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By A. Della Rocca, P. Jonker, B. Henning

Successful prediction of the collection efficiency of cyclone separators is a necessary step in cyclone design and verification. Aside from standard empirical relations, CFD modelling is widely adopted to supplement the design of cyclone units in relation to the desired separation performance. Nevertheless, effective adoption of numerical modelling is sometimes prevented by large modelling errors, especially for small size particles which are more subject to turbulence effects than larger particle classes. In the past, this motivated the adoption of more refined turbulence modelling approaches, such as large-eddy simulations. These approaches provide greater insight into time dependent behaviour, while leading to larger computational cost with respect to more standard approaches. In this paper, an effective Eulerian-Lagrangian Reynolds-averaged Navier-Stokes (RANS) approach is investigated, which is able to predict the complete separation efficiency curve with satisfactory accuracy, without requiring prohibitively long computational times. An assessment of the proposed approach is carried out against experimental data from large laboratory scale cyclones, in the form of mean and fluctuating velocity profiles from LDA measurements (Hoekstra, 2000), as well as with respect to the experimental separation curve (Zhao, 2005). The final application to a full-scale industrial cyclone unit is then carried out with the aim of tuning the cyclone design to the separation efficiency curve as required by downstream processes. Keywords: Cyclones, separation, CFD, RANS, RSM, Lagrangian

Jan 1, 2020

By A. F. Khan

The CSense advanced process control (APC) solution?s main objective was to improve the stability of the pH in the first stage leach process thereby improving nickel and iron extraction efficiencies and reducing the base metal (BM) content in the platinum group metals (PGM) concentrate. By improving the stability of the control of the pH on the first stage leach it had the corresponding effect of improving the Ni extraction efficiency by 0.5% and the Fe extraction efficiency by 3.3%. The system relieved the operators of many decisions that were virtually impossible to make given the complex, variable and real-time nature of the processes in their charge. On the operational side, the operators understand the APC system and they trust it. Another benefit is the reduction in pH peaks in the autoclave, which can oxidize certain elements whereby they become difficult, if not impossible, to leach. These elements go right through the process and end up contaminating the PGM solids, with the result that the entire batch has to be recycled through a lengthy and costly processing pipeline.

Jan 1, 2009

The variety and sources of sampling errors have been studied since the late 1800s, but the pioneering work of Pierre Gy in the 1950s provided insights into sampling as an error generating process. Total sampling variance is a measure of the total sampling error, but disaggregating the variance into its component parts is problematical. Ten sources of error and error generating processes have been identified, some of which can be eliminated through rigorous application of the principle of correct sampling. Others can only be minimized but never eliminated. Three principal questions relating to the appropriate mass of a sample, the fragment size of the sample and the size of the associated error are addressed. These questions relate principally to the Fundamental Error (FE), the only error that can be estimated before the sampling event. Aspects of constitutional and distributional heterogeneity are examined, as are the essential components of Gy?s formula including the shape factor (?), the granulometric factor (g), the mineralogical composition factor (c), and the liberation factor, l. Applications of Gy?s equation to the problems of sampling in the minerals industry are explained using real-life examples. The approach to sampling taken by Pierre Gy provides an excellent inferential relationship between the mass of material to be sampled, the size of the fragments being sampled, and the relative variance of the sampling error. It also provides solutions for three of the main problems associated with the Theory of Sampling.

Jan 1, 2007

By S. M. Brabyn

The wear in mild steel pipelines used to convey rod-milled waste backfill was determined and then compared with that obtained using a laboratory rig designed to simulate the wear condition in slurry pipelines. The relative importance of corrosion and abrasion was investigated under various conditions of water quality and particle size distribution. The laboratory rig was then used to evaluate other possible materials of construction for backfill pipelines. A preliminary assessment of the economic viability of pipelines made of alternative materials is included.

