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By D. S. van Vuuren

Titanium bearing resources can selectively be chlorinated at temperatures below 200°C if the Ti02 in the feed is nitrided before chlorination. However, the nitriding reaction is highly endothermic, requires highly reducing conditions, is only thermodynamically favourable at elevated temperatures, and is affected by mass and heat transfer restrictions. At the required processing conditions, problems might also be experienced with sintering and with melting of slag forming components in the raw materials. A test programme was undertaken to study the effects of raw material type, temperature, gas composition, bed depth, carbon to raw material ratio and residence time in order to simulate conditions required for scaling up a nitriding process. In contrast to previous experience with low-grade titanium-bearing slag containing about 30% Ti02, ilmenite and chlorinateable slag do not form melting phases under the studied nitriding conditions and hardly sintered at all. Both feed materials can readily be nitrided with conversions in excess of 90% at temperatures around 1300°C and using bituminous coal as reducing agent with fixed carbon in excess of 1.1 times the stoichiometric requirement. The conversion decreases as the bed depth of the feed material increases and the N2/CO ratio in the gas decreases. Analysis of the relative rates of mass and heat transfer into the reacting beds of ilmenite and slag showed that the heat transfer rates are more limiting than the mass transfer rates. In order to increase the throughput that can be achieved in a kiln, it would be necessary to take special measures to enhance the heat transfer rates into the mass of reacting material. One such a measure is to pre-form the mass of reacting material into thin-walled, hollow brick shapes prior to introducing it into a kiln. Depending on bed depth, temperature and N2/CO ratio, required residence times in the high temperature zone of the kiln can vary between about 6 and 10 hours. Keywords Titanium dioxide, titanium nitride, carbo-thermic, reduction, ilmenite, slag, tunnel kiln, residence time.

Jan 1, 2011

By H. E. Bartlett

In the operation of some flotation plants treating platinum ores it was found that there were imbalances between the inputs and outputs. The inputs and outputs were sampled as slurries and it was determined that the imbalances arose from biases in the sampling, despite the samplers having been designed according to well-established rules. The launders feeding the sample cutters, and the sample cutters themselves were redesigned using finite element analysis to model the flows. A new set of design rules were formulated. The application of a Components of Variance Analysis, to determine the variance of primary and secondary sampling and of analysis in the lab for a concentrate is presented to illustrate the need for frequent sampling of process streams.

Jan 1, 2002

Abrasivity and wear resistance are not intrinsic properties of materials, but rather parameters describing the interaction between the wear part and the material exerting the wearing action. Moreover, wear or, at least, that part of the wear which is due to the cumulative effect of minute scratches, is linked to the hardness disparity concept. Abrasivity, in this context, is a relative concept, pertaining to a metal-rock pair, rather than to a rock. Based on this assumption, a methodology has been developed and checked against actual cases, enabling description of the abrasiveness of a rock or the abrasion resistance of a metal through the ratio of comparable quantitative indicators. The paper describes the methods and provides examples of applications to practical cases (namely: rock cutting, excavation by means of tunnel boring machines (TBMs), rock crushing, and hydro-mill cutting).

Jan 1, 2012

Mineral Resource Throughput Management is based on the extraction of the maximum potential value from an ore reserve with the emphasis to generate maximum ROI and ROR (return on reserve). A steel producing company in India implemented MRTM to significantly improve their ROI and ROR. The value chain of this company consists of their own iron ore and coal mines, ore washing plants, sinter plants, steel plants, and sales and marketing division. The target for the mines was to produce at a stable and predictable rate and at specific quality requirements. These requirements were set to improve productivity and ROI of the steel plant. The implementation constituted the alignment of the reserve potential, total production chain, human resources and management culture at the mines with the requirements of the steel plant. Many typical mining practices were challenged and changed. Production targets regarding lump vs. fines ratio, consistent product tons, quality targets such as Fe, Al content and moist, and standard deviation on the quality targets were not achieved. A reverse distribution model with release mechanisms to satisfy the demand were developed and implemented at the mines. A stable and predictable flow of mine product with quality standards well within the required standard deviation targets were achieved. The contribution from the mines to significantly improve the Net Profit, ROI and ROR of the company were reached.

