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By R. J. Hundermark, S. Sun

The oxidation state dependence of the electrical conductivity of a calcium ferrite slag with 25 wt% CaO was measured at 1300°C using a shallow slag layer and two-electrode technique. The experiments were started in air and the slag was sequentially reduced by means of a controlled gas atmosphere using CO2and CO. The electrical conductivity in air was approximately 300 S/m and increased with reduction to approximately 1900 S/m at a pO2of 10-10atm. The interest in the oxidation state dependence of the conductivity of calcium ferrite slags was to provide a comparison with the conductivity of iron silicate slags and to establish the effect of slag basicity on the electrical conductivity and its oxidation state dependence. The results obtained are discussed in terms of the slag structural information available in the literature. The co-ordination of the ferric ions appears to play a large role in determining the electrical conductivity. Keywords: calcium ferrite, slags, electrical conductivity.

Jan 1, 2004

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

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

Jan 1, 2003

In extracting base metals from orebodies, sulphide as well as oxide, the main environmental concern is sulphur, whether in the form of sulphurous gases or sulphate in liquid form. Generally sulphur is in over supply in developed countries mainly because of strict legislation to capture it. In developing countries, on the other hand there is usually a shortage of sulphur because of less strict environ-mental legislation. Africa falls in this second category and the African continent imports substantial amounts of sulphur, despite the fact that large quantities of sulphur are emitted by smelters, thermal power stations, coalmines, fertilizer manufacturers and others. Other than making acid from gaseous emissions, existing methods to capture sulphur from gaseous and liquid effluents are uneconomical and it ends up in the environment either as ammonium sulphate (from gaseous effluents) or as gypsum (from liquid effluents). The CSIR?s Environmentek and Key Structure Holdings have developed a process whereby gaseous sulphur emissions and sulphates in liquid effluents can be economically captured and converted into elemental sulphur and metal carbonates. The elemental sulphur is of high purity as it is precipitated from a gas stream and is readily marketable. The metal carbonates (barium or calcium) can be recycled back to the process or marketed. The only harmful by-product of the process is carbon dioxide. Should natural gas or methane be available, the carbon dioxide could be reduced by about one third. Should solar, wind or hydro energy be available to generate hydrogen, the carbon dioxide emissions would be zero. Employing this technology could make Africa independent of sulphur imports and furthermore reduce the impact of acid rain and seepage of sulphate from gypsum and other waste dumps into the environment.

Jan 1, 2005

By J. Maiti

This study examined the group differences in accident susceptibility among underground coal mine workers accounting for their personal and workplace characteristics. A logistic regression model was used for this purpose. Data were collected from five underground coal mines for a period of four years. The case study results revealed that different age and experience groups of workers bear no significant differences in their accident susceptibility; however, the workplace location and occupation groups show significant differences in their risk of injuries. It is inferred based on the logistic model results that among the three occupation groups, the face workers are more susceptible towards accidents/injuries compared to the haulage and other workers. Key Words: Mine Safety, Accident Susceptibility, Group Differences, and Logistic Regression.

Jan 1, 2001

By R. P. Mohring

The South African Coal Industry had its beginnings in the Eastern Cape in 1859 when coal was mined to satisfy the fledgling settlements in the Eastern Cape. The growth in the industry was relatively slow up to the early 1970s when, firstly, the export business was expanded coupled with a major increase in the quantity of coal converted to liquid fuels and utilized for power generation. To meet this increased demand the industry developed many new operations employing the latest mining technology and systems. Coal production in South Africa reached 204 million tons in 1996 and revenue from exports reached R8 billion making it the second-largest foreign exchange earner after gold. In his address Rick P. Mohring describes the role coal plays in the international energy scene and outlines South Africa?s position as a producer and consumer of coal, and the challenges facing the industry. A wide range of steam-coals are produced to satisfy both the local market (power generation, coal conversion and the metallurgical industry) and the export steam-coal market. South Africa is in a unique position regarding the export market as it is still a relatively low-cost producer and is geographically well-placed to play in both the European and Far East markets. There are, however, a number of challenges facing the industry. To retain our competitiveness in the international market, ways of minimizing the cost pressures caused by high-cost inflation, increased environmental protection obligations and a decreasing quality resource base need to be sought. Locally the coal mining industry has a major role to play in Eskom?s goal of reducing the real cost of electricity by 15% in the next three years. Safety and health, productivity and the adaptation of the latest technology are issues being addressed by the industry to maintain its dominant position within the South African economy.

Jan 1, 1997

By D. Pillay

Outsourcing? and ?sub-contracting? have become buzzwords in recent years, as SA industry becomes increasingly exposed to the global economy, and global competitiveness. In its effort to ?catch up? after years of relative isolation, there is a concerted effort to learn from global ?best practice?, in order for South African companies, and the SA economy, to become ?winners?. There seems nothing wrong with this approach at face value. Companies need to compete and be profitable if they are to remain in business. Failure will in the end mean bankruptcy, and the loss of jobs. However, if one interrogates the precise practices, and their implications for all concerned?not just shareholders and employers, but workers, communities, the environment, future generations, the national economy?then the picture can change dramatically. ?Best practice? for whom?

