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By E. J. M. Jahnsen, I. Jauhari, T. Badrujaman, F. A. Stober, B. O. Wasmund, L. R. Nelson, T. Miraza, J. M. A. Geldenhuis, A. Taofik Hidyat

The role of dedicated operational support in the ramp-up and stabilisation of the FeNi-II furnace for ferro-nickel production at PT Antam?s smelter located in Pomalaa, Indonesia is described. The furnace was uprated to 32MW capability in a rebuild performed in 2005. This primarily involved installing a larger transformer, coupled with adoption of HATCH water-cooled copper plate, waffle and flanker coolers with integrated metal and slag tapblocks, HATCH air-cooled copper fin lower sidewall cooling and HATCH vertical sidewall binding system ? ?holddowns?. Following a smooth commissioning period, the progress in attaining the preliminary ramp-up target load of 24MW is described. This initial target was set by Antam, subject to some prevailing smelter equipment constraints, particularly kiln capacity. Stabilisation of the furnace operation is discussed, together with some of the specific commissioning and operational challenges surmounted by the joint Antam-HATCH team. These included: ?Mastering furnace integrity monitoring and operation with copper coolers, especially metal tapblock planned maintenance and repair strategies; ?Transition from traditional ?immersed electrode? to ?brush-arc? mode of operation approaching as closely as possible to the productive ?shielded-arc? mode of operation within existing equipment constraints; ?Reductant selection and control issues; ?Utilising the sophisticated furnace monitoring to provide detailed indication and warning of potentially destructive furnace upset conditions such as Si reversion and CO boils.

Jan 1, 2007

By H. Hearnden

Whereas in the past, ladles were simply a means of transferring molten products from furnace tapholes to points of discharge be they casting pans or waste dumps, the ladle is now becoming a more integral and versatile piece of equipment in the pyrometallurgical plant. The drive behind this development is the need for continuous improvement in performance where better, faster and cheaper means remaining competitive in the global market. This paper will explore the technologies available for the rendering of a costly and otherwise cumbersome piece of pyrometallurgical equipment more efficient and versatile in adding value to the final product. Essentially it all revolves around heat and more importantly the loss of it when tapping. The common practice is to move the molten product to its point of discharge quickly with the minimum of interruption to prevent skulling and hence the cost associated with clearing it. The advances in Oxy-fuel burners, AC or DC ladle furnaces, converters, gas purging and high velocity, bath injection systems has increased the versatility of processes and enhanced the potential for adding value to intermediate products through down stream practices such as granulation and atomisation.

Jan 1, 2004

By Luthie Els, Chris Coetzee, Roedolf Koekemoer, Casper Els, Olof Vorster, Frank Fereday

Three electric arc furnaces (EAFs) were constructed by Union Carbide at Tubatse Ferrochrome (TFC) in1975. This plant was expanded to four furnaces at the East Plant in 1985 and the gas cleaning system was enlarged without taking flow dynamics into consideration. In order to improve competitiveness, TFC has increased furnace capacity, partially substituted coal for coke, and changed the charge mix. These changes increase the heat and dust load into the air pollution control (APC) system. TFC embarked on a project to improve the APC capacity by: ?Quantifying the required off-gas capacity ?Optimising the aerodynamic flow through the system by means of Computational Fluid Dynamics (CFD) ?Converting the old Brandt Koyo top entry baghouses to bottom entry ?Upgrading the cleaning system ?Installing Gore-tex® ePTFE membrane filter bags The estimation of required off-gas capacity is traditionally done by rule-of-thumb methods such as specific extraction. A more elegant evaluation method was developed for simulating the effects of changes in charge mix on the furnace reaction gas volume and the APC system. Reaction gases are calculated by modelling the reactions taking place in the furnace and off-gas volumes are compared to both fan and baghouse capacity. This enables identification of bottle-necks in the off-gas system. CFD techniques were utilized to evaluate geometric imbalances and propose solutions to ensure optimal use of off-gas capacity. The system modifications were completed over several months and the modified equipment went into service in May2006.

Jan 1, 2007

By V. Pawlowsky-Glahn, E. Pardo-Igúzquiza, J. J. Egozcue, R. A. Olea

Compositional data constitutes a special class of quantitative measurements involving parts of a whole. The sample space has an algebraic-geometric structure different from that of real-valued data. A subcomposition is a subset of all possible parts. When compositional data values include geographical locations, they are also regionalized variables. In the Earth sciences, geochemical analyses are a common form of regionalized compositional data. Ordinarily, there are measurements only at data locations. Geostatistics has proven to be the standard for spatial estimation of regionalized variables but, in general, the compositional character of the geochemical data has been ignored. This paper presents in detail an application of cokriging for the modelling of compositional data using a method that is consistent with the compositional character of the data. The uncertainty is evaluated by a Monte Carlo procedure. The method is illustrated for the contents of arsenic and iron in groundwaters in Bangladesh, which have the peculiarity of being measured in milligrams per litre, units for which the sum of all parts does not add to a constant. Practical results include maps of estimates of the geochemical elements in the original concentration units, as well as measures of uncertainty, such as the probability that the concentration may exceed a given threshold. Results indicate that probabilities of exceedance in previous studies of the same data are too low.