Jan 1, 2007

A reliable laboratory method to characterize the response of free gold particles to flash flotation conditions has been developed. The test has been performed on free milling gold ores as well as synthetic ores, using either a gravity concentrate or gold powder as the gold source, to assess the floatability of gold particles. Trends in free gold flotation kinetics, as well as size and milling effects, were identified for gold recovery based on the different feed types, reagent dosages, and residence times. It was shown that the ultimate recoveries and kinetic trends of gold particles from the gravity concentrate could be enhanced with increased dosage of collector, potassium amyl xanthate. Interestingly, in comparison to gravity-recoverable gold, recovery from pure Au powders was better in collectorless flotation, and cumulative recovery decreased with higher levels of collector addition. Improved coarse particle recovery appeared linked to increased collector additions for both the gravity concentrate and the pure gold powders. In general, coarse gold particles demonstrated slower kinetic rates thaen the fine or intermediate components incomparable tests.

Jan 1, 2015

By J. P. F. Charpin

The transport of large boulders in a furrow from a mining area to a nearby pond was considered. The furrow is filled with a mixture of water and soil particles flowing down to the pond at high velocity. Due to operating constraints, the slope of the furrow is reduced progressively. A relationship is derived, relating the slope of the furrow and the composition of the fluid to the maximum size and shape of the transported boulders. The characteristics of the boulders carried all the way down to the pond may then be determined.

Jan 1, 2007

By R. Falcon, P. den Hoed, A. Luckos, R. Erasmus, V. du Cann, D. Comins

Carbon as a reductant, additive or filler is an essential element in the processing of metallic ores and the manufacture of iron and steel in the metallurgical industry. In most cases, the element carbon is derived from coal and its carbon derivatives. The properties of carbon required for the different processes in each metallurgical sector vary significantly and, for this reason, matching the correct carbon product for each specific process has become an important if not vital function in all sectors of this industry. This selection process, however, has become increasingly difficult. In many cases, the substitution of new products, despite being similar in all relevant chemical specification characteristics to previous products, has resulted in different performance properties relative to that expected. Under these circumstances, the prediction of performance of unknown carbon products has become fraught with difficulties unprecedented in the past. In order to initiate an investigation into addressing these issues, a test case was selected for indepth study the results of which are reported in this paper. The case concerned the use of a specific carbon feed in a conventional submerged arc furnace which gave rise to an unprecedented amount of unreacted or only partially consumed residue trapped in the frozen slag on the refractory walls of the furnace. During the course of these investigations, different advanced analytical technologies were employed including, inter alia, Raman spectroscopy, surface dimensional tests, organic petrology and various thermal reactivity factors. All results have been integrated into a multidisciplinary assessment presented in summary in this paper. Based on the above, and previous experience, the concept of an all-embracing 3-D coal-carbon ?framework? is briefly introduced. This approach has succeeded in obtaining greater depth of knowledge and a better understanding of the issues at stake with specific reference to the organic composition, structure, texture, internal surface area and consequent reactivity of the carbon materials concerned. In consequence, it would now appear that various properties of relevance to the metallurgical industry may be predicted with greater precision than has hitherto fore been possible.

