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Tests were carried out in a Hallimond microflotation cell and a Denver D12 cell on typical residue material from a gold mine in the Orange Free State (South Africa), in which 50 per cent of the kerogen was larger than 100 µm in size. Although kerogen is naturally hydrophobic, the observed unexpectedly poor flotation reponse may be due to occlusion of the kerogen by a slime coating and subsequent depression of the slime by guar gums. The recovery of gold from samples spiked with kerogen increased, with no significant reduction in grades, when a petroleum-based collector and tetrasodiumpyrophosphate (a dispersant) were used.

Jan 1, 1985

By J. Gholamnejad

Determination of the optimum production schedules over the life of a mine is a critical mechanism in open pit mine planning procedures. Long-term production scheduling is used to maximize the net present value of the project under technical, financial, and environmental constraints. Mathematical programming models are well suited for optimizing long-term production schedules of open pit mines. There are two approaches to solving long-term production problems: deterministic- and uncertainty- based approaches. Deterministic-based models are unable to deal with grade and geological uncertainties, which are two important sources of risk in mining industries. This may lead to discrepancies between actual production obtained by these algorithms and planning expectations. In this paper, a new binary integer programming model was developed for long-term production scheduling that incorporates geological uncertainty within the orebody. Then, traditional and uncertainty-based models are applied to an iron ore deposit. Results showed that the uncertainty-based approach yields more practical schedules than traditional approaches in terms of production targets.

Jan 1, 2012

The 90th Annual General Meeting of The South African Institute of Mining and Metallurgy was held at Kelvin House, Johannesburg, on 19th August, 1987. Dr H. Wagner (President) was in the Chair and declared the meeting open at 16h00. Obituaries The President read out the names of the departed Members as follows: N.M. Airey, F.J. Kisbey-Green, Dr R.A. Pelletier, C.B. Anderson, A.R. Cator, J. van Heerden, P.J. Burman, C.C. Crosson, M. Livingstone¬Blevins, S.T. Firman, V.E. Kisbey-Green, and A.L. Corna. All stood and observed a moment of silence as a mark of respect. Minutes The minutes of the 89th Meeting of the SAIMM, which was held on 20th of August, 1986, were confirmed.

Jan 1, 1987

By S. Kahraman

The prediction of rock properties from indirect testing methods is important, particularly for preliminary investigations since indirect tests are easier and cheaper than the direct tests. In this study, we investigate the predictability of the uniaxial compressive strength (UCS) and Brazilian tensile strength (BTS) of rocks from the indentation hardness index (IHI) obtained using point load apparatus. Forty-six different rock types, 14 of which were igneous, 15 were metamorphic, and 17 were sedimentary were tested in the laboratory. The UCS and BTS values were correlated with the corresponding IHI values and the results were statistically analysed. The influence of rock classes on the relationships was also investigated. A strong correlation between UCS and IHI was found for all data. The correlation between BTS and IHI is not as strong as the correlation between UCS and IHI. However, it is in the acceptable limits. When the regression analyses were repeated for igneous, metamorphic, and sedimentary rocks, the correlation coefficients were generally increased. The results show the UCS and BTS can be estimated from IHI. In addition, the effect of rock classes on the relationships between IHI and both UCS and BTS is important.

