Search Documents

By M. C. J. van der Merwe

"Carboxymethyl cellulose is an organic binder used in the iron ore pelletizing industry. The basic principles of how carboxymethyl cellulose (CMC) solutions behave during the pelletizing process and how these principles affect the drop and compression strengths of the pellets are poorly understood. The aim of the investigation was therefore to gain knowledge on the behaviour of CMC during the pelletizing of haematite concentrate.Haematite pellets with different additions of CMC (0.1–0.4 wt%), were subjected to drop tests, compression tests, and free moisture content analysis. The relationship between the drop strength, compression strength, free moisture content, elapsed time, and CMC concentration was analysed.The drop strength had a strong correlation with the free moisture content of the haematite pellets, with a correlation coefficient of 0.94. The compression strength of the CMC-bonded haematite pellets increased as the free moisture content decreased, reaching a maximum upon depletion of the free moisture content. Haematite pellets with CMC concentrations of 0.1 and 0.2 wt% developed most of their strength within the first day after pelletizing, whereas pellets with concentrations of 0.3 and 0.4 wt% developed most of their strength between one and two days after pelletizing. The time within which CMC-bonded haematite pellets develop most of their strength is therefore dependent on the CMC concentration. IntroductionFines are produced during the beneficiation of iron ore. These fines are separated from the lump ore and can be upgraded to produce a concentrate, which is used as a raw material for the production of pellets. Pellets in turn form a key burden material for direct reduction processes as well as the blast furnace (Zhu et al., 2015).Inorganic binders such as bentonite have been used predominantly in the iron ore pelletizing process to obtain pellets with suitable properties (Eisele and Kawatra, 2003). These binders, however, have the disadvantage of introducing impurities into the pellets. This has resulted in organic binders being pursued as suitable replacements for inorganic binders, of which carboxymethyl cellulose (CMC) shows good potential. Although CMC has been used as an organic binder in iron ore pelletizing, the fundamental principles of how it behaves during pelletizing and how these impact on pellet properties are poorly understood."

Jan 1, 2017

By L. Chanderman, C. E. Dohm

"Mineral Resource estimation (MRE) and classification are highly dependent on the confidence in the model of the orebody geometry, known as the geological model, within which the estimates are constrained. An understanding of the geology of a deposit is thus fundamental to the Mineral Resource evaluation process. The geological model is a function of the structural and depositional complexity of the geology captured by drilling information, which is limited in the early stages of a project. The information effect has a significant impact in terms of the interpretation of the geology as well as the estimation of grade continuity and the resultant risk associated with the Mineral Resource estimate and classification.Therefore, as new drilling information becomes available, it is necessary to update and refine the geological model to appropriately constrain the resource estimates. The grade information is also updated, including statistics and the spatial correlation characteristics. This refinement is based on geological interpretations derived from the drillhole information that becomes available throughout the life of the mine; orebody knowledge that comes from working experience of the deposit, as well as familiarity with the software package used for modelling, is also important.In updating, the potential to identify new resources in previously unknown areas may be realized. The opposite may also occur where previous interpretations of ore continuity are refuted. Both scenarios could result from a better understanding of the geology of the deposit and thus a more realistic MRE, which reduces geological risk. This paper describes how newly drilled advanced grade-control holes for a gold deposit in Mali were used to refine the 3D geological model for the deposit in an attempt to identify the potential for additional oxide ore using conventional geostatistical evaluation techniques."

Jan 1, 2017

By S. A. Hosseini, O. Asghari

"Recoverable mineral resources assessment has become a standard geostatistical application in the mining industry, with various geostatistical techniques currently available. This investigation aimed to improve the prediction at the Sungun deposit and to obtain mineral resource models capable of handling (i) the change of support from drill-hole composites to selective mining units (SMUs), (ii) the multivariate nature of the ore control selection criteria that involves both copper and molybdenum grades; and (iii) the local uncertainty on the true (unknown) grades. The solution presented in this paper is to use direct block-support sequential cosimulation in order to construct a set of alternative outcomes of the copper and molybdenum grades on block support over the deposit, with no need for storing point-support values, hence with a considerable gain in memory management and CPU time. The grade realizations so obtained are then processed to calculate the uncertainty in the mineral resources that can be recovered above given cut-off grades, both globally and on a blockby- block basis. IntroductionGeostatistical methods are widely used by mining companies to determine a resource model of the tonnage and head grade of a potential orebody, which is one of the first and most critical inputs underpinning any mining project. The prediction of the grade, tonnage, and recoverable metal for a particular mining plan and the corresponding financial forecast constitute the main technical risks in mineral resource evaluation. The conventional approach to this problem is to predict the mineral grade for constant volumes relevant to the mining plan and to base the recoverable mineral resource calculations on those predictions. Alternatively, one can directly predict the local variability in the mining block grades based on a spatial distribution model (David 1988; Rossi and Deutsch 2014). Multiple realizations can also be constructed by conditional simulation, providing a more complete representation of block grade uncertainty, as well as the uncertainty over multiple blocks. Simulation methods allow quantification of the uncertainty of the mineral resource prediction risks in downstream studies such as mine design, mine planning, or operational optimization studies; the risk assessment is achieved after applying transfer functions to the conditional simulation models (Dimitrakopoulos 2012; Rossi and Deutsch 2014)."

