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Paper written on project work carried out in partial fulfilment of B. Eng (Metallurgical Engineering) degree Electrowinning is an attractive method to recover gold from the relatively concentrated aurodicyanide solutions produced by the elution of loaded carbon, provided that the plated gold can be easily removed using high pressure water sprays. In practice, difficulty with the removal of the gold is occasionally experienced and has been correlated with the presence of high concentrations of copper in the eluate. In this work, the influence of copper on the electro-plating of gold was further investigated using a laboratory electrowinning cell with a rotating disc cathode, polarization, and adhesion tests. It was found that the reduction of copper will compete with gold electrowinning at high copper tenors and that the adhesion of the precipitated gold is also increased under these conditions. Keywords: reduction, adhesion, morphology, current efficiency, limiting current.

Jan 1, 2004

By B. Friedrich

In a German governmental funded three-year research project, a closed loop recycling process for Nickel-Metalhydride-Batteries (NiMH) is under development. Today the discarded batteries are used in the steel industry as a cheap nickel source. Cobalt and rare earth (RE) are slagged and lost for reuse. The entire value of the metals in discarded Ni-MH is estimated to be 4?-4.5 ?/kg. Spent NiMH-batteries containing 36?42 per cent Ni, 3?4 per cent Co and 8?10 per cent rare rarth (Ce,La, Pr, Nd). The dismantled and processed NiMH-batteries are melted in a DC electric arc furnace producing a nickel-cobalt alloy and a slag phase highly enriched with RE-oxides. The key to success in this process is to find a suitable slag system, which ensures best separation of NiCo-alloy from the rare earth oxides and high concentration of RE in the slag. Different oxidic and halogenic slag systems are investigated in the melting process. So far a slag system based on 65per cent CaF2 and 35 per cent CaO delivers the best separation of the two phases and metal yields. A slag with a composition of 20?25 per cent La, 13-16 per cent Ce, 1.5?2.5 Pr, 4.5?6.5 per cent Nd is obtained and further treated to misch metal hydro-/electrometallurgically. The first results of the influence of rare earth oxides on the density of CaO-CaF2slag system are shown at 1600°C. Keywords: battery recycling, CaF2, CaO, rare earth oxides, slag characterization, density measurement

Jan 1, 2004

The processes by which particles and bubbles interact capture many of the central concepts of colloid science and hydrodynamics. This area of research embraces hydrodynamics, interfacial(including capillary) forces, particle and bubble behaviour and solution chemistry. In this review, we discuss collision, attachment and stability efficiencies. We deal with the identification of a flotation ?domain?, the deformation of a bubble surface upon interaction with a solid surface, the kinetics of three phase contact line expansion and the determination of attachment efficiencies through to the direct measurement of bubble-particle interaction forces. We have recently carried out a test of collision theory where the latter embraces both inertial and centrifugal forces. The real challenge is now to quantitatively describe the behaviour of real systems and to incorporate a reliable description of the behaviour of particles in flotation froths. The approach described is very robust when applied to flotation, both from qualitative and quantitative points of view, providing an intellectual foundation for understanding this complex process in separation science and technology.

Jan 1, 1999

By M. Syamujulu

In 1994, Nkana smelter commissioned a multimillion US Dollar Chilean Teniente converter (CT) in its operations in order to improve its smelting technological base. The main objective was to reduce the overall smelting energy costs and increase the sulphur capture for sulphuric acid production to support the company?s leaching operations at Nchanga tailings leach plant. A decade of CT operations have since ensued following its installation and start-up. This paper provides a technical and operational audit of the performance of the CT in the first 10 years of its operations at Nkana smelter.

Jan 1, 2005

Council for 2003/2004 President T.R. Stacey President-elect F. M. G. Egerton Vice-presidents Senior W. H. van Niekerk Junior R.P.H. Willis Immediate Past-president S.J. Ramokgopa Honorary Treasurer J.A. Cruise

Jan 1, 2004

By A. Swanson

The Australian coal industry has been subdued in recent years and only a few new plants have been constructed, but the drive for greater efficiency has seen continued technological developments. The paper lists the new plants and major upgrades, plus summarizes technical developments in the areas of dense medium processing, fine coal treatment, froth flotation, dewatering and on-line analysers.

