resin and polishing back. These were then photographed using Scanning Electron Microscopy and the resulting profiles analysed using the structured walk technique.

Jan 1, 2001

By Q. C. Reynolds

Keywords: Pyrometallurgy, plant, photography, GIS, satellite images, Google Earth Google Earth is a piece of software able to display an interactive three-dimensional map of the world, combining aerial and satellite photography with maps, terrain, and user-generated geographical information systems (GIS). Many structural features of the planet, both natural and man-made, are of great interest to the mining and metallurgy field, and in this paper a study is made of the current state of the art of data accessible by Google Earth.

Jan 1, 2006

By P. den Hoed, R. I. Rambiyana

"Four sulphide minerals - pyrite (FeS2), pyrrhotite (Fe1-xS), pentlandite ([Ni,Fe]9S8), and chalcopyrite (CuFeS2) - contain the base metals and most of the iron in concentrates of platinum group metals (PGMs). In the pyrometallurgical processing of PGM concentrates these sulphides form a matte during smelting, and iron and sulphur are removed from the matte during the converting process. This paper discusses the roasting of Merensky concentrate in air before smelting, with the purpose of reducing the matte load to the converter.Roasting tests were conducted in a bench-scale rotary kiln at temperatures from 350°C to 700°C. The concentrate tested contained 17.4% sulphur and consisted of 23% pyrrhotite, 16% pentlandite, 11% chalcopyrite, and 2% pyrite. The particles were fine (d50 = 22 µm), and all the sulphide particles were liberated. Roasting in air at 550°C and 650°C for 20 minutes removed respectively 60% and 70% of the sulphur. The iron in the sulphides was oxidized to Fe3O4 (magnetite) at temperatures below 500°C and to Fe2O3 (haematite) at temperatures above 550°C. At 700°C the bed sintered and copper oxides formed. At temperatures below 450°C oxidation was incomplete: pyrrhotite remained and only 30% of the sulphur was removed. Smelting tests were conducted to assess matte fall and the deportment of copper and nickel to matte. It was evident that roasting resulted in lower matte falls (a drop of approximately 60%) compared with matte falls from unroasted concentrate. The iron and sulphur levels in the matte were reduced to below 3.5% and 22% respectively.This paper also briefly describes the mechanisms by which pyrrhotite, chalcopyrite, and pentlandite are oxidized during roasting. For chalcopyrite, the mechanism proceeds through an intermediate solid solution phase, which extends from Cu1.02Fe1.04S2 to Cu2.04Fe0.72S2 to a copper-rich solid solution of bornite (Cu4Fe1.4S4-Cu2S). The oxidation of pentlandite proceeds through a monosulphide solid solution (Ni0.39Fe0.53S-Ni0.74Fe0.15S) to a solid solution of heazlewoodite ([Ni,Fe]3}xS2). These mechanisms are explored in relation to chemical thermodynamics and microstructures."

Jan 1, 2015

By D. Vogt

South African underground hard rock mines are typically managed using measurements made daily, weekly or even monthly of key parameters such as face advance, readiness to blast, blast success, temperature or dust levels. Health, safety and productivity can all be greatly improved if a real-time measurement system can inform decision making. To enable this vision of widespread sensing, communication and decision support, CSIR has developed an open standard architecture for communication of sensor data, and a reference implementation using that standard. The standard, called AziSA, meaning ?to inform? in isiZulu, will allow any device that complies with it to join any network that supports it. The standard is designed for South African gold and platinum mines. To be practical in a typical Bushveld platinum mine, a real-time sensor system needs to be robust, reliable and cheap: ?Sensors are equipped with power sources that will last as long as the sensor is required. In effect, sensors need to be disposable: cheap enough not to warrant repair if they break. ?Communication in the stope is wireless, to avoid there liability problems associated with wire connections. For example, wires to sensors in the face area are unlikely to survive blasting. ?To get information out of the stope, the power line to the scraper winch is used as a communications link. Unlike a separate communications link, the power line will be repaired if damaged, because of its importance to production. ?Outside the stope, communications are transferred onto the mine communication infrastructure. To succeed as a management system, the next key element is the use of software decision support tools that will analyse masses of real-time data to extract key parameters and trends for decision makers. A range of sensors has been developed, including commercial sensors that have had wireless adapters added to make them AziSA compliant, and bespoke sensors that provide low cost sensing of typical mining parameters. An important parameter in any sensor network is the location of the sensor. This has to be easy and cheap to establish, so a tool has been developed to locate sensors in the confines of a stope, using ultrasonic and radio techniques. Once sensors are installed and located, they associate their location to all data that they produce. All the data from the system are captured at surface in a flexible database that can be queried by any application that requires data of any kind. It is simple to program alerts, and for actions to be associated with alerts. The use of wireless in stope also allows for communication from surface to the stope, or from stope to stope. The first implementation of an AziSA compliant system is being installed as part of the Mine Health and Safety Council funded rockfall elimination project. The design is discussed, and a future application for a platinum mine is considered.

