Search Documents

Council and Standing Committees - 1981/82 President: G. Y. Nisbet. Senior Vice-President: Prof. A. N. Brown. Junior Vice-President: Prof. R. P. King. Honorary Treasurer: Prof. D. G. Krige. Immediate Past President: Dr P. R. Joehens. Members of Council: B. C. Alberts, J. D. Austin, P. T. Fewell, C. E. Fivaz, J. J. Geldenhuys, Dr A. K. Haines, P. N. Harris, H. E. James, C. G. Knobbs, Dr B. K. Love¬day, Dr J. Lurie, C. S. MacPhail, D. G. Malan, J. C. Mostert, G. C. Thompson, Dr H. Wagner. Chairman, Witbank/Middelburg Branch: B. Rohrmann. Chairman, Orange Free State/Klerksdorp Branch: K. F. W. Eick. Chairman, Materials Engineering Specialist Division: G. Pienaar. Past Presidents serving on Council: Dr M. G. Atmore, H. Britten, Prof. D. D. Howat, Dr J. P. Hugo, D. G. Maxwell, Prof. R. P. Plewman, Dr R. E. Robinson, Prof. M. D. G. Salamon, P. W. J. van Rensburg, D. A. Viljoen, P. A. von Wielligh. Standing Committee Chairmen: Constitution, Rules and Policy, Dr P. R. Jochens; Membership, Prof. R. P. King; Training, Career Guidance and Education, P. A. von Wielligh; Journal, Prof. A. N. Brown; Monograph Series, D. G. Malan; Technical Programme - Metallurgy, C. E. Fivaz; Technical Programme - Mining, P. N. Harris; SAIMM Schools - Metallurgy, Dr B. K. Loveday; SAIMM Schools - Mining, J. D. Austin; 1982 CMMI Congress, Dr M. G. Atmore; Awards, Dr P. R. Jochens; Adjudication, Dr P. R. Joehens; Phoenix National Committee, Dr M. G. Atmore; Excursions, J. C. Mostert; Mines and Works, Prof. A. N. Brown; World Mining Congress - National Committee, Prof. R. P. Plewman.

Jan 1, 1982

By M. Wu, X. Zhao

This paper presents an integrated pipeline transport system for thickened coal sludge, which combines pretreatment and pipeline transport with combustion techniques of thickened coal sludge. The pipeline can transport thickened coal sludge with a sufficiently high solids content (about72%?77%) and high apparent viscosity (about 1 000Pa?S?3,000 Pa?S) directly by pipeline having neither use for water nor an addition agent. The transport distance can be as high as 1 000 metres. In particular, the operating principles, key equipment and technical parameters of this integrated system are examined in this paper. The integrated system effectively causes no pollution to the environment because it is completely sealed, and conserves energy over traditional conveyer designs. Keywords: pipeline transport; integrated system; circulating fluidized bed boiler; thickened coal sludge; high solids content

Jan 1, 2007

By F. S. A. de Frey, F. C. Kruger

Personnel management has undergone a remarkable change over the course of the past ten years. Personnel departments have played an increasingly important role, which today requires highly trained people and cannot be adequately served by the lesser qualified officials of yesteryear. Changes in the mining industry that stem from the demand for skilled labour to keep pace with technological developments and the mechanization of mines today demand that emphasis should be placed on the maximum utilization of manpower. Maximum utilization of manpower calls for more scientific and effective methods of recruiting, selecting, training, and placing workers so as to offer them the best opportunities for development and promotion, which naturally ensure a minimum labour turnover and eliminate labour unrest. This can be achieved only if well-qualified and properly trained personnel administrators are prepared to accept the challenge and apply themselves purposefully by assisting line mangement with the attainment of the company's corporate objectives.

