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By L. Mpolokeng, J. P. Labuschagne, H. Yilmaz

"An investigation into pillar cutting was carried out at a platinum mine on the western limb of the Bushveld Complex. The focus was on crush pillar design and implementation in order to ultimately improve the compliance percentage for pillar cutting. The major findings from the investigation suggest that the pillar cutting problem lies with the implementation of the design rather than the design itself. Observations of the practical issues underground that prevent good pillar cutting were made. After these issues had been identified, recommendations to rectify these problems and a few other issues identified during the investigation were provided. The recommendations are aimed at improving the pillar cutting compliance and reducing the likelihood of pillar bursts or pillar runs, which will ultimately create a safer mining environment. Paper written on project work carried out in partial fulfilment of BSc. Eng. (Mining Engineering)"

Jan 1, 2015

By C. Hutton

"SynopsisThe last commodities supercycle (2003 to 2011) was characterized by a belief in volume at any cost, where absolute output was deliberately prioritized over productivity considerations. This practice fuelled overoptimistic forecasting and planning, which in turn contributed to the economic crisis that followed. The sudden collapse of commodity prices has resulted in mining companies scrambling to find the right balance between optimizing current operations and preserving sufficient flexibility to grasp future opportunities. The runaway costs of building and operating mines have almost squeezed out profit margins, while lower ore grades are inflating production costs. Mining companies therefore need to look at the business with fresh eyes, and develop strategies to attract equity capital as traditional approaches are simply not working anymore. This is especially so in the context of a dwindling investor base that continues to demand greater returns, despite a significantly lower appetite for risk. This paper revisits the micro-economic concepts and demonstrates how pressure from shareholders to prioritize output contributed to spiralling costs and value destruction. Practical techniques are described to model cost curves to optimize a Mineral Resource endowment and address the need to rightbalance a business and preserve agility.IntroductionHenry Lazenby (2014) for the Mining Weekly writes, ‘Bruised and battered, the global mining industry today is undergoing a sea change. Practices and policies that might have worked wonders in the past are not as relevant today, and new approaches to running profitable mining operations need to be found.’ One significant practice the mining industry had during the last commodities supercycle (2003 to 2011) was chasing volume at any cost; absolute output was deliberately prioritized over productivity considerations (Goldsmith, 2013). Lazenby contends that in the face of falling and volatile commodity prices, many mining majors ‘across all commodity groups are currently grappling with sagging profits and low company valuations. This is often regarded as the result of the were in pursuit of growing their output at all costs in a high commodity price environment.’ Lee Hodgkinson, KPMG’s Canadian mining industry leader and quoted by Lazenby, says that ‘mining companies are now trying to find the right balance between optimizing current operations and preserving their agility to grasp future opportunities. The runaway costs of building and operating mines have almost squeezed out profit margins [whilst] lower grades of ore are inflating production costs. Mining companies need to look at the business with fresh eyes, and develop strategies to attract equity capital as it seems clear that some of the traditional approaches to the mining business are simply not working anymore."

Jan 1, 2015

By C. L. Reichardt

Mining companies are increasingly looking to the developing world for the next generation of mining projects, often in countries that have little or no previous history of large-scale mining. One of the major challenges for such projects is hiring?and retaining?personnel that have technical skills and experience in mining-related disciplines. Staffing a mine with an expatriate workforce is neither cost-effective nor sustainable, and many countries now insist that mining companies ?transform? the profile of their workforce to more closely mirror the demographic profile of the host population. The need to nurture mining-related skills in emerging mining nations is not solely limited to the workforce: there are also pressing economic and sustainability imperatives to develop capacity within local service providers such as consultants and contractors, as well as to facilitate informed engagement between mining companies, government and civil society. However, few educational institutions in emerging mining nations currently have the ability to offer practical training in mining-related disciplines. Local employees who are sponsored by companies to develop their skills through international study maybe impeded by language and cultural barriers, and may also be taught using course content that is of limited relevance to the specific challenges of their future working environment. This paper addresses the challenge of skills development and retention in emerging mining nations and uses examples from sub-Saharan Africa and the Asia Pacific region to explore practical means of developing capacity in mining-related disciplines. It examines the need for companies to implement strategies to develop local technical capacity in countries where they envisage a long-term operational future and also highlights the need to foster partnerships between academia, developmental institutions, mining companies, governments and civil society to establish the critical mass of mining-related skills required to nurture the development of a sustainable mining industry.

