Search Documents

By J. van Deventer

Testwork was done with two different adsorbents, Dowex-Minix gold-selective resin and activated carbon, to detemine their relative performances with regard to gold recovery from clarified low-grade solution employing a fixed-bed operation. The mill discharge from the milling-in-cyanide operation at a Witwatersrand gold mine was used as feed to the adsorption columns. A small amount of gold was leached during the milling process, so that this solution simulates, to a certain extent, a low-grade solution representative of a heap-leach operation. A speciation of the feed solution was done to establish which metal complexes were present in the milling-in-cyanide solution. This information was necessary to interpret metal loadings on the resin, as base metal cyanide species and their respective charges have an effect on the final gold loading capacity of the resin. Equilibrium isotherms were established for both adsorbents to estimate the rate of adsorbent flow anticipated for this specific feed solution. Breakthrough profiles were obtained at two different superficial linear velocities for each adsorbent. Mass transfer zone heights determined from the test work and the elution/regeneration time requirements were used to size a 150 m3/h full-scale plant for both adsorbents. A counter current configuration of adsorption columns, using three columns, should be suitable to recover gold effectively and to produce an effluent with a gold concentration below 0.01 mg/l. Based on the results obtained from the breakthrough tests, a preliminary techno-economic comparison was done between the resin-in-solution and carbon-in-solution options for the recovery of gold from low-grade solutions. This study indicated that the capital expenditure for a carbon-in-solution plant would be about 33 percent higher than that of a resin-in-solution plant. The operating expenditure for a resin-in-solution plant is expected to be only 60per cent of that for a carbon-in-solution plant. Keywords: resin-in-solution, carbon-in-solution, heap leach.

Jan 1, 2000

By H. Saroglou

Anisotropy is a characteristic of intact foliated metamorphic rocks (slates, gneisses, phyllites, schists). Testing was used to establish the anisotropic behaviour of selected gneissic rocks. The effect of anisotropy on various mechanical properties (strength, deformation) and dynamic properties (wave velocity) was examined. The rock samples were also tested at successively higher confining pressures in order to evaluate the effect of anisotropic behaviour at high overburden pressures.

Jan 1, 2004

By T. D. Mailula

Paper written on project work carried out in partial fulfilment of M.Sc.(Chemical Engineering) degree Chromite and talc are two major gangue minerals in platinum bearing UG2 ore processed from the Bushveld Complex in South Africa. During flotation, talc is effectively depressed by the addition of depressants. Chromite, on the other hand, is considered to be hydrophilic, its recovery is believed to follow water recovery and therefore recovered by entrainment only. In certain cases it has been shown that chromite can be activated by the reagent suite and hence is made amenable to true flotation. The aim of the work was to investigate the effect of the addition of copper sulphate as an activator and the effect of the depressant type and dosage on the recovery of chromite. The results of these experiments showed that copper sulphate, at higher dosages, activated the chromite. Low dosages of copper sulphate resulted in no chromite activation. This was observed at low depressant dosages of both IMP4 (guar gum) and KU5 (carboxymethyl cellulose (CMC)). When the depressant dosages were increased, at higher copper sulphate dosages, it was observed that the activated chromite was depressed by IMP4, but that the activation was still significant with the use of KU5. The activation of the chromite is attributed to the form of the copper species present in the solution and on the mineral surfaces at pH = 9 enhancing collector adsorption and thereby increasing hydrophobicity. These species were not measured directly and it is recommended that this should be further investigated using surface mineral techniques. Keywords: flotation; depressants; chromite; copper sulphate

Jan 1, 2003

By N. Ragoonanthun

Paper written on project work carried out in partial fulfilment of B.Sc. (Mining Engineering) degree This report investigates the optimization of a raiseline in order to open up the ore reserve quicker. The project was carried out at Mponeng Mine (an Anglogold shaft formerly known as Western Deep Levels 1 Shaft and South Mine, in Carletonville). The project was divided into two focus areas namely: ?To design an optimum layout of a raiseline, which includes the scheduling of all activities for the establishment of the infrastructure. Consideration was given to the blasting practice, mining cycle, orepass placement and slusher positioning. Two designs were carried out on the above basis. ?The design of a ledging operation/practice to match the optimized layout of the raiseline. The ledging cycle design involved a thorough investigation into the possible use of drill rigs, Electronic Delay Detonators (EDD) blasting technology, longer drilled holes, Threshold Blasting (THROB),and water jet cleaning.