Jan 1, 1988

By H. J. Le Roux, W. B. Drummond

1. INTRODUCTION We have a moral responsibility towards the world to reduce the harmful deposits we emit into the environment arising from beneficiation technologies. Industry has not willingly spent money to limit these emissions because it affected their profit margin with the end result of emitting harmful elements into the environment. Governments have thus rightly stepped in and enforced systematic reduction of these emissions through legislation. In the past beneficiation of sulphur bearing ores was typically done through hydro-metallurgical concentration, smelting, followed by Sulphur removal by converting processes like the Pierce Smith converter. The latter two processes emitted substantial quantities of Sulphur into the atmosphere. Spiralling costs and legislation have resulted in the quest to develop more efficient and environmentally friendly processes to achieve the same end results. New hydro-metallurgical processes like the ActiVox process has completely eliminated the pyro-metallurgical processes. Kansanshi are also operating a similar process. It however elicits other ground water and spillage pollution hazards and problems of it?s own. Various improvements has also been made to the pyro-metallurgical stages, examples being combined smelting and converting with the Noranda reactor, the Codelco CMT furnace, one step flash smelting/converting or the Mitsubishi continuous smelting, converting and slag cleaning process. The new converting processes are also normally enhanced using oxygen leading to higher SO2 gas strength with only a marginal increase in off-gas volume. These processes have led to better efficiencies and a more controlled environment that reduces pollution, but does not eliminate it completely. The fact that there are still more than 70 existing Pierce Smith converter plants throughout the world that needs to be replaced or upgraded at tremendous capital cost, means that we will have the environmental problems for some time to come. The need thus exists to cost effectively get these existing plants into a state where they meet the new environmental regulations, community and safety requirements. This paper will concentrate on just one aspect of this quest, i.e. reduction/removal of off-gasses emanating from the converting of non ferrous sulphur mattes to achieve higher or specialised grades of refined metals.

Jan 1, 2005

By H. Ramazi, A. Amini

"This article is devoted to the introduction of a new technique of electrical resistivity data processing called residual resistivity (RR). We define RR as measured resistivity minus background resistivity. To determine the background resistivity, the data acquired from electrical resistivity measurements along a given survey line is evaluated, and then an equation is fitted to the data corresponding to a chosen measurement station as a function of current electrode spacing (or array length). The RR technique was applied to several synthetic models to compare the conventional resistivity inversion of each model with its RR-based inversion. A case study was carried out in a karstic area in Zarrinabad, Lorestan Province, western Iran, to detect the location and geometry of probable cavities by conventional resistivity inversion and RR-based inversion. The results showed that the anomalous zones are better highlighted in the RR-based inversion images in comparison with the conventional inversion images. In some cases, anomalies detected by the RR-based images were hidden in the conventional method. IntroductionThe geoelectrical resistivity method has been widely used since the early 20th century, and plays an important role in several fields such as groundwater and subsurface mineral exploration, geotechnical and environmental investigations, and archeological studies (Bayrak and Senel, 2012; Candansayar and Basokur, 2001; Fehdi et al., 2011; Hee et al., 2010; Osella et al., 2003; Wilkinson et al., 2010). The goal of geoelectrical resistivity surveys is to determine the distribution of subsurface resistivity by measuring the current-potential difference on the ground surface (Aizebeokhai et al., 2010). In the electrical resistivity method, an electrical current is injected into the ground by two electrodes, called current electrodes (AB), and the potential difference is measured between another pair of electrodes, the potential electrodes (MN). Several methods of interpretation are available for application to electrical resistivity data, the simplest being the graphical interpretation of the apparent electrical resistivity pseudo-sections along each survey line. A second method, electrical resistivity inversion, has been developed to create relatively accurate two- and threedimensional computational resistivity models of subsurface sections (Loke and Barker, 1996; Niwas and Mehrotra, 1997; Nordiana et al., 2014; Oldenburg and Li, 1994; Papadopoulos et al., 2009; Yilmaz and Narman, 2014). In the inversion method, models of subsurface objectives are mathematically inverted to reach optimal solutions subject to prescribed objective functions, constrains, and convergence criteria. A common problem when using the electrical resistivity inversion method is that the inversion model of an electrical resistivity profile may be non-unique because different inhomogeneities in the investigation media can result in the same electrical response (Smith and Vozzof, 1984)."