Jan 1, 2015

By P. Henning

Rock fall accidents continue to be the main cause of fatal and serious injuries in the mining industry. Although there has been an improvement in the FOG (falls of ground) related fatal and serious injuries over the past few years, the rate is still too high. New technology has made it possible to reduce this rate significantly. FOG accidents imply failure of the support system or the design of the support system in use. In this paper we deal with the latest technology available to assist the mines to reduce the rates of FOG related injuries and fatalities.

Jan 1, 2010

A number of impending and actual pit wall failures have been observed and documented, which have been interpreted to initiate on newly generated structural features. This infers failure through intact rock. Failure mechanisms have been postulated resulting from circumferential stress, extensional strain and brittle flexure. These will be discussed in the context of the failures and the associated monitoring. The implications of failure initiating on ?unknown? features has a significant impact for deep open pit mines where designs are based on the expected structural regime. Being able to anticipate such failures is important for design. Equally important is management of such changes as they arise. In this context, monitoring using high resolution microseismic techniques will be discussed as a means of providing early warning of such failures.

Jan 1, 2006

By R. Armstrong

Due to limited available level ground, Nkomati Nickel Mine cut a weathered rock slope at the base of a mountain spur in order to create a platform for construction of the primary crusher plant and run-of-mine stockpiles. As space is limited around the mining area, ore processing at Nkomati is based on a high reliability of flow of material through the crusher plant, with minimal usage of other and larger designed stockpiles. Evidently, any crusher plant shutdown will render the mine as a whole unproductive and put excessive strain on the medium- to long-term large ore stockpiles, the deposition rates for which are restricted by founding material consolidation requirements. At the onset of the 2012 rainy season, movement was identified on the slope monitoring system and cracks developed on the slope. After a minor failure on the crusher slope an assessment of the slope stability was conducted and a slope management plan recommended, which included deployment of real-time monitoring. An evaluation of the conditions leading to instability was conducted and the likely causes for the failure identified. A full evaluation of the slope monitoring, rainfall, and mining conditions was undertaken and movement triggers were determined. This paper describes the events leading to the development of the failure and the evaluation of the monitoring data to determine a management plan for the failure that allowed for minimal shutdowns of the primary crusher.

Jan 1, 2014

By F. Lombard

We consider the Grubbs estimation of the precision of an online gauge. Typically, this type of estimation involves independent results from two or more reference instruments (sampling and laboratory analysis operations). The properties of the estimator are then independent of the product variability. However, the use of more than one reference instrument entails significant additional costs. The two-instrument Grubbs estimator, which is based on results from a gauge and a single reference instrument, has the disadvantage that its standard error is heavily dependent on the degree of product variability. We propose a new estimator that has a variance that is more or less independent of product variability. In fact, the variance is typically less than that of the Grubbs estimator based on the use of two reference instruments. In order to function successfully, our methodology requires some prior knowledge of the extent of product variability and of gauge precision. In practice, such prior knowledge is often available and it is a weakness of the traditional two - and three-instrument Grubbs methods that no use is made of such knowledge. The efficacy and robustness of the new method is illustrated by Monte Carlo simulation.

Jan 1, 2012

By L. Forsbacka, M. Nakamoto, L. Holappa

Viscosity of the slag is one of the central parameters when producing FeCr in submerged arc furnaces. It contributes to smelting behaviour and reduction kinetics of chromite ore as well as to the Cr recovery by influencing the separation of dispersed metal droplets from the slag. A typical FeCr process slag contains 5-10pct chromium oxides, CrO and CrO1.5. The neural network computation was applied to the evaluation of viscosity for slags containing chromium oxides, and the prediction of viscosity in FeCr process slag was conducted. The main results in this estimation were that the chromium oxides in FeCr process slag lower its viscosity, and that the effect of CrO on the viscosity decrease is greater than that of CrO1.5.