Jan 1, 2003

By H. Moosberg-Bustnes

In cement-based products, such as concrete and mortars, a balance between the particle sizes of the components must be kept in order to obtain the required material properties, such as workability and strength. Sometimes the aggregates lack the necessary amount of fines, hence fine particles, i.e., filler materials, have to be added. Large quantities of filler material are needed in the production of modern concrete types; one principle of self-compacting concrete (SCC) is, for instance, the use of large amounts of fillers to reduce the friction between the coarser aggregates. Use of by-products such as slag, dust or sludge from the metallurgical industries as filler materials in concrete may help to conserve natural resources and at the same time be an economically positive option. However, to be able to successfully use the available materials they must be suitable for the planned purpose, i.e., they must be compatible with cement. In this paper three different experimental studies of steel-slags will be discussed. The aim of the studies has been to investigate if it is possible to improve the steel-slags properties, by selective screening, fine wet grinding or remelting, so that the steel-slags can be used as mineral-addition/filler material in concrete. Keywords: concrete, filler, steel-slag, modification

Jan 1, 2004

Outotec?s direct leaching process is an atmospheric leaching process for sulphidic zinc concentrates. The direct leaching process, based on special leaching reactors developed by Outokumpu, is the most economical way to produce electrolytic zinc. The production scale applications of the process realized so far are in use at Boliden?s Kokkola and Odda zinc plants. A new full-scale application of Outotec?s direct leaching process will be started in 2008 in China. The process is integrated to the existing production plant, replacing part of the old production facilities by modern technology. Besides high zinc extraction the plant expansion and modernization offers also indium recovery, iron precipitation and solution purification processes. The process equipment includes tailor-made reactors designed on the basis of the work and experience of Outotec research center. Keywords: zinc, concentrate, atmospheric leaching, technology, indium, iron precipitation, solution purification, Outotec

Jan 1, 2008

By P. J. Foster

A common theme running through recently introduced mining health and safety legislation in many parts of the world is risk assessment. Most recently, risk assessment legislation has been introduced across the mining industry of South Africa and the view that the introduction of risk assessment based legislation provides an ideal opportunity to improve on past health and safety performance is presented. Risk assessment techniques range from highly complex safety system techniques that are used in high technology process industries, to subjective techniques based on simple judgements that are finding use in many other industries. The objective of this paper is to shed some light on risk assessment, not by detailing the risk assessment process but by identifying the crucial elements that need to be considered if risk assessments are to be successful in changing health and safety performance. A case study is presented illustrating the introduction of risk assessment into the Ingwe Coal Corporation, one of South Africa?s largest mining houses, to indicate how the system was developed and how it is being used.

Jan 1, 1998

By E. M. Bloomfield, C. A. Jermy

Geotechnical tests were carried out within an area of the coastal sand dune cordon of northern KwaZulu-Natal which is currently being exploited through mining of heavy mineral sands. In situ and laboratory tests were carried out to assess the density, strength and stability of the dune sand material before and after mining. The most stable combination of sand (>63µm) and fines(<63µm) material was determined as well as the effects of compaction on the strength and permeability of the sand dune samples. In situ DCP and density tests showed that the sand dunes fall in density immediately after mining has taken place. However, settlement of the dunes occurs with time and the density increases within the top 2 metres, and particularly once the dunes become re-vegetated. Laboratory tests carried out showed that the dune sand with between 20% and 30% added fines had the highest shear strength and dry density, but the permeability was shown to decrease steadily with increasing fines up to 40% fines added. The addition of fines would result in steadily increasing water flow problems. Compaction of the dune sands was shown to significantly increase the density and the shear strength, but with a corresponding dramatic decrease in the permeability of the material. Slope stability analysis carried out on models of the dunes with increasing fines showed that the addition of fines increases the stability of the dune sands up to a peak of about 30% fines added, and compaction further increases the stability of the dune sands. Despite the benefits of compaction on the stability of the tailings dunes, the loss of permeability is thought to outweigh the benefits as well as the high costs involved. The stability of the tailings dunes greatly increases after re-vegetation. Compaction and densification of the tailings dunes may be necessary within the top 2 m interval if large-scale construction takes place on the sand dunes. Petrographic analysis was performed to understand the granular interactions of the sand and fines fractions, and the effect of the in situ weathering of the dune sands on the stability of the sand dunes. As the fines contents increase the gaps between the sand grains are filled, until a point where the percentage of fines begins to push the sand grains apart.