Jan 1, 2012

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

Jan 1, 2010

By C. A. Snyders

The research presented in this paper investigated the practical aspects of the recovery of platinum group metals (PGMs) from a dilute cyanide leach solution containing base metals, in a manner similar to that used for gold extraction in a typical CIP process, and focuses on both the adsorption and elution stages. The carrier-phase extraction of precious metals using activated carbon offers significant advantages over other processes in terms of simplicity, the high pre-concentration factor, rapid phase separation, and relatively low capital and operating costs. As a sorbent, activated carbon is still by far the most important material because of its large surface area, high adsorption capacity, porous structure, negligible environmental toxicity, low cost, and high purity standards. Adsorption tests were conducted on a pregnant alkaline leach solution (0.15 ppm Pt, 0.38 ppm Pd, 0.1 ppm Au) resulting from cyanide extraction performed in column leach tests. The initial adsorption rates of Pt, Pd, and Au were very fast and recoveries of these three metals were approximately 90 per cent after 2 hours, and 100 per cent for Pt, 97.4 per cent for Pd, and 99.9 per cent for Au after 72 hours. The parameters that influence the extraction of PGMs and Au were examined to assess their relative importance during the adsorption process in order to provide the basis for process optimization. The concentration of thiocyanate was not identified as significant factor for PGMs adsorption, while Ni concentration was the most significant extraction process parameter. Base metal cyanide complexes adsorb and compete with the PGM complexes for sites on activated carbon, and while copper adsorption can be minimized by adjusting the residence time, Ni adsorbs at approximately the same rate as the PGMs, influencing the loading capacity and adsorption kinetics of the PGMs. The feasibility of eluting platinum and palladium cyanide complexes from activated carbon using an analogue of the AARL process was investigated. Platinum and palladium elute from activated carbon almost to completion in 4 to 5 bed volumes at 80°C, while the elution of gold at this temperature is slow, with a significant amount of gold still to be eluted after 16 bed volumes. The equilibrium loading of gold is exothermic in nature (Fleming and Nicol, 1984) which will result in an increase in gold elution kinetics with an increase in temperature at similar pre-treatment conditions. A similar result was found for the elution of Pt and Pd. Cyanide pre-treatment was found to have a significant influence on PGM elution. Higher cyanide concentration in the pre-treatment step results in more efficient elution up to a point, and results suggest the possibility of an optimum cyanide concentration, beyond which elution efficiency starts decreasing due to increased ionic strength.

