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By M. du Toit

Cromanite?is a new high-strength austenitic stainless steel developed by Columbus Stainless. It contains approximately 19 percent chromium, 10 per cent manganese and 0,5 per cent nitrogen. Cromanite can be welded successfully, but due to the high nitrogen content of the base metal, certain precautions have to be taken to ensure sound welds with the desired combination of properties. Although no matching filler metals are currently available, Cromanite can be welded using a range of commercially available stainless steel welding consumables. Welds produced using E309L, E307, E307Si and E312 filler wires are resistant to hot cracking and the formation of nitrogen-induced porosity, but the hardness, strength, ductility and toughness of the welds are generally inferior to those of the base metal. In applications where full use is made of Cromanite?s high strength, welds with matching strength levels would be required. In wear applications, where Cromanite is used primarily for its work-hardening properties and corrosion resistance, lower strength welds would probably be acceptable. Welds produced using E307 filler metal demonstrate the best combination of properties for use in wear applications. The welds display high rates of work-hardening that would result in increases in hardness and strength when subjected to abrasive or high impact environments.

Jan 1, 1999

By H. Tveit, E. H. Myrhaug, J. K. Tuset

Silicon metal as a commodity material is produced by carbothermic reduction of quartz in electric submerged arc furnaces, where CO2 forms as a by-product. Since 1997 the Norwegian Ferroalloy Producers Association have been engaged in research programmes aiming for reduced CO2-emissions associated with fossil carbon in their processes. One important issue has been to study how charcoal and wood chips perform compared to coal and coke in the silicon process. The ability of the carbon-rich reduction materials to react with SiO-gas is commonly assumed to be of large importance to the performance of the process. Based on laboratory experiments with different carbon materials, combined with estimation of parameters in a mathematical model of the reaction between carbon and SiO-gas, a foundation for a theoretical study of the performance of the carbon materials in a silicon furnace is established.

Jan 1, 2004

By A. M. Bryukhanov, A. G. Mnukhin

The report states accident rates for gassy/dusty coal mines represented as an ergatic system "man – machine - environment" with further analysis by the method of conditional probabilities. A coal mine has been analyzed with allowance for the attending personnel, equipment and environment as a sequence of events and states. Probabilities of operational states have been determined and prediction of mine behavior has been made on the basis of investigation findings for equipment and the personnel states, and analysis of the environment (i.e. mine and mining conditions). Utilization of expert estimation methods has been considered for determining major operational parameters of gassy/dusty mines. The importance of standardized values of permissible occupational risks (permissible probability of accident, PA) is demonstrated. It is also stated that a procedure is essential to determine these values, involving regular check-ups of the integral safety criterion at all mines and further development of customized recommendations for individual mines on efficient improvement of accident situations. Methodology to determine the assessment criteria has been developed and scientifically substantiated for permissible accident rates in hazardous industries.

Jan 1, 2003

By M. van Schoor

Coal remains South Africa?s most abundant and cheapest source of energy, and there is an ever-increasing necessity for optimal and safe extraction of the remaining reserves. Increasing focus on cost-effective mining and zero harm to the environment and miners has resulted in a shift in attitude towards the application of geophysics in local coal mining and exploration. Furthermore, technological advances have contributed to geophysics being embraced more readily by the coal mining industry, compared to a decade or two ago. Predictably, the growing interest in geophysical technologies has also created a need for education and training in the basic principles and application of geophysical methods, as local coal mining companies generally do not have in-house geophysicists. Consequently, the Coaltech Research Organisation?s Geology and Geophysics working group forum compiled a textbook aimed at addressing this need: to produce a guide for applying geophysics to coal mining problems in South Africa. The target audience for such a book would be coal geologists, mine surveyors, mine planners, and other mining staff with limited or no geophysics background. This paper provides a very brief overview of the book by summarizing key sections and selected examples. In doing so, the value of geophysics to solving a range of coal mining and exploration problems is highlighted.

Jan 1, 2014

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

Jan 1, 2012

It is estimated that the tailings dam of the Mouteh Gold Mine, in Iran, contains more than 770 kg of gold. Microscopic analysis reveals that sulphide minerals and active carbon are the main sources of the gold in the tailings residue. Flotation and cyanidation tests on the samples of tailings were conducted. Flotation concentrates, containing around 87.79% of the gold, which were associated with sulphide minerals, were recovered. By regrinding, roasting, and cyanidation of the flotation concentrate, the gold dissolution recovery was in the range of 87.8 to 98.4%. The carbon-in-column method was used to recover 98% of the gold from the solution. Keywords: gold ore, pyrite, flotation, roasting, cyanidation

