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By L. Uotinen, M. Rinne, R. Mishra

Underground mining gives rise to geotechnical hazards. A formal geotechnical risk assessment can help to forecast and mitigate these hazards. Frequentist probability methods can be used when the hazard does not have many variables and a lot of data is available. However, often there is not enough data for probability distributions, such as in the case of new projects. The risk assessment is often subjective and qualitative, based on expert judgement. The purpose of this research is to present the use of Bayesian networks (BNs) as an alternative to existing risk assessment methods in underground mines by combining expert knowledge with data as it becomes available. Roof fall frequency forecasting using parameter learning is demonstrated with 1141 sets of roof fall data across 12 coal mines in the USA. The prediction is nearly identical for individual mines, but when multiple mines are evaluated it is difficult to find a single best fit distribution for annual roof fall frequency. The BN approach with TNormal distribution was twice as likely to fit the observed data compared to the Poisson distribution assumed in the past. A hybrid approach using BN combining multiple probability distribution curves from historical data to predict annual roof fall is proposed. The BN models can account for variability for multiple parameters without increasing the complexity of the calculation. BNs can work with varying amounts of data, which makes them a good tool for real-time risk assessment in mines.

Jun 1, 2021

By N. Mutemeri, T. -L. Field, M. Chuma

The categorization of artisanal and small-scale mining has a significant impact on perception and understanding of the sector, particularly from a livelihood perspective. Several developing countries classify different types of artisanal and small-scale mining based on legal status. Given the nature such activities, the tragedy of the commons theory has been applied to understand the inevitable environmental, economic, sociocultural, safety, and health negative externalities – which are products of informality and illegality. Consequently, formalization is a panacea to sustainability. This article aims to offer a conceptual organization and foundational knowledge for characterization of artisanal and small-scale mining. It seeks to identify existing literature on the subject to avoid replication and acknowledge other scholars. Moreover, the article aims to place the study within the context of existing literature, establishing relationships with other studies and why the research is necessary. This paper pinpoints gaps left from other studies in so far as the characterization of artisanal and small-scale mining is concerned. Thus, reviewing literature abetted in finding similarities and differences on how artisanal and small-scale mining is defined from a scholarly and legal basis. The paper ascertains major claims made by earlier research on this topic, such as environmental impacts, the lack of adequate regulatory framework, and presents querying and probing questions lacking from other studies.

Jul 10, 2024

By D. C. Krige

The estimation of the tonnage and grade of payable ore in a mine and the correct policy of selective mining based on such estimates, is of vital importance to the mining engineer it is surprising, therefore, that more attention has not been devoted on the Witwatersrand to the scientific improvement of mine valuation methods. At present these methods consist almost entirely of the application of simple arithmetic and empirical formulae guided by practical experience, and ignore the many advantages to be gained from a careful statistical analysis of the behaviour of the gold values. The science of statistics has expanded rapidly during the last two decades and its value as a powerful and indispensable tool is now recognized not only by research workers and scientists but also, ever-increasingly, by the commercial and industrial world. This being the case it is noteworthy that in a mining field such as the Rand with its highly developed and advanced mining methods, singularly little attention has been paid to the analysis of mine valuation problems on a modern statistical basis. This omission is even more striking when cognizance is taken of the wealth of sampling data concerning the gold ore which is available and of the far-reaching decisions and deductions constantly being based on such data. Some contributions have however been made from time to time towards the application of statistics to mine valuation on the Rand (References Nos. 7, 8, 9, 11, and 12), but none of these have been generally applied in practice and a systematic practical approach based on clearly deemed fundamental concepts still appears to be lacking. The object of this paper is, therefore, to define these statistical concepts and to indicate briefly the lines along which statistical methods can be applied profitability in solving some of the existing problems and in improving the general standard of mine valuation on the Rand For this purpose a knowledge of mathematical statistics is essential, but as this paper is primarily intended to provide the mine valuator with a practical introduction to statistical application in his field, the mathematics is confined to a short annexure, together with references from which details can be obtained.

Jan 1, 1994

By G. T. van Rooyen

In this overview of materials engineering, the author, drawing on his long experience from his student days until the present (emeritus professorship), briefly recounts the main developments in this field: dislocation theory, fracture problems, and the development of alternative materials such as ceramics and polymers. He then takes a look at the future, in which he foresees a greater demand for materials engineers, and leading roles for universities and technikons in collaboration with industry.