Jan 1, 2013

The following notes have been compiled to assist authors in the preparation of papers for presentation to the Institute and for publication in the Journal. All papers must meet the standards set by the Council of the Institute, and for this purpose all papers are referred to at least two referees appointed by Council. STANDARDS FOR ACCEPTANCE To merit consideration papers should conform to the high standards which have been established for publication over many years. Papers on research should contain matter that is new, interpretations that are novel or of new significance and conclusions that cast a fresh light on old ideas. Descriptive papers should not be a repetition of well-known practices or ideas but should incorporate developments which would be of real interest to technical men and of benefit to the mining and metallurgical Industry. In some cases a well prepared review paper can be of value, and will be considered for publication. All papers and particularly research papers, no matter how technical the subject, should be written with the average reader of the Journal in mind, to ensure wide interest. The amount of textbook material included in a contribution should be the minimum essential to the argument. The length of a paper is not the criterion of its worth and it should be as brief and concise as possible, consistent with the lucid presentation of the subject. Only in very exceptional circumstances should a paper exceed 15 pages of the Journal (15 000 words, if there are no tables or diagrams). Six to ten pages is more normal. NOTE: Papers in the Journal are printed in 10 point type, which is larger than the 8 point type used on this page. For special publications Council may decide on page sizes smaller than A4 used for this Journal. The text should be typewritten, double-spaced, on one side only on A4 size paper, leaving a left-hand margin of 4 cm, and should be submitted in duplicate to facilitate the work of the referees and editors. LAYOUT AND STYLE Orthodox sequence Title and author's name, with author's degrees, titles, position. Synopsis. Index, only if paper is long and involved Introduction, including a brief statement of conclusions. Development of the main substance. Conclusions. in more detail. Acknowledgements. References. Title: This should be as brief as possible, yet give a good idea of the subject and character of the paper. Style: Writing should conform to certain prescribed standards. The Institute is guided in its requirements by: Collins, F. H., Authors & Printers' Dictionary-Oxford University Press. Hart, H. Rules for Compositors and Readers. Humphrey Milford (familiarly known as the Oxford Rules). Fowler, H. W. & F. G. The King's English-Oxford University Press. General: A few well selected diagrams and illustrations are often more pertinent that an amorphous mass of text. Over-statement and dogmatism are jarring and have no place in technical writing. Avoid the use of the first person, be objective and do not include irrelevant or extraneous matter. Avoid unnecessary use of capitals and hyphens, while punctuation should be used sparingly and be governed by the needs of sense and diction. Sentences should be short, uninvolved and unambiguous. Paragraphs should also be short and serve to separate basic ideas into compact groups. Quotation marks should be of the 'single' type for quotations and "double" for quoted matter within quotations. Interpretations in the text should be marked off by parentheses ( ), whereas brackets [ ] are employed to enclose explanatory matter in the text. Words to be printed in italics should be underlined singly. For small capitals they are to be underlined DOUBLY and for large capitals TREBLY. If there is any problem in producing formulae accurately by typewriter they should be inserted by handwriting in ink in the copy forwarded by authors. Abbreviations and symbols are laid down in British Standard 1991. Abbreviations are the same for the singular and plural, e.g. cm for centimetre and centimetres, kg for kilogram and kilograms. Percentages are written in the text as per cent; the symbol % is restricted to tables. A full stop after an abbreviation is only used if there is likely to be confusion of meaning. Metric System: The Systeme International d'Unites (S.I.) is to be used for expressing quantities. This is a coherent system of metric units derived from six basic units (metre, kilogramme, second, ampere, kelvin, and candela), from which are derived all other units, e.g. the unit of force is the newton (N) for kilogramme metre per second per second (kg m/s2). Always use the standard metric abbreviations. Commas must not be used for separating groups of digits. For ease of reading digits should be grouped in threes counting from the decimal point towards the left and the right. Illustrations: Drawings and diagrams are to be in black India ink and should be about 18 cm wide. When submitting graphical representations avoid a fine grid if possible. Curves should be in heavy line to stand out. Lettering too should be bold as a reduction in size is often involved in the printing process. (A single column is 8.5 cm wide.) Numbering of tables should be in Roman numerals: I, 11, etc. and figures in Arabic numerals: Fig. 1, Fig. 2, etc. (Always use the abbreviation for figure.) Photographs should be black and white glossy prints. As a guide to the printer the author should indicate by means of notes in the typescript where tables and figures, etc. are to appear in the text. Paragraphs: A decimal system of numbering paragraphs may be used when the paper is long and complicated and there is a need for frequent reference to other parts of the paper. Proof correction: Galley proofs are sent to authors for the correction of printers' errors and not for the purpose of making alterations and additions which may be expensive. Should an author make alterations which are considered excessive, he may be required to pay for them. Standard symbols as laid down in British Standard 1219C should be used. SYNOPSIS It is most important that the synopsis should provide a clear outline of the contents of the paper, the results obtained and the author's conclusions. It should be written concisely and in normal rather than abbreviated English and should not exceed 250 words. While the emphasis is on brevity this should not be laboured to the extent of leaving out important matter or impairing intelligibility. Summaries simplify the task of abstractors and therefore should present a balanced and complete picture. It is preferable to use standard rather than proprietary terms. FOOTNOTES AND REFERENCES Footnotes should be used only when they are indispensable. In the typescript they should appear immediately below the line to which they refer and not at the foot of the page. References should be indicated by super-script, thus. . .1 . . .2. Do not use the word Bibliography. When authors cite publications of other societies or technical and trade journals, titles should be abbreviated in accordance with the standards adopted by this Journal. GENERAL The Council will consider the publication of technical notes taking up to three pages (maximum 3 000 words). Written contributions are invited to the discussion of all papers published in the Journal. The editors, however, are empowered by the Council to edit all contributions. Once a paper or a note has been submitted to the Institute, that document becomes the property of the Institute, which then holds the copyright when it is published. The Institute as a body is, however, not responsible for the statements made or opinions expressed in any of its publications. Reproduction from the Journal is permitted provided there is full acknowledgement of the source. These points should be borne in mind by authors who may submit their work to other organizations as well as to the Institute. P.W.J.vR.

