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If an orebody has been drilled to achieve some level of regulatory compliance, then a number of associated geological databases will exist, representing 10 000 to 100 000 m plus of core intervals. The databases usually contain data about assays, lithology, mineralisation and geophysical attributes. They will also include location information such as collar positions and downhole surveys. Obviously this data is collected by geologists for, predominantly, geologists and mining engineers. However, from a process design viewpoint process engineers usually ignore the geology where possible and rely on a small number of metallurgical test samples. Typically these test samples are sourced from convenient and available cores or from a small number of specially drilled metallurgical holes. One of the worst instances known to the author was the design of a SAG mill using only two SAG specific test results (one for each of the major ore types) while, geologically, the orebody was defined by more than 30 000 m of drilling. This paper sets out a philosophy to maximise the use of the geological data, both for process design and in preparation for the commissioning phase of projects. Geological data is used in the identification of preferred locations for metallurgical test samples, for checking the metallurgical validity of the geological ore-type definitions, where necessary developing new ore-type definitions (geometallurgical domains) and developing mathematical relationships for the estimation of important metallurgical factors across the geological database. If the estimation of factors (for example ore competence) is considered reliable enough then there is also the possibility of feeding calculated data back into the block modelling process to allow the generation of metallurgically relevant outputs in the mine plans.

Jan 1, 2007

By M. Kerr

Background- History The most significant change in mining since the late 1970?s has been the emergence of very large scale mining operations , which have been developed to ensure profitability with relatively low grade ores. These large tonnage operations have resulted in the development of larger unit sized machines in all operations of beneficiation, solid-liquid separation and dewatering. Often only a few flotation lines are installed and tonnages up to 25 ktpd and beyond are not uncommon. The increased throughputs have led to the development of circular, reactor type tank designs. The reactor cell system is the most up to date flotation cell design to utilise the principles of circular cell design. The Svedala DV mechanism was specially developed to suit the RCS machine giving good solids handling characteristics and excellent metallurgical performance. Development of UG2 ore type flotation equipment The equipment was developed and optimised by Svedala process from 1995. A higher energy specification was requested by industry. This amounted to 3kW/m3 for installed volume. Existing designs were at 1.5kW/m3. Hence various modifications were required to achieve the required power input. The first 50m3 machines were installed and developed at Impala Platinum?s UG2 circuit over a one year period. Once reliability and performance was achieved, over 300 large volume flotation cells were installed at Anglo Platinum and Lonmin operations as well. Pilot Plant Development The Impala Platinum High Energy pilot plant was commissioned in 2002 and had an installed power exceeding 5kW/m3. It was operated for over a year at the tailings dam booster station and was fundamental to the large scale scavenging plant design. All experience in overcoming mechanical and operational problems was applied in scale up design principles. A very robust mechanism was designed to accommodate the additional power input from installed motors, as well as the high SG (>1.5) of the feed source. The pilot plant flowsheet is shown in the figure below.

Jan 1, 2007

By Wayne Burmeister, Danie Benade, Louis Meyer, Hugo Joubert

What is not measured cannot be managed. This is true of most things, including a furnace lining. This paper describes a Lining Management System used for this purpose. It provides the operations staff with a management tool to predict long term lining life and acts as a process optimisation tool. It alarms and records upset furnace conditions. Outputs from the system are described as presented through a specially developed software package and interface. It includes vertical and horizontal furnace sections showing estimated isotherms through the lining as well as the furnace bath. It also shows calculated heat flux values, estimated lining wear and the freeze layer profile. A novel three-dimensional display is described which provides the operator with a big picture view of the furnace crucible profile under real time operating conditions. The powerful trending facility for analysing both measured and calculated values is discussed. The required instrumentation hardware as well as the installation thereof is described, with special reference to an electrically insulating thermocouple socket design. Finally feedback is provided on the first year?s performance of the system installed on an open ferrochrome furnace at Assmang Chrome, Machadodorp, South Africa.