Jan 1, 2001

By Y. M. Zhao

The separating performance of a pilot dry beneficiation system using a gas-solid fluidized bed was investigated with coal from South Africa. The coal used for the study has a low inherent moisture content, a moderate ash content, a moderate volatile content, a low sulphur content and a high calorific value. Its washability is moderate. Experimental results show that the separating quality of the fluidized bed drops gradually as the feed-coal particle size decreases. The probable error, E, values for 50?25mm, 25?13 mm and 13?6 mm coals were 0.04 g/cm3, 0.06 g/cm3 and 0.09 g/cm3, respectively. The cause of the differences in separating characteristics was analysed by particle dynamics and numerical modelling. Furthermore, the pilot fluidized bed was employed to separate 50-6mm coal. In this experiment the coal ash content was reduced from 23.74% to 11.79%, with a probable error, E, value of 0.07 g/cm3and a recovery efficiency of 98.26%. This indicates that the fluidized bed is applicable to the separation of coal from South Africa and has good separating performance and wide applicability. Keywords: feed-coal particle size; gas-solid fluidized bed; dry coal beneficiation; numerical simulation.

Jan 1, 2010

By Bjørn Nilsen, Werner Stefanussen

The construction of the Guaigui Multipurpose Project includes a 74 metre high concrete face rock fill dam, a 350 metre long diversion tunnel and a 350 metre long spillway tunnel. The topography in the project area is very steep, and the rock masses are characterized as soft rocks. The stability of the 80 to 100 metre high dam abutments and the excavation of the tunnels in soft rock conditions have caused various challenges and problems to be solved. Limited pre-investigations have called to a great extent for estimation of parameters for the stability calculations based on experience. The preliminary calculation of the stability of the planned rock slope above the spillway intake platform has been carried out by conventional partial factor methods and by use of a computed based Slide Program. The two methods of calculation give different results , and that rock support is necessary to obtain an acceptable factor of safety for a slope inclination of 52o. The input parameters for the rock mass characteristics need to be verified for the permanent calculations.

Jan 1, 2006

By J. P. Bergh

The advent of low-quality export coal demand has brought a new range of possibilities to the South African coal industry. Products that traditionally were only of value to the domestic or combustion industry sectors now have the potential to be exported, with only minor amounts of upgrading required through beneficiation. Comparatively high steam-coal export prices can be obtained for lowquality export coal, which enhances the economic feasibility of expanding low-quality thermal coal exports. There are, however, increasing concerns about the feasibility of lower quality thermal coal exports and the broader implications. These concerns relate to the environmental impact of low-quality thermal coal production for export and the inherent threat to the security of domestic thermal coal supply in South Africa. Against this background, this paper serves to explain the extended value chain in the production of export coal. The technical and economic advantages and disadvantages of low-grade exports versus coal production for domestic use are evaluated. The value chain estimation is calculated by the beneficiation modelling and characterization of two coals. Based on the value estimation, the lowgrade export production scenario, and finally the modelling of potential pollutant distribution, are described. Keywords coal beneficiation, techno-economics, thermal coal, dense medium processing, dry processing, fine coal processing, environmental impact.

Nov 1, 2013

By A Weber, L MacNamara, H Schreiber

Design and development of the world?s largest flotation cell was completed in 2002. This was the first 257 m3 flotation cell installed in the mineral industry and represents a major development in the design of larger flotation cells. This cell has a 50% increase in volume over the widely installed 160 m3 WEMCO® Smartcell? flotation machine. In the next few years it is anticipated that 257 m3 flotation cells will be incorporated into rougher-scavenger flotation circuits in many more world class copper sulphide concentrators. The prototype 257 m3 cell, No.250 Smartcell? flotation machine was installed at Minera Los Pelambres in the front of Row 1 in the existing rougher flotation circuit. This cell is followed by nine No. 130 Smartcell? flotation cells. After the successful development phase, this unit has been incorporated as part of a row of No. 250 Smartcell? flotation machines at Minera Los Pelambres. A key to the successful development of the equipment has been the emphasis placed on fundamental hydrodynamic scale-up criteria. Hydrodynamic factors include superficial gas velocity, water (pulp) circulation through the draft tube, and pulp mixing (distribution) characteristics. This paper will review the scale-up criteria of the No. 250 flotation cell, and present a case study of the in-plant equipment testing. The case study will document the metallurgical and hydrodynamic performance of the machine. It will also illustrate the economic benefits derived by incorporating larger flotation cells in a modern copper sulphide concentrator.

Jan 1, 2007

By H. Kose

In this research, a model quarry with an annual production capacity of 1 000 000 tonnes has been studied for both pit and hillside quarry cases with constant overall slope angle and variable bench slope angle, considering road grades of 8 per cent and 10 per cent. First, technical requirements have been determined and then the effect of production parameters, such as hole diameter, type of quarrying (pit or hillside) and road grade, on the cost has been investigated to determine bench height. Based on the results, it has been concluded that hole diameter has to be kept large in both pit and hillside quarrying to reduce drilling unit costs. In addition, in order to take advantage of gravity and reduce transportation cost, it has been suggested that bench height and road grade have to be kept high and low respectively in the case of hillside quarrying (downhill transportation) while, in the case of pit quarrying (uphill transportation), bench height and road grade have to be kept low and high respectively, in order to transport the blasted material to a lower height and distance, to save energy, thus decreasing the transport cost. Keywords: Quarry, pit, hillside, road grade, bench height

