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By V-P. Takalo, M. Natsvlishvili, M. Hicks, S. Khizanishvili

"The complexity of copper-gold ores leads to large variations in recoveries and concentrate grades in the processing plant. Detailed chemical and mineralogical studies revealed considerable variation in the ratios of chalcopyrite, chalcocite, and oxidized copper minerals in the ore types studied. The end-member ore types are chalcopyrite-dominated and chalcocite-dominated, while most of the ore types plot between these end-members. In addition, increasing amounts of copper oxide and sulphate minerals result in a decreased response to flotation. Good recoveries and concentrate grades can be achieved from the chalcopyritedominated ore type, while the more altered chalcocite-dominated ore type is more challenging to enrich. IntroductionRich Metals Group (RMG) Copper in Georgia (Figure 1) produces copper-gold concentrates from two open pit mines, Madneuli and Sakdrisi, both located in the Bolnisi mining district in South Georgia. RMG and Outotec began a cooperative project with the aim of improving the recoveries and metal grades in concentrate by gaining an increased understanding of the ore variability and developing more efficient procedures for ore blending, grinding, and flotation. This type of mineralogy-led approach has already been used for other complex ores such as iron oxide copper-gold ores (Hunt, Berry, and Bradshaw, 2011), for iron ores (Lund, Lamberg, and Lindberg, 2013), and for Kupferschiefer ore deposits (Rahfeld et al., 2018).The project started with process audits and mineralogical and chemical characterization of process samples, followed by detailed chemical and mineralogical characterization of six different ore types with simultaneous flotation test work on the same samples. Since neither the recoveries nor the concentrate grades correlate with the head grades of the ores, the modal mineralogical composition, together with the ore hardness, proved to be the most promising approach in developing the geometallurgical classification of these ore types."

Apr 1, 2019

By H. F. Fuls

Skorpion Zinc, an integrated zinc mine and refinery located in the south of Namibia, has a production capacity of 150 000 t/a of special high grade (SHG) zinc. The Skorpion zinc oxide resource will be depleted by 2017. Extensive exploration drilling for additional zinc oxides was conducted without success. With the abundant availability of zinc sulphide concentrates regionally (Black Mountain and Gamsberg in the Northern Cape or Rosh Pinah Zinc and new deposits in the Rosh Pinah region) the life of the operation can be extended by processing of zinc sulphide concentrates. The leach kinetics of zinc sulphides is vastly slower than for oxides, preventing the processing of zinc sulphides in the existing process under current conditions, and Skorpion Zinc faces the challenge to identify a suitable zinc sulphide treatment process that can be integrated with the existing plant. Various zinc sulphide processing options were identified through an extensive literature search and non-viable options were eliminated. Mass and energy balances were established for potential options and an economic evaluation (including capital and operating cost estimation) was conducted to identify a suitable process. It is concluded that ferric leaching of sphalerite in a sulphate medium under atmospheric or pressure leach conditions are suitable processes for Skorpion Zinc. These processes present advantages over all other zinc processing options when elemental sulphur is preferred as the final deportment for sulphide sulphur. Both these processes can be integrated into the existing refinery and will be able to process concentrates with a wide composition range.

Jan 1, 2013

By R. H. Matjie, J. R. Bunt, C. A. Strydom

"A number of conventional and advanced analytical techniques (proximate and ultimate analysis, low-temperature oxygen-plasma ashing, X-ray diffraction, X-ray fluorescence spectrometry, coal petrography, and lightelement electron microprobe analysis) have been integrated and crosschecked to provide detailed characterization of coals from the Highveld coalfield in South Africa, as a basis for better understanding of the mineralogical and chemical properties of the individual coal sources that are blended as feedstocks for combustion and carbon conversion processes. The techniques included methods to quantify the abundance and composition of the mineral matter (minerals and non-mineral inorganic elements), and also the abundance and chemical composition of the individual macerals in the individual coals concerned.Kaolinite is the most abundant of the minerals in the coals studied, with lesser but still significant proportions of quartz, mica and/or illite, dolomite, calcite, and pyrite. Small but variable proportions of anatase, goyazite, and siderite are present in some coal samples. Electron microprobe analysis, based on a special configuration for light-element study, shows that the vitrinite contains less carbon and more oxygen, and has significantly higher concentrations of nitrogen and organic sulphur, than the inertinite macerals in the same samples. Minor proportions of organically-associated inorganic elements, including titanium, were also identified in some of the maceral components.A comprehensive knowledge of the minerals and non-mineral inorganic elements in the coals used for feedstock preparation, obtained by integration of data from these advanced analytical techniques with more conventional analyses, may be of benefit in understanding the processes that take place during coal utilization, and also in avoiding or ameliorating some of the operational and environmental problems that may occur in different sectors of the coal utilization industry."