Jan 1, 2009

By G. A. Kordosky

The concept of selectively extracting copper from a low-grade dump leach solution followed by stripping the copper into an acid solution from which electrowon copper cathodes could be produced occurred to the Minerals Group of General Mills in the early 1960s.This simple, elegant idea has resulted in a technology by which about 2.2 million tonnes of high quality copper cathode was produced in year 2000. The growth of this technology is traced overtime with a discussion of the key plants, the key people and the important advances in leaching, plant design, reagents and electrowinning that have contributed to the growth of this technology. Some thoughts on potential further advances in the technology are also given.

Jan 1, 2002

By M. Hooman, W. M. Marx, R. C. W. Webber-Youngman

This paper discusses a study that investigated different underground bulk air heat exchanger (>100 m3/s) design criteria. A literature review found that no single document exists covering all design criteria for different heat exchangers, and therefore the need was identified to generate a guideline with decision analyser steps to arrive at a technical specification. The study investigated the factors influencing heat exchanger designs (spray chambers, towers, and indirect-contact heat exchangers) and the technical requirements for each. The decision analysers can be used to generate optimized, user-friendly fit-for-purpose designs for bulk air heat exchangers (air cooler and heat rejection). The study was tested against a constructed air cooler and heat rejection unit at a copper mine1. It was concluded that the decision analysers were used successfully. This tool (decision analysers) can be used by engineers for the efficient and cost-effectively design of heat exchangers.

Jan 1, 2015

One of the seminal pioneering papers in reserve evaluation was published by Danie Krige in 1951. In that paper he introduced the concept of regression techniques in providing better estimates for stope grades and correcting for what later became known as the ‘conditional bias’. In South Africa, the development of this approach led to the phenomenon being dubbed the ‘regression effect’, and regression techniques ultimately formed the basis of simple kriging in Krige’s later papers. In the late 1950s and early 1960s, Georges Matheron (1965) formulated the general theory of ‘regionalized variables’ and included copious discussion on what he termed the ‘volume-variance’ effect. Matheron defined mathematically the reason for, and quantification of, the difference in variability between estimated values and the actual unknown values. In 1983, this author published a paper that combined these two philosophies so that the ‘regression effect’ could be quantified before actual mining block values were available. In 1996 and in some earlier presentations, Krige revisited the regression effect in terms of the conditional bias and suggested two measures that might enable a practitioner of geostatistics to assess the ‘efficiency’ of the kriging estimator in any particular case. In this article, we revisit the trail from ‘regression effect’ to ‘kriging efficiency’ in conceptual terms and endeavour to explain exactly what is measured by these parameters and how to use (or abuse) them in practical cases.

Jan 1, 2015

By A. Vorster

The objective with mine planning is to consistently deliver production conforming to quality and quantity requirements throughout the life of the mine. The complexity of the operational context of the modern mine extends far beyond the actual production actions and there is a need to find ways of analysing and managing this extended environment. A well-established approach to handling complex situations rely on the creation of representative models that use classification and visualization strategies. An example of the use of a classification scheme is the periodic table of the elements. All physical matter can be expressed as combinations of basic elements. Not only is the periodic table useful in classifying and identifying matter but it can also be used for the prediction of the properties of unknown matter and compositions of elements.

Jan 1, 2001

By J. C. Vreugdenburg, B. A. Dippenaar, J. Muller, T. L. de Vries

Iron ore fines are agglomerated to produce sinter, which is an important feed material for blast furnaces worldwide. A model of the iron ore sintering process has been developed with the objective of being representative of the sinter pot test, the standard laboratory process in which the behaviour of specific sinter feed mixtures is evaluated. The model aims to predict sinter quality, including chemical quality and physical strength, as well as key sinter process performance parameters such as production rate and fuel consumption rate. The model uses the finite difference method (FDM) to solve heat and mass distributions within the sinter pot over the height and time dimensions. This model can further be used for establishing empirical relationships between modelled parameters and measured sinter properties. Inputs into the model include the feed material physical properties, chemical compositions, and boundary conditions. Submodels describe relationships between applied pressure differential and gas flow rate through the bed of granulated fine ore particles, combustion of carbonaceous material, calcination of fluxes, evaporation and condensation of water, and melting and solidification. The model was applied to typical sinter test conditions to illustrate the results predicted, and to test sensitivities to parameters such as feed void fraction, feed coke percentage, and the fraction of combustion heat transferred to the gas phase. A model validation and improvement study should follow, ensuring sinter test results are free from experimental errors by conducting repeated tests.