By J. W. Latilla, J. J. van Wijk

In late 1997 a request was received to assist with determining the powered support unit (shield) load capacities for the planned 2 seam short wall. This project had a number of aspects which made it attractive to utilize numerical modelling in conjunction with other more conventional design tools in the design of the shields. Amongst these were: The 2 seam panels were to be laid out about 25 m below the previously short walled 4 seam, the 4 seam had in turn been over-mined by the 5 seam long wall, the proposed face height of the 2 seam short wall was 5.5 m while the 4 seam had been mined at 4 m. The top seam in the area (5 seam) had been mined at between 1.5 and 2.2 m high, the face conditions with about 95 m of broken material applying dead weight loading to the 2 to 4 seam inter-burden septum were hard to predict and cyclical loading due to the presence of strong sandstone bands in the 2 to 4 seam inter-burden. The basic thrust of the study was to take the known, and successful, situation (4 seam short wall) and carry out comparative modelling to enable prediction of likely 2 seam conditions. Some two dimensional aspects studied were: 5 m goaf hanging up behind shields, stresses in beams to determine likely first goaf roof span, stresses in cantilever beams to asses cyclical loading due to sandstone bands in the interburden being loaded by the overlying goaf and stresses on chain and crush pillars adjacent to the goaf edge. Three dimensional aspects that were investigated included: Load distribution along face for close goafing and 5 m goaf hang-up and load in a 1 m wide rib modelled in the position of the powered support units. From the modelling it was possible to determine the optimal shield leg capacity of the new 2 seam equipment. These outputs were used when drawing up the technical specifications for manufacture of the new equipment. The face was successfully commissioned in August 2002. Fin 1997, requête fut faite pour aider à la détermination des capacités de charge pour l’unité de soutènement mécanisée (bouclier) pour la couche 2 courte taille en projet. Certains aspects de ce projet le rendaient intéressant pour utiliser la modélisation numérique en même temps que d’autres méthodes conventionnelles pour la conception des boucliers. Parmi ces aspects se trouvaient : Les panneaux de la couche 2 devaient être placés environ 25 m au dessous de la couche 4 courte taille ; la couche 4 avait été remplacée par la couche 5 longue taille ; la hauteur de taille proposée pour la couche 2 courte taille était 5.5 m, tandis que la couche 4 avait été exploitée à 4 m. La couche supérieure de la région (couche 5) avait été exploitée entre 1.5 et 2.2 m de hauteur ; il était difficile de prédire les conditions de taille, avec environ 95m de matériaux cassés ajoutant une charge morte à la plaque de séparation entre les couches 2 et 4 et un chargement cyclique causé par des bandes de grès dans l’entre-fardeau 2-4. L’idée principale de l’étude fut de prendre la situation connue et réussie (couche 4 courte taille) et de faire une modélisation comparative pour prédire les conditions probables de la couche 2. Certains des aspects à double dimension qui furent étudiés étaient : Un accrochage de remblai de 5m derrière les boucliers ; contraintes dans les poutres pour déterminer le premier intervalle probable entre remblai et toit ; contraintes dans les poutres en porte-à-faux pour évaluer le chargement cyclique causé par les bandes de grès dans l’entre-fardeau qui est accablé par le remblai et les contraintes sur les piliers par chaîne et d’écrasement adjacents au bord du remblai. Aspects à trois dimensions qui furent étudiés : Distribution de la charge le long de la taille pour les remblais proches et l’accrochage de remblai de 5 m et la charge dans une nervure de 1 m de large modelée dans la position des unités de soutènement mécanisées. La modélisation a permis de déterminer la capacité de portée optimale du bouclier du dispositif nouveau pour la couche 2. Ces résultats furent utilisés pour dresser les spécifications techniques pour la fabrication de l’équipement nouveau. La taille fut commissionnée avec succès en août

Jan 1, 2003

Grains are subject to contamination by mycotoxins which are metabolic by-products of various fungi. The fungal infestations produce local concentrations of the mycotoxins thousands of times higher than the average. These facts make the sampling of the grain for assessment of the mean mycotoxin levels potentially very difficult. In the context of sampling theory, this morphology of the infestations creates a very high distributional and intrinsic heterogeneity of the grain shipment. The distributions of mycotoxin concentrations in seaborne shipments that exist at loading and the number and intensity of infestations that develop under shipping conditions are unknown. All grain shipments carry spores that may give rise to mycotoxin-producing colonies; moisture and temperature determine the final extent of the problem. This paper develops the value of the sampling constant with respect to intrinsic heterogeneity based on data on observed Ochratoxin A (OTA) concentrations in individual wheat kernels. A useful relationship between the distribution of mycotoxin concentrations on a kernel to kernel basis and the distribution of concentration over subsamples is developed.

