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Existing processes for the recovery of platinum group metals (PGM) from UG-2 ores place stringent requirements with regard to chromite content upon feed material to the plant. An alternative hydrometallurgical process for which this is not an issue is proposed that involves reductive roasting of the ore followed by leaching with HCl/chlorine, ion exchange, and recovery of PGM from the ion exchange eluate by reduction. Problems associated with leaching of PGM are discussed and results of laboratory testwork for each of the process steps are given.

Jan 1, 2004

By Simon St J Tose

The objective of this paper and presentation is to review the different criteria and methodology used by AEL and other organisations to create a pre-split design which delivers a stable highwall for the life of that part of the mining operation. It will look at the need to adapt and change the way, size and direction of the production blasts as the mining phase approaches the highwall position for which a pre-split has been created. Key Words: Pre-split: Design; Highwall; Perimeter

Jan 1, 2006

By H. Griesel

The overall supply of platinum is forecast to rise more than the demand, and market deficit will narrow somewhat, but is still substantial at about 480 000 ounces. Because of this deficit, the price of platinum is expected to remain high, not taking into account the impetus from funds and speculators. With this strong demand for platinum and the high price, platinum producers still need to initiate projects to not only sustain current production, but also expand output into the high demand. However, the rise in the platinum price does not entirely offset the drop in revenue due to the strong rand. Consequently, in the current economic environment, executives and managers are under extreme pressure to initiate only the highest yielding projects and implementing them successfully. During the initiation phase of a project, the cost of changing concepts is the least, and strategic project decisions are the most important. It is during this phase that the most value can be added to a project, therefore requiring inputs from highly skilled, creative and experienced people. This paper will discuss thought processes and paradigms during the initiation of projects that will assist project owners in the selection and initiation of successful and profitable projects. The project initiation process will also be discussed outlining selection models, risk analyses and funding considerations.

Jan 1, 2004

By Peter W. Lotz

Contents of: ?Sampling for Cyanide in Metallurgical Processes? ?Sampling at process level of operation ?Sampling at environmental level ?Sample stability and integrity issues ?each citing possible objectives, practical example and reasons for surprises Overall recommendations on sampling plans and procedures to maintain sample integrity

Jan 1, 2005

This is a sampling of the papers presented at the conference, the proceedings can be bought from the SAIMM The technique reported here involves measuring the air pressures generated within sealed boreholes located behind blasts. Results from twelve free face blasts in competent rock environments a represented. There were no instances of high pressure gas penetration, even at distances corresponding to less than one blast burden. Rapidly generated underpressures were measured in most holes, with the magnitudes of the peak pressures decreasing with distance behind the blasts. It has been proposed that the under pressures are the result of new volume created due to crack formation and overall rock mass dilation. The experimental evidence is consistent with this, including a correspondence of the onset times of the peak underpressures with the nominal firing times of the nearest blastholes. New post-blast cracks were observed when using borehole video cameras in the monitoring holes. A calculation of new volume produced within the monitoring holes is proposed as an indicator of damage. While the data exhibit considerable scatter, there is a power function dependence on scaled distance, which resembles that of typical vibration data. The data also lie within the normally quoted vibration regimes for rock damage and are consistent with measured extents of damage. It is concluded that this technique may provide an inexpensive and practical comparative measure of near-field rock damage due to blasting. It is further concluded that gas penetration is not a common phenomenon. Damage appears to be mainly attributable to the nearest blastholes and the control of charge mass in perimeter blastholes is emphasized for damage minimization.

