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Abstract : The computation of reliability index or failure probability of slopes can be transformed into an optimisation problem. In high rock slope engineering, it is usually a multimodal optimization problem. The traditional optimization techniques are difficulty to find out the global optimal solution because of their easily falling into local optimal value. Recently, a new kind of bionic algorithm - ant colony algorithm (ACA) - has been used to solve this problem. In this paper, the structure of ant colony algorithm and the transfer probability of ants are modified to evaluate the failure probability of complicated slopes. A new adaptive ant colony algorithm (AACA) is proposed to determine critical slip surface and its corresponding failure probability of complicated slopes. A case study is given to verify the proposed approach. The results show that the presented method has obvious advantages compared with traditional methods. ZUSAMMENFASSUNG: Die Rechnung des Zuverlaessigkeitindexes oder der Zerstoerungswahrscheinlichkeit kann sich in einer Optimierungsfrage umwandeln, im Bauprojekt an hoehe Gebirgehang, handelt es sich meistens um eine Optimierungsfrage ueber Multi- Spitzenwert. Mit der traditionelle Optimierungsmethode ist es schwer eine umfassende Loesung fuer die Optimierung zu finden wegen des leichte Verfallens in Beschraenkung der Teiloptimierungsloesung. Mit dem neue Bionik- Algorithmus —— Ameisen - Kolonie- Algorithmus wird dieses Problem geloest. In diesem Text hat man eine Strukturverbesserungsloesung fuer das Ameisen- Kolonie -system und die Wahrscheinlichkeit der Ameisenkolonie erwaehnt, und damit wird man die Zerstoerungswahrscheinlichkeit des komplizierte Hangs feststellen. Mit dem neuen Ameisen- Kolonie- Algorithmus kann man die gefaehrlichste Gleitflaeche und die entsprechende Zerstoerungswahrscheinlichkeit herausfinden. Die in diesem Text beschriebene Methode wurde durch Praxis geprueft. Durch die Pruefergebnisse wurde es gezeigt und bestaetigt, dass der neue Bionik- Algorithmus vorteilhafter als der traditionelle Algorithmus ist. Résumé : Le calcul de l’indice la fiabilité ou de la probabilité de ruptures peut être transformé en un problème de l’optimisation. Pour le cas du génie des pentes de haut rocher , le problème se pose en général en l’optimisation de multi-crêtes. Les techniques traditionnelles conduisent facilement à la solution optimal partielle au lieu de celle globale. Récemment un nouveau type de bionique algorithmique a été appliqué pour la solution de ce genre de problèmes, c’est l’Algorithme Colonie de Fourmis. Dans l’article il est proposé de modifier la structure du système de la colonie de fourmis et la probabilité de transfert des fourmis en vue d’évaluer la probabilité de ruptures des pentes de haut rocher complexes, par ailleurs un nouveau algorithme adapté de colonie de fourmis est formulé pour déterminer la surface glissante critique et la probabilité de ruptures correspondante. Les techniques proposées dans l’article sont vérifiées à travers des expérimentations dont les résultats ont prouvé que les techniques présentées dans l’article sont évidemment meilleures que celles traditionnelles.

Jan 1, 2003

Keywords: Pyrometallurgy, Pretoria University Substantial research in pyrometallurgy at the University of Pretoria started in 1980 with the appointment of Rian Dippenaar to the Iscor Chair, a position that he held until 1996, when Chris Pistorius became the leader of this pyrometallurgy group. This paper reviews the main research themes over the quarter-century from 1980 to 2005, as well as some of the industrial developments that have shaped the research approach. The main topics have been the use of electrochemical sensors for equilibrium measurements, ilmenite smelting, steel processing, and reduction.

