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By Antonio Karzulovic, Sergio Olavarría, Patricio Adriasola

The economical analyses of different Chuquicamata open pit mine planning scenarios, indicate that the pit closure should occur at latest in the year of 2017. However, about 60,000 m of drill holes have demonstrated that below the pit bottom there is a potential of 2.3 billion tons of ore. Hence, Division Codelco Norte developed the scoping engineering for a large underground panel caving operation, similar to El Teniente mine. This project considers the exploitation of a 2500 m 300 m footprint, with three 250 m lifts. The plan considers to initiate the construction in the year 2009, to begin the production in the year 2015 and achieve a production rate of 45 million tons per year in the year 2021. A large-scale transition from open pit to underground mining like this one presents three main challenges: (1) to include the geotechnical aspects relevant for mine design and mine planning, (2) to define the proper surface and underground infrastructure, and (3) to fulfil the project deadlines and to achieve the production targets. This paper summarizes this transition project and discusses these three main challenges.

Jan 1, 2006

By M. J. Lukhele

Paper written on project work carried out in partial fulfilment of B. Tech (Mining Engineering) degree A number of high wall mining methods were developed over the years to mine coal reserves exposed on the high walls created during surface mining. The auger mining system was initially developed in the early 1940s in the United States of America. High wall mining is a method of recovering coal from seam exposed either by mechanical excavation methods or natural erosions. This is usually associated with strip-mining (opencast) where the stripping ratio is high and uneconomical to mine using the opencast mining method. This paper discusses the surface auger mining as deployed at Rietspruit Mine Services Proprietary Limited.

Jan 1, 2002

By E. Mpoloka

Debswana together with ADP as their design partner have embarked on an RDP project at Jwaneng Mine. The objective of the project is to install a 2 million ton per annum mineral processing plant that will fast track the recovery of diamonds from the Debswana tailings resource to ensure maximum return on investment for the company. Due to the prevailing economic conditions Debswana has had to review the way they used to build plants in the past and consider simple, fast and effective ways of doing things. The rapid deployment plant concept is therefore the most suitable means of achieving this objective. Debswana is also considering an operating partner who will operate far more efficiently and cheaply compared to the larger more cumbersome and less agile Debswana.

Jan 1, 2010

By M. Rakoma

Following the blasting fatality on 17 December 2009, Landau Colliery was forced to change from the blasting practices that had been utilized since the start-up of the mine. Since then, attempts have been made to optimize blasting results. The challenge is rooted to the mining environment - during the early life of the mine, mining took place in virgin areas, whereas currently mining is taking place in areas overlying old underground bord and pillar workings. The underground bord and pillar workings aggravate phenomena such as spontaneous combustion, hot holes, and sinkholes. The 2009 fatality was attributed to hot holes causing premature detonation. Landau has been struggling with poor results from their overburden and coal blasts; leading to poor fragmentation of overburden and the PI parting that lies between the No.1 and No.2 coal seams. An extensive literature survey was completed in order to identify possible alternative solutions that could be evaluated for this unique mining environment, which demands a high degree of caution during mining to ensure factors such as dragline stability and personnel safety. The literature survey confirmed that the previous blasting technique, which was mainly characterized by air decking, was indeed the more efficient, although it was deemed unsafe because of the possibility of hot holes and the high sensitivity of detonators. Potential modifications to the blasting technique were modelled in a Microsoft Excel simulation that was available from the mine, and pit visits were conducted in order to determine whether implementation would be a problem. From the model it is evident that results can be improved by changing the current burden and spacing ratio. Visiting the pit revealed that the tie-in pattern and drilling inaccuracies are contributing to problem areas.