Jan 1, 2000

By P. S. Paul

Mine accidents/injuries are complex and generally characterized by several factors, from technical to social characteristics. In this paper, a sociotechnical model for work injury in mines was developed and tested through structural equation modelling with application to case study mines in India. In total 14 variables were considered in this study. Most of the variables are not directly quantifiable. Instruments were developed to quantify them through a questionnaire survey. Underground mineworkers were randomly selected for the survey. Responses of 300 participants were used for the analysis. The analysis was conducted in three parts. Firstly, high-low plots were constructed to explore the variations in responses to the questionnaires by the accident involved (AG) and non-involved (NAG) workers. Secondly, a t-test was conducted to see whether the responses were significantly different for the two groups or not. The chi-square results showed significant differences of responses among the two groups. Finally, how these difference scan cause accidents/injuries in mines was hypothesized and evaluated using structural equation modelling. The measurement model of the Linear Structural Relations (LISREL) program was used to identify the latent constructs of the sociotechnical model. The structural model of LISREL was used to estimate the interrelationships among the constructs. The case study results showed that there is a sequential interaction among the sociotechnical factors leading to accidents/injuries in mines. Work hazards induce more job stress in the workers while social support mitigates the same. Job stress and safety environment predict the workers? job involvement. A worker who is more job-involved exhibits better safety performance, which in turn reduces work injury. The safety environment is shown to have a direct mitigating effect on work-related injury. The findings of this study clearly revealed that job stress and safety environment are the two key factors influencing work-related injuries in mines that need to be addressed properly through effective safety programmes.

Jan 1, 2005

By G. Westcott

Impala Platinum, the second largest platinum producer in the world, is embarking on a major expansion strategy to increase its platinum output from 1.95 moz to 2.8 moz by the year 2008. The smelter complex, situated in Rustenburg, will undergo substantial modifications, and will require a solution to the capture and treatment of the smelter off-gases and dust produced during smelting and converting operations. One of the solutions explored was an integrated approach, where all the off-gases from both the primary smelting electric furnaces and the converter operations are routed to a large central gas cleaning and double catalysis, double absorption acid plant. In-line sulphur burning, utilizing a highly flexible LURO1spin cup burner with a turn down ratio of 50%, ensures that the acid plant operates independently of operating conditions at the smelter complex.

Jan 1, 2007

By C. Wade, A. Swart, M. Dworzanowski

AngloGold Ashanti operate a pyrite flotation plant at their East Gold Plant, Acid Plant and Flotation Plant (EGAF) metallurgical complex within their Vaal River operations in the North West province in South Africa. The flotation plant feed is reclaimed pyrite rich tailings and the concentrate produced is used as the source of sulphur for the EGAF acid plant. The sulphuric acid produced is in turn used for the recovery of uranium at the Vaal River South uranium plant. The original flotation plant built in 1960 was based on the use of many small volume flotation cells and was becoming very expensive to operate and its age severely limited further operation. A decision was taken in 2005 to replace this plant with a new one based on fewer, larger volume flotation cells. This paper describes the benefits of using larger volume flotation cells in this new flotation plant when compared to the smaller volume flotation cells in the old plant. The benefits of the new plant include a smaller plant footprint, fewer flotation cells, fewer pumps, no distribution boxes, simpler piping, a greater flotation volume and a reduction in installed power. The saving in capital cost could not be quantified because of the age of the old plant. The savings in operating cost will arise from fewer operators, less maintenance and reduced power consumption. The new plant has not been in operation long enough to quantify the benefits in operating cost and metallurgical performance. However, recovery improvements can be expected given the greater flotation volume (increased residence time) and the installation of larger, more efficient flotation cells.

Jan 1, 2007

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 G. Vouille, P. Bérest

Residual stresses observed in rocks often result from non-compatible initial strains. These stresses can be determined when the incompatibility tensor associated with the initial strain tensor is known. The residual stresses in a cylindrical rock sample can be computed the sample is considered small enough for its incompatibility tensor to be constant. Les contraintes résiduelles, dont on observe couramment les manifestations dans les roches, résultent souvent de l’existence de déformations initiales non-compatibles. Ces contraintes peuvent être calculées lorsque le tenseur d’incompatibilité associé aux déformations initiales est connu. Les contraintes résiduelles dans une éprouvette cylindrique sont données dans le cas où le tenseur d’incompatibilité est constant. Eigenspannungen, die man haeufig in Steinen beobachtet, sind oft Ergebnis einer inkompatiblen Deformation des Anfangszustandes. Diese Spannungen koennen berechnet werden, wenn der Inkompatibilitaets-Tensor der Anfangsdeformation bekannt ist. Die Eigenspannungen einer zylindrischen Probe werden fuer Fall eines konstanten Inkompatibilitaets-Tensor bestimmt.