Jan 1, 2003

By T. A. Ngcobo

Paper written on project work carried out in partial fulfilment of BSc Eng (Mining)degree The purpose of this report is to assess the risks faced by mines in dolomitic compartments in particular Kloof 8 shaft. The dolomites of the West Rand comprise one of South Africa?s most natural water resources, and overlie the reefs of the richest gold mines in the world. The pumping of water from the dolomitic aquifers to prevent flooding has caused the natural water table to subside, and the resulting cavities within the dolomite rock formations that overlie many gold deposits sometimes collapse, causing sinkholes. These impacts of the mining industry could worsen over time if preventative measures are not taken. This report discusses these impacts in detail, more specifically the risks to which operations in dolomitic compartments are exposed. A risk analysis was carried out to access the risks that the organization could face and it was this analysis that allowed one to examine the best methods to combat the problems. Other factors such as geological features and seismic events were also considered for the evaluation. To aid with the completion of this work various resources were utilized. A literature study was undertaken, information was gathered from various experts who specialize in dolomitic studies, evaluations were conducted and conclusions reached. The results from the project indicated that preventative measures should be implemented and correct procedures put in place to prevent any disasters.

Jan 1, 2006

By J. -P. Chilès

The discrete Gaussian model is a very popular change-of-support model for estimating block grade distributions. It is designed for a stationary random function Z(x) that is regarded as the transform of a stationary random function Y(x) with Gaussian marginal. It is based on an assumption that is not fully true and thus constitutes an approximation to the exact solution. We examine the effect of this approximation on the modelling of the marginal distribution of block values of a lognormal random function. The initial discrete Gaussian model and a variant of that model are considered.

Jan 1, 2014

By C. Siyasiya

One of the problems that is occasionally encountered during the continuous casting of DIN 1.4003 stainless steel (hereafter referred to as 1.4003) is the side bulging effect, a problem that is generally prevalent in ferritic stainless steels. This occurs because the unconstrained narrow sides of the solidification shell are not able to withstand the ferrostatic pressure once the strand has emerged from the mould. Coupled with side bulging, there is strand width variation at high temperatures, i.e. when the steel is in the ferrite-austenite dual phase region. Both of these dimensional changes to the slab profile create some processing problems in subsequent hot rolling operations when unacceptable width variations are encountered. The strength of the solidification shell and its ability to withstand the ferrostatic pressure during continuous casting is dependent on its thickness and phase composition when exiting from the mould up to a few metres downstream. From the study of the high temperature metallurgical behaviour of this steel, it was observed that a thicker solidification shell when exiting from the mould and a higher austenite volume fraction in the steel would be favourable for the reduction of the side bulging effect during continuous casting. It was also found that as long as the d-ferrite to austenite phase ratio keeps fluctuating due to variations in chemical composition and process control in the dual phase region from cast to cast, the strand width variation problem would probably persist. The remedy to this effect lies in more strict chemical composition and process control during continuous casting of this steel. The hot ductility experiments revealed that 1.4003 exhibits good hot ductility in the strand straightening temperature range with a minimum of 75 per cent reduction in area and this was attributed to the high volume fraction of ferrite (0.2 to 0.4) in the steel. This would provide a remedy to side bulging by increasing the secondary cooling rate of the strand in order to form a thicker solidification shell without necessarily risking transverse cracking and other surface defects during unbending. Keywords: side wall bulging, resistance bending moment, applied bending moment, ferrostatic pressure.

