Search Documents

Changes in reductant and energy inputs which are required to adjust the slag composition in anilmenite smelter to a higher or lower FeO content are calculated. The calculated changes are based on the assumption that solidification equilibrium with the freeze lining constrains the slag composition to follow a eutectic groove in the TiO2-FeO-TiO1.5phase diagram. Calculated equilibrium conditions along the eutectic groove are presented, and form the basis of the calculations. The inputs of energy and carbon need to deviate strongly from the steady-state values to adjust the slag composition. The inputs required at any given time depend on the desired rate of change of the slag composition, and the current slag composition. The steady-state relationship of a change in energy input of 5 kWh corresponding to a 1 kg change in carbon input does also hold for the changed inputs during transient changes in FeO content. Keywords: Ilmenite smelting, freeze lining, solidification, eutectic

Jan 1, 2003

By A. Hammel

This paper summarizes indigenous mining methods used to collectmetal ores in pre-colonial southern Africa, south of 15°S. These methods, for the purposes of discussion, are divided into sections inorder of increasing organizational complexity, from scavenging,which only required basic equipment and a relatively minimal division of labour, to underground mines, which necessitated complex planning to overcome obstacles such as the need for illumination and ventilation. Examples concerning the pre-colonial exploitation of iron, copper, tin, and gold have been taken from the archaeological literature. This review paper provides an introduction to the technology that was available to and used by miners in the past, illuminates some of the factors limiting their operations, and supports the claim to the indigenous nature of this activity

Jan 1, 2000

The paper deals with the importance of design and of codes of practice in ensuring safe working conditions in mines. The design principles involved in the design process are dealt with, and the importance of a logical design process is emphasized. The links between the requirements for developing a code of practice, embodied in the existing guidelines for the preparation of such a code, and the design principles and process are considered in some detail. Finally, suggestions are included, which may provide improvements to the code and hence, ultimately, lead to further improvement in safe working conditions.

Jan 1, 2004

By A. H. Swart

Rock engineering is concerned with the design of rock structures generated by mining activities. Therefore, rock engineering designs have major implications for the safe recovery of mineral deposits and operating costs. The paper deals with a few challenges facing rock mechanics engineers operating in the hard rock underground mining environment in South Africa. Finally, examples are included, which may assist rock mechanics engineers in providing better designs, which could ultimately lead to further improvement in safety and lower operating costs.

Jan 1, 2005

By A. C. du Preez

The separation of nickel and cobalt from calcium, magnesium and manganese by solvent extraction using synergistic mixtures of carboxylic acids was studied. Addition of certain viable synergists to commercially available tertiary branched carboxylic acids, such as Versatic 10 (Shell) or Neodecanoic acid (Exxon), produced large synergistic shifts (?pH50) in the pH50values for nickel, and small antagonistic shifts (negative ?pH50values) in the extraction of calcium. Under the initial test conditions used (0.50 M each of Neodecanoic acid and the Mintek synergist, in xylene) a large separation (pH50Ca? pH50Ni= 3.09 pH units) between nickel and calcium in their extraction from 1.00 M sodium nitrate solutions was obtained, compared with only 1.11 pH units in the absence of the synergist. The selectivity series for the extraction of divalent base metals from 0.333 M sodium sulphate solutions by 0.50 M Neodecanoic acid and 0.25 M of the Mintek synergist in C12-C13aliphatic diluent was found to lie in the order (with pH50values in parentheses): Cu(3.42) > Ni (5.08) > Zn (5.58) > Co (5.73) > Mn (6.62) > Ca (7.48) >Mg (8.25). In batch counter current experiments, a simulated leach liquor containing (in gL-1): Ni 5, Mg 5, Mn 2, Co 0.5, Ca 0.5, Cu 0.1and Zn 0.1 was contacted with the mixed extractant in three stages at unit phase ratio and an equilibrium pH of 5.9. The recovery of nickel was 99.9 per cent and that of cobalt was 84.7 per cent, whilst the co-extractions of manganese, calcium and magnesium were 2.7,1.5 and 0.04 per cent, respectively. The recovery of cobalt can be enhanced by employing a slightly higher pH, although this will also increase the extraction of manganese, calcium and magnesium somewhat. Nearly quantitative stripping (99 per cent) of nickel from the loaded organic phase was achieved in a single contact at an organic-to-aqueous phase ratio of 4 using a simulated spent electrolyte containing 39 gL-1sulphuric acid and 33 gL-1nickel,thereby producing an ?advance electrolyte? containing 57 gL-1nickelat pH 3.5. Loading of acid into the organic phase was very slight, amounting to only 0.002 M H+in contact with the above-mentioned spent electrolyte. Keywords: solvent extraction; synergism; nickel; calcium; carboxylic acids.