Jan 1, 2009

By D. S. van Vuuren

Industrial production of titanium occurs via the batch-wise reduction of titanium tetrachloride (TiCl4) with a reducing metal, being magnesium in the Kroll process, or sodium in the Hunter process. In the search for low cost titanium, the CSIR is developing a continuous process to produce titanium powder directly via metallothermic reduction of TiCl4 in molten salt, dubbed the CSIR-Ti process. The move to a continuous process has been attempted by a number of organizations, but was until now always met with failure, due in no small part to challenges inherent in the process chemistry. The reaction between TiCl4 and the reducing metal can occur directly, when TiCl4 or any titanium sub-chlorides present, comes into contact with suspended or dissolved reducing metal. The reaction can also occur indirectly, without any physical contact between the reacting species, via an electronically mediated mechanism. The reaction mechanism via electronic mediation can cause TiCl4 to react at the outlet of the feed port, rapidly causing blockages of the TiCl4 feed line. The electrical conductivity of the metal reactor can also cause the electronically mediated reaction to favour the formation of titanium sponge on the reactor walls and internals, rather than titanium powder. Various methods were investigated to overcome the problem of blockages in the TiCl4 feed line, e.g. mechanical removal, sonic velocities, dilution of the TiCl4 and the use of ceramic feed lines. This article discusses problems experienced with the continuous feeding of reagents, and various methods attempted are shown and discussed. Information is also given on the morphology, chemical composition and suitability of the final titanium powder for powder metallurgical application as presently produced by the CSIR-Ti process. Keywords Titanium dioxide, titanium nitride, carbo-thermic reduction, ilmenite, slag, tunnel kiln, residence time.

Jan 1, 2011

By D. Van Dyk

Horizontal rotating mills are being used all over the world in different mineral and power generation industries. David Brown South Africa, with over 140 years of experience in gear manufacture and design, has been supplying these industries with innovative designs at exceptional quality. The gearing systems associated with these industries are challenged daily with operating conditions that are not always fully understood. Failures are therefore experienced, over time in the industry, which cannot always be fully explained. David Brown South Africa has developed a gear monitoring system, the Intelligent Gearing System, in association with Transmission Dynamics (UK), in order to monitor and analyse these operating conditions in real time. The system has been designed on the principles of Six Sigma, incorporating Design for Six Sigma. The purpose with this system design is to monitor the operating conditions on the pinion, record the information and analyse the data in relation to the rate of fatigue damage to the girth gear and pinion. This is done in real time and unattended. The output from the Intelligent Gearing System can be fed back into the operating system of the mill user, in order to display an alarm for operating conditions exceeding the design criteria as well as information on the rate of fatigue damage due to these operating conditions. When the mill operating and the effect on the fatigue life of the mill gearing components, conditions are better understood, mill users can forecast critical spare holding levels with an increased accuracy. The Intelligent Gearing System also allows early actions to remove reasons for system overloads.

Jan 1, 2006

By L. Bam, R. Machaka, S. Chikosha, N. S. Muchavi

"Parts manufactured through power metallurgy (PM) typically contain pores that can be detrimental to the final mechanical properties. This paper explores the merits of 3D X-ray computed tomography over traditional microscopy for the characterization of the evolution of porosity in metal injection moulding (MIM) and direct powder rolling (DPR) products. 17-4 PH stainless steel (as-moulded, as-debound and sintered) dog-bone samples produced via MIM and Ti-HDH strips (as-rolled and sintered) produced via DPR and were analysed for porosity. 3D microfocus X-ray tomography (XCT) analysis on specimens from both processes revealed spatial variations in densities and the existence of characteristic moulding and roll compaction defects in agreement with traditional microscopic microstructural analysis. It was concluded that micro-focus XCT scanning can be used to study MIM and DPR parts for the characterization of the amount, position and distribution of porosity and other defects. However, the majority of the sub-micron sized pores could not be clearly resolved even at the highest possible instrument resolution. Higher-resolution scans such as nano-focus XCT could be utilized in order to fully study the porosity in MIM and DPR parts. IntroductionMetal injection moulding (MIM) is a novel process, which combines the advantages of powder metallurgy (PM) and plastic injection moulding. MIM has found widespread applications in the cost-effective production of high-sintered density small parts with complicated shapes and mechanical properties equivalent to those of wrought materials (German and Bose, 1977; Machaka and Chikwanda, 2015; German, 2013). There are four basic processing steps involved in MIM, namely; feedstock preparation, injection moulding, debinding and sintering. These steps are discussed in greater detail elsewhere (Machaka, Seerane and Chikwanda, 2014; German and Bose, 1977; Machaka and Chikwanda, 2015; German, 2013).Feedstock preparation involves mixing metal powder with a carefully selected composition of polymeric binder materials at a specific temperature. The feedstock is then granulated and injected into a predefined mould die with the desired shape. The part produced during the moulding step is referred to as a ‘green’ component. The green component typically contains no porosity since the spaces between adjacent powder particles are readily filled with the binder materials (German and Bose, 1977; Li, Li and Khalil, 2007). Debinding is the systemic removal of the binder components by chemical, catalytic, or/and thermal means while maintaining the shape of the component. The part produced after the debinding step is referred to as a ‘brown’ component. Debinding is known to be the source of porosity in brown components (Ji et al., 2001; Tsai and Cen, 1995). Finally, the brown debound part is sintered to full or nearfull density (Sotomayor, Varez and Levenfeld, 2010). The sintering step and associated densification closes up the majority of the pores. Sintered MIM parts are typically sintered to high density (95–99%) and retain an irreducible amount of residual porosity (Barriere, Liu and Gelin, 2003; German, 1990)."

