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By J. M. Font, R. G. Reddy

Jan 1, 2004

By J. Eriksson

Slag from stainless steelmaking is known to disintegrate, which is an environmental problem and prevents the cooled slag from being utilized. This disintegration is due to the transformation from the ßto the ? polymorph of di-calcium silicate. The transformation is accompanied by an increase in volume of about 11% and a total disintegration of the slag. AOD slag from stainless steelmaking was re-melted in a laboratory induction furnace, together with olivine and calcinated dolomite, to investigate the prevention of disintegration by increased MgO content of the slag with small changes in CaO to SiO2ratio. The modified slag was examined with X-ray diffraction and scanning electron microscopy. The trials showed that an increased MgO content can change the mineral composition towards formation of more Merwinite and Bredigite, which prevents disintegration of the slag. Keywords: slag, disintegration, di-calcium silicate

Jan 1, 2004

By H. Hamma, R. Fehrmann, M. Gaune-Escard, G. Hatem, S. B. Rasmussen, K. M. Eriksen

The molten salts M2S2O7and MHSO4, the binary molten salt systems M2S2O7-MHSO4and the molten salt-gas systems M2S2O7-V2O5and M2S2O7-M2SO4-V2O5(M = Na, K, Rb, Cs) in O2, SO2and Ar atmospheres have been investigated by thermal methods like calorimetry, Differential Enthalpic Analysis (DEA) and Differential Scanning Calorimetry (DSC). Fundamental thermodynamic data like temperatures and molar heats of solid-solid transition and fusion, phase diagrams, heat capacities of solids and liquids, heat of mixing, and heats of complex formation have been obtained and are reviewed here. Also EPR spectroscopic evidence of V(IV) complexes and their structure are reported and the results are discussed in relation to the mechanism of SO2oxidation by V2O5based industrial catalysts. Keywords: Alkali pyrosulfates, alkali hydrogen sulfates, vanadium pentoxide, EPR spectroscopy, complex formation

Jan 1, 2004

By A. D. Thomas

Some years ago, the authors developed an analysis of non-Newtonian pipe flow based on enhanced turbulent microscale and associated sublayer thickening. This analysis, which can be used for various rheologic modelling equations, has in the past been applied to smooth-walled pipes. The present paper extends the analysis to rough walls, using the popular Bingham plastic equation as a representative rheological behaviour in order to prepare friction-factor plots for comparison with measured results. The conditions for laminar-turbulent transition for both smooth and rough walls are also considered, and comparisons are made with earlier correlations and with experimental data.

Jan 1, 2007

By D. Xie, S. Sun

An overview of recent development of CSIRO?s Multi-Phase reaction models will be presented with examples comparing the calculated physico-chemical properties of metallurgical slags with the existing experimental data. The paper will also outline the development of a kinetically based model for molten bath reactors and its application to submerged combustion of coal in a slag bath as well as the reaction between the slag and injected coal particles. The plume model combines established models for the combustion of pulverized fuel with models for the growth and rise of bubbles from a lance or tuyere. This model predicts the extent of de-volatilization and combustion of the coal in the plume, the utilization of oxygen and the exchange rate of oxygen between the gas and the bath as well as the heat transfer rate between the gas bubbles and the bath. The slag reduction model brings together the recently measured rate data and fundamental understanding of the kinetics of CO-CO2reaction with iron oxide containing slags and predicts the changes resulting from injection of coal particles into molten slags. The top-space model covers reactions between gases and molten droplets in the post-combustion zone, where heat and mass transfer between phases results in higher utilization of the fuel values in the partly oxidized gases and transfer of heat to the molten bath. Keywords: Phase equilibria, viscosity, electrical conductivity, slags, kinetics, reaction rate.

