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By S. Frimpong, S. R. Dindarloo

Material handling in open pit mining accounts for about 50% of production costs. The selection and deployment of efficient, safe, and economic loading and haulage systems is thus critical to the production process. The problems of truck and shovel selection and sizing include determination of the optimal number and capacities of haulage and loading units, as well as their allocation and operational strategies. Critical survey and analysis of the literature has shown that deterministic, stochastic, and experimental approaches to these problems result in considerably different outputs. This paper presents a comprehensive simulation framework for the problem of truck and shovel selection and sizing based on the random processes underlying the network-continuous-discrete event nature of the mining operation. The framework builds on previous research in this field and attempts to address limitations of available methodologies in the form of a comprehensive algorithm. To test the validity of the framework a large open pit mine was evaluated. The stochastic processes governing the uncertainties underlying the material loading and haulage input variables were defined and built into the stochastic model. Discrete event simulation was used to simulate the stochastic model. The proposed model resulted in several modifications to the case study.

Jan 1, 2015

Application of Gy?s formula is appropriate for calculation of the Fundamental Error (FE) prior to samples being collected at any stage of the minerals process, provided that sampling parameters K and a (alpha) have been determined by calibration of the ores. Two types of calibration procedure are well established in the industry, the Hetrogeneity test and the 32-piece sampling tree experiment. The sampling tree experiment uses the variance and average grade of metal analyses from four series of samples at different nominal fragment size, as the basic input data. Pierre Gy suggested the cube as an appropriate exponent of the nominal fragment size for use in his equation. More recent work suggests that this exponent is variable and characteristic of specific ores and therefore requires calibration. The method described here explains the experimental procedure of the calibration. It is then possible to calculate a sampling nomogram using the sampling parameters K and a. This allows the sampler to determine a suitable protocol for the sampling event that will ensure that the FE does not exceed a predetermined precision at any point in the sampling procedure.

Jan 1, 2007

Models are used in engineering to reproduce reality as faithfully as possible so that the expected response of a system for given actions or inputs can be determined. In the field of rock engineering, both empirically based and numerical models are widely used to determine the likely response of the rock surrounding excavations. Many of the empirical models are developed from statistical analysis of case histories or from direct observation; however, empirical models are limited because they should be used only within the range of conditions of the observational database. Synergy exists between empirical and numerical models, because empirical models can be used to calibrate and validate numerical models. The empirical approach can benefit from the capability of numerical models to investigate specific mechanisms, which would not be possible using observations alone. Two cases are presented in which the synergy between empirical and numerical models is demonstrated. The first case examines the analysis of discontinuity effects on the strength of slender pillars in limestone mines, and the second case evaluates the effects of stress orientation on coal mine entry stability. It is concluded that numerical model calibration and verification comprises an important first stage in the successful application of models in rock engineering design. Application of numerical models allows mechanisms and interactions of various parameters to be analysed, greatly improving the understanding of the system. The improved understanding can be used to extend the application of empirical design methods, resulting in improved safety and efficiency of rock engineering designs.

Jan 1, 2014

By T. Y. Yunsel

Estimation techniques such as polygonal, triangular prism, trapezoid, isopach maps, and inverse distance methods are often used in ore or industrial minerals deposit evaluation. These techniques do not express the variability of the deposit and do not allow a determination of the reliability of the estimates. However, geostatistical methods can express a measure of the error associated with the estimates, by finding weighting coefficients for a given mining block, and can also help with data configuration that minimizes the error. This work addresses an application study on the quality and reserve characteristics of the cement raw materials of the Adana Cement Factory in Adana, Turkey, based on the spatial distribution and variability of the chemical components (Si02, CaO, A1203, Fe203). The study has been carried out using a geostatistical procedure that is useful for site assessment, characterization, and monitoring situations where data are collected spatially. Directional and omnidirectional experimental variograms of the cement raw material variables showed that neither strong geometric nor severe zonal anisotropy exists in the data. The most evident spatial dependence structure expressing the continuity for omnidirectional experimental variograms were characterized by exponential and spherical variogram models. These models have been used in cross¬-validation analysis, which proved that these models, their parameters, and kriging parameters are applicable for the study area. Quality contour maps of the deposits at given levels underground were estimated using a kriging interpolation technique. Anomalies such as bullseyes and drift were not observed in the maps that were generated. Kriged maps showed the spatial distribution of quality continuity and variability of the deposits. Grade-tonnage curves and total tonnage estimates in the particular grade were determined using ordinary kriging in order to improve the mining operation and planning. Consequently, local uncertainty and the probability of extreme values occurring are tools of prime importance for the mine planning, the optimum mix of raw materials coming from different quarry stopes.