Jan 1, 2009

Stope support systems, typically consisting of props and packs, are used extensively in the gold and platinum mining industry to stabilize the rock mass in the excavation vicinity and to reduce the hazard associated with rockfalls and rockbursts. The design of stope support systems was historically based predominantly on past experience and practices, and cost considerations. The recent development of a new and improved support design methodology, has led to the potential for significant increases in worker safety and support cost savings. This paper reviews some of the fundamental rock mass and support criteria that form the basis of the improved support design methodology. The considered design criteria are the height of potential fall; quasi-static stope closure rates; dynamic stope closure rates; compressive hangingwall stresses; discontinuity spacing, orientation and interface properties; effect of support length (stoping width); effect of compression rate; consistency of support performance; a real coverage; support spacing; and zone of support influence. The proposed support design methodology combines both the zone of influence and key block stability theories, resulting in optimized support systems for rockfall and rockburst conditions. The site-specific methodology consists of two stages: (i) a tributary area analysis, and (ii) a zone of support influence and a stability analysis, considering hangingwall failure due to buckling, shear and block rotation, which gives maximum safe spacing of individual support units. The methodology is suitable for designing support systems for both blocky hangingwalls and hangingwalls fragmented by face-parallel extension and shear fractures.

Jan 1, 2001

By J. D. Steenkamp

Keywords: Thermal, conductivity, diffusivity, expansion, history, density, specific heat capacity, industrial rich high-carbon manganese slag The thermal conductivity of slag is an important parameter in the design of furnace-containment systems based on freeze-lining technology. Literature indicates that the crystal content of a slag has a significant influence on its thermal conductivity. Industrial, rich, manganese-bearing slag was cooled at different rates to create samples with different microstructures. The coefficients of thermal conductivity of these samples were measured in a nitrogen atmosphere from room temperature to 990°C at 100°C intervals. The laser-flash measurement technique was used for this purpose. Follow-up investigations included XRF and XRD and modelling in FACTSage.

Jan 1, 2011

By S. M. Spottiswoode

Much as one hopes to predict whether damaging seismicity might occur somewhere in the next shift, this is not possible at present. Recently, an analysis of seismicity at two mines has shown that a small increase in seismicity occasionally occurs before both large and small events. This analysis is extended here to five mines, with the same results. Earthquake seismologists forecast hazard in terms of the average incidence of earthquakes over the last 50 years, adjusted on an hourly basis according to the possibility of aftershocks of events that have happened. The rate of seismicity in any area remains approximately constant when expressed as seismicity per area mined, or better still, per unit of elastic strain energy released. It is suggested that seismic hazard in mines be estimated using historical seismicity and forward modelling, adjusted according to the possibility of aftershocks. In summary, medium-term forecasting of seismicity is viable; short-term prediction of large events is not.

Jan 1, 2010

By P. Kluge

Mining engineers frequently encounter complex design problems for which the critical components of the design are difficult to quantify or compare. Teams of people typically work on these designs and human perceptions and judgments play a strong role. To assist with this process, the analytical hierarchical process (AHP) as a decisionmaking tool is described in this paper. Although the technique is used in many other disciplines, it is currently not widely used in mining engineering in South Africa. To use the AHP process, the problem should be treated as a hierarchy that defines the goal, the alternatives to reach it, and the criteria for evaluation of these alternatives. Pair wise comparisons are conducted on the criteria of the hierarchy to establish priorities. The value of the technique is that it is simple to test for consistency amongst the pair wise comparisons to ensure that the answer obtained is better than that provided by a random selection. To illustrate the technique, the use of a backfill support system in a platinum mining project was investigated. Ten design parameters, which will be impacted by the use of backfill, were identified and weighted according to their relative importance. The result of the AHP evaluation was that the use of a backfill support system should be preferred to a conventional support system at the mine.