Jan 1, 2007

By J. Riss, S. Gentier, A. Marache

The study of the hydromechanical behaviour of fractured rock masses requires a detailed knowledge of the isolated fractures. The aim of the paper is the simulation of the evolution of the void space, located between both walls of a fracture, during a shear test under constant normal stress. Results of the mechanical simulation model are first validated then analyzed in detail. We observe that, during the shear process, there is an opening of the fracture with the creation of preferential channels. These channels are determined at the early phase of the shear process (pre-peak phase), and we observe during the post-peak phase that void areas increase in size rather than the creation of new apertures. Die Untersuchung des hydromechanischen Verhaltens eines zerlegten Felsmassivs erfordert genaue Kenntnisse der einzelnen Spalten. Ziel dieses Artikels ist die Simulation der Evolution des Hohlraumes zwischen den beiden Wänden eines Spaltes während eines Abscherungsexperimentes unter konstantem senkrechtem Druck. Die Ergebnisse der Modellierung werden zunächst mit dem Abscherungsexperiment verglichen und dann im Einzelnen ausführlich analysiert. Während des Abscherungsprozesses tritt eine Öffnung des Spaltes auf, die die Bildung von bevorzugten Fliesswegen fördert. Diese Kanäle werden bereits in einer frühen Phase des Abscherungsprozesses (pre-peak Phase) festgelegt. In der post-peak Phase tritt dann eher eine Vergrößerung dieser Kanäle, als die Bildung neuer Hohlräume auf. L’étude du comportement hydromécanique d’un massif rocheux fracturé ne peut se faire sans une connaissance approfondie des fractures le constituant. L’étude présentée dans cet article concerne la simulation de l’évolution de l’espace des vides présent entre les deux épontes d’une fracture au cours d’un essai de cisaillement à contrainte normale constante. Les résultats du modèle sont tout d’abord validés puis analysés en détail. On constate que, au cours du cisaillement, il apparaît une ouverture de la fracture permettant la création de chenaux préférentiels. Ces derniers sont déterminés très tôt dans le cisaillement (phase pré-pic), et on observe dans la phase post-pic davantage un accroissement de la taille des chenaux plutôt que la formation de nouvelles zones de vides.

Jan 1, 2003

By P. F. Dicks, N. J. Shackleton, E. H. W. Theron, V. Malysiak

Flotation is a complex physical chemical process in which flotation reagents play a vital role in valuable minerals recovery and concentrate grades. This study examines the performance of new generation AECI Mining Chemicals (previously named Senmin) collectors. They were developed to enhance the valuable minerals recovery and flotation selectivity by tailoring the collectors to target specific valuable mineral species present in an ore and thus create added value for concentrators treating PGM ores. The case study was conducted on a Platreef ore, where batch flotation tests were performed and the concentrates were mineralogically characterised for PGE and BMS using QEMSCAN. Further batch flotation testwork was conducted on Merensky and UG2 ores from various localities in South Africa to confirm the trends observed for Platreef ore. The results have shown that there is a strong correlation between PGE mineral type and AECI Mining Chemicals collector type - clearly demonstrating that one reagent type does not fit all flotation applications. Keywords: Batch flotation, QEMSCAN, collectors, PGE and BMS

