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By R. J. Davidson

Arguments are presented in favour of a new interpretation of the chemistry pertaining to the dissolution of gold, when this takes place in typical gold plant leach circuits where calcium is present in solution. It is suggested that under these conditions the standard chemistry, as it applies in the absence of calcium, is no longer valid. Thus the concept of very soluble sodium and aurocyanide ionic species in solution is replaced by the presence of weakly soluble calcium aurocyanide, which is a covalent coordination complex that is non-ionic. Supporting evidence for this is provided and the implications that the presence of calcium in gold plant circuits may have for operational efficiency are discussed. In particular, because of the formation of this weakly soluble calcium complex, the addition of lime to the leach circuit is questioned. Arguments for the use of a sodium hydroxide/sodium carbonate/sodium bicarbonate buffer solution as a means of controlling pH and of increasing ionic strength in a so-called ?soft? leach are presented. Such a lime-free system, besides benefiting the leaching of gold, would have many downstream benefits in existing CIP circuits. Furthermore, the direct electrowinning of gold from the leach now becomes potentially feasible.

Jan 1, 2007

By J. Rogans

This paper discusses the comparative performances of the three activated carbon adsorption circuits at the West Wits operations of Anglogold. These circuits consist of two pump-cell circuits (at Two Plant, formerly Elandsrand and at Three plant) and a conventional counter-current adsorption circuit (at Mponeng plant). The implications of the improved performance of the pump-cell plants are discussed.

Jan 1, 2002

By Sverre Olsen, Kai Tang

The composition of ferromanganese slag is very important as it determines the slag/metal equilibrium relations including MnO content of final slag, melting relations and slag viscosity. The slag composition is further expected to influence the process temperature. The properties of ferromanganese slags are suitably described by its basicity and A/S mass ratios. The influence of slag basicity has been discussed in the previous papers. The present paper will discuss the effect of Al2O3 on melting relations, viscosity and MnO-content of final slag. This discussion will be based on assessed thermochemical databases and a recently developed viscosity model.

