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By W. V. Mutler

Present day capital costs are analysed for a 2 000 metric tonne per day (MTPD) pyrite burning plant and compared with a sulphur burning plant of the same capacity. Power, raw material and steam production rates are then compared for the two facility types. A sensitivity analysis is conducted to highlight the impact changing sulphur, pyrite, capital and operating costs have on the relative economics of these feeds. Technological improvement effects on capital cost and energy recovery are also discussed. Besides the steam produced from the burning of pure sulphur or pyrite, plants using an advanced form of heat recovery can produce up to 10 bar steam using heat from acid formation. The quantity depends on the overall water balance which is influenced by such factors as gas strength and product acid concentration. Modern materials and innovative process design also improve the ability to increase the high pressure steam from the roaster boiler in pyrite plants above the traditional 1.25 kg of superheated steam per kg of acid produced.

Jan 1, 2009

By M. L. Bakker

The ISASMELT? top submerged lance (TSL) bath smelting process was developed in Mount Isa, Australia by Mount Isa Mines Limited (now a subsidiary of Xstrata plc) during the 1980s. By the end of 2011, the total installed capacity of the ISASMELT? technology will exceed 8 000 000 metric tons per year of feed materials in copper and lead smelters around the world. Commercial plants, operating in Belgium and Germany, are also batch converting copper materials in ISASMELT? furnaces. This TSL technology is equally effective for continuous converting processes, in which role it is called ISACONVERT?. This paper presents the recently patented ISACONVERT? process for the continuous converting of nickel and platinum group metal (PGM) containing mattes using the calcium ferrite slag system. The paper focuses on the potential application of the ISACONVERT? technology to existing nickel and PGM smelting complexes.

Jan 1, 2011

By I. Mihajlovic

This paper investigates a potential method for arsenic removal from copper concentrates using hypochlorite leaching. The problems concerning pyrometallurgical processing of copper concentrates with high arsenic contents are discussed. A possible solution to the problem by leaching of natural enargite crystals with sodium hypochlorite under alkaline oxidizing conditions, with enargite converted into crystalline CuO and the soluble arsenic forming AsO43-, was experimentally investigated and results are presented. Kinetic parameters were calculated for enargite leaching, using a model-free approach. Advanced isoconversional methods were used to investigate the dependence of activation energy (Ea) on reaction rate (a). Keywords Enargite, copper concentrate, isoconversional method, kinetics, activation energy.

Jan 1, 2011

By B. O. Odera

The Pt-based alloys have a high potential for replacing some Ni-based superalloys (NBSAs) used in the highest temperature and most aggressive environments, and vanadium would be a beneficial alloying element. Six alloys of average compositions Pt-26.6Al-9.1V, Pt-23.1Al-17.8V,Pt-9.6Al-21.1V, Pt-17.4Al-6.4V, Pt-22.3Al-7.9V, and Pt-6.0Al-10.1V (all in at.%) were manufactured by arc-melting and examined in the as-cast condition using scanning electron microscopy and X-ray diffraction (XRD). Five samples were heat treated at 1 000°C for 1 500 hours and water quenched, then examined. The phases were identified using energy-dispersive X-ray spectroscopy and the identities were confirmed by XRD. In most of the samples, the phases existing in the as-cast condition were different from those at 1 000°C after ~1500 hours heat treatment. A solidification projection, an isothermal section and a liquidus surface projection were determined for the Pt-rich corner.

Jan 1, 2012

The compilation of the sampling nomogram is an essential tool in the optimization of a sampling protocol and allows the operator to track the change in relative variance of the sampling error (the Fundamental sampling error) during steps of comminution and mass reduction in the process of recovery of the aliquot for analysis. The data required for the compilation of the nomogram are centred on the sampling constant K and the exponent, alpha (a) of the nominal fragment size. Five methods for establishing K have been identified, but two of them, the duplicate sampling analysis method and the heterogeneity test method purport to provide such constant. The step by step procedure for each of these two methods was examined using broken ores from three mines, Mponeng mine, Kloof mine, and Lily mine. Two of these mines (Mponeng and Kloof) are typical Witwatersrand-type gold mines, and the third is an Archaean-type shear related gold deposit situated in the Barberton Greenstone belt. The results suggest that the factor K derived using the heterogeneity test is very accurate, but applies only to a single size fraction in the spectrum of comminuted materials. The calculation of gold grain sizes using this method appear to be too small and do not conform with the results from detailed mineralogical studies. The factors K and alpha derived using the duplicate series analysis are appropriate for use across a wide spectrum of comminution sizes and also provide realistic gold grain sizes, comparable with the equivalent circular diameter of gold grains identified in mineralogical studies of the ores.