Jan 1, 2016

By P. Minkkinen, R. C. A. Minnitt

Particle size distribution analysis is important to many industries for assessing product quality, process efficiency, and compliance with contractual standards, while ensuring sample accuracy, and representativeness. Inaccurate particle size distribution results, arising from fines due to excessive handling can lead to penalties and buyer-seller disputes. A non-representative particle size distribution means samples will not accurately represent the chemical components either. Sampling blasthole cuttings poses challenges due to large material volumes, segregation, and uneven settling of particles in dense gold bearing ores. Commonly used sampling methods, such as spear or sectoral sampling, may lack representativeness. Particle size distribution analysis is crucial for evaluating sampling methods by comparing test sample representativeness against a reference standard derived from multiple particle size distribution analyses. Acceptable samples must fall within the 97.5% confidence intervals of the standard; deviations analyses lying outside these boundaries indicate a strong likelihood of segregation errors. A case study demonstrates this approach by using a 6.005 kg benchmark sample to assess two additional samples (1 kg and 5 kg), highlighting particle size distribution’s role in detecting sampling errors and refining protocols. An example of three test samples collected from reverse circulation drill cuttings compared to a standard reference sample is presented to illustrate a quality assurance/quality control procedure for reverse circulation drilling.

Oct 2, 2025

By R. Kuyvenhoven, A. Parbhakar-Fox, X. Prieto, J. Quevedo, L. V. Danyushevsky

This paper presents the results of a study focussed on determining the distribution of cobalt in different types of pyrite of the La Estrella IOCG deposit in Chile. In the IOCG mineral deposits, where copper is the main product, the quantification and distribution of cobalt is required to correctly define the technical and economic viability of recovering cobalt as a by-product. In the La Estrella mineral deposit, seven alteration and mineralisation events were recognised through both optical and automated electronic mineralogical analysis. Of these seven events, five different types of pyrites were identified, each with unique characteristics of the pyrite crystals. Through advanced elemental analysis of these five types of pyrites, it was determined that the concentration and distribution of cobalt within the pyrite crystal is dependent on the mineralisation event. The results indicate high cobalt concentrations in the early pyrite mineralisation events, associated with relatively fine pyrite grains, and cobalt generally occurring in a solid form in the pyrite core. The late pyrite mineralisation event exhibits the lowest concentrations of cobalt, with cobalt predominantly present along the outer periphery of the pyrite. These results are relevant from a metallurgical point of view because the preferential location of cobalt within the pyrite crystal will influence the maximum metallurgical recovery of cobalt. For this, a cobaltiferous pyrite concentrate must be formed which, according to the characteristics of pyrite, must be processed with the optimal solubilisation method. The overall objective is to ensure both good cobalt recovery and a high concentration of cobalt in the leach solution resulting from pyrite leaching. Keywords: Cobalt, pyrite, IOCG, copper, metallurgical recovery, solubilisation, Chile

