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The influence of Harold Hotelling?s work in the field of mineral economics is both unusual and outstanding. In the 66 years since its development, theory surrounding the economics of exhaustible resources has only been significantly researched since the early 1970s. At that time a wave of research into the economics of exhaustible resources arose from the threat of global resource scarcity and continued into the late 1990s. Current East Asian and global demand for natural resources as well as mineral and metal commodities, has stimulated interest in the optimal and sustainable exploitation of exhaustible resources to the point that the subject is worthy of review. Hotelling?s theory and the assumptions that he made in establishing a model for the optimal exploitation of mineral resources at the industry level and at the level of the individual mine owner, are examined. He showed that the rate of increase inexhaustible resource prices should be equivalent to the market rate of interest and that in a market with rising prices the rate of extraction should be constant. In markets where demand is stable optimal exploitation requires that the rate of extraction should decline over time, while in a monopoly market he showed that the rate of extraction is retarded. In addition, the effects of cumulative production on costs and prices, the uncertainty associated with estimates of the resource stock, the impact of exploration and issues of intergenerational equity are examined. An analysis of the optimal price path, extraction costs and mineral rents at an industry level is presented as a model. An analysis of the rates of production and optimal benefits at the individual mine level including total, average and marginal costs on the optimal rate of production, is considered. Optimal extraction rates for a mine with a clearly defined concave positive cost equation vary according to the position on the marginal cost curve. The influence of discount rates and the size of the ore reserves on the rates of mineral extraction are also examined and could define the frontier of usefulness for the ?economics of exhaustible resources?.

Jan 1, 2007

By D. Farrow

Future development of kimberlite mines is now focused on mining at deeper levels. The consequences are increased difficulty and costs of the mining operations. The decisions on investments require accurate resource evaluation and quantification of the risk. In the decision process the first step consists in choosing the number of boreholes sampling the pipe relative to the level of uncertainty that can be accepted. The uncertainty in the volumes of rocks of different types can be assessed as soon as we can estimate these volumes from a given borehole layout and calculate the error by means of its variance for instance. In theory this can be achieved by using geostatistical techniques (‘transitive theory’), but in practice the calculation of the error on volumes can be achieved in very particular cases, assuming some regular sampling patterns. A different approach has been chosen based on simulations, giving maximum flexibility to reproduce the reality of the sampling procedure. The idea is to simulate the geometry of several ‘possible’ pipes with their internal geology and estimate them by kriging. Several experimental errors are obtained on which risk analysis can be performed. The aim is to find a feasible method to perform the simulations with reasonable chance to correctly represent the reality, without data on the pipe extension. The methodology applied is based on some hypotheses that can be assessed by the geologist as well as by the geostatistician. The procedure assumes a geological model based on current knowledge including appropriate geostatistical variation. What make these simulations specific and powerful in this case comes from the fact that the boundaries between the different rock-types can be simulated using a transformation of the real 3D space into a 2D space defined by means of polar coordinates. Ultimate transformations to account for smoother variations with morphological transformations allow the generation of realistic pipe geometries on which sampling pattern can be used to evaluate the estimation errors. By estimating the simulated pipe geometries with different boreholes layouts a risk curve expressing the uncertainty in the volumes of the different rock-types versus the number of holes can be developed.

Jan 1, 2003

By L. Gunnewiek

An advanced real-time monitoring system called the tapblock diagnostic system (TDS) has been developed. The purpose of the TDS is to help furnace operators manage the safe operation and economical maintenance of furnace tapblocks. This system is an evolution of the current practice of using historical records and operator interpretation to assess the ?health? of a tapblock. The main parameters affecting tapblock health are heat removal capacity and refractory wear, and these are currently difficult to assess in situ except in a global way. By using monitored and operating data together with predictive numerical modelling and multivariate statistical methods, real-time tapblock performance is assessed relative to expected performance. A state indicator in the form of a green, yellow, and red light is used by furnace operators to monitor the tapblock performance and health status during operation. Access to historical operating data and the provision of diagnostic functions allow for probable health degradation events to be deeply investigated. A recent opportunity to evaluate the actual performance of a first generation TDS installed in the KIVCET furnace at Teck Cominco?s Trail Operations showed that a reasonable estimate of tapblock health was made. However, the evaluation also found that some areas of refractory wear were missed, and a new mechanism affecting refractory wear was discovered that was not previously known. This has reinforced the belief that there is a need to develop improved methods of monitoring so that data used to define the health of the tapblock is more comprehensive and accurate.