Jan 1, 2020

"Chairman: Mr. K. F. LaneRapporteur: Mr C. T. ShawPapers:Design of crushing plant flow sheets by simulation by T. GurunThe impact of transportation networks upon the potential supply of base and precious metals from Sonora, Mexico by P. de V. Harris and D. E. EurestyProfitability sensitivity analysis of a mining venture by C. A. Beasley and E. P. PfleiderTechnological innovation and its potential effect on the opening of new gold mines in South Africa by N. C. JoughinMr Turgay Gurun, in presenting his paper, indicated that this simulator was no purely theoretical exercise, but that the model had been used in the design of crushing plants of capacities ranging from 3 000 tons per day to 66 000 tons per day, and that recently the design of a plant of capacity of 99 000 tons per day had been studied.The crushing plant simulator was an independent portion of a much more comprehensive simulator for the design of a. complete recovery plant. It would be possible to use each section of this simulator on its own, and simulators would be designed to cover flotation concentrates, cash flow analyses of the entire project, and so on.Each simulator would be backed by a comprehensive data bank. For example, the crushing plant simulator was backed by such a data bank which included the performance and cost data from five manufacturers for an average of 30 items of process and materials handling equipment each. This meant that data preparation involved generally less work than would be required for a manual calculation. On average, data preparation for one run took 30 minutes and three minutes of computer time on an IBM 360/40 completed the run. The model could be valuable as a design tool in that it allowed the designers an opportunity to make a thorough examination of many alternative designs. It was also of value to plant operators as it could be used to predict the consequences of operating decisions.This paper generated much interest and there were numerous questions and contributions, so many, in fact, that the discussion had to be cut short.It was pointed out by Mr K. F. Lane that crushing plants represented a very large capital investment. A plant designed for 40 000 tons per day at 98 per cent efficiency might well in practice be run at 50 000 tons per day at, say, 83 per cent efficiency. He asked how, therefore, their design could be investigated without building economic criteria into the model? The author conceded that this was a tender point. He would have liked to have given facilities for more variability of the metallurgical information. He pointed out, however, that while there was no overdesign for conservatism built into his system, some overdesign was inevitable as the performance characteristics given by the manufacturers were generally conservative. Also, in his system, if lower recovery was allowed for, the system would nut through more tonnage."

Jan 1, 2014

By B. Amadei, F. Tonon

Rock stress measurement is cast in the more general context of the determination of boundary conditions for rock engineering. A study on the effect of elastic anisotropy on underground excavations reveals that this effect is actually controlled by the imposed boundary conditions. Applications to tunneling and to the Underground Research Laboratory (URL), Canada, exemplify a procedure for boundary condition estimation formerly developed by the authors. The procedure displayed fast convergence despite the complex geometry, and the high degree of non-linearity of the models. In the URL application, the 3-D model was able to completely reproduce the complex measured stress pattern, and the 90° rotation of the principal in situ stresses with depth. In order to reliably estimate the boundary conditions reproducing the current in situ state of stress, response measurements of the rock mass to current disturbances are necessary as input data. La mesure des contraintes in situ tombe dans le domaine général de la détermination des conditions aux limites pour les problèmes de mécanique des roches. Une étude sur le rôle de l’anisotropie élastique sur les excavations souterraines montre que ce rôle est contrôlé par les conditions aux limites qui sont imposées. L’application aux tunnels et au Laboratoire Souterrain de Recherche (URL) au Canada, nous permet de présenter une méthode de détermination des conditions aux limites. La méthode converge rapidement bien que le géométrie soit complexe et que le problème soit non-linéaire. Pour le URL, le modèle 3D est capable de reproduire la distribution des contraintes qui ont été mesurées ainsi que la rotation de 90 degrés des contraintes in situ avec la profondeur. Afin de déterminer avec précision les conditions aux limites responsables pour la distribution actuelle des contraintes, la réponse du massif rocheux doit être connue et mesurée. In der Felsentechnik sind die Spannungsmessungen in Gestein an die Bestimmung der Randbedingungen gebunden. Eine Studie legt dar, dass der Effekt elastischer Anisotropie in unterirdischen Aushoehlungen von den Randbedingungen kontrolliert ist. Eine von den Authoren entwickelte Methode zur Bestimmung der Randbedingungen wird an Beispielen im Tunnelbau und im Underground Research Laboratory (URL) in Kanada illustriert. Auch bei komplexer Geometrie und einem hohen Grad an Nicht-Linearitaet zeigt diese Methode ein schnelles Konvergenzverhalten. Ein 3D-Model und dessen 90° Drehung der lokalen Hauptspannungen mit der Tiefe, kann bei einer URL Anwendung vollstaendig reproduziert werden. Um mit dieser Methode die Randbedingungen zuverlaessig abschaetzen zu koennen, werden der gegenwaertige lokale Spannungszustand sowie die Antwort des Gesteins und die resultierenden Stoerungen als Eingabedaten benoetigt.

