Search Documents

By M. Steyn

Until 2000, pricing involved profit taking and cost covering combined with limited global published information. Market information was mostly subjective in nature and large resource companies benefited exclusively from aggregated company information and data. The market constituted producers and consumers only. The nineties saw massive cost cutting drives and re-engineering initiatives and this underwrote the structural changes evident in the late 1990s? economy. This supported South African producers on the international FOB cash cost curve, and ensured profitable coal mining operations. As the debate on relative scarcity of fossil fuels ensued, producers and buyers looked to the developing terminal coal market for direction. The much needed direction was provided when the API coal indices were developed and derivative trading was embraced to include financial institutions, trading houses and hedge funds. The liquidity of coal trades increased rapidly and vastly and market information became obtainable on a daily basis. Interpretation of current and future coal prices became available to all market players and contributed to the sophistication of the market that is now able to participate in risk management of prices, capital expenditure and brownfield developments.

Jan 1, 2010

By H. Basarir

Due to the environmental constraints and the limitations on blasting, ripping as a ground loosening and breaking method has become more popular in both mining and civil engineering applications. Because of the technological advances in dozer manufacturing techniques, more powerful dozer types are available today. Thus, the ground, previously classified as non-rippable, has become rippable. As a consequence, a more applicable rippability classification system is needed which considers both equipment properties as well as rock properties in all applications. This paper is part of a complementary research work and presents the development of a previously published grading rippability classification system by the application of fuzzy set theory. The integrated rippability classification system considers the combined utilization of the rock and equipment properties, as well as expert opinion. Fuzzy set theory was chosen mainly because it deals well with uncertainty in the choice of variables. Although there are apparent sharp or discontinuous boundaries in existing classification systems, practically most of the factors involved in the ripping process are less well defined and boundaries are more blurred (or fuzzy) or uncertain in nature. Also by means of fuzzy logic it is possible to eliminate bias or subjectivity. The validity of the proposed system was checked by the comparison against existing classification systems and direct ripping production values obtained at studied sites. It is seen that by means of fuzzy logic, the uncertainties are reduced and biased usage of the final ratings that appear in alternative systems are efficiently dealt with. Keywords: Fuzzy set theory, rock rippability, rippability classification system, direct ripping, fuzzy inference system.

Jan 1, 2007

By G. Mucsi, F. Kristály, R. Szabó

Kaolin is one of the most important ingredients in porcelain manufacturing. Its main phase is clay mineral containing aluminum hydrosilicate, namely kaolinite. Beside kaolinite it also contains quartz, illite and feldspars, which impair its applicability. Kaolin is a non-reactive material, but metakaolin can be produced by heat treatment (calcination) of kaolin, which is also used by the cement and concrete industry due to its latent hydraulic (pozzolanic) properties. Beside thermal activation, reactive materials can also be produced by mechanochemical activation in general. This paper deals with the mechanochemical activation of kaolin. The raw material was classified into various size fractions, then ground in a batch stirred media mill under varying circumstances (residence time, circumferential velocity). After grinding, the structural changes of the products were investigated by X-ray diffractometry (XRD) and Fourier Transform Infrared Spectroscopy (FTIR). In addition, the particle size distribution of the ground material was determined by laser scattering. As a result of the grinding experiments and analytical measurements of the products, it can be clearly seen that reactivity of kaolin can be improved significantly by mechanical activation in a stirred media mill, but due to its high energy density the circumstances were optimised carefully to avoid aggregation. Keywords: Kaolin, grinding, stirred media mill, mechanical activation, material structure

Jan 1, 2020

By M. G. B. Wheeler

SYNOPSIS This report outlines the development of a model to simulate the radiometric sorting of gold- and uranium-bearing ores. The developed program indicates the optimum mass, reject percentage, and expected reject gold and uranium grades for a radiometric sorter. It achieves this by statistical analysis of the data gathered from a large sample of rocks in the required size range for a particular mine. The program can be used in the optimization of existing sorters, as a design tool for new radiometric sorters, and in feasibility studies on radiometric sorting.