Jan 1, 2007

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

A running facebreak ahead of the powered support units occurred on the number 4 seam at Matla Coal’s number 3 shaft (Matla 3) in April and May 2002.Very difficult mining conditions were experienced for a distance of some 150 m in the tailgate and to a lesser extent on the face itself. The paper analyses the main causes for the high stress conditions leading to the facebreak, namely, the existence of a >20 m dolerite sill close to surface and the effect of stopping longwalling on the overlying 5 seam. Difficulties experienced during the facebreak are discussed, including, pillar and roof collapses in the tailgate, high stress areas ahead of the face causing roof and sidewall stability problems, flushing of broken rock into the face area at the tailgate, secondary mid-face breaks, and the availability of critical support units. Successful rock engineering interventions and learning points were that, a goaf angle of 14.6° was found to be more realistic than the previously used 20 to 25° in predicting dolerite sill behaviour in this area, pre-split blasting of the sill significantly reduced stress on the face and tailgate allowing re-support work to proceed, varying pillar support types were analysed and rated, the need to always have a ground control “First Aid” kit available was recognised and a strategy for subsequent panels beneath the sill was developed. Numerous support units were used and the performance of the more suitable types is briefly discussed. A running facebreak ahead of the powered support units occurred on the number 4 seam at Matla Coal’s number 3 shaft (Matla 3) in April and May 2002.Very difficult mining conditions were experienced for a distance of some 150 m in the tailgate and to a lesser extent on the face itself. The paper analyses the main causes for the high stress conditions leading to the facebreak, namely, the existence of a >20 m dolerite sill close to surface and the effect of stopping longwalling on the overlying 5 seam. Difficulties experienced during the facebreak are discussed, including, pillar and roof collapses in the tailgate, high stress areas ahead of the face causing roof and sidewall stability problems, flushing of broken rock into the face area at the tailgate, secondary mid-face breaks, and the availability of critical support units. Successful rock engineering interventions and learning points were that, a goaf angle of 14.6° was found to be more realistic than the previously used 20 to 25° in predicting dolerite sill behaviour in this area, pre-split blasting of the sill significantly reduced stress on the face and tailgate allowing re-support work to proceed, varying pillar support types were analysed and rated, the need to always have a ground control “First Aid” kit available was recognised and a strategy for subsequent panels beneath the sill was developed. Numerous support units were used and the performance of the more suitable types is briefly discussed. Une cassure de taille en avant des unités de soutènement s’est produise sur la veine numéro 4 dans le puits numéro 3 (Matla 3) de la mine Matla Coal en avril et mai 2002. Les conditions d’extraction étaient extrêmement difficiles sur une distance d’environ 150 m dans la voie de tête et, en moindre mesure, sur le front de taille lui-même. L’étude présente analyse les raison majeures pour les conditions de grandes contraintes qui ont conduit à la cassure de taille, à savoir l’existence d’un mur de dolérite de >20m proche de la surface et l’effet d’arrêter la longue taille sur la veine 5 superposée. Les difficultés rencontrées pendant la cassure de taille sont rapportées, y compris les effondrements de piliers et toit dans la voie de tête, les aires de grandes contraintes en avant du front de taille causant des problèmes de stabilité pour le toit et les parois latérales, l’injection de roches cassées dans la taille en voie de tête, les cassures secondaires à mi-taille, et la disponibilité d’unités de soutènement critiques. Interventions minières réussies et leçons apprises furent : un angle de remblai de 14.6° était plus réaliste que celui de 20 à 25° utilisé auparavant pour prédire la conduite du mur de dolérite dans cet endroit ; tir à deux temps du mur a réduit considérablement les contraintes sur la taille et la voie de tête, ce qui a permis un travail de support complémentaire ; des types variés de support de piliers furent analysés et évalués ; la nécessité d’avoir toujours une trousse de première urgence disponible fut reconnue ; et finalement une stratégie pour les panneaux en dessous du mur fut

Jan 1, 2003

By L. A. Cornish, L. H. Chown, M. Matema, R. Süss, L. Glaner, A. Douglas

Mintek has been developing Pt-based alloys for high temperature applications in aggressive environments, for example, land-based turbine engines, to replace the currently used nickel-based superalloys (NBSAs). The Pt-based alloys have a similar structure to the NBSAs, and since Pt is more chemically inert and has a higher melting point, the Pt-based alloys can potentially be used at higher temperatures. The greater chemical inertness of the Pt-based alloys compared to the NBSAs means that coatings can be simpler, or perhaps not even used at all, depending on the environment. TEM work was done at NIMS, Japan, to investigate the changes in the microstructure o f Pt-Al and Pt-Al-Ir alloys at elevated temperatures using in-situheating up to1100°C. Initial casting trials showed that work needs to be done to optimise casting parameters before commercialisation can take place. Room temperature tensile tests were performed and results were variable mainly due to microstructural differences. The alloy hardnesses were in the order of 300-350HV with ultimate tensile strengths of ~800 MPa and elongations of less than 10%. These results are comparable to other alloys used at high temperatures, which is very encouraging. Keywords: platinum, super alloys, hardness, tensile

Jan 1, 2006

By S. Ganguly

Slag samples taken from adjacent to the furnace wall of a submerged arc ferromanganese smelting furnace have been found to contain high concentrations of K2O. To characterize the phase equilibria relevant to these slags experimental studies have been carried out to determine pseudo-ternary sections of the form ?MnO?-CaO-(SiO2+Al2O3) with a fixed Al2O3/SiO2 weight ratio of 0.65 and 6.0 wt% K2O for temperatures in the range 1523-1673 K. In the pseudo-ternary section investigated the primary phase fields are found to be mullite, 3Al2O3?2SiO2; corundum, Al2O3; spinel, MnO?Al2O3; manganosite solid solution, (Mn,Ca)O; dicalcium silicate,2CaO?SiO2; gehlenite 2CaO?Al2O3?SiO2; anorthite CaO?Al2O3?2SiO2; kalsilite KAlSiO4 and leuciteKAlSi2O6. It was found that the presence of K2O in the slag decreases liquidus temperature in the anorthite and gehlenite primary phase fields. The manganosite primary phase field is expanded in the direction of increased (Al2O3+SiO2) and the liquidus temperatures in the manganosite primary phase field are increased significantly with the presence of K2O in the slag.