Jan 1, 2003

By J. Güntner

Most copper/cobalt ores from the Central African Copperbelt contain sulphidic compounds, which are not extractable in direct leaching. Roasting provides the possibility to transfer the valuable components into leachable compounds. In an operation window defined by temperature and off-gas composition it is possible to selectively oxidize iron sulphides to haematite and copper/cobalt sulphides to sulphates. Selective sulphating of the valuable minerals is an important condition for the subsequent leaching stage. The dissolved copper and cobalt are recovered by solvent extraction and electrowinning. This technology has been part of an established process for many decades. The concentrates from recent projects on the Copperbelt have lower sulphur contents, and frequently higher copper contents, than those from older projects. The paper shows the consequences of this trend for plant operation and explains useful counter actions by means of case studies. Autothermal combustion is ensured even at very low sulphur contents. Off-gas treatment has so far been based on SO2 removal through sulphuric acid production. The generated acid is used to make up acid losses in the hydrometallurgical plant section. This well-proven process combination is still the preferred route if the feed sulphur content is high enough; however, some cases may require different off-gas cleaning concepts without compromising on clean air quality. Roasting in a fluid-bed furnace remains the core of the technology. Fluid-bed roasters are easy to operate and provide an excellent control of the calcine quality. Different feeding and heat-recovery systems are used to provide a tailor-made solution for each project. Outotec built it first sulphatizing roaster in Zambia about 30 years ago. At that time, the roasting of metal sulphides was already one of the main technologies in the company. Outotec has developed roasting solutions for copper, gold, zinc, lead, molybdenum, and pyrite ores. The continuously expanded and upgraded research facilities provide an excellent basis for developing sustainable, energy-efficient, and economic solutions for copper and cobalt production in Africa.

Jan 1, 2012

By J. Güntner

Most copper/cobalt ores from the Central African Copperbelt contain sulphidic compounds, which are not extractable in direct leaching. Roasting provides the possibility to transfer the valuable components into leachable compounds. In an operation window defined by temperature and off-gas composition it is possible to selectively oxidize iron sulphides to haematite and copper/cobalt sulphides to sulphates. Selective sulphating of the valuable minerals is an important condition for the subsequent leaching stage. The dissolved copper and cobalt are recovered by solvent extraction and electrowinning. This technology has been part of an established process for many decades. The concentrates from recent projects on the Copperbelt have lower sulphur contents, and frequently higher copper contents, than those from older projects. The paper shows the consequences of this trend for plant operation and explains useful counter actions by means of case studies. Autothermal combustion is ensured even at very low sulphur contents. Off-gas treatment has so far been based on SO2 removal through sulphuric acid production. The generated acid is used to make up acid losses in the hydrometallurgical plant section. This well-proven process combination is still the preferred route if the feed sulphur content is high enough; however, some cases may require different off-gas cleaning concepts without compromising on clean air quality. Roasting in a fluid-bed furnace remains the core of the technology. Fluid-bed roasters are easy to operate and provide an excellent control of the calcine quality. Different feeding and heat-recovery systems are used to provide a tailor-made solution for each project. Outotec built it first sulphatizing roaster in Zambia about 30 years ago. At that time, the roasting of metal sulphides was already one of the main technologies in the company. Outotec has developed roasting solutions for copper, gold, zinc, lead, molybdenum, and pyrite ores. The continuously expanded and upgraded research facilities provide an excellent basis for developing sustainable, energy-efficient, and economic solutions for copper and cobalt production in Africa.