Jan 1, 2017

By N. Coulson, P. Ledwaba

"The University of the Witwatersrand presents an accredited four-course training programme for community relations practitioners (CRPs). Between May 2013 and October 2014 six courses were facilitated for 145 participants, of whom 82% were from sub-Saharan Africa, 62% worked in mining, and 58% worked directly with communities. Thematic analysis of the comments of course participants collected during course exercises found that there were a set of coherent drivers for resilient companycommunity relationships, but that the restrainers to resilient relationships were often context-specific and dominated by politics. CRPs reported facing as many difficulties in the internal company environment as in the external environment. These findings for CRPs in Africa resonate with those worldwide.InroductionMuch has changed in how the extractive industry responds to social and community issues. There has been a growing prioritization of community-related issues within the extractive industry globally (Kemp, 2010; Tatar, n.d.). According to Kemp (2010) this can be attributed partly to escalating pressure from local-level stakeholders to push mining companies to take greater responsibility for the social, economic, and environmental impacts of mining. Securing and maintaining the social licence to operate is ranked fourth in terms of the top risks facing the mining and metals industry in 2016, up one place from 2015 (Ernst & Young, 2016).Conflicts between local communities and large-scale mining companies arise because of the social, environmental, and economic impacts of mining. Worldwide, large-scale mining companies have a poor reputation amongst communities, including those in Africa (Gilberthorpe and Banks, 2012; Kemp and Owen, 2013a; van Wyk, n.d.). For mining companies, conflicts for whatever reason, result in loss of productivity, lost opportunities, lost time, and adverse impacts on reputation (International Council on Mining and Metals, 2015). Conflicts also have a significant financial impact on mining operations (Franks et al., 2014). Davis and Franks (2014), estimated that US$10 000–50 000 is lost each day when a project is delayed during the exploration phase, and about US$20 million per week when in operation. Today these costs could be expected to be higher due to increasing input costs."

Jan 1, 2017

By J. N. Van der Merwe

"Platinum is a highly valuable resource, its safe and economic extraction is paramount. The success of platinum mining by the bord and pillar method depends heavily on a comprehensive and dependable pillar design method. Pillars need to be large enough to safely support the load and small enough to avoid loss of resources. A critical evaluation of current pillar design systems used in narrow-reef platinum mining was undertaken using practical experience from a large feasibility-stage platinum exploration project, supplemented by observations from several platinum mines in Zimbabwe. An extensive literature survey was undertaken in order to determine the current status of design systems. Through this approach, the shortcomings of current pillar design systems are highlighted. Areas are proposed for further research to obtain a better understanding on how additional factors influence pillar system stability. The exploration work highlighted how rock mass classification methods can be utilized in determining the overall strength of pillars. Current pillar design systems for narrow-reef platinum mining consider width-to-heightratio (usually with different exponents for width and height) and the strength of the pillar material. However, there are many more important factors that are not considered and which have a bearing on pillar system stability. An in-depth study of these parameters with a view to establish effective narrow- reef platinum mining pillar design systems needs to be undertaken. IntroductionPillars have been used as a means of support since the early days of mining. Pillarsupported mining methods such as bord and pillar require a reliable design system for them to be successful. This paper presents an evaluation of the current hard-rock mining pillar design systems as applied to a practical large-scale narrow-reef platinum mining feasibility study. It is vital to have a dependable pillar design system for economic and sustainable mining. Using an extensive database collected from the project, the pillar strength formulae were tested and several discrepancies noted. This necessitates the establishment of more reliable pillar design systems. In narrow-reef platinum mining, large compressive stresses accompanied by geological and geotechnical factors contribute to pillar instability. A well-formulated pillar design system is required that accounts for such factors so as to minimize pillar failures."