Jan 1, 2013

By T. M. Chagwedera, A. E. Lewis, J. Chivavava

Eutectic freeze crystallisation is a novel separation technique that can be applied to treat brine solutions such as reverse osmosis retentates, which are often a mixture of different inorganic salts. The treatment of calcium sulphate-rich brine solutions through eutectic freeze crystallisation has resulted in gypsum scale formation on the walls of the crystallisers and ancillary equipment. In order to prevent gypsum scaling on equipment surfaces, it is essential to understand the mechanism of gypsum scaling on cold surfaces. This paper focused on the interaction between gypsum crystallisation in the bulk solution and scaling on the crystalliser walls in the presence of gypsum seeds. A cooled, U-shaped stainless-steel tube suspended in the saturated solution was employed as the scaling surface. Preliminary results showed that the scale layer was predominantly composed of needle-type and hexagonal prismatic crystals. The rate of scale deposition was highest during the first 24 hours, thereafter it decreased. A thin scale layer was observed to have coated the tube within the first hour of the experiment. Seeding, using reagent grade gypsum crystals, was effective in reducing scale layer formation through providing a surface for growth. The highest scale reduction, 81%, was realised at a seed loading of 0.50 g/L. At a high seed loading of 4.01 g/L, the seed material adhered to the tube. Keywords: Gypsum, eutectic freeze crystallization, seeding, scaling, cooling crystallisation

Jan 1, 2020

By I. Fedotov

One of the most effective methods of metal surface heat treatment is through laser hardening. In most cases, laser parameters are determined experimentally, which is expensive and time-consuming. A mathematical model for the surface heat treatment process will allow a significant decrease in costs, and reduce the time required for optimization. In the present work, the authors present a mathematical model for laser heat treatment with forced cooling which can be applied to medium carbon steel. The model is based on a three-dimensional heat transfer equation using Green?s function. The model allows one to calculate the temperature of the treated steel at different depths below the surface with and without cooling, for set values of the laser power and travelling speed, when the heat transfer coefficient is a known constant. It also takes variations in the radiation adsorption coefficient on the metal surface and laser beam spot size into account. The model was illustrated by comparing calculated and experimental temperature profiles of mild carbon steel with 0.5% C with and without cooling. A reasonably good agreement was achieved between experimental and predicted values to ensure that a high enough austenizing temperature with short enough cooling time was reached for direct martensite formation. It also predicted the depth of treatment accurately. The incorporation of cooling in the model substantially improves previous models based on heat transfer only. It delivers a tool that can with a reasonable accuracy predict the depth of surface heat treatment and cooling time required from operational parameters, such as laser power, speed of motion, and distance between laser and cooling source, that can be controlled in the work set-up. This can eliminate trial and error efforts and result insignificant time and cost savings. Keywords Laser, surface treatment, martensite transformation, carbon steel, heat treatment.

Jan 1, 2011

By A. Nuric, S. Nuric, L. Kricak, M. Negovanovic, S. Mitrovic

"SynopsisRotary drilling with rolling tricone bits is the most widely used method for drilling large-diameter blast-holes in large surface mining operations. This drilling method is applicable to a wide range of soft to hard rock materials. This paper presents a fuzzy model for predicting the penetration rate of tricone rotary blast-hole drilling. The model is based on data obtained during the drilling of blastholes in rocks with various uniaxial compressive strengths in the Veliki Krivelj open pit mine, Bor, Serbia. The model was developed using the fuzzy logic toolbox of MATLAB with the Mamdani inference system. The fuzzy model was tested with 23% of the total dataset. The results obtained show the high reliability of predicting the penetration rates. Although there are possible limitations in applying the model to other open pit mines because of differences in rock properties, the prediction methodology applied in this paper can be used in many other predictions of the penetration rates.IntroductionAccording to Tamrock, rotary blast-hole drill operations depend on four important elements:•,Torque in the drill string drive sufficient to turn the bit in any strata encountered•,A high bit loading capability (pulldown force) sufficient for optimum penetration•,An air volume sufficient to remove chips generated during the drilling and to provide cool air to the drill bit bearings•,The selection of the proper type of bit for the material being drilled (Tamrock, 1984).The effects of rock mass parameters on the choice of the type of tricone bits were investigated by Kricak (1997)."

