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By J. H. Potgieter

This paper describes two cases of corrosion that occurred in dry-process, rotary, cement-clinker kilns. In the case of the kiln with five pre-heater stages, the attack occurred primarily from sulphates that probably originated in the raw feed and fuel being used in the plant and that penetrated the refractory lining. The corrosion was similar to ash-deposit corrosion often observed in steam boilers. In the second case the plant consisted of a long dry kiln with a single pre-heater fitted to the feed-end. In this case the corrosion could be ascribed to alkali chloride penetration through the refractory-brick lining and subsequent hot corrosion of the kiln shell.

Jan 1, 2004

By S. M. Rupprecht

"SynopsisThis paper is intended to document recent personal thoughts, opinions, and debate around the South African Code for the Reporting of Exploration Results, Mineral Resources and Mineral Reserves (the SAMREC Code) (2009) and its current usage by Competent Persons. Admittedly, some debates are as old as the SAMREC Code itself and have been ‘parked’ as no consensus could be reached by members of the SAMREC Working Group.Some of the more critical issues currently under examination are the definition of Competent Person and the potential registration of Competent Persons, the current re-write of the Code, and the introduction of reporting of Exploration Results, Mineral Resources, and Mineral Reserves on an ‘If not – why not’ basis, noncompliance with the Code and discipline, the role of the Johannesburg Stock Exchange Readers Panel, and the valuation of mineral assets based on scoping studies.IntroductionThis paper is intended as a personal memoir of recent thoughts and debate around the South African Code for the Reporting of Exploration Results, Mineral Resources and Mineral Reserves (the SAMREC Code) (2009) (‘the Code’). Admittedly, some debates, such as reporting of Mineral Reserves inclusive or exclusive of the Mineral Resource, are as old as the SAMREC Code itself and have been ‘parked’ as no consensus could be reached by members of the South African Mineral Resource Committee (SAMREC) Working Group. The author, who has been involved with the SAMREC Working Group since 2007, offers observations in his personal capacity as a professional mining engineer with the intent of getting practitioners to contemplate the influence of the Code on the mineral industry. Current practices in the compilation and reporting of Exploration Results, Mineral Resources, and Mineral Reserves are often deficient in adhering to the Code and a conscious effort must be made by the mining sector to improve the standard of public reporting, in particular Competent Person Reports (CPRs) and Public Reports issued by listed mineral exploration and mining companies."

Jan 1, 2015

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

Cokriging uses a sparsely sampled, but accurate and precise primary dataset, together with a more abundant secondary data-set, for example grades in a polymetallic orebody, containing both error and bias, to provide improved results compared to estimation with the primary data alone, as well as filtering the error and mitigating the effects of conditional bias. The method described here may also be applied in polymetallic orebodies and in other cases where the primary and secondary data could be collocated, and one of the data-sets need not be biased, unreliable, etc. An artificially created reference data-set of 512 lognormally distributed precious metal grades sampled at 25×25 m intervals constitutes the primary data-set. A secondary data-set on a 10×10 m grid comprising 3200 samples drawn from the reference data-set includes 30 per cent error and 1.5 multiplicative bias on each measurement. The primary and secondary non-collocated data-sets are statistically described and compared to the reference data-set. Variograms based on the primary data-set are modelled and used in the kriging of 10×10 m blocks using the 25×25 m and 50×50 m data grids for comparison against the results of the cokriged estimation. A linear model of coregionalization (LMC) is established using the primary and secondary data-sets and cokriging using both data-sets is shown to be a significant improvement over kriging with the primary data-set alone. The effects of the error and bias are filtered and removed during the cokriging estimation procedure. Thus cokriging using the more abundant secondary data, even though it contains error and bias, significantly improves the estimation of recoverable reserves.

Jan 1, 2014

By J. J. Bezuidenhout

The waste-heat boiler is used within the Sulphide flash smelting process as the main dust and energy recovery unit. The large volume of off-gas discharged from the flash smelter is at a very high temperature (1350°C) and contains a significant dust load that subjects the downstream waste-heat boiler to tough and demanding conditions. The boiler cavity is especially prone to dust accretions, fouling, and corrosion caused by accumulation of molten particles and precipitation of sulphuric acid. Computational fluid dynamics (CFD) is applied within a qualitative study to model the flow and heat transfer distribution throughout the waste-heat boiler. The commercial CFD package, Fluent 6.2.16, was applied to a modified waste-heat boiler (23 m ×11 m ×5.4 m) within the Outokumpu flash smelting process. This investigation focuses on the geometric modifications to the typical boiler design, which includes elevation of the ceiling, placement of flow-obstructing baffles and radiation plates parallel within the flow path. Also investigated were various boiler operating conditions such as the circulation of process off-gas, air leakage from the dust discharging hoppers and variation in inlet gas composition. The geometric modifications had the desired effect of increasing the volumetric utilization and therefore enhancing heat transfer between the boiler surface and the gas stream and dust segregation. Introducing circulated off-gas at a rate of 20 m/s and at a 45° angle to the front of the waste boiler further enhanced cooling while reducing the high impact of the furnace-uptake gas-stream on the boiler ceiling. The placement of radiation plates was found to be very effective in enhancing the heat transfer surface and distributing gas flow within the boiler. These results present recommendations towards an improved waste-heat boiler design. Keywords: flash smelting, waste-heat boiler, CFD simulation, off-gas cooling.