Jan 1, 1982

By J-N. Oyourou, R. McCrindle, C. J. S. Fourie

"Many mines in South Africa were inappropriately closed and left unattended during the last century. These old mines are potential sources of environmental pollution and may pose a health risk to local populations, since the surrounds contain elevated levels of toxic elements. Soil from the old Edendale lead mine property in Mamelodi Extension 11, east of Pretoria, which was suspected to be contaminated with lead, was analysed. The mine, which primarily extracted galena, was decommissioned in 1938. During this study, the old mine property and surrounds were screened for zinc and lead using a field-portable X-ray fluorescence (pXRF) spectrometer. The metal concentrations, which ranged from 18 to 7 300 mg/kg for zinc and from 50 to 21 000 mg/kg, for lead, were plotted together with the GPS coordinates to produce a concentration distribution map for lead and zinc. This map revealed three anomalies of unacceptably high concentrations, possibly corresponding to areas where ore had been piled or dumped to waste from the old mine. Thirty-six of the soil samples that were analysed by pXRF on site were selected and analysed in the laboratory using inductively coupled plasmaoptical emission spectrometry (ICP-OES) for verification purposes. The zinc and lead concentrations obtained from the two analytical methods were compared using linear regression analysis. Excellent correlation was obtained between the results from the two methods (r2 = 0.99 for zinc and r2 = 0.95 for lead). IntroductionEarly economic development in South Africa was based mainly on mining. However, these activities left a legacy of approximately 6 000 improperly closed mines scattered throughout the country (SAI, 2009; van Schie, 2012). Due to their proximity to settlements, these abandoned mines may pose a potential health risk to humans and an environmental hazard. Mining activities generate large amounts of waste, mostly in the form of overburden and process tailings, which often contain high concentrations of toxic elements. Bioavailable toxic elements can contaminate crops growing in the polluted area (Kala, 2010; Marwa, Meharg, and Rice, 2012) or eventually migrate and detrimentally affect the groundwater (Rösner and van Schalkwyk, 2000). Moreover, sulfides accumulated in mine waste generate acid minewater (Rösner and van Schalkwyk 2000). Unfortunately, owners of mines, closed before the promulgation of the Minerals Act more than twenty years ago (Act 50 of 1991), avoided the compulsory rehabilitation of the environment enforced by this legislation. Toxic elements, such as lead, which were confined within ores, may become exposed through mining and are therefore more easily mobilized within the environment. Elements essential to human and plant metabolism, such as zinc, when exposed by mining activities, may become hazardous due to elevated concentrations (Aslibekan and Moles, 2003; Wuana and Okiemen, 2011). Humans exposed to potentially toxic metals may experience harmful effects as discussed elsewhere (Nriagu and Pacynar, 1988; Wayne and Ming-Ho, 2005)."

Jan 1, 2019

By Richard F. Link, Jr. Koch

"A mathematical simulation model has been devised to guide the layout of surface or underground mine workings, drill stations, and drill holes that are established in order to search for tabular ore bodies. The ore bodies may be contained within veins, sedimentary beds (including reefs), or other tabular structures.Programmed for a time-shared digital computer, the model contains both stochastic and deterministic variables. Stochastic or natural variables include the number of ore shoots and their sizes, orientations, locations and values. Deterministic or controllable variables include (i) locations and costs of workings (for underground exploration); (ii) drill station locations and costs; and (iii) drill hole azimuths, inclinations, lengths and deflections (if any).For various assumptions about the natural variables, the model is run while the controllable variables arc changed deliberately. Thus, layouts are devised to determine the percentages of the total number of assumed ore shoots found at different costs. In order to choose among the various layouts, cost-effectiveness measures are calculated."

Jan 1, 2014

By R. Asamoah, P. Forson, S. Xu, W. Skinner, M. Zanin

In most auriferous hydrothermal deposits, gold is preferentially associated with pyrite and arsenopyrite minerals, with higher economic gold values noted for the latter and arsenian pyrite minerals. In this paper, surface (Cryo-XPS) and solution (EDTA extraction) analysis were used to characterise pyrite and arsenopyrite minerals under different aqueous conditions involving electrokinetic study and collector interactions to better understand ways of improving the separation of pyrite and arsenopyrite. The evidence showed higher surface oxidation at solution pulp pH values in the range of 4-11 for arsenopyrite relative to pyrite. The observed highest ratio of pyrite to arsenopyrite selectivity was 1.7 at collector concentration of 50 g/t and decreased with an increase in collector concentration. Keywords: EDTA extractable iron, selectivity index, differential flotation, grade engineering