Jan 1, 2012

By D. F. Malan, Y. Jooste

"SynopsisScattered mining was practised on Kusasalethu Mine (previously Elandsrand Gold Mine) prior to 1998, but at deeper mining levels it was no longer feasible, since it would have resulted in unacceptably high stress levels and energy release rates. Longwall mining was not adopted at these depths as the mine required a more flexible mining method owing to the highly variable grade and the presence of geological structures. A mining method was developed that consisted of dip stabilizing pillars for regional support, as well as bracket pillars to clamp geological structures. A strict sequence of extraction was followed and this, together with the particular layout, was called the ‘sequential grid mining method’. This method addressed two key problems, namely negotiating adverse geology and the erratic grade of the Ventersdorp Contact Reef (VCR) orebody. However, a significant drop in production rates resulted in the need for alternatives and improvements to the original mine design. Modifications to the design were proposed in order to increase production rates, and an investigation to consider the rock engineering implications of these modifications was conducted. The study indicated that the modified method, called the ‘multi-raise mining method’, appears to be feasible and might address some of the production problems that were experienced with the original sequential grid design. An analysis of actual seismic data showed no significant differences between the original sequential grid mining and the implemented multi-raise mining. The numerical modelling of the mining layouts showed slightly higher interim energy release rates (ERRs) and average pillar stress (APS) levels during the extraction process. The final values are nevertheless identical to that of the original sequence. The study also investigated the use of a modelled moment method to analyse future seismic trends. The study illustrated that the expected seismic trends will be very similar for the multi-raise method compared to the original sequential grid mining method. This study is nevertheless considered of a preliminary nature and ongoing monitoring and analysis of seismic data at the mine is required to verify the response of the rock mass to the modified sequence and increased extraction rate. In particular, future work needs to investigate the effect of mining rate (advance rates in individual panels as well as volume of mining in particular raise lines) on the level of seismicity."

Jan 1, 2015

A systematic study of groundwater conditions at eight underground mine sites exhibiting a wide range of groundwater qualities throughout Australia has been completed at the WA School of Mines. This has resulted in a new corrosivity classification for groundwater driven corrosion processes for cement grouted cable strand used in the Australian underground mining industry. The new corrosivity classification is simple to use and corrosion rates may be predicted from readily obtained in situ measurements of groundwater dissolved oxygen.

Jan 1, 2008

By B. K. Loveday, N. V. Ramlall

A study was carried out to evaluate various batch flotation models for the recovery of minerals in a UG2 platinum ore. The major minerals in a UG2ore can be grouped as platinum group minerals, chromite, and siliceous gangue. This study also examined the entrainment of minerals during flotation. The models were ranked using statistical methods and an analysis of model-fit residuals. Entrainment parameters obtained from model fitting were evaluated for logic using a simple mineral-to-water ratio versus time plot. The foremost conclusion from the study was the importance of entrainment modelling. The measurement of water recovery increased the size of the data-set, and the inclusion of a simple entrainment model was statistically significant. The overall fit to the data was improved, and the entrainment model provided logical information on the recovery of gangue minerals that were not considered to be floatable.