Jan 1, 2009

By C. Kruger

Anglo American Platinum has adopted a strategy of best practice principles (BPP) for sampling, mass measurement, analysis, and metal accounting for more than a decade now. When new plants are designed, the most suitable sampling equipment and sampling protocols are implemented and material flows and plant layouts are designed around sampling strategies. A few years ago, a crushing plant for a high-grade matte stream was commissioned. The design called for the high-grade material to be crushed to 95% passing 2 mm, and the design allowed for a single-cutter primary Vezin sampler taking increments from a gravity flowing stream at regular intervals while filling a tanker for pneumatic offload at the base metal refinery. This was a single point of sampling and analysis that would measure the wanted output from the smelting complex and the input to the refineries. In addition, the design incorporated the functionality to collect increments in an ?interleaved? fashion from the Vezin sampler for internal precision checks. The metal accounting strategy for Anglo Platinum involves the ongoing measurement of all inputs, outputs, and stock levels for all operations for platinum group metal (PGM) and base metal (BM) content. Included are yearly stocktakes, usually done on 1 February, across the smelters and refineries (at least the base metal refinery). In the accounting period immediately following the introduction of the new crushing and sampling facility, a trend was developing whereby the absolute difference between the physical stock and theoretical stock (PGMs predominantly) increased for the two respective sites on an ongoing basis. The smelter showed an increase in physical stock compared to the theoretical stock (sender) and the base metal refinery showed an increase in theoretical stock against physical stock. Because of this anomaly, an additional stocktake was held in September for the period in question, and it was confirmed through the physical stock measurement results that the PGM accounting problem was indeed pointing towards the evaluation of the high-grade matte stream. This paper showcases parts of the process that took place to explain the poor accountabilities for the two sites. Previous results from the sampler ratification process (of the interleaved sampling design) were reanalysed, a physical inspection was carried out on the sampling system again, and the sampler performance was monitored (quality control parameters) for the period. From these investigations, it was found that airflows inside the Vezin introduced the sampling bias. A change in sampling protocol was introduced, as well as certain physical changes to the sampling equipment, to eliminate the airflow and thus the bias conditions significantly. The accounting period that followed the phased upgrading process showed that the accounting between the smelter and base metal refinery had been restored to within statistical limits (difference between physical and theoretical stock below 5% relative to theoretical stock). Keywords sampling, metal accounting, Vezin sampler, sampler bias.

Jan 1, 2014

The 109th Annual General Meeting of The South African Institute of Mining and Metallurgy was held at The Country Club, Johannesburg, Napier Road, Auckland Park on Wednesday, 16 August 2006. Special General Meeting A Special General Meeting to consider the changes to the Constitution was held immediately prior to the AGM. 1. Purpose In order for the SAIMM to remain relevant and ensure maximum value to all members, Council propose three changes to the Constitution. 2. Background Three changes to the Constitution were proposed by the Council on 21 July 2006. These changes now have to be approved by means of a ballot at a Special General Meeting. These three proposed changes are discussed briefly below:

Jan 1, 2006

By Peter Voulgaris, Allan Haines, Diane Walker, Ian de Bruyn

The Oyu Tolgoi porphyry gold and copper project is located in the south Gobi region of Mongolia. The Ivanhoe Mines project has the potential to become a long-life copper and gold producer that could rank among the largest in the world. There are five deposits which cover a strike length in excess of 6.5 km, from south to north they are named South Oyu, Southwest Oyu, Central Oyu, Hugo South and Hugo North. The first three, collectively known as the Southern Oyu deposits, are planned to be mined by open pits, whilst extraction of the deeper Hugo deposits is planned using block caving techniques. The pits will have diameters of approximately 1000m and a maximum depth of 550m. The geological environment consists of a sequence of porphyritic augite basalt, dacitic tuffs and sedimentary rocks that have been intruded by several generations of porphyritic quartz monzodiorite and numerous post mineralization dykes. Several major faults cut through the southern deposits juxtaposing the relative position of the stratigraphy. The geotechnical investigation for the Oyu Tolgoi Open Pits was conducted in three distinct phases of increasing complexity: scoping study; advanced scoping study and feasibility study. Each phase consisted of data collection, interpretation and analysis designed to progressively develop 3D geotechnical domaining for the empirical, structural and numerical evaluations. The development of the geotechnical design parameters for these green fields open pits posed many technical challenges, brought about by the conditions associated with a lithologically and structurally complex environment. The design work focused on the optimization of the pit geometry to conform to equipment selection and blasting characteristics. Limiting bench stack heights were derived from the influence of major structures. The overall slope angles in each pit sector were developed around the requirement for haulage ramps and geotechnical berms. This paper describes each of these aspects and the methodology used to address the integration of the geotechnical characteristics with the mining environment.

