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By J. A. Bakken, M. T. Jonsson, G. A. Saevarsdottir, H. Palsson

The electrodes of a Submerged Arc Furnaces carry a high current and are subject to enormous stresses caused by both the electric arc itself, and the current distribution within the electrode. The external effect of the arc on the electrode is treated in a different paper at this conference, The purpose of this paper is to analyze the thermal effects of ohmic heating within the electrode at the arc attachment on the carbon based electrode, using data for Søderberg electrodes. The thermal conditions are then used to examine stress conditions in the vicinity of an arc. Two types of models of an electrode are presented in the paper. The first type is an accurate finite element model, based on both two and three dimensional elements and the second type is an one dimensional model, providing better insight into the problem. For the second type, a spherical model of thermal conditions in a semi-infinite solid has been developed. Results show that the electrode surface is heated quickly up to a maximum temperature and for a specific test case, the surface can only withstand the load for about 10 seconds. Also, the thermal stresses on the surface are very high which will increase erosion on the surface in addition to normal evaporation.

Jan 1, 2007

By H. Krogerus, P. Jokinen, T. Lintumaa

The energy consumption and recovery of chromium are important economic factors in ferrochrome production. Outokumpu has a lot of experience of the reduction behavior of the sintered pellets in industrial-scale furnaces and also on the grounds of numerous laboratory and pilot-scale investigations. Sintered pellets have shown a superiority over lumpy ore and briquettes made of the same chromite grade. The good performance of the pellets has also resulted in investigations on the reasons for such a performance. In this study, the factors affecting pellet behavior in smelting furnace were investigated. This study is divided into two sections, i.e. the investigations were on the factors affecting solid state reduction and on the factors affecting reduction under melting. These tests were performed by means of thermo gravimetry and by smelting tests. The correlation between the pellet characteristics and reduction behavior was shown and its influence on industrial-scale furnaces was discussed. Factors worth of consideration are for instance, the extent of oxidation during sintering, slag formation and chemistry in respect of molten state reduction, and the grain size of the chromite mineral in the raw material in respect of kinetic reasons (retention time in smelting).

Jan 1, 2007

By O. A. Olaseinde

The 2101 lean duplex stainless steel has wide potential application in storage, heat exchangers, and in the oil and gas industries. This work investigates the electrochemical behaviour of 2101 duplex stainless steel with an addition of 0.15 wt% ruthenium, using potentiodynamic techniques in 1M H2SO4 at 25º, 40º, 60º, and 80ºC. The microstructures of samples were characterized using optical metallography and scanning electron microscopy. The results showed that the ruthenium addition moved the corrosion potential of alloy 2101 to a more positive potential. All samples containing ruthenium displayed longer passive regions at 25°C and 80°C compared to those without ruthenium. Alloys without ruthenium had higher critical current density (icrit) values when compared to the alloys with ruthenium. Ruthenium additions decreased the passive current densities and inhibited anodic dissolution. At room temperature the corrosion rate of alloys with ruthenium was lower than these without ruthenium.

Jan 1, 2012

By N. Kumar, A. K. Dhawan, A. Varughese, S. K. Khullar

Abstract The in-situ stress field is one of the primary parameters influencing the performance of underground structures particularly in the Himalayas where there is strong influence of topography and geology on in-situ stresses. It is always advisable to measure the in-situ stresses, in whatever best way possible. Hydrofracturing is one of the methods by which in-situ stress can be measured. This paper briefly describes details of the concept of Hydrofracturing in arriving at the in-situ stresses of the rock mass at Pancheswar Project. The data obtained from the tests has been analysed, interpreted and the results are presented in this paper. Kurzfassung Das Spannungsfeld an Ort und Stelle ist einer der wichtigsten Parameter, die das Verhalten der Untergrund-Struktur beeinflussen, insbesondere in den Himalayas, wo die Topografie und die Geologie einen grossen Einfluss auf die oertlichen Spannungen ausueben. Es empfiehlt sich stets die Spannungen an Ort und Stelle so gut wie moeglich zu erfassen. Die Hydrofraktur bzw hydrografisches Zerstueckeln ist eine der Methoden, die bei den Messungen der oertlichen Spannungen verwendet werden koennen. Diese Abhandlung beschreibt kurz Einzelheiten ueber das Konzept von Hydrofraktur bei der Bestimmung der Spannungen an Ort und Stelle von der Felsmasse bezueglich des Projekts Pancheshwar. Die gewonnenen Daten aus den Messungen wurden analysieret und ausgewertet. Die Ergebnisse werden dabei vorgelegt. Sommaire Le champ de contraintes in-situ est un des paramèters principaux influencant l’exécution des structures souterraines particulierèment en Himalaya où les forces in-situ sont fortement influencées par les caractéristiques topographiques et géologiques de la région. La fracturation hydraulique est une technique qui permet de mesurer des forces in-situ des massifs rocheux. Cet article décrit brièvement le mécanisme de fracturation hydraulique et présente les résultats de mesure des forces in-situ des roches au site du projet hydroélectrique de Pancheswar.