Jan 1, 2004

By D. F. Malan, M. Grave, J. A. L. Napier

Previous fundamental research projects have indicated the value of continuous closure measurements in deep tabular excavations for improved support design, hazard assessment and for quantifying the effect of seismicity on stope closure. This paper describes further measurements in a VCR stope to validate some of the earlier findings. Calculation of the closure ratio showed that it is a good measure to identify different ground conditions and possible hazards. This work was supported by numerical modelling results, which showed that the closure ratio is very useful in discriminating the response of different geotechnical environments. Des projets précédents de recherche fondamentale ont démontré la valeur de mesures continues de fermeture dans le cas de profondes excavations tabulaires pour une conception améliorée du soutien, de l’évaluation du danger et pour quantifier l’effet de la séismicité sur l'affaissement du toit d’un chantier d’abattage. Le présent document décrit d’autres mesures dans un chantier d’abattage VCR afin de valider certaines des conclusions précédemment formulées. Le calcul du degré d'affaissement montre qu’il y va de soi d’identifier différentes conditions de sol ainsi que les dangers possibles. Les présents travaux ont été confirmés par des résultats de modélisation numérique, lesquels ont démontré que le taux d'affaissement est très utile quant à discerner la réponse dans des environnements géotechniques différents. Vorherige Forschungsprojekte haben den Wert von kontinuierlichen Setzungsmessungen im tiefen Sudafrikanischen Strebabbau angedeutet, vor allem fur Ausbaudesign und Risikobewertung, als auch fur die quantitative Bestimmungen der seismizitatsabhangigen Setzung. Dieses Referat beschreibt weitere Messungen in einer VCR Grube um fruhere Bestimmungen zu bewerten. Dass errechnete Konvergenzverhaltniss erweiste sich als eine gute Massnahme zur bestimmung von geotechnischen Zonen und moglichen Risiken. Numerische Analyse unterstutzte die vorliegende Arbeit und deutete darauf, dass das Konvergenzverhaltniss sehr brauchbar ist um Verhaltensunterschiede der geotechnischen Zonen zu erproben

Jan 1, 2003

By C. S. Chenga

Sustainable development is currently an extremely relevant concept worldwide, especially in developing countries like South Africa. Mining and metals companies are also directly affected by the sustainable development agenda. The Mining Charter?s requirements as well as new legislation (Mineral and Petroleum Resources Development Act) expect, among others, for mines to support infrastructure and poverty eradication projects in the communities surrounding the mines. The aim of this paper is to, against the background of a qualitative study of mining communities in the North-West Province of South Africa, put forward some critical factors for the sustainability of social development projects in the mining sector.

Jan 1, 2006

By F. A. Camisani-Calzolari

The latter half of the 20th century has seen the proliferation of a series of codes to address commodity needs which were brought about by rapidly advancing technologies and the globalization of markets and consumerism. This paper addresses the specific needs and the origin of this surge and presents these codes in the context they were developed. It also compares the main codes or groups of codes and elaborates upon their strengths and weaknesses. Three main categories of codes are identified, namely: codes for reporting to international agencies, codes addressing government needs and, finally, codes for the investors and the stock market. Codes governed by international agencies usually relate to strategic commodities which have highly specialized fields of usage like nuclear power generation where international cooperation is eventually the only viable approach for both the development of technologies and their applications. Codes for reporting to governments address the necessity of each state to exploit their mineral potential profitably and to secure the preservation of wealth for future generations. Reporting to investors is experiencing a considerable popularity as of late because of globalization in mining and the growing need for outside financing of mining projects, whose capital requirements are getting out of reach for the average mid-cap mining company. All these codes have advantages and shortcomings dictated by the specific circumstances under which they were developed, therefore necessitating the definition and implementation of some kind of international standard whereby investments and the spread of information across political boundaries would be facilitated. Though none of these codes might ever become international in the true sense of the word because of significantly different legislations at national level, a step that would greatly contribute to the cross-border disclosure of information would be the reciprocal recognition of competent persons by the major mining countries, including China and Russia. It is also becoming essential that financial institutions and investors be properly advised on mining projects by reporting reserves and resources in a transparent and responsible way with the relevant public disclosures being compiled by professionals who take full responsibility for their submissions. Keywords: reporting codes, mineral resources, mineral reserves, competent person, UN Framework Classification, IAEA classification, JORC Code, SAMREC Code and CRIRSCO.

Jan 1, 2003

By T. E. Pogue

This paper traces the co-operative initiative undertaken by South Africa?s gold mining companies through the Chamber of Mines Research Organization (COMRO) in development of hydraulic technologies. After a brief description of the structure of these technologies? development under COMRO?s stewardship, the paper turns to an overview of the structure of innovation within which these hydraulic technologies were developed. A central focus of this paper is systematic review on whether similar technologies are likely to emerge in the present system of innovation and the role played by innovation policy.

Jan 1, 2006

By S. K. Murphy, K. B. Le Bron, A. K. Ward, S. Hayes, T. Rangasamy

A process for evaluating different options for extraction of mining blocks is presented. The process is described and an example of the application of the process to a case study is presented. Un procédé pour évaluer différentes options pour l’extraction de blocs d’exploitation est présenté. Le procédé est décrit et un exemple de l’application du procédé à un cas particulier est présenté. Ein Prozeß für das Auswerten der unterschiedlichen Optionen für die Extraktion von Abbaublöcken wird dargestellt. Der Prozeß wird beschrieben und ein Beispiel der Anwendung des Prozesses zu einer Fallstudie wird dargestellt.