Jan 1, 2003

By S. Montes

Mineral floatability is strongly connected with mineral structure and composition. The complexity of mineral surfaces has meant that few attempts have been made to understand the effect of impurities (trace elements) on the flotation process. Zeta potential technique has been extensively used to evaluate the surface charge of mineral particles. Nevertheless, those measurements consider only an average of mineral particles surface charge. The presence of fine particles and inclusions covering a mineral may influence the local reagent adsorption process, which will ultimately be reflected in the subsequent global response of the mineral froth flotation efficiency. The current work assesses the iron oxide mineral, haematite (Fe2O3). Zeta potential and streaming potential techniques were used to determine the surface charge of fine and coarser particles of haematite. Further analysis was performed to determine the point of zero charge (PZC) of the mineral. In addition, adsorption isotherms of alkyl ammonium chloride reagents with different lengths of carbon chains were carried out. It was found haematite floatability depends strongly on the isoelectric point (IEP) value, which is affected by other mineral species present at the mineral surface. Haematite floatability became significant only at relatively high tetradecyl ammonium chloride collector concentrations (concentration greater than 4 10-4M), which does not happen with other oxides such as quartz. Unlike quartz, haematite develops a low surface charge over a wide range of pH, disabling all long-range attractive interactions between the mineral and the collector. Therefore, hydrophobic chain interaction is probably the most likely mechanism acting to promote collector adsorption and enhance further floatability. Diffused reflectance infrared Fourier transform spectroscopy (DRIFTS) was used to suggest a possible mechanism to understand the sequence of collector adsorption and the effect of trace species on it. Keywords: floatability, haematite, adsorption, electrochemistry, zeta potential.

Jan 1, 2007

By P. Sharma

Longwall panels facing wind blasts have been investigated at both Newstan and Moonee Collieries in the Newcastle Coalfield under the Wind Blast Project of the School of Mining Engineering, The University of New South Wales. The fluid mechanics involved in the compression and expulsion of air during wind blasts have been defined and the overpressure and air velocity time histories utilized to determine the wind blast parameters and define the relationship between them. The characteristics of wind blasts pressure pulses in mine roadways show some similarity with transient phenomenon like air blasts from explosives and shock waves from the failure of pressurized vessels. The peak wind velocities in roadways, however, exhibit marked deviations from theoretical predictions based on compressible fluid flow and Rankine-Hugoniot relationships applied to goaf air displacement and panel geometry. Peak overpressures and wind velocities have shown a positive correlation with the areas of goaf falls, with the values peaking off for larger areas. The field investigations have helped the mine management in risk assessment and in evaluating the success of induced caving by hydrofracturing to mitigate the hazard.

Jan 1, 2004

By RT White

For many years the concept of life cycle costing (LCC) was promoted for decision making in corrosion protection systems. Nevertheless, the application of LCC was limited. Input data was often sourced from suppliers and met with scepticism. As a result final analysis was often insufficiently rigorous to meet the needs of Project Managers in sound decision making. The need for expediency often resulted in non-optimal corrosion protection system specifications. With improved communications and the global reach of industries, case history data, based upon actual performance has been able to provide input to substantiate decision making. However, today?s focus upon sustainability whereby environmental, economic and even social aspects enter into decision making has extended LCC into Life Cost Analysis (LCA). In an LCA analysis energy and environmental inputs into systems are compared as part of an overall assessment. The development of Agenda 21 at the Rio summit of 1992 has challenged the countries of the world to look at sustainable development in every economic activity. This ranges from construction to mining to electricity production to automotive production, use and disposal. The protection of buildings, infrastructure and transport systems is part of the needs of sustainable development. Zinc based corrosion protection has been an important part of the arsenal of the corrosion protection industry. This paper will highlight the use of LCC and the development of LCA with reference to the use of zinc based protection systems in a number of important industries.