Jan 1, 2015

By J. M. McKinley

Mineral exploration programmes around the world use data from remote sensing, geophysics, and direct sampling. On a regional scale, the combination of airborne geophysics and ground-based geochemical sampling can aid geological mapping and mineral exploration. Since airborne geophysical and traditional soil-sampling data are generated at different spatial resolutions, they are not immediately comparable due to their different sampling density. Several geostatistical techniques, including indicator cokriging and collocated cokriging, can be used to integrate different types of data into a geostatistical model. However, with increasing numbers of variables the inference of the crosscovariance model required for cokriging can be demanding in terms of effort and computational time. In this paper a Gaussian-based Bayesian updating approach is applied to integrate airborne radiometric data and ground-sampled geochemical soil data to maximize information generated from the soil survey, enabling more accurate geological interpretation for the exploration and development of natural resources. The Bayesian updating technique decomposes the collocated estimate into two models: prior and likelihood models. The prior model is built from primary information and the likelihood model is built from secondary information. The prior model is then updated with the likelihood model to build the final model. The approach allows multiple secondary variables to be simultaneously integrated into the mapping of the primary variable. The Bayesian updating approach is demonstrated using a case study from Northern Ireland. The geostatistical technique was used to improve the resolution of soil geochemistry, at a density of one sample per 2 km2, by integrating more closely measured airborne geophysical data from the GSNI Tellus Survey, measured over a footprint of 65 x 200 m. The directly measured geochemistry data were considered as primary data and the airborne radiometric data were used as secondary data. The approach produced more detailed updated maps and in particular enhanced information on the mapped distributions of zinc, copper, and lead. The enhanced delineation of an elongated northwest/southeast trending zone in the updated maps strengthened the potential for discovering stratabound base metal deposits..

Jan 1, 2014

By N. J. Castilla, R. Giglio

"Circulating fluidized-bed (CFB) combustion technology has been around for over 40 years, but over the last 6 years it has been commercially demonstrated at the 500 MWe scale at the Lagisza plant located in Bedzin, Poland. The CFB at the Lagisza plant has unique first-of-a-kind design features, such as vertical-tube supercritical steam technology and a lowtemperature flue-gas heat extraction that allows the plant to achieve high plant efficiencies of over 43% (net lower heating value). Another unusual feature for a coal power plant is that this plant meets all its atmospheric emission permit levels without any post-combustion de-NOx or de-SOx equipment such as selective catalytic reduction (SCR) or flue-gas desulphurization (FGD).CFB clean coal power technology is entering the utility power sector just in time to help deal with declining quality in internationally traded coals and to promote the large-scale use of economic, low-quality domestic fuels. Owing to the very attractive price discounts, growing supplies of low-quality Indonesian coals are outpacing the supply of high-quality Australian, Russian, and US coals. In Germany and Turkey, the use of domestic lignites for power production provides a secure and economic energy solution while creating domestic jobs.Conventional pulverized coal (PC) boilers will have trouble accepting these off-specification coals because of their narrow fuel specifications; they typically call for heating values above 5500 kcal/kg. This limitation is not an issue for CFB technology because of its ability to burn the worst and best of coals with heating values ranging from 3900 to 8000 kcal/kg.This paper provides an outlook for future coal supply, quality, and price, as well as a review of the technical and economic benefits of CFB technology firing low-quality fuels for utility power generation."