Jan 1, 2016

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 Z. Nzimande

The Constitution of the Republic of South Africa advocates the importance of sustainable economic development and justifiable environmental consciousness by business. The government needs to ensure that every citizen of the Republic has access to an environment that is protected, pollution free, and sustainable by enacting certain regulations. However, there are more than 5 700 derelict and unrehabilitated mines of all types in South Africa. Former asbestos operations were among the first to be targeted for clean-up under the programme instituted by the Department of Mineral Resources (DMR), owing to the proven direct impact of asbestos pollution on health. This paper seeks to investigate the challenges faced by the coal sector as far as mine rehabilitation and closure is concerned. For the purpose of this paper rehabilitation is defined as per the Chamber of Mines Rehabilitation Guidelines publication, which defines rehabilitation as putting the land impacted by mining activities back to a sustainable and usable condition. Some of the current rehabilitation challenges are technical skills (know-how), leadership focus, poor planning, cost saving initiatives, and the government's lack of capacity to enforcement rehabilitation requirements. It is imperative that mining companies identify rehabilitation as a critical strategic pillar that directly influences license to operate. The case study evidence indicates that relevant policies, appointment of accountable people, sufficient leadership support, and the correct choice of rehabilitation equipment can assist to improve the rehabilitation and land management challenge.

Jan 1, 2012

By D. Limpitlaw, A. Alsum, D. Neale

"Ecological footprint analysis (EFA) was first described in 1996 as a measure of carrying capacity appropriated by human activities. EFA is a resource and emissions accounting tool designed to track the demand on the biosphere’s regenerative capacity. Ecological footprints are increasingly used as indicators of organizational and corporate environmental performance and product sustainability. There is a compelling argument to develop an EFA tool for mining companies.To determine the size of a mine’s ecological footprint, land requirements for all categories of consumption and waste discharge must be summed. This land is only made up of the ecologically productive land and water in various classes (cropland, pasture, forests etc.) required on an ongoing basis to provide all energy and material resources consumed and absorb wastes.A challenge in conducting an EFA for a mine is the shortage of accessible data. Undertaking an EFA for a corporation or individual site entails compiling consumption and emissions data (which can be used for other reporting applications). The footprint results themselves highlight the most critical aspects of an organization’s impact on the environment and provide a platform for focusing actions and for educating the workforce to improve their contribution to best-practice operations. This paper discusses the benefits and challenges of undertaking an EFA for a mining company, and provides examples of the various components of ecological footprints associated with mines, as well as showing how an EFA can be used to understand and communicate some of the impacts associated with mining activities.IntroductionFundamental biophysical and economic limits are now being experienced in many countries around the world. Herman Daly, a former World Bank economist, described this scenario as ‘uneconomic growth’, where the costs of growth exceed the benefits (Daly, 2005). This occurs when the economy’s expansion encroaches excessively on the surrounding ecosystem, sacrificing natural capital. Under such conditions the sacrificed natural capital is more valuable that the resulting economic growth. Consequently, the world faces largescale threats to sustainability and especially to the viability and continued existence of the ecosystems that support human settlements (El Zein et al., 2014). In recognition of this sustainability imperative, mining companies are increasingly concerned with their ecological footprint (EF)."