Jan 1, 2015

By P. J. Petit

Financial evaluation is necessary to investigate the viability of implementing and/or utilising new technology in mining projects. It establishes a techno-economic base for decision-making and justifies capital expenditure. This paper aims to present a monetary appraisal of the electric rock drilling system in a typical feasibility project, whose purpose is to increase the production rate. The in situ environment is a platinum orebody, and the stoping operations occur in UG2 reef. The results are a function of production requirements, technical parameters and financial outlay of the drills. The costs involved in implementing and operating electric rock drills are assessed to the current method of drilling, namely the compressed air operation. A comparison of the electric and pneumatic rock drills in terms of financial outlays for drilling and service requirements, peripheral equipping and training is discussed. Other factors that affect the business case are technical advantages, safety and risk management and the environmental objective of the company.

Jan 1, 2006

By A. Koursaris, J. B. See

The influence of Iscor coke and Delmas coal on the reduction of Mamatwan manganese ore to ferromanganese was examined by use of a variation of the 'stationary charge in controlled environment' (SCICE) technique. The charges of Mamatwan ore and the appropriate reducing agent were heated to temperatures between 1300 and I600 °C and either allowed to cool immediately the required temperature had been reached or held at that particular temperature for periods of up to ... hours. The heating rate was 350°C per hour, the particle size of the ore was between 2,83 and 12,7 mm, and the particle size of the reducing agent was between 2,83 and 6,35 mm. After being allowed to cool in air, the reacted charges were examined by optical microscopy, X-ray-diffraction analysis, scanning electron microscopy, and electron-microprobe analysis. No significant difference was found between the changes observed during the reduction of Mamatwan manganese ore by Iscor coke and by Delmas coal. A hypothesis is advanced to explain the mechanism of formation of the Fe-Mn-C alloy.

Jan 1, 1979

By D. van Rensburg

Jointed rock slopes are generally stable, as there is no freedom of movement for blocks of rock. In an open- pit mining environment, blasting opens up space into which blocks of rock can fail, resulting in the common occurrence of slope failure. Prior to the blasting of a trim pattern, the immediate highwall is scaled, where loose rock material is removed by means of a mechanical scaler. As mining of the pit progresses, the height of the scaled highwall from the pit floor progressively increases. These highwalls are never scaled again for the remainder of the pit life, and time-dependant deterioration contributes to these highwalls becoming subject to rockfall and, sometimes, slope failure. This paper documents the development of a South African innovation, a remote-controlled mechanical highwall scaler, a world first for the mining industry. The scaler will enable open-pit highwalls to be scaled from crest to toe whenever the need arises. It will reduce the risk associated with highwalls and deliver on the Anglo American promise of producing safe, profitable platinum.

Jan 1, 2012

By L. A. Thompson, A. J. Linington

"Copper–cobalt extraction is a reagent-intensive process resulting in acid consumption greatly contributing towards production costs, which in the current market conditions curtail profitability. Nanofiltration (NF) membranes have become an attractive approach in the mining and minerals industry for product concentration and reagent recovery based on the ability of the membrane to separate monovalent ions from divalent ions. NF membranes can selectively separate acids from metals and salts allowing acid to be recycled as well as the concentration and purification of product streams. Membrane technology in the field of copper–cobalt processing focusses on the concentration of Cu2+ and Co2+ in the pregnant leach solution, recovery of acid from waste streams to neutralization, recovery of valuable metals from waste ponds and process water recovery. This paper aims to provide insight into the potential applications of NF membranes in copper–cobalt processing circuits as well as a brief overview of the effects of process conditions on membrane performance and process development. INTRODUCTION The copper–cobalt industry commonly uses inorganic acids, such as sulfuric acid, in large quantities for primary leaching of copper–cobalt oxide ores and releaching during product purification (Stuurman et al., 2014). This results in numerous acidic intermediate streams containing high metal concentrations and acidic waste streams with low metal concentrations. Acid consumption typically accounts for 10–15% of the operating costs of mines in the Democratic Republic of Congo (DRC) and Zambia (Acid Plant Database, 2015). Due to remote mine locations, poorly maintained roads and cross-border conflict, the cost of sulphuric acid can range between USD 300 and 400 per ton. The pivotal role of acid in the copper–cobalt extraction process has driven many mines to build sulphuric acid plants on site to ensure a reliable acid supply, however elemental sulphur still needs to be imported which faces similar logistical challenges and contributes towards operating costs."