Jan 1, 2003

By Marko Lampi, Marc Nicolle, Janne Karonen, Kari Valkama

"In the ten years from 2003 to 2013 global mine production of copper has increased by over 23% to meet demand while the weighted average head grade has dropped from 0.9 to 0.7% Cu. These divergent trends of increasing demand and declining economic grades will extend the life of many existing mines and improve the viability of marginal and/or complex copper deposits. Against that context this paper outlines hydrometallurgical copper sulphide leaching options as alternatives to the more conventional pyrometallurgical processing route of copper sulphides. Three copper sulphide leaching and refining processes are discussed: total pressure oxidation, ferric sulphate leaching and copper chloride leaching. The effect of mineralogy on the choice of processing technology is discussed as well as some of the unit processes used. Additionally, possible benefits that a hydrometallurgical process may offer over an existing pyrometallurgical route are discussed. Subsequently, two very important aspects to the development of projects involving the leaching of copper sulphides are discussed. Finally, a number of conclusions are presented that will be useful to keep in mind when considering projects involving the leaching of copper sulphides. INTRODUCTION In the ten years from 2003 to 2013 global mine production of copper has increased by over 23% to meet demand while the weighted average head grade has dropped from 0.9 to 0.73% Cu (Murphy, 2014). If these divergent trends of increasing demand and declining economic grades continue, they will contribute to the extension in life of many existing mines and improve the viability of marginal and/or complex copper deposits. Against that context, this paper outlines hydrometallurgical copper sulphide leaching options as alternatives to the more conventional pyrometallurgical processing route for copper sulphides. Three copper sulphide leaching and refining processes are discussed: total pressure oxidation, ferric sulphate leaching and copper chloride leaching. Ferric sulphate leaching and copper chloride leaching are carried out at atmospheric pressure while total pressure oxidation takes place at elevated pressures."

Jan 1, 2015

By H. J. Glass

Collection, preparation, and analysis of blasthole chippings is expensive. Frequently, interpolation of grades at unsampled locations is considered using techniques like kriging. A pre-requisite for kriging is that an experimental variogram is established. In order to assess the quality of the experimental variogram, a measure is developed in this paper. The measure is derived from analysis of the time-honoured expression relating the variance, semivariance, and covariance. It reflects the weighted average deviation of the summed semivariance and covariance from the biased variance. The proposed measure allows assessment of the influence of key variables on the quality of the variogram. Using simulated data, it follows that the quality improves with an increasing number of samples, increasing density of the sampled locations, increasing regularity of the sampling pattern, and increasing uniformity of grades in the absence of correlation. Application to real data shows that the minimum number of samples could coincide with a marked decrease in the value of the measure. Establishing a threshold value is subject to further research. Keywords: variogram, variance, covariance, semivariance, minimization, sampling.

Jan 1, 2003

By S. Lin

A new hydrogen production process, named the HyPr-RING, has been proposed. Fundamental concept of the HyPr-RING is integration of water carbon reaction, water-gas shift reaction and CO2 absorbing reaction in a single reactor. Firstly, thermodynamic analysis was done to judge the possibility to realize the process. It was found that high pressure and temperature condition, such as 20 MPa and 1000 K, is required to promote this integrated reaction. Next, experimental verification of the new process was done under the high pressure and temperature reaction conditions. As the results, integration of above three reactions in a single reactor can be done successfully and produced a large amount of hydrogen as estimated by thermodynamic analysis. Experiments showed that organic materials including coal, heavy oil, biomass, plastics can be used in this process. In the gaseous phase, no pollutants such asH2S, SO2, COS are detected so that gas cleanup system is not required for power generation when this process is used. Finally, a process design was made to estimate process efficiency. Theoretically, 1 mole of carbon can generate 2 moles of hydrogen and cold gas efficiency of this process estimated as more than 80 per cent. The process potentially reduces hydrogen production cost compared with the conventional hydrogen production methods. Keywords: Hydrogen, Fossil fuel, Energy, Process, Supercritical water