Jan 1, 2020

By J. D. Flint

The geological conditions in the Vierfontein area ~re such that conventional pillar extraction ~stooping) cannot be practised safely or efficiently. Both the open-end lift and the pocket-and-fender methods of pillar extraction have been tried with little success because of problems with roof control and ground stability. The main reasons for the difficulties are the coarse-grained sandstone roof, local weaknesses in the coal seam, and the rate at which the pillars were extracted. The mine has practised bord-and-pillar mining since it started production in 1952, and considerable reserves of coal are contained in the pillars. As an alternative to total pillar extraction, in which hand-loading methods were practised, a system of partial pillar extraction using mechanized-mining methods ~11"modified goaf-line support has been evolved. These remnant coal pillars (snooks) remaining after partial extraction ofthe pillar, together with the installation of 1,2 m" matpacks and a double line of fullcolumn resin roofbolts, ensure control of the edge of the area that has been mined out (goaf). Where roof conditions preclude the use of conventional pillar-extraction methods, this method holds promise as a safe and efficient alternative for the recovery of coal from pillars and for an increase in the volumetric extraction of the reserves within a mining panel.

Jan 1, 1984

By B. Larsen

The Søderberg electrode was invented about 95 years ago by the company Elektrokjemisk, later known as ELKEM. It is still the most commonly used electrode system in submerged-arc furnaces for ferroalloys, platinum smelting, and slag cleaning operations. The size of the furnaces and electrodes has increased over the years and electrode diameters up to 2000 mm are today in use. Such large electrodes can be challenging to manage, and large electrodes are also more demanding when it comes to the electrode paste used in the electrodes. Although electrode sizes and equipment around the electrodes have changed, the main principles of the Søderberg electrode processes are the same. To assists in proper understanding of the electrode processes and to optimize electrode management, Elkem has developed several mathematical tools covering various aspect of the process. Both temperatures and thermal stresses can be calculated during dynamic conditions. The paper demonstrates, with examples, how the tools are used in both education and as practical input to improved electrode performance.

Jan 1, 2012

By A. A. Rogozhin, S. I. Anufrieva, A. V. Kurkov

The results of development of technologies for flotation concentration of two types of complex beryllium ores are presented: beryllium-fluorite in apocarbonate metasomatites (Type I) and rare-earthberyllium in feldspar metasomatites (Type II). The researched samples of Type I ores contain a mineral complex that is difficult to separate by fatty acid flotation, including phenakite, bertrandite, fluorite, and carbonate minerals. The ores are characterised by an increased content of fluorite and carbonates. The sample of Type II ore contains such rare-earth minerals as bastnesite and orthite, and a beryllium mineral - cleiophane. The size of individualised grains of cleiophane does not exceed 0.04 mm, which significantly limits the possibility of extracting the mineral into the enrichment concentrates. For the Type I ores, a technological process for the extraction of fluorite using a phosphorus-containing reagent from the class of dialkylphenyl polyethylene glycol esters of phosphoric acid (DAPEGEPhA) has been developed. The use of DAPEGEPhA enables the production of a high-grade fluorite concentrate (95% CaF2). The production of commodity phenakite-bertrandite high-grade (10% BeO) flotation concentrate from the fluorite flotation tailings with using a fatty acid collector is based on binding calcium in the flotation pulp using soda, sodium hydroxide and sodium tripolyphosphate. The use of a combined collector based on fatty acids and DAPEGEPhA made it possible to produce a collective rare-earthberyllium- lithium concentrate with high REE extraction (88%) from the Type II ores. The concentrates obtained are suitable for production of commercial-grade hydrometallurgy products. Keywords: Beryllium ores, flotation, reagents, concentrates, hydrometallurgy products

