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By K. C. Sole, M. E. Mitshiabo

Although surfactants have proven to increase metal extraction by improving solution flow in porous media, these reagents have not been widely adopted in heap leaching operations because of potential incompatibilities with downstream processes that are subject to surface properties. The BASF leaching aid, LixTRA 118, was previously found to have no significant effect on post-leach operations. This study evaluated its performance in ores of different particle size distributions and the impact on acid consumption and metal recovery. Column leach studies, carried out on a copper oxide ore and mixed oxide–sulfide ore, showed that the effect of LixTRA 118 was more pronounced in ores with wider particle size distributions than in those with more uniformly sized particles. Solution percolation rates increased by up to 18% in the presence of leaching aid, and increased copper recovery and acid consumption. Improved wetting facilitated the kinetics of acid diffusion at macroand micropore level. There was no significant effect on iron recovery

Jan 1, 2023

By A. Singh, R. D. Govender

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

Jan 1, 2020

By N. Kumar, A. K. Dhawan, A. Varughese, S. K. Khullar

Abstract The in-situ stress field is one of the primary parameters influencing the performance of underground structures particularly in the Himalayas where there is strong influence of topography and geology on in-situ stresses. It is always advisable to measure the in-situ stresses, in whatever best way possible. Hydrofracturing is one of the methods by which in-situ stress can be measured. This paper briefly describes details of the concept of Hydrofracturing in arriving at the in-situ stresses of the rock mass at Pancheswar Project. The data obtained from the tests has been analysed, interpreted and the results are presented in this paper. Kurzfassung Das Spannungsfeld an Ort und Stelle ist einer der wichtigsten Parameter, die das Verhalten der Untergrund-Struktur beeinflussen, insbesondere in den Himalayas, wo die Topografie und die Geologie einen grossen Einfluss auf die oertlichen Spannungen ausueben. Es empfiehlt sich stets die Spannungen an Ort und Stelle so gut wie moeglich zu erfassen. Die Hydrofraktur bzw hydrografisches Zerstueckeln ist eine der Methoden, die bei den Messungen der oertlichen Spannungen verwendet werden koennen. Diese Abhandlung beschreibt kurz Einzelheiten ueber das Konzept von Hydrofraktur bei der Bestimmung der Spannungen an Ort und Stelle von der Felsmasse bezueglich des Projekts Pancheshwar. Die gewonnenen Daten aus den Messungen wurden analysieret und ausgewertet. Die Ergebnisse werden dabei vorgelegt. Sommaire Le champ de contraintes in-situ est un des paramèters principaux influencant l’exécution des structures souterraines particulierèment en Himalaya où les forces in-situ sont fortement influencées par les caractéristiques topographiques et géologiques de la région. La fracturation hydraulique est une technique qui permet de mesurer des forces in-situ des massifs rocheux. Cet article décrit brièvement le mécanisme de fracturation hydraulique et présente les résultats de mesure des forces in-situ des roches au site du projet hydroélectrique de Pancheswar.

Jan 1, 2003

By R Kroukamp

Horizontal belt filters are typically used for separation of relatively free filtering solids where good post treatment is required. He horizontal belt filter is a continuous filter with an endless cloth supported on a grooved carrier belt. The belt and cloth are driven around two rollers across a series of evacuated suction boxes. The feed suspension is introduced at one end of the filter and deliquored to produce a cake at the other end. The benefits of using horizontal belt filters are good cake washing, continuous and visible processing, fully automatic operation, flexibility, high capacity and relative high speeds of operation. If required, horizontal belt filters enable efficient counter-current washings to minimize the usage of wash liquid. The horizontal belt filter has applications in the following: [? Metal concentrates ? Mineral sands ? Tailings ? Coal ? Iron ore ? Alumina ? Chloride processing ? Nickel and Cobalt refining ? Platinum group metals ? Zinc processing ? Many other applications in the Mining and Metallurgy industries ] 2. Operating Principle of a Horizontal Vacuum Belt Filter 2.1 Cake Forming The slurry to be dewatered is evenly distributed onto the filtering surface. Gravity assists the cake formation and the feed can be introduced in multiple stages. 2.2 Cake Washing Once the cake is formed, wash liquor/water can be introduced onto the top of the cake via a wash launder or sprays. Multiple wash stages, co-current, counter-current or direct washing can be added by increasing the length of the filter.

Jan 1, 2007

With the passing of Dr William Bleloch on 20th June 1991, we lost not only a colleague and a good friend but a man who made a very significant contribution to the industrial development of South Africa. He can rightly be called the father of the ekctrochemical and electro-metallurgical industries in this country, since his ideas and dedicated work were directly responsible for the development of these large industries as we know them today.