Jan 1, 2008

This paper pays tribute to the pioneers in geomechanics, and addresses some of the most pressing issues of our time related to deep mining, and how to mitigate these issues. Solutions developed by our predecessors seem to have reached their limits as mines continue to go deeper. The International Society for Rock Mechanics (ISRM) guidelines for rock mass characterization for excavation design also require re-thinking to reflect current knowledge and experience. Thus, a whole new approach is urgently required to increase mine safety and productivity. The paper will draw on the challenges and experiences in medicine and science that have been overcome through genuine collaboration, advances in technology, and impressive funding, which can be adopted to provide solutions to contemporary geomechanics challenges for increased safety and productivity as mines continue to go deeper.

Jan 1, 2014

By A. Wedepohl

Selective leaching of phases in charge chrome is used in a variety of industrial processes for the production of chromium chemicals. A mineralogical study was made of a range of local charge chrome samples, at various stages of leaching in sulphuric acid (20g/l at 90°C), using mainly a scanning electron microscope (SEM) together with an energy-dispersive spectroscopy analyzer (EDS), and X-ray diffraction techniques. It was found that the leaching behaviour of the different types of charge chrome depends largely on the nature of the secondary phases, which in turn depends upon whether the silicon content is above or below 4 per cent by mass. The leaching behaviour of high-chromium ferrite is anomalous, and it is postulated that the process is analogous to the corrosion of brass by dezincification. Keywords: charge chrome leaching, scanning electron microscope

Jan 1, 2000

By M. Sanchez, C. Morales, J. Palacios

The slag produced in the Peirce Smith converters at the Ilo smelter of Southern Peru Copper Corporation has shown a wide range of magnetite content, which introduces an additional problem in the smelting units due to materials? recirculation. However, the operation data analysis and the application of thermodynamic concepts have made it possible to produce slag with magnetite content between 18 and 20%. The results have suggested that matte grade enhances magnetite formation while silica controls its precipitation, and they are also influenced by the increasing temperature of the slag. Thus, in order to obtain the required magnetite content in the slag, matte grade is gradually enriched in equilibrium with slag containing from 25 to 32% silica.

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 J. M. Lottering

Paper written on project work carried out in partial fulfilment of B Eng (Chem) degree Operational factors influencing the electrostatic separation of mineral sands were investigated in a laboratory separator. Measurements were collected online by means of an optical sensor using diffused reflectance spectroscopy to determine the mineralogical composition. The results have shown that the roll speed and potential were the dominant operating variables, collectively explaining more than 83% and 68% of the product grade and yield, respectively. In contrast, the feed rate, temperature and position of the plate did not affect separation. The effect of the ambient relative humidity, ranging from 10% to 45%, could not be assessed conclusively and at best appeared to have a weakly beneficial effect on the product grade. Keywords: process modelling, high tension roll separator, mineral sands

Jan 1, 2006

By J. E. Nesset

The bubble size, together with the gas rate, determines the bubble surface area flux in flotation machines and, therefore, impacts directly on the kinetics of flotation. Understanding the variables that influence bubble size is one of the keys to understanding flotation recovery. Surprisingly, these relationships are poorly understood, largely due to the difficulties associated with gas dispersion measurements in industrial environments. The McGill gas dispersion sensors (bubble size, gas rate, gas holdup) are capable of reliably making such measurements. This paper reports on a study, using the McGill sensors in a 0.8 m3 Metso RCSTM pilot cell, which investigated the effect on bubble size of frother type and concentration, gas rate, temperature and rotor speed. A Denver laboratory cell was used to investigate the effect of elevation above sea level. Frother concentration proved to have the predominant influence on bubble size, and the effect of frother type can be normalised as a function of the critical coalescence concentration (CCC). Measurements made at many plant sites worldwide are compared to the model developed using the Metso RCSTM unit.