Jan 1, 2006

By Braam Blom

PK2 Ventilation shaft is part of Paardekraal No 2 twin shaft system that is being developed to replace depleting Merensky reef production at Paardekraal shaft complex. The sinking team at this shaft faced considerable challenge of improving the total sinking cycle in order to be able to deliver the fully equipped shaft on time and on schedule. The cladding support cycle was identified as the tedious and time consuming activity in the overall shaft sinking operation. Reduction in the time required for handling and setting up the support installation equipment, and the time required for subsequent installation of the necessary support has a direct impact on the overall cycle time, and consequently the overall productivity and efficiency of the sinking operation. This reduction in support cycle was achieved by making use of machine carousel. The objective of this paper is to describe the support methodology that was used during the ventilation shaft sinking and the use of the machine carousel to reduce the cladding support cycle. The machine carousel replaces the traditional use of machine kibble in conventional vertical shaft sinking and has been designed specifically for installation of sidewall support at the shaft bottom during the sinking process.

Jan 1, 2009

By N. McEwan

Keywords: refractories, chromite, Marico This paper examines the role of refractory-grade chromite in refractories. The chromite deposit at Verref?s Marico Chrome mine is described. The refractory properties of chromite and their role in basic refractories are described. The properties and metallurgical applications of chrome-containing refractories are described and finally environmental issues associated with chrome-containing refractories are discussed.

Jan 1, 2011

By R. Thomason

Thank you Dr Barcza, President of the South African Institute of Mining and Metallurgy, for inviting me to share our experiences in Australia as regards the competency movement and my Association?s experience in assisting engineers become managers. This is my second visit to South Africa, and I am struck by the similarities between our countries. This extends to the professional issues associated with engineering and competencies in particular. I propose to outline two exciting stories today. ? Development of competency standards for professional engineers in Australia. ? Development of a management programme which has assisted professional engineers regain positions of leadership in Australian industry and government. First of all I would like to outline the Association of Professional Engineers, Scientists and Managers, Australia(APESMA).

Jan 1, 1997

By C. Sensogut

The phenomenon of spontaneous combustion is one of the major hazards encountered in underground coal mines both from the safety aspects and on economic grounds. Every occurrence, however small, if not tackled effectively in the early stages can develop into open fire, or explosion of gas or coal dust. In terms of economy, even dealing with small incidents may be costly in terms of labour and materials, and in case of a sealing off of a district being necessitated, the loss of face equipment and sterilization of reserves is potentially great. Therefore, expense and effort in prevention and detection of such heating, together with a high state of readiness for dealing with likely event, is completely justified and may be considered as a sound investment. In order to achieve this investment, it may be worth to pinpoint the centre of the fire occurring due to autogenously heating which is supposed to be great assistance to inert it at a least cost and time. Therefore, it is the aim of this work to model the spontaneous combustion in the goaf.

Jan 1, 2002

By R. L. Gibson

Manpower competencies in the mining, minerals processing and energy industries in South Africa into the next century will, to a large extent, derive from the nature and quality of the teaching which pupils receive at school. This paper provides an overview of the current developments towards a new National Curriculum in South African Schools and highlights areas in which the Minerals Industry might provide input into this process.

Jan 1, 1997

By P. Gonzalez, C. Ariyo, L. Holappa

Oxidation state of titanium was determined in CaO-SiO2-TiOxslags in the composition range25–53 per cent CaO, 27–46 per cent SiO2, 10–55 per cent TiOxat 1873K using gas equilibration method. In the experiments, slags with different titanium oxide contents were equilibrated with a known carbon monoxide and carbon dioxide ratio. The results were used to determine the Ti3+and Ti4+contents as well as the activity coefficient ratio of corresponding oxides in the slag. The dependency of the activity coefficient ratio as a function of oxygen partial pressure was determined. Keywords: titanium, titanium oxide, activity, activity coefficient, slag iron, carbon monoxide,carbon doixide, gas, equilibrium.