Jan 1, 2008

By T. Feroze, B. Genc

"The ventilation of underground coal mines plays an important role in minimizing the risk of methane and coal dust explosions. The ability of ventilation, with the use of line brattices (LBs), to remove methane and coal dust in empty headings is dependent on the amount of air leaving the LB and entering the heading. The quantity of this air depends on the associated system variables, namely heading dimensions, settings of the LB, and velocity of air in the last through road (LTR). However, the exact effect of these system variables on the flow rate at the exit of the LB in an empty heading is not known. The installation of LBs in South African coal mines is generally carried out based on experience. This can result in overor under-ventilation and may increase the cost of providing ventilation or cause accidents, respectively. In this paper, using computational fluid dynamics (CFD), the air flow rate at the exit of the LB in an empty heading was estimated using full-scale three-dimensional models. The CFD model used was validated using experimental results Firstly, the settings of these three system variables were varied, the flow rates at the exit of the LB were measured, and finally the results were used to calculate the effect of each system variable. The outcome is a mathematical formula that can be used to estimate air flow rate at the exit of the LB in empty headings for any practical scenario.This paper will help the coal mining sector in South Africa by providing estimation models based on scientific reasoning for the installation of LBs, and will also serve academia as part of the curriculum towards educating future mining engineers."

Jan 1, 2016

By Z. Halifa, P. G. Geyer

Tapping a blast furnace is necessary not only to deliver the product, but is also essential for the safety of the furnace and workers in the cast-house. This paper will highlight the practices at ArcelorMittal’s blast furnaces in the Vanderbijlpark Works, with specific focus on tap-hole design and monitoring as well as casting practice. Extension of the tap-hole life and hearth campaign will be illustrated with reference to the methods of maintenance of the tap-holes, troughs, runners, and cast-house equipment. The importance of proper cooling, good thermocouple installation, and temperature monitoring will be explained.

Jan 1, 2014

By R. Koen, H. Visser, A. Roodt

"SynopsisThe tetraethylammonium salt of the mono-anionic coordination compound mer-oxidotrichlorido(thenoyltrifluoroacetylacetonato- K2O,O’)niobate(V) (NEt4)[NbOCl3](ttfa)], has been prepared under aerobic conditions and characterized by single-crystal X-ray diffraction. (NEt4)[NbOCl3](ttfa)] crystallized in the monoclinic P21/c space group, with a = 11.483 (5), b = 12.563 (5), c = 17.110(5) Å, and ß = 100.838 (5)o. The complex structure exists in a 50.0% (NbA) : 50.0% (NbB) positional disorder ratio.IntroductionComplexes containing organometallic type ß- diketone ligands with O,O and O,N donor atoms are used widely in coordination chemistry and have applications in catalysis, radiopharmaceuticals, etc. (Schutte et al., 2011; Roodt, Visser and Brink, 2011; Brink et al., 2010; Otto et al., 1998). These ligand systems are very useful because of their highly coordinative nature, high solubility, and also due to their ability to be functionalized with various substituents on the carbonyl carbon atoms (Schutte et al., 2011).Only a small number of ß-diketonate ligands have successfully been coordinated to a Nb(V) metal centre, with only a select few being characterized by X-ray crystallography (Viljoen, 2009; Bullen, Mason and Pauling, 1965; Preuss, Lamding and Mueller-Becker, 1994; Funk, 1934; Davies, Leedlam and Jones, 1999; Allen, 2002. The synthesis and crystal structure determination at room temperature of mer-oxidotrichlorido (thenoyltrifluoroacetylacetonato- k2O,O’)niobate(V) {(NEt4)[NbOCl3(ttfa)]} was first reported by Daran et al. in 1979. Accordingly, for this current investigation, (NEt4)[NbOCl3(ttfa)] was re-evaluated at 100 K to determine if the structural features might change with temperature."