Jan 1, 1989

By P Knight, P A. Walker, H E. Speight

Pushback 8 South is the final cut back on the south wall of the East Pit at BHPBilliton?s Mt Whaleback iron ore mine in the Pilbara region of Western Australia. Development of the cutback commenced in 1999 and is now nearing completion with ultimate pit walls up to 300m high. This paper describes the geotechnical, structural and hydrogeological setting of PB8S, reconciliation between design and slope performance and the slope engineering techniques used to effectively manage the risks associated with the slope. These techniques include slope buttressing and sequential mining with waste backfilling, as well as a detailed program of displacement and hydrogeological monitoring, structural mapping and slope stability assessment. During the course of slope formation recent developments in remote slope displacement monitoring using radar and remote structural mapping using terrestrial photogrammetry have also been applied. Aspects of the PB8S slope management plan are relevant to many large scale open pit slopes. This paper provides geotechnical practitioners with information which may be helpful in managing geotechnical risk in similar environments.

Jan 1, 2006

By B. W. Wallace

Permitted explosives in South Africa are those explosives approved by the relevant State authority for use in fiery coal mines. The main tests that an explosive must pass for this approval are the gallery tests derived from the Buxton (U.K.) classification. These tests are described briefly. In addition, the safety of permitted explosives is affected by their ability to deflagrate, and to produce a naked flame after blasting, rather than to detonate fully. Tests done on this phenomenon are discussed. A further potential hazard of explosives is after-blast fume. The testing and behaviour of several permitted explosives in this respect are covered, both in the laboratory and in the field. Performance testing of permitted explosives, specifically the double-pipe, underwater, and ballistic mortar tests, and their relationship to field use, are considered in some detail. The application of traditional and new tests to permitted explosives leads to guidelines for the safe and efficient formulation and use of these products.

Jan 1, 1986

By V. Labiouse, R. Gärber

The paper aims at clarifying the up-to-now misappreciated role taken by pore water on the design of deep tunnels in saturated porous media. Numerical simulations with a non-dimensional FEM-model emphasise the influence of pore water characteristics (in situ pressure and compressibility) and boundary conditions (lining permeability) on the short and long term underground-structure equilibrium states. These results cannot be achieved by means of monophasic total stress analyses. Dieser Beitrag untersucht den Einfluss des Porenwassers auf die Dimensionierung von tiefen Tunnelbauwerken in wassergesättigtem Untergrund. Numerische Simulationen mittels eines dimensionslosen FEM-Modells betonen den Einfluss der Porenwassereigenschaften (in-situ Druck und Kompressibilität) und der hydraulischen Randbedingungen (Tunnelausbaudurchlässigkeit) auf Kurz- und Langzeitverhalten des Untergrund-Ausbau Gleichgewichts. Diese Ergebnisse können nicht ermittelt werden anhand von Einphasen- und Totalspannungsmodellen. L’article s’intéresse au rôle méconnu de l’eau interstitielle dans le dimensionnement de tunnels profonds creusés dans des milieux poreux saturés. Des calculs adimensionnels par éléments finis soulignent l’influence des caractéristiques de l’eau interstitielle (pression in situ et compressibilité) ainsi que des conditions aux frontières (perméabilité du revêtement) sur les équilibres court et long terme de l’ouvrage. Ces résultats ne peuvent pas être obtenus par des calculs en contraintes totales.