Jan 1, 2011

By B. Solar Menéndez, M. B. Díaz Aguado, I. Á. Fernández, C. González Nicieza

The analysis of subsidence due to the opening of an underground void (mining, water exploitation or civil works hole) is a problem usually hard to solve. First of all, it requires a predictive model, in order to define both the displacement magnitude and area affected by subsidence. Such model should be validated with measurements of the actual movements sustained on the surface, in order to adjust it properly and enable influence of future behaviour in a reliable way. Two different kinds of problems might arise. On one side, it is necessary to control and measure surface movements in a very exhaustive way during a long period of time, beginning before underground works take place and finishing years after they are over. Furthermore, three factors bring in errors, some times of magnitudes higher than the displacement magnitudes measured. These include: the fact that reliable and long-term information cannot always be achieved; the precision of measuring devices; and the design of the topographical network itself. In addition, the predictive models more widely used only apply to certain excavation geometries, mainly to horizontal holes. In light of this background, the Group of Rock Engineering, of the University of Oviedo Mining Department, has developed a working methodology and a specific software tool, Subsidence 3D, to estimate ground displacements and strains. The program will allow for predictive models to be defined and also allows the treatment of data related with topographical marks and its comparative analysis with calculated results. The software has been programmed using Visual C++. Graphical outputs however are generated using AutoCAD 2000. This paper mainly refers to a practical situation, an underground coalmine, remarking the main difficulties arisen during the study of the available information and proposing how to solve them. A predictive model in subsidence 3D was established and validated. The actual behaviour of the ground was that in the model.

Jan 1, 2003

By T. Frömmer, H. Wagner

An inter-disciplinary geotechnical study has been carried out in an Austrian magnesite mine. The paper describes the how geological data, in situ and laboratory tests as well as subjective, empirical, geophysical and numerical methods have been used to identify critical areas in the mine. In einem österreichischen Magnesit Bergbau wurde in den letzten Jahren eine interdisziplinäre geotechnische Studie durchgeführt. Der Vortrag beschreibt den Einsatz subjektiver, empirischer, geophysikalischer und numerischer Methoden zur Identifikation geotechnischer Problembereiche Ces dernières années des études géotechniques interdisciplinaires sont effectuées dans une mine souterraine de magnésite en Autriche. Ce rapport trace l’application des méthodes subjectives, empiriques, géophysiques et numériques pour identifier les zones problématiques dans la mine

Jan 1, 2003

By A. Kale

A chlorination pilot plant having capacity to produce 5?10 kg/hr of titanium tetrachloride is in operation at the chlorination facility in Mintek. The bubbling fluid bed chlorination plant can be operated in batch and/or continuous process to study the chlorination kinetics of various feedstocks. The chlorination of titaniferrous ores to produce titanium tetrachloride (TiCl4) was carried out during the commissioning of the pilot plant and also as part of the titanium programme carried out at Mintek. TiCl4 is a basic raw material for producing commercial titanium dioxide pigment and titanium metal. This paper discusses the challenges faced during the commissioning and operation of the chlorination pilot plant. It also discusses the effect on the auxiliary facilities and instrumentation as a result of the harsh operating conditions of +1000°C and use of corrosive gases like chlorine and titanium tetrachloride. It discusses the effect of physico-chemical properties of the titanium tetrachloride and iron chlorides. The effect on the chlorinator refractory lining due to heating and cooling of the chlorinator is also discussed. Besides the special provisions made during the design of the chlorinator, this paper also discusses the operational experience and possible solutions to be implemented in future. Keywords Fluid bed chlorination, titanium ore chlorination, titanium tetrachloride (TiCl4) production using fluid bed technology.

Jan 1, 2011

By G. V. R. Landman

It is self-evident that economic pressure demands that today?s mines stay ahead and stay competitive. The challenge, however, isto find fresh approaches to the pursuit of efficiency and operational effectiveness. Rather than focusing on individual activities in isolation, a process that can lead to poor investment decisions affecting other critical areas of operation, a key concept is optimization of the whole value-adding process of mining. This concept is often called ?mine to mill?. Whereas it is never easy to establish optimal conditions across a whole mining operation, the quality and consistency of the blasted rock strongly affects all operations. In many instances an inability to control rock breaking has been unchallenged, leading to significant investment in time and money to manage the consequences of poor and/or inconsistent rock breaking. This paper discusses how electronic initiation systems can play a major role in optimizing the whole mining operation. Electronically programmed detonators provide not only the ability to tightly control a key parameter, namely timing, but also the opportunity to extract blast data for a continuous improvement process. The ability to alter predictably, using feedback from the downstream processes, blasting variables such as fragmentation, throw, wall stability, and vibration, is a huge advantage. The current understanding of the effect of timing, accuracy, and scatter on rock fragmentation is reviewed and offers reasons why there is significant progress in controlling blast results. Two case studies are examined, which demonstrate the benefits of the technology on the economics of the operations under review.