Jan 1, 2003

By S. M. Spottiswoode, J. A. L. Napier, M. Kataka

The move away from the use of strike stabilising pillars at depth and the adoption of the more flexible system of mining towards final dip remnant pillars brings new opportunities for optimising mine design. In the initial planning stage, the size and spacing of the final pillars is designed using classical design criteria, through limiting modelled values of Energy Release Rate (ERR), Average Pillar Stress (APS) and Excess Shear Stress (ESS). In reality, mines often leave pillars that are larger than those originally designed. One of the reasons for leaving more ground is an unexpectedly high rate of seismicity. In this paper, we present developments in integration of modelling and seismicity that are aimed at developing design criteria that are more responsive to local conditions.

Jan 1, 2003

1. New publications International minerals/metals review - 1982. Washington D.C., McGraw-Hill, 1983.720 pp. U.S.$1l7. Mining subsidence engineering, by Helmut Kratzsch. New York, Springer, 1983.580 pp. U.S. $63,20. Papers presented at the 6th International Symposium on Jet Cutting Technology, Guildford, England: April 6-8, 1982, edited by H. S. Step hens and E. B. Davies. Cranfield (England), BHRA Fluid Engineering, 1982. £40. 2. Mintek reports Report M95 Modern applications of polarography and voltammetry to inorganic analysis. Report M96 The mathematical modelling of the reduction behaviour of chromite from the Upper Chromitite Layer of the Bushveld Complex. Report M113 The selective flotation of South African chromite. Conference on copper The International Conference 'Copper 83', to be held in London on 1st and 2nd November, 1983, will provide a valuable forum for all connected with the manufacture and use of copper. Underwater mining The 14th Underwater Mining Institute will be held in Madison, Wisconsin, on 7th and 8th November, 1983. Asian mining The Institution of Mining and Metallurgy, in conjunction with the Chamber of Mines of the Philippines, will hold an international conference, Asian Mining '84, in Manila, Philippines, from 6th to 8th November, 1984. Apcom '84 The Eighteenth International Symposium on the Application of Computers and Mathematics in the Minerals Industries will be held in London in the week 26th to 30th March, 1984. The Symposium is being Jet cutting Another Symposium on the very successful and popular series of international conferences on Jet Cutting Technology is being arranged by BHRA.

Jan 1, 1983

By A. H. Swart, M. F. Handley

Unplanned stope panel collapses occur on most near-surface and shallow mines in South Africa. Although these incidents often occur during blasting, they pose a major threat to the safety of underground workers and the economic extraction of orebodies. Most stope panel collapses occur due to excessive panel lengths that are not designed according to a systematic design procedure or methodology. Instead, panel lengths are often dictated by the equipment in use and by previous experience under similar conditions. Hence, a rock engineering design methodology for the design of stable stope panels between pillars is of vital importance for optimum safety and production in shallow mining operations. Using the proposed design methodology described in this paper, rock mechanics practitioners and mine planners should be able to identify and quantify the critical factors influencing the stability of stope panels. The critical factors should then be used as input to the design of stable stope panels that will provide the necessary safe environment for underground personnel working in stopes. The proposed design methodology is an iterative process, which includes aspects such as rock mass characterization, estimation of rock mass properties, identification of potential failure modes, consideration of appropriate stability analyses and other elements of the rock engineering design process. This process continues after implementation. During monitoring, new data should be included in the database and the design process repeated on a regular basis. Design approaches included in the proposed design methodology include empirical methods such as different rock mass classification methods, analytical methods such as elastic and Voussoir beam analyses, kinematic analyses, probabilistic analyses, and numerical analyses. Keywords: stability, stope panels, design methodology, hard rock mines, shallow mining operations