Jan 1, 2007

By J. Forwood

The Youga gold mine in Burkina Faso, West Africa, is scheduled to produce first gold in the third quarter of calendar 2007. The project is expected to produce 540 000 oz of gold over 6.5 years, from a conventional open pit carbon in leach mine. The direct capital cost of the project is US$47 M. Etruscan Resources Inc, a Canadian based gold exploration and development company, holds 90 per cent of the project company Burkina Mining Company SA (BMC). The state of Burkina Faso is free-carried for the remaining ten per cent of BMC. RMB Resources Limited, of Melbourne Australia, has arranged a US$35 M project finance facility for BMC (the Borrower) as the majority of funding for the Youga project development. The loan facility was provided by RMB Australia Holdings and Macquarie Bank Ltd (the Lenders) each as to 50 per cent in the lending syndicate. The Lenders also provided a gold hedging facility to guarantee a minimum price for the project's gold production. Burkina Faso is a francophone country, part of the Economic and Monetary Union of West Africa (UEMOA). The project financing is the first such facility to be arranged for a mining project in Burkina Faso, with little or no precedent available in other UEMOA countries. Therefore, while the Youga gold project is forecast to be a robust project applying conventional mining and processing methods, a number of legal, technical, commercial and social issues required identification, evaluation and resolution before the loan could be established. This paper describes that evaluation process and the resolution of these issues. In-house experience and expertise in both the Lenders' and Borrower's teams has facilitated a greater understanding and `ownership' of the issues and hence provided comfort with risks which might not normally be taken in conventional project developments and project financings. As a result, blanket external reviews were not required by the Lenders. A long-standing relationship between Etruscan and RMB Resources also facilitated solutions to a number of issues. Nevertheless, a degree of flexibility by the Lenders, the Borrower and Etruscan was required to successfully close the financing.

Jan 1, 2007

By S. H. Badenhorst

Zacharias Lewala discovered a diamond at Grasplatz, near Lüderitz in April 1908. While this stone may not have been the first diamond to be found in this barren, inhospitable area, it most certainly was the stone that set off a chain reaction ultimately leading to the creation of Namdeb as we know it today. [ ]

Jan 1, 2003

By K. Schwerdtfeger

Data are presented on the effect of iron oxide on the electrical conductivity of CaO-SiO2-FeO-Fe2O3melts, and on limiting current and impedance in direct current or alternating current charge transfer at iron electrodes. The strong influence of iron oxide content can be utilized for in situ determination of total iron oxide content and Fe3+/Fe2+ratio. The possible probe designs are presented and the principles and procedures of the measurements are explained. Keywords: in situ probe for iron oxide determination in steelmaking slags, electrical conductivity of CaO-SiO2-FeO-Fe2O3slags, direct current over voltage and alternating current impedance at iron/slag electrodes.

Jan 1, 2004

By H. Jalkanen, L. Holappa

The main role of slag in oxygen converter processes is to absorb the non-volatile oxidation products of hot metal impurities, Si, P, Mn, Ti, V, etc. The importance of converter slag as deP and de Smedia has ceased with implementation of special pre- and post-converter treatments. The transfer from top blowing (LD) to combined blowing converters has decreased the amount of slagged iron that, together with the tendency towards lower silicon and manganese contents, has decreased slag to steel ratio. Still the control of slag forming and behaviour during the blow is of great importance. In this paper the thermodynamics of the slag forming reactions, the role of slag in the modern oxygen converter process for impurity elimination, splashing, lining wear, dust formation and post combustion are discussed on the basis of common knowledge and experience of Finnish steel plants.

Jan 1, 2004

By Q. C. Reynolds

Keywords: Pyrometallurgy, plant, photography, GIS, satellite images, Google Earth Google Earth is a piece of software able to display an interactive three-dimensional map of the world, combining aerial and satellite photography with maps, terrain, and user-generated geographical information systems (GIS). Many structural features of the planet, both natural and man-made, are of great interest to the mining and metallurgy field, and in this paper a study is made of the current state of the art of data accessible by Google Earth.

Jan 1, 2006

By J A. Rabe, PAP Fouche, K O?Neill

Two of the most important issues mines have to deal with are tracking the ore mined from pit to plant and to test the efficiency of beneficiation equipment. Kumba Resources and Saco Systems are working together at moment to develop a RFID tracer system to help address these issues. This paper will focus on the tracking of ore from pit to plant. The main advantages for ore tracking is to ensure plant feed blending and dilution according to plan. The RFID tracer system works on the basis of a tracer that physically simulates the ore properties and radio frequency technology that facilitates communication with the tracer and allowing information to be stored on the tracer. This paper tends to indicate the progress on the application of RFID tracer technology in the minerals processing environment as tested at Kumba Resources so far. It is concluded that the system has great potential, but some important problems remain

