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By R. L. Castro

Currently, in several caving operations, the spacing between the drawpoints is determined by consulting Laubscher's design guide (Laubscher 1994, 2000), a methodology based on the gravity flow characteristics of the caved rock. Laubscher's methodology is based upon the height of interaction between adjacent flow zones, but does not allow calculation of primary recovery for a given layout. In this paper the authors present a technical and economic methodology based on the flow that occurs near the drawpoint and the associated development costs to estimate the optimal spacing. The flow model at the drawpoint was validated at the El Teniente mine, which extracts coarse caved rock. To validate the flow model, small-scale simulations using drawpoint clusters were conducted and results compared to extracted grades, marker recovery, and drill holes to determine ore remnants that are part of the production control programme at the mine. The results indicate that primary recovery depends on the height of interaction, which varies with the friction angle of the caved rock and the spacing between adjacent drawpoints. Primary recovery estimations indicate values from 85 per cent to 97 per cent depending on the drawpoint spacing used. Extrapolations were then conducted to estimate the primary recovery for different drawpoint configurations planned to be used in the New Mine Level of the mine. The results indicate that the optimal drawpoint spacing is 32 m x 20 m with a through length of 18 m. The methodology developed may be used to estimate optimal drawpoint spacing for block caving mines under different metal prices and mine cost conditions.

Jan 1, 2012

By V. Léveillé

As new legislation drives metallurgical plants to lower SO2 emissions, plant managers face the challenge of keeping their costs under control. The Cansolv® SO2 Scrubbing System has been broadly adopted in the non-ferrous industry as a cost-effective solution for smelter operators to meet the new SO2 emissions targets. The Cansolv® SO2 Scrubbing System is an a mine-based regenerable process that selectively absorbs SO2 from a variety of gases, including dilute smelter gases, such as furnace and converter gases. The system produces a pure, water-saturated SO2 by-product stream, which can then be directed to the front end of a sulphuric acid plant for conversion to sulphuric acid. When deployed in a smelter complex, the Cansolv® SO2 Scrubbing System may also be used to process acid plant tail gas, allowing single absorption sulphuric acid plants to achieve emissions an order of magnitude lower than that of a double absorption acid plant with a lower capital investment. Depending on inlet gas temperature, SO2 emissions in the treated gas can be controlled to as low as 55mg/Nm3. This paper will describe some of the applications where customers have or are planning to use the Cansolv® SO2 Scrubbing System, as well as which features and cost advantages for the treatment of smelter gases were important in the technology choice.

Jan 1, 2009

By J. L. Porter

This paper takes a personal look, through the author?s own experiences, at the implementation of innovations in the narrow-seam, hard-rock mining environment of South Africa?s mining industry over the past 40 years. A number of examples are used to illustrate some of the successes and failures over this period. More importantly, the examples are used to illustrate that the bulk of the investment for these projects should have been applied in a manner that could have achieved more sustainable results. The use of the word ?technology? in this context is also examined, as it is the author?s contention that only measuring the performance of machinery fails to encapsulate the potential of the entire system describing the scope of the innovation being implemented. These experiences and observations are projected onto the current backdrop of upheaval in the relationship between key industry stakeholders and the sustainability challenges facing areas of the mining sector in the South African economy. The paper concludes with some opinions on where attention can be focused in order to develop new thinking that can be applied for the safe and economic extraction of the nation?s mineral wealth.

Jan 1, 2014

High pressure grinding roll (HPGR) technology is used in an increasingly diverse range of applications, predominantly iron ore , gold and diamonds. KHD Humboldt Wedag HPGRs are applied world-wide, and consistently prove to be well designed and reliable operating units, with their performance meeting the pre-set standards. This publication summarizes some of the features and experiences for recent applications in treatment of copper ore, coarse iron ore, and gold ore. Summary data of roll surface wear life and operating data are given, together with operational observations. In addition, effects of feed segregation and truncated feed are discussed, as well as the implications of a product recycle flow sheet.