Jan 1, 2010

By Chris D. Winkler

Vanadium-based sulphuric acid catalyst has been utilized to oxidize SO2 to SO3 since the early 1900?s. This versatile product displaced the expensive and easily-poisoned platinum-based catalyst in nearly all applications by the 1930?s. MECS has been manufacturing the vanadium-based catalyst since 1925 and today is the leading supplier in the world of sulphuric acid catalysts in a variety of forms. Currently, MECS has world-wide customer/technical support for the catalyst as well as a dedicated catalyst manufacturing plant in Martinez, California. MECS also has a strong technical and research and development program dedicated to creating new and improved products and services. This paper will describe some of the technical details of vanadium-based sulphuric acid catalysts as well as offering a unique look into how caesium-promoted MECS catalysts can be used in single and double absorption acid plants, and off-gas plants running on irregular gas feeds, to reduce emissions and pre-heater run times. An update on MECS technical services extended for use in characterizing converter performance is also presented.

Jan 1, 2009

By Chris D. Winkler

Vanadium-based sulphuric acid catalyst has been utilized to oxidize SO2 to SO3 since the early 1900?s. This versatile product displaced the expensive and easily-poisoned platinum-based catalyst in nearly all applications by the 1930?s. MECS has been manufacturing the vanadium-based catalyst since 1925 and today is the leading supplier in the world of sulphuric acid catalysts in a variety of forms. Currently, MECS has world-wide customer/technical support for the catalyst as well as a dedicated catalyst manufacturing plant in Martinez, California. MECS also has a strong technical and research and development program dedicated to creating new and improved products and services. This paper will describe some of the technical details of vanadium-based sulphuric acid catalysts as well as offering a unique look into how caesium-promoted MECS catalysts can be used in single and double absorption acid plants, and off-gas plants running on irregular gas feeds, to reduce emissions and pre-heater run times. An update on MECS technical services extended for use in characterizing converter performance is also presented.

Jan 1, 2009

By P. Kluge

Mining engineers frequently encounter complex design problems for which the critical components of the design are difficult to quantify or compare. Teams of people typically work on these designs and human perceptions and judgments play a strong role. To assist with this process, the analytical hierarchical process (AHP) as a decisionmaking tool is described in this paper. Although the technique is used in many other disciplines, it is currently not widely used in mining engineering in South Africa. To use the AHP process, the problem should be treated as a hierarchy that defines the goal, the alternatives to reach it, and the criteria for evaluation of these alternatives. Pair wise comparisons are conducted on the criteria of the hierarchy to establish priorities. The value of the technique is that it is simple to test for consistency amongst the pair wise comparisons to ensure that the answer obtained is better than that provided by a random selection. To illustrate the technique, the use of a backfill support system in a platinum mining project was investigated. Ten design parameters, which will be impacted by the use of backfill, were identified and weighted according to their relative importance. The result of the AHP evaluation was that the use of a backfill support system should be preferred to a conventional support system at the mine.

Jan 1, 2011

With the passing of Dr William Bleloch on 20th June 1991, we lost not only a colleague and a good friend but a man who made a very significant contribution to the industrial development of South Africa. He can rightly be called the father of the ekctrochemical and electro-metallurgical industries in this country, since his ideas and dedicated work were directly responsible for the development of these large industries as we know them today.

Jan 1, 1991

By L. Holappa

Ferroalloy production is an energy-intensive industrial sector with significant CO2 emissions. In this paper the current situation in ferroalloy processes is discussed from the standpoint of global environmental issues, trends and development. Progress and data of ferroalloys production are frequently compared with the steel industry, which is a closely related sector and the main user of ferroalloys. Emission factors of processes and electricity production are examined as well as possibilities and future scenarios of how to diminish CO2 emissions. As a part of this study a questionnaire was submitted to experts in the field of ferroalloys worldwide to survey opinions on the ferroalloy industry today and in the near future (2020). Eighteen questions concerning raw materials, energy, environmental aspects, by-products and economic aspects were responded to by seventeen experts, the answers were analysed and conclusions were drawn. Keywords Ferroalloys, energy, CO2 emissions, electricity, sustainability, questionnaire.