Jan 1, 2015

By FT Cawood

The latest Draft MPRRB was released for public comment in October 2006. The main purpose of the Bill is to collect royalties at mines developed in terms of new-order mineral rights granted through the MPRDA process. The transition phase stipulated in the MPRDA will be completed by 1 May 2009, on which date mineral royalties will become payable to the state. The royalty rates stated in the MPRRB differ from mineral to mineral and also depend on the degree of refinement. Gold is the subject of this paper, where the royalty rate ranges from 1.5% (for refined gold) to 3% (for unrefined gold) of sales revenue. This royalty is payable regardless of profit, with a maximum 75% relief for loss-making mines. The purpose of this paper is to establish whether or not it would be necessary for gold mines to adjust their mineral reserve statements as a result of this Bill. The methodology is to add the royalty costs stipulated in the MPRRB to the actual quarterly information for the past ten years as reported by the gold-mine members of the COM. The rationale is to investigate the impact this Bill (in its current form) would have had on gold reserves that must be left unmined in the ground because of a higher pay limit. The results of the study point to a significant impact on reserves available for mining with the subsequent shortening of mine lives and retrenchment of workers. Had the MPRRB been effective for the 10 years prior to 1996, it would have resulted in 46 tonnes of gold being sterilised. Stated alternatively, 30 700 workers at COM gold mines alone would have lost their livelihoods.

Jan 1, 2007

By J. T. Nel

Non-transfer-arc linear plasma systems are highly suited to manufacturing nanoparticles. In this paper, the manufacturing of such particles with specially designed plasma systems is discussed. In general, it entails the volatilization of a metal halide that is injected in the high-temperature region of a plasma flame, where it is reacted with a suitable reagent, for example O2, to produce nanooxide powders. Metal powders can also be introduced directly in the plasma. Due to the very short residence time of only milliseconds in the reaction zone, as well as the fact that the reaction takes place in the gas phase, combined with very rapid quenching in the order of 10 000°C.s-1, nanoparticles are produced. At Necsa the manufacturing of such particles has been demonstrated on various scales. A pilot plant for the production of nano-Al2O3, and two pilot plants, one using SiCl4 and the other one using SiF4 as feed material, were built to produce fumed, pyrogenic, nano-SiO2. The alumina plant had a production rate of 8?10 kg.h-1 and the silica plants had production rates of 2 and 10 kg.h-1 respectively. Perfectly spherical alumina particles with a particle size distribution of between 10 and 200 nm were produced on a continuous system. Particle size analysis for the silica by SEM measurements showed a d50 of 60 nm and a particle size distribution of 30?100 nm. The specific surface area was in the range of 170m2.g-1. Other samples of plasma produced nanoparticles such ZnO and B4C will also be presented.

Jan 1, 2010

By N. Z. Fotoyi

Keywords: MgO-MgR2O3 refractory, SO2-containing gases, chemical attack The reaction mechanisms occurring when MgO-MgR2O3 refractories are exposed to SO2-containing gas atmospheres were examined. The study examined the characteristic structures of magnesite-chrome, chrome-magnesite and magnesite refractories exposed to SO2-O2 gas mixture at temperatures of 700°C to 1350°C. The phase characterization was conducted with scanning electron microscopy (SEM) and powder X-ray diffractometry (XRD). The results show that the physical characteristics of the refractory matrix along the grain boundaries are important refractory features during chemical attack from SO2-containing gas. Upon heating in SO2-containing gas, the changes in phase-chemical compositions and accompanying grain growth causes loosening of the structure and the pore volume promotes gas diffusion. The chemical reactions that occur form stable sulfate compounds identified as MgSO4, CaSO4 and CaMg3(SO4)4, and lead to disintegration of various phase structures and consequently erosion of the refractory. In conclusion, the reaction mechanisms in MgO-MgR2O3 refractories exposed to SO2-containing gases progress through a combination of structural disintegration and chemical attack.

Jan 1, 2011

By W. Vorster

Bateman Engineering Project's acid-plant track record goes back to 1977. Bateman Engineering can design sulphuric plants based on gas from sulphur burners, metallurgical off gas as well as pyrite roasting systems. Bateman Engineering has a technology marketing agreement with NORAM Engineering Ltd of Canada to provide state-of-the-art, well-proven acid plant technology, and also has access to roaster technology from several sources, including Chinese technology. Utilising the Noram technology agreement, Bateman was awarded the Engineering and Procurement (EP) contract for the Ambatovy Nickel Project, Sulphuric Acid Facilities in 2007. This is the first Greenfield sulphuric acid plant Bateman has designed for many years, producing a combined 5,500tpd, and is one of the largest sulphur burning acid plants in the world. This paper gives an overview of the sulphuric acid plant for the Ambatovy Nickel Project, advantages of Noram?s unique technology on offer, an overview of work conducted on a recent study of an pyrite roasting acid plants as well as a new technology currently being developed by Bateman for the direct combustion of solid sulphur to form sulphur dioxide.