Jan 1, 2017

Metso Minerals Process Technology Asia-Pacific (MMPT-AP) has been working with many mining companies worldwide performing `Mine to Mill' or Process Integration and Optimisation (PIO) studies. MMPT-AP has developed a proven methodology to improve the efficiency of the mine-mill interface and gain maximum benefit. The PIO methodology involves rock characterisation, mathematical modelling and simulation to generate a list of operational and control changes for both the mine and concentrator. Following the methodology, the list of recommendations is developed relatively easily; the more challenging part depends on the company. Success of a PIO project relies on the ability of an organisation to implement change - both operationally and culturally: the human element. When a PIO project is started, there is initial interest and commitment from the company. But how can this be maintained? How does an operation know if the benefit continues? MMPT AP is now developing long-term relationships with clients to ensure that the increased production and improved efficiency continues. Direct and indirect measurements are used to determine the key factors involved and to understand the cause/effect relationships. Simulation tools also can be used to compare current with recommended practices - so when material properties vary over time, the benefits can still be quantified. PIO is about empowerment: by measuring and understanding what parameters affect concentrator performance, the site personnel now have the knowledge to make a difference. Rather than simply reporting variable or poor concentrator performance, operations can predict when production will be affected and put controls in place to prevent it from happening. This requires support and commitment from the company or `buy in'. Ensuring this buy in continues is the challenge facing every company involved in PIO work - but the benefits are well worth it. This paper will review MMPT-AP's experiences in implementing PIO projects in the long term: from both the consulting and operational viewpoints. MMPT-AP's involvement with a number of companies will be discussed as examples of what works and what does not.

Jan 1, 2007

Palabora Mining Company is operating a copper block cave mine in the Limpopo Province of South Africa. The mine was developed in the late nineties with a target ore reserve of 220 million tonnes of carbonatite at 0.69% copper. At 30,000 tonnes per day the operation had an estimated life of mine of approximately 23 years. Cave induced open pit side wall failure occurred in late 2004 with 130 million tonnes of waste reporting to the bottom of the open pit. This failure resulted in potential sterilization and dilution of the ore reserve and subsequent reduction in life of mine. Physical and numerical modelling indicated potential losses of up to 30% of the original ore reserves. Cave Management tools based on throughput principles are utilized to manage the failed waste ingress and ensure an optimum life of mine. Extracting the maximum rate possible, as soon as draw points are commissioned, with the view of achieving the highest production in the short term, is any mining operation?s goal as more money is required sooner. This approach, of course, improves the cash flow but presents a risk in the cave propagation profile as overall draw control is compromised. At Palabora it is evident from a Mineral Resource Throughput Management (MRTM) point of view that maximum production in the short term is not the solution. If high production rates are achieved and the profile of the cave is not manage correctly, this results in failed waste reporting to draw points earlier with adverse effects on grade. This would effectively and significantly shorten Palabora?s Life of Mine. The applications of good MRTM principles are required to assist the value chain for sustained profitability. The process commenced with change management paving the way for a better understanding and a holistic view for all role players.

Jan 1, 2007

By C. I. Ware

The phrase ?back to basics? is used to describe the fundamental principles and philosophies on which a successful mining operation is based. At Richards Bay Minerals (RBM), ?back-to-basics? (BTB) has been implemented as a continuous process to probe operational functions with a view to increase production without capital expenditure. It also ensures that the fundamentals of dredge mining are understood and adhered to. BTB is based on the principle that people drive organizations, necessitating an interactive implementation approach. At the RBM mine this entails a three-pronged approach, namely practical training, teamwork initiatives and the use of lean Six Sigma methodology. It is the latter on which this paper will focus. The lean Six Sigma methodology is successful in identifying, managing and documenting BTB projects, while team work initiatives are integral to successful project implementation. This paper describes two examples of how the Six Sigma methodology can be applied to a dredge mining operation. The first example focuses on the improvement of Mining Pond Echo (MPE) plant throughput by reducing the lost opportunity (non-production) due to tails downtime. The project was successful in increasing plant throughput by 4.5%. This was achieved by increasing the tails disposal system availability by running MPE as a four tails lines operation and focusing on causes of tails production downtime. Subsequently, the tails system at MPE is no longer the production bottleneck. Second, the Six Sigma methodology was successfully applied at Mining Pond Charlie (MPC) to increase the primary dredger throughput by 4.6% through focusing on the dredging technique and maintenance issues. This project highlighted the need for trend analyses to ensure an effective dredging technique, coupled with simple production documentation, which also ensures a focus on maintenance. Keywords: Back to basics, Six Sigma, training, teamwork, throughput improvement, tails, dredger.