Jan 1, 2015

By Donald Leroux, Simon Gariépy, Luc Lachance

"Quantitative information about the quality of metal balance results is often overlooked when making important plant production planning decisions. Not only is this common omission made in a context where many measurements taken in and around mineral processing plants carry significant errors, but it also conflicts with the AMIRA P754 Code of Practice for Metal Accounting. The fact that metal balances are typically published without any indication of data quality may give the wrong impression that the measurements are unquestionably accurate. While it is true that statistical data reconciliation can improve the confidence intervals of redundant variables, there is no data processing technique that brings them down to zero at a finite cost. In this paper, we review the entire data flow, starting from field instruments to metal accounting-based decision-making to show how measurement errors are transmuted into business risks associated with production planning. Necessary conditions for first exposing then quantifying such business risks are stated. Pitfalls to be avoided are also discussed. Finally, a simplified risk assessment and management procedure which considers the quality of metal balance results are applied to a polymetallic mineral processing plant. INTRODUCTION Each and every mineral processing plant has production reporting obligations. In this paper, we are concerned with metal accounting reports (Morrison, 2008) where saleable metal flows and inventories are estimated and published. These metal accounting reports are delivered to a variety of stakeholders who use them for internal management purposes (day-to-day plant production planning, plant operation optimisation, capital spending, etc.) as well as for external management (royalty settlements, tolling agreements, etc.). Hence, there should be no doubt that spotless metal accounting is instrumental to high-quality corporate governance (Gaylard et al., 2014) of mining and metallurgical companies. To this extent, one would have expected industry-endorsed standards to have emerged a long time ago. However, the lack of an accepted set of standard procedures for metallurgical accounting was explicitly recognized as an industry-wide problem only in August 2001 during an SAIMM workshop held in Cape Town, South Africa. Discussions that followed this workshop led to the initiation of the AMIRA Project P754, “Metal Accounting and Reconciliation”, in 2003."

Jan 1, 2015

By J. D. Stone

This paper briefly reviews the adequacy of existing management theories and practices and the managerial proficiency or competency in the South African mining industry. The investigation revealed that existing management practices are totally inadequate to enable all employees on all the levels of the mining industry to achieve the results required from them, in all aspects, at all times. As a result, the South African mining industry is gradually losing its long standing reputation as a relative cheap, competitive, and reliable supplier of minerals to the local and global markets. According to some prominent management authors and theorists, an all-inclusive unified management theory does not exist at present. In this paper the authors summarize the main aspects of a newly developed comprehensive, practical, and integrated management method. It is believed that the application of this method would significantly improve the future performance and competitiveness of the South African mining industry

Jan 1, 2010

By I. M. Wolf, S. A. Usmar, L. A. Cornish

The limiting criterion in the use of stainless steel for certain forming operations such as coining is its hardness, which determines parameters such as required striking pressure, wear on dies, and integrity of pattern detail. Attention is given here to the development of ultra-soft ferritic stainless steels for coinage. In the first instance, the influence of carbon content on the striking properties of a series of commercial and experimental 17%Cr alloys was evaluated. It was found that a lower carbon content permitted the striking of relatively highly profiled and intricate patterns, provided that the hardness did not exceed 125 HV. Hardnesses as low as 115 HV were achieved in the fully annealed condition, but these alloys required high striking pressures. In a further study, three grades of experimental 14%Cr ferritic stainless steels were produced with a view to optimizing the ductility. When the residual impurities were minimized, hardness values of about 100 HV and lower were achieved. Micro-alloying additions allowed the heat-treatment response and grain size to be controlled. Excellent tensile properties, with elongations of up to 42 per cent, were achieved in the fuly annealed condition, and highly profiled patterns were produced in coining trials.