Jan 1, 2012

By H. C. Van Der Merwe

In the 21st century, dynamic, accurate digital 3-D geological models are essential to the pursuit of safe, efficient and profitable mining. This is particularly true for the deep-level underground mines in South Africa. The Sirovision® solution is a collaboration project between the Australian CSIRO (Commonwealth Scientific and Industrial Research Organisation), Datamine Software Ltd. and AngloGold Ashanti Ltd (AGA). The purpose of the project is to provide a fully integrated digital rock face imaging, geological mapping and modelling system for the AGA gold mining operations. The CSIRO-developed Sirovision® Stereo Camera Rig (SCR) consists of two digital cameras, alighting system, a laser guidance system and image processing software. The imaging system works on the principles of photogrammetry, i.e. overlaying of two 2-D images with a central focus point, with mathematical algorithms extracting 3-D information from the 2-D image pair. The output from matching several image pairs is a computer-generated, full 3-D, virtual copy of the mining excavation. The image resolution and relief ares of sufficient quality to distinguish different rock types and structural contacts. Functionality within Datamine Studio3 is used to add geological intelligence to the 3-D images provided by Sirovision®. The geologist identifies and ?draws? lines representing geological features directly onto the image. By utilizing the inherent ?topography? of the 3-D image, the software is able to convert the lines into 3-D surfaces, ready for use in the 3-D geological model. Subsequent to promising underground test results from AGA?s Sunrise Dam Gold Mine (SDGM) in Australia and other mining operations worldwide, it was decided to test the Sirovision® system in the South African deep-level gold mines. The first underground tests at Moab Khotsong Mine began in January 2009. The objectives of these tests entailed the capturing of 3-D images of selected development ends, mapping of geological features onto the 3-D images and integration of the mapping data with the 3-D geological model. Some downsides have cropped up during the feasibility testing, related to practicality of the SCR for acquisition of 3-Dimagery in the deep-level underground operating environment. These constraints will have to be addressed prior to operational implementation. Facing such difficulties is not unusual when attempting to implement new technology in such a challenging working environment and testwork is still in progress at the mine in order to prove the concept of using this technology in a Witwatersrand underground gold mine. The great advantage of the Sirovision® solution is that it offers the geologist the opportunity to work remotely on a 3-D virtual copy of a mining excavation, without the heat, humidity, hazards and time constraints associated with physical mapping in an underground workplace.

Jan 1, 2009

By L. A. Thompson, A. J. Linington

"Copper–cobalt extraction is a reagent-intensive process resulting in acid consumption greatly contributing towards production costs, which in the current market conditions curtail profitability. Nanofiltration (NF) membranes have become an attractive approach in the mining and minerals industry for product concentration and reagent recovery based on the ability of the membrane to separate monovalent ions from divalent ions. NF membranes can selectively separate acids from metals and salts allowing acid to be recycled as well as the concentration and purification of product streams. Membrane technology in the field of copper–cobalt processing focusses on the concentration of Cu2+ and Co2+ in the pregnant leach solution, recovery of acid from waste streams to neutralization, recovery of valuable metals from waste ponds and process water recovery. This paper aims to provide insight into the potential applications of NF membranes in copper–cobalt processing circuits as well as a brief overview of the effects of process conditions on membrane performance and process development. INTRODUCTION The copper–cobalt industry commonly uses inorganic acids, such as sulfuric acid, in large quantities for primary leaching of copper–cobalt oxide ores and releaching during product purification (Stuurman et al., 2014). This results in numerous acidic intermediate streams containing high metal concentrations and acidic waste streams with low metal concentrations. Acid consumption typically accounts for 10–15% of the operating costs of mines in the Democratic Republic of Congo (DRC) and Zambia (Acid Plant Database, 2015). Due to remote mine locations, poorly maintained roads and cross-border conflict, the cost of sulphuric acid can range between USD 300 and 400 per ton. The pivotal role of acid in the copper–cobalt extraction process has driven many mines to build sulphuric acid plants on site to ensure a reliable acid supply, however elemental sulphur still needs to be imported which faces similar logistical challenges and contributes towards operating costs."