Jan 1, 2004

By R. E. Robinson

A novel variation of the GYPCIX process for the treatment of the acid mine effluent water from Grootvlei is described, in which a number of valuable by products can be obtained and the product water can be used for a variety of different purposes. A conceptual case study is presented in which the important cost parameters are described and certain critical path activities are indicated in order to derive a Return on Investment evaluation according to methods previously published. The study indicates that the treatment costs can be dramatically reduced, provided that proper utilization of the by products is taken into account. There are many possible uses for the water. However, by far the most advantageous contribution to the RDP and the best return on capital is derived if the water is used to establish small-lot farming activities providing work opportunities for thousands of people and contributing several hundred million Rands to the GDP. Vastly improved social conditions will be generated in an area of Gauteng that is in danger of rapid deterioration and a contribution will be made to maintaining mining activities in this area. The environmental impact is positive.

Jan 1, 1998

By P. J. D. Lloyd

At first I read this paper with interest, which grew to fascination, and ended up with horror. Such reactions to a supposedly scientific contribution are rare, and I believe the coal mining community must be warned in the strongest possible terms against the recommendations that this paper makes. The paper purports to have assessed statistically two sets of data on methane concentrations recorded in the return air from Turkish longwalls. The first set of data, from their Table I, is reproduced in Table I below. The data have been rearranged in classes to indicate the underlying distribution. While there is only limited data (N=33), the distribution looks as if it could be the sum of two normal distributions with means around 0.5 and 0.8, or possibly a log-normal distribution. What is quite clear is that it is nota single normal distribution.

Jan 1, 2004

By T. F. J. Hälbich

Namakwa Sands aims to conserve environmental resources and prevent or minimize environmental impacts from its operations. The challenge faced by Namakwa Sands is the rehabilitation of the arid winter rainfall Strandveld and lowland Succulent Karoo vegetation zones affected by its mining activities. Extensive experimentation with different rehabilitation methods resulted in the development of an effective rehabilitation programme. The use of topsoil as a seed bank and shade-cloth as windbreaks have significantly aided the rehabilitation process. The aim of the programme is to stabilize the soil environment so as to allow the germination and development of the local plant species. The ability to control wind erosion is critical to the success of the rehabilitation effort. A programme of biodiversity audits has been started to measure the recovery of plant species in the rehabilitated area. The principle of continuous improvement, coupled to site-specific rehabilitation studies, is applied to enhance the rehabilitation programme.

Jan 1, 2003

By J. H. Schubert

Mintek has developed a level-control system, FloatStar, for use in flotation circuits. Instead of controlling levels separately in each unit, the controller monitors levels throughout the circuit. It can thus take account of the global effects of any control actions. A collaborative project between Mintek and Karee Platinum Mine has begun, looking at aspects of flotation control. Karee plant was chosen as the site for this work because of its good existing control infrastructure. As a first stage of the joint project FloatStar was installed. Analysis during installation and running of the FloatStar has illustrated how circuit design and measurement technology can affect process control. Severe interactions have been observed in the levels of adjacent banks. The effect of FloatStar on flotation performance was tested and an improvement in level control was observed. Similarly, a faster settling of the plant after start-ups was observed. Both the improved level control and faster start-ups lead to higher platinum recovery.

Jan 1, 1999

By F. H. Abd EL-Rahiem

A selective dispersion process is presented and the work carried out to find optimum process conditions to minimise the colouring material in ground calcium carbonate (GCC) is described. The feed material is the overflow product from a hydrocyclone which results from using a Denver Attritioning machine with semi-autogenous grinding for one hour and a 1:1 ore/water ratio. By using sodium silicate (SS), with pH 9 and pulp density 5%, the iron content (as colouring impurities) is decreased from 0.21% in the original concentrate to 0.12% in the final concentrate. The degree of whiteness reached is improved to 85% from 63% in the original material. However, by using hexametaphosphate (SHMP) at pH 10 at the same pulp density, the iron content decreased to about 0.073% and hence the whiteness degree increased to about 96%.

Jan 1, 2004

By R. L. Lawson

I?ve been asked to appraise the global role of coal and mining, and the best place I can think of to begin is with the World watch Institute, which purports to monitor all things global. Last fall the institute?s magazine, entitled World Watch, in a cover story called for a worldwide campaign to outlaw the use of coal before this century?s end. To my mind the article began the campaign. However, the institute had to admit that no such ban will be possible unless there is special help and heavy intervention?that is, novel policies and punitive taxes. I?ll quote directly from the magazine to underscore the point: ?without them the market will continue to deceive us into thinking coal is cheap, abundant and irreplaceable?.