Jan 1, 1999

By S. Dessureault

Computer Integrated Mining (CIMG) is a process of using computer networks to transform islands of enabling technologies into a highly interconnected mining system. CIMG involves the integration of advanced technologies at various levels in the mine business to achieve higher flexibility, better quality of processes and control, and improved profitability. Justifying the benefits of CIMG are difficult as many of the advantages are derived from improved flexibility, quality, and control. Justification is based on the evaluation of the benefits to be gained, compared to the required capital investment. Management tools used in mining are currently inadequate in assessing the value of advanced technology whose benefits are primarily qualitative. A key aspect of successful implementation is management acceptance, which has to be won through the capability to justify the technology?s financial costs and the true value of all of its benefits. The manufacturing industry faced similar justification difficulties when adopting advanced technology in factories. A significant amount of funding and research was invested in developing management strategies and approaches to justification. Many of the problems that faced the transformation of the manufacturing industry in the late Eighties and early Nineties are now facing mining. The solutions derived for manufacturing may help mining in its transition to an increased reliance on integration technology. Reviewing the industrial history of computer integrated manufacturing identifies several tools and strategic frameworks that can be adapted for mining. Keywords: Computer integrated mining, justification techniques, CIM, information technology.

Jan 1, 2004

By J. E. McGill

The junior and small-scale mining sectors in South Africa play an important role in the livelihoods of numerous communities. Mining presents an opportunity, in the post-1994 democratic era, for many individuals to obtain access to much required empowerment and socio-economic development. These sectors are, however, not without numerous characteristics that pose problems for operators, legislators, and other role-players. Mining is inherently risky, with operators experiencing frequent difficulties and challenges throughout the life of mine. Opportunity exists, and needs to be enhanced, for junior and small-scale prospects and operations to include technical risk assessment techniques in documentation presented in search for funding, and in optimizing monthly planning and longer-term functioning. The focus here is to explore how the risk management cycle may currently be applied to a mineral resource suitable for exploitation by the junior and small-scale mining sectors. No management process can create additional value in the ground, but various available mechanisms can go a long way to quantifying the inherent risk that exists, highlighting the need to manage the risks and hopefully allowing the entrepreneur access to the intrinsic opportunities of the emerging mining sector in South Africa.

Jan 1, 2006

Ongoing rockpass problems on mines within the South Africa region, prompted AngloGold Ashanti to embark on a risk assessment of major rockpasses. This commenced with the collection of relevant data to identify gaps in the available knowledge and identify existing problems. This was followed by an assessment of rockpass layouts to determine existing and potential interactions with other excavations. An initial risk assessment has been completed and the rockpasses have been ranked in terms of their risk profile. The lack of geological data and an easy and reliable method of surveying rockpasses have been identified as problem areas. Shortcoming is terms of rockpass management procedures have also been identified. Further work is required to quantify the risk in terms of probability of occurrence and consequences.

Jan 1, 2005

By S. Sarac

Solving ventilation networks of natural splitting is a basic problem in mine ventilation. Several mathematical techniques are used to solve this problem. This paper proposes a new method which combines the advantages of both classical Hardy Cross method and unconstrained optimization techniques. The trials carried out on model networks have shown that the method offers some facilities in the analysis of mine ventilation networks. Keywords: Ventilation network analysis, Hardy Cross method, Steepest Descent method.

Jan 1, 2000

By J. Bongardt

Ecologically acceptable techniques are described for the handling of waste materials from the fabrication industry. New production methods and the recycling of sludges from grinding and other waste materials are suggested.

Jan 1, 1997

By C. F. Vos, J. D. Miller, J. C. Davidtz

Small replacements of C12-trithiocarbonate (C12-TTC) for dithiocarbonate (DTC)/dithiophosphate(DTP) in a reagent suite for the flotation of platinum group metals (PGM) have significantly improved the rejection of gangue. Coupled to this is an improvement in kinetics, grade and recovery of PGMs. In a pilot-plant trial, after a 5 mole per cent replacement of the current DTC/DTP collector combination by C12-TTC, large opaque bubbles were replaced by small clear ones. In addition, a similar flotation response was realized with one-third of the current depressant dosage. During a preliminary plant trial on underground UG2 ore, the initial rougher concentrates were characterized by higher PGM concentrate grades and this was in part due to improved chromite rejection. The concentrate produced from the TTC trial also exhibited a much finer particle size distribution. The overall circuit performance, which included secondary regrind and flotation, showed an increase in concentrate grade of approximately 44% while the tailings grade remained unchanged

Jan 1, 2006

Records over the past ten years indicate that there is potential for serious multiple accidents due to engulfing associated with rockpasses. Significant attention is not usually given to the design of rockpasses, with the implication that mistakes leading to poor performance of the passes are often repeated. This paper outlines general guidelines for the design, support, operation and rehabilitation of rockpasses based on information obtained from the limited amount of literature on the subject.