Jan 1, 2004

By M. J. Lukhele

Paper written on project work carried out in partial fulfilment of B. Tech (Mining Engineering) degree A number of high wall mining methods were developed over the years to mine coal reserves exposed on the high walls created during surface mining. The auger mining system was initially developed in the early 1940s in the United States of America. High wall mining is a method of recovering coal from seam exposed either by mechanical excavation methods or natural erosions. This is usually associated with strip-mining (opencast) where the stripping ratio is high and uneconomical to mine using the opencast mining method. This paper discusses the surface auger mining as deployed at Rietspruit Mine Services Proprietary Limited.

Jan 1, 2002

By L. Ntlhakana, K. Khoza-Shangase, G. Nelson, I. Maposa

Occupational noise-induced hearing loss (ONIHL) is associated with various risk factors in South African mines. We investigated the association between standard threshold shifts (STSs) and exposure to noise and platinum mine dust (PMD), using demographic data, five years of annual audiometry screening results, and noise and dust exposure data. Miners’ age, sex, percentage hearing loss (PLH), and dust and noise exposure data were gathered, and a linear mixed effects regression model used to predict STS. Average occupational exposure levels to noise and dust were calculated from recorded measurements. A total of 12 692 records were analysed. Most miners were male (89.6%) and more than 50% were younger than 41 years. More than 70% were exposed to > 85 dBA noise and 58% were exposed to 1.5–2.99 mg/m3 PMD. Changes in hearing levels ranged from 8.3 dBHL at baseline (2014/2015) to 10 dBHL in 2016 (STS), with no changes thereafter. The model showed that the estimated effect on STS for males was 27% and 21% higher than for females, for the left and right ear, respectively The estimated effect of age, PLH, noise exposure and years of exposure on STS was < 10% for each variable. There was no statistically significant association between PMD and STS. The combined effects of age, sex, years of exposure to noise, and noise exposure levels, and strength of associations can be used to predict STS for this group of miners. Our findings may be used to measure the efficacy of the mine’s hearing conservation programme.

Aug 1, 2021

Sishen Iron Ore Mine previously used only A-grade material (>60% Fe in situ value) from the pit for beneficiating in the DMS plant to a final product grade of 66% Fe in lump and 65% Fe fine ore. The B-grade (between 50% and 60% Fe) and C-grade material (between 35% and 50% Fe) were stockpiled separately, owing to the inability of the existing DMS plant to beneficiate material at densities higher than 3600 kg/m3. The ability to beneficiate the B-grade material at densities higher than 3600 kg/m3 was evaluated, and air-pulsed jigs were found to be techno-economically feasible and value maximizing. The beneficiation of B-grade material would add to the existing DMS production of 28 Mt/a, with no additional mining cost and only limited costs for the handling of waste and B-material. The objective of the Sishen Expansion Project (SEP), i.e. the jig plant, was to produce 10 Mt/a of saleable product with six modules to the set physical and chemical specifications by 2009. During the start of construction, it was decided to add another two jig modules to the plant to increase production to 13 Mt/a. During commissioning and ramp-up the shortcomings and advantages of the jigs were fully experienced and understood, resulting in many changes to optimize jigging performance..

Jan 1, 2014

By A. McLean, M. Iwase, K. Wakimoto, K. Katogi, Y. Kikuchi

One of the greatest obstacles to the application of physical chemistry principles to the elucidation of slag-metal reactions is a lack of knowledge of activities of the reacting species. To a large extent, oxygen potential of the slag phase governs iron and steelmaking practice. Without oxygen control by means of appropriate sensors, the behaviour of the other elements cannot be managed. In this paper, measurements of the FeO activity with various types of electrochemical FeO sensors will be described together with examples of their applications for improved strategies toward better practice for ladle metallurgy and sulphur and manganese distributions between slag and metal phases during steelmaking. Measurements of FeO activity have also been made in order to improve dephosphorization reactions. This type of work has led to significant reduction in volume of slag generated within the steelmaking vessel, which in turn has important implications for refractory wear, metal yield, alloy recovery and improved productivity. Finally, an on-line sensor is described that permits the oxygen potential to be determined for both the metal phase and the slag phase during steelmaking in the BOF.