Jan 1, 2017

By C. Birch

"Mineral reserve statements as well as optimizing mine planning require a block model with grades for each mining block. A cut-off grade is determined by considering the mining costs as well as the expected revenue for each block. These grades are estimated using various techniques, but in reality there is uncertainty in the grade values. These uncertainties result in two types of error. A type I error is where material is classified as ore and mined, but the true value is below the cut-off grade and the material is therefore waste. This material constitutes dilution. The type II error is where material is estimated to be below the cut-off grade and is classified as waste, whereas the true grade is actually above the cut-off grade. This material is not mined and the value is lost.This research considers the value of the lost ore and the costs of dilution under various degrees of uncertainty. Simulation using @Risk and mixed integer linear programing (Excel Solver) is used in a financial optimizer model to maximize either profit or net present value. This is applied to four Witwatersrand tabular gold deposits to investigate the impact of block grade uncertainty on cut-off grades.When optimizing for profit, value may be added by adjusting the cutoff grade slightly downwards. When optimizing for NPV, value may be added by lowering the cut-off grade significantly for the lower discounting rates. At higher discount rates, the lowering of the cut-off grades should be reduced, and in some cases an increase in cut-off grade may be required. Each mine reacted differently to the optimization and thus there is no single rule that can be applied across all tabular Witwatersrand gold deposits."

Jan 1, 2017

By G-L. Wu, X-B. Liu, C-Y. Zhou

"The static recrystallization behaviour of Ti-Nb microalloyed high-strength steel during hot deformation was studied by conducting double-hit hot compression experiments using a Gleeble-3500 thermomechanical simulator. The effects of deformation temperature, strain rate, strain, and initial austenite grain size on the static recrystallization fraction are discussed. The static recrystallization kinetics were modelled, and the results show that the static recrystallization fraction increased with deformation temperature, strain rate, and strain and interpass time. The static recrystallization activation energy Qs was 326.05 kJ mol-1. Comparison of the experimental results and predicted results indicates that the effects of deformation parameters on the static recrystallization in multistage hot deformation are significant. The predicted results are in good agreement with the experimental results. IntroductionIn hot-forming processes, complex microstructures are often induced by multiple hot deformation mechanisms (Zhang et al., 2014; Liang et al., 2015). The softening behaviour during hot processing has generated considerable interest because component properties are influenced significantly by the corresponding microstructural evolution (Wu et al., 2010). It is well known that dynamic recrystallization (DRX); metadynamic recrystallization (MDRX), which occurs by the growth of DRX nuclei during intervals of deformation; and static recrystallization (SRX), which occurs by nucleation and growth during the intervals of deformation, can significantly alter the austenite grain size (Chen et al., 2015. Chen, Sui, and Cui, 2014; Mao et al., 2014). The long interpass times allow complete SRX to take place if the steel is being rolled above the interpass recrystallization stop temperature (Tnr), i.e. in the absence of carbonitride precipitation (Siciliano, 2000). In recent research, microalloying technology coupled with new-generation thermomechanical control processing (NG-TMCP) has proved efficient in achieving the proper balance between strength, toughness, ductility, and formability by means of a suitable combination of chemical composition and thermomechanical treatment parameters (Shukla et al., 2012; Bandyopadhyay et al., 2011). The alloying elements Nb, V, Ti are widely used in high-strength low-alloy (HSLA) steel to achieve the desired strength and toughness properties with solid-solution strengthening, precipitation hardening, grain refinement, and dislocation strengthening (Opiela, 2014; Chen and Yu, 2012). The wide applicability of alloying elements in HSLA steel is due to the fact that heat treatments are not required after forming of the parts, which results in time and cost savings."

Jan 1, 2017

By E. Kumar, L. A. Kumar

"A methodology is proposed to develop an optimization model to understand the impact of transporting minerals, from mines to the final destination, on air quality. Recently, there has been increasing concern about the combined effects of multiple activities over many years, and the regional environmental changes brought about by a single project. Environmental issues in the iron ore industry have highlighted the need to broaden the cumulative impact assessment. In this study, we simulated the optimal routes and quantity of materials needed to meet the destination plant demand based upon environment constraints (level of air pollution), as well as the cost of transportation and availability of materials. Multiple scenarios were developed to analyse the effects of changes in routes, alternative transport system (or multi-modal split), traffic congestion, and the cumulative impacts on air quality. The air quality impact zones of the study area were demarcated using a GIS technique. The expected outcome of the study is the selection of a suitable transport system for a particular site with the least impact on air quality, including the transportation route, relative to the minimum cost of transportation of the minerals from the mines to their final destination. The proposed methodology is evaluated with a case study. IntroductionIn India, the process of environmental impact assessment (EIA) has been focused primarily on the local impacts of projects, without considering regional environmental effects. Environmental clearances for proposed projects are based on reports of local impacts. However, any developmental project poses a potential risk to the environment as a whole, and not just in the immediate vicinity of the project. Recently, there has been increased concern about the combined effects of multiple activities over many years—the regional environmental changes due to development of a single project (Dutta, Mahatha, and De, 2004). Environmental issues throughout the country, particularly in the iron ore industry, have emphasized the need to broaden the analysis to include the combined impacts, or those forecast for a proposed region, on an existing environment. The most significant adverse environmental consequences of iron ore transportation are the deterioration of biodiversity and air quality (Kumar and Ajay, 2015)."