Jan 1, 2006

By Y. Wang, S. Sridhar, B. Coletti, G. N. Shannon, S. Vantilt

The final removal of inclusions in the ladle, tundish, and mold in a continuous casting process involves the kinetic steps of liquid film drainage, interface rupture, and absorption of the inclusion into the overlaying molten slag. During this process, oxide inclusions can undergo chemical reactions with the slag. This paper presents recent results on imaging the slag/steel interface and elucidates the evolution of Al2O3and Al2O3-CaO inclusions during their separation from the steel and on their incorporation into the slag. Experimental results, obtained through a Confocal Scanning Laser Microscope, are compared with thermodynamic predictions.

Jan 1, 2004

By J. A. Bakken, G. Sævarsdóttir, H. Pálsson, M. Þ. Jónsson

The role of the electric arc in the consumption of electrodes in submerged arc furnaces has long been debated. The hostile environment in the furnace does not make direct measurement feasible, so simulation has been used to evaluate the arcs contribution to the erosion. Magnetofluiddynamic (MFD) electric arc simulations and a cathode / anode sub-model developed in order to provide boundary condition to the arc model have been used for this purpose. The cathode / anode sub-model provides current distributions and cathode / anode fall voltages for the arc and temperature distribution for the electrode surface, which is paramount to the erosion rate which in turn is calculated from the Clausius Clapeyron equation and the Hertz Knudsen formula for the vapour transport. In the case of high-current industrial AC arcs, arc currents are typically ~100 kA, phase voltages ~100 V and total furnace power ~10 ? 60 MW. The results show that although enormous amounts of material is evaporated, much of it recondenses on the surface. Furthermore the results show that the arc erosion increases strongly with the arc current. If a single arc is present its contribution to erosion is close to the actual total erosion in the furnace. Results from this analysis indicate that there are possibly more than one arc present in the crater, in which case less than 40% of the total erosion would be due to the arc, the rest is chemical erosion.

Jan 1, 2007

By Braam Blom

PK2 Ventilation shaft is part of Paardekraal No 2 twin shaft system that is being developed to replace depleting Merensky reef production at Paardekraal shaft complex. The sinking team at this shaft faced considerable challenge of improving the total sinking cycle in order to be able to deliver the fully equipped shaft on time and on schedule. The cladding support cycle was identified as the tedious and time consuming activity in the overall shaft sinking operation. Reduction in the time required for handling and setting up the support installation equipment, and the time required for subsequent installation of the necessary support has a direct impact on the overall cycle time, and consequently the overall productivity and efficiency of the sinking operation. This reduction in support cycle was achieved by making use of machine carousel. The objective of this paper is to describe the support methodology that was used during the ventilation shaft sinking and the use of the machine carousel to reduce the cladding support cycle. The machine carousel replaces the traditional use of machine kibble in conventional vertical shaft sinking and has been designed specifically for installation of sidewall support at the shaft bottom during the sinking process.

Jan 1, 2009

The paper discusses the improvements achieved after an external sparger flotation column was installed as a final cleaner at the Northam Platinum Ltd. UG 2 concentrator in South Africa. It further discusses the improvements achieved after the conversion of a conventional flotation column, utilized as cleaner in the Merensky concentrator, to an external sparger flotation column. Finally, the application of the above knowledge in the design and commissioning of an external sparger flotation column as final cleaner in the furnace slag concentrator, is also discussed. 1. FINAL CLEANER AT THE UG 2 CONCENTRATOR The MF2 designed UG 2 concentrator is processing 75 000 tonnes run of mine ore at a head grade of 4.0 g/t 3PGM+Au and a feed Cr2O3 concentration of 28 %. Since commissioning of the plant in 2001, Cr2O3 in final concentrate amounted to approximately 5 % of the total mass. Although final concentrate produced from the UG 2 concentrator is blended with final concentrate obtained from the Merensky concentrator before smelting, blended Cr2O3 values in excess of 1.6% lead to difficulties in the subsequent smelting process. Several options for reducing the amount of Cr2O3 in final concentrate have been evaluated namely:- ? Differing types of depressants at various dosing rates. This test work did not reduce the amount of Cr2O3 reporting to final concentrate by any significant extent. ? Reduction in mass pull to minimize the entrainment of Cr2O3 in the concentrate stream.. This process change had a detrimental effect on PGM recovery. Conclusions were drawn that conventional mechanically agitated flotation cells could not achieve the required selectivity without sacrificing PGM recovery. As a consequence an alternative mechanism needed to be incorporated for the final cleaning of PGM concentrate.