Jan 1, 2001

By A Weber, L MacNamara, H Schreiber

Design and development of the world?s largest flotation cell was completed in 2002. This was the first 257 m3 flotation cell installed in the mineral industry and represents a major development in the design of larger flotation cells. This cell has a 50% increase in volume over the widely installed 160 m3 WEMCO® Smartcell? flotation machine. In the next few years it is anticipated that 257 m3 flotation cells will be incorporated into rougher-scavenger flotation circuits in many more world class copper sulphide concentrators. The prototype 257 m3 cell, No.250 Smartcell? flotation machine was installed at Minera Los Pelambres in the front of Row 1 in the existing rougher flotation circuit. This cell is followed by nine No. 130 Smartcell? flotation cells. After the successful development phase, this unit has been incorporated as part of a row of No. 250 Smartcell? flotation machines at Minera Los Pelambres. A key to the successful development of the equipment has been the emphasis placed on fundamental hydrodynamic scale-up criteria. Hydrodynamic factors include superficial gas velocity, water (pulp) circulation through the draft tube, and pulp mixing (distribution) characteristics. This paper will review the scale-up criteria of the No. 250 flotation cell, and present a case study of the in-plant equipment testing. The case study will document the metallurgical and hydrodynamic performance of the machine. It will also illustrate the economic benefits derived by incorporating larger flotation cells in a modern copper sulphide concentrator.

Jan 1, 2007

By E. Chen, M. Barati, K. Coley

The reaction between carbon and slags is of significant importance in direct smelting of iron ores, EAF slag foaming and copper slag cleaning processes. This reaction is known to occur via gaseous intermediates and it is important to have fundamental data to understand the relative importance of each reaction step. In this study, the rate of CO2dissociation on different slag surfaces is measured using an isotope exchange technique. It was found that increasing iron oxide content up to 30 wt per cent does not have a significant effect on the rate constant while increasing from this limit, increases the rate constant dramatically. Activation energy of CO2dissociation on slags of unit basicity and different iron oxide contents is in the range of 180±40 kJ/mol. It is found that rate constant dependence on oxygen potential in the slag phase is increasing with iron oxide concentration. In the case of copper making slags, the influence of copper oxide is found to increase the magnitude of apparent rate constant, while decreasing the activation energy considerably. Key words: Gas-slag reaction, CO2dissociation, copper slag, kinetics, isotope exchange

Jan 1, 2004

By L. Jurca, C. Gligor

After 1990, a great process of re-organisation and economic reform has occurred in the Romanian mining sector and especially in the pitcoal mining in the Jiu Valley. This process has included both legislation and the main aspects for getting an economic efficiency in the environment issues and for dealing the problems with social impact. Accordingly, starting with the year 1993 a new mining method has been introduced to turn efficient the pitcoal mining, and we speak about mining with caved in bed. This method has two variants: - with transverse strips and caved in bed; - with long face and caved in bed. Each of the above-mentioned variants has in turn several subdivisions, depending on how the longwall is prepared and on other characteristics. By using this method, the output has increased compared to other mining methods. The main safety aspects concerning caved in mining refer to: - great emissions of methane; - technical aspects (a mining method system, supports, discharging process); - pressure driving (analysed for the case of mining with long face, with transverse strips as well for the case of transverse strips when mining a subsequent sublevel).

Jan 1, 2003

By L. Jeffrey

The Waterberg Coalfield has vast potential to become a significantmining and industrial centre in South Africa. Its future developmenthinges on a number of critical decisions that must be made jointly by government, power utilities and industry, and on some technical and economic challenges that must initially be overcome. Sufficient water is the primary key to enabling exploitation, together with an adequate market for the large volumes of low-grade coal. As the most likely consumer of this coal will be either a power station or a petrochemical complex, the need for additional energy will be a driving force in the development of this coalfield. Conventional mining methods can exploit the shallow coal resources in both the Grootegeluk and the Vryheid formations, but alternative technologies such as coalbed methane extraction and underground coal gasification are the only currently known technologies that may be able to exploit the deep Grootegeluk Formation resources. However, extensive research is still required into these procedures, particularly with respect to the Waterberg coals. Transport infrastructure to the region is currently not sufficiently well developed to support large-scale exploitation of the region?s coal resources. In particular, the railway line would have to be extensively upgraded to allow the increased export of coal. Alternative transport methods such as pipelines would also have to be pursued to serve a large Sasol-type petrochemical complex or coal gas extraction. The road network would also require improvement, as only the roads between the main commercial centres are currently tarred. Dr Con Fauconnier, Kumba CEO, concluded his presentation to the Investing in African Mining Conference 2004 with the words: Again, it?s all about infrastructure? when it?s there, it enables the development of bulk mining projects which attract the resultant economic benefits for the region and country as a whole. These words aptly sum up one of the stumbling blocks to the future development of the Waterberg Coalfield.