Jan 1, 2017

By F. Hees, A. H. Bracken, L. I. Boshoff

"Biological cementation of the Mandena heavy mineral sand deposit in Madagascar was causing difficulty in dredge mining and hence in planning and control of production rates. An investigation was initiated to better evaluate the geotechnical properties of the orebody by defining the distribution and geotechnical properties of the cemented strata, in order to generate a site-specific geotechnical model for the deposit. The geotechnical characterization was developed by an integrated approach using several ground investigation techniques such as piezocone (CPTu) testing, geotechnical drilling, standard penetration testing (SPT), as well as laboratory testing. The final outcomes of the investigation included a 3D geotechnical model showing the distribution and extent of the cemented areas, as well as the typical geotechnical parameter ranges associated with each of the defined geotechnical units. The interpretations developed were incorporated into the mine and production planning to ultimately optimize operational planning and control.IntroductionQIT Madagascar Minerals (QMM) is a heavy mineral sand mining operation at Mandena, near Fort Dauphin in Madagascar. During the final planning and commissioning stages of the project, the need to fully characterize the unusual geotechnical conditions was identified and a geotechnical investigation became necessary.Nature of the problemDuring the commissioning phase it was found that mining production was being hampered by biologically cemented/indurated layers encountered within the sands. Closer inspection of the indurated horizons in the dredging face revealed that these layers contain a high loading of bacteria and fungi. It appears that the bacteria produce an extracellular (outside the cell) polysaccharide (i.e. sugar and carbon salts), which form a gelling biofilm to trap nutrients. There are a number of different bacteria. The fungi, on the other hand, produce a network of fibrous strands that bind the sand grains together. Thus both bacteria and fungi probably contribute to the ‘apparent cohesive’ strength or binding of the indurated sand (Lynn, 2008)."

Jan 1, 2017

By M. H. M. von Wielligh

"Brick manufacturers supply a variety of uniquely coloured facebricks to the building industry, which requires a high level of colour consistency in the products. Colour variation in bricks is influenced by the composition and consistency of the white clay raw material. By blending varieties of naturally occurring white clay the manufacturers produce a unique range of facebrick products. Homogeneity of the white clay raw materials mined at Lenasia is crucial for producing bricks of consistent colour. Geostatistical investigations of the major element distributions (SiO2, Al2O3, Fe2O3, and K2O) and loss on ignition (LoI) were conducted. An analysis of the spatial continuity of these variables followed by ordinary kriging indicated that the upper white clay layer at Lenasia is richer in K2O and Fe2O3 than the lower layer. Consistency in the colour of facebricks depends critically on careful management of the variability in the K2O and Fe2O3 content of the clays. The geostatistical approach to understanding the distribution of elements in the clay allows miners to construct clay stockpiles of consistent quality for feeding the brick-making process. Geostatistical investigation of the chemical contents in other clay domains within the deposit is recommended, and could be extended to all facebrick manufacturers to assist in improving the colour consistency of their products. IntroductionMost clay in South Africa is used in the manufacturing of tiles, pipes, bricks, whiteware, refractories, and pottery. Bricks are manufactured from a wide variety of clay types, the behaviour of which during firing depends critically on the the clay mineralogy and chemical composition, but this relationship not well understood (Stein, 1982). The variety among clay deposits is related to the different processes of formation (Deer, Howie, and Zussman, 1992). The geochemical composition of the clay can vary between layers and within the same layer in an individual deposit (Lurie, 1984). The properties of clay minerals are determined by their structures and the different combinations of silicate layers, cations, and hydroxyl ions (Kingery, Bowen, and Uhlmann, 1976). South African clays can be classified as either kaolinite or montmorillonite and are seldom found in a pure form (Lurie, 1984). Different clay minerals affect the drying, forming, firing behaviour, colour, and quality of the brick product in different ways. Laboratory tests (full physical analysis) can indicate the suitability of a clay for the manufacture of ceramic products. The minerals most essential for the manufacturing of clay brick products are kaolinite, illite, and quartz (Stein, 1982)."