Jan 1, 2004

By M. Mostert

Mining companies sponsor a range of non-core, corporate social responsibility projects to adhere to social and labour plans and environmental management prerequisites that form part of a mining licence application. Some companies go above and beyond such projects, sponsoring initiatives that generate renewable energy through solar power, wind energy, natural gas, etc. The challenge for these companies is to choose between a variety of projects to ensure maximum value, especially in times when the economic climate might be less favourable for such projects. The focus of this research was to analyse the concept of sustainability as it exists today, and to apply that to the triple bottom line accounting method in an attempt to quantify the sustainability of a project. Research was done on the methane burn-off project at Sibanye Gold?s Beatrix Mine to establish how such projects are planned and financed, and what impact they have on the triple bottom line of a company. The financial bottom line is, by definition, one that executives understand. This paper also proposes a quantitative method for defining the social and environmental bottom lines as well. By considering the financial, social, and environmental values, the study attempts to determine a monetary value for a sustainable renewable energy project. This monetary value can be compared to similar values obtained for other sustainable renewable energy projects under consideration. The research suggests that monetary value alone is not enough to base a sustainable decision on, and qualitative measures are suggested for use in conjunction with quantitative methods. The selection method proposed should assist the board of a mining company to choose the most sustainable option and the project that will add the greatest value to the company across all three bottom lines. It will also provide increased justification for such renewable energy projects, even in periods of harsh or uncertain economic climates.

Jan 1, 2014

Abrasivity and wear resistance are not intrinsic properties of materials, but rather parameters describing the interaction between the wear part and the material exerting the wearing action. Moreover, wear or, at least, that part of the wear which is due to the cumulative effect of minute scratches, is linked to the hardness disparity concept. Abrasivity, in this context, is a relative concept, pertaining to a metal-rock pair, rather than to a rock. Based on this assumption, a methodology has been developed and checked against actual cases, enabling description of the abrasiveness of arock or the abrasion resistance of a metal through the ratio of comparable quantitative indicators. The paper describes the methods and provides examples of applications to practical cases(namely: rock cutting, excavation by means of tunnel boring machines (TBMs), rock crushing, and hydro-mill cutting).

Jan 1, 2012

By P Papanastasiou, J Hadjigeorgiou, E Kyriakou

The south west area of Cyprus has a long history of slope instability problems. The location and extent of these landslides has been influenced by ground morphology, geological structure and the presence of weak rocks and cohesive soils. The main triggering mechanisms have been precipitation and/or seismic events. Landslides have contributed to the decision to relocate villages and considerable efforts have been put into maintaining the integrity of the local transportation network. This paper uses a recent case study of road embankment failure near Pentalia in southwest Cyprus to review the available tools for the analysis of slope instability. It further demonstrates how the shear strength reduction technique can be used in a finite element analysis to better visualise the slope instability mechanism of a road embankment and provide a reliable tool in selecting appropriate remedial measures.

Jan 1, 2006

By A. C. Legg, M. T. Malema

Keywords: Pyrometallurgy, flash, smelting, furnace, nickel, copper, Botswana BCL Limited operates the only Flash Smelting Furnace on the African continent, at Selebi-Phikwe, situated in north-eastern Botswana. The furnace was commissioned in 1973 and produces a high-grade sulphide matte containing nickel, copper and cobalt, which is shipped to refineries in Zimbabwe and Norway for further processing. This paper outlines the recent process improvements and plant expansions that have resulted in a capacity increase from 40 000 to 60 000 tons per annum of metal production.

Jan 1, 2006

By S. Thorley

In engineering design of operator?s compartments, in underground mining equipment, ergonomics principles are often neglected or not given the full recognition they deserve. This paper defines ergonomics, applies it to machinery in an underground mining environment and describes the ergonomics analysis undertaken during the design phase of an EJC extra-low-profile mining loader. Encompassing the design of the operator?s compartment of this new loader, this paper illustrates the importance of ergonomics principles within the collective design process, ensuring that it is fully integrated into the design approach. An ultimate aim of this study is to ensure that all future designs follow this route to guarantee not only the outcome of a highly efficient, cost-effective and productive machine but that it is also takes the human factor into account, not only in maintenance but also in operation. Maximizing comfort will have the ultimate outcome of actually increasing productivity.