Jan 1, 2007

By H. W. J. P. Neomagus, J. R. Bunt, T. S. Mthombo, C. A. Strydom

"Low-cost calcium lignosulphonate (CL), which is a byproduct of the wood pulping industry, was investigated as a potential binder during laboratoryscale pelletization of inertinite-rich high-ash coal fines from the Highveld Coalfield of South Africa. Coal-binder mixtures containing between 1 and 15% calcium lignosulphonate were prepared, pressed, and ultimate, proximate, porosity, XRD, and XRF analyses obtained. It was found that increased pressure during pelletization results in increased attractive forces, due to increased interparticle contact areas. FTIR analysis showed that chemical interactions occur between coal fines and the binder, as evidenced by the formation of new C-O ether-type bonds. The presence of moisture during pelletization enhanced surfactant activity of the binder. Chemical interactions between the coal and the binder seem to be mainly electrostatic, driven by Ca2+ from the calcium lignosulphonate, which may act as a bridge between the anionic parts of the binder and the surface of the coal. IntroductionCoal has over the years remained South Africa’s major energy source, with over 90% of the country’s electricity being produced via coal-fired processes (Arndt et al., 2016). Sasol’s coal conversion technology alone provides more than 40% of South Africa’s liquid fuel requirements (van Dyk, Keyser, and Coertzen, 2006). The production of high-grade coal requires the processing of run-of-mine (ROM) resources by a combination of processes which include crushing, screening, and washing (Radloff, Kirsten, and Anderson, 2003). These processes result in the generation of coal fines (< 0.5 mm) which, until recently, have been discarded into slimes dams (le Roux, Campbell, and Smit, 2012). Several issues are associated with slimes dams, among which are the costs of transportation of these fines from the place of origin to the discard point (often a considerable distance), and the potential environmental effects due to seepage of toxic materials into surrounding ecosystems (Clausen, 1973).Consequently, utilization of these coal fines is an area of great interest. Mechanical densification of fine coal by means of pelletization and/or briquetting to larger sizes for use in technologies that require lump coal, such as chain-grate stokers and fixed-bed gasifiers, has been shown not only to reduce environmental risks (Mangena et al., 2004), but also to significantly reduce storage and transportation costs (Mani et al., 2001). Pelletization is the process by which solid particles are consolidated into uniform, usually hard, impact-resistant agglomerates, rendering them useful as a fuel with sufficient calorific value for domestic and industrial utilization (Finney, Sharifi, and Swithenbank, 2009)."

