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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 T. O. Hagan

A simulated rockburst experiment was conducted underground at a deep level gold mine. This was done by means of a large explosion detonated in solid rock close to a tunnel sidewall. The resultant shake-out damage is typical of that associated with a small seismic event in close proximity to a tunnel that is subjected to the estimated field stress, as in this case, of 50 MPa. The experiment involved: ?the design of a blast to mimic a seismic source ?seismic monitoring using a dense seismic array ?high speed video filming ?a study of rock mass conditions (fractures, joints, rock strength etc.) before and after the simulation using mapping and ground penetrating radar ?special investigations to evaluate the mechanism and the magnitude of the damage ?a study of support behaviour under excessive dynamic loading.

Jan 1, 2001

By H A. Myburgh

The beneficiation of heavy metal oxides, such as iron ore, is usually performed with heavy medium separation in cyclones, static baths and lately with Larcodems. Atomized ferrosilicon is most suitable as a heavy medium at densities above 3600 kg/m3 whereas a mixture of milled and atomized ferrosilicon is suitable at densities below 3600 kg/m3. When operating a beneficiation plant at densities higher than 3600 kg/m3 the quality of the ferrosilicon particles is an important factor that influences the control of the beneficiation process. Therefore, it is important to know how the rheology would be affected by the ferrosilicon quality as it also influences the control of the process at these elevated densities. Background The Kumba Resources Sishen Iron Ore Mine in South Africa produces 26.5 Mt iron ore per annum from its beneficiation plant. The ore body consists mainly of laminated and massive type hematite ore that is crushed down to ?90mm before being beneficiated by means of a combination of Wemco drums, Larcodem and dense medium cyclone separators. The need for higher densities When the percentage of high-density gangue2 is higher than normal in the run-of-mine (ROM), a higher separation density is necessary to produce a product to specification. Certain ore types of this quality in the Sishen reserves require a separating density higher than 4000 kg/m3, whereas densities would normally average 3600 kg/m3 when beneficiating ores of normal high-density gangue content. Sink and float tests conducted on the ROM material at Sishen revealed some interesting characteristics. In the waste fraction, (density < 3600 kg/m3) it was found that the %Fe was <21% (Fig. 1). Similarly, for the product fraction (density >3000 kg/m3), the percentage Fe varied between 35% and 67.2%. The bulk of the material (88%) actually had a density greater than 4000 kg/m3 and a Fe content that varied between 63% and 67.2%. At a density interval of 3600 to 4000 kg/m3, the Fe content varied from 37% to 60% with an average of 45%.

Jan 1, 2006

By D. Hoffmann, S. Plumb

IRUP is an iron-rich ultramafic pegmatite rock that formed due to hot ironrich fluids and gases replacing local stratigraphic zones of the Bushveld Complex. This study focuses on the estimation of the probability of IRUP occurrence on the Merensky Reef at the Marikana Karee Mine. A 2.15 million centare IRUP-rich domain at the Karee Mine was initially defined from the interpretation of a surface aeromagnetic anomaly, and exposures in the mine workings. Surface boreholes (spaced 250-500 m apart) within this IRUP domain contain approximately equal numbers of IRUP-replaced and IRUP-free intersections. Owing to the uncertainty in the continuity of the IRUP alteration (a result of the wide borehole spacing), the risk associated with the development of mining infrastructure within this domain is unquantifiable. Semi-quantitative data comprising visual estimates of IRUP replacement from reef development mapping data and surface borehole reef intersections was interpolated into blocks using indicator kriging estimation. Comparative analyses of the estimate of IRUP occurrences were made by changing the block size and declustering the data systematically. Reconciliations of the probability of IRUP predicted from the block models derived from the different data-sets and sequential indicator simulation models were analysed for four mining study blocks. A quantitative approach to modelling the occurrence of IRUP can be an additional tool for refining the estimate of the geological losses that inform the mine plan in such high-risk zones.

Jan 1, 2015

By E. R. Davis, R. J. Knott

The paper discusses some of the tools of management in the field of project control, especially in engineering. Project control includes planning and cost engineering, and involves various phases: the conceptual Design and Planning Phase, the Definitive Design and Capital Budgeting Phase, and the Implementation Phase. Each of these phases is discussed in in, together with the use that can be made of data banks, progress reports, and computer systems.