Jan 1, 2012

When designing coal mine roof support, it is necessary to account for the uncertainties and variability that inherently exist within the rock mass and support elements. The performance of a support system is affected by these uncertainties, which are not taken into account in the current deterministic design methodologies used in South Africa. The key to the design of a roof support system is a better understanding of roof behaviour and uncertainties that can been countered during extraction. This paper sets out to develop a method that takes all uncertainties that exist within the rock mass and the mining process into account and provides a quantitative risk-based design methodology.

Jan 1, 2009

By F. T. Cawood

This article offers a personal and independent view on the threats to the sustainability of the South African minerals industry. It argues that if the six identified threats of insufficient spending on research and development, general standard of education, nationalization, inadequate infrastructure, Aids prevalence and labour inefficiency are not acted upon as a matter of urgency, the future of the mining industry, along with its important contribution to the economy, is at risk.

Jan 1, 2011

By S. A. Abdel Sabour

Strategic decisions in the mining industry are made under multiple technical and market uncertainties. Therefore, to reach the best possible decision, based on information available, it is necessary to integrate uncertainty about the input variables and model financial risk of the project?s merit measures. However, this provides few useful insights to decision-makers unless accompanied by modelling management responses to uncertainty resolutions. It is widely acknowledged that conventional decision-support methods based on static, no-change, discounted cash flow (DCF) techniques such as net present value (NPV) and internal rate of return (IRR) tend to provide inaccurate value estimates. This could mislead the strategic decision-making process and result in significant value losses. This paper aims to model financial risk related to uncertainty about market variables such as metal prices and foreign exchange rates. Other sources of risk that are related, for example, to geology and production costs are not considered in this work. The article outlines a flexible financial model that integrates uncertainty about market variables and management flexibility to react to uncertainty resolutions into mine project valuation using a real-options valuation technique based on Monte Carlo simulation. Significance of information generated from this simulation-based flexible valuation model to the strategic decision-making process is tested using an illustrative case study of a Canadian mining project. The project is a typical multi-metal, open pit mine that produces copper and gold. In this case, there are three uncertain market variables, which are: copper and gold prices and US$/CAN$ exchange rate. Financial valuations are carried out using both the conventional static DCF method and a flexible real-options model. In the flexible model, management flexibility to decide whether to go ahead with the next expansion or terminate production operations is integrated. Results show how the flexible financial model can enhance the decision-making process.

Jan 1, 2009

The proper understanding of the functioning of ground support under dynamic loading and the current approaches to designing of dynamic support are plagued by a great deal of uncertainty and lack of knowledge. This applies equally to the understanding of the support capacity as well as the demand placed onto the support due to dynamic loading. This lack of understanding currently leads to a case of design indeterminacy. This paper does not aim to solve this problem of design indeterminacy but to explore some of the issues that need consideration to obtain a better understanding of the dynamic demand on ground support systems. Keywords ground support, dynamic loading.

Dec 1, 2013

By J. Loubser

The concept of caring is in most cases confused with material needs and not psychological needs. By giving employees a job, most managers think that employees should be grateful and return the favour by being loyal, productive and working safely. Other managers hold the view that employees can be lucky to have a job. To show and demonstrate that management are caring for the safety of the workforce requires involvement, dedication and commitment. Obtaining the trust and respect of the workforce should be the main thrust of any organization because within trust and respect lie the secret of optimal safety performance. In the last 70 years, all the fatalities and serious injuries that occurred in the mining industry can be traced back to one thing, non-caring. The same safety non-compliances are still observed, reported and planned against as 70 years ago, and strange as it may sound, the same injuries occur the same way. The question could be asked: Does the mining industry need more risk assessments? More codes of conduct? More engineering. Or does the mining industry need more caring?

Jan 1, 2010

By M. Yavuz

Determining the most convenient plant location is one of the most commonly encountered problems in engineering applications. This paper presents a fuzzy multiple attribute decision making (FMADM) model which is developed for the selection of the optimum plant location for natural stone factories in the mining industry. The criteria affecting the decision making process in natural stone industry were determined to solve the plant location problem in the FMADM model. To determine the optimum plant location for a new natural stone factory, which is planned to be established by a mining firm located in the Eskisehir region of Turkey, an analysis was carried out by incorporating the method and the analytic hierarchy process (AHP) method. The analysis shows that the Yager?s method can easily be applied to the selection of plant location in the natural stone and mining industry when the difficulties encountered in the application process of the AHP method is taken into account. Keywords: Natural stone, plant location, decision making, Yager?s method, analytic hierarchy process (AHP).