Jan 1, 2010

By R. T. Jones

DC arc furnaces are widely used for steel scrap melting as well as for reductive smelting of ore fines. Industrial smelting applications include the smelting of chromite to produce ferrochromium, the smelting of ilmenite to produce titania slag and pig iron, and the recovery of cobalt from nonferrous smelter slags. A number of myths and misconceptions are widely held, especially regarding: the age of the technology, the use of a hollow electrode, arc stability and shape, arc and bath radiation, interaction between the arc and molten slag, electrical behaviour of arcs and slags, a comparison between AC and DC furnaces, DC reactors, the lifespan of bottom electrodes, and the applicability of DC arc furnaces to various metallurgical systems.

Jan 1, 2011

By R. W. Ottermann, N. D. L. Burger, A. J. von Wielligh, P. R. de Wet, J. L. Steyn

A low noise blast hole drilling system was developed to limit the risk of noise induced hearing impairment in mining operations. Noise induced hearing loss has been identified as a major occupational health risk in SA mines. The noise generated by pneumatic percussion drills is a major contributor to such noise induced hearing. This motivated the South African Safety in Mines Research Advisory Committee (SIMRAC) to commission the development of a low noise rock drill system. The system had to be designed, manufactured, tested and demonstrated in a simulated underground mining environment. The specification required noise levels below 90 dBA. Other important design considerations were ease of manual transport, setting up and operation. The primary design concept was to encapsulate a standard Seco S215 pneumatic rock drill in a composite material tube. The tube is pushed onto the rock face by a pneumatic cylinder and is sealed at the rock face by an elastic seal. The drill is pulled towards the rock face by a rope and pulley mechanism fitted inside the tube. This mechanism is powered by a second pneumatic cylinder. The actions of moving and setting the drill require two persons. However, the team can carry out the drilling function itself on several drills simultaneously because of the self-thrusting design. The drill is supported by two camlocks. The exhaust (air containing dust, water, rock shavings, oil and grease) is removed from the encapsulating tubes via exhaust tube to the end of the stope. In this way exhaust noise and air pollutants are disposed of away from personnel. Tests were conducted in a test stope. Noise levels of under 90 dBA were achieved, thereby attaining the primary design specification. This was achieved without materially compromising ease of handling. Penetration rate was somewhat improved compared to that of the standard drill, so that productivity could be maintained. Keywords: Drill, rock drill, quiet, noise, mine, underground.

Jan 1, 2003

A typical sub-level block cave mining extraction method employs an undercut level to establish a cavity in hard rock, and as such requires special support methods and products to be installed during the development phase. The undercut level development in the block cave orebody is then sacrificial, and support elements will eventually report to the crusher and perhaps conveyor belt systems for transportation to surface. The choice of support products installed in the undercut level development should take cognizance of the detrimental effect these could have on the mining system such as cutting of conveyor belts, obstructing crushers, safety aspects, and productivity. This work explores the probability and practicality of making use of new-generation support products to make the operation safer as well as enhance productivity in the development phase and during the undercut operation. This paper will investigate the use of glass reinforced plastic(GRP) rockbolts and GRP mesh instead of conventional steel bolts and mesh along with resin capsule-filled holes with the GRP bolts. Complementing this with thin spray liner (TSL) application as another means of creating a safer operating environment, as well as a productive support medium, will also be addressed. These proposed items are envisaged to reduce production downtime and improve the safety of our people. These items are all easy and light to handle, cuttable and crusher friendly, as they will break up during the crushing process.

Jan 1, 2012

By D. A. Spencer, L. J. Gardner

In light of the apparent productivity benefits provided by mechanised stoping, Impala Platinum Limited commissioned a study to investigate its possible implementation for mining reserves located 1200 – 1700 m below surface. This paper records the methodology employed for designing a support system for such mechanised mining, as well as initial conclusions of the work done. Preliminary results show the concept to be technically feasible; work was however stopped due to financial non-viability. En considération des bénéfices de production apparents que donne l’exploitation par gradins mécanisée, Impala Platinum Limited a commissionné une étude visant à examiner sa mise en œuvre possible pour des réserves minières situées à 1200 – 1700 m sous la surface. L’étude présente rapporte la méthodologie employée pour créer un système de support pour ce genre d’exploitation mécanisée, ainsi que les conclusions initiales de ce projet. Les résultats préliminaires montrent que le concept est techniquement faisable ; cependant le travail fut arrêté à cause de difficultés de rentabilité. Im Licht des offensichtlichen Produktivitätsnutzens auf Grund mechanisierten Stossbaus, kommissionierte Impala Platinum Limited eine Studie, die dessen mögliche Implementierung für den Abbau von Reserven 1200 - 1700 m unterhalb der Oberfläche untersuchen soll. Dieses Elaborat dokumentiert sowohl die Methode die für das Design eines Unterstützungssystems für eine derartige mechanisierte Abbauweise angewendet wird als auch die anfänglichen Konklusionen der geleisteten Arbeit. Anfängliche Resultate zeigen daß das Konzept technisch durchführbar ist; die Arbeit wurde jedoch wegen der finanziellen Nichtrealisierarkeit gestoppt.