Jan 1, 2020

By L. Makua, K. Langa, Ndlovu. S., C. Saguru

"Global demand for the three platinum group metals (PGMs) Pt, Pd, and Rh has been steadily growing due to their widespread use in emission control, industrial catalysis, and numerous other applications. The primary supply of PGMs is currently the mining industry. However, legislative, operational, and environmental challenges faced by many mining operations result in erratic supply patterns and deficits for these three metals. Naturally, recycling scrap material to recover Pt, Pd, and Rh has therefore aroused research interest in the scientific and engineering communities. Given that the majority of the global demand for these three metals is driven by emission control devices, autocatalytic converters are therefore a significant source of already processed and beneficiated PGMs for recycling.Although pyrometallurgical processes dominate the recycling industry, hydrometallurgical processes may offer certain advantages, chief among these being lower emissions and reduced energy consumption. In this investigation, scrap converter material was leached in acidic chloride media and the leach liquor subjected to solvent extraction and cloud point extraction (CPE) to recover the PGMs. The recoveries for Pt and Pd using Alamine 308® dissolved in kerosene with decanol as a modifier were 95% and 81%, respectively. The maximum recoveries using CPE after complexation with 2-mercaptobenzothiazole (2-MBT) in the presence of Triton X-100 and tin (II) chloride dihydrate as a reductant were 97% for Pd, 96% for Pt, and 91% for Rh. This demonstrates that CPE, although relatively new, may have some potential as a breakthrough PGM recovery technology. IntroductionPlatinum group metals (PGMs) have found a wide variety of applications in different industries due to their chemical, catalytic, and physical properties. PGMs are essential in automobile emission abatement, petroleum refining, and the pharmaceutical and electrical industries (Carabias-Martinez et al., 2000). However, the abundance of PGMs in the Earth’s crust is low and their primary sources are fast depleting (Crundwell et al., 2011).The high demand for PGMs, together with social, economic, environmental, and political aspects related to their production, has led to concerns about their future supply. This has resulted in renewed interest in recycling end-of-life material. PGM supply from recycling has doubled over the last decade, and currently contributes 22% to global supply (Johnson Matthey, 2016). This is in part due to the environmental, social, and operational challenges associated with mining of PGMs. For example, labour unrest, energy cuts, declining commodity prices, and declining ore grades have collectively made the mining landscape economically challenging (KPMG, 2015). On the other hand, the high content of PGMs in secondary sources makes their recovery from the increasing quantities of waste products important from a resource conservation viewpoint. Moreover, PGMs obtained through recycling have been demonstrated to have a 1% environmental cost from a life-cycle perspective, whereas PGMs obtained from mining contribute the remaining 99% of environmental cost (Bossi and Gediga, 2017). Sustainable resource recovery and the economic incentive of recycling have therefore been major drivers to justify investment in PGM recycling. The autocatalytic converter industry accounts for about 70% of the global consumption of these metals (Johnson Matthey, 2016) and therefore recycling spent converters has become a major source of Pt, Pd, and Rh (Figure 1)."

May 1, 2019

By Ernst-Ulrich Reuther, Alexander Donmen

Mine ventilation in the German coal mining industry is concerned mainly with problems of thermal environment arising from greater depths and with increasing emission of methane gas. The development of computer techniques over the past ten years for solving these and ancillary problems is reviewed. The emphasis from a planning and control point of view falls mainly on ventilation network calculations, temperature predictions and advance estimates of methane emission.

Jan 1, 2014

By U. C. Galimidi, J. M. Stewart, A. J. Van Rensburg

The effect of body movement on convective heat transfer from a man performing a block-stepping task was investigated experimentally by direct measurements of convective heat transfer. A series of experiments was conducted in which a nude man was required to stand at rest or to block step at 12 and 24 steps per minute. Wind speed, which was kept constant during each experiment, spanned the range 0,5 to 3,5 m/so Air temperature was kept constant at 43 °C in all the experiments. The results showed conclusively that the convective heat-transfer coefficient depends on the stepping rate. The effect of body motion can be regarded as being equivalent to an increase in the velocity of the free stream. The equivalent increase in air speed was found to be 0,36 and 0,77 m/s for 12 and 24 steps per minute respectively. Data from various sources, including the present study, indicate that wind speed should be increased by about 0,30,0,55, and 0,80 m/s to account for low, moderate, and vigorous body movements respectively. These findings are of direct relevance to the practical assessment of heat stress.

Jan 1, 1979

By D. Sethuram, P. G. Koppad, S. Iyengar, R. Shobha

TiB2 and CeO2 particle-reinforced Al6061 hybrid composites were manufactured using stir casting and hot rolling techniques. The base alloy and composites were hot-rolled at 500ºC and a 50% reduction was achieved through 12 passes. The effect of varying TiB2 and CeO2 particle additions on the microstructure and mechanical properties of the Al6061 matrix was studied. Scanning electron microscopy showed uniform dispersion of both the reinforcements, with good interfacial bonding. Microhardness and tensile properties like yield and tensile strength were found to be higher for hybrid composite with 2.5% TiB2 and 2.5% CeO2 compared to Al6061 alloy and other hybrid composites. The increased tensile strength is attributed to good dispersion and interfacial bonding between the particles and Al6061 matrix. Fracture analysis using a scanning electron microscope revealed ductile fracture for the Al6061 alloy and mixed characteristics of ductile-brittle fracture for hybrid composites