Jan 1, 2015

By G. P. Dyke

The MRMR Classification System was developed specifically for mining applications, namely caving operations, and is one of three rock mass classification systems used in the South African mining industry today. Increased usage of the MRMR Classification System has raised concerns that it does not adequately address the role played by discontinuities, veins and cemented joints in a jointed rock mass. To address these concerns, Laubscher and Jakubec introduced the In-Situ Rock Mass Classification System (IRMR) in the year 2000. Although the IRMR System is more applicable to a jointed rock mass than the MRMR System, a quantitative comparison of the MRMR and IRMR Classification Systems indicates that there is not a significant difference between the resultant rock mass rating values derived from the two Classification Systems.

Jan 1, 2008

By R. F. Taberer

Within the technology field generally known as biological heap leaching or percolation leaching, lies a wealth of technological knowhow that is potentially patentable and therefore can form the subject matter of patent applications. An organization often overlooks the potential for generating intellectual capital during its research by dismissing the possibility that what it is working on may be novel and inventive and therefore patentable. The organization labours under the misconception that there is nothing patentable in its work mainly because the novel aspect is overlooked against the general background state of the art or, if identified, is not recognized as having sufficient inventive merit. In the field of biological heap leaching, patents have issued on inventions that extend across a large range of technology, including microbiological inventions-for example a particular strain of microbe used in a heap leach application, electro-mechanical inventions, for example a column simulator that simulates the heap leach environment, and thermodynamic inventions such as methods of generating and maintaining heat in a heap.

Jan 1, 2012

By D. Seke

Metal inventories are usually reported in financial statements of mining companies. However, the value of these inventories can be reliable only if the metals in stock are measured within acceptable tolerances. Reliable metal balancing requires accurate mass measurement, sampling, and chemical analysis. Many mining companies are usually unable to validate the accuracy of metals in inventories at the end of their financial year. This is mainly due to poor mass measurement, sampling, and chemical analysis practices. This has an adverse impact on metallurgical accounting and metal valuation. In addition, it puts a lot of stress on external auditors, who have the duty to recommend the approval of the financial statements to the board of directors. Although a full value chain of metal reconciliation includes the accuracy of Mineral Reserve definition and grade control at the mine, this paper discusses the implementation of best practices for mass measurement, sampling, and chemical analysis at processing plants. This is an important aspect of sampling and reconciliation that is required in order to improve the reporting of inventories in the financial statements of public mining companies. Keywords metallurgical accounting, corporate governance, sampling, analysis.

Jan 1, 2014

By R. M. G. Machunter

The use of testwork to establish an economically feasible separating plant has been a long established practice in the mineral processing industry. However, uncertainties in orebody characteristics and equipment/plant operation can have a significant impact on the separation performance of a given project. This paper explores the impact of uncertainties derived during testwork at key processing stages on the overall performance of mineral processing flowsheets. Case studies for both mineral sand and iron ore projects will be used to illustrate the concepts studied in this paper.

Jan 1, 2007

Copper cyanide is a common component of cyanide-treatable precious metal ores. The copper concentration in production heaps can be predicted from laboratory column tests, but the exact correlation is not necessarily intuitive. Generally, heap leach operators like to keep copper concentrations in solution below 300?500 ppm and may note problems with gold recovery and cyanide consumption when copper concentrations exceed this amount. There are several methods of copper removal from cyanide solutions including ion exchange; direct electrowinning; acidification, volatilization, and recovery (AVR); and sulphide precipitation such as the sulphidization, acidification, recycling, and thickening (SART) process. SART involves acidification with addition of soluble sulphide, separation of the resulting copper sulphide precipitate, and addition of lime to re-establish alkalinity prior to returning the solution to the leaching process, recovering both copper and cyanide as valuable products. In principle SART is very simple. Yet some SART plants that have been built may have been unnecessarily complex. This paper explores the basics of SART and makes the case for a simple plant design as applied to the heap leaching circuit.