Jan 1, 2007

By S. H. Badenhorst

Zacharias Lewala discovered a diamond at Grasplatz, near Lüderitz in April 1908. While this stone may not have been the first diamond to be found in this barren, inhospitable area, it most certainly was the stone that set off a chain reaction ultimately leading to the creation of Namdeb as we know it today. [ ]

Jan 1, 2003

By M J. Van Der Merwe

The mining industry is facing a serious skills resource shortage, growing commodity demand and cyclical prices. This makes focus and allocation of resources in the early stages of project development very important. To assist with these six key elements in the project prioritization process is proposed, namely: 1) Define the project vision, objectives and business case, 2) Determine the potential show stoppers, 3) Determine the key value drivers, 4) Track changes and provide regular feedback, 5) Evaluate the alternatives and, 6) Ensure proper gate management governance at the decision point. Incorporating these elements in the project development process will assist in resource allocation and focus on the high value aspects of projects and alternatives during the early stages of the project development lifecycle. Keywords: Resource allocation and focus, vision, show stoppers, value drivers, project prioritization, linear programming, business case modelling, management decision.

Jan 1, 2008

By F. T. Cawood

This paper focuses on the role of the coal mine surveyor at the start of the 21st century. It demonstrates that surveyors must look beyond their legal appointment and pursue opportunities to add value at an operational or corporate level of the company. It also exposes the shortfall of statutory appointments in defining the surveyor?s role in terms of key business drivers of the company. One such an opportunity is the potential role of the surveyor in mineral accounting and quality assurance to meet mine requirements, market specifications and standards pertaining to corporate governance and reporting. Finally, some thoughts are expressed on what can be done to elevate current practice to best practice and how to achieve this goal

Jan 1, 2007

By O. Celep, T. Uslu, Savas

This study investigates the enrichment of a low-grade colemanite concentrate (-3 mm) using a Knelson centrifugal gravity concentrator. Due to its low boron content, the concentrate is unsaleable and has to be stored under appropriate conditions to avoid potential environmental problems. The low-grade colemanite concentrate was comminuted to size fractions of-1 mm, -0.5 mm, and -0.15 mm before treatment in the Knelson Concentrator. The effects of particle size, fluidizing water velocity, and bowl speed on the enrichment process were examined. The B2O3content of the concentrate was increased from 33.96% to a maximum of 45.52%. B2O3recovery increased with increasing bowl speed and particle size, and decreased with increasing fluidizing water velocity. The enrichment process also rejected arsenic and iron to some extent, with a maximum reduction of arsenic from 1360 g/t to 765 g/t and iron from 0.88% to0.33%.

Jan 1, 2015

By C. M. Rule

Energy efficiency is currently a significant area of interest due to the Eskom power situation, which led to severe power impacts to the PGM, and indeed whole SA primary industries, in early 2008. Anglo Platinum has focused on energy efficiency for a number of years, especially in the concentrator operational area. New comminution technologies have been aggressively developed, which have shown real metallurgical efficiency gains as well as significant energy efficiency and saving potential for Anglo Platinum?s total electrical consumption as the company expands into a growing PGM demand market. This paper illustrates this programme?s activities, potential and considerable achievements to date.