Jan 1, 2001

By C. Sensogut

The phenomenon of spontaneous combustion is one of the major hazards encountered in underground coal mines both from the safety aspects and on economic grounds. Every occurrence, however small, if not tackled effectively in the early stages can develop into open fire, or explosion of gas or coal dust. In terms of economy, even dealing with small incidents may be costly in terms of labour and materials, and in case of a sealing off of a district being necessitated, the loss of face equipment and sterilization of reserves is potentially great. Therefore, expense and effort in prevention and detection of such heating, together with a high state of readiness for dealing with likely event, is completely justified and may be considered as a sound investment. In order to achieve this investment, it may be worth to pinpoint the centre of the fire occurring due to autogenously heating which is supposed to be great assistance to inert it at a least cost and time. Therefore, it is the aim of this work to model the spontaneous combustion in the goaf.

Jan 1, 2002

By B. Elevli

The aim of this paper is to demonstrate the implementation of multicriteria analysis in selection of the most suitable underground ore transport system for a chromite mine in Turkey. The related problem includes five possible ore transport systems and six criteria to evaluate them. The adopted evaluation and ranking method for this study is PROMETHEE. PROMETHEE I revealed a partial order of alternatives where incomparability exists. PROMETHEE II gave the absolute ordering of alternatives. The results have shown that the PROMETHEE method can be successfully used in solving mining engineering problems. Keywords: multi-objective, decision analysis, mining, ore transport system

Jan 1, 2004

By H. Zhu, F. Xu, T. Wang

Abstract : The deformation monitoring data of the middle pier of the in permanent ship lock in Three Gorges revealed several interesting deformation phenomena. Conclusions and explanations are made concerning the phenomena in this paper, based on the finite element and engineering geology analyses. Firstly, the fluctuation of the horizontal transformations can be attributed to the alternate excavation of the two neighbouring ship lock rooms. Secondly, the rock mass discontinuities result in the displacement breaks. Lastly, the main reasons for the one-sided leaning phenomena are the natural stress, which is not evenly distributed, and the presence of discontinuities. This paper presents a valuable reference for studying the ‘individual phenomena’ in geotechnical engineering. ZUSAMMENFASSUNG: Die Beobachtungs claten an der Mittelpier deformation bezüglich Permannenter Schiffsschleuse in den Drei Schluchten offenbaren einige interessante Deformationsphänomene. Die Schlußforgerungen und Erklärungen dazu in dieser Arbeit basseren methodisch anf der ‚’ ‘Endlichen-Elemente-Analzse’ und der ‘Ingenieurnissen-Geograhnie-Analzse’. Erstens kann die Fluktuation der horiyontalen Transformation durch die ungleichzeitige Ausgrabung der zwei benachbarten Schiffsschleusenräume verursacht werden. Zweitens resultzert die Diskontinuität der Felsenmasse ans dem verlagerten Bruch. Drittens: Die Hauptgründe für das Zu-einer-Seite-Neigung-Phänomen in manchen Stellen sind der ungleich eigeteilte natürliche Druck und das vorhandersein der Diskontinuität. Diese Arbeit präsentiert eine wertvolle Referenz für die Untersuchung der Sonderfälle in geotechnischen Bau. Résumé: Cet article a analysé sérieusement et profondément , en utilisant des procèdes d’étude par exemple l’analyse d’éléments défini et celle de la condition géographique de traveaux , des règles typiques de la déformation montrées dans les données surveillantes à propos de la déformation des pierres centrales dans les écluses éternelles du Trois Gorges , on en a tiré une conclusion : 1) le changement des chiffres des déplacements horizontaux des pierres centrales est causé par les creusages séquentiels des cannelure voisines ; 2) l’inclinaison au Nord de toutes les pierres centrales entre les deuxième et troisième chambres d’écluse est causée par la différence de la gravitation entre les deux chambres d’écluse et par l’existence de la surface structurale ; 3) l’existence de la surface structurale cause le changement des chiffres des déplacements horizontaux des pierres centrales au niveau profond . Cet article donne une référence utile pour l’étude du ‘ problème d’indivudualité’( ou les situations anormaux) dans les données surveillantes de la déformation des pierres centrales de la génie civile.