Jan 1, 2015

By K. Shame, H. H. Thiele

South Africa holds approximately 70% of the world’s total chrome reserves. Chromium is an important raw material for the production of stainless steel and ferrochrome alloys. Over the years, China’s ferrochrome market has been dependent on chrome ore imports from South Africa. In 2018, China imported about 75% of its chrome ore from South Africa. With the low platinum price and the rising demand for stainless steel, a growing demand to evaluate new beneficiation technologies for fine chromite was identified. Gravity separation of fine chromite (<75 μm) is inefficient, due to the limitations of the technology to upgrade fine particle size distributions. Potential for the recovery of chromite, specifically fines (<75μm), lost to UG2 PGM flotation tails, but also from MG and LG6 spiral circuit tailings exist. Flotation of podiform chromite ores from India and Kazhkhstan is successful in generating saleable product grade, following acid or alkaline flotation routes. Application to South African stratiform chromite is being evaluated, with the emphasis on evaluating reagent type, optimising dosages and the effect of pH in optimising flotation performance. Flotation can unlock additional value from chromite tailings material. The effect of ore characteristics such as gangue mineralogy, particle size distribution and headgrade are reported. The performance in terms of product quality and yield are evaluated and compared. The impact of this paper will not only prolong life of mine and increase revenue but will also alleviate environmental burdens associated with tailings dams. Keywords: Chromite, flotation, fine material, performance optimisation

Jan 1, 2020

By F. Peer

In most coal preparation processes, water is a necessary medium, but the presence of water in coal after it has been cleaned has a negative impact on transportation costs, handling and specific energy values. The utilization of super absorbent polymers (SAP) in the nappy application is well known. The concept of utilizing these polymers was investigated for the purposes of dewatering coal and other fines, generated by preparation processes such as flotation. SAPs are granular highly cross-linked synthetic copolymers with excellent water-absorbing properties. The dewatering process is characterized by three main stages: (a) contact of super absorbent polymer with high-moisture fine coal; (b) separation of dewatered fine coal from super absorbent polymer; and (c) regeneration of used super absorbent polymer, by exploiting its response to changes in conditions such as pH or temperature. Preliminary tests showed the separation step to be very difficult. The novel idea of encasing a given amount of polymer in a water permeable cloth solved this problem (of separating the swollen polymer from the dewatered coal). Preliminary tests investigating the effectiveness of the sachets of polymer showed a drastic decrease in the moisture contents of slurries. Furthermore, it was shown that it was possible to regenerate the polymer (still within the sachets) through thermal drying. A full-scale experimental programme was then followed to accurately determine the feasibility of using sachets of SAP. The experimental variables were initial slurry moisture content and polymer dosage. It was observed that the sachets seemed to work fastest and most effectively at high moistures and also at higher dosages of SAP. Regeneration of the polymer was also investigated, using two methods: thermal regeneration and pH-induced regeneration. The experimental variables, for investigating the regeneration process, were method of regeneration and grade of water used. Thermal regeneration at 70°C seemed to work successfully. Although the cost of using thermal energy is still a problem, the safety aspect (fire hazards) has been addressed since the polymer does not ignite when heated, unlike fine coal particles that may do so. The alternative method of regeneration, which exploits the pH-sensitivity of the polymer, was less successful, and further work needs to be conducted.