Jan 1, 2003

By John V. Simmons, Peter J. Simpson

Excavated slopes in open pit coal mines are designed to be as steep as possible consistent with stability and safety requirements. Slope failures occur for many reasons, including oversteepening. This paper is concerned with slope design and excavation experience in the Bowen Basin coalfields of central Queensland (Figure 1), [ ]

Jan 1, 2006

By C. J. Badenhorst

The scope of this project was to research, develop and eventually produce a personal occupational hygiene and safety exposure monitor system to assist in recording and analysing various stress factors that could affect the health, wellness and safety of employees, i.e. that could result in injury or ill health of workers, create stress build-up within individual workers that could negatively affect worker alertness and safety, and, may even result in permanent disability or death. Utilized systems at the time were all reactive, whereas the DOHEMS (Proactive Digital Occupational Hygiene and Safety Exposure Monitoring) System enabled the measurement of exposure (and associated risk) in a proactive manner via real-time exposure and digitized recordings. The idea of the development was to create a unit that is so cost effective, small and light that every worker can use a system on a daily basis. The development will eventually replace current, bulky and expensive monitoring equipment. The device must be a portable battery operated device and monitor the immediate working environment by periodic sampling for vibration, noise, toxic gasses (NO/NOX/CO/VOC, etc.), body temperature and heart rate. The samples must be time and date stamped, utilizing a real-time clock (RTC) synchronized with the closest regional secondary time source and related to synchronized real-time video captured samples. These samples are then recorded onto a rugged non volatile storage device with the capacity to store a vast number of samples covering the entire working shift of eight (8) hours plus. The system has been fitted with a clear visual local alarm indication system, indicating any excessive exposures or stresses, for the worker?s supervisor to respond to. This system allows for a pro-active approach. The system is also a wireless system (to the external environment) so as to not affect the mobility of an employee and flameproof to allow for use in explosive environments. Keywords: safety, digital, exposure, monitoring, proactive.

Jan 1, 2010

By J. M. Ortiz

Grade control and short-term planning are usually based on the samples obtained from blastholes. These samples may carry a large sampling and sample preparation error. At El Tesoro copper mine in northern Chile, an advance drilling grid is used for short-term planning and grade control. These drill holes are sampled well in advance, and a short-term model that incorporates several variables and sophisticated estimation methods can be prepared for decisionmaking. An additional advantage of the advance drilling samples is that reverse circulation can be used instead of conventional down-the-hole equipment, and a very careful sampling and sample preparation process can be implemented, reducing the total sampling error. Advance drilling can be performed on a wider grid than blasthole drilling, hence the decision about the grid requires assessing the economic benefit of different sampling grids. Furthermore, this process allows the cost of poor sampling and the effect of different estimation procedures to be quantified. We demonstrate the optimization of the drilling grid for short-term planning and grade control at El Tesoro mine by means of the economic evaluation of the performance of different drilling grids, with different drilling techniques (which differ in the sampling error). The methodology is based on creating dense (exhaustive) geostatistical simulations of the grade distribution over a volume defined for a production period in respect of the geological model, and assuming each simulation as the true grade distribution. Then, samples are obtained from the exhaustive simulations at a spacing similar to the advance grid to be evaluated, and a sampling error is added. The short-term estimation procedures used on the mine are applied to determine the destination of each block and the profit obtained. This profit can be compared with the maximum profit (unachievable) and with the profit under different sampling errors and grids. The results show that the current 8 x 8 m drilling grid is appropriate and by reducing the sampling error, misclassification is also reduced, leading to an increase in profit of about US$ 5 million in 4 years.