Jan 1, 2017

The two methods for calibrating the parameters K and (alpha) for use in Gy’s equation for the Fundamental Sampling Error (FSE)–, Duplicate Sampling Analysis (DSA) and Segregation Free Analysis (SFA)–, are described in detail. A case study using identical broken reef material from a Witwatersrand-type orebody was calibrated using the DSA and SFA methods and the results compared. Classically, the form of Gy’s equation for the FSE raises the nominal size of fragments given by dN to the power of 3. A later modification of Gy’s formula raises dN to the power (alpha), the latter term being calibrated with the coefficient K in the DSA and SFA methods. The preferred value of for low-grade gold ores used by sampling practitioners in the mining industry is 1.5. A review of calibration experiments for low-grade gold ores using the DSA and SFA methods has produced values of K that vary between 70 and 170 and values of in the range 0.97 to 1.30. The average value for is shown to be 1, rather than 3 as originally proposed in the classic form of Gy’s equation or the industry-preferred 1.5. It is suggested that for low-grade gold-bearing ores the equation for the FSE should raise dN to a power of 1. Such an equation for the variance of the FSE greatly simplifies the characterization of gold ores, now requiring only the calibration of K for a given mass and established fragment size. The implications of the simplified equation for the heterogeneity test are that, provided the fragments have been screened to within a narrow size range, any particular size will return a value for K that is acceptable for use in the sampling nomogram.

Jan 1, 2017

By B. Aydin, A. S. Aloglu, S. Kahraman, E. Saygin

"The coal strength parameter is used in operations such as the selection and design of mechanical excavators and coal crushing/grinding equipment. However, coring or cutting prismatic specimens from coal for the standard strength tests is difficult, and sometimes not possible. For this reason a method for the indirect determination of coal strength from easy tests would be useful. In this study, the predictability of coal strength from the needle penetration test was investigated. This is a very easy and practical test method. Point load and needle penetration index (NPI) tests were carried out on coal specimens from Çayirhan coalfield in Turkey. The point load indexes were converted to the uniaxial compressive strength (UCS) values by using the general conversion factor. The UCS and NPI values were evaluated using regression analysis. A strong linear relationship was found between the two parameters. The conversion factor for the UCS-NPI ratio is 0.35 for the tested coal samples. It is concluded that the UCS of coal can be predicted from the NPI.IntroductionKnowledge of coal strength is important for the selection and design of mechanical excavators and coal crushing and grinding equipment. Uniaxial compressive strength of coal is used in designing pillar dimensions in room and pillar mining. Coals always contain bedding planes and cleats; they are also brittle and fragile. Therefore, coring or cutting prismatic specimens from coal for the standard strength tests is difficult, and sometimes not possible. For this reason, a method for the estimation of coal strength from easy tests would be useful.The needle penetration test is a nondestructive index test that is applicable both in the field and the laboratory and does not require any special sample preparation. The test has been used for the estimation of physical and mechanical properties of weak or soft rocks (Okada et al., 1985; Yamaguchi et al., 1997; Takahashi, Noto, and Yokokawa, 1988; Uchida et al., 2004; Aydan et al., 2006; Aydan, Watanabe, and Tokashiki, 2008; Aydan, 2012; Erguler and Ulusay, 2007; Park, Obara, and Kan, 2011; Ulusay and Erguler, 2012; Aydan and Ulusay, 2013; Aydan. Sato, and Yagi, 2014). This study investigates the predictability of coal strength from the needle penetration test."