Jan 1, 2003

By M. Görnerup, M. Hayashi, S. Seetharaman, C. -Å Däcker

The mould flux plays a crucial role in the continuous casting operation of steel due to its multi-functional assignment as lubricator and heat flux controller. In reality, the commercial fluxes can fall short of the expectations of the operator. In such cases, the performance of the mould flux reduces production throughput in the casting machine. This paper presents the results of a study of two different commercial mould fluxes in continuous casting of steels. The results of online sampling during casting, as well as off-line measurements in the laboratory, are presented. Mould flux powder and slag samples from the caster have been characterized with respect to melting behaviour, interfacial tension and thermal diffusivity, using various measuring techniques. An experimental technique has been developed in order to simulate the melting behaviour of a flux in the mould, which has been found to be useful for qualitative studies. A cross-sectional view of different powders reveals that up to four different material layers may exist in the bed: a loosely packed powder layer, sintered layer, semi-solid layer and liquid slag layer. It is found that the melting rate of the mould flux is dependent on the liquid slag layer thickness. Thus, in a continuous casting operation the melting rate is likely to be non-uniform with position in mould due to the difference in liquid slag layer thickness. Mould slag composition is found to be influenced by the starting powder for as long as 30 min, representing a large part of the first heat casting time. Observations of gas formation indicate that interfacial reactions between the steel and slag take place. Keywords: continuous sacting, mould flux, mould slag, properties

Jan 1, 2004

By D. E. Ng?andu

The experience of Mufulira concentrator, of the Zambia Consolidated Copper Mines Limited, with underground mine drainage water, which is used in milling operations is discussed. It is shown that the underground mine water has a deleterious effect on flotation performance. The adverse effect of the underground water was successfully negated by adding lime into the primary ball mills and increasing the pH of the slurry, from a ?natural? pH of 8 to the flotation pH of 10.5. Traditionally, the pH modifier, quicklime, had been added downstream of the milling. Changing the lime addition point further reduced lime consumption by 50%,?a key issue as lime accounted for over 60% of the Mufulira flotation reagent costs. The nature of the effect of the underground water at Mufulira, particularly the sensitivity of the flotation to the pH at which the milling was conducted, characterized galvanic interaction. A large-scale plant situation is presented in which the desired electro-chemical response in the flotation was achieved, by a deliberate manipulation of the milling environment. The experience provides practical testimony of a more fundamental role for the milling process, other than the mere physical preparation, i.e. size reduction and liberation, of mineral particles prior to flotation.

Jan 1, 2001

By Q. Lui, J. Oxenford

The occurrence of heavy minerals in the oil sands of Alberta has long been known and has been well documented in the literature. Unfortunately most of the researchers working on this resource have been unable to produce products that meet acceptable market specifications. This has resulted in many misconceptions about this resource. Recent efforts have shown that with some innovative approaches, marketable material can be produced and as a result it might finally be possible to realize the potential of this immense resource that, some have estimated, could contain in excess of 20% of the world demand by 2010. This paper highlights the uniqueness of this mineral assemblage and the mineral processing challenges it presents. It shows the most recent work that has resulted in the production of marketable titanium and zircon products. This paper also focuses on some of the special problems resulting from the variability in the heavy mineral suite. Of special interest is the occurrence and removal of bitumen and pyrite without adding to the sulphur dioxide loading in the regional airshed. The trend by the mining industry to develop various positions on ‘sustainable mining’ has some significance for the heavy mineral industry. Although the industry generally has an excellent track record of eventually rehabilitating disturbed ground in an acceptable manner, heavy mineral mining operations tend to have a relatively large footprint of disturbance and the industry is under considerable pressure to develop options that are more environmentally acceptable. In addition, as operators move to exploit deposits that are lower grade and/or are further from a port site, the emissions per unit of sold product will also rise and the industry will be under pressure to address this issue as well. Because heavy minerals from oil sands are by-products of existing operations, there are virtually no incremental disturbances or emissions that would be associated with heavy mineral production. All mining and tailings remediation issues are accounted for by the oil sand operation. The only incremental emissions would be those associated with the mineral processing operations and transport of finished products to a port site. This paper discusses the environmental and cost implications of this situation.

Jan 1, 2003

By I. Alp

Application of magnetic separation was investigated for the enrichment of colemanite ores by removing the magnetic gangue fraction. The detailed XRD analysis of the ore has indicated that the gangue fraction is composed predominantly of the iron-bearing silicates such as smectite and, to a lesser extent, illite. Magnetic susceptibility measurements of the colemanite and gangue samples have proved that colemanite is diamagnetic in character whereas gangue fraction is weakly paramagnetic to allow the removal of this fraction by magnetic separation. Magnetic separation of the crushed and sized ore samples (-5 mm +75 µm) was performed using a high intensity permanent magnetic separator. Under the test conditions a colemanite concentrate (41.29 wt.% B2O3) was found to be produced from the crushed ore (30.76 wt.% B2O3) at a recovery of 96.76%. These findings suggest that magnetic separation has great potential as an alternative process for the production of a concentrate of commercially sufficient grade.