Jan 1, 2007

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 S. O. Choi, C. Park, C. Sunwoo

Two methods of stress measurements have been executed on the surface and underground to con-struct an oil storage cavern using hydro-fracturing and overcoring method. The first measurement has been performed to make a design of the caverns before excavating and the second to confirm the stress state during excavation. Six measurements have been carried out in the hydro-fracturing test at the depths between –17.8 and 54.5m from the sea level and a single measurement in the overcoring test in a single borehole at the depth of –21m from the sea level. The ratios of the maximum horizontal to vertical stress measured using hydro-fracturing and overcoring method are 2.95 and 3.1, respectively. Also, the orientations of the maximum horizontal stress are N53E and N58E. These measurements show that both methods give almost same results and significant horizontal stresses are acting on this cavern. Deux méthodes de mesure de contrainte ont étè exécutées sur la surface de terrain et sous la terre pour construire une cavité de stockage de pétrole en utilisant l’hydro-fracturing et l’overcoring. La première mesure a étè faite pour le plan des cavités avant l’excavation et le seconde pour con-firmer l’état de contrainte durant l’excavation. Six measures ont étè faites dans le teste de l’hydro-fracturing à la profondeur entre –17.8 et 54.5m depuis l’élèvation maritime. Une seule mesure a étè faite dans le teste de l’overcoring dans une seule trou de songdage à la profondeur de –21m. Le ratios de la maximale contrainte horizontale à la contrainte verticale mesure par les deux méthodes sont 2.95 et 3.1, respectivement. Les orientations de la maximale contrainte horizontale sont N53E et N58E. Ce montre que les deux méthodes donnent presque m me résultats et la contrainte im-portante est activée sur ces cavités. Zwei Druckmessungen wurden durchgeführt auf der Erdoberfläche und im Innern von Ölspeicher-kavernen unter vergleichender Anwendung des Hydrofraktionierungs- und des Kernbohrungsver-fahrens. Die erste Messung wurde durchgeführt um einen Plan der Kavernen vor der Herstellung zu erstellen und die zweite um die Druckverhältnisse während der Bohrung zu überprüfen. Sechs Messugnen wurden mit der Hydrofraktionierungsmethode bei einer Tiefe von 17,8m und 54,5m unter dem Meeresspiegel und eine einzige Messung mit der Kernbohrungsmethode in einem Bohr-loch bei einer Tiefe von 21m unter dem Meeresspiegel vorgenommen. Das Verhältnis von maxi-malem horizontalem zu vertikalem Druck bei der Hydrofraktions- und der Kernbohrungsmedthode ist 2,95 bzw. 3,1. Die Bezugspunkte des maximalen horizontalen Drucks in beiden Verfahren sind N53E und N58E.

Jan 1, 2003

By H. Saridikmen, C. S. Kucukkaragoz

In the present study, the measurement of sulphur distribution ratios between the slag and metal phases encountered in the ferromanganese smelting has been carried out at 0.83 atm of partial pressure of CO at 1773 K by using classical gas-slag-metal equilibrium quenching technique as a function of composition. The distribution results were employed in calculating the sulphide capacities of SiO2-Al2O3-CaO-MgO-MnO slags in equilibrium with the Mn-Fe-Si-Csatd.-S metal phase. It is shown that the sulphur transfer from metal to slag phase increases with increasing the basicity of the slag. As expected, the sulphur distribution ratio decreases by increasing the silica content of the slag system. The effect of metal composition on the sulphide capacities of the slag as well as on the sulphur distribution ratios between the slag and metal phases have been discussed. Emprical relationships were developed to express the sulphur distribution ratios and sulphide capacities of the above slag system.

Jan 1, 2007