Jan 1, 2004

By J. C. Carrasco, M. Sánchez, R. Jara, F. Marquez, F. Parada, R. Parra, J. Palacios

In past years, Chile has been the largest copper producer in the world and for 2002 mining represented country average of 10 % of the GDP, accounting for 47 % of the total exportation. As copper sulphides are the main mining resources in the country, the metal is produced using the classical processes of flotation and pyrometallurgical extraction. Seven copper smelter plants, which extends from the northern Atacama desert to the central part of the country produced1,522,000 metric tons of fine copper in 2002, approximately one half of total copper concentrate production, with a notorious environmental impact due to the great amount of slag produced during these extraction steps. In this work, a global characterization of copper pyrometallurgical slags produced and disposed of in Chile and worldwide is done, and the concept of total project development is considered to explain the scopes of the study, recovering different compounds and generating new activities around mining. The presentation is completed with the proposal of various methods and techniques being developed today in a joint project between smelter plants and the University of Concepción, with the support of the Chilean government and mining companies, addressed to generate new materials from copper slag. Recovery of copper, molybdenum, precious metals, silica and iron, that is the most abundant component of the slag, are the goals for this research. Metals, commercial compounds, alloys and different forms of iron oxides for steel industry are proposed products.

Jan 1, 2004

By G. Tranell, L. Kolbeinsen, S. Gaal, J. Safarian

The effect of carbon material properties on the rate of MnO reduction from ferromanganese slag by solid graphite was investigated. A sessile drop technique was used to study the reduction rate of a synthetic slag containing 45 wt% MnO at 1500 and 1600 ºC. Different types of graphite substrates were used and the con-tact angle between slag droplets and substrate were measured in-situ. Moreover, the slag droplet volume during the interaction with the graphite substrates was calculated and normalised. The mathematical relationship between the slag density during the reduction and the normalised slag droplet volumes during the reduction were derived and the MnO reduction curves were then calculated. A method for measuring the slag reactivity of solid carbon was defined and used to qualify the propensity of the different graphites to react with the liquid slag. Some supplementary studies such as manganese evaporation measurement and EPMA analysis for determining the extent of MnO reduction were also carried out. It was observed that there is nota significant difference in the wetting angle of the graphite substrates by the slag, and the wetting is not changed within the temperature range of 1500-1600ºC. However, the changes in the contact angle during the slag reduction at 1600ºC are more than at 1500ºC. The kinetics of MnO reduction is dependent on the type of graphite and it is more dependent on the graphite properties at lower temperatures. On the other hand, the dominant properties of graphite on the reduction rate vary with temperature. A multivariate analysis on the graphite properties and the parameters related to the slag reactivity indicated that the kinetics of MnO reduction is mainly dependent on the temperature, and then on the graphite properties. It was also found that at1500 ºC the surface area and the CO2 reactivity are the most important graphite properties for the slag reduction, suggesting that the reactivity of carbon is rate controlling at 1500 ºC. However, the porosity related parameters are the most important graphite properties at 1600 ºC, suggesting that CO gas desorption is rate controlling at high temperatures.

Jan 1, 2007

Outsourcing of specialist and non-continuous services is common practice in international mining operations. There is an increasing trend towards this practice in South Africa as a result of the major organisational changes that have taken place in the industry, and as lower revenues and production cost pressures have reduced profit margins. Many specialist functions have been outsourced in the industry for a long time, an example being shaft sinking, which is undertaken by specialist shaft sinking contractors. In the professional services area, some activities have been outsourced, for example the design and construction supervision of tailings dams, but mining related activities such as geology, mine planning and scheduling, engineering, ventilation, and rock engineering, have traditionally been carried out by in-house staff. In this paper some of the industry problems which have led to an increase in outsourcing of professional services are considered. Then the pros and cons of outsourcing are dealt with before outlining the factors which should be taken into account in choosing an outsourcing partner.

Jan 1, 1999

By G. Broadbent

It is an honour to be invited as a speaker to this ICCR conference and a pleasure to be with you here in South Africa. I have been asked to talk about the competitiveness of coal versus other energy alternatives. Coal supplies nearly one-quarter of the global primary energy. Its most direct competitors are gas, nuclear and renewables. Oil is predominantly for transport fuels. Fuel oil is competitive with coal when crude is below its long-run average price and has some niche opportunities. But I will confine my comments to nuclear, renewables and particularly natural gas as the most potent current competitive threat to coal. Competitiveness is more than just cost and price; there is environmental acceptability, security or reliability and increasingly image. These factors are more of a spectrum than discrete issues. Dollars and cents remain the key issue for competitiveness but one must recognize the impact of politics in sustainable development and energy security.