Jan 1, 2003

By S. Burks

This paper develops the themes explored by the authors at the Fourth International Platinum Conference,. Optimization techniques can be used to significantly increase the value of mining businesses by enabling better long-term planning decisions. Open pit and underground mine design, mine scheduling, cut-off grade and blending, stockpiling, and the linking of these to flexible elements of the metallurgical recovery processes are all evaluated together. Transport or sale of intermediate products and the requirements of the product metal markets can also be considered. Experience shows that net present value (NPV) can potentially be increased by 5-35 per cent or more, usually even before the expenditure of significant amounts of project capital. The case studies presented include: > An existing operation with multiple open pits and PGM concentrators linked to offsite downstream processing facilities, and with infrastructure constraints for which the scheduling of current operations and the potential for expansion were investigated > An existing operation with an integrated portfolio of mines, concentrators, smelter, and refinery, for which the various possible sources of ore for processing were prioritized to match the downstream process plant constraints and the product markets > An underground operation in Zimbabwe for which the optimum mining width was calculated and expansion plans were evaluated > An underground mine with many separate mining sections, for which a revised schedule was developed aiming to keep the shaft system and processing plant at capacity with the highest net value material available at any time throughout the life of mine. In the concluding section of the paper, a few brief notes are included suggesting how the strategic recommendations from enterprise optimization studies may be implemented by the owner's team.

Jan 1, 2013

This International Mine-Surveying Conference will take place in Budapest (Hungary) from 5 to 14 June, 1972. Detailed information can be obtained from the Mine-Surveying Working Committee of the Hungarian Mining and Metallurgical Society. Write: OMBKE Bányaméröi Munkabizottsag Budapest, V., Szabadsag ter 17, Hungary. SYMPOSIUM ON NICKEL The 'Gesellschaft Deutscher Metallhiitten-und Berglaute' is holding a Symposium on nickel on 24-25 September, 1970 at Wiesbaden, on the occasion of the G.D.M.B. Annual Meeting. Some 24 papers will be presented by metallurgists from many important companies around the world. Information may be obtained from The Secretary, G.D.M.B., Postfach 210, 03392 Clausthal-Zellerfeld, German Federal Republic. VISIT TO THE COUNCIL FOR SCIENTIFIC AND INDUSTRIAL RESEARCH On 23rd June, 1970, members of the Institute visited the C.S.I.R. in Pretoria. More members had booked for this tour but the current flu epidemic caused cancellations which was unfortunate. The visit was organised with military precision, which prevented detailed discussion of any particular subject, but provided a bird's eye view of a large number of interesting projects. The visit was packed with interest for all and those requiring further information were invited to contact the relevant divisions afterwards. Or Denkhaus welcomed the delegates and stressed the importance of integrating research efforts with industry's requirements. An excellent colour and sound film was shown which depicted the work of the Rock Mechanics division. This showed very clearly methods used for preparing rock samples and demonstrated the machines and instruments for the various tests. It made one realise the extent to which this research has been integrated with the actual mining situation. The fullscale experiments underground showed the failure of pillars under applied loads and were very interesting. This is undoubtedly a film which all mining people should see. After the film the rock mechanics laboratories were visited where the actual machines were seen and described. We then visited the metal and strength mechanics sections where the metallurgists were able to see some interesting experiments and tests. We also visited the Aeronautics Research group where a large 1 000 hp wind tunnel was inspected. We were told enough about this to realise something of the complexities involved in the design and operation of a closed circuit tunnel of this type. The tunnel is used for tests on models which are necessary for the design and modification of aircraft. After a very excellent lunch at the C.S.I.R. recreation centre, the delegates attended two lectures-one by Mr. Mandersloot of the Chemical Engineering group, who outlined the varied functions of this group and told us something of their work. Of particular interest was the research into the suitability of various South African manganese ores for dry cell batteries. Work on the thickener settlement studies interested the metallurgists. The second lecture was given by Mr Donaldson of the National Building Research Institute. This Institute has about ten divisions each of which covers a particular aspect of building research. The work of the soil mechanics division was described in detail and illustrated by coloured slides. This was particularly interesting and demonstrated clearly how building failures result from lack of attention to detail of construction where unstable soil conditions exist. Cracks in walls of compound blocks brought the subject home forcibly to the mining delegates. This division has also caried out important work on sinkholes and sUmes dams and produced some positive results. Altogether the visit was most interesting and enjoyable. It was made more worthwhile because the emphasis was on the work being carried out and not on just seeing the laboratories. The Institute is greatly indebted to the C.S.I.R. and its staff for the very excellent arrangements made.