Jan 1, 2003

Bacterial leaching represents an unusual problem in biochemical engineering, because the substrate for bacterial growth is not supplied directly, but is a product of another reaction, the leaching of mineral particles. Leaching arises from the bacterial oxidation of ferrous ions to ferric ions, which in turn oxidize the mineral. For the bacterial dissolution of pyrite, these reactions are: [ ] (Y represents a stoichiometric yield factor, and N represents the amount of bacteria.) Equations [1] and [2] represent a cyclic auto-catalytic system since more ferric ions are added to the system with an increase in the extent of leaching.

Jan 1, 2000

1. A statistical approach to some mine valuation and allied problems on the Witwatersrand. Unpublished Master?s Thesis, University of the Witwatersrand ? 1951. (Separate) 2. A statistical approach to some basic mine valuation problems on the Witwatersrand - J. of the Chem. Metall. and Min. Soc. of S.A., December, 1951 - discussions and replies March, May, July and August 1952. (Vol. 1?.1). Also: J. of the Institute of Mine Surveyors of S.A. December 1952, March 1953. (Vol. 1?2) 3. A statistical analysis of some of the borehole values of the Orange Free State goldfield - J. of the Chem. Metall. and Min. Soc. of S.A., September, 1952 - discussions and reply November 1952, and February 1953. (Vol. 1?3). 4. A study of the relationship between development values and recovery grades on the South African goldfields - J.S.A.I.M.M, January 1959, - discussion and reply April and October 1959. (Vol. 1?6) 5. On the departure of ore value distributions from the lognormal model in South African gold mines. J.S.A.I.M.M., November 1960, January and August 1961. (Vol. 1?8) 6. Developments in the valuation of gold mining properties from borehole results - Seventh Commonwealth Mining and Metallurgical Congress, 1961. (Vol. 1?9) 7. Effective pay limits for selective mining. J.S.A.I.M.M., January and August 1962. (Vol. 1?10)

Jan 1, 2014

By H. S. Marshall

Optimum Colliery is an opencast strip mine producing 18Mt of bituminous coal per annum for the export and inland markets as well as for domestic power generation at the Hendrina PowerStation. Coal is exposed by four 60m3 and four 11m3 walkingdraglines and transported from the open cuts to the processing plants by twelve 130 ton coal haulers. Overburden and interburden areas are drilled by nine 250mm-diameter rotary drill rigs. Until 1997 all surveying tasks were conducted by electronictotal stations requiring accurate control points from which line-of-sight XYZ readings could be taken. In 1997 a GPS system was introduced which consisted of a fixed base station and two rovers. The rovers were able to perform most of the survey tasks assigned to total stations. In addition, two overburden drills were equipped with blasthole drill navigation systems, which includes the drill monitoring and material (strata) recognitions system. The rest of the drilling fleet will also be equipped with GPS systems. Blasthole positions are designed in the office based on survey and geological/geophysical information and transmitted via radio link to an industrial PC on the drills. Together with GPS positional data, both the planned and actual drill positions are displayed on an LCD screen. This eliminates the need for surveyed hole positions to be staked before drilling, and for actual hole positions to be surveyed after drilling. As holes are drilled, performance and rock property data transmitted back to the office. Future applications will include GPS monitoring of dragline positions and pad elevations. GPS receivers on the draglines will utilize the existing base station to calculate and transmit XYZ co-ordinates. Another application will be locating of boreholes in the field prior to the pumping of specified explosive charges into the blastholes. Charging instructions for each blasthole will be loaded into the computer on the explosives truck which will be equipped with a GPS system for hole identification.