Jan 1, 2001

By Y. Nakata, K. Nagata

Plasma is partially ionized gas composed of ions, electrons and activated elements at high temperature. Some flying ash from incinerated municipal waste is melted to become glass by a transfer-type arc plasma furnace. As the glass is ionic silicate, when an electric current passes through anode to cathode, ions in molten slag electrochemically react with electron in plasma at the surface of molten slag. In case of molten Na2O-SiO2, sodium ions in the molten slag carry electric current and SiO2are reduced to evaporate as SiO gas by electron in plasma. The cases of Ag+in NaNO3-KNO3molten salt and Fe2+in FeO-SiO2slag were examined. The amount of cathodic reaction is larger than that of anodic reaction and not apparently according to the Faraday?s law on the electrochemical reactions.

Jan 1, 2004

By N. N. Malila, N. R. Shoko

The ever-increasing pressure on the profit margins of ferro-chrome producers and the gradual depletion of deposits of rich hard lumpy chrome ores calls for the ferrochrome industry to maximise the use of fine fractions of concentrates and friable chromite ores. Zimbabwe is endowed with huge deposits of refractory and friable ores that occur on and off the Great Dyke complex. The conventional metallurgical process of smelting of chromite ores in submerged arc furnaces is favoured by the use of refractory hard lumpy ores. The requirement to use all lumpy ore has been circumvented to a large extent at Zimbabwe Alloys. The use of briquetted chrome ore fines in the production of Ferrosilicon Chrome and High Carbon Ferrochrome has yielded positive results over a period in excess of twenty-five years. Of the three industrially used methods of agglomeration of chromite ores; sintering, pelletisation and briquetting, briquetting is preferred because the other two are associated with higher capital and operational cost. Zimbabwe Alloys has developed operational and technical expertise on the briquetting and utilisation of chromite ore fines and concentrates. Variations in the quality of available chromite ore fines imply that their amenability to briquetting is a dynamic problem. Appropriate briquetting parameters to guarantee quality briquettes are essential to the successful use of briquetted chromite ore fines. In developing a technology for briquetting of chromite ores, it is important not only to study the mineralogical and grain-size characteristics of the chromite ore fines but also to make an informed choice of the type and quantity of the binder and the conditions for producing a physically and chemically competent green and cured briquette. This paper discusses Zimbabwe Alloys' experience on the briquetting process and the advantages derived in the smelting of the briquetted chromite ore fines in comparison to the use of conventional lumpy chromite ore with respect to improvements in chromium recovery and as a consequence related efficiencies and unit cost of production.

Jan 1, 2004

A large number of brittleness concepts have been used in very different studies in the literature. One of them is the B1brittleness concept. In this study, the objective is to criticize the B1 brittleness concept on rotary blast hole drills. The B1 brittleness concept, the ratio of uniaxial compressive strength (sc) to tensile strength (sT), are widely used as a rock brittleness concept in the literature (Inyangand Pitt, 1990; Verhoef, P.N.W. 1993; Neil, D.M. et al.1994;Becker, et al.1984; Evans and Pomeroy, 1966; Göktan, R.M.1992; Kahraman, S. 2001; Yamaguchi, U. 1970; Verhoef, P.N.W. et al.1996; Bilgin, 1982; Howarth and Rowlands,1987; Howarth, D.F. et al. 1986). So, it was used as a rock brittleness concept in this article. The value of the B1brittleness concept is equal to the tangent of ß angle in the following graph. It was seen that more meaningful relationships could be obtained with the B2 brittleness, the under ?Area?(= 1/2(scxsT) = B2) under the curve, instead of tangent ß, (=B1), of the curve.