Jan 1, 2006

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 L. J. Gardner

Ore pass systems play a critical role in moving broken rock from the workplace to surface, and the integrity of the ore pass excavations is crucial. Over the life of the mine, ore pass integrity deteriorates, which may eventually result in the ore pass no longer being fit for purpose. This paper presents several case studies of successful ore pass rehabilitation exercises.

Jan 1, 2006

By N. L. Ayres

Tendon support systems have been successfully used to stabilize excavations. Tendon support systems are routinely designed using the axial load-bearing capacity of tendons, namely the tensile strength. To attain tensile strength the tendon must be loaded along its length, which often does not occur in practice. Tendons should optimally be installed at 90° to the surface of the excavation to achieve maximum penetration depth, yet this is often not physically or practically possible, and installations at angles less than 90° occur. Furthermore, the intersection of geological features within the rock mass frequently results in complex loading situations on tendons. The position and angle at which loading occurs results in different combinations of tensile and shear forces acting on the tendon, which can impact on the support performance of each unit and ultimately the whole system. All factors that influence the support system should be understood and taken into account to ensure a sound support design. Combination loading situations are further investigated and tested to obtain a better understanding of the mechanisms involved and the effects on tendon load-bearing capacity. Tendon support units were tested at different installation angles to establish the tendon performance, mechanical behaviour, and load capacity during these loading situations. The results and outcomes are aimed at providing rock engineers with additional data and improved understanding of how tendons could perform under certain conditions.

Jan 1, 2014

By David Colloby, Darelle T. Janse van Rensburg

Premature coating failures of new and refurbished structural steelwork of clarifiers have been a common occurrence at power generation plant in recent years. Several of these failures have ended in disputes regarding which party was actually to blame for the early degradation of the coating system, i.e. quality of the power station?s water, poor application, substandard materials, outdated corrosion protection specifications, etc. Having investigated several of these premature failures, it is clear that the corrosion protection of clarifier steelwork is a highly complicated process and that the painting work needs to be closely monitored in order to ensure long-term protection by whichever product that is applied. The need for quality control inspections during the painting of the plant is often underrated during the project planning stage, also the importance of detailed corrosion protection specifications that consider not only the practical application of the materials, but also the quality control responsibilities of the Contractor, End User and Third Party Inspectorates that may be involved. This paper considers the application constraints of coatings to clarifier structural steelwork and importance of stringent quality control procedures in order to ensure the long-term performance of the corrosion protection systems.

Jan 1, 2006

By J. H. Van Reenen, H. Thiele, C. Bergman

For some time spirals have been the process equipment chosen to recover metal in the size range 0.15 to 3mm from ferrochrome and silico/ferro manganese slags. Recoveries of metal obtained using spirals are usually about 70%. Spirals are also difficult to control. By combining a novel gate on the Apic pneumatic fines jig with the recently developed Apic classifier, metal recoveries of 76% and grades of over 90% have been obtained for FeCr and SiMn slags in the size range 0.15 to 3 mm. The paper compares classifier operating performance and costs with those spirals for FeCr and SiMn metal recovery from slags. The classifier technology can also be applied to chromite and iron ores and coal fines.

Jan 1, 2004

By Dechun Lou, Benjamin Ravary, Merete Tangstad, Stein Wasbø, Sean Gaal

The melting phenomena of manganese ore, slag and alloys were studied in an experimental sessile drop furnace. Particles of approximately 20-60mg were placed on graphite substrates and then heated at a constant rate of 5°C/min up to 1830°C in a controlled gas atmosphere of Ar or CO. The shape of the particle was photographed with a digital video camera every second. It was observed that the melting behaviour can vary significantly, with some particles exhibiting a large softening/melting range. Selected samples were sectioned and then analysed with EPMA. The implications of the results on understanding industrial furnace operations are discussed.