Jan 1, 2006

This paper characterizes the copper cycle, that is, the flows of copper entering and leaving the African economy over a one-year period (1994). The major flows over the entire life-cycle of copper are examined; these include production (mining, milling and refining), fabrication of semi-products and manufacturing of finished products, use, and the waste management system. The results reveal that substantial amounts of copper (of order705 Gg/yr) are mined in Africa; of that amount, about 70 per cent is exported following processing, 18 per cent is utilized by African fabricators, and 12 per cent is discarded. The flows of copper products from African fabricators and product imports from other continents exceed product discards by large amounts. This difference, about 0.25 kg Cu/capita/yr on average, is added to in-use stock, largely as wire, plumbing tube, and in electronics. Some 65 per cent of the copper in discard flows is contained in electrical and electronic products, where it is relatively easy to collect and process for reuse. About a third of the copper discard flows known is recycled. The actual percentage is almost certainly higher because of informal (and unrecorded) recycling. Much of the remaining discarded copper is diluted into the municipal waste stream, where recovery and recycling are probably not economically justified. Keywords: material flow analysis, resource management, material budgets, copper, stocks and flows, systems analysis, Africa, developing country

Jan 1, 2003

By Q. G. Reynolds

The presence of dust and fume suspended in the freeboard region is a common feature of the operation of direct current (DC) plasma smelting furnaces. This occurs primarily as a result of the use of fine feed materials together with the open-arc, open-bath operation of such smelters, and is exacerbated by the high velocities and turbulent mixing of the gas in the vicinity of the arc jet. Dust and fume losses into the furnace off-gas system can be significant in some cases and may have economic, operational, and environmental impacts on the process. A computational modelling study is presented in which the concentration of dust material was considered as a continuous field subject to a governing partial differential equation. Settling behaviour was calculated as a function of particle size, local gas/plasma temperature, and other physical properties. Development of the coupling between the concentration field and a magnetohydrodynamic description of the arc is shown, and the resulting models were used to compute various aspects of the behaviour of the concentration field in the arc region for a variety of furnace conditions. Time-averaged as well as transient models of the arc were used to generate the results presented. Qualitative case studies produced several practical suggestions for furnace operation, including increased dust capture by the bath when feed ports are located closer to the electrode, and the possible effects of feed segregation in the furnace freeboard based on dust particle size and density.

Jan 1, 2015

By M. du Plessis, D. F. Malan

"The aim of any mine design is to ensure that the excavations remain stable for the period they will be in use. Various pillar systems are used to ensure that underground stopes remain stable and that mining activities do not affect the surface infrastructure through either surface subsidence or seismicity. Intermediate-depth platinum mines make use of in-stope pillars designed to fail while the pillars are being cut at the mining face. The pillar stress exceeds the loading capacity and the pillars crush as a result. The aim of the paper is to provide an overview of in-stope crush pillars. This will include the application, behaviour, function, mechanism, impact, and design of a crush pillar system."

Jan 1, 2015

By F. M. C. C. Vieira

Four mining alternatives for exploiting an ultra-deep orebody were assessed through a multidisciplinary evaluation process which involved: the generation of a 3D geological model; the design and scheduling of life-of-mine layouts; the analysis of anticipated ventilation and cooling conditions; the study of rock-related risks of mining in ultra-deep stress environments; the logistic implications of transporting men, rock and materials; and, lastly, the economic implications of each option. Once results from the integrated mine design assessment were available, mine planners were faced with an important problem to solve: how to identify the optimal mine design alternative when numerous assessment measures and multiple decision criteria needed to be considered simultaneously? To address this ‘multiple-attribute decision problem’ and arrive at the ‘optimal layout for ultra-depth’, a generic decision methodology that uses principles of ‘utility’ was applied. The methodology assumes that ‘single-value risk estimators’ do not account for the inherent variability of real conditions. Therefore, risk estimators were represented by statistical distributions of their incremental changes, where applicable. The stochastic variables, once defined, are used as inputs in the ‘utility’-based layout decision scheme. This ‘utility’-based decision methodology offers a framework for mine design decisions to be made objectively, when complex trade-offs between multiple risk domains need to be considered simultaneously. Upon applying it, one of the layouts emerged as the preferred alternative. Keywords: Utility; mine design; multiple-attribute decision; layout selection