Jan 1, 2017

By J. Y. Foley, K. Eden, A. E. Grosz, C. J. Giles, J. E. Grosz

"Portions of the Icy Cape placer Au district have been described and exploited since the early 1900s. Industrial studies of Au-bearing garnetrich intervals established a 3.5 million troy ounce resource in the western half of the district. This estimate is not compliant with CIM and SME definition standards for Mineral Resources and Mineral Reserves. We note high variability in the textures of sediments and their heavy mineral (HM) content and composition in the district, probably as a function of the depositional environment. Sediments are medium- to fine-grained sands with a valuable HM assemblage that averages 26.0% in a range of 1.1– 72.6%. Valuable heavy minerals (VHMs) garnet, magnetite, ilmenite, rutile, and zircon, but excluding Au, average 7.9% in a range of 1.0–37.6% of the HM assemblage. Trace quantities of uraninite, thorite, monazite, xenotime, and others are noted. Garnets have an average Y content of 726 ppm with a range of 0–2150 ppm. Energy-dispersive X-ray fluorescence confirms compositions commensurate with Ca, Al, and Mg silicates. We provide empirical analytical data and note high variability in the textures, HM content, and compositions as a probable function of depositional environment. Icy Cape District land and resources are owned by the Alaska Mental Health Trust Authority and managed by the Trust Land Office (TLO). IntroductionThe Icy Cape Heavy Minerals (HM) District in Alaska subtends more than 200 km2 fronting the Pacific Ocean and backing to the foot of the Robinson Mountains at about 1700 m above sea level. We classify the district into geomorphic provinces; the eastern region as deltaic (Figure 1) and the western region as coastal plain (Figure 2), based on geomorphologic expressions. The coastal plain is entirely built up of unconsolidated outwash sediments and ancient beach sand deposits."

Jan 1, 2017

By Z. Yang, X. Bian

"The synthesis of 3-hydroxy-2-naphthyl hydroxamic acid (H2O5) as a collector for bastnaesite is described. The flotation performance of H2O5 with respect to bastnaesite was investigated by flotation tests, measurements of the surface adsorption capacity, and polarizing microscopy. The results indicated that H2O5 exhibits superior collecting performance compared with direct flotation recovery of bastnaesite, with recoveries above 90% at pH 8–9. The adsorption mechanism of H2O5 on bastnaesite was studied by solution chemistry analysis and ?-potential tests. The results showed that the adsorption of H2O5 is associated with the types and concentrations of hydrolysis products of rare earth cations on the bastnaesite surface. At pH 8–9, the hydrolysis-dominant components RE(OH)2+ and RE(OH)2 + of the rare earth cations were adsorbed onto the bastnaesite surfaces, which were considered to be the major positive active points and were beneficial to chemical adsorption of the reagents. The pH range of 7–10 was optimum for bastnaesite floatability, and the adsorption of H205 on bastnaesite was by means of chemical adsorption through formation of a five-membered ring chelate. IntroductionThe rare earth elements (REEs) have long been known as ‘industrial gold’ and are widely used in the petroleum, chemical, ceramic, metallurgical, and permanent magnet material industries because of their special physicochemical properties (Chen, 2011; Krishnamurthy and Guptac, 2002; Esquivel, Bohe, and Pasquevich, 2002; Abrahami, Xiao, and Yang, 2015). Demand for REEs is growing in response to continuous advances in science and technology. Currently, most REEs are extracted from bastnaesite ((Ce,La)CO3F) (Chelgani et al., 2015; Yosry, 1990), which is recovered from rare earth ores by flotation. Typically, hydroxamic acids are used as bastnaesite collectors (Xu, 2015; Ren, 1997; Mousumi and Venugopal, 2016). Research into the mechanism of interaction between hydroxamic acids and bastnaesite is important for improving the recoveries of bastnaesite. However, there have been few studies that examine this mechanism."

Jan 1, 2017

By T. G. Maepa

"The creation of mine excavations alters the stress distribution in the surrounding rock mass. In modern mining, resin-grouted rockbolts are used as a means of support in order to redistribute stresses and reestablish equilibrium in the rock mass. The success of resin-grouted rockbolting depends on the design of the system and the correct installation of the support units.The support design and rockbolt installation procedure at a platinum mine in the Bushveld Complex were investigated. A number of issues that resulted in poor installation were identified, including resin admixture, incorrect length and orientation of support holes, over- or under-spinning of the resin, and incorrect rockbolt tensioning. The support design used at the mine was reviewed and its limitations identified. A number of recommendations were made for optimizing the support design by reducing the diameter of the drill bit and reducing the length of the support holes. These changes will enable the mine to use different combinations of resin capsules. Implementation of the proposed changes will lead to a significant reduction in the cost of installation per support hole, as well as improve productivity and safety.IntroductionThe creation of any mine excavation disturbs the virgin state of stress in the Earth’s crust. This results in stress concentrations that interfere with the stability of the rock mass surrounding the excavation. It is essential to modify the internal behaviour of the rock mass surrounding excavations in order to reinforce the ground and stabilize excavations. Resin-grouted rockbolts are extensively used for this purpose. Esterhuizen (2014) stated that when effectively installed, the rockbolt exerts a clamping force and a bonding strength that keeps the rock mass together. This increases the cohesive strength of all discontinuities in the rock mass and enhances the stability of the excavation. Poorly designed and installed ground support is ineffective and constitutes a safety hazard. It is therefore crucial for every mine to ensure that any form of ground support is designed and installed correctly. This research evaluates the installation of resign-grouted rockbolts and identifies challenges and solutions for improved safety as observed at an operating hard rock mine. The support design used at the mine was reviewed and the design parameters optimized. The outcomes will enhance the efficiency of support and minimize the costs associated with the installation of resingrouted rockbolts."