Jan 1, 2015

By M. B. Shongwe

Pt-based alloys are being developed for high-temperature applications with the aim of replacing some of the currently used Ni-based superalloys (NBSAs) in the highest temperature applications. The Pt-based alloys have a similar structure to the NBSAs, and since Pt is more chemically inert than nickel and has a higher melting point, they can potentially be used at higher temperatures, up to 1300°C, and in more aggressive environments. Several experimental Pt-based alloys were studied at Mintek, and an optimum composition was found to be Pt84:Ahi:Ru2:Cr3 (at.%). On the basis of hardness and microstructure, a later study identified a new optimum: Ptr8:A111:Ru5:Cr6 (at.%). There are at least two Pt3A1 allotropes, and the high-temperature cubic structure has better properties than the lower temperature tetragonal form, and so needs to be stabilized. This work describes the latest results obtained in transmission electron microscopy (TEM) studies of the quaternary Pt-based superalloys. These results are both interesting and important, because the samples have a higher precipitate density compared to those from earlier work. The precipitate morphology is mainly cubic, with minor areas having irregular-shaped precipitates. The high volume fraction of the precipitates is a major breakthrough, since the objective of this work is to improve the alloys. A prior disadvantage was that the proportion of the precipitates was too low in samples before this work, especially compared with the work from Germany on Pt-Al-Cr-Ni¬-based alloys as well as the NBSAs. TEM -Pt3A1 diffraction patterns were studied, and for each diffraction pattern, many possible lattice point combinations were tried, with the angle between the lattice spots as well as interplanar spacings being calculated for each phase (cubic or tetragonal) to match the measured results. An overall analysis of the diffraction results indicates that the cubic phase fitted the experimental lattice points with much lower errors compared to the tetragonal phase. Thus, with the close match achieved with the cubic structure, the structure of -Pt3A1 precipitates is likely to be cubic. X-ray diffraction has been carried out on selected samples, and the results confirmed the presence of cubic -Pt3A1 and (Pt). Different X¬ray diffractometers were used to further verify the results, and the results were also compared with those from TEM.

Jan 1, 2012

A typical sub-level block cave mining extraction method employs an undercut level to establish a cavity in hard rock, and as such requires special support methods and products to be installed during the development phase. The undercut level development in the block cave orebody is then sacrificial, and support elements will eventually report to the crusher and perhaps conveyor belt systems for transportation to surface. The choice of support products installed in the undercut level development should take cognizance of the detrimental effect these could have on the mining system such as cutting of conveyor belts, obstructing crushers, safety aspects, and productivity. This work explores the probability and practicality of making use of new-generation support products to make the operation safer as well as enhance productivity in the development phase and during the undercut operation. This paper will investigate the use of glass reinforced plastic(GRP) rockbolts and GRP mesh instead of conventional steel bolts and mesh along with resin capsule-filled holes with the GRP bolts. Complementing this with thin spray liner (TSL) application as another means of creating a safer operating environment, as well as a productive support medium, will also be addressed. These proposed items are envisaged to reduce production downtime and improve the safety of our people. These items are all easy and light to handle, cuttable and crusher friendly, as they will break up during the crushing process.

Jan 1, 2012

By P. I. Page

In mineral exploration the place that yields the first significant result is marked and two questions are posed immediately. Where should the next sample be drawn and how big should it be? At present the answers are arbitrary and ad hoc. They depend on personal experience and sentiment?that is hunch. The thought processes involved in reaching the decisions are unsatisfactory and unsatisfying for professionals. This paper proposes guidance on choosing sample spacing and sample size. The guidance is obtained from the grades of the samples. The grades also imply the extent of influence of each sample assay. Thus sampling and assay are integrated. The integration is achieved by changing the unit of value in which assays and grades are expressed and by exposing meanings and functions of grade beyond that of measuring rock value. The proposals are extended to guide comminution of particle size in sample size reduction and to deal with the problem of erratic high assays. Also, elucidation becomes possible of the computation of a reliable figure for average grade as a statistical weighted mean.