Fathi Habashi, Chalcopyrite. Its chemistry and metallurgy. New York, McGraw-Hill, 1978. 165 pp. RI9,95. Loss prevention and safety promotion The Proceedings of the 2nd International Symposium on Loss Prevention and Safety Promotion in the Process Industries, Heidelberg, 6th to 9th September, 1977, are now available. Chemical reaction engineering The Proceedings of the 4th International/6th European Symposium on Chemical Reaction Engineering (4th ISCRE) held at Heidelberg, Federal Republic of Ge rmany, from 6th to 8th April, 1976, are available from DECHEMA Deutsche Gesellschaft fur Chemisches Apparatewesen, P.O.B. 970146, D-6000 Frankfurt/ Main, West Germany, at the price of DMlOO plus postage and packing. Books received The Institution of Mechanical Engineers Proceedings Volume 190. Tribos abstracts on friction lubrication wear. Published by BHRA Fluid Engineering, Cranfield, Bedford MK 43 OAJ England. Price £30 (UK), US$72 (Europe), Seawater corrosion handbook, edited by M. M. Schumaker. Noyes Data Corporation Publicity Department, Mill Road at Grand Ave., Park Ridge, NJ 07656. 494 pp. Australian mineral industry quarterly 31(1) 1978 and 31(2) 1978. Bureau of Mineral Resources, Geology and Geophysics, Box 378, Canberra City, ACT 2601 Australia. Subscriptions $8, individual number $2. Mineral and NIM reports Report no. 1996 The extraction of gold from chloride solutions. (10th Nov., 1978). Report no. 1898 Batch and pilot-plant tests on M erensky Reef ore from the Western Platinum Mine. (8th Jun., 1977; reissued 30th Jan., 1979). Report no. 1920 A mineralogical investigation of Mamatu'an and Wessels manganese ores. (15th Sep., 1977; reissued 3rd Jan., 1979). Report no. 1978 The preparation and certification of a referencesample of magnetite ore. (22nd Dec., 1978). Report no. 1998 Electrode response to the addition of zinc during the cementation of gold. (25th Jan., 1979). Report no. 2002 The spectrochemical determination of phosphorus, magnesium, and iron in phosphate rocks and sulphuric acid leach liquors. (26th January, 1979). Report no. 1992 The use of emission spectrometry for the determination of impurities in metals. (24th Jan., 1979). Report no. 2003 An electrodeless conductivity meter of improved sensitivity and reliability. (28th Feb., 1979). Report no. 2005 The spectrometric analysis of manganese-bearing materials with particular reference to ferromanganese slags and metals. (16th Mar., 1979). Report no. 2006 An examination of procedures for the analysis of dry powders by atomic-absorption spectrophotometry. (28th Feb., 1979). Report no. 2007 The instrumentation and computerization of a 25 MV.A submerged -arc furnace. (25th Mar., 1977; reissued 16th Mar., 1979). Corrosion The International Corrosion Council has decided to hold the next Internat ional Congress on Corrosion in Mainz, Federal Republic of Germany, from 6th to 11th September, 1981. Process control The First European Symposium on Real -time Datahandling and Process Control will be held in West Berlin from 23rd to 25th October, 1979. Geomechanics The 28th Geomechanics Colloquy, organized by the Oosterreichische Gesellschaft fur Geomechanik, is to be held at Salzburg on 18th and 19th October, 1979. Geosta tistics A short course on 'Geostatistics for exploration and production planning' is being conducted by the Applied Earth Sciences Department, Stanford University, California, from 27th to 31st August, 1979. Business administration The Twelfth Executive Development Programme of the Graduate School of Business Administration, University of the Witwatersrand, is to be held from 9th July to 17th August, 1979. The engineer and the law A series of four meetings on the above subject is being conducted by the Measurement, Computation and Control SubCommittee of The South African Institute of Electrical Engineers. Lead smelter for South Africa? The National Institute for Metallurgy and Gold Fields of South Africa are making a comprehensive joint investigation of the technical and economic viability of an integrated lead smelter. Conference on titanium The Fourth International Conference on Titanium will be held from 19th to 22nd May, 1980, in Kyoto, Japan.