Jan 1, 2016

Mill relining is a major contributor to overall plant downtime. Reducing the number of mill liner pieces removed from and replaced in the mill has a direct impact on the overall reline time and in turn, mill availability. To improve the mill availability of Ridgeway Operations' 32 foot SAG mill, a number of initiatives were implemented in terms of liner design. These included the conversion of the shell from 40 to 30 rows, reducing the number of pieces from 80 to 60 each shell reline and reducing the number of pieces from 48 to 32 per feed end reline. In addition, modifications were made to the discharge end of the mill to extend the life of the outer pulp lifter and discharge cone, thereby reducing the frequency of change out. The standard radial outer pulp lifter was converted to an angled design. The discharge cone was converted to the BullnoseTM design supplied by Bradken. This paper discusses the design changes made and the expected benefits to the Ridgeway Operations in terms of mill availability improvements.

Jan 1, 2007

By M. H. Moys, J. Engelbrecht, N. Terblanche

Interface levels in flotation columns are generally measured with the aid of a pressure-sensitive Instrument, e.g. a differential-pressure cell. This paper criticizes the use of this type of measurement, and discusses other methods that are claimed to give more accurate measures of interface levels. The paper focuses on the development of methods based on the measurement of conductivity across the froth-slurry interface. These are often sabotaged by variations in the conductivity of the feed slurry, particularly when the pH of the slurry IS being controlled, e.g. In sulphide flotation. Methods of improving the accuracy and reliability of this technique are described. The result IS a robust, easy-to maintain level-control scheme that successfully rejects large disturbances in plant operation (including a 5:1 change in slurry conductivity) while controlling levels to an accuracy of I 4 cm.

Jan 1, 1992

By J. McPherson

In order to add value to South Africa?s gold reserves AuTEK, a joint venture between Mintek and Anglogold-Ashanti, was started in 2000 with the aim of developing new industrial uses for gold. Accordingly gold catalysts are being made in kilogram quantities by Project AuTEK and sold toend users and other interested parties under the trade name AUROliteTM. Although these materials are optimized for use in CO oxidation applications, demonstration of appropriate activity, selectivity and durability in both liquid- and other gas-phase reactions has been shown1. The review below highlights the recent use of these materials, and other gold catalysts, in reactions of commercial interest.

Jan 1, 2009

By H. J. Le Roux, W. B. Drummond

1. INTRODUCTION We have a moral responsibility towards the world to reduce the harmful deposits we emit into the environment arising from beneficiation technologies. Industry has not willingly spent money to limit these emissions because it affected their profit margin with the end result of emitting harmful elements into the environment. Governments have thus rightly stepped in and enforced systematic reduction of these emissions through legislation. In the past beneficiation of sulphur bearing ores was typically done through hydro-metallurgical concentration, smelting, followed by Sulphur removal by converting processes like the Pierce Smith converter. The latter two processes emitted substantial quantities of Sulphur into the atmosphere. Spiralling costs and legislation have resulted in the quest to develop more efficient and environmentally friendly processes to achieve the same end results. New hydro-metallurgical processes like the ActiVox process has completely eliminated the pyro-metallurgical processes. Kansanshi are also operating a similar process. It however elicits other ground water and spillage pollution hazards and problems of it?s own. Various improvements has also been made to the pyro-metallurgical stages, examples being combined smelting and converting with the Noranda reactor, the Codelco CMT furnace, one step flash smelting/converting or the Mitsubishi continuous smelting, converting and slag cleaning process. The new converting processes are also normally enhanced using oxygen leading to higher SO2 gas strength with only a marginal increase in off-gas volume. These processes have led to better efficiencies and a more controlled environment that reduces pollution, but does not eliminate it completely. The fact that there are still more than 70 existing Pierce Smith converter plants throughout the world that needs to be replaced or upgraded at tremendous capital cost, means that we will have the environmental problems for some time to come. The need thus exists to cost effectively get these existing plants into a state where they meet the new environmental regulations, community and safety requirements. This paper will concentrate on just one aspect of this quest, i.e. reduction/removal of off-gasses emanating from the converting of non ferrous sulphur mattes to achieve higher or specialised grades of refined metals.