Jan 1, 2005

By Ron Tluczek

[Power Point Presentation]

Jan 1, 2006

By Ö. Erdem

The investment decision making process in the insurance and finance industries is affected by new advances such as simulation techniques. These advances have improved the discounted cash flow method (DCF). In DCF, a dynamic and flexible model construction is not possible because it does not consider uncertain conditions. Each project should be evaluated taking into account the related uncertainties because the related uncertainties determine the characterization of the project. Related uncertainties can be processed in dynamic DCF, which is applicable to both financial and non-financial industries with different kind of uncertainties, such as power generation and petroleum projects. The dynamic DCF method can estimate net present value (NPV) while managing related project uncertainties with a simulation method like Monte Carlo Simulation. The simulation method is preferred because its output is unbiased. Therefore, a more realistic financial evaluation of the project can be concluded. In spite of the improvement of dynamic DCF, this project evaluation method is not used frequently in mining industry. However, the mining industry is ideally suited to this concept because it is highly dependent on estimations such as orebody size and ore grade. During the project evaluation stage, these uncertainties can be included with the dynamic DCF method. This study aims to contribute to increasing the usage of this method in mining projects. A copper reserve in Turkey is selected as a case study to apply uncertainty assessment for the evaluation of NPV.

Jan 1, 2012

By V. Pawlowsky-Glahn, E. Pardo-Igúzquiza, J. J. Egozcue, R. A. Olea

Compositional data constitutes a special class of quantitative measurements involving parts of a whole. The sample space has an algebraic-geometric structure different from that of real-valued data. A subcomposition is a subset of all possible parts. When compositional data values include geographical locations, they are also regionalized variables. In the Earth sciences, geochemical analyses are a common form of regionalized compositional data. Ordinarily, there are measurements only at data locations. Geostatistics has proven to be the standard for spatial estimation of regionalized variables but, in general, the compositional character of the geochemical data has been ignored. This paper presents in detail an application of cokriging for the modelling of compositional data using a method that is consistent with the compositional character of the data. The uncertainty is evaluated by a Monte Carlo procedure. The method is illustrated for the contents of arsenic and iron in groundwaters in Bangladesh, which have the peculiarity of being measured in milligrams per litre, units for which the sum of all parts does not add to a constant. Practical results include maps of estimates of the geochemical elements in the original concentration units, as well as measures of uncertainty, such as the probability that the concentration may exceed a given threshold. Results indicate that probabilities of exceedance in previous studies of the same data are too low.

Jan 1, 2015

By J. Madias, E. Benavidez, E. Brandaleze, L. Castella

Knowledge of the physical and chemical properties as well as the behaviour of the mould fluxes during melting, important in order to improve continuous casting operations. Lubrication and control of heat transfer in the mould are the more relevant functions of these materials. Values of physical properties like viscosity and surface tension at melting range temperatures are required, as much as the thermal behaviour under process conditions. The heat extraction from the liquid steel has an important effect in the final quality of products. Mould fluxes are constituted by different oxides, and may form glasses and crystal phases during cooling. The solidification rate and the chemical composition determine the proportion, type and crystalline morphology, which are responsible of the thermal transfer processes. In this paper, viscosity values are reported in the melting range temperatures calculated by means of the Riboud model and compared with fluidity results obtained by the inclined plane technique. Also the linear expansion of the mould fluxes at high temperatures was determined by dilatometry. The crystallization in two different fluxes was determined by DTA tests and correlated with the basicity index. Crystal phases were evaluated by scanning electronic microscopy on quenched samples at 1300°C. This information is relevant to increase the knowledge on the peritectic steel grades casting process in order to improve its quality. Keywords: mould fluxes, heat transfer, crystal phases, peritectic steels, thermal properties.

Jan 1, 2004

By J. Kortnik

Mining has always been, and still is, an activity which is vital for the development of mankind. This is because a predominant proportion of industrial products and energy is produced from raw materials that are excavated using mining methods. The need for environmental protection and the close proximity of urban settlements and mines in Slovenia have necessitated ever stricter requirements for the excavation of raw materials and introduction of more environmentally-friendly mining methods. This is achieved by implementing a closed eco-technological cycle of raw material excavation within the scope of mining methods. In surface mines, this means prompt reclamation of the degraded surfaces, and in underground mines the use of methods with minimized impact on the surface and on underground water. In underground mines, mining methods with backfilling installed according to the multi-barrier disposal system are the only ones that allow the possibility of implementing a closed eco-technological cycle of excavating raw materials. Various industrial waste materials are also included in the backfilling material in order to improve its strength properties. Backfilling consisting of several different waste materials is produced in the form of a composite. Before backfilling consisting of waste material composites can even begin to be used in mines, an environmental impact assessment of its suitability for mines needs to be made. In order to make such an assessment, a pressure leaching cell and an open diffusion cell were made, i.e. a pressure leachate test and a sorption test were developed. The two cells and the developed tests will enable the study of the influence of backfilling on the environment if installed in an underground mine. The pressure leachate test performed with the use of the pressure leaching cell simulates leaching from a consolidated backfill during the seeping of underground water into the backfilling material under pressure. The sorption test performed in an open diffusion cell simulates the flow of eluate leached from the backfilling material through the rock/geotechnical barrier. The two tests were developed in such a manner that they are performed either in succession immediately after one another, but they can also be performed separately at a certain time interval. The paper presents an assessment of the suitability of backfilling made of different waste material composites. Keywords: environmental impact assessment, multi-barrier disposal system, waste material composites, pressure leachate test, sorption test, pressure leaching cell, open diffusion cell, eco-technological cycle, mining methods with backfilling.