Jan 1, 1982

By P. J. N. Pells

A good thing is becoming a bad thing. Rock mass classification systems, that are so excellent for communications between engineers and geologists, and that can be valuable in categorizing project experience, are emasculating engineering geology and rock mechanics. Some engineering geologists have been sucked into thinking that Q and RMR values are all that is needed for engineering purposes, and seem to have put aside what can be learned from structural geology and geomorphology. Many rock mechanics engineers seem to have forgotten the scientific method. This paper attempts to redress the situation by showing how mechanics can be used in rock engineering to design with a similar rigour to that used in the fields of structural engineering, hydraulics and soil mechanics. It also attempts to remind practitioners of what can be achieved by skilled engineering geology.

Jan 1, 2008

By D. Grabowski, Z. Pokryszka

ABSTRACT: Some residential areas of the iron basin of Lorraine (in the North-East of France) are affected by noxious gas emissions (under oxygenated, carbon dioxide loaded and radon loaded gas mixtures). Site investigations showed that the gas flow was mainly due to natural thermal air circulation between old mines and the external atmosphere. The main hazards associated with this flow of gas and its potential accumulation in confined volumes within buildings are asphyxiation and intoxication. A further study is in progress in order to better understand the origin of the gas generation within the old iron mine workings. Following the first hypothesis, the carbon dioxide emission is mainly due to the specific hydro-geo-chemical process associating the pyrite oxidation with the acid dissolution of carbonates. KEY-WORDS : gas, emission, mine, flow, pyrite. ZUSAMMENFASSUNG: Einige Wohngebiete der Eisenmulde Lothringen (im Nordöst Frankreich) werden von Ausgasung gesundsheitsschädlichen sauerstoffarmen Mischungen, die mit Kohlendioxid und Radon beladen sind, betroffen. Untersuchungen am Ort haben gezeigt, wie diese Gasstroemung von natürlichem thermischen Luftumlauf zwischen den alten Bergwerken und der externen Atmosphäre ausgelöst wird. Erstickung und Vergiftung sind die wichtigste Risiken, die mit dieser Gasströmung und ihrer möglichen Speicherung in begrenzten Lokalen zusammenhängen. Eine weitere Untersuchung wird durchgefuehrt so dass man die Herkunft der Gaserzeugung in den alten Grubenräume besser versteht. Der ersten Hypothese folgend, Ausgasung von Kohlensäure liegt vor allem an dem hydro-geo-chemischen Prozess, der Pyritrösten mit der säuren Auflösung von Karbonate verbindet SCHLÜSSELWÖRTER: Gas, Ausgasung, Bergwerk, Strömung, Pyrit RESUME: Certaines agglomérations du bassin ferrifère lorrain (au Nord-Est de la France) sont affectées par des émanations de mélanges gazeux sous-oxygénés et chargés en certains gaz nocifs (dioxyde de carbone, radon…). Les investigations effectuées in situ ont montré que les écoulements gazeux à l’origine de ces émanations sont liées au phénomène de tirage naturel entre les anciens travaux miniers et la surface. Les principaux risques engendrés par ces émanations de gaz et son accumulation possible dans des endroits confinés sont l’asphyxie et l’intoxication. Une étude est en cours afin d’expliquer l’origine de la modification de l’air au sein des vieux travaux miniers. Les émissions de dioxyde de carbone seraient dues à des processus hydro-geo-chimiques associant l’oxydation de la pyrite et la dissolution de carbonates. MOTS CLES: gaz, émanation, mine, écoulement, pyrite.

Jan 1, 2003

By N. Andersen

During the preliminary design phases and feasibility study of a proposed vertical shaft, a vertical diamond drill-hole is normally drilled on the site. This paper outlines how rock mass characteristics, in-situ rock stress, rock strength, hydrological characteristics, and structural parameters can be determined using wireline logging of this borehole. In addition, a rock mass classification scheme is developed, based on published work, and in particular the Q-factor is adapted to assess the stability of raise-bored shafts. The ‘stick plot’ is introduced, which combines all geotechnical parameters applicable to the stability of a vertical shaft into a colourcoded format where cross-correlations can readily be made on a day-today basis during the shaft-sinking process.