Jan 1, 2010

By L. Malmgren, A. Ansell

This paper deals with the influence from blast induced stress waves on the performance of shotcrete support in the Kiirunavaara mine. Time histories of stress waves from blasting were obtained from measurements during production blasts in the mine, followed by failure mapping. A finite element model, consisting of beam and spring elements, was used to calculate the shotcrete response to vibrations from blasting. The modelling approach was similar to that of a building during an earthquake, with accelerations measured in-situ used as loads. The analysis showed that the calculated adhesive stresses exceeded the strength in the interface between rock and shotcrete near to the blasted ring. It also indicated that tensile rock failure did occur. These types of failure will presumably result in ejection of joint defined rock blocks or rock slabs and will require a ductile support, such as fibre reinforced shotcrete. The predicted failure was confirmed by the mapping, which also showed that the zone of failed shotcrete was much larger in areas with plain shotcrete compared to areas with reinforced shotcrete. L’influence de l’onde de pression générée par les sautages à la mine de fer de Kiruna sur la performance du béton projeté est étudiée dans le présent article. Les ondes créées par les sautages ont été enregistrées et les domages résultants ont été cartographiés. La réponse du béton projeté aux vibrations de sautage est étudiée à l’aide d’un modèle d’éléments finis, constitué de poutres et de ressorts. L’approche est similaire à celle d’un immeuble subissant un tremblement de terre, avec les accélérations internes utilisées comme charges. L’analyse montre qu’à proximité des sautages, la contrainte adhésive dépasse la résistance de l’interface roche-béton. L’analyse confirme aussi l’existence de ruptures en tension. Ces types de rupture induisent probablement l’éjection des blocks définis par les structures du massif rocheux et requierent un support ductil, comme du béton projeté renforcé par exemple. Le type de rupture est confirmé par les observations de terrain, qui montrent aussi une extension plus importante des domages lorsque le béton projeté n’est pas renforcé. In diesem Konferenzbeitrag geht es um den Einfluss, der aus einer Sprengung hervorgerufenen Schwingungswellen auf die Ausführung der Spritzbetonverstärkung in dem Kiirunavaara Bergwerk. Die Aufzeichnungen der Schwingungswellen von Sprengungen gemäß einer Fehlerkartierung beziehen sich auf Messungen, die während der Sprengungen durchgeführt wurden. Ein Finite Elemente Modell, bestehend aus Stab- und Federelementen, wurde für die Berechnung der Spritzbetondeformation in Bezug auf die Schwingungen aus Sprengungen angewendet. Die Modellierungsmethode war ähnlich der eines Gebäudes während eines Erdbebens anhand der gemessenen Beschleunigungen vor Ort, die als Lasten benutzt wurden. Die Untersuchung hat gezeigt, dass die berechnete Haftspannung größer war als die Festigkeit in der Verbindung zwischen Gestein und Spritzbeton in der Nähe des Sprengungscentrums. Die Analyse hat gezeigt, dass die Zugfestigkeit des Gesteins versagte. Diese Arten von Versagen werden als Folge der Herausnahme von Gesteinsbrocken oder Gesteinsplatten erklärt und benötigen eine faserverstärkte Spritzbeton. Das vorausgesagte Versagen bestätigte sich beim Kartieren, welches auch zeigte, dass die Zone des versagenden Spritzbetons in Bereichen mit unverstärktem Spritzbeton viel größer war als in Bereichen mit armierten Spritzbeton.

Jan 1, 2003

By S. J. Lötter

Analysis of the major and minor components of raw zircon as well as plasma-dissociated zircon was undertaken using inductively coupled plasma optical emission spectroscopy (ICP-OES). Microwave-assisted acid extraction as well as flux fusion using lithium tetraborate were investigated as digestion methods. Microwave-assisted acid extraction samples were analysed with matrix-matched standards. The most successful microwave-assisted acid extractions yielded 44.3(1), 49.75(7), 78.3(3) and 90.0(7) per cent recovery for Zr, Hf, Al, and Fe respectively using sulphuric acid. In no instance was acid extraction capable of complete digestion of the sample matrix. A standard addition method was applied to the flux-fusion samples due to the high complexity of the sample matrix. Method validation for the flux fusion procedure was performed using the SARM 62 certified reference material (CRM) with acceptable recovery ranges being based on the 95 per cent confidence intervals of the CRM. Successful analyses were achieved for Zr, Hf, and Ti with apparent content of 66(6), 1.7(1) and 0.15(1) per cent respectively.

Jan 1, 2012