Jan 1, 2007

By A. B. Fox, R. P. Thackray, K. C. Mills

The role of mould fluxes in continuous casting is reviewed. The main functions of the flux are described and the importance of the flux in providing lubrication and the right level of heat transfer between the shell and the mould is described. The major problems of longitudinal, transverse and star cracking, gas and slag entrapment and deep oscillation marks in the steel product and ?sticker breakouts? are analysed. The important physical properties of the flux in combating these various problems are identified. Physical property data for the fluxes are given.

Jan 1, 2004

By C. Birch

"A ‘geologically constrained’ orebody model has long been hailed as vital for a Mineral Resource statement that is compliant with the South African Code for Reporting of Exploration Results, Mineral Resources and Mineral Reserves (SAMREC Code). In this paper, the requirements for geological modelling as contained in the outline for the SAMREC Code are considered, and whether the new modelling software available on the market is a ‘black box’ or is better for modelling than traditional methods of wireframe creation.Implicit geological modelling is a technique that uses a radial basis function to establish and update geological models relatively quickly and efficiently from borehole data, outcrop data, manually interpreted vertical or horizontal sections, and structural data. Assays and any coded drill-hole data, such as lithology and alteration, can be interpolated.Leapfrog Geo software is an example of this new approach to geological modelling. A case study of a short training course in geological modelling for non-geologists at the University of Witwatersrand, as part of the Higher Certificate in Mineral Resource Management, is presented. The benefits of this type of geological modelling software are considered for this type of assignment as well as for mining industry applications.The use of geological models in mine planning is reviewed and a case study is presented comparing the variations in mine plan design and financial output of 13 final-year Mine Design projects from the University of the Witwatersrand School of Mining Engineering. These designs were all based on the same geological model created in the traditional way, and yet the resultant mine designs were significantly different, with very different resulting financial outlooks for the project. This raises questions as to how significant a very detailed model in the pre-feasibility and feasibility phases of projects really is, considering the huge costs involved in gathering the required data to build a SAMREC-compliant geological model."

Jan 1, 2014

By R. D. Hull

Paper written on project work carried out in partial fulfilment of B.Sc. (Eng.) (Mining) degree As a partial fulfilment for the degree of B.Sc. (Eng) (mining) at the University of the Witwatersrand, a dissertation was to be completed in the mining industry. This was done at Finsch mine, with the purpose of determining the best solution to the required secondary breaking problem. In order to complete the study of the secondary blasting method available for use in the new block 4, cave mining method at Finsch mine the following problem statement was identified and solved ?The methods currently in use, for the secondary breaking of oversize rocks at their source in the current production levels, are to be investigated, and their applicability to the new block 4mining project determined?. To effectively achieve this problem statement above; time was spent researching and investigating, in depth, the methods that are currently in use at both Finsch and Koffiefontein mines; so as to gain practical knowledge of these. The methods were identified and independently evaluated, taking into consideration factors such as costs of the equipment, time to break oversize rocks, advantages, disadvantages, safety and labour requirements, etc. This in turn then allowed for a direct comparison between the methods and the decision as to the best to apply to the new block 4 production level. The methods that were investigated included: ?Concussion blasting, where concussion bombs and lay-on charges are used to break hang-ups and boulders. ?Drill and blast methods, where holes are drilled in large rocks and charged manually with explosives. ?Emulsion secondary blasting, which is a new project in use at Koffiefontein mine from African Explosives Limited. ?The Ro-BustTM breaking system, a hydro-fracturing breaking system. Once all the methods had been evaluated and compared it was found that the Ro-BustTM Breaking system was the most applicable for the breaking of boulders, with, the Emulsion Blasting System being used for hang-ups. Further information and the more in-depth version of this report, is stored in the resource centre at De Beers?Finsch Mineand the School of Mining Engineering WITS University.`

Jan 1, 2002

If you have problems or questions relating to the installation of this disc, please either telephone Document Transformation Technologies at (+27 12) 667 2074, or e-mail: nigel@doctech.co.za Si vous avez des problèmes relatifs àl?installation de ce disque, veuillez appeler Document Transformation Technologies au (+27 12) 667 2074, ou nous écrire par courrier électronique: nigel@doctech.co.za Produced by: / Produitpar:Document Transformation TechnologiesP O Box 560 ?Irene ?0062 ?South Africa.Tel: (012) 667 2074; Fax: (012) 667 2766; International Code (+27 12) e-mail: doctech@doctech.com website: http://www.doctech.co.za