Jan 1, 2015

The French research institute, INERIS, requested the assistance of the CSIR?s Division of Mining Technology in developing further precautionary measures against explosions in their collieries. In response to this approach, an on-board active suppression system was adapted to meet their mining requirements. This system is used on tunnelling machines in Germany where the machine is positioned in the middle of the tunnel, which is therefore not much wider than the machine itself. With this configuration, the machine is never away from the tunnel face during the cutting cycle. As a result, the possible volume in front of the machine of combustible gas requiring suppression is less than 50 m3. In South Africa this technology has been adapted to suit a two-cut mining method which entails greater distances from the face and thus much larger volumes of methane mixtures requiring suppression. The particular configuration of the Explo-Stop® system being investigated required the suppression of possible methane ignition volumes of up to 180 m3of a 9% per volume methane/air mixture. The volume is a consequence of the large cross-sectional area of French underground workings and of the two-cut mining method used in France. In order to take the second cut in the coal seam, the machine is pulled back a maximum distance of 4 m, leaving an air pocket in which gas can accumulate. The machine-mounted system is required to effectively suppress any flame ignited by such a large accumulated volume of methane. The results of the protocol tests done at Kloppersbos showed that the system was capable of suppressing all simulated methane ignitions for the prescribed conditions. This was achieved with a temperature increase of less than a 100°C at the operator?s position and without any flame being detected at this position.

Jan 1, 2001

A201 aluminium alloy is a high strength casting alloy with a nominal composition of Al-4.6Cu-0.3Mg-0.6Ag. It is strengthened by the O(Al2Cu) phase and the ??(Al2Cu) phase during heat treatment. Further strengthening of this alloy system can be obtained through the addition of transition elements, but care must be taken as other elements might have adverse effects on the mechanical properties. The objective of this study is to determine the influence of Mn on the tensile properties of rheo-processed Al-Cu-Mg-Ag alloy A201. ThermoCalc software was used to predict the different phases that can be expected in the alloys, and scanning electron microscopy(SEM) with energy dispersive spectroscopy (EDS) was used to investigate the actual phases that formed. The influence of these phases on tensile properties is quantified. SEM and ThermoCalc revealed that there is an increased amount of the Al20Cu2Mn3 with increasing Mn. The tensile properties showed that high amounts of Mn do have adverse effects on the tensile properties of alloy A201, especially the ductility. Keywords Semi-solid metal (SSM) forming, alloy A201, intermetallics, Al20Cu2Mn3

Jan 1, 2011

By T. Mwanza, B. N. Belford, P. Conradie

"Metix has introduced a three-piece ’deep-cooled’ copper slag tapblock into a six in-line copper matte settling electric furnace. The tapblock was designed without any internal refractory; it relies purely on the development and maintenance of a freeze lining on its hot face and within the tapping channel to protect the copper and promote the integrity of the surrounding endwall refractory lining. In addition, the geometry of the tapblock further supports the sidewall refractories, reduces the impact of funnelling and, therefore, the need for premature rebuilding of the furnace endwall, and facilitates easy removal and replacement of the wear components even under ’hot’ furnace conditions. Eighteen thermocouples embedded in the copper components ensure full resolution of the copper condition, enabling plant personnel to identify wear rates, estimate freeze lining thickness and stability, and schedule replacement of spares and wear components well in advance.At the time of writing the tapblock had been in operation for 6 months with approximately 350 000 t of slag having been tapped through it. Every indication is that the design will limit the need for premature relining of the furnace endwall due to rapid deterioration of the tapblock and its surrounding refractories. IntroductionNonferrous furnaces rely heavily on the maximization of refractory campaign life to increase profitability and reduce planned downtime. In large electric copper slag-cleaning furnaces utilizing insulating linings, campaign lives of six or more years are realistic if consideration is given to each aspect that can degrade the refractory lining during the campaign. An area that is particularly vulnerable is the slag tap-hole and the local surrounding refractory. To avoid premature relining of the furnace walls, every effort should be made to consider not only the tap-hole design itself, but also the selection of the sidewall refractory material and its construction immediately adjacent to the tap-hole, and furthermore the interplay between the tapblock and this adjacent refractory. A holistic approach to the design that considers these interdependent features in the slag tapping area can reduce the incidence of accelerated refractory wear (‘funnelling’), support the surrounding refractories to prevent their collapse, introduce easily replaceable wear components that can be exchanged with the furnace still ‘hot’, and encourage and maintain a stable freeze lining at the refractory hot face that maximizes the tapblock and refractory lifetime."

