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By R. G. Diale, H. R. Chauke, T. M. Ledwaba, P. E. Ngoepe

FeCo alloys play an important role in soft magnetic materials with a wide range of technological applications due to their high saturation magnetization and Curie temperature. However, these alloys have low ductility at room temperature. The ductility can be improved by the ternary addition of elements such as V. A density functional theory supercell approach was used to generate B2 Fe50Co50-xVx (0 ≤ x ≤ 50) structures and the properties were evaluated at different atomic percentage compositions to determine the ductility at room temperature. The structures were fully optimized to obtain better equilibrium ground-state properties such as lattice parameters and thermodynamic properties for both binary and ternary systems. The stability of Fe50Co50- xVx was evaluated from the heats of formation, elastic properties, and phonon dispersion curves. Furthermore, magnetic strength was evaluated from magnetic moments. It was found that all structures are thermodynamically stable due to the negative heats of formation. The calculated Pugh’s ratio and Poisson’s ratio confirm that alloying with V effectively improved the ductility. It was also found that Fe50Co50-xVx showed a positive shear modulus for the entire concentration range investigated, in agreement with phonon dispersion curves. The ternary addition of V to the FeCo system resulted in reduced magnetic strength due to a decrease in magnetic moments. These findings reveal that B2 FeCo-V alloys can be used as components and actuators for the automotive industry.

Jun 10, 2024

Spiral concentrators are compact, cost-effective and generally efficient gravity concentration separators for a wide range of applications (for example: coal, beach sands, iron ore, chromite and tantalite). Large mineral processing plants consist of thousands of spiral concentrators resulting in large plant footprints (capital intensive) and the adjustment of splitters is time consuming, impractical and is in many cases neglected?high capacity (HC) spiral concentrators aim to address these shortcomings. As a result Exxaro Namakwa Sands is currently investigating high capacity spiral technology for the spiral circuit upgrade at the primary concentrator plants (PCPs). This article summarizes the rougher spiral performance evaluation that was conducted on different types of spiral concentrators (the traditional MG4 spiral concentrator and the high capacity (HC) spiral concentrator) under different feed conditions. In addition, the effect of slimes on the spiral concentrator performance was also investigated. Slimes rheology was linked to the poor concentrator performance at the higher slimes concentrations. The test campaign shows a sacrifice in recovery under design-feed conditions can be expected when using high capacity spiral concentrators in the rougher stage when compared to traditional spiral technology currently in use. Both spiral concentrators show a detrimental impact of slimes on the performance, but the high capacity spiral concentrator is more sensitive to the higher slimes conditions.

Jan 1, 2010

By J. Arzuúa, U. Castro-Filgueira, L. R. Alejano, F. Malan

"Pillar design for underground mining is typically done using empirical formulae or numerical modelling. Practical experience and recent literature, nevertheless, illustrate the shortcomings of these design approaches. Ongoing monitoring of pillars is therefore recommended to minimize the risk associated with these designs.In a mine where a large number of pillars are cut, different pillar strengths can be expected owing to variations in rock mass strength from area to area. This problem is compounded by the fact that in mining environments the pillars are not always cut according to the prescribed dimensions. Although the original design using either empirical methods or modelling may predict stable pillars, unstable pillars will be encountered in reality. Very conservative designs with large factors of safety may circumvent this problem, but this approach is uneconomical.A possible solution to localized stability problems may be to enhance the strength of a few unstable pillars. It may even be hypothesized that reinforcing a few critical pillars may prevent ‘pillar runs’ on a much larger scale. Rockbolting, strapping of pillars, and pillar shotcreting have occasionally been used in the past as possible solutions. It appears that these have not been successful in all cases and large collapses have occurred in spite of the pillar remedial work.The authors investigated the strapping of pillars by conducting laboratory tests on cabled rock specimens. The results were qualitatively compared to actual attempts of pillar reinforcement available in the literature, as well as additional observations in an old haematite roomand- pillar mine in Spain. Based on these results, the value of steel cabling and mesh wrapped around pillars to improve stability is demonstrated. Some cases where this approach will not be successful are also discussed."