Jan 1, 2009

By W. Vorster

Bateman Engineering Project's acid-plant track record goes back to 1977. Bateman Engineering can design sulphuric plants based on gas from sulphur burners, metallurgical off gas as well as pyrite roasting systems. Bateman Engineering has a technology marketing agreement with NORAM Engineering Ltd of Canada to provide state-of-the-art, well-proven acid plant technology, and also has access to roaster technology from several sources, including Chinese technology. Utilising the Noram technology agreement, Bateman was awarded the Engineering and Procurement (EP) contract for the Ambatovy Nickel Project, Sulphuric Acid Facilities in 2007. This is the first Greenfield sulphuric acid plant Bateman has designed for many years, producing a combined 5,500tpd, and is one of the largest sulphur burning acid plants in the world. This paper gives an overview of the sulphuric acid plant for the Ambatovy Nickel Project, advantages of Noram?s unique technology on offer, an overview of work conducted on a recent study of an pyrite roasting acid plants as well as a new technology currently being developed by Bateman for the direct combustion of solid sulphur to form sulphur dioxide.

Jan 1, 2009

By I. C. Spangenberg

The status of sampling practices in the gold mining industry in Africa was determined as an initial step in a process to standardize sampling practices in the mining industry. Twenty-one gold mines, twenty metallurgical plants, and thirteen laboratories were rated for the potential influence of the relevant sampling errors on each component of the particular sampling system. The findings of the study on the status of equipment, standards, procedures, and management principles were presented in a dissertation (Spangenberg, 20121) and are now used by AngloGold Ashanti?s mines in the quest for correct sampling practices. The information is also used to compile a guideline on leading practice procedures for sampling methods in gold mining. This article is an overview of sampling best practice found in African mining Keywords theory of sampling, best practise, sampling errors, sampling standards.

Jan 1, 2014

By J. N. Van der Merwe

Due to the approaching depletion of reserves in the Witbank Coalfield, and the fact that the Waterberg Coalfield is as yet under developed, there is increasing pressure to extend the lives of the operating coal mines in the Witbank Coalfield. One potential source of coal is the old pillars, often small and at shallow depth, that were not left with secondary extraction in mind. At face value, some of these pillars appear to be suitable for secondary mining due to their high safety factors. However, it is known that over time, these pillars have scaled and the current sizes are smaller than the as-mined dimensions. It is also known that at shallow depth, the overburden is often less likely to fail during secondary mining, resulting in high abutment loads on the unmined pillars. The paper proposes a systematic method to pre-evaluate those old pillars for the possibility of stooping. The method consists of elements of fundamental methods and newly developed technology. In essence, it revolves around using empirical methods to estimate current pillar dimensions, followed by numerical modelling to investigate the probability of progressive pillar failure and then fundamental methods to determine the limits of applicability of the numerical model.

Jan 1, 2012

By T. Güyagüler, A. Güngör

Labour protection, that is prevention of occupational disease and reduction in the frequency of accident, has always been a matter of major concern of mining industry. Management and the government should promote and maintain high safety standards through some measures to reduce accident frequency and occupational disease. This can be achieved by using the science and technology for improving the working conditions, educating workers and managers about accidents and prevention techniques. The detailed analysis of an accident requires knowledge of many factors such as location, time, type, cost of accident, victim, nature of the injury, personal and environmental factors etc. that can be obtained from the standard coded accident report form. There is a need to prepare safety data in a common format to produce a common safety reporting system and ‘Occupational Health and Safety Management Tool’ is being designed to manage this by using database and Internet technology. Precautions should be taken according to results from database queries by providing comprehensive and accurate national data. To have an accident is unfortunate, however, to have an accident and learn nothing from it is unforgivable. Keywords: Occupational health and safety, Accident report form, Accident database, Occupational diseases and accidents, Safety reporting system.