Jan 1, 1979

By D. Grgic, A. Giraud, F. Homand

RESUME : Le comportement mécanique partiellement saturé du minerai de fer a été étudié à partir d’essais de compression simple sur des éprouvettes à pression capillaire imposée par les solutions salines. Les échantillons restent peu saturés (32 %) même pour une humidité relative de 94 %, du fait de la présence de mésopores. Jusqu’à 90 % d’humidité relative la résistance diminue régulièrement. De 90 % à 94 % une forte chute est observée et pourrait être liée à la fois aux effets capillaires et à l’hydratation de certains minéraux. Le cycle hydrique subit par la roche dans la mine a été modélisé en 1D à l’aide d’un code de calcul entièrement couplé pour les milieux poreux partiellement saturés. Les calculs ont montré notamment une diminution importante en paroi des contraintes totales au cours de la phase de désaturation et une augmentation importante au cours de la phase de resaturation. Ces variations pourraient induire un endommagement du massif et être à l’origine d’instabilités, et soulignent l’intérêt d’une modélisation avec une géométrie plus adaptée. MOTS-CLEFS : mines de fer, partiellement saturé, pression capillaire, résistance, modélisation. ABSTRACT : The partially saturated mechanical behavior of iron ore has been studied from uniaxial compression tests on samples in which the suction is imposed with aqueous solutions. Samples are little saturated (32 %) even for a 94 % relative humidity because pores are too large. Up to 90 % relative humidity the strength decreases regularly. From 90 % to 94 % a great decrease is observed ; it could be explained by the capillary effects and the moisturizing of some minerals. The hydrous cycle imposed to the rocks in the mine has been modeled with an 1D fully coupled code for partially saturated porous media. The computations have shown an important decrease in the total stresses at the wall during the desaturation stage and an important increase during the re-saturation stage. These variations could induce a rock mass damage and instabilities, and highlight the necessity of a modeling with a well-adapted geometry. KEY-WORDS : iron mines, partially saturated, suction, strength, modeling. ZUSAMMENFASSUNG : Das mechanische Verhalten von teilweise gesättigten Eisenerz wird durch einachsige Druckversuche untergesucht. Die Prüfkörper haben einen durch Salzlösungen gestimmten kapillarischen Druck. Sie bleiben kaum gesättigt (32 %), sogar bei einer relativen Feuchtigkeit von 94 %, aufgrund der Anwesenheit von Mesoporen. Bis eine relative Feuchtigkeit von 90 % verringert sich gleichmässig die Druckfestigkeit und zwischen 90 % und 94 % merkt man eine starke Abnahme in Verbindung, möglicherweise, mit kapillarischen Effekten und Hydratation von bestimmten Mineralen. Die nümerische 1D Modellisierung des gezwungenen Wasserzyklus im Stein der Mine ist mit einem für porösen Medien ganz vernetzten Rechnungcode geführt. Sie zeigt besonders ein bedeutendes Sinken der Gesamtspannung während der Entwässerung und eine bedeutende Steigerung während der Sättigung. Diese Veränderungen könnten die Beschädigung des Gesteines herbeiführen und die Grundlage von Unstabilität sein. Sie unterstreichen die Wichtigkeit eine Modellisierung mit einer gut geeigneten Geometrie. STICHWÖRTER : Eisenminen, teilweise gesättigt, kapillarischer Druck, Druckfestigkeit, Modellisierung.