Jan 1, 1993

By G. Bueno, L. M. Tavares, T. M. Campos

Iron ore pellet feed pressing has been one of the first and most successful applications of High- Pressure Grinding Rolls (HPGR) in the minerals industry. Vale S.A. has been one of the pioneers in this application, currently with six HPGRs in operation in the pelletising plants of the Complexo de Tubarão (Brazil). In spite of the important advances in the technology, risks still exist when scaling-up the process from small-scale information. The present work takes advantage of the recent advances in the mathematical modelling of the HPGR performance, using the population balance model to evaluate the modified Torres and Casali model prediction in iron ore pellet feed pressing for different scales of operation. Results are presented that compare the HPGR performance in different operational scales for iron ore pellet feed pressing, demonstrating the confidence of this model-based approach for scale-up to full-scale HPGRs used in pressing iron ore concentrates. Keywords: Scale-up, HPGR, pellet feed, modelling, simulation

Jan 1, 2020

By J. J. Stacey

Large mining companies generally follow the distributed ownership corporate model, with a board of directors responsible for decisions that affect both shareholder value and stakeholders of the company. The board is simultaneously responsible for setting the culture and values of the corporation, which drive performance and priorities. Companies listed on the Johannesburg Securities Exchange (JSE) commit to sustainable development in various ways, either by virtue of implementing the King Code of Governance 2009 (King III) and/or through their own public reporting on social and environmental matters. Many mining companies make public statements regarding their support for environmental stewardship, ethical behaviour, and fair treatment of communities. It is a local, regional, and indeed, global phenomenon that companies fail to deliver on these statements. Research was carried out through the Institute of Directors of Southern Africa in 2007, and followed up in 2012, regarding directors? understanding of sustainable development issues, the relative priorities, what is needed for ?radical change? to effect sustainable development, and what enables or constrains the latter. Pertinent findings of both surveys are presented in this paper, and it is suggested that ?on-the-ground? performance may be indicative of the nature of leadership and decisions in the topmost ranks of the company. The results indicated that environmental concerns fall consistently below social issues. Financial capital ranked most important, and while environmental issues are recognized as being of strategic concern for the long-term, they ranked as being the lowest importance of all ?Five Capitals? (Financial, Manufactured, Social, Human, and Natural). Social capital ranked second lowest, with black economic empowerment being the only high-priority social issue. There is also evidence that certain companies within the mining sector fail to recognize their absolute dependence on natural resources. Much is made in academic and popular literature of the need for a new type of leadership for the radical shift to sustainable development: at company level this implies therefore a new type of director. The research found that only 14 per cent of directors felt that board decisions are consistent with their personal values; while intentions are strong to behave ethically and serve sustainable development, actions to give effect to these intentions lag significantly. Respondents indicated that the top impediments to courageous leadership for sustainable development related to personal issues of maintaining the image of being a director, fear of appearing weak, fear of being a lone voice, and bowing to board-colleague peer pressure.