Jan 1, 2005

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. Thomas, I. N. M. Nday

"*Paper written on project work carried out in partial fulfilment of BSc.Eng (Mining Engineering) degreeThe optimization of the cycle time to increase productivity at Ruashi Mining was an on-site project investigation conducted from December 2017 to January 2018. The main objective of the investigation was to determine the actual cycle time components. These comprise the queuing time, loading time, hauling time, and dumping time of ADTs (articulated dump trucks). Data was also collected on two hydraulic shovels to identify where these could be optimized. The actual cycle time obtained was compared to the theoretical cycle time to ascertain the constraints, which affect productivity. By applying Systems Thinking to the cycle time, man-made constraints of the actual cycle time were identified and recommendations to mitigate them suggested to optimize the cycle time. However, rainfall is a natural constraint that adversely affects the actual cycle time, and which cannot be mitigated.In addition, both the theoretical and actual cycle time were analysed, as well as the theoretical and actual productivity for the year 2017. Based on the findings, conclusions and recommendations were made to optimize the cycle time. IntroductionThe aim of the project was to increase Ruashi Mining’s productivity by 39%, from about 7.537 Mt of broken material mined to 12..367 Mt targeted in 2017.BackgroundRuashi Mining is a copper (main commodity), cobalt (by-product), and acid producer located in the Democratic Republic of Congo (DRC), 10 km from the city of Lubumbashi. Figure 1 shows the location of the Ruashi Mining open pit.Ruashi Mining started production in 1911 and in 2005 the mine was registered as a DRC company owned by Metorex Group Limited. In November 2013, the Chinese company Jinchua Group International Resources Co. Ltd. bought a majority stake in the business. Ruashi Mining currently produces 38 000 t of copper and 4400 t of cobalt per annum. The company has contracted NB Mining (a contract mining company) to transport its ore. To optimize the productivity of the mine, considering ore flow delivery at Ruashi Mining, the cycle time is the indicator used in this project. The cycle time components were recorded on site using a stopwatch."

Jul 1, 2019

By S. R. Sankaranarayanan, T. Sowmya

Slags and fluxes used in metallurgical processes are typically made up of oxides (especially silicates), with additions of fluoride and carbonaceous matter. Despite the efforts made towards understanding the role of slags in various processes, little information is available on the structure of these slags. Tools such as X-ray diffraction, spectroscopy, and electron microscopy could be used for this purpose. This paper is based on an ongoing spectroscopic and structural investigation of slags and related materials. Spectroscopic studies of various commercial slags (predominantly ferrous), ores, glass and related materials, covering a wide range of compositions, have been carried out to understand the structure. The infrared spectra were recorded, predominantly, using FTIR spectrometer (Bruker IFS 66U) spanning 4000 to 100 cm-1using the KBr pellet method. The resolution was typically 4 cm-1. The spectral outputs have been compiled in terms of bands present (corresponding to different bonds) and then compared with the typical bands expected for such bonds. Efforts are in progress to identify the trends with respect to the chemical composition?for example, the effects of SiO2, Al2O3, and non-bridging oxygens. Data obtained so far indicate some trends such as (i) a shift in the Si-O band (969 to 1099 cm-1) towards a higher wave number with increasing silica content (almost 2 to 92 weight percentage) and (ii) further strong shifts as a function of the alumina content. These are being further investigated structurally and in terms of chemical composition/parameters. Keywords: slags, silicates, structure, spectroscopic analysis, shifting of bands

Jan 1, 2004

By M. Görnerup, M. Hayashi, S. Seetharaman, C. -Å Däcker

The mould flux plays a crucial role in the continuous casting operation of steel due to its multi-functional assignment as lubricator and heat flux controller. In reality, the commercial fluxes can fall short of the expectations of the operator. In such cases, the performance of the mould flux reduces production throughput in the casting machine. This paper presents the results of a study of two different commercial mould fluxes in continuous casting of steels. The results of online sampling during casting, as well as off-line measurements in the laboratory, are presented. Mould flux powder and slag samples from the caster have been characterized with respect to melting behaviour, interfacial tension and thermal diffusivity, using various measuring techniques. An experimental technique has been developed in order to simulate the melting behaviour of a flux in the mould, which has been found to be useful for qualitative studies. A cross-sectional view of different powders reveals that up to four different material layers may exist in the bed: a loosely packed powder layer, sintered layer, semi-solid layer and liquid slag layer. It is found that the melting rate of the mould flux is dependent on the liquid slag layer thickness. Thus, in a continuous casting operation the melting rate is likely to be non-uniform with position in mould due to the difference in liquid slag layer thickness. Mould slag composition is found to be influenced by the starting powder for as long as 30 min, representing a large part of the first heat casting time. Observations of gas formation indicate that interfacial reactions between the steel and slag take place. Keywords: continuous sacting, mould flux, mould slag, properties