Jan 1, 2008

By M. Kamali

In this research, in order to predict the peak particle velocity (PPV)(as vibration indicator) caused by blasting projects in the excavations of the Karoun III power plant and dam, three techniques including statistical, empirical, and neural network were used and their results were interpreted and compared. First, multivariate regression analysis (MVRA) was used as statistical approach. Next, PPV was predicted using some widely used empirical models. Lastly, an artificial neural network was used. In the ANN model, maximum charge per delay, total charge per round, distance from blast site, direction of firing, blasthole length, number of blastholes, total delay in milliseconds, number of delay intervals, and average specific charge were taken into consideration as input parameters and consequently the PPV as output parameter. The results of the techniques were interpreted from two points of view. Firstly, the correlation between the observed data and predicted ones, secondly the total error between observed data and predicted ones. The MVRA had a satisfactory correlation but its error of estimation was comparatively very high. The empirical model had reliable correlation and a small error of estimation; in total the results of empirical method were more reliable than those of MVRA. Generally, the ANN approach showed very high correlation and a very small error. The results of this research indicated that the ANN model is the best predicting model for PPV in comparison with other approaches.

Jan 1, 2010

By R. Ajalloian, L. Karimzadeh

This paper describes the engineering properties of Givi dam foundation. Givi dam will be built across the Givi River on the andesitic rocks (Karaj formation) in Ardabil province (northeast of Iran). Geotechnical investigations including drilling, pumping tests, sampling for laboratory testing and discontinuity survey. Physical and mechanical properties of andesitic rocks such as density, water absorption, porosity, uniaxial compressive strength, triaxial compressive strength, durability and direct shear tests are evaluated in this paper. Discontinuity data are process for the determination of dominant sets and for the rock mass characterization in terms of classification systems ( RMR, Q and RSR ). Correlations between these three classifications are discussed. Le barrage doit être construit sur la rivi_re givi qui cou_e sur les andesites (formation de Karaj)dans la province d_ Ardebile situee_ a Nord- Ouest de l_ _Iran. Les études géophsique commesondage, Pompage. Et échantillonnage afin de verifier les discontinutés out éte_ effectuées. Lesproprietés physique et méchanique des roches andesifique ont éte_ verifieés. Les informations concernaüt aux discontinuitiés afin de montrer leur principale direction ont éte_ verifieés, les proprietés des roches dans leurs ensemble ont éte_ etudieés. Les divers classifications(RMR,Q,RSR ) ont éte_ comparés et analyseés. Dieses Schreiben ist zur Erklaerung der Ingenieureigenschaften ueber Baugrund des Givi Deiches.Dieser Deich soll im Givi fluss auf Andesitgesteine (Karaj formation) gebaut werden. Der platzdes Deiches legit im Ardebil Provinz nordwestlich von Iran. Geotechnische Untersuchungen Sind:Bohrungen, pumpen Versuche, Probenentnahme fuer Laborversuche, BrechbarkeitBestimmungen, physikalische und mechanische Eigenschaften der Andesitgesteine wurde hierausgewertet, wie Z.B.: Wasserleitfahigkeit, Porositaet, Scherfestigketswiderstand, Informationenueber Brechbarkeiten der Gesteine wurde gesamelt, und die meisten Brechbarkeiten bestimdamitman die Gesteine besser klassifizieren kann. In Endefekt wrid die Resultate verschiedeneKlassifizierung wie RMR, Q, und RSR besser geachtet und zusammen vergliechen.

Jan 1, 2003

High pressure grinding roll (HPGR) technology is used in an increasingly diverse range of applications, predominantly iron ore, gold and diamonds. KHD Humboldt Wedag HPGRs are applied world-wide, and consistently prove to be well designed and reliable operating units, with their performance meeting the pre-set standards. This publication summarizes some of the features and experiences for recent applications in treatment of copper ore, coarse iron ore, and gold ore. Summary data of roll surface wear life and operating data are given, together with operational observations. In addition, effects of feed segregation and truncated feed are discussed, as well as the implications of a product recycle flow sheet.