Jan 1, 2014

By T. Nesane, S. S. Mnyakeni-Moleele, L. C. Murulana

The effectiveness of two synthesized ionic liquids, 1-(benzyloxy)-1-oxopropan-2-aminium 4-methylbenzenesulfonate (1-BOPAMS) and 4-(benzyloxy)-4-oxobutan-1-aminium 4-methylbenzenesulfonate (4-BOBAMS), were evaluated for mild steel corrosion inhibition in 1.0 M hydro-chloric acid solution, using electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP), and gravimetric techniques. Organic moieties responsible for the adsorption process on mild steel surface were investigated using Fourier transform infrared spectroscopy (FTIR). Gravimetric analysis revealed that the inhibition efficiency of 1-BOPAMS and 4-BOBAMS increased with concentration, with maximum inhibition values of 90.32% and 97.91%, respectively, at the highest concentration of the inhibitors. Gibbs free energy (ΔG°ads) values indicated a strong interaction between the mild steel surface and the molecules of the ionic liquids, and that the adsorption process was spontaneous. These values also show that the inhibitive nature of ionic liquids against mild steel corrosion is caused by a mixedtype of adsorption film formed on the steel surface. The Langmuir adsorption isotherm was used to describe the adsorption of ionic liquid molecules onto the mild steel surface. Polarization curves showed that 1-BOPAMS and 4-BOBAMS have a similar effect on both the anodic and cathodic half-reactions, indicating that they prevent the dissolution of mild steel through both physical and chemical process. Nyquist plots were defined by incomplete semicircle capacitive loops, showing that the charge transfer mechanism controls the corrosion of mild steel in acidic solution.

Apr 1, 2021

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 D. N. Esfahani, K. Khazen, M. Mohammadi

Electrowinning is one of the nickel recovery processes from solutions obtained from the leaching of nickel sources. Every year significant amounts of nickel products are used in various industrial processes and daily life, such as catalysts or batteries, which are a valuable source of nickel for recovery. Nickel purity is also very important in the electrowinning process, because the amount of impurities in nickel such as sulphur, if greater than 100 ppm, make it unsuitable for use in catalysts and plating. Because sulfur is intrinsic to the sulphate electrowinning system, we needed to investigate parameters that can affect the quality and purity of nickel. In this regard, experiments were performed in static and circulating electrowinning processes. A monitoring and circulation system was designed and built to measure voltage, current and temperature as well as to circulate the solution in the system at a specified rate. It was then observed that nickel ion concentration, pH, using the circulation system and additives, were factors affecting the purity and quality of nickel, and in the best case the amount of sulphur in nickel was below 100 ppm. Keywords: Nickel, electrowinning, sulphur impurity

Jan 1, 2020

By L. Hekkala, J. Ollila, J. Keihäs, P. Mäkelä

The Outokumpu Steel Belt Sintering (SBS) Technology is used for manufacturing chromite pellets that are charged into a smelting furnace for ferrochromium production. One of the main elements in successful furnace operation is the control of gas flows inside the furnace, giving improved temperature distribution in the bed during the process. Computational Fluid Dynamics (CFD) gives excellent opportunities for studying these phenomena. An investigation using CFD can be performed relatively fast. For example, implications of different configurations can be studied within a day and an optimum design chosen. Therefore, Outokumpu Technology has developed a Steel Belt Sintering Model (SBSM), which takes advantage of a commercial CFD code. Each main physicochemical event occurring in a steel belt sintering furnace is incorporated independently in the SBS model as a sub-model, enabling every event to be studied separately. The commercial CFD code solves mass, momentum, species and energy equations for determination of the gas flow, composition and temperature. In addition, the Outokumpu SBSM takes into account the moving pellet bed, drying of pellets interms of water content, coke combustion, oxidation and reduction of chromite and the decomposition of carbonates and silicates. During the development of the model, numerous laboratory-scale tests were performed. The sub-models were validated against the laboratory tests. The reliability of the Outokumpu Steel Belt Sintering Model was validated against a pilot-scale batch-sintering furnace by comparing the modelling results against measurements. The aim of this paper is to give a brief presentation of the Outokumpu steel belt sintering model by showing some general modelling examples. Emphasis has been placed on demonstrating some of the main features of the model.

Jan 1, 2007