Jan 1, 2003

By M. Helm

Over the last 40 years, numerous investigations have focussed on the preg-robbing capacity of carbonaceous material during gold ore processing. Various techniques have been applied to characterize the physical and chemical properties of the carbonaceous material in efforts to predict its preg-robbing capacity. The present study, which forms part of an ongoing investigation, is specifically designed to increase the understanding of preg-robbing in ores containing carbonaceous material. In excess of 100 samples from 13 gold mines located in major gold provinces of the world have been incorporated into the present study. These samples were characterized using industry standard metallurgical techniques and were shown to have gold adsorption capacities ranging from a few grams to many hundreds of grams of gold per ton of ore. Further analysis showed that the crystalline nature of the carbonaceous material, which is related to its geological history, is important in determining the preg-robbing capacity of an ore. This finding builds on the common understanding that the preg-robbing behaviour of an ore is related to the amount (or abundance) of carbonaceous material present in that ore. In this study, Raman spectroscopy was used to evaluate the physical nature of carbonaceous material. This is a tool which has been successfully applied by researchers for the characterisation of carbon materials, with respect to crystallite size and lattice defects. Raman analysis of the samples included in this study showed varying degrees of disorder in the carbonaceous materials from the different deposits. Comparison of the Raman spectra with the gold loading capacities of the samples indicated a direct relationship between the structure of the carbonaceous material and its capacity to preg-rob gold. From this, a simple and robust method has been developed based on the Raman spectra of the sample and carbonaceous material content to predict the preg-robbing capacity of an ore. The potential exists to develop a predictive tool using Raman spectroscopy for characterising the preg-robbing capacity of an ore. Such a tool would have potential application in projects ranging from the early stage of exploration through to more detailed feasibility studies and mining operations. The result of applying the predictive method outlined in this paper would be the effective and proactive management of the deleterious influence of carbonaceous material on gold recovery in mining operations.

Jan 1, 2009

By W. G. Huang

To recover the coal resources of high-sulphur anthracite in Jincheng Mining Area, underground coal gasification (UCG) of No. 15 seam in Fenghuangshan Coal Mine was proposed. The feasibility of the project was confirmed by investigations of occurrence conditions, coal properties, and roof conditions, as well as experimental studies and theoretical analysis. It was found that UCG technology is appropriate to be adopted in the mining of the No. 15 seam, due to the stable rock conditions, simple geological structure and hydrogeology, the high carbon content of the coal, non-cohesiveness, medium-thermal stability, high ash fusion temperature, and weak reactivity with CO2. Further factors are the characteristics of the immediate roof, which consists of 9.11 m of limestone and mudstone with a compact structure and low permeability, and 4.27 m of dominantly mudstone with low permeability.

Jan 1, 2012

Often plant performance suffers as a result of poor control. Poor control leads to low mill throughputs, poor classification and less than satisfactory concentrate grades and overall recoveries. By using the appropriate control tools, substantial gains in plant performance can be made. Mintek?s MillStar and FloatStar controllers have been implemented at various sites across the world. The MillStar controller incorporates leading technology that controls process units from the mill feed through to the flotation feed. Typical results show that milling circuit throughput is increased by 6-10 % and the final product grind size is tightly controlled, thereby enhancing flotation performance. The FloatStar controller is aimed at stabilising and optimising flotation circuits. Through improved level control alone, recovery improvements of up to 1 % have been achieved. Furthermore, by using on-line grade analysers, the controller stabilises final concentrate grades, whilst maximising flotation recovery.

Jan 1, 2005

By P. Maais

This paper gives an account of the development of a plant for the differential flotation of mixed sulphide ore, special reference being made to the separation of copper and zinc sulphides. The uniqueness of the geology, mineralogy, and metallurgy of each complex ore-body is stressed. Consideration is given to the scale-up of laboratory data, and to some of the factors involved in the design of milling and flotation plants for this type of ore. Process control and development are discussed, as are the human requirements for the optimum operation of a concentrator.