Jan 1, 2012

By S. V. Rungan

The modern mining industry is increasingly being tasked to comply with various legal, industry and social prerequisites. In addition to complying with these, the mining industry is further expected to effectively report on their compliance. Although there are many models that aid the mining industry in compliance and reporting, it is perhaps opportune for a new model to be introduced. The Compliance Spindle is postulated as a new and alternative model which is easy to understand and has the possibility of implementation in South Africa and other jurisdictions as well. The Compliance Spindle is also an effective tool to educate future compliance officers. The new model provides for all aspects of compliance and reporting and can be easily modified to take account of new developments in the mining compliance and reporting arena.

Jan 1, 2010

The 114th Annual General Meeting of The Southern African Institute of Mining and Metallurgy was held at The Country Club, Johannesburg, Napier Road, Auckland Park on Thursday, 11 August 2011. Welcome The President extended a special welcome to the guests and representatives of our sister institutes and other associations, and also to recipients of awards, senior members of industry, Honorary Life Fellows, past-presidents, our members and other guests, among them the following: F. Cawood, President, Institute of Mine Surveyors of South Africa C. Roode, President, Mine Metallurgical Managers' Association of South Africa M. Cresswell, Chairman, South African Coal Processing Society A. Hay, Immediate Past President, South African Institute of Electrical Engineers L. Gardner, President, South African National Institute of Rock Engineers J. Krynauw, President, The Geological Society of South Africa (GSSA)

Jan 1, 2011

By Sönke Schmachtel

Several possible physico-chemical properties of composite electrodes for oxygen evolution are presented to describe experimental data for which a mathematical model had been developed. On this basis, local electrical and electrochemical properties of a composite electrode were investigated with conductive atomic force microscopy (CAFM) and scanning electrochemical microscopy (SECM). It could be shown by CAFM measurement that the boundary between matrix and catalyst particles seemed to have special advantageous electrical properties. The SECM measurements showed the presence of mass transport phenomena with increased surface concentrations, whilst the thickness of the Nernst diffusion layer was very small. An intermediate was detected and assigned to be hydrogen peroxide. From all species involved in the oxygen evolution reaction (H2O2, H+ and O2), it was concluded that local active spots exist on the electrode on which hydrogen peroxide reacts to oxygen and protons. A two?step two-material process was suggested to explain the whole oxygen evolution mechanism.

Jan 1, 2008

By C. P. Naudé

Mechel, a large, integrated steel, stainless steel, and ferroalloy producer in Russia is committed to upgrading its facilities to world class pyrometallurgical process and environmental practice. Yuzhural Nickel currently uses shaft furnaces to produce a matte containing iron, nickel and traces of cobalt. This rather old technology is thermally inefficient and is characterized by high operating costs. Mechel has investigated suitable equipment and processes to upgrade the plant, and awarded a contract for the construction of a 12 MW DC smelter, located near the town of Orsk, to Bateman Engineering Projects in June 2008. The selection of DC furnace technology for laterite smelting can be considered as a strategic highlight for the pyrometallurgical treatment of low-grade lateritic ores, and could be the first industrial-scale implementation of this technology. This project has been designed to achieve multiple goals including the demonstration of the process and associated equipment technology at commercial scale, to confirm the scale-up design parameters of the forthcoming 2 x90 MW, twin electrode DC furnaces, and to prove the environmental emission superiority of closed furnaces. It also provides a valuable operator training platform. This paper deals with the process design, key technology building blocks and design features which have been incorporated to produce a pyrometallurgical vessel capable of (i) resisting slag superheat and chemical aggressiveness, (ii) process fine material without pre-agglomeration, (iii) achieve high nickel recoveries and(iv) being tolerant to the variations in chemical composition of laterite ore. The approach to increasing campaign lives between partial and complete rebuilds, through the use of composite furnace module (CFM) technology originally developed and patented by the University of Melbourne, is also followed in more detail. Unfortunately, results from hot commissioning and lessons learned from initial operation are not available because the project completion has been delayed due to the worldwide downturn in demand for commodities. Keywords DC furnace, ferronickel laterite smelting, corrosive slag, coppercooler technology.