Jan 1, 2004

By M. Tangstad, J. D. Steenkamp

In April 2013 a 48 MVA submerged arc furnace producing silicomanganese was excavated in South Africa. Since the high shell temperatures recorded in the tap-hole area resulted in the furnace being switched out for relining, the tap-hole area was excavated systematically. A refractory wear profile of the tap-hole area with affected hearth and sidewall refractory was obtained in elevation. The carbon ramming paste in front of, above, andbelow the tap-hole was worn, as was the SiC with which the tap-hole was built. A clay mushroom formed but was detached from the refractories. Thermodynamic and mass-transfer calculations were conducted to quantify the potential for wear by chemical reaction between refractory and slag and refractory and metal in the tap-hole area. It was found that chemical reaction between refractory and slag or metal could offer only a partial explanation for the wear observed; erosion is expected to contribute significantly to wear.

Jan 1, 2015

By R. L. Castro

Block caving methods, when operated under favourable rock mass conditions, can achieve higher production rates and lower operating costs than other various existing underground mining applications. For this reason, it has been considered the preferred method for the mining of deep and large orebodies in current and future operations around the world. One of the key aspects in the design of block caves is the selection of the production level layout, which, among other parameters, is based on the gravity flow characteristics of the caved rock. This is because gravity flow has a large impact on total ore recovery and the amount of dilution in a caving operation. Today, there are a number of computer based methods which aim to emulate the gravity flow pattern of the caved rock. In this paper, the authors present the development of FlowSiman improved model of gravity flow based on the cellular automaton approach, to estimate dilution entry, mixing and ore recovery. As part of the model development, flow simulations were conducted and subsequently compared to full-scale data collected at two mine sectors operated by Codelco Chile. The results indicate that by using proper calibrated parameters, good correlations between simulated and measured grades as well as dilution entry are obtained. The potential use of the numerical tool to evaluate drawpoint spacing in terms of recovery and dilution for block/panel caving operations is also presented.

Jan 1, 2009

William Schreiner Findlay (1908 to 1980) had a distinguished career in the mining industry, to which a mere account of his appointments does not do full justice. However, they give some idea of his ability as an engineer and a manager.

Jan 1, 1981

By Raphael Banda

1 Initiating Systems ? a definition An initiation system is a combination of explosive devices and component accessories specifically designed to convey a signal and initiate an explosive charge from a safe distance. In the use of explosives, the initiating system performs the functions of transmission and control of the firing signal to each explosive charge. As functional groups, initiating systems may be considered as: Starters Those which provide the initial signal to start the blasting process. Surface systems Products which provide transmission of the starter signal and delay timing (if any) across the surface of the blast outside the blast hole. In-hole systems Products which provide the signal transmission, delay timing (if any) and the initial explosives energy in the blast hole.1 2 Different types of Initiating Systems The initiation systems commonly used in Sub Saharan Africa are: ? Detonating cord and detonating relay systems ? Capped fuse and igniter cord systems ? Shock tube non electric systems ? Electric systems ? Electronic detonators 3 Overview of Electronic Delay Detonator Technology Conventional detonators use pyrotechnic delay elements and the variation of the actual delay periods is at best approximately 1% the nominal delay. The lack of guaranteed precision common to all pyrotechnic systems enhances the likelihood of negative environmental blasting effects.3 For example, take a 500 ms in hole delay. In conventional detonators this means that 95 % of shots fire within 10 ms of the mean. i.e. a window of 20 ms. Taking a fixed interval between shots of 25 ms, with a range of ± 3 ms, a very ragged firing pattern could be expected which in practice would result in non uniform fragmentation.