Jan 1, 1991

By R. W. Ottermann, N. D. L. Burger, A. J. von Wielligh, P. R. de Wet, J. L. Steyn

A low noise blast hole drilling system was developed to limit the risk of noise induced hearing impairment in mining operations. Noise induced hearing loss has been identified as a major occupational health risk in SA mines. The noise generated by pneumatic percussion drills is a major contributor to such noise induced hearing. This motivated the South African Safety in Mines Research Advisory Committee (SIMRAC) to commission the development of a low noise rock drill system. The system had to be designed, manufactured, tested and demonstrated in a simulated underground mining environment. The specification required noise levels below 90 dBA. Other important design considerations were ease of manual transport, setting up and operation. The primary design concept was to encapsulate a standard Seco S215 pneumatic rock drill in a composite material tube. The tube is pushed onto the rock face by a pneumatic cylinder and is sealed at the rock face by an elastic seal. The drill is pulled towards the rock face by a rope and pulley mechanism fitted inside the tube. This mechanism is powered by a second pneumatic cylinder. The actions of moving and setting the drill require two persons. However, the team can carry out the drilling function itself on several drills simultaneously because of the self-thrusting design. The drill is supported by two camlocks. The exhaust (air containing dust, water, rock shavings, oil and grease) is removed from the encapsulating tubes via exhaust tube to the end of the stope. In this way exhaust noise and air pollutants are disposed of away from personnel. Tests were conducted in a test stope. Noise levels of under 90 dBA were achieved, thereby attaining the primary design specification. This was achieved without materially compromising ease of handling. Penetration rate was somewhat improved compared to that of the standard drill, so that productivity could be maintained. Keywords: Drill, rock drill, quiet, noise, mine, underground.

Jan 1, 2003

By M. Jeffrey

This study investigated the elution of precious and toxic metals from activated carbon. Gold and mercury are of primary interest, due to their value and environmental impact respectively. A laboratory elution rig was commissioned to simulate industrial Zadra and AARL carbon elution conditions. Mercury was found to elute most effectively in strong caustic cyanide solutions; gold was found to elute most effectively in hot low ionic strength solutions. As cyanide decomposes on contact with activated carbon at high temperatures, optimum elution conditions for gold conflicts with those for mercury?no practical compromise in conditions was found. However, sequential elution allowed reasonable recovery of both metals. Ongoing work is looking at the deportment of other metals under elution conditions.

Jan 1, 2009

By K. Sugawara, H. -S. Jeong, Y. Ishiguro, J. Otani, Y. Obara, A. Hirata

A series of measurements of induced stress by the Compact Conical-ended Borehole Overcoring (CCBO) technique was performed within rock mass around a tunnel excavated in a region that an underground powerhouse is constructed under high initial rock stress. In the measurements, a phenomenon of core disking was observed during overcoring. The selecting method of strain data uninfluenced by the core disking was proposed, using X-ray CT scanner. Then, the state of induced stress determined from the selected strain data was discussed, comparing with the state of initial stress. Eine Serie von Messungen von induzierter Belastung mit kompaktem konisch-beendetem Überbohrverfahren (CCBO) wurde in Felsmassen um einen Tunnel ausgeführt, der in einer Region gebohrt wurde wo ein unterirdisches Kraftwert unter hoher anfänglicher Felsbelastung gebaut wird. Bei den Messungen wurde beim Überbohrverfahren ein Phänomen des Core Disking beobachtet. Die gewählte Methode der Belastungsdaten, unbeeinflusst durch Core Disking wurde vorgeschlagen, unter Verwendung von Röntgen-CT-Scanner. Dann wurde der Zustand der induzierten Belastung aus den gewählten Belastungsdaten diskutiert, unter Vergleich mit der ursprünglichen Belastung. Une série de mesures de contrainte induite effectuée avec la technique de forage de sur-carottage compacte à embout conique a été exécutée dans la masse rocheuse autour d'un tunnel excavé dans une région de construction d'une centrale électrique souterraine sous haute contrainte de roche initiale. Au cours des mesures, un phénomène de discage de carotte a été observé pendant le sur-carottage. La méthode de sélection des données de contrainte non influencée par le discage de carotte a été proposée, en utilisant un scanneur de tomographie calculée aux rayons X. Il s'ensuit que l'état de contrainte induite provoquée et déterminé à partir des données de la contrainte sélectionnées a été traitée, en effectuant une comparaison avec l'état de contrainte initiale.