Jan 1, 2017

By J. Witley

"Narrow tabular platinum group element deposits in the Bushveld Complex of South Africa are typically evaluated by diamond core drilling from surface. Several short deflections are drilled from each mother hole in order to obtain multiple intersections at a close spacing (less than 1 m). Examination of the intersections from deflection drilling revealed the importance of these deflections in understanding the representivity of the borehole, obtaining an estimate of the nugget effect, and mitigating the undesirable effect of the high grade variability at the ultra-short range that is a characteristic of these deposits. The use of deflections in estimation was investigated by means of a number of techniques and scenarios in order to find the most appropriate way to use them in an estimate. A significantly improved level of confidence was gained from using multiple close-spaced intersections rather than a single borehole intersection. IntroductionThe Upper Group 2 chromitite layer (UG2 or UG2 Reef) is known for its remarkable geological continuity, being traced almost uninterrupted for tens of kilometres. However, what is often less well emphasized is the high variability in platinum group element (PGE) grade and thickness (and therefore PGE content) and internal reef stratigraphy over very short distances (several metres or even tens of centimetres).This paper examines the application of short drill-hole deflections in evaluating UG2 PGE mineral resources at Marikana in the western Bushveld Complex of South Africa."

Jan 1, 2017

By C. S. Kucukkargoz, A. Bhalla

"The solid-state reduction of ilmenite concentrate with graphite was studied under argon atmosphere at temperatures between 1050°C and 1350°C. The rate of reduction increased with increasing temperature and decreasing particle size, with the maximum extent of reduction found to be 80% at 1350oC with a particle size in the range of -106 +90 µm. The activation energy for the reduction reaction was calculated to be 257 kJ/mole. The trivalent iron oxide was reduced first to divalent iron oxide and then to metallic iron. An annular ring of a partially reduced oxide phase containing metallic nuclei was formed around the core of ilmenite, which grew in size as the original ilmenite core shrank with progressive reduction. The reduction of titanium dioxide also took place during this stage, which produced the Magneli oxides in the form of TinO2n-1. The metallic phase had very high Fe and low Ti contents throughout the reduction, whereas the partially reduced oxide phase adjacent to the metallic phase was high in Ti and depleted in Fe. The metallic phase globules formed during this stage were small and are considered suitable only for leaching and not for other concentration processes. The core of the particle generally retained the composition of the original ilmenite. The purpose of this work was to remove iron and increase the titanium oxide content of the ilmenite to produce a high-titanium containing charge for subsequent smelting.IntroductionThe titanium-bearing minerals ilmenite (FeTiO3) and rutile (TiO2) are the primary natural raw materials used in industry to produce titanium metal and titanium-based products. The common titanium-bearing minerals are ilmenite, rutile, anatase, brookite, leucoxene, arizonite, and perovskite. Although the formula of ilmenite is commonly expressed as FeTiO3, the mineral can accommodate Mn and Mg, which are chemically bound in the form of (Fe,Mn,Mg)TiO3. Ilmenite concentrate can also contain Fe2O3 and Al2O3 in addition to the physically separable oxides such as SiO2 and CaO. The crystal structure of ilmenite is an ordered derivative of the corundum structure with a trigonal-rhombohedral symmetry. Fe2+ and Ti4+ ions occupy the octahedral sites, leaving the tetrahedral sites unoccupied. In each FeTiO3 unit, there are three O2- ions creating three octahedral sites, two of which are occupied by Fe2+ and Ti4+ (Wilson et al., 2005)."