Jan 1, 2003

By E. S. Peters, M. J. van Rensburg, M. Le Roux, Q. P. Campbell

"The demand for energy has continued to rise worldwide in line with population growth. The majority of South Africa’s electricity is supplied by coal-fired power stations. The amount of fine coal (-2 mm) generated at coal processing plants has increased, due mainly to mechanized mining methods. Fine coal retains more water, which lowers its heating value.Drying the coal is costly and it is difficult to achieve the required moisture content. Consequently, coal fines are often discarded. An estimated 8% of the total energy value of mined coal is lost1.Fluidized bed technology is often used to dry coal thermally, but this method is expensive and has an adverse environmental impact. The objective of this study was to investigate the removal of moisture from fine coal (<2 mm) in a fluidized bed operated with dry fluidizing air at moderate temperatures as the drying agent. The effects of different air temperatures and relative humidity levels were investigated in a controlled environment. The study further investigated the influence of coal particle size on moisture removal.The drying rate was found to increase with increasing temperature. The relative humidity of the drying air had a more pronounced effect on the drying rate, even at temperatures as low as 25°C.. It became more challenging to remove moisture as the particle size decreased. The gain in calorific value was greater than the energy required to dry the coal samples, showing that a fluidized bed using moderately warm dry air is an energy-efficient drying technology. The energy efficiency of the fluidized bed compared favourably with other thermal drying methods.Paper written on project work carried out in partial fulfilment of Degree in Chemical Engineering(NWU) - Pursuing Masters in Coal Beneficiation"

Jan 1, 2015

By F. T. Cawood

The distinction between real estate ownership and that of interests in the property is fundamental to the appraisal of mineral properties. This distinction affects the nature and understanding of security of tenure and, consequently, the perception of what constitutes fair value. Legal matters are a particular concern because of their influence on security of tenure, ownership definition and use restrictions. The dynamics of the market and the complex interrelationships between the factors of production define value at a specific point in time for the bundle of rights, interests and assets that constitute a mineral property. Because each mineral property is unique, physically immobile and of a wasting nature, its usefulness to its owner and society must be optimized. The US Appraisal Institute (2001) classified the forces that affect land use as the cultural, political and economic attitudes of society. These forces culminate in laws that often dictate the purposes for doing appraisals. Once the legal definition of the asset is understood, valuers can decide on the valuation process that will support the final valuation approach.

Jan 1, 2004

By Rajendra Singh

Underground depillaring of contiguous coal seams/sections is a difficult problem, which becomes even more complex if the interburden/parting between them is thin. Conventionally, the depillaring with caving of contiguous seams/sections is done in descending order. However, if the parting is thin, the influence of the top sections/seams working over the standing pillars of bottom the sections/seams becomes extremely important for the safety and optimal exploitation of coal. Field investigations were carried out at Nowrozabad East mine where superimposed pillars of the Johilla top section were depillared above the developed pillars of the Johilla bottom section with a 3 m thick parting between the two sections. The competency of the 3 m thick parting (which consists of alternate layers of shale, sandstone and shaly sandstone) was improved by reinforcement (underpinning). The strata control investigations did not show any considerable instability problem of the 3 m thick reinforced parting and pillars of the bottom section due to top section depillaring. On the basis of this field investigation and a laboratory study on simulated models, simultaneous extraction of both the sections, along with reinforcement of the parting, was suggested for the geomining conditions of the Johilla top and bottom sections. Adopting the suggested simultaneous depillaring process, two sub panels of Johilla top and bottom sections have successfully been extracted without any strata control problem. This paper presents this case study along with the results of the strata monitoring conducted to evaluate performance of the underground structures during the field trial.

Jan 1, 2004

By E. Ringdalen

Keywords: Pyrometallurgy, research, Norway, SINTEF, NTNU The Norwegian Ferro-alloy Industry and the model for research cooperation between SINTEF, NTNU, and the Norwegian ferro-alloy industry is presented as an introduction. The research within pyrometallurgy is illustrated by examples from characterisation of Mn-ores and characterisation of carbon materials. Examples from studies of reaction mechanisms in laboratory- and pilot-scale experiments are presented, in addition to an example of industrial off-gas measurements. Education possibilities at NTNU are also described.

Jan 1, 2011