Oct 1, 2021

By N. C. Steenkamp

Lightning has been observed in dust clouds following open-pit blasting. It is proposed that the occurrence of this phenomenon is related to the physical composition and characterization of the mineral fines that comprise the bulk of the dust cloud. Silicate minerals, which are susceptible to fine fracturing during blasting, generate the initial charge. This is further enhanced by collisions and friction during the turbulent upcast in the post-blast dust cloud. Varying size fractions result in different rates at which these particles drop out of suspension and create a secondary temperature gradient. This results in the creation of two charged zones and increases the potential of developing a discharge in the form of lightning. The ideal prevailing meteorological conditions need to be windless to minimize the effect of particle dissipation and have sufficient moisture toenhance the potential of generating lightning.

Apr 14, 2024

By W. J. Whiten

"Models of cone crushers and vibrating screens are described. These models have been constructed from actual plant data using a systematic model-building technique. Included in this technique is regression analysis using multi-dimensional spline functions.The models have been used to simulate complete crushing plants and hence to design and evaluate a control system for crushing plants."

Jan 1, 2014

By K. Hodgson, Cook. N. G. W.

Most structures are designed so that the possibility of failure is eliminated. However, some degree of failure in the rock around deep mine excavations is inevitable if mining operations are continued. The presence of failed rock constitutes a hazard the magnitude of which can be predicted by computer models from calculations of the energy change per unit area mined in stopes, or the field stress around service excavations. Empirical relationships between these calculable quantities and the incidence of rock failures and delays associated with them have been established. Experiments on the computer using different layouts enable the mining engineer to select the least hazardous of otherwise acceptable alternatives, and to predict the incidence of damage ahead of actual mining, so that appropriate measures to maintain an adequate degree of safety and productivity can be planned in advance.

Jan 1, 2014

By D. F. Malan, T. E. Oates

A recent experimental pillar extraction project at a UG2 bord-and-pillar mine presented a unique opportunity to compile a new pillar database. Currently, the South African hard rock bordand- pillar mines are designed using the Hedley and Grant formula with a modified K-value. This empirically derived formula was developed for uranium mines in the Elliot Lake district of Canada. The use of this formula for the design of pillars in South Africa is questionable. Very few pillar failures have nevertheless been observed and its current calibrations for the various reef types are possibly too conservative. A new UG2 pillar database of 66 pillars, of which seven are classified as failed, was compiled by the authors. This enabled a revised ‘first-order’ calibration of the K-value for the Hedley and Grant formula. The new estimated value for the UG2 is K = 75 MPa. This gives a pillar strength that is more conservative than the PlatMine formula. This work should nevertheless be considered as only a preliminary calibration as the database was small. Further work is also required to determine whether the exponents in the formula for the width and height parameters are appropriate for UG2 pillars.

May 3, 2023

By E. van Steen, G. M. Leteba

Optimizing the catalytic performance of multimetallic nanoparticle (NP) catalysts demands a concrete understanding of their design, while preferentially deploying wet chemical synthesis procedures to precisely control surface structural properties. Here we report the influence of reductants such as hydrogen-rich tetrabutylammonium borohydride (TBAB) and carbon monoxide-rich molybdenum carbonyl (Mo(CO)6) on the shape and morphological evolution of Pt-based binary (PtNi and PtCo) and ternary (PtNiAu and PtCoAu) nanostructures derived from a homogeneous solution of aminebased surface active agents (surfactants) in a high boiling point solvent. We successfully synthesized nanostructures exhibiting well-defined and composition-controlled surfaces deploying a one-pot synthetic approach. The development of the surface properties was, however, observed to be alloyspecific. The resultant highly monodisperse alloy NP with narrow size distributions and facet-oriented surfaces are expected to display enhanced functionality as catalysts for utilization in specific chemical reactions.

Jun 1, 2021

By A. J. Dickson, A. M. Starfield

This paper reviews the progress made to date in the development of computer models of heat and moisture transfer from rock surfaces to the ventilating air in deep-level mines. The application of these programs to ventilation planning and design is discussed.