Jan 1, 2020

1. Reviews A concise world atlas of geology and mineral deposits, by D. R. Derry. London, Mining Journal Books, 1980. (Reviewer: B. C. Alberts) The geology of the Western Cordillera of northern Peru, by various authors. London, Institute of Geological Sciences, Overseas Memoir 5. (Reviewer: C. E. Feather) 2. New books Influence of diffusion coatings on the strenth of steel, by G. V. Karpenko, V. I. Pokhmurovskii, V. B. Dasilov, and V. S. Zamikhovskii, second revised and updated edition by A. Aladjem. Aedermannsdorf (Switzerland), Trans Tech Publications, 1979. 200 pp. Sw. Fr. 68.00. Mechanical and corrosion properties, by G. S. Ansell, P. Haasen, J. Weertman, D. J. Fisher, U. Gramberg, and F. W6hlbier (editors). Heat-resistant and refractory steels, by K. L. Lanskaya. Aedermannsdorf (Switzerland), Trans Tech Publications, 1979. 266 pp. Sw. Fr. 86.00. Hardening of metals, by P. Feltham (editor). Aedermannsdorf (Switzerland), Trans Tech Publications, 1980. 316 pp. Sw. Fr. 78.00. Precious metals The 6th International Precious Metals Conference will be held in Newport Beach, California, from 7th to 11th June, 1982. Strata mechanics A symposium on Strata Mechanics is to be held in Newcastle-upon-Tyne from 5th to 7th April, 1982. Over the past thirty years, mining of coal and stratified mineral deposits has become increasingly capital-intensive, and the level of investment demanded by modern methods has led to demands for improved assessment of their likely performance.

Jan 1, 1981

By А. V. Aksenov, S. G. Rybkin, А. Y. Senchenko

For gold plants in Russia, it is very complicated and costly to use cyanide leaching for efficient processing of gold refractory ores, where gold is closely associated with sulphide minerals and the significant amount of natural carbonaceous matter present. Oxidative roasting of gold refractory concentrates is a well-known method, making it possible to obtain a high recovery rate of precious metals to a target product. The use of oxidative roasting is limited in general by the expense of capturing and neutralising the harmful components of roasted gas, mainly sulphur (SO2, SO3) and arsenic (As2O3) oxides. This paper addresses testing and development of an optimised technology to process gold refractory gravity and flotation concentrates by means of oxidative roasting which stabilises arsenic as calcium arsenate. The process involves roasting of a gravity or flotation refractory ore concentrate in a mixture with lime and calcium chloride, with a supply of oxygen, and at 600-700°С. During the roasting a carbonaceous matter of the concentrate burns out and sulphide components transform into harmless calcium sulphate (CaSO4) and calcium arsenate (Ca3(AsO4)2), and iron passes into the form of hematite (Fe2O3). After disintegration, the roasting cinder is concentrated on a table to obtain a high-grade gravity concentrate and gravity tailings. The high-grade gravity concentrate is subject to smelting in a mixture with fluxing agents, which results in alloyed gold and slag. The gravity tailings are ground and reported to cyanide leaching. In the case of a flotation concentrate, the roast cinder is ground to minus 30 μm and subject to sorption cyanide leaching. High gold recovery (90-95%) of the target product and environmental safety are typical of the improved technology under consideration. Two national patents were granted for the methods developed to treat refractory concentrates bearing precious metals. Keywords: Gold concentrates, oxidative roasting, cinder, cyanide leaching, smelting, alloyed gold

Jan 1, 2020

By N. Mangadoddy, M. Padhi

The simulation of multi-component classification with modified viscosity model is the key focus in the current study. The classification of the ores using hydrocyclone is a renowned process and has a convoluted flow separation phenomenon. The highly turbulent flow inside hydrocyclone depends on the operating and design parameters apart from the feed mixture. Slurry viscosity also plays a dominant role in the classification of solid particles under the centrifugal settling action. A heterogeneous mixture with different components would result in different settling and rheological behaviour of particles’ suspension in the water medium. The newly proposed multi-component viscosity model (Mandakini et al. 2020) is implemented as a user-defined function to define the material property during the CFD study of the mixture rheology inside hydrocyclone classifier. The multiphase and turbulence model is solved using the modified Algebraic Slip Model and Large Eddy Simulation model. A comparison of the predicted component performance curves is evaluated with and without the corrected viscosity model. The density and size effect on the particle phase distribution inside the classifier are compared, where the misplacements of the finer particles are carefully assessed. Validation of the component classification in hydrocyclone with the laboratory experiments found a close agreement with the rheology based CFD data. Keywords: Dual-component, multi-component viscosity model, double-gap rheometer, computational fluid dynamics, high solids concentration