Dec 1, 2018

By V. L. Nkuna, S. R. Amos, T. Naidoo

"Ivanhoe Mines’ Kamoa copper project is a recently discovered high-grade copper sulphide deposit in the Katanga Province of the Democratic Republic of Congo. The mineralization identified to date within the resource is typical of sedimentary-hosted stratiform copper deposits and comprises three distinct units: supergene, mixed, and hypogene mineralization. Since 2010, various metallurgical test work campaigns have been conducted on drill core from different areas within the deposit in line with resource expansion. The most recent bench-scale flotation test work has shown positive repeatable results. The work was conducted on a composite sample of drill core from the southern part of the Kamoa resource. The sample is representative of the first four to five years of planned production, when Ivanhoe Mines intends to produce clean, highgrade copper flotation concentrate. A detailed test work roadmap developed from first principles for the campaign led to an optimum flow sheet for treating the Kamoa mineralization. Copper recoveries of 88.3%, at a concentrate grade of 39.0% copper, were achieved using a composite sample — an improvement on the previously published 85.9% life-of-mine average copper recovery indicated in the November 2013 Kamoa Preliminary Economic Assessment. IntroductionThe Kamoa project is a newly discovered, very large, stratiform copper deposit with adjacent prospective exploration areas within the Central African Copperbelt, approximately 25 km west of the town of Kolwezi in the Democratic Republic of the Congo (DRC) and about 270 kilometres west of the provincial capital of Lubumbashi. Ivanhoe Mines holds its 95% interest in the Kamoa copper project through a subsidiary company, Kamoa Copper SA Limited SPRL, and DRC government owns 5%. The project location is indicated in Figure 1.In January 2013, a new independent mineral resource estimate ranked Kamoa as Africa's largest high-grade copper discovery and the world's largest undeveloped highgrade copper discovery. At this time, Ivanhoe Mines had estimated discovered Indicated Mineral Resources of 739 Mt grading 2.67% copper, containing 43.5 billion pounds of copper, and Inferred Mineral Resources of 227 Mt grading 1.96% copper, containing 9.8 billion pounds of copper, as demonstrated in the Preliminary Economic Assessment (PEA) (AMC, 2013). A 1% copper cut-off grade and a minimum vertical mining thickness of 3 m were applied in each classification."

Jan 1, 2016

By C. G. Carey, M. P. Mullins

BHPBilliton is a large (US$32bn market capitalization) diversified mining group. Significant organic growth is planned through the development of a number of mining, processing and oil and gas projects, totalling some US$5.2bn over the next three years. The investment standards underpin the capital approval process, and incorporate the requirements for range and risk analysis of key input variables, including mineral resources. Public reporting codes for mineral resources and ore reserves (such as JORC) stipulate deterministic reporting of estimates, but are generally silent on any requirement for range or risk assessment, although they acknowledge the risk and uncertainty in the production of resource estimates. In contrast, public reporting of petroleum reserves allow for the use of either deterministic or probabilistic estimation, and for the latter, mandate the level of confidence required for proven versus probable reserves. Conditional simulation techniques, popular in the petroleum industry, provide an ideal tool forrange and risk assessment of the range of outcomes of key resource parameters, such as tonnagesand grades. Examples of a diamond deposit and of a porphyry copper deposit are presented. The understanding and quantification of mineral resource risk through a technique such as conditional simulation provides quantified information on the potential upside or downside. These techniques should be more widely utilized in the high-risk minerals extraction industry. Keywords: mineral resources, conditional simulation, risk, capital investment standards, BHPBilliton.

Jan 1, 2003

By E. Spicer

X-Ray diffraction (XRD) provides useful information about the composition of an ore sample in terms of quantification of crystalline phases and amorphous content. The use of new, fast detection systems in XRD creates the opportunity to use this technique in modern process control. In the analysis of heavy mineral sands, XRD can identify the main mineral phases, such as ilmenite FeTiO3, rutile TiO2, Zircon ZrSiO4and quartz SiO2, and any other minor components present, such as anatase TiO2, magnetite Fe3O4, haematite Fe2O3or monazite (Ce, REE)PO4. Quantitative analysis is possible by various classical methods such as straight line or polynomial calibration with standards, but modern quantification analysis techniques such as Rietveld analysis (Bish and Howard, 1988) are attractive alternatives, as they do not require any standards or monitors. These methods offer impressive accuracy and speed of analysis. The Rietveld method compares calculated versus experimentally derived X-ray powder diffraction patterns for the sum of all crystalline phases. Another analysis technique offering great benefit to mining industries is cluster analysis. Enormous amounts of XRD measurement data are generated during the process control and material evaluation. New ways of handling such vast amounts of data are required to produce meaningful information for the end users. Cluster analysis greatly simplifies the analysis of a large amount of data from different processes or different raw materials, and automatically sorts closely related scans of an experiment into clusters and marks the most representative scan of each cluster as well as outlying patterns. The use of cluster analysis to evaluate the XRD data allows fast and reliable tracking of the process. It is the most economical procedure to have automatic data evaluation without involving any dedicated personnel in the process. Details of the techniques used, sample optimization methodologies, results, data precision and limitations will be discussed. The approach has potential as a relatively inexpensive, reliable tool, useful in the characterization of heavy minerals sand materials.