Jan 1, 2003

By F. T. Cawood

This research report was produced in response to the release of the Mineral and Petroleum Royalty Bill. It involved are view of the mineral investment environments of selected countries in order to form an opinion on the appropriateness and competitiveness of the proposed royalty structure for South Africa. Many emerging countries have recently attracted a significant share of foreign investment, as a direct result of changes in policy. These are, by implication, the least risky and most favourable destinations for the ?investment dollar?. The five most competitive countries, namely Chile, Argentina, Peru, Mexico and Brazil have been identified as succeeding with their policy visions of creating favourable domestic investment environments. The investment rules of these countries served as a basis for the compilation of a Competitive Investment Framework (CIF). This is a template of best practice against which other investment environments, such as that of South Africa, can be measured. The framework indicates that mineral royalties should ideally be no more than three per cent, demonstrating that the regime proposed in the Royalty Bill is out of step with international best practice. Mineral royalties can never be viewed in isolation and in the assessment of the rates proposed in the Royalty Bill, one must consider the total taxation package. Such assessment appears in Section 5 of this report, demonstrating that there is reason for concern if National Treasury were to impose the rates stipulated in the Royalty Bill. The alternatives, conclusion and recommendations of the review appear in Sections 9 and 10. These are the result of independent analysis and assessment of the fundamental principles. It is done through the application of a Competitive Investment Framework that avoids the highly subjective and emotional views that often accompany a process like this.

Jan 1, 2003

By M. W. Hildyard

The aim of this paper is to demonstrate that active seismic measurements could have an impact in helping solve rock engineering problems experienced in the South African mining industry. The paper presents a variety of experimental and numerical results where seismic waves show clear differences in wave-speed and amplitudes due to different degrees of fracturing. It presents results from the ?Omnibus? project commissioned to develop new ultrasonic technologies for diagnosing fracturing for nuclear waste repositories. This included using models to investigate assemblies of cracks where the effects of crack density and crack size on waveforms are shown to be coupled. Results indicate that these effects can be decoupled in the frequency domain, where the Fourier amplitude aids in estimating crack size, while the low frequency phase-difference has a direct relationship to crack density. Models are also shown to aid interpretation of waveforms by isolating geometric effects from the effects due to cracks. Two rock engineering problems experienced in the South African mining industry are investigated through numerical examples. These demonstrate that determining whether ?crush? pillars have failed and determining the degree of fracturing in the hangingwall of stopes, may be possible through the use of active seismic surveys.

Jan 1, 2005

By C. Legote

"This paper investigates the conditions leading to the indefinite termination of production in four critical primary panels at an underground coal mining operation, the observed shortcomings in the mining approach, and the proposed strategy to mine through the affected panels. Initial assessment of the abandoned panel conditions indicated time-dependent strata failure,(i.e. bolted roof failure overrunning intersections), which occurred from mere minutes to up to four weeks post-production, with and without prior warning of failure. This prompted the constant re-supporting of back areas, which raised safety and productivity concerns. Investigation of the initial mining conditions revealed that the failures were due to a critical combination of factors, the chief of which was isolated horizontal stress. Other factors that were initially overlooked by the mine (i.e. influence of hydraulic stress, misinterpretation of borehole data), resulted in the conditions being described as abnormal. Remedial actions were determined, and in so doing, a new strategic approach was formulated to thoroughly address all failure concerns. The four panels were explicitly planned to serve as the main intake and return airways for the recently commissioned secondary ventilation shaft, as well as providing access to millions of tons in proven coal reserves. It is thus imperative to mine the panels. A feasibility study showed that the proposed strategy set for implementation would be financially viable. Paper written as project work carried out in partial fulfilment for BEng(Mining Engineering) degree"

Jan 1, 2015