Jan 1, 2012

By P. J. Kinver

This paper deals with the development of backfilling methods and systems at the Broken Hill orebody of Black Mountain Mineral Development Company (Pty) Limited, at Aggeneys in the north-western Cape Province. Production started in 1979, being confined to large diameter blasthole stoping methods in the upper, steeply dipping areas of the orebody. This blasthole reserve is now depleted and the production tonnage, 100000 tons per month, is produced from eight cut and fill stopes in the flatter dipping areas of the orebody. The fill methods of the blasthole stoping area evolved prior to the pillar extraction are briefly discussed together with the resulting experiences gained that enabled virtually 100% extraction to be achieved. The original cut and fill mining used costly hydraulic cemented fill; this was replaced partly by unconsolidated river sand and later by dune sand which occurs in abundance. The paper describes the planning, research work and commissioning of a cycloning plant that now enables dune sand to be used successfully as an unconsolidated hydraulic fill. The development of drainage, placement and control methods are also reviewed.

Jan 1, 1988

Material transfer in underground mines often relies on ore and waste pass systems. Over the years the authors have investigated the design and performance of orepass systems in several Canadian and South African mines. It has been recognized that while most mining operations have either implicitly or explicitly clearly defined objectives, in the design and successfully operate orepass systems there seems to be an absence of a strategy on how to best attain these goals. Consequently, it is not surprising that the majority of operations reviewed by the authors experience a number of problems of varying degrees of severity and economic consequences. This is illustrated by reference to both South African and Canadian operations. The second part of this paper focuses on a review of tactical interventions to rectify orepass problems or mitigate their impact. The paper closes with a framework for a flexible strategy for the design and operation of orepass systems. Keywords orepass; orepass design; orepass stability; orepass rehabilitation; orepass operation; orepass strategy.

Oct 1, 2013

By J. A. L. Napier

Computer programs which rely on the assumption of linear, elastic rockmass behaviour have been used routinely for many years in the South African mining industry to determine the stresses arising in the vicinity of mining excavations. A description is given of the theoretical background and novel solution techniques used in the recently developed MINSIM-D boundary element program. Features of the program include the ability to analyse multiple interacting reef planes at arbitrary orientation to one another, slippage on fault planes and the effects of backfill placement in mined areas. Incremental mining sequences can be modelled, and digitizer and front-end routines have been written to assist in the capture of mining outlines and general problem specifications. A brief indication is given of design problems for which MINSIM-D is appropriate, as well as some future extensions of the system.

Jan 1, 1987

A knowledge of the steady-state mass and energy requirements of a particular process is essential to a determination of the economic feasibility of that process. A predictive simulation technique can be of great value in this respect. A versatile computer program based on a fundamental thermodynamic approach has been developed for the prediction of process requirements. The equilibrium composition of a multiphase system is determined by the technique of free energy minimization. Energy-balance calculations are performed using the appropriate thermodynamic data for the chemical species present in the composite materials used. All models for the process units under consideration are written in modular form, the output being calculated from the input and the specified operating conditions. The computer program is written in such a way that it can be used easily by anyone familiar with the processes involved, even though he may have no previous experience with a program of this type. The program is structured so as to facilitate the varying of one parameter without any alteration to the others, thus simplifying the investigation of the effects of any parameters considered to be important. The program has the advantage of being able to compare existing and new processes on the same basis, namely from the ores to the molten metal.