Jan 1, 2004

By O. Nyandoro, K. Khoza-Shangase, M. Madahana, N. Moroe

"Occupational noise-induced hearing loss (ONIHL) is classified as the leading work-related disability in the mining industry. ONIHL has a negative impact, on not only the health and occupational productivity of affected individuals, but arguably also on the country’s mining industry and economy. Hearing conservation programmes (HCPs) are an effective strategy in the management of ONIHL. However, current literature indicates that HCPs are not achieving the anticipated and desired outcomes in the South African mining sector despite the efforts focused on the management of ONIHL. Therefore, the purpose of this study is to propose the use of a feedback-based noise monitoring model as a tool for monitoring and managing ONIHL in the South Africa’s mining sector. This model is a basic static feedback model with practical applications such as estimating, monitoring. and providing quantitative information to aid miners, mining administrators, and policy-makers in decision-making around HCPs. Additionally, the model could form part of an early intervention and management strategy for ONIHL in the workplace. The strength of this model, although currently static, is that it encompasses all the pillars of HCPs and takes into account the policies concerned with the management of ONIHL in the mining sector. IntroductionHazardous noise levels (above 85 dBA) in the workplace place exposed employees at risk of developing a disabling occupational noise-induced hearing loss (ONIHL). ONIHL is the ‘partial or complete hearing loss in one or both ears as a result of one’s employment’ (Nandi and Dhatrak, 2008, p. 1). This type of hearing loss develops gradually as a result of being exposed to continuous or intermittent high levels of noise over a long period of time (McBride, 2004; Patel et al., 2010; Rappaport and Provencal, 2001). A hearing threshold below 40 dBs is classified as a disabling hearing loss (Yadav et al., 2015), resulting in a hidden condition that does not readily manifest itself (Tye-Murray, 2009, p. 3). Dugan (2003) describes disabling hearing loss as the ‘most prevalent, least recognized and least understood physical disability’, while Copley and Frederichs (2010) and Hermanus (2007) argue that permanent disabling hearing loss is a major contributor to the global burden of disease on individuals, families, communities, and countries."

Jul 1, 2019

By J. Janssens, B. Coletti, S. Smets, J. Plessers

The oxygen activity of the ladle slag determines the reactivity towards the steel during ladle treatment. Therefore, the in situ measurement of the oxygen activity of slags can be an important tool. The applicability of an electrochemical sensor is examined in this work. The sensor measures the electromotive force (EMF) that is established between a sample of the slag phase that is immersed in the liquid steel bath and a reference system (Cr/Cr2O3). Industrial and laboratory experiments demonstrated the capability of the sensor to detect the influence of the slag components on the measured oxygen potential. Comparison of the measured values with thermodynamically calculated values shows that the measured oxygen activity is systematically too low. This was attributed to a reaction of the steel with the slag sample. To investigate this, further lab tests were performed where the slag oxygen activity was measured after the slag had been equilibrated with the steel. The measured values were dependent on the oxygen activity (aO) of the steel. For industrial applications, it is concluded that the aO of the steel should be known and that this value is necessary for the interpretation of the measured values. Keywords: low carbon steels slags, slag oxygen activity, on-line sensing, thermodynamic evaluation.

Jan 1, 2004

By John V. Simmons, Peter J. Simpson

Excavated slopes in open pit coal mines are designed to be as steep as possible consistent with stability and safety requirements. Slope failures occur for many reasons, including oversteepening. This paper is concerned with slope design and excavation experience in the Bowen Basin coalfields of central Queensland (Figure 1), [ ]

Jan 1, 2006

By M. Sanchez, C. Morales, J. Palacios

The slag produced in the Peirce Smith converters at the Ilo smelter of Southern Peru Copper Corporation has shown a wide range of magnetite content, which introduces an additional problem in the smelting units due to materials? recirculation. However, the operation data analysis and the application of thermodynamic concepts have made it possible to produce slag with magnetite content between 18 and 20%. The results have suggested that matte grade enhances magnetite formation while silica controls its precipitation, and they are also influenced by the increasing temperature of the slag. Thus, in order to obtain the required magnetite content in the slag, matte grade is gradually enriched in equilibrium with slag containing from 25 to 32% silica.

Jan 1, 2004

By R. L. Gibson

Manpower competencies in the mining, minerals processing and energy industries in South Africa into the next century will, to a large extent, derive from the nature and quality of the teaching which pupils receive at school. This paper provides an overview of the current developments towards a new National Curriculum in South African Schools and highlights areas in which the Minerals Industry might provide input into this process.

Jan 1, 1997