Jan 1, 1998

By J. W. Latilla, J. J. van Wijk

A running facebreak ahead of the powered support units occurred on the number 4 seam at Matla Coal’s number 3 shaft (Matla 3) in April and May 2002.Very difficult mining conditions were experienced for a distance of some 150 m in the tailgate and to a lesser extent on the face itself. The paper analyses the main causes for the high stress conditions leading to the facebreak, namely, the existence of a >20 m dolerite sill close to surface and the effect of stopping longwalling on the overlying 5 seam. Difficulties experienced during the facebreak are discussed, including, pillar and roof collapses in the tailgate, high stress areas ahead of the face causing roof and sidewall stability problems, flushing of broken rock into the face area at the tailgate, secondary mid-face breaks, and the availability of critical support units. Successful rock engineering interventions and learning points were that, a goaf angle of 14.6° was found to be more realistic than the previously used 20 to 25° in predicting dolerite sill behaviour in this area, pre-split blasting of the sill significantly reduced stress on the face and tailgate allowing re-support work to proceed, varying pillar support types were analysed and rated, the need to always have a ground control “First Aid” kit available was recognised and a strategy for subsequent panels beneath the sill was developed. Numerous support units were used and the performance of the more suitable types is briefly discussed. A running facebreak ahead of the powered support units occurred on the number 4 seam at Matla Coal’s number 3 shaft (Matla 3) in April and May 2002.Very difficult mining conditions were experienced for a distance of some 150 m in the tailgate and to a lesser extent on the face itself. The paper analyses the main causes for the high stress conditions leading to the facebreak, namely, the existence of a >20 m dolerite sill close to surface and the effect of stopping longwalling on the overlying 5 seam. Difficulties experienced during the facebreak are discussed, including, pillar and roof collapses in the tailgate, high stress areas ahead of the face causing roof and sidewall stability problems, flushing of broken rock into the face area at the tailgate, secondary mid-face breaks, and the availability of critical support units. Successful rock engineering interventions and learning points were that, a goaf angle of 14.6° was found to be more realistic than the previously used 20 to 25° in predicting dolerite sill behaviour in this area, pre-split blasting of the sill significantly reduced stress on the face and tailgate allowing re-support work to proceed, varying pillar support types were analysed and rated, the need to always have a ground control “First Aid” kit available was recognised and a strategy for subsequent panels beneath the sill was developed. Numerous support units were used and the performance of the more suitable types is briefly discussed. Une cassure de taille en avant des unités de soutènement s’est produise sur la veine numéro 4 dans le puits numéro 3 (Matla 3) de la mine Matla Coal en avril et mai 2002. Les conditions d’extraction étaient extrêmement difficiles sur une distance d’environ 150 m dans la voie de tête et, en moindre mesure, sur le front de taille lui-même. L’étude présente analyse les raison majeures pour les conditions de grandes contraintes qui ont conduit à la cassure de taille, à savoir l’existence d’un mur de dolérite de >20m proche de la surface et l’effet d’arrêter la longue taille sur la veine 5 superposée. Les difficultés rencontrées pendant la cassure de taille sont rapportées, y compris les effondrements de piliers et toit dans la voie de tête, les aires de grandes contraintes en avant du front de taille causant des problèmes de stabilité pour le toit et les parois latérales, l’injection de roches cassées dans la taille en voie de tête, les cassures secondaires à mi-taille, et la disponibilité d’unités de soutènement critiques. Interventions minières réussies et leçons apprises furent : un angle de remblai de 14.6° était plus réaliste que celui de 20 à 25° utilisé auparavant pour prédire la conduite du mur de dolérite dans cet endroit ; tir à deux temps du mur a réduit considérablement les contraintes sur la taille et la voie de tête, ce qui a permis un travail de support complémentaire ; des types variés de support de piliers furent analysés et évalués ; la nécessité d’avoir toujours une trousse de première urgence disponible fut reconnue ; et finalement une stratégie pour les panneaux en dessous du mur fut

Jan 1, 2003

By G. Broadbent

It is an honour to be invited as a speaker to this ICCR conference and a pleasure to be with you here in South Africa. I have been asked to talk about the competitiveness of coal versus other energy alternatives. Coal supplies nearly one-quarter of the global primary energy. Its most direct competitors are gas, nuclear and renewables. Oil is predominantly for transport fuels. Fuel oil is competitive with coal when crude is below its long-run average price and has some niche opportunities. But I will confine my comments to nuclear, renewables and particularly natural gas as the most potent current competitive threat to coal. Competitiveness is more than just cost and price; there is environmental acceptability, security or reliability and increasingly image. These factors are more of a spectrum than discrete issues. Dollars and cents remain the key issue for competitiveness but one must recognize the impact of politics in sustainable development and energy security.

Jan 1, 2001

Outsourcing of specialist and non-continuous services is common practice in international mining operations. There is an increasing trend towards this practice in South Africa as a result of the major organisational changes that have taken place in the industry, and as lower revenues and production cost pressures have reduced profit margins. Many specialist functions have been outsourced in the industry for a long time, an example being shaft sinking, which is undertaken by specialist shaft sinking contractors. In the professional services area, some activities have been outsourced, for example the design and construction supervision of tailings dams, but mining related activities such as geology, mine planning and scheduling, engineering, ventilation, and rock engineering, have traditionally been carried out by in-house staff. In this paper some of the industry problems which have led to an increase in outsourcing of professional services are considered. Then the pros and cons of outsourcing are dealt with before outlining the factors which should be taken into account in choosing an outsourcing partner.

Jan 1, 1999