Jan 1, 1987

By G. P. Dyke

The MRMR classification system was developed specifically for mining applications, namely caving operations, and is one of three rock mass classification systems used in the South African mining industry today. Increased usage of the MRMR classification system has raised concerns that it does not adequately address the role played by discontinuities, veins and cemented joints in a jointed rock mass. To address these concerns, Laubscher and Jakubec introduced the In-Situ Rock Mass Classification System (IRMR) in the year 2000. Although the IRMR system is more applicable to a jointed rock mass than the MRMR system, a quantitative comparison of the MRMR and IRMR classification systems indicates that there is not a significant difference between the resultant rock mass rating values derived from the two classification systems.

Jan 1, 2008

By G. Lyman

The cross-belt sampler is a device that is very widely used even though it has not been ratified by the Standards associations. This paper is concerned with the bias testing of two cross-belt sampler designs against stopped belt samples and a cross-stream cutter at the belt end. The bias analysis is carried out using size distribution as the analyte and conventional t-testing and the Hotelling T squared test, which are compared for their effectiveness. The paper considers the issue of detectable bias and the statistical planning of bias tests.

Jan 1, 2009

By S. Özgen

In this study, the possibility of beneficiation of chromite tailings in the Uckopru/Fethiye-Turkey region by a combination of hydrocyclone and multigravity separator (MGS) was investigated. The two significant operational parameters of hydrocyclone, which were diameter of the apex and diameter of the vortex, and the three significant operational parameters of the MGS, which were drum speed, tilt angle, and wash water, were varied and the results were evaluated with the central composite rotatable design. In order to produce a chromite concentrate by hydrocyclone and MGS, mathematical model equations were derived by computer simulation programming, applying the least-squares method using Minitab 15. Second-order response functions were produced for the grade and recovery of chromite concentrates.

Jan 1, 2012

By L. A. Abichequer

ROM grade variability is one of the most important factors influencing plant product recovery. Due to the influence of grade variability on mine profits, it is deemed important to guarantee a proper homogenization of the ore through a well-planned blending and homogenization pile system from which the ore is reclaimed at an acceptable grade fluctuation. This study tests geostatistical simulation efficiency in predicting in situ grade variability. The methodology is illustrated using a data-set from a large phosphate mine in central Brazil. Additionally, real data obtained at the mine site during January and February 2007 were used to derive the actual grades of each pile formed during this period. Each pile was formed by a selection of blocks within a dig line and these lines mined along the year 2007 were also made available. Given the real grades, it was possible to reconciliate and validate the results predicted by the proposed methodology. The main outcome of this study is the opportunity to check the geostatistical simulation as a tool to quantify the variability of the homogenization system.

Jan 1, 2009

By J. L. Louw

The utilization of centralized blasting systems is progressively becoming a feature of the South African mining industry, owing to increased pressure from the Department of Mineral Resources (DMR) to ensure safer blasting conditions. The purpose of a centralized blasting system (CBS) is to ensure reduced blasting-related incidents and to improve the underground working environment for the mine?s employees. The brief from Samancor Western Chrome Mines (WCM) pertaining to this study was to explore?at a conceptual level?all variables pertaining to the implementation of the CBS. Studies have indicated that Sasol?s SafeBlast? was preferred due to low overall risks and user-friendliness. Empirical observations, however, indicated that attention should be given to the current shaft-clearing procedure and to the installation of additional transformers. This is required to co-ordinate the power supply from 2 level to 10 level with the required supply of the network slave station. A cost analysis indicated that an electronically initiated CBS will result in a R24 cost increase per panel, which relates to a mere 1% cost increase per panel. This cost, in addition to the R1.1 million capital cost, proved to be negligible in comparison to the possible direct and indirect costs incurred by the mine in the event of a blasting-related incident. It was found that Samancor should conduct further studies incorporating the necessary requirements to ensure a successful transition, while considering all stakeholders on the mine. This study proved that the transition to a CBS would ensure safe and efficient blasting at Samancor?s Mooinooi Mine.

Jan 1, 2012