Jan 1, 2005

By R. P. Mohring

Before we look at what the challenges and opportunities for future coal mining will be, it is appropriate to have a look at whether there will be a coal industry in the future. There is much talk about the damage caused by the burning of fossil fuels and the need to replace coal and oil with more environmentally friendly energy sources. Yes, there is evidence that the current practice in burning of fossil fuel has certain negative environmental effects, however, the adverse effects for global economic development from inappropriate measures to control greenhouse gas emissions would be severe.

Jan 1, 2001

The acoustic signals emitted from a laboratory-scale ball mill were used for the estimation of the comminution of two complex sulphide ores, viz. Merensky and UG2 ores from the Bushveld Igneous Complex in South Africa. The digital acoustic signals were transformed to power spectral densities that could be related to particle size distributions (-75 µm to 4000 µm) in the mill by use of continuum regression. This approach is more general than principal component regression methods or Kalman filtering used previously and resulted in significantly more accurate calibration in the case of the Merensky ore, where approximately 93.4% of the variance in the particle size distributions could be explained. With fewer data available, the variance in the particle size distributions in the UG2ore could be explained less accurately (82.4%), but still satisfactorily. In addition, smaller particle sizes (less than 300 µm) could be modelled more accurately in the case of the UG2 ore.

Jan 1, 2000

By S. Sarac

In this study, graphical and mathematical methods used to determine operating points in single or multiple fan ventilation systems are summarized. The problem is mathematically formulized for parallel connected fans in which analytical solutions are not possible. For n number of parallel connected fans, a non-linear equation system that consists of n number of non-linear equation sis derived. The Newton-Raphson method, which is a numerical analysis method, is adapted to solve this non-linear equation system and the solution steps are given as an algorithm. A computer program based on this algorithm is written and its applicability is proved.

Jan 1, 2000

By E. Munnik

The Chambishi Metals Cobalt Plant in Zambia has recently installed a novel oxidation/precipitation pressure leach process as part of the COSAC (CObalt from Slag And Copper as by-product) Project. Aniron-cobalt-copper alloy, produced by the carbothermic reduction of slag, is atomized and pumped to the COSAC Leach Plant, where cobalt and copper are recovered as dissolved sulphate salts, andiron is rejected primarily as hematite. Cobalt and copper are subsequently recovered as cathode metal in the existing Chambish ioperation by conventional electrowinning. This paper examines the challenges faced during the design and subsequent successful commissioning of the COSAC Leach Plant. The challenges discussed include alloy handling, autoclave design, autoclave cooler design, residue liquor recovery and the water balance design. Keywords: Chambishi, Avmin, COSAC, Zambia, Copperbelt, cobalt, copper, alloy handling, pressure leach, autoclaves, cooling, filtration.

Jan 1, 2003

By G. Westcott

Impala Platinum, the second largest platinum producer in the world, is embarking on a major expansion strategy to increase its platinum output from 1.95 moz to 2.8 moz by the year 2008. The smelter complex, situated in Rustenburg, will undergo substantial modifications, and will require a solution to the capture and treatment of the smelter off-gases and dust produced during smelting and converting operations. One of the solutions explored was an integrated approach, where all the off-gases from both the primary smelting electric furnaces and the converter operations are routed to a large central gas cleaning and double catalysis, double absorption acid plant. In-line sulphur burning, utilizing a highly flexible LURO1spin cup burner with a turn down ratio of 50%, ensures that the acid plant operates independently of operating conditions at the smelter complex.

Jan 1, 2007

By D. R. Hack, N. M. Sirakov, M. L. Feves, M. Iwanowski

This paper presents a new approach capable of volume calculation of 3D reconstructed geological objects. The method is based on a well-known concept that states the volume of an object can be computed as the limit of the sum of the area of infinite number of sections, which cut the 3Dobject. Since shortage of input data about the geological objects usually exists, Mathematical Morphology and polynomial interpolation are employed to generate a set of intermediate sections between the set of initial sections. A Mathematical Morphology tool is applied to compute the area of the two of sets initial and generated 2D sections. Regularities together with Delaunay Triangulation are employed to perform 3D reconstruction. A formula is developed on purpose of volume calculation of the reconstructed objects. A set of ten theoretical, electrical resistivity cross-sections were generated and used to perform an experiment to show the capability of our approach to estimate the volume of complex 3D geological object in case of sparse 2D sections. The volume determined using the morphological approach presented in this paper show good correlation with the volume of the original input object. Advantages and disadvantages of our volume calculation approach are discussed in the conclusion of this paper. Keywords: electrical resistivity, sparse 2D sections, geological objects, smooth 3D visualization and volume calculation.

Jan 1, 2003

By A. D. Thomas

Some years ago, the authors developed an analysis of non-Newtonian pipe flow based on enhanced turbulent microscale and associated sublayer thickening. This analysis, which can be used for various rheologic modelling equations, has in the past been applied to smooth-walled pipes. The present paper extends the analysis to rough walls, using the popular Bingham plastic equation as a representative rheological behaviour in order to prepare friction-factor plots for comparison with measured results. The conditions for laminar-turbulent transition for both smooth and rough walls are also considered, and comparisons are made with earlier correlations and with experimental data.

Jan 1, 2007