Jan 1, 2005

By D. Hoffmann, S. Plumb

IRUP is an iron-rich ultramafic pegmatite rock that formed due to hot ironrich fluids and gases replacing local stratigraphic zones of the Bushveld Complex. This study focuses on the estimation of the probability of IRUP occurrence on the Merensky Reef at the Marikana Karee Mine. A 2.15 million centare IRUP-rich domain at the Karee Mine was initially defined from the interpretation of a surface aeromagnetic anomaly, and exposures in the mine workings. Surface boreholes (spaced 250-500 m apart) within this IRUP domain contain approximately equal numbers of IRUP-replaced and IRUP-free intersections. Owing to the uncertainty in the continuity of the IRUP alteration (a result of the wide borehole spacing), the risk associated with the development of mining infrastructure within this domain is unquantifiable. Semi-quantitative data comprising visual estimates of IRUP replacement from reef development mapping data and surface borehole reef intersections was interpolated into blocks using indicator kriging estimation. Comparative analyses of the estimate of IRUP occurrences were made by changing the block size and declustering the data systematically. Reconciliations of the probability of IRUP predicted from the block models derived from the different data-sets and sequential indicator simulation models were analysed for four mining study blocks. A quantitative approach to modelling the occurrence of IRUP can be an additional tool for refining the estimate of the geological losses that inform the mine plan in such high-risk zones.

Jan 1, 2015

By P. J. N. Pells

A good thing is becoming a bad thing. Rock mass classification systems, that are so excellent for communications between engineers and geologists, and that can be valuable in categorizing project experience, are emasculating engineering geology and rock mechanics. Some engineering geologists have been sucked into thinking that Q and RMR values are all that is needed for engineering purposes, and seem to have put aside what can be learned from structural geology and geomorphology. Many rock mechanics engineers seem to have forgotten the scientific method. This paper attempts to redress the situation by showing how mechanics can be used in rock engineering to design with a similar rigour to that used in the fields of structural engineering, hydraulics and soil mechanics. It also attempts to remind practitioners of what can be achieved by skilled engineering geology.

Jan 1, 2008

By D. M. Mubita

Dilution reduction is one of the areas that offer metal mines an opportunity to increase revenue and reduce costs, resulting in enhanced profits. Effective dilution control programmes require interaction on a multi-disciplinary level. This paper outlines recent initiatives undertaken at Konkola Mine to reduce dilution and increase revenue. The increase in revenue arising from reduced dilution and high factors between in situ and delivered to mill grades were quantified and amount to close to U$ 1.0 million per one per cent improvement in grade factor at a 75c/lb copper price. Sources of dilution from open and in?stope mining methods practised at the mine were identified and a multi-disciplinary dilution control forum set up to control these. Among the major achievements were the introduction of low dilution in-stope mining methods; the introduction of Gemcom geological and mining planning software to replace traditional pencil and paper methods, leading to better in situ estimation and production planning; enhanced control in open stopes through dilution awareness among mining production personnel; location of critical secondary development ends in correct positions; enhanced blast hole control; tracking of development waste by metal tracers and monthly tally; implementation of a cavity monitoring system to check over-breaks in open stopes; and setting up of a stope history database. The results from the cavity monitoring system showed that stopes with over-breaks of 5 metres or less could be controlled to break along the hangingwall contact.

Jan 1, 2005

By S. Frimpong, S. R. Dindarloo

Material handling in open pit mining accounts for about 50% of production costs. The selection and deployment of efficient, safe, and economic loading and haulage systems is thus critical to the production process. The problems of truck and shovel selection and sizing include determination of the optimal number and capacities of haulage and loading units, as well as their allocation and operational strategies. Critical survey and analysis of the literature has shown that deterministic, stochastic, and experimental approaches to these problems result in considerably different outputs. This paper presents a comprehensive simulation framework for the problem of truck and shovel selection and sizing based on the random processes underlying the network-continuous-discrete event nature of the mining operation. The framework builds on previous research in this field and attempts to address limitations of available methodologies in the form of a comprehensive algorithm. To test the validity of the framework a large open pit mine was evaluated. The stochastic processes governing the uncertainties underlying the material loading and haulage input variables were defined and built into the stochastic model. Discrete event simulation was used to simulate the stochastic model. The proposed model resulted in several modifications to the case study.

Jan 1, 2015

By M. Jeffrey

This study investigated the elution of precious and toxic metals from activated carbon. Gold and mercury are of primary interest, due to their value and environmental impact respectively. A laboratory elution rig was commissioned to simulate industrial Zadra and AARL carbon elution conditions. Mercury was found to elute most effectively in strong caustic cyanide solutions; gold was found to elute most effectively in hot low ionic strength solutions. As cyanide decomposes on contact with activated carbon at high temperatures, optimum elution conditions for gold conflicts with those for mercury?no practical compromise in conditions was found. However, sequential elution allowed reasonable recovery of both metals. Ongoing work is looking at the deportment of other metals under elution conditions.

Jan 1, 2009