Jun 1, 2019

By C. Lemmer

The resolution with which the different categories of resources are forecast for Witwatersrand gold reefs should ideally tie in with block sizes that are optimal in terms of the variability structures of the reefs. A tool, called the ?variancegram?, is proposed as a basis for block size choice. A variancegram is intrinsic to the particular reef and mine concerned. A further requirement is the ability to attach global confidence limits to weighted average estimates built up from combinations of local kriged estimates. Approximations to derive global kriging variances based on variables derived from local kriging deliver hugely inflated results if ordinary kriging is used, and markedly better, but not accurate, values if simple kriging is used. These approximations improve as the number of samples used in kriging each block is increased. It is shown that the behaviour of the different components of the global kriging variance with increasing number of samples, all differs, but they all link to the variancegram for the particular reef. The variancegram can thus be used to correct the different components to the values they would have had if all samples were used in kriging each block, and so deliver the ?correct? global kriging variance, even though only a limited number of samples were used in kriging each block. The desirability of having very stable solutions implemented in production systems is taken into account in the proposals. It is anticipated that the same variancegram findings will also hold for other densely sampled deposits, but this remains to be investigated.

Jan 1, 2014

By B. P. Watson

Crush pillars have been incorporated into a mechanized, low-profile trackless system at South Deep Gold Mine. These pillars had to be designed to fail near the face and to ensure that pillar failure is contained within the pillar, to avoid bursting and the risk of high loads being generated during a seismic event, respectively. PoweRite backfill bags were recommended to maintain the integrity of the pillars; except in the main access drives, where the sidewalls were to be supported on 5.6 mm diameter weldmesh and yielding anchors. The results of a trial site investigation exceeded expectations, showing a residual pillar strength of about 37 MPa for a newly formed pillar and 8 MPa for a pillar subjected to seismicity and a closure of more than 300 mm. The introduction of these pillars has improved the rock mass conditions because of the active nature of the support, compared to the previous passive backfill method. Importantly, the pillars have increased mining efficiencies and improved face availability. A potential cost saving to the mine of R140.9 million could be realized over a period of 10 years.

Jan 1, 2014

By P. R. Segopolo

"The purpose of the project is to convert current shuttle car utilization on an underground coal mine to best practice by focusing on change-out points and tramming routes, which have a major influence on shuttle car away times. Time studies were an integral part of the project as these enabled the determination of shuttle car away times. An indirect proportional relationship between shuttle car away times and productivity is established. Through the time studies, it is deduced that a third shuttle car will make an insignificant contribution to production when there is only one split open. During this time, maintenance on the third car can be optimized. In order to satisfy the mine’s key performance indicator of keeping shuttle car away times less than 75 seconds, a belt extension must be scheduled after the third split is open. It is established that at any given time, a minimum of two shuttle cars should be used. When cutting on the left-hand-side of the belt road with only two shuttle cars available, the centre and left (left of the feeder breaker) shuttle cars should be used for coal hauling. When cutting on the right-hand-side, the centre and the right-hand-side cars should be used. If only one shuttle car is available, the centre car is the most efficient to use. Alternative anchoring configurations can be employed so as to enable cars (left or right, especially) to reach the opposite extremities of the panel and hence minimize cable length restrictions. Paper written on project work carried out in partial fulfilment of BSc. Eng. (MiningEngineering)"

Jan 1, 2015

By R. E. Robinson

I shall present a concept for the development of the resources of this country and its neighbours that repre¬sents a fantastic challenge to our scientists and entre¬preneurs. This concept offers prospects of development that must make our previous achievements seem equivalent only to the first act in a drama enacted on the stage of Southern Africa. I hope to illustrate how, in Act Two, chemistry will play a dominant role, and chemists and chemical engineers will be among the principal actors.

Jan 1, 1980

Rock engineering has now been practised as a discipline for about50 years, and many sophisticated methods of analysis for use in rock engineering design have been developed. However, analysis is only a tool for use in engineering design, and rock masses are often so complex that realistic modelling of them, even with sophisticated methods of analysis, is impossible. At the other end of the scale, rock mass classification methods have been developed to quantify the rock mass. These ?numbers? are now widely used for assessment of stability of underground and surface excavations in rock, for the determination of rock support requirements, and for the estimation of rock mass strength and deformation properties. In considering these areas, the two concepts?design, and prediction of behaviour?will be dealt with. The discussion will be introduced by a consideration of the characteristics of the rock mass, which will highlight the variability in its properties and hence the uncertainty in the behavioural parameters. Examples of real projects will be used to illustrate the discussion.