Jan 1, 2003

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 P. A. Lilly, W. Sarunic

In most cases, slope movement monitoring data are collected on a temporal basis and displacement or velocity is plotted against time in order to assist the engineer to make judgements about slope behaviour. Once an unusual behaviour pattern has been established, the data are then analysed to estimate when the key inflection points occur in the data, when the slope movements start to accelerate and, ultimately, when the slope is expected to collapse. The identification of these inflection points is sometimes difficult to achieve with the naked eye. This paper presents the application of a trend analysis technique, known as cusums, to assist in this process. The authors have presented a range of data from various real life examples which highlight the effectiveness of the cusums technique. A key aspect of the cusums technique is the use of a constant (K) against which data trends are assessed. This constant is best derived from slope performance data at each site, as each rock mass will behave in its own unique way. The authors have experienced slopes that have had threshold values ranging from 0.1mm/day through to 10mm/day, and therefore a conservative approach should be adopted when assessing the performance of slopes.

Jan 1, 2006

By Van Sint JanM., M. Prudencio

ABSTRACT We report the results of a model-testing program to evaluate the strength characteristics of non-persistent joints. We describe the conditions under which new tensile cracks generate and propagate to connect existing joints so that the rock mass becomes fractured into several blocks, leading to a low strength. The strength of some models was equal to that along a single joint through the full sample length. In models with two joint sets, failure took place along a composite plane, partly sliding along a discontinuous joint and shearing through the intervening intact block of rock, or else by rotation and sliding of the blocks. This last failure mode could also lead to very low model strength. ZUSAMMENFASSUNG Dieser Bericht beschreibt die Ergebnisse von Versuchen mit Modellfelsmassen um den Einfluâ von unterbrochenen Rissen in ihrer Widerstandsfähigkeit zu untersuchen. Es werden die Umstände beschrieben unter denen neue Zugrisse entstehen, sich verbreiten, sich mit bestehenden Rissen verbinden und die Felsmasse in mehrere Felsblöcke zerlegen und zu einer kleinen Widerstandsfestigkeit führen. Der Widerstand einiger Versuchskörper entsprach der Festigkeit eines Risses der die ganze Länge des Versuchskörpers überquert.Versuchkörper mit zwei Rißfamilien versagten unter einer zusammegesetzten Ebene, zum Teil mit Verschiebungen nach unterbrochenen Rißebenen die sich durch Schnittversagen intakter Felsblöcke verbinden, und zum Teil durch Drehungen und Verschiebungen einzelner Felsblöcke. Die letzte Versagunsart kann zu einer stark verminderten Widerstansfähigkeit führen. RÉSUMÉ Nous présentons les résultats de quelques essais fait sur des modèles évaluant les caractéristiques de résistance des fractures discontinues. Nous décrivons les conditions sous lesquelles des nouvelles fissures de traction peuvent s’engendrer et se propager pour faire la connection avec des fractures existantes, de façon que le rocher se fracture en plusieurs blocs, menant à une résistance réduite. La résistance de quelques modèles fut égale a celle d’une fracture traversant toute la longueur du modèle. Pour les modèles ayant deux ensembles de fractures, la rupture a eu lieu sur une surface mixte, causée d’une part, par le glissement sur une fracture discontinue et d’autre part, par la rupture à travers le pont de matériel intact; ou bien par rotation et glissement des blocs. Cette dernière façon de rupture peut aussi aboutir à une très faible résistance des modèles.

Jan 1, 2003

By C. Ntsele

Stirred milling technologies have firmly established themselves in concentrator circuits as energy-efficient alternatives to tumbling ball mills. High and continued increases in electricity costs, coupled with the ever-increasing power consumption by primary grinding circuits due to declining head grades of ore-bodies, provides a compelling case for these technologies. Additionally, the ability to successfully deploy stirred milling in coarse grinding applications extends the range of use in concentrators, thus increasing the opportunity matrix for energy optimization in a flowsheet. This paper therefore details methodologies and strategies that can be applied to evaluate the optimum stirred milling solution for different concentrator applications. These methods and strategies will focus specifically on the two major stirred mill machine types; namely, gravity-induced (VERTIMILL? grinding mill and Nippion-Eirich tower mill) and fluidized (SMD, Isamill?, Knelson-Deswik mill, etc. ). Finally, case studies from circuits across industry and laboratory tests will be used to illustrate the energy benefit from the use of stirred mills.