Jan 1, 2005

By M. Gous

Namakwa Sands is a heavy minerals mining and beneficiation business in the Anglo Base Metals Division, and operates along the West Coast of South Africa. The business encompasses mining, mineral concentration, separation, and smelting operations. The smelting process comprises the carbonaceous reduction of ilmenite to produce titania slag with a TiO2 content of 86%, and iron with a carbon content of 2.5%. The Namakwa Sands smelter, situated near the Saldanha Bay harbour, commenced smelting operations in 1994, when a 25 MW DC-arc furnace was commissioned. The smelting operations were expanded in 1999, with the commissioning of a second 35 MW DC-arc furnace. Despite the fact that ilmenite smelting poses a technical challenge in terms of the high temperatures required, the physical characteristics of the slag, the constraints placed on the feedstock, and the tight product specifications, Namakwa Sands has continually increased slag production since 1995. High furnace feed-on utilization and furnace stability, complemented by continuous improvement drives, will be thevehicle to drive performance in the short-term, with longer-term performance enhancements due to strategic process development. Keywords: Pyrometallurgy, Namakwa Sands, ilmenite, DC-arc furnace, titania slag, pig iron

Jan 1, 2006

Open cast mining has been practiced in South Africa since the late1970s under near ideal geotechnical conditions. In the past decade, with the exhaustion of the traditional South African coal fields, geotechnical conditions have deteriorated. In addition, the nature of the open cast coal mining industry is changing from the conventional strip mining of virgin coal seams to the extraction of underground coal pillars by buffer blasted highwalls. These industry changes have resulted in the need to re-examine the manner in which geotechnical engineering is applied to highwall design. This paper proposes a geotechnical design rationale for open cast highwalls. Furthermore, the rationale takes cognizance of the various geotechnical hazards associated with conventional strip mining and pillar extraction by buffer blasted highwalls. The need to use geotechnical domain models and blasting geotechnics, as proactive tools for rock fall reduction, are also discussed.

Jan 1, 2001

By R. Webster

"Daniel Krige’s influence on soil science, and on soil survey in particular, has been profound. From the 1920s onwards soil surveyors made their maps by classifying the soils and drawing boundaries between the classes they recognized. By the 1960s many influential pedologists were convinced that if one knew to which class of soil a site belonged then one would be able to predict the soil’s properties there. At the same time, engineers began to realize that prediction from such maps was essentially a statistical matter and to apply classical sampling theory. Such methods, though sound, proved inefficient because they failed to take account of the spatial dependence within the classes.Matters changed dramatically in the 1970s when soil scientists learned of the work of Daniel Krige and Georges Matheron’s theory of regionalized variables. Statistical pedologists (pedometricians) first linked R.A. Fisher’s analysis of variance to regionalized variables via spatial hierarchical designs to estimate spatial components of variance. They then applied the mainstream geostatistical methods of spatial analysis and kriging to map plant nutrients, trace elements, pollutants, salt, and agricultural pests in soil, which has led to advances in modern precision agriculture. They were among the first Earth scientists to use nonlinear statistical estimation for modelling variograms and to make the programmed algorithms publicly available. More recently, pedometricians have turned to likelihood methods, specifically residual maximum likelihood (REML), to combine fixed effects, such as trend and external variables, with spatially correlated variables in linear mixed models for spatial prediction. They have also explored non stationary variances with wavelets and by spectral tempering, although it is not clear how the results should be used for prediction. This paper illustrates the most significant advances, with results from research projects."

Jan 1, 2015

By A. S. Macfarlane

The South African Institute of Mining and Metallurgy was approached by the Australian Institute of Mining and Metallurgy to present a paper on the current practice in terms of the valuation of mineral projects and properties, given the development of a Code for the Valuation of Mineral Properties, developed in Australia (the VALMIN Code), and a similar Code in Canada (the CIMVal Code).This paper is the result of research and investigation into the matter, in terms of the reporting of Mineral Resources and Reserves, financial reporting practice, the Listing Rules of the Johannesburg Securities Exchange, and various practices in valuation. The paper establishes that a strong linkage has already been established between the SAMREC Code for the reporting of Mineral Resources and Reserves and the Listing Rules, and that, for completeness, a Code for Valuation needs to be developed. This Code will be similar to its international counterparts, with the necessary inclusions which are relevant to South Africa, and will provide guidelines and definitions on matters such as transparency, materiality and competency in valuation. It proposes that a multi-stakeholder steering committee be established under the auspices of the SAIMM, to deliberate and design a process for establishing such a Code.