Jan 1, 2003

By H. Yilmaz

Tensile strength testing has been one of the most common physical property testing methods of thin spray-on liner (TSL) products worldwide. However, the variety of products tested has been insufficient for comparison purposes. Specimen preparation procedures and test parameters such as curing time and loading rate are not reported well. Comprehensive tensile strength testing on 20TSL products and one plain shotcrete brand was performed over 28days of curing period. Detailed information on the test procedures with particular attention on the important aspects during sample preparation and test execution are provided. As expected, the tensile strength increases with increasing curing period. The test results make the categorization and comparison of liner products possible.

Jan 1, 2010

By T. J. Otto, G. C. Lindeque

Productivity is improved by increasing the ratio of output to input. In an operating open-pit mine, improving the productivity of heavy mining equipment (HME) enables the unit cost of production to be reduced. To optimize HME productivity, the Kolomela open-pit iron ore mine transitioned to an enhanced short-term mine planning (STMP) process that supports the application of a manufacturing-type operating model. At the core of the enhanced STMP process is a focus on integration across the open-pit mining value chain. The interdependencies between mining activities are highlighted and emphasized, thus ensuring that mining activities are synchronized. The improvements related to HME productivity were monitored from 2019 to 2020. The utilization of mining area in the Leeuwfontein pit improved from 71% to 90%, and the blasting frequency reduced by 14% while the average blast size increased by 17%. The distance travelled during shovel relocations between mining phases reduced by 16%, and the lost time associated with drills relocating reduced by 53%. These productivity improvements resulted in an 11% increase in the loading rate of the main waste shovel at Kolomela from 0.9 Mt/month in 2019 to 1.0 Mt/month in 2020. The enhanced STMP process can be adapted to other open-pit mining operations.

Nov 1, 2021

By V. Bari?ic

The scheduled power cuts of early 2008 were a disturbing reminder that South Africa needs to expand its power-generating capacity. Low-grade and discard coals, of which South Africa has much, are a source of energy and amenable to combustion in circulating fluidized beds (CFBs). Foster Wheeler (FW) has a long record in developing this technology in boilers. The technology is flexible in burning a variety of fuels; low-grade, high-ash coals, good quality bituminous and anthracite coals, and biomass and waste fuels have all been used. CFB boilers are efficient, reliable and can be designed to meet tight emission standards. In recent years once-through supercritical (OTSC) CFB technology has been developed. It enables the next stage in CFB development to proceed to a medium-scale (500 MWe) utility in such projects as Lagisza, which runs at a net efficiency of nearly 44%. Scaling the technology up to 800 MWe with a net efficiency of>45% is planned to be commercial during 2009. CFB technology can reduce CO2 emissions in the repowering of coal-fired and greenfield power plants. It does so through greater efficiencies and by co-combusting coal with biomass. FW has also developed CFB technology for the gasification of biomass, as, for example, in a pressurized gasifier to produce syngas, which can be used for the production of biodiesel, thereby reducing CO2 emissions from vehicles. Carbon capture and storage (CCS) can potentially cut CO2 emissions in the generation of power from fossil fuels in the short term, provided that it gains public acceptance, that the required regulatory framework is created, and that emission-trading mechanisms or other incentives provide a solid return on the major investments required. Oxyfuel combustion is an option in CCS; Foster Wheeler is adapting its CFB combustion technology for oxy-fuel combustion to meet this challenge. It is developing Flexi-burn?, which enables a plant to be operated either with or without carbon capture. This paper describes the status of CFB technology in terms of boiler efficiency and fuel flexibility. It highlights the advantages of CFB technology for oxyfuel combustion, presents a development plan for Flexi-burn?, and discusses a pressurized gasifier for biodiesel applications.

Jan 1, 2009

By S. Y. Chen

A new process comprising metallizing reduction, magnetic separation, and electroheat melting separation is proposed with the aim of achieving high recoveries of iron, vanadium, and titanium from vanadium titanomagnetite. The effects of magnetic intensity, reduction temperature, reduction time, carbon ratio, and coal particle size on the efficiency of reductionmagnetic separation were investigated, the reaction mechanisms elucidated by SEM and EDS analysis, and the optimal process parameters established. Recoveries of up to 80.08% for titanium, 95.07% for iron, and 71.60% for vanadium were achieved. The reduction sequence is shown to be: Fe2O3 ? Fe3O4 ? FeO ? Fe; Fe2TiO5 ? Fe2TiO4 + TiO2 ? Fe + FeTiO3 ? Fe + FeTi2O5 ? Fe + TiO2.

Jan 1, 2014