Jan 1, 2007

By H. Bhikha

The minerals industry is committed to the principles of sustain-ability. Reducing water consumption is a priority area, especially for regions of water scarcity. This paper presents a systemic optimization of the water balance of the Skorpion Zinc refinery with the aim of reducing water consumption. An Aspen Plus simulation of the process is used. The validity of the simulation is tested by measuring key output variables and comparing results to plant data. A number of water minimization scenarios are investigated, Including unit operation and circuit configuration changes. The scenarios leading to the largest reduction in water consumption are through the full recycle of treated effluent water, which results in water savings of up to 19%. Reducing process water and/or recycling of untreated water is prohibited by the build-up of trace elements, which affect product purity. The Skorpion process already features a highly optimized water balance, with unit operational changes merely resulting in a shift in the water balance. Consequently, the largest area for improvement is through the re-use of effluent water. Keywords Skorpion zinc water usage, process optimization, sustainability.

Jan 1, 2011

By C. D. Winkler

Vanadium-based sulphuric acid catalyst has been utilized to oxidize SO2 to SO3 since the early 1900s. This versatile product displaced the expensive and easily poisoned platinum-based catalyst in nearly all applications by the 1930s. MECS has been manufacturing the vanadium-based catalyst since 1925 and today is the leading supplier in the world of sulphuric acid catalysts in a variety of forms. Currently, MECS has worldwide customer/technical support for the catalyst as well as a dedicated catalyst manufacturing plant in Martinez, California. MECS also has a strong technical and research and development programme dedicated to creating new and improved products and services. This paper will describe some of the technical details of vanadium-based sulphuric acid catalysts as well as offering a unique look into how caesium-promoted MECS catalysts can be used in single and double absorption acid plants, and off-gas plants running on irregular gas feeds, to reduce emissions and preheater run times. An update on MECS technical services extended for use in characterizing converter performance is also presented.

Jan 1, 2009

By S. R. Xie, S. Gong, E. P. Li, S. S. He, Y. J. Sun, S. J. Li

"Based on the complicated geological production conditions and abnormal strata behavior of the fully mechanized caving face No. 102 in the Xinyang Coal Mine, we analyze the breaking and forming process of distinguishing key block structures in close spaced coal seams. This analysis establishes an integrated mechanical model of these distinguishing structures. Furthermore, the horizontal force TAB generated by downward key blocks A and B is quantified, as is the Pressure PG exerted by key block B on caved gangue. Finally, the interaction mechanism is revealed. Analysis of the results using Mathematica reveal the following: 1. Both TAB and PG exhibit approximately inverse relationships to coal pillar width b; 2. TAB exhibits an approximately exponential relationship with mining height M of which the base is greater than 1; 3. PG exhibits an approximately arctangent relationship with mining height M. Combining these results with field observations, we conclude that the area in the vicinity of supports 100#–120# in the upper area of working face No. 102 is the likely zone of abnormal strata behavior. Thus, this area was classified as a key control area. Based on these results, the graded support control technique is proposed. Application of this technique in the field resulted in a reduction in the rate of hydraulic support system malfunction from 47% to 7% in the key control area. In addition, during times of periodic mining pressure, the roof caving height value never exceeded 0.3 m and the maximum spalling depth never exceeded 0.2 m. Overall, the results indicate that this new technique has markedly increased the stability of surrounding support rock material. IntroductionClose-spaced coal seams are widely distributed in China, and mining proceeds from the uppermost to the lowermost seam (Zhang et al., 2008). In the case of coal seams in close proximity, a particular set of risk factors becomes pertinent. These include disturbance of lower seams during the mining of overlying ones and the decrease in mechanical stability of lower coal seams following repeated movement of key blocks in main coal seam roofs. This inevitably results in behaviour such as heavy wall spalling and support damage to fully mechanized caving faces in lower-lying coal seams, which necessitates a significantly increase in the measures to support surrounding rock material (Zhang et al., 2010; Huang et al., 2013; Xie et al., 2013)."