Jan 1, 2005

[Ferro Alloys Producers Association The South Africa Institute of Mining and Metallurgy www.saimm.co.za Mintek www.mintek.co.za Eskom www.eskom.co.za ]

Jan 1, 2004

By T. S. Seleka

Laser surface melting has been conducted on a 304 stainless steel (SS) with the aim of enhancing pitting corrosion resistance of the material. This process involves rapid melting of the material?s surface followed by rapid solidification to refine the microstructure. This includes the dissolution of inclusions such as MnS, FeS, CrxCy, and other minor constituents. The microstructures as a result of laser treatment were observed by means of optical microscope and also confirmed by the XRD. The glow discharge optical emission spectroscopy (GDOES) was utilized for chemical analysis. Changes in hardness were observed by using a Vickers microhardness tester. Pitting corrosion tests on laser treated and untreated samples were conducted according to ASTM G48-92 to evaluate mass loss and pitting morphology. Laser surface melting improved the pitting corrosion resistance of this material in a chloride-containing environment.

Jan 1, 2007

By T. Dlokweni

Several Rockmass classification systems have been developed and used in Civil Engineering design and for underground mining operations. Some of these rockmass classification systems have been modified and used in the South African coal mining industry to quantify descriptive geological information for use in coal mine design and roof support selection. The Coal Mine Roof Rating (CMRR) system developed in the USA has been investigated in detail as part of the study. Advantages and disadvantages of the system have been identified by means of underground and surface borehole testing. Investigations into the rating systems in South Africa found that most of the rating systems used in the South African coal mining industry are for planning purposes, and are conducted on borehole cores. This study also highlighted that the rating systems being used are based on geology, and that the human factor plays a major role in the rating systems. To overcome these problems, all the classification systems used in South African coal mines have been benchmarked against impact splitting technique and documented. The best elements of these systems are combined into a new standard system that will be easily used by all mine geologists and rock mechanics engineers. Plusieurs systèmes de classification de la masse rocheuse ont été développés et utilisés dans le Génie Civil et pour les opérations d'exploitation minière souterraine. Certains de ces systèmes de classification de la masse rocheuse ont été modifiés et utilisés dans l'industrie minière sud-africaine pour quantifier l'information géologique descriptive utilisée dans la conception de mines de charbon et la sélection de soutènement du toit. Le système d'Evaluation de Toit de Mine de Charbon (CMRR) développé aux USA a été examiné en détail, comme part de l'étude présente. Tests en surface de trous de mine ont permis d'identifier les avantages et inconvénients du système. Une étude des systèmes d'évaluation en Afrique du Sud a révélé que la plupart des systèmes d'évaluation utilisés dans l'industrie minière sud-africaine sont utilisés pour la planification, et sont menés sur les carottes de trous de mine. L'étude présente a aussi souligné que les systèmes d'évaluation utilisés sont basés sur la géologie, et que le facteur humain joue un rôle majeur dans les systèmes d'évaluation. Pour surmonter ces problèmes, tous les systèmes de classification utilisés en Afrique du Sud ont été référencés en termes de technique de fissuration sur choc, et documentés. Les meilleurs éléments de ces systèmes sont combinés dans un nouveau système standard qui sera utilisé aisément par tous les géologues de mine et les ingénieurs miniers. Verschiedene Gesteinsmassenklassifikationssysteme wurden entwickelt und kamen im Design für Hoch- und Tiefbau und Untertageabbau zum Einsatz. Einige dieser Gesteinsmassen-klassifikationssysteme wurden modifiziert und sind in der südafrikanischen Kohlebergbauindustrie in Verwendung, um beschreibende geologische Informationen für die Anwendung im Design von Kohlebergwerken und der Firstabstützungsauswahl quantitativ zu beschreiben. Das in den USA entwickelte Kohlengrubenfirstbewertungssystem (CMRR) wurde als Teil der Studie im Detail untersucht. Vorteile und Nachteile des Systems sind mittels der Untergrund- und Oberflächenbohrlochprüfung gekennzeichnet worden. Prüfungen der Bewertungssysteme in Südafrika ergaben, daß die meisten Bewertungssysteme die in der südafrikanischen Kohlebergbauindustrie benutzt werden, Planungszwecken dienen und werden anhand von Bohrlochkernen durchgeführt. Diese Studie hob auch hervor, daß die verwendeten Bewertungssysteme auf Geologie basieren und daß der menschliche Faktor eine Hauptrolle in den Bewertungssystemen spielt. Um diese Probleme zu überwinden, wurden alle in südafrikanischen Kohlengruben benutzte Klassifizierungssysteme vergleichsweise in Hinblick auf Spaltschlagtechnik überprüft und dokumentiert. Die besten Elemente dieser Systeme werden in ein neues Standardsystem kombiniert, das leicht von allen Grubengeologen und von Gebirgsmechanikingenieuren benutzt werden kann.

Jan 1, 2003