Jan 1, 2005

H. W. Glen (ed.). Proceedings of Asbestos Symposium, Johannesburg, South, Africa, 3rd-7th, October, 1977. Randburg, National Institute for Metallurgy, 1978. 158 pp. (Copies obtainable from the Department of Mines, P.O. Box 4584, Johannesburg, 2000 South Africa.) This Symposium, which concentrated on the theme of dose-response relationships for asbestos-related diseases, was attended by an internationally representative group of experts in this field. Bulk solids The Powder Advisory Centre announces its third annual International Conference on Bulk Solids Swrage, Handling and Flow, to be held at the Holiday Inn, Liverpool, on 7th to 9th November, 1978. This sequel to the extremely successful November &apos;76 Stratford and November &apos;77 Nottingham Conferences is again to be co-sponsored by a number of internationally acknowledged professional societies, including the Institute of Materials Handling (through its Bulk Solids Panel), the Institution of Production Engineers, and the American Society of Mechanical Engineers (through its Materials Handling Engineering Division). NIM reports Report no. 1943 A review of the literature on the separation and determination of rare-earth elements. (23rd Mar., 1978.) Report no. 1947 The cation- and anion-exchange behaviour of various base-metal chlorides in polar organic solvents. (lOth Mar., 1978.) Report no. 1948 The measurement of trace amounts of gold in solution by atomic-absorption spectrophotometry and carbon-rod atomization. (28th Feb., 1978.) Report no. 1949 The kinetics of the leaching of zinc sulphide concentrates in acidic solutions containing ferric sulphate. (23rd Mar., 1978.) Report no. 1950 Factors affecting the carbon contents of alloys formed during the prereduction of chromite ores. (31st Mar., 1978.) Report no. 1952 The effect of slag composition on copper losses to silicasaturated iron silicate slags. (31st Mar., 1978.) Report no. 1953 A fundamental investigation into the depression of copper-activated sphalerite. (28th Apr., 1978.) Report no. 1956 An improved ion-exchange separation of rare-earth elements for spectrographic analysis. (10th Mar., 1978.) Report no. 1960 The recovery of ferrochromium from furnace slags and related products. (20th Aug., 1976; declassified 31st Mar., 1978.) Process instrumentation The National Institute for Metallurgy and the South African Institute of Measurement and Control are organizing a symposium that will draw the attention of researchers and industrial workers to the importance of metallurgical process instrumentation.