Jan 1, 2017

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

A Colloquium and General Meeting was held jointly with the Mine Ventilation Society of S.A. in Kelvin House, Johannesburg, on 17th November, 1971, the theme being "The Economics of Mine Ventilation". Professor D. Howat (President) was in the chair. The Colloquium was attended by 150 delegates and was opened by the President at 9.00 a.m. MEMBERSHIP The President: "I have much pleasure in announcing that the names of the candidates, having been published in accordance with By-Law 5.2.2, Council has elected them to membership of the Institute in the following Grades: Fellows: Frederich-Wilhelm Volk, Peter Bennet Columbine. Members: Allan Colin Lawrence, Karel Anton van Gessel, Christopher Robert Harrison, Christopher Michael George Wartley, Frank Heinrich Deist, Ralph Morris, Benjamin Johannes Nolte. Associates: Wolf gang Freidrich Gottsman. TRANSFERS From Member to Fellow: Hugh Edward Keith Alien. From Graduate to Member: Errol Vincent Bosman, Christopher Roderick Stewart Needes, Bernard Wessels Holthousen. From Student to Graduate: David Robert Fleming. I welcome the new members to the Institute and congratulate them on their election. CO-OPTION TO COUNCIL The President announced that at the Council meeting held on 5th October, 1971, it was agreed, in terms of Rule 3.9 to co-opt Dr T. B. Beeton to Council. COLLOQUIUM The President welcomed visitors and members. He stressed that the discussion would be informal and that any contributor requiring publication should submit his contribution in writing. He then thanked the authors for providing pre-prints of the papers. After the President had concluded his opening remarks, he asked Professor J. de V. Lambrechts to act as Colloquium Chairman for the day and he, in turn, introduced the three Session Chairmen namely, Dr A. Whillier (Chamber of Mines and President of the Mine Ventilation Society); Mr M. Barcza (Managing Director, Corner House Laboratories); and Mr L. W. P. v.d. Bosch (Chief Consulting Engineer, Union Corporation). The following papers were presented: "Fan efficiency investigation on mines of the Union Corporation, Ltd." by J. A. Drummond. Published in the Journal Feb. 1972. "The design of underground cooling towers" by A. Whilliel'. Published in the Journal, Oct. 1971. "Some aspects of the design of cooling plant installations" by R. Hemp. Published in the Journal, Nov. 1971. "The planning of ventilation and refrigeration requirements in deep mines" by D. F. H. Grave and R. M. Stroh. Published in the Journal, Dec. 1971. "Cooling power of underground environments" by D. Mitchell and A. Whillier. Published in the Journal, Oct. 1971. At the conclusion of the three technical sessions the Symposium Chairman commented as follows, indicating that he would prepare a written summing up at a later stage: "The tone of the colloquium has had a sincerely practical note about it. It would have been a pity if the ventilation experts talked only theory and little practice. This practical theme has, I am sure, made the colloquium interesting to both ventilation men and others whose daily tasks do not touch so closely on this fascinating subject. This practical theme was in evidence through all the papers and contributions. Some of you may have felt that there was not enough emphasis on the word 'economics' as advertised in the broad title of the colloquium. I do not think this was really a valid criticism because as someone said 'it all boils down to Rands in the end!' So whether it was a case of low fan efficiency, poor design of cooling towers, wrong planning or low human efficiency due to high heat stress. . . it all boils down to money saving and therefore economics, whenever improvements are forthcoming. The title of the colloquium was thus not misplaced. The views of senior mining men on the production side are appreciated. Let us say that this exchange of views between ventilation engineers and those who have to take the final decisions and spend the money, should prove to be most rewarding." Professor Lambrechts finally thanked the Session Chairmen and everybody who had helped to make the colloquium a success and the meeting closed at 4.0 p.m. In a subsequent written summing up, the Colloquium Chairman gave the following as his impressions of some of the highlights which emerged from the papers and discussion thereof: (The names indicate the authors only). Drummond: It was hinted that the time had arrived to consider the introduction of a South African fan test code which would be better suited to local conditions than the currently acknowledged B.S.S. code which, however, is seldom enforceable in practice. In this connection also, there was prominent reference to the thermodynamic approach of McPherson. Wide variations in the quality of maintenance of, and repair work on, fans were stressed. It was mooted that ventilation engineers responsible for estimating the basic duty specifications for large fans, frequently played safe by overestimating the pressure required, thus ensuring that there would not be a shortfall in air volume delivered. This usually meant reduced fan efficiency and it was suggested that decision makers seemed to lay more emphasis on volume of air delivered than on real eco-