Jan 1, 2009

By M. -O. Suk, S. -K. Jo, S. -C. Shim, J. T. Kim, S. -H. Kim, C. -W. Seo, J. -S. Kim

An equilibrium study was carried out at 1873 K to ascertain the effect of carbon in CaO-SiO2-Al2O3-MgO-MnO-FetO slag systems on their FetO and MnO activity coefficients, representing the slag?s thermodynamic potential for steel reoxidation. Both ?FetOand ?MnO showed not only a sharp increment, but also a simultaneous slow decrement by increasing carbon content in slag, suggesting opposite roles of the carbon according to its stable forms. XPS (X-ray photoelectron spectroscopy) was introduced to clarify the stable forms of carbon in slag. XPS results prove that carbon dissolves in slag as carbonate, and carbide ions under oxidizing and reducing atmospheres, respectively. It was concluded that carbonate ions increase ?FetOand ?MnO, and that carbide decreases them. This paper suggests an application method of the present results to actual ladle refining processes, in order to enhance steel cleanliness without decreasing (FetO + MnO) content in slag. Keywords: carbon, slag, activity coefficient, FetO, MnO, carbonate, carbide, XPS, reoxidation, cleanliness

Jan 1, 2004

By J. Kraemer, A. Preusse

In the federal state of North Rhine Westphalia (Germany) small and medium sized companies are beginning to extract the related gas via old shafts or boreholes and to use it as a source for the production of electricity and heat. More than 100 applications for the separate mining right on mine gas had already been filed by beginning of 2002, since mine gas is treated as a mineral resource under the Federal Mining Law. Meanwhile more than 40 mine gas concessions have been granted and first projects are being developed with encouraging results so far. To enhance the applied techniques and their efficiency Aachen University has formed a research team in this discipline. Scope and goals of this research activities are being presented in this paper. Keywords: extraction mine gas, Renewable Energy Act, Ruhr District.

Jan 1, 2003

By F. T. Cawood

Inauguration of the new political dispensation in South Africa in1994 initiated a dynamic shift in the ownership, management and development of the country?s affluent mineral heritage. The process of substituting the old South African regime with a new equitable system started soon after the 1994 election of the African National Congress (ANC) to parliament. The Congress?s Freedom Charter revealed the intent of the new dispensation when it called for radical transformation of mineral development. However, since then there have been important changes affecting the rules of mineral development. These are: ?A drastic change in politics ushered in by negotiation, a spirit of reconciliation and a desire to settle disputes peacefully ?The globalization of the South African mining industry in tandem with the opening of domestic mineral resources to foreign capitalists and ?The introduction of sustainable development as a holistic approach to mineral development in order to replace traditional narrow-minded environmental management. Each of these significantly shaped the new mineral investment environment of South Africa. This paper represents a summary of the historical developments leading to the current Mineral and Petroleum Resources Development Act No. 28 of 2002, its regulations, the much publicised Broad-Based Socio-Economic Empowerment Charter, its associated Scorecard, and the Draft Royalty Bill.

Jan 1, 2004

By A. McLean, M. Iwase, K. Wakimoto, K. Katogi, Y. Kikuchi

One of the greatest obstacles to the application of physical chemistry principles to the elucidation of slag-metal reactions is a lack of knowledge of activities of the reacting species. To a large extent, oxygen potential of the slag phase governs iron and steelmaking practice. Without oxygen control by means of appropriate sensors, the behaviour of the other elements cannot be managed. In this paper, measurements of the FeO activity with various types of electrochemical FeO sensors will be described together with examples of their applications for improved strategies toward better practice for ladle metallurgy and sulphur and manganese distributions between slag and metal phases during steelmaking. Measurements of FeO activity have also been made in order to improve dephosphorization reactions. This type of work has led to significant reduction in volume of slag generated within the steelmaking vessel, which in turn has important implications for refractory wear, metal yield, alloy recovery and improved productivity. Finally, an on-line sensor is described that permits the oxygen potential to be determined for both the metal phase and the slag phase during steelmaking in the BOF.