Jan 1, 2012

By M. Castelli, C. Scavia, S. Marello, A. Allodi

ABSTRACT – This paper investigates the possibility of interpreting the shear band evolution in hard soils and soft rocks as the result of shear propagation from pre-existing natural defects. Thesis done through the application of the principles of Fracture Mechanics, a Slip-Weakening Model(SWM) being used to simulate the non-linear zone at the tips of the discontinuity. Experimental observations have been carried out on prismatic samples of Beaucaire marl through biaxial compression tests in plane strain conditions. A numerical simulation confirms the validity of the proposed approach. RÉSUMÉ – Cet article présente la possibilité d’interpréter l’évolution des bandes de cisaillement dans les roches tendres et les sols raides comme le résultat de la propagation pour cisaillement à partir d’un défaut préexistant. Le Slip-Weakening Model (SWM) a été employé pour modéliser la zone non linéaire a l’extrémité d’une discontinuité. Nous présentons des observations expérimentaux obtenues à travers des essais de compression en déformation plane sur des échantillons prismatiques de marne. La simulation numérique d’un essai confirme la validité de la méthode proposée. KURZFASSUNG – Die vorliegende Arbeit versucht die Ausbreitung von Scherzonen in(bindigen) Böden und im Lockergestein anhand der Entwicklung von Scherrissen ausgehend vonexistierenden Schwachstellen zu erklären. Die Umsetzung erfolgte mit Hilfe der Bruchmechanik,für die Modellierung der nichtlinearen Zone an den Rissenden wurde ein Slip-Weakening-Modell(SWM) eingesetzt. Es wurden zweiaxiale Druckversuche an prismatischen Probekörpern vonBeaucaire Mergel unter der Bedingung eines ebenen Verzerrungszustandes durchgeführt. Dienumerische Untersuchungen bestätigten die Annahmen der untersuchten Theorie.

Jan 1, 2003

By N. J. Wagner, D. G. Modiba

There is currently limited knowledge concerning South African coal deposits as hosts for rare earth elements (REE). This project aims to determine the concentration of REE, including yttrium and scandium (REY+Sc) in various coal seams and adjacent sediments in borehole cores from the Ermelo, Witbank, and Waterberg coalfields in South Africa. Coal petrography (maceral count and vitrinite reflectance), XRD, XRF, sequential chemical extraction procedure (SCEP) before ICPMS, and mineral liberation analysis (MLA) were conducted on the coal and associated sediment samples. The coals were inertinite-rich, medium-rank bituminous coal, with moderate to high ash content. The two dominant minerals in all the coalfields are kaolinite and quartz, except for sample ZBS2M, where dolomite was dominant. The dominant major oxides are Al2O3, SiO2, Fe2O3, and CaO, which concur with the XRD results. The ICP-MS results following SCEP indicated that both coal and the associated sediments were light REY+Sc dominant. There was also an elevation of medium REY+Sc in the Witbank coal’s associated sediment samples. Notably, the samples with the highest REY+Sc results were the sediment samples. The Waterberg samples had the lowest REY+Sc from both the coal (less than 2 μg/g to 7 μg/g) and associated sediments (2 μg/g to 15 μg/g). While the highest REY+Sc was yielded from the Witbank-associated sediments (500 μg/g to 2,500 μg/g). The carbonate fraction step proved to be the most successful leaching step, as most REY+Sc was recovered in that step for all coalfields. In addition to the carbonate fraction, the silicates and sulfide fraction in the Witbank samples, and the ion-exchangeable fraction for the Waterbergassociated sediments samples proved successful in leaching out the REY+Sc. MLA determined that monazite and xenotime in all the coal samples were the REY+Sc-bearing minerals.

Nov 6, 2024

By G. I. McPhail

The authors have conducted several investigations into the prediction of the beach profile of high-density tailings and have found that there are a number of important considerations that need to be taken into account over and above the reliability of the beach profile prediction methodology. These considerations relate to the chemistry of the slurry and specifically the influence of pH and flocculation, both of which have a significant influence on the rheology of the slurry at the discharge point. A number of examples are discussed and a potential testing protocol that will assist in assessing the influence of chemistry ahead of the beach profile predictions is presented. A methodology for assimilating the results of the testing into the likely field situation is discussed, and suggestions are made on application of the results in beach profile prediction. The suspected influence of residual flocculation on the stratification

Jan 1, 2012

Since 2001, the Hybrid Stress Blast Model (HSBM) project members have developed a software suite to model the complete blasting process from non-ideal detonation to muck pile formation. To preserve the physics and improve solution time, the breakage engine uses a combination of analytical models and 2D axisym-metric finite differences to model near-field crushing, coupled to 3D discrete lattice fracturing and distinct element numerical methods to model throw and muck pile development. The model has been validated by comparison with laboratory and field tests in kimberlite. Multiple blasthole simulations are used to demonstrate how changes to blasting parameters can influence downstream efficiencies. Case studies of wall control blasting show that the presplit design must balance the two opposing effects of increased damage with increased charge and decreasing attenuation of the seismic waves with decreasing charge. Modelling of decoupled explosives needs further development. Reducing the charge towards the back of the trim blast results in a much more significant decrease in back damage than altering the timing. The model demonstrates how separation along the weaker planes in a jointed rock can coarsen the fragmentation, leading to inefficient beneficiation, and extends the damage to a distance of at least twice the burden behind from the blasthole, severely compromising the wall stability.