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

By K. Koruyan

Although remote sensing technology has been available for many years, it has rarely been used for monitoring mining activity. Recent studies indicate that remote sensing is also a valuable tool for managing and planning certain aspects of the mining operation. In this paper, we examine areal expansion of marble quarries and the affected vegetation over a period of 10 years in the Mugla region in Turkey, using geographic information system (GIS) and remote sensing (RS) techniques. Images captured by ASTER Level 3A01 (3D Ortho Data Set), Landsat 5, and Landsat 7 satellites between 2001 and 2009 were used for the analysis. Changes in the natural vegetation as a function of the production level in the marble quarry were calculated using the normalized difference vegetation index. According to the study results, land cover and natural vegetation decreased by less than 3 per cent and 1 per cent respectively between 2001 and 2009, following an upsurge in mining activity in the region.

Jan 1, 2012

By J. N. Van der Merwe

"Platinum is a highly valuable resource, its safe and economic extraction is paramount. The success of platinum mining by the bord and pillar method depends heavily on a comprehensive and dependable pillar design method. Pillars need to be large enough to safely support the load and small enough to avoid loss of resources. A critical evaluation of current pillar design systems used in narrow-reef platinum mining was undertaken using practical experience from a large feasibility-stage platinum exploration project, supplemented by observations from several platinum mines in Zimbabwe. An extensive literature survey was undertaken in order to determine the current status of design systems. Through this approach, the shortcomings of current pillar design systems are highlighted. Areas are proposed for further research to obtain a better understanding on how additional factors influence pillar system stability. The exploration work highlighted how rock mass classification methods can be utilized in determining the overall strength of pillars. Current pillar design systems for narrow-reef platinum mining consider width-to-heightratio (usually with different exponents for width and height) and the strength of the pillar material. However, there are many more important factors that are not considered and which have a bearing on pillar system stability. An in-depth study of these parameters with a view to establish effective narrow- reef platinum mining pillar design systems needs to be undertaken. IntroductionPillars have been used as a means of support since the early days of mining. Pillarsupported mining methods such as bord and pillar require a reliable design system for them to be successful. This paper presents an evaluation of the current hard-rock mining pillar design systems as applied to a practical large-scale narrow-reef platinum mining feasibility study. It is vital to have a dependable pillar design system for economic and sustainable mining. Using an extensive database collected from the project, the pillar strength formulae were tested and several discrepancies noted. This necessitates the establishment of more reliable pillar design systems. In narrow-reef platinum mining, large compressive stresses accompanied by geological and geotechnical factors contribute to pillar instability. A well-formulated pillar design system is required that accounts for such factors so as to minimize pillar failures."

Jan 1, 2017

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 Bjørn Nilsen, Brian J. Ballou

The Tellnes open pit mine in Southwestern Norway has been operating since 1960. The maximum height of pit walls is currently about 150 meters with the current mine plan extending this distance to 400 meters with slope stability being a major controlling factor. As a result of unfavorable combinations of directions of major joints and faults, local stability problems have occurred several places in the pits walls. Stability problems have affected the reliability of main transport roads on several occasions. Most of such incidents have occurred during heavy rainstorms and during periods of repeated freezing/thawing. This paper reviews some of the stability problems and the measures taken to deal with such stability problems.

Jan 1, 2006

Mixed integer programming (MIP) has been used for optimizing production schedules of mines since the 1960s. The major problem in the long-term production scheduling for an entire orebody is that the number of integer variables needed to formulate an MIP model is too large to solve the formulation. This number may reach well over one hundred thousand. To overcome this difficulty, this paper presents two new algorithms to reduce the size of the problem. These algorithms assign an earliest and latest possible start date for each machine placement, eliminating the integer variables that correspond to machine placement before its early start date and after its late start date. A case study based on Kiruna Mine, the second largest underground mine in the world, is summarized in the paper. It shows substantial improvement in the solution time required using the new algorithms. This increased efficiency in the solution time of the MIP model allows it to be applied to Kiruna Mine, with the potential to increase substantially the net present value (NPV) of the project.