Jan 1, 2014

By L. Godfrey, Z. Nontso, F. Magweregwede, B. Maphalala, S. Khan

The aim of this paper was to establish if mineral resource scarcity is a driver for South Africa to transition to a circular economy. The project objectives were achieved by investigating economically viable, and critical or strategic minerals remaining in South Africa, as well as resource scarcity, as a driver for South Africa to transition to a circular economy. The study found that some minerals in South Africa, such as iron ore, lead, manganese, gold, and cobalt have less than 50 years of economically viable mining remaining. At least 18 minerals can be classified indicatively as critical or strategic: aggregates, bauxite, chromite, cobalt, copper, gold, graphite, iron, limestone, lithium, manganese, nickel, phosphorous, platinum group metals, rare earth elements, silver, titanium, and vanadium. The classification was based on the minerals’ economic importance, supply risk, and potential use in the development and manufacturing of emerging technologies. The findings suggest that the scarcity of mineral resources is a critical driver for the country to transition to a circular economy. Other identified drivers include socio-economic factors, climate change commitments, and business objectives. All minerals are non-renewable resources and at risk of depletion, therefore sustainable extraction and use are critical. Priority should be directed at investigating circular economy opportunities and substitutes for commodities at risk of being depleted within the next 50 years. There is an opportunity for South Africa to transition from a minerals export-based model to one that promotes local mineral beneficiation and manufacturing of end products.

Mar 5, 2025

By S. Annavarapu

"Fragment size distributions play an important part in the design and planning of block cave mining operations. Though several methods have been proposed for estimating fragment size distributions in advance of mining, the calibration of these estimating procedures to field measurements has been a challenge. The Block Size Estimator (BSE) program was developed for providing an assessment of primary fragmentation expected in a block cave mine using drill-core piece length data and joint characteristics from the exploration and geotechnical evaluation programmes. In order to validate the results from the BSE program, the drill-core piece length data and the joint characteristics in different rock types from the DOZ block cave mine in Indonesia were used to help generate fragment size distributions in different areas of the mine. The predicted fragment size distributions were compared with the fragmentation observed at the drawpoints during operation of the mine.This paper presents the details of the validation of the fragment size estimates by the BSE program using fragment size distribution data from the drawpoints at the extraction level at the DOZ block cave mine, and the challenges encountered in developing reasonable correlations between the estimated and measured fragment size distributions. IntroductionThe assessment of fragmentation is an important aspect of the design and planning of the block cave mining method, and forms an integral part of the design of the excavations at the extraction level and the selection of material handling systems for transporting the ore to the processing stations. Secondary blasting requirements can also be estimated based on the fragment size distributions developed for the block cave (Laubscher, 1994).Several methods of estimating fragment size distributions in block cave mines have been developed based on joint set parameters estimated from structural data from oriented core drilling campaigns and mapping of available excavations and outcrops. The BCF program (Esterhuizen, 1999) estimates the fragmentation using a combination of empirical, analytical, and rational methods to model the behaviour of materials during the primary and secondary fragmentation processes. The program JKFrag uses advanced tessellation of joint traces to create rock blocks and then generate fragment size distributions (Brown, 2002). Nickson, Coulson and Hussey (2000) presented the details of processing of the geotechnical data from the Mont Porphyre project, including an assessment of block sizes from the data collected on the core logging sheet. The distance between natural fractures was used to create distributions of block lengths, and a distribution of potential block sizes was estimated assuming that the blocks had equal dimensions in all directions. The results agreed closely with the results of the BCF program. Hadjigeorgiou, Grennon, and Nickson (2002) demonstrated the use of oriented borehole data to provide characteristic block size distributions for a mining project using a software package called Stereoblock, which generates a three-dimensional joint network for a given volume and calculates the volumes of blocks created by the intersections of these joints, simulated as circular planes. The distributions of joint orientation and joint spacing generated from statistical analysis of the oriented core data are used for the creation of the Stereoblock model. The diameter of the circular planes representing the joints is determined based on the mean and standard deviation of the joint trace length obtained from scan-line mapping."

May 1, 2019