Jan 1, 2012

Assuming that a gold ore has been effectively ground to ensure maximum economic liberation of gold, the circuits that will have the most effect on the successful operation of a gold plant will be that of the leaching and carbon-in-pulp circuit (CIP). The reagent and utilities operating costs associated with leaching, adsorption, elution and regeneration would typically make up some 15% of total operating cost, whilst the capital costs associated with these areas is about 16% of the total. Although not largest (capital and operating costs associated with comminution are generally dominant) these items represent a significant proportion of capital and operating cost. Much more importantly, these plant areas represent the primary gold recovery process and their technical and operational efficiencies will have a significant impact on overall plant efficiency. The objective during process design of these sections is thus to develop a design which provides maximum technical and economic efficiency and which is robust to potential changes in ore throughput, mineralogical characteristics and head-grade. Experience has shown that, particularly for longer life and higher-grade projects typical of the South African underground gold mining industry, small changes in recovery and efficiency have a significant value over the life of the project.

Jan 1, 1999

By W. Carter, P. Chaubal, K. Spaleck, M. Schoeman, J. Bobek, W. Seegers

Keywords: Pyrometallurgy, steel, hearth, blast furnace The Mittal Steel Company operates about 36 blast furnaces on four continents. Furnaces range from 1100 m3 to 4800 m3 inner volume. The focus of the group is to push for increasing productivity and increasing campaign life. This has been especially challenging, as many of these furnaces were not equipped for long campaigns during their prior rebuilds. Monitoring and operating practices have to be modified to match the new philosophy. Mid-campaign hearth repair strategies and hearth design philosophies have had to be reconsidered. The paper describes experiences with the current hearth designs and measures taken for hearth life extension. Additionally, the philosophy of recent hearth re-designs is discussed.

Jan 1, 2006

By O. Naiker

Xstrata has modified and improved on the solid state reduction of chromite (SRC) process that was pioneered by Showa Denko in Japan and previously used at Xstrata?s Lydenburg plant. The history of pre-reduction is a long one, with the SRC process being the first and only commercially successful one prior to Premus. Krupp developed the chromite direct reduction and the rotary hearth for the pre-reduction of chromite. However, these processes have not been successfully commercialised. The are a number of significant differences between Xstrata?s patented Premus and the original Consolidated Metallurgical Industries (CMI) process. These include, the use of lower cost anthracite fines as the reductant source together with the use of unactivated bentonite as the binding agent. In addition the use of oxygen as an energy source is used in Premus but not in the original CMI process. There was a fundamental change in the operational philosophy of the process in that while the original CMI process aimed to maximize metallization of the pellets, the Premus process seeks to maximize the energy output from the kiln while still achieving the required efficiencies and hence increasing furnace output. Premus is designed to reduce electrical energy consumption, provide high recoveries of metallic oxides, and utilizes low cost reductant and energy sources such as anthracite and oxygen respectively. Due to the fact that Premus is one of the most technologically advanced and competitive processes used today in the production of ferrochrome it was the process selected for Xstrata?s new ferrochrome facility, Project Lion, that is due to be commissioned in the third quarter of 2006 in the Steelpoort Valley in Mpumulanga, South Africa.

Jan 1, 2007

By A. Wedepohl

Selective leaching of phases in charge chrome is used in a variety of industrial processes for the production of chromium chemicals. A mineralogical study was made of a range of local charge chrome samples, at various stages of leaching in sulphuric acid (20g/l at 90°C), using mainly a scanning electron microscope (SEM) together with an energy-dispersive spectroscopy analyzer (EDS), and X-ray diffraction techniques. It was found that the leaching behaviour of the different types of charge chrome depends largely on the nature of the secondary phases, which in turn depends upon whether the silicon content is above or below 4 per cent by mass. The leaching behaviour of high-chromium ferrite is anomalous, and it is postulated that the process is analogous to the corrosion of brass by dezincification. Keywords: charge chrome leaching, scanning electron microscope

Jan 1, 2000