Jan 1, 2008

By P. A. Roberts

A modified in situ leaching method for extracting gold from oxidized gold ores using a non cyanide lixiviant is proposed. A non cyanide lixiviant is suggested because of the obvious concerns posed by injecting cyanide bearing solutions into the subsurface. Oxidized gold ores are the initial focus because earlier research on the use of sodium thiosulphate as a lixiviant under anaerobic conditions indicated that the presence of pyrite led to rapid thiosulphate breakdown. A reconnaissance research programme, involving ore characterization and hydrometallurgical testwork on samples from four Australian ore deposits and preliminary reactive transport modelling studies was carried out. This work showed that lixiviant-oxidant combinations of sodium thiosulphate and ferric EDTA, and iodide and iodine are both capable of extracting high percentages of accessible gold from the selected samples under anaerobic conditions. The ore characterization and reactive transport studies, suggested that both physical and chemical methods of permeability enhancement may be required to lift bulk permeability and the availability of gold for dissolution to sufficiently high levels to obtain adequate gold recoveries. Physical permeability enhancement could be achieved by blasting and/or hydraulic fracturing of the ore. Assuming that such methods prove to be both necessary and economically viable, the mining method would no longer be regarded as simple in situ leaching. Therefore, the term ?in place leaching? has been adopted for the proposed gold extraction system

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

Council for 1998/99 President R.P. Mohring President Elect J.R. Dixon Vice Presidents Senior M.H. Rogers Junior Dr L.A. Cramer Immediate Past President Dr N.A. Barcza Honorary Treasure J.A. Cruise Members of Council J.P.W. Bennie E.G. de Villiers A.A.B. Douglas F.M.G. Egerton R. Graham Dr R.G. Gürtunca Dr R.V.R. Handfield-Jones P.J. Knottenbelt R.G.B. Pickering* P.S. Piper Prof. R.F. Sandenbergh Dr T.R. Stacey D.J. van Niekerk P.J. Venter J.C. Viljoen

Jan 1, 1998

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 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 Thermo Electron, Tim Sennett

Summary ?SamStat Development ?SamStat Description ?Accuracy ?Availability ?Cost of ownership ?Capital ?Installation ?Operating/Maintenance ?Case Studies ?Modikwa ?Combined concentrate sampling ?Cerro Verde ?State of the art sampling & analysis ?Ok Tedi Final Tails ?brownfields installation ?Conclusion

Jan 1, 2005

By M. Gao

The Zinifex Century Mine employs a large number of Detritor mills for fine and ultra-fine grinding to liberate silica and sphalerite at 80 per cent passing 7.5 microns before final zinc flotation. A joint project between CSIRO Minerals and the Zinifex Century Mine was carried out to evaluate the Detritor mill performance. Plant surveys were conducted around the Detritors in conjunction with laboratory tests. The survey data showed that the Detritors in the ultra-fine milling circuit performed well. They reduced a feed F80 sizing of 46 microns to a product P80 sizing of 7.5 microns at a gross energy consumption of 37.2 kWh/t. Scale-up of ultra-fine milling Detritors was studied using a 0.55 kW laboratory batch unit and a 355 kW full-scale Detritor by processing Century zinc concentrate with 1 mm sand media. The results indicated that the 0.55 kW laboratory mill underestimated the energy consumption of the full-scale Detritor by about 20 per cent for a product P80 of seven microns. The performances of a horizontal IsaMill and a vertical Detritor were compared as ultra-fine milling devices for processing Century zinc concentrate. The experimental data demonstrated that, when using the same grinding media, the energy efficiency of the two mills is similar despite the difference in mill designs. The Detritors used for regrind duty at the Century Mine performed poorly when processing feed at 80 per cent passing 88 micron. The energy consumption was high and the product size distribution was broad with particles above 100 microns in the feed unbroken and particles below ten microns overground. A coarser ceramic media of 3 mm was therefore tested in a laboratory Detritor to process the regrind Detritor feed as an alternative to the 1 mm Colorado sand used at the Century Mine. The ceramic media reduced the energy consumption significantly and produced a narrower product size distribution, which is more desirable for the downstream flotation process.

Jan 1, 2007

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

The Skorpion process comprises three processing steps-atmospheric leaching in sulfuric acid, zinc solvent extraction and electrowinning to produce special high grade zinc. The major mode of impurity transfer was attributed to crud runs in the solvent extraction circuit. Crud may be described as a heterogeneous, partly inorganic, partly organic mass of material which accumulates predominantly at the interface between organic and aqueous solutions. The paper describes the root causes of the crud formation in the solvent extraction circuit and optimization strategies which are being followed to prevent impurity excursions in electrowinning. Keywords: zinc oxide, solvent extraction, crud formation, colloidal silica.

Jan 1, 2007