Jan 1, 2003

By L. Holappa

Ferroalloy production is an energy-intensive industrial sector with significant CO2 emissions. In this paper the current situation in ferroalloy processes is discussed from the standpoint of global environmental issues, trends and development. Progress and data of ferroalloys production are frequently compared with the steel industry, which is a closely related sector and the main user of ferroalloys. Emission factors of processes and electricity production are examined as well as possibilities and future scenarios of how to diminish CO2 emissions. As a part of this study a questionnaire was submitted to experts in the field of ferroalloys worldwide to survey opinions on the ferroalloy industry today and in the near future (2020). Eighteen questions concerning raw materials, energy, environmental aspects, by-products and economic aspects were responded to by seventeen experts, the answers were analysed and conclusions were drawn. Keywords Ferroalloys, energy, CO2 emissions, electricity, sustainability, questionnaire.

Jan 1, 2010

By C. J. Badenhorst

The scope of this project was to research, develop and eventually produce a personal occupational hygiene and safety exposure monitor system to assist in recording and analysing various stress factors that could affect the health, wellness and safety of employees, i.e. that could result in injury or ill health of workers, create stress build-up within individual workers that could negatively affect worker alertness and safety, and, may even result in permanent disability or death. Utilized systems at the time were all reactive, whereas the DOHEMS (Proactive Digital Occupational Hygiene and Safety Exposure Monitoring) System enabled the measurement of exposure (and associated risk) in a proactive manner via real-time exposure and digitized recordings. The idea of the development was to create a unit that is so cost effective, small and light that every worker can use a system on a daily basis. The development will eventually replace current, bulky and expensive monitoring equipment. The device must be a portable battery operated device and monitor the immediate working environment by periodic sampling for vibration, noise, toxic gasses (NO/NOX/CO/VOC, etc.), body temperature and heart rate. The samples must be time and date stamped, utilizing a real-time clock (RTC) synchronized with the closest regional secondary time source and related to synchronized real-time video captured samples. These samples are then recorded onto a rugged non volatile storage device with the capacity to store a vast number of samples covering the entire working shift of eight (8) hours plus. The system has been fitted with a clear visual local alarm indication system, indicating any excessive exposures or stresses, for the worker?s supervisor to respond to. This system allows for a pro-active approach. The system is also a wireless system (to the external environment) so as to not affect the mobility of an employee and flameproof to allow for use in explosive environments. Keywords: safety, digital, exposure, monitoring, proactive.

Jan 1, 2010

One of the most important factors leading to the success of a cement plant is its location. A multicriteria decision-making method is used to rank alternative plant locations. The set of criteria is established and corresponding criteria should be established for each case study, although this multicriteria decision-making approach has broader applicability. In this paper, the analytic hierarchy process (AHP) with 5 criteria is used to develop a location evaluation hierarchy for an alumina?cement plant in East Azerbaijan province of Iran. Five alternatives for the plant location are evaluated. The main criteria are transportation, water supply, power supply, fuel supply and land. Other criteria have the same importance as these five alternatives. The alternatives are ranked by a multicriteria method and the best site is proposed. Keywords: plant location; multicriteria decision-making

Jan 1, 2005

By N. Reddy

The influence of local geology and rock mass characteristics on deformations during a rockburst caused by a controlled blast was studied. This was done by means of visual examination, mapping and photography both before and after the blast. We found that the ejected material was bounded mostly by fractures associated with the bow-wave fracturing and bedding surfaces and that existed prior to the blast. Most of the damage was caused by shake-out. This information is important input for the design of rockburst resistant support systems under conditions of moderate stress.

Jan 1, 2001