Jan 1, 2020

Plurigaussian simulation allows constructing lithofacies or rock type models that reproduce the contacts between facies in accordance with the geologist?s interpretation. Its implementation requires inferring the local facies proportions, but the uncertainty in the true proportions is not accounted for. The simpler model with constant facies proportions may not yield realistic results, due to the possibility of obtaining facies at locations where it is geologically unlikely to find them. This article presents a variation of the plurigaussian model, in which the facies proportions are represented by random fields. The realizations can be made conditional to soft geological informati onto account for local changes in the facies proportions. The model is illustrated via a case study of a porphyry copper deposit where four Gaussian random fields are simulated conditionally to drill hole data and to constraints on the probability of finding a given facies at specific locations (control points) in the deposit. Then the first two fields are truncated using the random thresholds defined by the last two, generating a three-facies model. The proposed random proportion model proves to be simple to use and to account for spatial variations of the geological characteristics and for the uncertainty in the facies proportions. Keywords: categorical variable; lithofacies; truncated plurigaussian simulation; regionalized proportions

Jan 1, 2008

By M. Borowski, N. Szlazak, D. Obracaj

Methods of research and control of the intensity of gas inflow to undersoil layers, after the mines were abandoned are presented in the paper. Gas migration causes them to penetrate to lower storeys of buildings and earthen structures being a menace to people's health and life. The results of measurements of gas concentration in undersoil layers, gas emission to atmosphere and their accumulation in buildings on the territory of closed down mines are presented.

Jan 1, 2003

By N. Naudé, J. de Villiers, C. P. Bergmann

It is proposed that the physical and chemical composition of individual mineral particles are an appropriate basis from which to model the performance of minerals processing equipment. Such a particle-based approach enables modelling across disciplines such as comminution, classification and flotation and automatically generates the traditional mass and chemistry balances. The general approach followed is to generate full grade-recovery curves for a separator by sampling product and tailings at varying mass yields. AutoSEM characterisation of each sample provides particle data that is used to reconcile mineral deportment and liberation to the measured size and assay data. In this way, partition surfaces can be generated and modelled. In this paper, an empirical model for the performance of a gravity spiral concentrator treating fine chromite ore is proposed. The model is based on the combination of two partition surfaces and is able to accommodate both forward and reverse gravity concentration effects per size fraction. The results show that this approach is well suited to represent spiral performance for the cases evaluated. The effect of two feed particle size distributions on the performance of the Multotec SC21 and SC25 spirals is demonstrated. Simulations are run in an Excel environment, linked to Python-enabled routines for enhanced data management and calculation speed. Keywords: Spiral concentrator, gravity separation, particle-based modelling

Jan 1, 2020

By M. Bryson, G. Marap, M. Ntlhane, M. D. Hlahane

This study investigated flotation of phosphate from a low-medium grade 8-12% P2O5, 65-73% SiO2 sedimentary phosphate ore from Kropz Elandsfontein (herein referred to as Elandsfontein) in South Africa. Quantitative evaluation of minerals by scanning electron microscopy (QEMSCAN) was used to determine apatite grain size distribution, liberation and mineral association in the F2 horizon sample. The mineralogy indicated that apatite was liberated and for the Elandsfontein plant to operate at the design throughput, the flotation feed has to be milled to a coarse grind ranging between 300 μm and 425 μm. Reverse flotation process routes using varying reagent dosages, and flotation feed top sizes that could possibly yield a final product of 31% P2O5,10% SiO2 at a reasonable +70% P2O5 recovery were investigated. Based on the results, a split circuit of coarse (-300+212μm) flotation and fine (-212+20μm) flotation, was mostly preferred as compared to treating the whole ore. A final combined concentrate of 31% P2O5 and 10% SiO2 with P2O5 recovery of 84% could be produced from the reverse split circuit. The robustness of reverse flotation for both coarse and fine fractions was further investigated. Reverse flotation of the fines fraction was found to be robust and produced a final product of 31% P2O5. It was however more challenging to achieve the required product grade and recoveries on the coarser fraction (-425+212μm), suggesting that reverse circuit was not adequately robust at fractions coarser than 300μm. Keywords: Phosphate, sedimentary, reverse flotation, particle size