Jan 1, 2004

By R. G. B. Pickering

The purpose of this report is to chronicle the interaction between Anglo Platinum and Sandvik Tamrock during the development and application of Long Hole drilling as a viable, practical method of narrow reef mining. Appendix I identifies the people from Anglo Platinum and Sandvik Tamrock who participated in the project. Experiments in long hole drilling and blasting were conducted in a number of mines during the late 1950s and early 1960s. Some of the advantages envisaged were: ? The face would require no daily examination ? No barring down or immediate face support required ? No sockets to clean ? Only a few well drilled holes rather than large numbers of short blast holes ? Avoidance of poorly-marked holes, inaccurate drilling and improper charging ? Better supervision and better face advance. Holes 50 mm in diameter were drilled parallel to the stope face by pneumatic rock drills from advance strike gullies. Holes were charged with amon gelignite cartridges. All holes were traced with detonating cord to ensure propagation of the explosive along the entire hole length. Rock was blasted onto a rolling scatter pile. A number of reasons have been cited for the failure of this mining method. The two most important were: ? problems in controlling hole deviation which was exacerbated by the fractured ground ? difficulty of charging up holes in fractured ground, due to relative movement of rocks along fracture surfaces over the hole length. The idea of drilling a few long holes parallel to the face rather than a large number of short blast holes perpendicular to the face was an attractive option to mechanize narrow reef mining. This particular project started in 1998. Initial trial The Union Section of Anglo Platinum purchased a Solo H 606 RA long hole drilling rig from Sandvik Tamrock in 1997. In order to evaluate long hole drilling as a basis for face mechanization. The Solo series of drill rig was selected because it combines high drilling performance and good drilling accuracy with high versatility with a compact size. The mining method proposed by a consultant to Anglo Platinum was based on the current trackless mining method practised by Union Section. The trackless mining method is better described as a trackless development and transport method. Reef strike drives were installed approximately 40 metres apart on dip using trackless equipment. Reef was mined using hand-held pneumatic rock drills and scraper winches and the excavation was supported by sticks and crush pillars at the top of the panel. Rock scraped from the panel was loaded by Lad Haul Dumps (LHDs), trammed to an inclined haulage, and loaded into trucks for transport to the surface. It was intended that the Solo would drill from the bottom advance strike drive to the top advance strike drive. Blasted rock would still have to be scraped from the panel. It is also difficult to understand how well the support would have survived. In the initial motivation it was stated that drilling accuracy was of the utmost importance. Previous work by Sandvik Tamrock had shown that, in other parts of the world, 20 metre long holes could be drilled with a deviation not exceeding 100 mm provided that: ? holes were collared with low thrust pressure ? operating percussion pressure was kept low -often not ? exceeding 10 MPa ? drilling was to be with tubes, not rods. In early 1998 initial trials with the Solo H 606 RA were inconclusive; attempts were made to drill 40 metre long holes from one advance strike drive to another. Difficulty was experienced in measuring hole straightness and accuracy, there was no survey of the holes, and no blasting was done to expose hole barrels. A long hole mining system was then defined, with a corresponding face mining system, which led to the design of a test programme for the Solo drilling rig. Earlier experience at Telfer The proposed face mining system was based on a mining method that is practised at Telfer Gold Mine in Western Australia. Telfer has a series of domed reefs that dip at angles of less than 20° to more than 40°. The ore bodies are all thin, with widths from 0.6 metres to 0.8 metres. Figure 1 shows the face layout. Experience at Telfer indicated the following: ? The spacing and size of the dip pillars should be based on the rock mechanics of Union Section ? The length of the face is determined by the ability to correctly position the blast holes. Positioning of blast holes is a function of hole straightness and hole direction. Blast holes in Telfer were drilled 64 mm diameter with retrac bits from Sandvik. Extension steel was T38 by 1.8 metre lengths. A guide rod was fitted immediately behind the bit. To achieve greater accuracy' operators drill at relatively low percussion and thrust pressures. Results show that very good accuracy is achieved in 20 metre stopes and only fair accuracy in longer stopes. In 34 metre long stopes 10-15% of the holes are not sufficiently accurately positioned and have to be re-drilled. All blast holes are