Jan 1, 2007

By Jochen Petersen, Thandazile Moyo

"The oxidative leaching of chalcopyrite in ammoniacal solutions has been evaluated using electro-analytical techniques. The anodic dissolution process has been established to be a seven-electron transfer process under nitrogen in ammonia–ammonium sulphate solutions and ammonia–ammonium carbonate solutions. The number of electrons transferred in the carbonate and sulphate salts suggests that the sulphur is oxidised to a thiosulphate intermediate and the copper and iron released as Cu+ and Fe2+. The Cu+ and Fe2+ is subsequently oxidised in solution in non-Faradaic reactions. The deportment of Fe2+ and S2O32- is affected by choice of the ammonium salt used in the leaching process. In the perchlorate salt, only five electrons are transferred, however observations made on the mineral surface after leaching do not support the formation of elemental sulphur. Scanning electron microscopy and energy-dispersive spectroscopy analysis of the mineral surface suggest presence of an iron–sulphur surface layer completely free of copper under the ammonia–ammonium sulphate conditions, an iron-rich surface layer under ammonia–ammonium perchlorate solutions and absence of surface layer build up under ammonia–ammonium carbonate solutions. INTRODUCTION Hydrometallurgical processes for copper extraction provide a viable route to recover the metal from mixed and low-grade ores, as well as overcome the environmental challenges faced by the traditional pyrometallurgical processes. Chalcopyrite is not only the most abundant of the copper sulphides, but also the most stable, making it recalcitrant to hydrometallurgical processes. Hence, hydrometallurgical processing of chalcopyrite continues to be an attractive area of research due to the vaguely understood surface chemistry of the mineral in different aqueous media. Different approaches to hydrometallurgical treatment of chalcopyrite can be carried out. These include thermal treatment prior to leaching, direct leaching and direct electrochemical leaching (Venkatachalam, 1991). Direct leaching of chalcopyrite can be carried out in various solution systems, as reviewed by Roman and Benner (1973) and Venkatachalam (1991). Ammoniacal solutions are attractive and effective lixiviants that form stable amine complexes with some base-metal cations while rejecting iron. Leaching of chalcopyrite in ammoniacal solutions in the presence of an oxidant is possible due to the stabilisation of copper(I) and copper (II) by ammonia at elevated pH levels. In oxygenated ammonia solutions, it has been suggested that chalcopyrite dissolves according to Equation 1 (Beckstead & Miller, 1977a):"

Jan 1, 2015

By M. Ayhan

Drums of a modern longwall shearer are manufactured to include various constructional features conveying extracted material onto the face conveyor as efficiently as possible. Designing a drum with a conical shell or with reduced vane length, consequently with a stepper vane angle, is the most widely employed method in an attempt to increase loading efficiency. This study compares loading performances of two such drums, one having a conical shell with modified loading vanes, the other with a cylindrical shell with reduced vane length. Firstly, the loading performances of drums are predicted and the maximum haulage rate attainable with the drums are calculated. Then the performances of drum are compared by long-term comprehensive underground trials with coal shearers under similar conditions during the production operation of Park Termik Cayirhan coalmine in Turkey. Although higher loading performance is predicted for cylindrical drums, the in situ trials point out that Globoid drums have a slightly higher loading performance than cylindrical drums. Furthermore, the relationship between operational variables, i.e. extraction height, sumping depth, haulage rate and in situ loading performance, were investigated statistically on the basis of data gathered during the underground trials. Keywords: longwall mining, shearer drums, loading performance.

Jan 1, 2006

By M. Jeffrey

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

Jan 1, 2009

By Rajib K. Mohapatra, K. Vizaya Kumar

In any manufacturing organization internal logistics plays a vital role in improving and maintaining the productivity. In Ferro Alloys manufacturing organization where there is huge input of raw material in terms of ore, reductants and variety of fluxes amounting to about four times of the mass of alloy produced need to be handled from yard to furnaces , internal logistics requires utmost attention. Any deviation or mismatch between stock and requirement will affect furnace operation. Though the activities are being outsourced by most of the organization, these require close monitoring. This communication presents an optimization model which can work as a ready reference for the manager to decide upon the material quantity and the furnace to be fed with an objective of minimizing the cost of handling and zero production loss.

Jan 1, 2007

By L. van Dyk

The project was aimed at evaluating the double-header trains implemented at Great Noligwa mine, looking at the changes from the old conventional trains to the new trains, and identifying possible improvements to obtain an even better and more productive tramming system. The methods used to evaluate the double-header trains at the mine included personal observations, time studies, personal interviews, technical research, safety analysis, cost analysis, production analysis, breakdown analysis, break test analysis, comparisons and working closely with engineering department and manufacturers. Issues that were evaluated are the improvements in safety, cost reductions, tramming congestion reductions, better efficiencies, labour optimization, enhanced driver safety and maintenance. Shortcomings of the double-header trains were identified and recommendations made to improve on the shortcomings. Findings of the evaluation study indicated the following: ?Drastic improvement on safety ?Extreme cost reductions ?Reduction in tramming congestions and bottlenecks ?Better tramming efficiencies ?Optimized labour placement ?Enhanced driver safety ?More effective maintenance. Although there is room for improvements, the double-header trains were implemented with great success at Great Noligwa mine. It is currently the preferred tramming methodology at Great Noligwa mine, and is also implemented at other Anglo Gold Ashanti?South Africa shafts. This tramming system has huge potential for growth, not only in Anglo Gold Ashanti, but in all other older mines that experience major tramming problems.

Jan 1, 2008