Jan 1, 2016

By M. J. Kanda

"The design of rock slopes in the planning and operation of open pit mines and for road and rail cuttings requires the evaluation of their stability. This is commonly done using two well-established methods – limit equilibrium and numerical modelling. The research described in this paper compares the outputs of analyses using these two methods with regard to factor of safety and probability of failure, taking into account technical factors associated with each method and other factors such as material parameters and their variabilities. Results show that technical factors such as number of slices and slip circles, number and type of finite elements, and the stress reduction factor can all affect the results of stability analyses. Factors not taken into account in limit equilibrium analyses, such as dilation, in situ stress, and locked-in stresses can affect the outputs significantly. The research has focused particularly on the predicted location of the failure surface, the resulting volume of failure and, most significantly dependent on this volume, the predicted risk associated with slope failure. The results presented show that there is good agreement between the outputs of the two methods regarding factor of safety and probability of failure. However, the same is not the case with regard to volume of failure and hence risk, which can be very dependent on the methods of analysis and their input parameters. The research is not exhaustive, and there are many other factors that could affect the results of slope stability analyses that were not investigated. Some such factors are mentioned in the paper.IntroductionThe design of rock slopes in the planning and operation of open pit mines and for road and rail cuttings requires the evaluation of their stability. The traditional method of stability analysis used limit equilibrium (LE) methods, and this approach continues to be used. Numerical modelling (NM) packages are now also commonly used in slope stability analyses. The outputs from these analyses provide the factor of safety (FOS) and probability of failure (POF) of the slope. Since the capabilities of the two approaches are different, there can be some variations in FOS and POF outputs and in the predicted location of the failure surface. These variations can affect the predicted volume of failure, and this could in turn have a significant effect on the risk associated with the potential failure (Read and Stacey, 2009). Researchers such as Chiwaye and Stacey (2010) have found that LE analyses underestimate the predicted failure volume, unlike NM methods."

Jan 1, 2016

For the past 12 years, the Universities of Stellenbosch and Cape Town have hosted an annual symposium to discuss research topics in Minerals Processing. Since 1987, this meeting has been held under the auspices of the Western Cape Branch of the South African Institute of Mining and Metallurgy, and has enjoyed much national and international support. In 1993, in place of the usual Symposium, the Branch and Universities collaborated with CSM Associates Ltd and Minerals Engineering Journal is organizing the international Minerals Engineering &apos;93 Conference in Cape Town.

Jan 1, 1993

By Maggi Loubser

"In a technologically advanced era, where process control is accurately maintained within the smallest error margins, and accuracy and precision are continuously improved, sampling is still left to the lowest paid employee in the company without training him or her properly to understand the relevance and importance of the task. In this paper the objectives of sampling in a process control environment is discussed and an attempt is made to link it to the theory of sampling. Some of the practical problems associated with implementing theoretical sampling principles in an industrial environment will be elucidated and some examples given on how compromises are made. Different methods of sampling will be discussed with real life examples from different manufacturing industries."

Jan 1, 2014

By S. Botes, H. van der Merwe

While the refractory lining contains the process on a steady-state basis, the tap-hole must provide a channel for transport of molten materials at discreet intervals, with thermal cycling as routine. The tap-hole introduces a discontinuity in any lining, and this fact can lead to failure in the region around the tap-hole before general lining failure occurs. Hence there is a need for a rapid and reliable tap-hole repair technique that can be readily implemented in conjunction with all types of linings. The UCAR®V Repair supplied by GrafTech is a durable solution capable of repairing all types of lining designs and has been extensively utilized in the ferroalloy industry. More than 20 UCAR®V Repairs have been successfully performed in South Africa alone. This paper describes the system in general and reviews recent repairs and their unique challenges.

Jan 1, 2014