Jan 1, 2004

By A. Varadarajan, M. Hashemi, K. G. Sharma

Quartz mica schist collected from Nathpa-Jhakri Hydropower Project, Himachal Pradesh, North India is tested under triaxial loading using a servo-controlled loading system. Complete stress-strain-volume change behaviour including post peak softening behaviour of the samples, are presented. Strength and deformation parameters are given. Quarz mica schist, der von Nathpa Jhakri Hydropower Projekt, Himachal Pradesh gesammelt wird, wird Nördlich Indien unter triaxial geprüft, der von Gebrauch eines servo kontrollierten Ladesystems beladung. Vollständiges Spannung-Spannung-Band Änderung Verhalten Postens Spitze Erweichung Verhaltens der Proben, wird überreicht. Kraft und Verformung Parameter werden gegeben. Mica à quartz schist recueilli du Projet de Hydropower de Nathpa Jhakri, Himachal Pradesh, l'Inde du nord est essayé sous l'utilisation de chargement de triaxial un système chargeant servo réglé. La tension complète-la tension-comportement de changement de volume y compris la poste sommet amollir le comportement des échantillons, sont présenté. Les paramètres de force et déformation sont donnés.

Jan 1, 2003

By R. J. Fruehan

Slags have many useful functions in iron and steel making. In particular, slags are used to remove impurities such as sulphur, phosphorus and inclusions from the metal, and a large amount of research has been done in this area. Slags also insulate the metal thermally and form reactions with the atmosphere such as reoxidation and nitrogen pick-up. However, slags serve other more unique functions, several of which are reviewed in this paper. The role of slags in new iron smelting processes with regards to reduction of ore and gaseous desulphurization are discussed. In iron smelting processes, much of the reduction occurs by the reaction of carbon in the char and the metal suspended in the slag with iron oxide dissolved in slags. The slags also react with the gas resulting in sulphur removal from the process. The mechanisms of these reactions and pilot plant data for these processes are given in this paper. Slag formation within ferrous burden materials affects the cohesive zone and the performance of the blast furnace. Recent theoretical and experimental findings on this topic are presented. In the electric arc furnace, foamed slags are used to allow for higher power operation and productivity. Of particular interest, foaming in stainless steel production is more difficult than for normal steels. The foam index, or the ability of the slag to foam, for stainless steelmaking is similar to that for carbon steelmaking slags. The poor foaming is due to the lack of gas generation for the foam. Methods to increase foaming in stainless steelmaking are discussed.

Jan 1, 2004

By P. Fredriksson, S. Seetharaman

In the ladle refining process, the ?FeO?-content of the ladle slag is of great importance in the chemistry as well as the energetics of the process. An optimization of the process requires an accurate knowledge of the thermodynamic activities of ?FeO? in the ladle slags. Due to the discrepancies in the existing data, renewed attempts are being made at the Royal Institute of Technology to generate reliable data for binary, ternary and multi component slags containing ?FeO? at steelmaking temperatures. In order to measure the activities of ?FeO? in the slags, a gas equilibration technique was employed in the present work. The slags, kept in Pt-crucibles, were equilibrated with a CO-CO2-Ar gas mixture and quenched after equilibration. The chemical composition of the slag was analyszed. From a knowledge of the thermodynamics of Fe-Pt system, the ?FeO? activities in the slag could be evaluated. The results of the present studies, together with other literature values, were optimized in the slag software, THERMOSLAG® developed in the Royal Institute of Technology, Sweden. The results of the optimization are presented. Model calculations were performed with the KTH slag software, THERMOSLAG®, by using plant data from OVAKO Steel, Hofors, Sweden. It was found that oxygen estimations in the metal from the ?FeO? analyses of slags, obtained by conventional sampling and analysis methods, where less reliable. Estimation of the oxygen levels utilizing the sulphur partition between the slag and the metal were carried out using the THERMOSLAG® software. Reasonable estimations of the oxygen contents in the metal confirmed that this could be a very useful tool for the plant operator. Keywords: ladle, thermodynamics, slags, ?FeO?, experimentation, modelling, sulphur partition

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

Publications on hard rock tunnel support design in the South African mining industry have originated primarily from the goldmines during the past 50 years. Little has been published to date on the platinum and chrome mines of the Bushveld Complex. This paper covers the search for a suitable design methodology for off-reef tunnels at Impala Platinum Mine, situated on the Western Lobe of the Bushveld Complex. The fall of ground accident statistics for off-reef excavations of the mine are presented and the available rock mass quality evaluation systems are reviewed. The Q-Tunnelling Quality Index (or Q-Index) is selected because it assesses the important driving factors behind falls of ground at Impala. Two off-reef excavations are evaluated using the Q-Index, and it is shown that minor modifications are required for implementation at Impala. It will take some time before support design throughout the mine is based on the outcome of proper geotechnical investigations based on the Q-Index. Widespread implementation of such support designs should help to solve the fall of ground problem in off-reef excavations while at the same time reducing support costs.

Jan 1, 2002