Jan 1, 2003

By V. Yahorava

Resin-in-pulp (RIP) technology has recently often been considered for the direct recovery of base metals and uranium from dense pulps. Implementation of RIP will eliminate the requirement for any solid-liquid separation downstream of leaching and has the potential to combine the recovery and purification steps, hence reducing both capital and operating costs. The recovery of the valuable metal is expected to be higher when RIP is used, especially where the leached solids are difficult to settle or filter, and to wash. The main concerns about the use of RIP for uranium recovery from dense pulps are the impact of silica on the resin?s metallurgical performance and the operating costs that would be associated with resin loss. Although a number of resin manufacturers have been developing much improved RIP-grade resins, it is critical that the most cost-effective resin be selected. Mintek currently is doing a significant amount of work on silica fouling of RIP-grade strong-base resins in acidic leach liquors and the effect it has on the performance of the resin, including its durability. This paper describes the results of the test work done on silica fouling and its impact on plant design input data. Resin durability test work was done using various laboratory techniques, but durability was also evaluated on a relatively large scale using actual pumps, screens, and mechanical agitation. Based on the results generated, a preliminary economical evaluation was done to estimate the impact of resin loss on the overall economic viability of a specific application. Keywords: resin-in-pulp, silica fouling, resin loss, equilibrium, kinetics, elution, durability, mechanical strength, resistance to attrition.

Jan 1, 2009

By N. E. Yasitli

There is a considerable amount of lignite reserve in the form of thick seams in Turkey. It is rather complicated to predict the characteristics of strata response to mining operation in thick seams. However, a comprehensive evaluation of ground behaviour is a prerequisite for maintaining an efficient production, especially when top coal winning by means of caving behind the face is applied. A comprehensive modelling of deformations and induced stresses is vital for the selection of optimum production strategy. In this study, numerical modelling and analysis of a longwall panel at Omerler underground coalmine have been carried out by using the software called FLAC3D developed based on the finite difference technique. Firstly, a 3-D numerical model of the M3 panel has been prepared. Secondly, induced stresses formed around the longwall face have been determined as a function of face advance where the face was located at the bottom of thick coal-seam. Results obtained from modelling studies have revealed that the front abutment vertical stress was maximum at 7 metres in front of the face and magnitude of front abutment stress was found to increase up to a distance of 200 metres away from the face start line. As the face was further advanced after 200 m from the face start line, there was not any significant change in the characteristics of front abutment stresses. Results of numerical analysis of the panel were in good agreement with in situ observations.

Jan 1, 2005

By P. den Hoed, J. Nell

Tests were conducted on samples of rutile, titaniferous slag and ilmenite; each sample was mixed with coke and chlorinated in a bubbling fluidized bed at 1000°C. Profiles of the rates of chlorination of species were constructed from chemical compositions of the bed residues at different durations. From the start FeO and MnO are chlorinated quickly and all but entirely in a fraction of the time it takes to chlorinate all the TiO2. When the level of FeO is significant, as in slag and ilmenite, FeO is chlorinated faster than TiO2is. In these oxides, there is an inverse relationship between the rates of chlorination of FeO and TiO2during this first stage; the relationship, moreover, correlates linearly with the initial percentage of FeO in the oxide. We identify three stages in the chlorination process; a first, in slag and ilmenite, when FeO is being chlorinated; a second, when TiO2is most readily chlorinated; and a third, towards the end, when the levels of TiO2are reduced to those of other species. The rates at which individual species are chlorinated are analysed in terms of their appreciation or depreciation with respect toTiO2

Jan 1, 2003

Paper written on project work carried out in partial fulfilment of M.Sc. (Chemical Engineering)degree Identification of non-linear systems can be a daunting task and in the process industries the problem is complicated considerably by the presence of noise from various sources, non-stationarity of the data and intermittence, such as observed in particulate flows. Traditional methods, such as frequency analysis and linear model-ling do not handle these systems well. Similar problems arise with the application of non-linear theory developed over the last few decades, where much of the analysis depends on embedding of the data in a phase space or pseudophase space, since these methods were not originally designed to deal with noisy systems. In contrast, singular spectrum analysis is a method which can be used to identify structure and distinguish noise from important information in multivariate data, such as the trajectory matrices of time series measurements. It provides an orthogonal basis onto which the data can be transformed, so that components of the time series can be investigated individually. With Monte Carlo methods, the components can be compared with those from linear surrogate data in order to identify possibly non-linearities in the data. In this paper, this versatile technique is briefly explained and illustrated by means of case studies.

Jan 1, 2003

By S. Lin

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

Jan 1, 2001