Jan 1, 2005

By E. Bakhtavar

There are many near-surface deposits with considerable vertical extent that have the potential to be mined by a combined method of open-pit and underground methods. In this regard, there is often a point called ?transition depth? where a decision has to be made whether to continue deepening the pit or change to underground methods. Recently, optimization of the transition from open-pit to underground operation has become an important challenge in mining engineering. Optimally, to model the transition problem on the basis of maximization of the profit from open-pit and underground mining, (0-1) integer programming has been used. In this method, block economic values of open-pit and underground methods should be imported to the transition model. A hypothetical example is presented in order to assess the model in detail.

Jan 1, 2012

By E. Van Der Lingen

Within the context of the overall gold market industrial demand plays an important role. Industrial demand for gold was 430 tonnes in 2008, approximately 12% of total end-user consumption. The dominant consuming industry in this market for gold remains the electronics sector, consuming an estimated 300 tonnes, primarily through the use of gold bonding wire for computer chips and plated contacts and connectors. Substantial demand also derives from dental applications, with other smaller industrial markets and decorative uses of the metal (non-jewellery) constituting the balance. In each market gold faces tough competition from alternative lower cost materials, such as silver and copper (electronics) and ceramics (dental). As well as the obvious benefits to the gold market resulting from this constant physical demand, there are an umber of additional positive factors concerning the use of gold in industrial applications: ?Price inelasticity: demand for gold from the major consuming industries has so far proven to be relatively robust in the face of significant increases in gold price. ??Stickiness?: the gold consumed by industrial uses tends not to return easily to the market (i.e. the demand is ?sticky?) because it is highly dispersed. ?Image: the beneficial environmental and medical applications of gold (e.g. gold used in the treatment of prostate cancer and in purification of contaminated water) are helpful to the positive image of gold. ?Added-value: new industrial uses for gold can create substantial added value in the supply chain, particularly in gold producing countries.

Jan 1, 2009

By I. Wigden

This paper discusses system integration and installation of High-Tec systems in underground mines. ABB has the capability to be a System Integrator and co-operates with partners in different areas of technology. Today it is difficult to find one Company that is responsible for the complete Automation System. The design of the system is also dependent on the caving procedure that is currently being used in mines. Most of the engineering must be done during the feasibility study and the design phase. Any mistakes made during these phases will be costly to rectify in the commissioning phase. The paper will also include a presentation of the benefit of using Automation in an Underground Mine, and the importance of integration with the people component. Most of the experience and discussions in this paper are from different technologies that have been developed in Scandinavia and adopted from LKAB in Kiruna. The author of this paper was responsible for the Automation projects in Kiruna Mine during1994 - 1999. These projects include: • Broadband communication of data, audio and compressed video in one data stream. • Control System for Haulage -1045m • Automation of Load Haulage and Dumping machines (LHD) • Control of Production Drilling Rigs from a Central Control Room.

Sep 1, 2001

By F. P. Greyling

The aspect of sustainability of ferroalloy processes has long been a serious matter for consideration in many of the world?s industrialized countries. A number of countries can be named where ferroalloy plants that were once flourishing, have all but disappeared. One of the most important factors playing a role in this type of occurrence is the cost and availability of quality raw materials. Given that all natural resources will be depleted with time, users are compelled to develop new processes that are sustainable in the changing environment. The DC arc smelting furnace is one such process that has proved itself, and has gained increasing popularity over the past two decades. This process, amongst other benefits, directly addresses the use of more readily available and more affordable raw materials in ferroalloy production. Since early in the new millennium, GLPS has been involved in various studies for different clients of furnaces for the production of ferroalloys. Two of these recent studies have culminated in the design, construction and commissioning of DC arc furnaces for the production of ferrochrome. One of these furnaces is a 10 MW unit at Mogale Alloys, and the other a 60 MW unit at the Middelburg plant of Samancor Chrome. This paper discusses the approach taken in the design and construction of these two furnaces, which, although varying significantly in size and capacity, are very similar in many other aspects of their design. Keywords Furnace, DC arc, and ferrochrome.

Jan 1, 2010