Jan 1, 2020

By V. L. Nkuna, S. R. Amos, T. Naidoo

"Ivanhoe Mines’ Kamoa copper project is a recently discovered high-grade copper sulphide deposit in the Katanga Province of the Democratic Republic of Congo. The mineralization identified to date within the resource is typical of sedimentary-hosted stratiform copper deposits and comprises three distinct units: supergene, mixed, and hypogene mineralization. Since 2010, various metallurgical test work campaigns have been conducted on drill core from different areas within the deposit in line with resource expansion. The most recent bench-scale flotation test work has shown positive repeatable results. The work was conducted on a composite sample of drill core from the southern part of the Kamoa resource. The sample is representative of the first four to five years of planned production, when Ivanhoe Mines intends to produce clean, highgrade copper flotation concentrate. A detailed test work roadmap developed from first principles for the campaign led to an optimum flow sheet for treating the Kamoa mineralization. Copper recoveries of 88.3%, at a concentrate grade of 39.0% copper, were achieved using a composite sample — an improvement on the previously published 85.9% life-of-mine average copper recovery indicated in the November 2013 Kamoa Preliminary Economic Assessment. IntroductionThe Kamoa project is a newly discovered, very large, stratiform copper deposit with adjacent prospective exploration areas within the Central African Copperbelt, approximately 25 km west of the town of Kolwezi in the Democratic Republic of the Congo (DRC) and about 270 kilometres west of the provincial capital of Lubumbashi. Ivanhoe Mines holds its 95% interest in the Kamoa copper project through a subsidiary company, Kamoa Copper SA Limited SPRL, and DRC government owns 5%. The project location is indicated in Figure 1.In January 2013, a new independent mineral resource estimate ranked Kamoa as Africa's largest high-grade copper discovery and the world's largest undeveloped highgrade copper discovery. At this time, Ivanhoe Mines had estimated discovered Indicated Mineral Resources of 739 Mt grading 2.67% copper, containing 43.5 billion pounds of copper, and Inferred Mineral Resources of 227 Mt grading 1.96% copper, containing 9.8 billion pounds of copper, as demonstrated in the Preliminary Economic Assessment (PEA) (AMC, 2013). A 1% copper cut-off grade and a minimum vertical mining thickness of 3 m were applied in each classification."

Jan 1, 2016

By J. C. Barry, J. H. van Laar, P. L. Crouse, H. Bissett, I. J. van der Walt

"Plasma-assisted spheroidisation of metal powders offers several technical advantages with respect to both the ease of materials handling and powder-metallurgical item manufacturing. Advantages include improved flowability, increased powder packing density, elimination of internal component cavities and fractures, changes in morphology resulting in decreased friction between particles and contamination during pneumatic transport and enhanced particle purity. In this empirical study, spherical iron particles were produced using a microwave plasma operating at atmospheric pressure and characterized using optical microscopy and SEM techniques. Iron powders were fed into the system at fixed operating conditions, resulting in particles with spherical structures. The theoretical estimate of the time required for melting to occur is 1.6 ms, an order of magnitude smaller than the actual residence time. IntroductionParticle design and functionalization has become an increasingly popular aspect of materials synthesis and powder-metallurgical item manufacturing. One such technique involves the spheroidisation and densification of feed materials, typically in the form of chemical powders with wide particle size distributions. The major benefits of powder spheroidisation include improved powder flowability, increased powder packing density and powder purity, reductions in internal voids and defects, as well as the ability to manipulate the particles surface morphologies (Boulos, 2004). Thermal plasma processing has the potential for scale-up and for producing industrial quantities of spheroidised powder.Thermal plasma technologies offer a wide spectrum of material synthesis and treatment options, amongst others the synthesis and spheroidisation of nano-sized ceramic and metal particles (Kumar and Selvarajan, 2006). The spheroidisation process occurs within the plasma discharge via in-flight heating and melting of the powder feed material, given high enough plasma temperatures (Fridman, 2008, p. 495). Surface tension in the molten droplets results in spherical, or nearly, spherical, powder particles being formed upon exiting the plasma discharge where the droplet undergoes rapid cooling and freezes. Quite often, the bulk density of these spherical particles is higher than that of the starting material (Boulos, Fauchais and Pfender, 2013, p. 42). The different plasma spheroidisation techniques reported include radio frequency (RF) induction thermal plasmas (Jiang and Boulos, 2006; Karoly and Szepvolgyi, 2005; Yuming, Junjie and Yanwei, 2013), nontransferred direct current (DC) thermal plasmas (Chaturvedi et al., 2014; Kumar and Selvarajan, 2008; Suresh, Selvarajan and Vijay., 2008) and microwave-assisted plasma processing methods (Chen, Gleiman and Phillips, 2001; Vanamu et al., 2004; Weigle et al., 2004)"