Jan 1, 1996

By P. L. Crouse

"SynopsisFluorine – in the form of hydrofluoric acid, anhydrous hydrogen fluoride, elemental gaseous fluorine, fluoropolymers, volatile inorganic fluorides, and more – has played, and still plays, a major role in the nuclear industry. In order to enrich uranium, the metal has to be in the gaseous state. While more exotic methods are known, the standard and most cost-competitive way of achieving this is by means of uranium hexafluoride (UF6). This compound sublimates at low temperatures, and the vapour is enriched using centrifugal processes. The industrial preparation of uranium hexafluoride requires both elemental fluorine gas and anhydrous hydrogen fluoride (HF). HF is prepared by the reaction of sulphuric acid with fluorspar (CaF2). Fluorine gas in turn is prepared by the electrolysis of HF. Yellowcake is first converted to uranium tetrafluoride (UF4), using HF, after which the compound is treated with fluorine to yield UF6. After enrichment, the UF6 is reduced to UO2 for use in fuel elements in pellet form.South Africa has the largest reserves of fluorspar internationally, and is the third largest producer after Mexico and China. Fluorine technology has many associated difficulties, because of the reactivity of fluorine and the toxicity of HF. The main barriers to entry into the fluorochemical industry are thus the abilities to produce both HF and F2. Both these substances are produced locally, at the industrial scale, at Pelchem SOC Ltd. Should South Africa contemplate developing its own nuclear fuel cycle as part of the awaited new-build nuclear project, it will be imperative to leverage the existing skills with respect to fluorine technology, resident at both Pelchem and Necsa, for this purpose. This paper summarizes the fluorochemical skills developed locally over the past several decades, and suggests strategies for maintaining the technology base and developing it for the next generation of scientists and engineers.IntroductionFluorine chemistry has always had a very close relationship with the nuclear industry. Although the first mention of fluorspar was recorded in the sixteenth century, and the fundamentals had been well-developed by the Second World War, it was only during the Manhattan Project (Banks et al., 1994), when almost unlimited funds were made available for the large-scale industrialization of fluorine and related compounds, that the technology took off. Expertise in both the chemistry and the engineering aspects of fluorine is essential for the design and running of several of the unit processes in the nuclear fuel cycle."

Jan 1, 2015

By L. Thomas, A. Argyn, B. Mbao, G. Longo Banza

Since the first application of solvent extraction as part of the hydrometallurgical processing of copper, several studies have been carried out to optimize extractant formulations. In 2006, Solvay developed the ACORGA® OPT series of solvent-extraction reagents to optimize copper transfer by use of a blended formulation containing both aldoxime and ketoxime as well as selected modifiers. The incorporation of selected modifiers in these blended reagents resulted in increased copper transfer, due to the interaction between the modifier and oximes within the blend. By changing the ketoxime concentration and ratio of modifier to aldoxime, the strength of the formulation was optimized to enhance copper transfer and improve Cu:Fe selectivity. This formulation is well known in the African region under the ACORGA® OPT5540 name and provides the best performance at the conditions of agitated leach plants with pregnant leach solutions that fluctuate in Cu grade and pH. This paper discusses advantages of using ACORGA® OPT5540 in the Copperbelt

Jan 1, 2023

By S. Purushotham, Y. R. Murthy, M. Narasimha, S. K. Tripathy, M. Kumar

Spiral concentrators are gravity-based separators widely used to beneficiate coal, heavy minerals and beach sand. It consists of a helicoid trough that spirals downward in the helical configuration around an axial column. The particle segregation takes place based on size and density under the influence of gravity as the particles spiral down within the thin water layer. In the last century, most design modifications of this equipment were based on trial and error based lab-scale experimentations and empirical approach. The use of Computational Fluid Dynamics (CFD) has gained interest in the past two decades to understand the underlying flow physics in the spiral concentrators. In this paper, we used CFD to model the fluid flow and investigate the particle segregation inside a conventional LD9 spiral concentrator. Firstly, the Volume of Fluid model was used to resolve the liquid-air interface. The liquid depth and flow field predictions for varying flowrates were validated against the experimental literature data. One-way coupled VOF-LPT model was then used to describe the particle dynamics in the spiral flow field assuming dilute particulate flow. Moderate dense particulate flow (20 vol.%) was then modelled using the Algebraic Slip Mixture (ASM) model. Four particle-phases representing particles of different sizes of dual-density were simulated, and the component particle segregation was analysed. Keywords: Spiral concentrator, two-phase flow, multiphase, discrete phase model, ASM model