Jan 1, 2010

By D. A. Vetter

A novel mathematical model is presented which describes the behaviour of beds of particles, of uniform size and shape but different densities, during autogenous separations. The approach used in the formulation of the dispersion model is a phenomenological one based on a statistical view, which leads to a diffusion-like representation of the autogenous-separation process. Although the model currently considers only density-related phenomena, it accounts quantitatively not only for the density-segregation aspects of the process but for the interactions between the particles. Quantitative predictions of the dispersion model are compared with the results obtained in tests using a specially constructed experimental batch jig, and it is shown that the model provides an adequate quantitative description of the process for particles of uniform size and shape. It is pointed out that, for the description of more complicated autogenous separations, a more rigorous formulation of the particle drag and density-segregation terms will have to be incorporated into the dispersion model. Nonetheless it is concluded that the model as presented in this paper provides not only a novel insight into the mechanisms of autogenous separations but a means by which to analyse similar systems.

Jan 1, 1987

By A. L. Edwards

A retrospective study was conducted on the Rand Mutual Assurance (RMA) noise-induced hearing loss (NIHL) compensation claims from 1998 to 2008 to determine if the 2008 milestone agreed at the 2003 Mine Health and Safety Summit was achieved. The number and costs of NIHL compensation claims in different commodity sectors and workplaces were collated. A secondary analysis of the ages of employees compensated after 2008 was conducted. A complementary retrospective analysis of audiogram data investigated the percentage loss of hearing (PLH) shift in different homogeneously exposed groups and occupations at two gold mines. The compensation claims analysis indicated a significant decrease in NIHL claims from 1998 to 2008, but the milestone was not achieved. The reason may be either that claims have not been submitted timeously as required by Instruction 171 and that the current submissions are a result of pre-2003 noise exposure, or that employees who were baselined are still developing NIHL owing to ineffective hearing conservation programmes in place in the mining industry. On the basis of best practice for hearing conservation, recommendations are made for leading indicators in hearing conservation programmes and for reducing the risks of NIHL in order to achieve the 2013 milestone.

Jan 1, 2012

The peak in Sulphur price late 2008 caused again intensified investigation into the decomposition of sulphates and spend acid. One option is the recycling of sulphur from spend acid, which already started more than 40 years ago in the field of spend acid from organic processes in refineries and acrylic glass manufacturing. Since this acid couldn't be neutralized and discarded due to high organic contents, another source of SO2 to produce sulfuric acid is the decomposition of metal sulfates. The decomposition of metal sulfates was investigated at the next peak in Sulphur price in the 80?s. The first major scale pilot tests and studies of gypsum decomposition were carried out for clients in Florida. The decomposition of gypsum was quite often mainly influenced by the strategic decision of some countries to get own and independent acid production. In other cases the industry doesn?t have enough space to dump the gypsum. Therefore the company was also forced to convert the gypsum into ?saleable? products to avoid these residues. Other projects were made for the recycling of iron-sulfates from the pigment industry. The motivations for these projects were not only given by acid price. For the German pigment industry it was no longer permitted in the 80?s to dump the iron sulphate residues into the sea. These regulations forced the industry to develop new technology, which allows converting of the FeSO4-residues into iron oxide and acid. Therefore economical and mainly environmental factors influenced the decision of the companies to develop and to build these plants. Beside the above mention iron- and calcium-sulphates many other process exist, which produce metal sulphates as an intermediate product. These cases are not forced by environmental or strategic factors. In cases like Ni, Co or Mn-decomposition the main product of the plant is treated in the decomposition plant and later on used as ferrous-alloys. These final products are higher in price compared to e.g. CaO, which exclude the high-energy consumption for the endothermic chemical decomposition reaction. The reaction of SO2 generation based on acid or sulfate decomposition takes place in the range of 1000°C. The energy demand of the endothermic reaction is considerable and leads due to the high fuel-combustion off-gas stream to a diluted SO2 gas. Energy prices are usually increasing at the same time like sulphur. Sulphuric Acid based on decomposition is therefore more expensive than as acid based on sulphur combustion. The paper describes fluid bed technology and possible process concepts for decomposition plants. Additionally the thermodynamic background of the decomposition process and the main influence factors are provided to receive a better understanding of this technology.

Jan 1, 2009