Jan 1, 2016

By A. P. L. Kotzé

Modelling and scheduling for Grootegeluk coal mine, situated in the north- western Transvaal, is by means of a series of modular systems. Modelling of the multilayered body, which is part of the Waterberg coalfield, was based on a detailed study of the behaviour of coal and waste qualities and the sub- sequent use of standard geostatistical techniques. A notable improvement on previous methods was attained. Scheduling procedures and systems were developed to model a multibench pit producing coal for several metallurgical plants as well as a power-station. Scheduling was done by producing a series of longitudinal cuts, the cuts being subdivided into increments. By allocating cuts to certain periods, the resulting calculated product tonnages were com- pared with production targets, and by iteration a final scheduling sequence was determined.

Jan 1, 1987

By Nelson Sánchez

The Los Bronces Development Project (LBDP) was approved in October 2007 by the Anglo American plc Board at a capital cost of some US$1.74B, and is scheduled to be completed by the end of 2010. The project represents a big step forward for the Los Bronces mine since it will increase the treatment rate by 140%, the mining rate by 64% and almost double copper production during the first four years of the project. This economy of scale will also position Los Bronces as a much bigger and efficient mining operation, better prepared to face adverse market scenarios and allowing Anglo to consolidate its position in base metals. The project addressed numerous scope alternatives such as plant capacity vs mine capacity, cut-off grade strategy to maximise value based on the existing flotation and leaching process, cutback strategy, etc. Main infrastructure aspects of the project are as follows: ?Dump area with 2400Mt capacity for waste and low grade material ?Mining equipment: 1 x electric shovel, 12 x 300t trucks, 1 x drill ?Primary crusher: 60? x 89? ?Three new power lines (144MW capacity) ?Grinding plant at 87kt/day nominal capacity (includes a 4.3km tunnel with a regenerative conveyor belt) ?Grinding plant: 1 SAG mill 40? x 25?, 2 ball mills ?Slurry pipeline (52 km from grinding to flotation plant) with five choke stations ?Flotation plant (rougher, cleaning, regrinding circuits and molybdenum flotation). The history of Los Bronces started in 1867 when it was discovered. In 1978 ENAMI (Government company) sold Los Bronces to Exxon for US$112M. The same year a snow avalanche destroyed San Francisco Flotation Plant. In 1979 the plant was rebuilt at 4.9kt/day and from 1979 to 2002 several plant expansions were made up to 54kt/day capacity. In 2002 Anglo acquired Los Bronces for US$1.3B. The 2002 resource and reserve statement showed reserves at 459Mt at 1.02%CuT and resources at 780Mt at 0.80%CuT. The 2007 statement shows reserves at 1,480Mt at 0.67%CuT and resources at 1,644Mt at 0.45%CuT. Defining the size of a plant expansion is the key challenge that any expansionary project faces. The scope of this paper is a general review of the project, describing all the mining techniques that were used to define the best options that maximise value. In this context, a range of plant capacities (from 58 to 230kt/day) combined with a range of mining capacities (from 83 to 166Mt/a) were evaluated in detail, defining for each option a mine plan, Capex and Opex, and cut-off grade strategy for flotation and leaching processes and the associated Net Present Value (NPV) that was used as the selection criteria. The Los Bronces mineral resources potential provides good growth opportunities for the mine beyond LBDP implementation, offering an exciting invitation to continue studying new initiatives that maximise the value of this deposit.

Jan 1, 2008