Jan 1, 1978

By A. V. Z. Brink

Rock engineering risk is defined in this paper as a function of the potential ground motion; the vulnerability of the workplace; exposure of people; and a general term – quality of information. The paper describes the development of prototype software that is a combination between an expert system approach for determining overall risk assessment, a risk control recommendation and a basic GIS (Graphic Information System) approach for graphically overlying input parameters and the output risk. The expert system uses a Bayesian probabilistic approach to combine various workplace-related information, a quantified seismological environment and the exposure of underground staff to provide an overall RE risk rating. The risk assessment is dynamic in that it is recalculated each time that any of the input parameters change, for example each time a seismic event is recorded in the area of interest. The code was tested on a data set from Savuka Gold. As risk assessment is not an absolute prediction of a specific outcome, it is therefore not possible to relate to individual case studies and the reliability of this method would only be determined after an extensive period of use with appropiate back-analysis. Le risque dans le génie minier est défini dans cette étude comme une fonction du mouvement potentiel de terrain ; la vulnérabilité du lieu de travail ; l’exposition des personnes ; et un terme général – la qualité de l’information. L’étude présente décrit le développement d’un logiciel prototype qui est une combinaison entre une démarche de système expert pour déterminer une évaluation générale du risque, une recommandation pour le contrôle du risque, et une démarche de SIG (Système d’Information Géographique) pour superposer graphiquement les paramètres d’entrée et le risque de sortie. Le système expert utilise une méthode de probabilité bayésienne pour combiner des informations variées sur le lieu de travail, des données quantifiées sur l’environnement sismique, et l’exposition du personnel travaillant sous terre, pour finalement produire un classement général de risque minier (RE). L’évaluation du risque est dynamique en ce sens qu’elle est recalculée à chaque fois qu’un des paramètres d’entrée change, par exemple à chaque fois qu’un évènement sismique est enregistré dans la région. Le code fut testé sur un ensemble de données obtenues de Savuka Gold. Comme l’évaluation du risque ne constitue pas une prédiction absolue d’un résultat spécifique, elle est par conséquent difficile à rattacher à des cas individuels et la validité de cette méthode ne pourrait être déterminée qu’après une longue période d’utilisation avec analyse rétrospective appropriée. Das Gesteinstechnikrisiko wird in dieser Arbeit als Funktion einer möglichen Bodenbewegung definiert; die Anfaälligkeit des Arbeitsplatzes; das Ausgesetztsein der Belegschaft; und ein genreller Begriff - Qualität der Informationen. Das Papier beschreibt die Entwicklung einer Prototyp-Software, die eine Kombination zwischen einem Expertensystemzugang für die Bestimmung der gesamten Risikobeurteilung ist, eine Empfehlung zur Risikokontrolle und eines fundamentalen GIS (graphisches Informationssystem) Zuganges für graphisch darüberliegende Eingangsparameter und das Outputrisiko. Das Expertensystem verwendet eine bayesische Wahrscheinlichkeitsannäherung, um verschiedene mit dem Arbeitsplatz in Verbindung stehende Informationen, ein quantitativ bestimmtes seismologisches Umfeld und das Ausgesetztsein des Untertag-Personals zu kombinieren, um eine gesamte RE-Risikobewertung zur Verfügung zu stellen. Die Risikobeurteilung ist insoferne dynamisch,daß sie stets nachkalkuliert wird wenn sich irgendeiner der Eingangsparameter ändert, z.B. jedesmal wenn ein seismischer Fall im Interessensbereich aufgezeichnet wird. Der Code wurde auf einem Datenbestand von Savuka Gold geprüft. Da die Risikobeurteilung nicht eine absolute Vorhersage eines spezifischen Resultates ist, es ist folglich nicht möglich, sich auf einzelne Fallstudien zu beziehen und die Zuverlässigkeit dieser Methode könnte nur nach einer umfangreichen Benutzungsdauer mit geeigneter Postanalyse bestimmt werden.

Jan 1, 2003

Notices THE FEDERATION OF SOCIETIES OF PROFESSIONAL ENGINEERS The following letter has been received from the Secretaries of the above Federation. Ref. EHvdL/MM/27 13/11/1973 TO THE SECRETARIES OF ALL MEMBER AND AFFILIATE SOCIETIES Dear Sir/Madam, ENTRIES IN TELEPHONE DIRECTORIES PAPERS OF INTEREST The following recently published papers may be of interest to memo bers. DIE FEDERASIE VAN VERENIGINGS VIR PROFESSIONELE INGENIEURS Die volgende brief is van die Sekretarisse van die bogenoemde Federasie ontvang. verw. EHvdL/MM/27 13/11/1973 AAN DIE SEKRETARISSE VAN ALLE LlD- EN GEAFFILIEERDE VERENI GIN GS Geagte heer/dame,

Jan 1, 1974

By H. Wagner

The paper points out that bord-and-pillar mining is the most important method of coal extraction in South African underground coal mines, and advocates that pillar design procedures should be refined to make more rational allowance for the differences in strength properties between various coal seams and roof and floor strata. However, any deviations from well-established design procedures must be based on sound engineering principles and reliable data on the strength properties of the seams and strata concerned. Recent information indicates that practices for the protection of surface structures against underground mining should be revised.

Jan 1, 1980

By W. K. Brinsden

The Australian Institute of Geoscientists (AIG) held their fifth successive annual seminar at Observation City, Scarborough, in Perth on 15th November, 1990. The title of the seminar was &apos;Strategies for Grade Control&apos;. The Seminar attracted 158 delegates, including 10 speakers. In addition to geoscientists, the attendees included mining engineers, metallurgists, and mining analysts. The welcoming address was given by Rob Duncan, Chairman of the Westem Australian Branch of AIG, who said there is a strong demand for this type of seminar in Western Australia (WA). It helps geoscientists to keep up with former colleagues and to keep abreast of technical developments.

Jan 1, 1991