Jan 1, 2002

By F. -Z. Ji, A. G. Irons, M. Barati, K. Coley

In order to optimize carbon injection into oxidizing slags, in terms of carbon and iron yield, we must have a detailed understanding of the kinetics of the reactions involved. The current study measures the rate of carbon oxidation during injection at steelmaking temperature by means of injections of coal into EAF slags. The compositions of analysed outgoing gas were used to calculate gas flow rate and hence the gasification rate of carbon. A fundamental equation to predict residual carbon in slags was developed. The predictions using this model at moderate injection rates are in good agreement with experimental data. The reaction rate of EAF slag with carbon is under mixed control by the slag gas and the gas carbon reactions. The relative importance of each step depends mainly on the v-ratio of slags. A relative reactivity parameter ? has been defined and it is found to be important to carbon-slag reaction kinetics and slag foaming. Key words: carbon-slag reaction, kinetics, slag foaming.

Jan 1, 2004

By R. G. B. Pickering

Over the last few years Lonmin Platinum and Sandvik have embarked on a unique partnership of collaboration through a systematic approach to developing equipment to mechanize and automate narrow reef platinum mining. After the initial design and manufacture of the equipment the key aspect is the integrating equipment, people and method into a mining system. Another key aspect of mechanization is the optimization of equipment utilization, and this philosophy has ensured continual evolvement of mining methods. This paper describes the trials and development that have resulted in the mining method described as Lonmin mechanized breast.

Jan 1, 2007

By M. M. Makhofane

Anhydrous zirconium tetrafluoride can be used as a precursor for the manufacturing of nuclear-grade zirconium metal. This can be done by fluorinating plasma-dissociated zircon with ammonium bifluoride in a batch reactor. This paper describes the batch process. It was proved that anhydrous zirconium tetrafluoride can be manufactured by this route as confirmed by X-ray diffraction. The process shows potential for scaling up to the kilogram scale and possibly the tonnage scale.

Jan 1, 2012

By C. Balci

Specific energy is defined as the amount of work required to break a unit volume of rock and is used to predict the performance of mechanical miners. It is obtained from full-scale rock cutting experiments, which require large block samples, experienced personnel and expensive equipment found in only a few research centres in the world. Estimation of the optimum specific energy, at which a given geological formation is excavated at optimum cutting geometry in the most energy efficient manner, from mechanical rock properties to predict the performance/efficiency of roadheaders is the basic aim of this study. The mechanical rock property tests require only core samples, which are easier to obtain and to test. In this context, full-scale rock cutting tests are performed on 23 different rock, mineral and ore samples including sandstone, claystone, tuffite, chromite, trona and copper collected from some operating mines in Turkey. The optimum specific energy values are obtained for each sample. Physical and mechanical property tests are performed on the core samples obtained from the same samples to determine uniaxial compressive strength, indirect (Brazilian) tensile strength, static and dynamic elasticity moduli, Schmidt hammer rebound values, density, and Cerchar abrasivity index. The relationships between the optimum specific energy and the mechanical rock properties are analysed using statistical methods. The results indicate strong relationships between the optimum specific energy and the mechanical rock properties. The strongest relationships are found by using uniaxial compressive strength and tensile strength. The performance models developed in this study are in good agreement with the empirical models previously developed for roadheaders and can be used reliably for prediction purposes. Keywords: Mechanical excavation, roadheader, performance prediction, rock cutting, optimum specific energy, mechanical properties of rocks.

Jan 1, 2004

By L. Li

The performance of microemulsified diesel and conventional diesel collectors in coal flotation was compared by flotation indicators, including combustible recovery, ash content of the clean coal, and the flotation index. An efficient separation with lower dosage was obtained using the microemulsified diesel collector. Under optimum separation conditions, the microemulsion consumption was 100 g/t less compared with diesel. The saving in diesel consumption using the microemulsion reached about 70%, disregarding the consumption of the surfactant and cosurfactant. Frothing tests showed that the frother dosage was decreased by using the microemulsion collector, because of the surfactant and cosurfactant added during preparation. The microemulsified diesel collector is superior to the conventional diesel collector in terms of diesel consumption and separation efficiency, but the selectivity requires further improvement. Keywords froth flotation, microemulsified collector, coal.

Nov 1, 2013