Jan 1, 2006

By Org de Wet

This paper summarises the strategy for selection between a two module coal plant incorporating large, but less equipment, and a three module coal plant with more but smaller equipment. The two options were evaluated in terms of three main categories: ? Size ? size of the equipment and the effect on the process efficiency as well as the difference in physical dimensions of the plant to accommodate the larger equipment; ? Cost ? capital savings between a two and a three module plant, processing the same ROM (run-of-mine) tons per hour (t/hr); and ? Practicality ? in terms of constructability of the plant, safety of using larger equipment and maintainability of the equipment. Decisions that were taken to reduce the risk associated with size, cost and practicality on the chosen option of a two module plant will be highlighted.

Jan 1, 2006

By G. A. Bezuidenhout, J. P. T. Kapusta, D. K. Chibwe

"Peirce-Smith converters (PSCs) are extensively used in the copper, nickel, and platinum group metals industries. The typical converting operation involves lateral purging of air into molten matte through a bank of tuyeres. This blowing operation occurs at low pressure from the blowers, resulting in a bubbling regime that is considered inefficient from both a process and an energy utilization perspective. Inherent drawbacks also include recurrent tuyere blockage, tuyere punching, and low oxygen efficiency.Western Platinum embarked on a full-scale industrial evaluation of generating a jetting regime by using sonic injection. Prior to industrialscale tests, a numerical assessment to ascertain the feasibility of implementing sonic injection into a PSC was conducted. The work included flow characterization at high-pressure injection achieving sonic velocity at the tuyere exit. The 2D and 3D simulations of the three-phase system were carried out using the volume of fluid method together with the RKE turbulence model to account for the multiphase and turbulent nature of the flow.This paper discusses the key findings in understanding plume extension, velocity distribution, shear wall stress analysis, and phase distribution characteristics in the system. Plant trials are also discussed with reference to the commercial aspects of a full-scale implementation of sonic injection in the smelter."

Jan 1, 2015

By H. Krogerus, P. Niemelä, P. Oikarinen

High carbon ferrochromium is produced by carbon reduction. No replacement for carbon as reductant has yet been developed. The reduction creates a considerable amount of CO-gas. In open and semi-closed furnaces the gas is burned when leaving the burden. In closed furnaces the formed gas is sucked out by a fan, washed and utilised as fuel. The formation of carbon monoxide is presented briefly starting from thermodynamic considerations up to solid and liquid state reduction. The volume, composition and energy content of the furnace gas are discussed, focusing on the raw materials and pre-treatment processes of the furnace feed as well as on the process equipment and control. Outokumpu has been using closed and sealed furnaces and utilising the CO-gas in its Tornio Ferrochrome Works since 1968. Today in Tornio with an annual ferrochromium production of 260 000 t CO-gas production is 186 million m3, representing 68 MWh an hour. At the same time the furnace power input is 95MW. About 98 % of the CO-gas is utilised, whereof 30% in the ferrochrome production itself. This paper focuses on the characteristics and utilisation of CO-gas. CO-gas is secondary energy, which on one hand saves primary electric and fossil fuel energy in ferrochromium production and, on the other, replaces other fossil fuels at the adjacent steel works. The characteristics of the fuel, requirements for utilisation as well as health and safety aspects are discussed. Utilisation of the gas has a high impact on the total dust and gaseous emissions and on the energy optimisation at the ferrochromium and steel works.

Jan 1, 2004

By J. H. Zietsman

It has previously been observed that industrial high-titania slags display a compositional invariance, remaining close to stoichio-metric M3O5. The present study focuses on this invariance and the phenomena which may cause it. The invariance was studied using thermochemical calculations and a mechanism is proposed for the observed behaviour. The mechanism suggests that a combination of thermochemical equilibrium and transient slag solidification and melting results in the observed compositional invariance. The proposed mechanism provides new insights and prompts questions about other mechanisms in the smelting process.

Jan 1, 2004