Jan 1, 2009

By T. G. Carter

Support system design for tunnels and underground excavations has for many years relied heavily on the use of rock mass classification systems and the Hoek-Brown failure criterion as a means for characterizing rock mass behaviour. Because of their development, both the GSI system and the Hoek-Brown criterion admirably characterize most ?normal? rockmasses from the viewpoint of their behaviour for rock excavations. They, however, run into difficulties when applied at the two ends of the rock competence scale. This is largely because block size and incipient strength are such that rockmass behaviour in these domains tends not to be controlled by interblock shear strength but rather by material strength. At the low end of the rock competence scale (UCSi <<15 MPa and GSI generally <30) discontinuities play less of a role and rock mass strength tends to matrix strength. Similarly, at the high end of the scale (GSI >>65, mi>>15), because discontinuities are now widely spaced, block size becomes so significant that again, intact material behaviour rather than the fracturing becomes the dominant factor controlling rock mass strength. In this paper several case examples are presented to illustrate the application of the high-end (spalling) and low-end (weak ground) transition Hoek-Brown relationships proposed by Carter, Diederichs and Carvalho (2007) as a basis for better defining rockmass behaviour at the extreme ends of the rock competence scale.

Jan 1, 2008

By A. Asadi

Subsidence phenomenon as an unwanted consequence of underground mining can cause problems for environment and surface structures in mine area. Surface subsidence prediction for inclined and steep seams has been given less attention than horizontal seams due to the difficulties involved in the extraction of such coal-seams. This paper introduces a new profile function method for prediction of surface subsidence due to inclined coal-seam mining. The results of calculation with the new function indicate that the predicted value has good agreement with the measured data. Keywords: subsidence; coalmining; caving mining methods; longwall mining; profile function.

Jan 1, 2005

By B. Salt, R. Sullivan, E. Roos, M. de Vries, K. McKenna, L. R. Nelson, M. J. N. Uys, P. Jacobs, E. Munnik, P. Lewarne

A review is presented of the furnace cooling system design and operating developments since the initial furnace start up in January 2001 of the Chambishi DC-arc furnace to produce ferrocobalt alloy. The furnace operating conditions present a number of challenges to the furnace designers and operators in particular to provide a sustainable lining that can withstand the highly corrosive siliceous slag (roughly 50% SiO2). This is exacerbated by the dual requirement to operate this slag in a relatively highly superheated state (?T ? 400°C when tapped at 1550°C) to ensure that the ferroalloy can be tapped (estimated 1370°C alloy liquidus temperature) prior to atomisation. The core design challenge occurs at the alloy-slag interface, where a single refractory type cannot simultaneously meet the dual requirement of both adequate alloy and slag corrosion compatibility. Progression by the fourth furnace campaign to involve a retrofit of the bath sidewall to Hatch high-intensity, water-cooled, copper Waffle coolers and tapblocks is described. This involves operation of the entire slag bath, the slag-alloy interface and a portion of the alloy within a more chemically compatible refractory/slag (and possibly at times even an alloy) freeze-lining. Due to the high furnace power density employed (up to 500 kW/m2 hearth area) coupled with the large slag superheat needed, the resulting imposed peak bath sidewall heat fluxes are substantial, especially in the alloy (typically averaging 170 kW/m2), and on occasion have exceeded 1000 kW/m2. The performance of the Hatch Copper Waffle coolers under such aggressive process pyrometallurgical conditions is described. Aspects of the design and especially operating strategies to effect sustained production at up to 38 MW power input are also discussed.

Jan 1, 2004