Jan 1, 1980

By A. Doroudgar, H. Noferesti

Unstable rock failure or rock bursting is one of the most dangerous problems in deep hard rock mines. This type of failure, that occurs uncontrollably, is associated with a significant release of strain energy from the surrounding rock. In this study, the numerical simulation of unstable rock failure was carried out using the three-dimensional explicit Lagranian finite-volume finite difference method to identify the onset and location of unstable failure events in the model. On this basis, a numerical simulation of mine pillars with width-to-height ratios of 0.5, 2 and 3 was performed. A criterion was developed, based on the calculation of the elastic strain energy, to determine the prone areas for the initiation of rockburst in the models. The results of this study showed that, in softer loading systems, due to large amounts of stored elastic strain energy, an unstable equilibrium is established, which leads to the rapid transfer of strain energy to the rock in the form of violent failure. It was also found that the unstable failure starts at the corners and free surface of the model. The new criterion developed in this study may help predict the occurrence of rockbursts in slender pillars and the design of pillars to control human and financial losses caused by this phenomenon.

Nov 27, 2024

By M. Nicolle

The Tati Activox® Project will be the first full-scale implementation of the patented Activox® process (The Tati Activox® project was deferred in 2008. Please refer to the Norilsk Nickel press issue on the topic for more info). The process was developed by Norilsk Process Technology and has been tested on Tati mine sulphide concentrates in laboratory, pilot and demonstration plant scales and demonstrated its viability. There are inherent risks to the final scale-up of the process from the demo plant and one of them will be investigated in this paper. Compartment 1 is designed to leach approximately 77% of the total nickel leached. For this reason agitation requirements in the first compartment of the autoclave are reviewed. An attempt is made to minimize the process and mechanical risks associated in achieving oxygen mass transfer into the slurry solution. The agitator powers for oxygen mass transfer are calculated using empirical correlations and compared to demonstration plant testwork. The resulting gassed power per unit volume (P/V) is higher than most commercial autoclaves and raises uncertainty on the viability of using such high unit power inputs. Additionally, there is concern about the ability of the autoclave shell to withstand and support the higher loading of large agitators. An alternative solution to designing for the increased P/V is assessed in which the number of compartments within the autoclave is reduced from 5 to 4 by removing the compartment wall separating compartments 1 and 2. This results in an enlarged first compartment containing 3 agitators instead of 2. Therefore the compartment 1 oxygen demand is supplied through 3 agitators, which lowers the P/V per agitator. The reduction in the number of autoclave compartments raises the potential for short-circuiting the mean flow pattern by slurry particles. Short-circuiting and low velocity zones could result in a lower recovery of metal and localized hot spots, respectively. A computational fluid dynamic (CFD) analysis was conducted to quantify these concerns and also to evaluate further design considerations. The results indicate that the proposed design change to 4 compartments affects short-circuiting. The impact of increased short-circuiting on the overall autoclave recoveries is not quantified, however; it is expected to be negligible based on testwork done in the Tati Demonstration Plant and similar modifications made to another operating autoclave. The CFD analysis also suggests that there will be no low velocity zones within the compartment.

Jan 1, 2009

[Ferro Alloys Producers Association The South Africa Institute of Mining and Metallurgy www.saimm.co.za Mintek www.mintek.co.za Eskom www.eskom.co.za ]

Jan 1, 2004

By B. Dias, P. C. Schutte

Work-related musculoskeletal disorders (WMSDs) affect the wellbeing of workers and result in poor quality work, lower work performance and decreased motivation. In contrast to ‘occupational’ diseases where there is a direct cause-and-effect relationship between hazard and disease (e.g., asbestos and asbestosis, lead and lead poisoning), ‘work-related’ diseases are multifactorial, where the work environment and the type of work that is performed contribute significantly to musculoskeletal disorders. WMSD is the term used to describe disorders and diseases of the musculoskeletal system (i.e. muscles, joints, ligaments, tendons and nerves). WMSDs are by definition a work-related phenomenon. The literature shows inarguably that certain jobs and certain work-related factors are associated with a significant risk of contracting a WMSD. It is assumed that repeated movements and postures, static work, continuous loading of the tissue structures or lack of recovery time, trigger or cause a pathological process that then manifests itself as a WMSD. This paper looks at the prevalence of the WMSD condition at three mines in South Africa: a coal, a gold and a platinum mine. Predisposing factors that include work factors, presentation of symptoms and psychological factors will be discussed in the paper.

Jan 1, 2003

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