Jan 1, 2017

By M. R. Khalesi, Y. Kianinia, A. Seyedhakimi, F. Soltani

"The feed ore to Agh-Darreh gold processing plant (Takab City, Iran) contains 2 ppm Au, 7 ppm Ag, and 120 ppm Hg. After cyanide leaching of the feed at pH 10.4, 80% of the total mercury (in the form of cinnabar and metacinnabar) goes to the tailings dam. In this research, separation of mercury from the tailings by flotation was investigated. The effects of collector type and dosage, pH, and the number of cleaner stages were studied. The results showed that after two stages of cleaning a 40–62% recovery of Hg at a grade of 14.3% Hg is attainable. Recycle water from a test in which 50 g/t amyl xanthate and 30 g/t pine oil was used in the flotation stage showed no adverse effect on the leaching and adsorption of gold onto activated carbon.IntroductionMercury, most commonly found in the nature as the mineral cinnabar (HgS), is a hazardous substance because of its mobility and toxicity (Kyle et al., 2012). Roasting is the wellestablished treatment method for mercury ores, in which the sulphur is burned and volatilized and mercury recovered subsequently by cooling and condensation. However, for low-grade ores, flotation is mainly applied for primary concentration due to its comparatively low costs, low environmental hazards, and flexibility regarding feed variations (Bulatovic, 2007). Particularly, cinnabar can be easily recovered by flotation using pine oil and a collector such as xanthate (Bulatovic, 2007; Crozier, 1991). Floatability of cinnabar is reduced due to surface oxidation when it is exposed to the atmosphere after crushing. This problem can be eliminated by adding copper sulphate and lead nitrate or acetate. The best pH for cinnabar flotation is in the range of 6.5 to 8.5 according to Erspamer and Wells, (1954), who reported that cinnabar and stibnite can be floated with long-chain xanthate collectors and an alcohol frother, with cumulative recoveries of 97.8% and 94.7%, respectively. Lead acetate was used as an activator."

Jan 1, 2017

By P. J. Le Roux

"Mining companies are under constant pressure to reduce their cost structures to sustain profitability. In mines using an open stoping mining method, dilution often has a significant effect on profitability. At Target mine in South Africa, dilution in some open stopes was found to exceed 10%, falls of ground being a major contributor to the problem. This dilution can reduce the recovered grade from 5.5 to 4.5 g/t, resulting in a potential loss of about R21 million per month based on a gold price of R240 000 per kilogram. In addition to the cost of dilution, the cost of damage to, or loss of, trackless equipment as a direct result of falls of ground in open stopes is significant. Other associated costs include transport, hoisting, secondary blasting, milling, and plant treatment of waste material. Stable open stopes are essential in order to reduce falls of ground. Back-analyses of stope instability at Target mine have indicated that conventional rock mass failure criteria are unsuitable for stope design. An alternative strain-based criterion has been developed, and has proved to be very successful, allowing the stability of open stopes to be calculated reliably. Since its implementation in 2010, dilution and equipment damage have decreased markedly, creating value for the mine. IntroductionMines that make use of an open stoping mining method aim to extract only the ore, leaving the waste behind. Many orebodies have well-defined boundaries between the ore and the waste rock. In such orebodies, the introduction of waste into the ore due to overbreak dilutes the grade. In massive disseminated orebodies, dilution is less problematic. Overblasting, falls of ground, or other causes may result in dilution. A study undertaken in Canada (Pakalnis et al., 1995) found that approximately 51% of all underground metal mines utilized open stoping mining methods and, from surveys conducted at these mines, open stoping operations experienced dilutions of up to 20%, and occasionally more. Dilution of this magnitude has a significant economic impact on any mining venture. Research carried out in Australia by Capes (2009) came to the same conclusion."

Jan 1, 2017

By T. Feroze, B. Genc

"Blind headings in room and pillar coal mines are a major source of methane and coal dust. Most methane and coal dust explosions therefore occur in the blind headings. The primary cause of these explosions is the disruption of the local ventilation system. Line brattice (LB) ventilation systems are used to ventilate blind headings by directing air from the last through road (LTR) into the heading. The amount of air available to ventilate the face of the empty heading depends on the heading dimension, settings of the LB, and velocity of air in the LTR. LBs are commonly installed by underground supervisory staff based on work experience, which may result in ineffective ventilation. The correct installation of LBs remains a challenge.In this study, a validated computational fluid dynamics (CFD) model has been used to analyse the effect of the LB ventilation system variables on the air flow rates close to the face of the empty heading. Full-scale three-dimensional models with various heading heights, heading depths, LB settings, and LTR velocities were simulated. The air flow rates and patterns at various locations inside the heading were analysed. A comparative study was carried out to quantify the effect of each of these system variables on the flow rates close to the face of the heading. Based on the findings, a user-friendly numerical model was formulated that can be used to estimate the flow rate close to the face of an empty heading for different practical settings of the system variables. This model can help the supervisory staff to swiftly implement the ventilation plan according to the regulations and the mine standards. The model can also serve as part of the curriculum for educating future mining engineers."

Jan 1, 2017