Jan 1, 2012

By M. Tangstad, D. Lu, G. Tranell, S. Gaal, J. Safarian

The kinetics of MnO reduction from high carbon ferromanganese slag was investigated using a sessile drop technique at 1600 ºC. The effects of reductant type, ambient atmosphere and slag composition on the MnO reduction were illuminated. Two different types of industrial reductants (ground to a particle size of 44 to 106micron and pressed to pellets) were used as substrates for small slag droplets of varying composition, which were reacted in a CO or Ar atmosphere with the reaction studied in-situ. The cross sections of the reacted slag-carbon samples were subsequently studied by EPMA to find the extent of MnO reduction as a function of reaction time. It was found that the rate of MnO reduction is affected by both the type of reductant, the ambient atmosphere and the presence of metallic components in the slag. Higher reduction rates were obtained for charcoal than for coke as reductant while a CO atmosphere unexpectedly yielded faster MnO reduction than an Ar atmosphere. It was also found that metal prills in the initial slag will increase the rate ofMnO reduction.

Jan 1, 2007

By Jeffrey C. Hillman

The need to recruit locally produced engineers by the South African Mining Industry led to the Engineering Faculty at the University of the Witwatersrand developing a number of academic bridging initiatives for educationally disadvantaged students. The graduation rate achieved during the initial five years of operation by the most successful of these programmes has been on a par with that of al other students but the performance of subsequent intakes has declined to such an extent that the continuance of this scheme could now be at risk. One reason for this reduction in throughput is that many of the applicants for the increasing number of mining bursaries have been more interested in the bursary than the profession and have either failed or dropped out due to a lack of application and motivation. This will have serious consequences for both Wits and the Industry if it continues and some method of identifying unsuitable or suspect applicants needs to be introduced as a mater of urgency. It is recommended that an introductory course be set up at a working mine that would be run under the auspices of Wits, as a joint venture with industry, and include a level of academic input that would provide both bridging needs and certain first year credits. The final form of this course will require extensive consultation with al parties but needs to be completed before the end of 1996. It is further recommended that the advertising and promotion of mining careers be expanded and much improved.

Jan 1, 1996

By J. P. Josien, J. F. Noirel, F. Lahaie, P. Bigarre, M. Al Heib

ABSTRACT: In June 2001, a fatal rockburst affected a longwall face in the Houillères du Bassin de Lorraine (HBL), France. Subsequently, a large operation of in situ stress measurements by overcoring was carried out with two main objectives: providing input data for the back analysis of the dynamic event and characterising the stress field in the next panels to be mined for identifying other potential high-risk zones. This paper makes a synthesis of the results of the overcoring tests performed and discusses those results in connection with the mining context, numerical model predictions, laboratory rock test results and microseismic activity. KEY WORDS: Mine, rockburst, stress, overcoring, measurement. ZUSAMMENFASSUNG: Im Juni 2001 hat ein Bergschlag eine Kohlengrube des Houillères du Bassin de Lorraine (HBL, Lothringen, Frankreich) schwer beschädigt. Nach diesem Unfall sind Spannungsmessugen durch Überborung durchegeführt worden, mit zwei Hauptziele : 1/ Daten zu liefern für die Retro-analyse des dynamischen Gebirgsschlag und 2/ die Spannungen in den zukünftigen Ausbauen so gut wie möglich zu charakterisieren, um eventuele andere Risikozonen festzustellen. Dieser Artikel stellt eine Synthese der erzielten Ergebnisse vor. Er diskutiert diese Ergebnisse in Verbindung mit dem gesamten Kohlengruben Zusammenhang, mit den Ergebnissen von numerischen Modellierungen, mit der Labor-Charakterisierung und mit der microsismische Überwachung. SCHLÜSSEL-WÖRTER: Kohlengruben, Bergschlag, Spannung, Überborung, Messung. RESUME: En Juin 2001, un coup de terrain a gravement affecté une longue taille aux Houillères du Bassin de Lorraine (HBL) en France. A la suite de cet accident, une importante campagne de mesures de contraintes par surcarottage a été réalisée, avec deux objectifs majeurs : fournir des données d’entrée permettant la rétroanalyse du phénomène dynamique et caractériser au mieux le champ de contraintes dans les futurs panneaux exploités afin de détecter d’éventuelles autres zones à risque. Cet article présente une synthèse des résultats obtenus, et discute ces résultats en liaison avec le contexte d’exploitation, les résultats de modélisation numérique, de caractérisation en laboratoire et de surveillance microsismique. MOTS CLES: Mine, coup de terrain, contrainte, surcarottage, mesure.

Jan 1, 2003