Jan 1, 2020

1. Mintek reports The folowing reports are available from Mintek, Private Bag X3015, Randburg, 2125 South Africa. They are available at R25 (plus R3,25 GST) per copy to South African addressees, and US$25 per copy (including airmail postage) to addressees elsewhere. Report M91D A mineralogical investigation of samples from the Renosterkop tin prospect near Upington, by M.J. Southwood. First issued Jul. 1983, reissued May 1989. 16 pp. Report M256D The upgrading of Mamatwan manganese ores heavy-medium separation, by P. W. Overbeek. First issued Apr. 1986, reissued May 1989. Report M299D A mineralogical investigation of samples from the Eenzaamheid cobalt-molybdenum deposit, by C.D. de Nooy. First issued Jan. 1987; reissued May 1989. Report M301D The evaluation of manganese metal powder by automatic image analysis, by E.J. Oosthuyzen. First issued Feb. 1987, reissued May 1989. 13 pp. Report M311D Mineralogical and beneficiation studies of ore from Lutzputz, by R.N. Guest and C.T. Logan. First issued Mar. 1987, reissued May 1989. 13 pp. Report M314D The beneficiation of a sample of magnesium ca/crete, by L. Jonker. First issued Apr. 1987, reissued May 1989. 13pp. Report M369 The determination, by flow-injection analysis, of thiocyanate, by E.A. Jones and M-J. Hennings. Jun. 1989. 7pp. Report M389 A spectrophotometric method for the determination of zinc by flow-injection analysis, by D.E. Barnes and RA. Jones. Jul. 1989. 15 pp.2. Recent publications Pumps-principles and practice. Available from K. Myles & Associates CC, P .0. Box 2212, Northclif 2115. :200pp. R99 including GST. Standard handbook of hazardous waste treatment and disposal, edited by H.M. Freeman. Bergano Book Co., P .0. Box 190, Fairfield, CT 06430, USA. 1120 pp. US$130.Quality control handbook, by J. Juran and F. Gryna Jr. Bergano Book Co. (address as above). 4th 00. 1536pp. US$125.Refractories in the manufacture and transport of pig iron. Verlag Schmid GMBH, P.O. Box 6609, 7800 Freiburg, West Germany. DM 100. The user-computer interface in process control, byW.E. Gilmore, D.I. Gertman, and H.S. Blackman. London, Harcourt Brace Jovanovich Ltd, 1989. " 312pp. $29.Aluminum alloys-contemporary research and applications, edited by A.K. Vasudevan and R.D. Doherty. London, Harcourt Brace Jovanovich Ltd, 1989. " 676 pp. " £90.3. TMS publications issued recently The folowing publications are available from The Minerals, Metals & Materials Society, 420 Commonwealth Drive, Warendale, PA 15086, USA (Telephone: (412) 776-9000, Telex: 9103809397, Fax: 4127763770). Advances in magnesium alloys and composites, by H. Paris and W.H. Hunt (eds.). 145 pp. $65. Arsenic metallurgy-fundamentals and applications, by R. Reddy (ed.). 515 pp. $104. Casting of near net shape products, by Y. Sahai (ed.). 7oopp. $155.Continuous casting of non-ferous metals and alloys, by H.D. Merchant, D.E. Tyler, and E.H. Chia (eds.). 360 pp. $90.Dislocations and interfaces in semiconductors, by K. Rajan, D. Ast, and J. Narayan (eds.). 210pp. $75.

Jan 1, 1989

By N. Tatalias, P. Ilunga, M. Lampi, J. Edwards, K. Valkama, M. Nicolle, D. Samal

"Developing a greenfield mining project is a complex exercise: doing so in an increasingly volatile, uncertain, and ambiguous global economy adds significantly to this complexity. In the context of an elevated cobalt price, this paper outlines the metallurgical and process development of the Mutoshi copper–cobalt project for copper cathode and cobalt hydroxide production in the Democratic Republic of Congo. Chemaf has a long production history on the Copperbelt, a region widely perceived to be tough to operate in. This history stretches back to 2001, during which time the company has developed two copper–cobalt processing facilities. The experience gained in the development and operation of these two facilities has been used extensively in the Mutoshi copper–cobalt project. The metallurgical test work, process design, and project delivery approach are presented. Additionally, the decisions taken to minimize risk and maximize upside to the project are discussed. IntroductionChemaf (Chemicals of Africa), a mining company located in Katanga province of the Democratic Republic of Congo (DRC), has been operating since 2001 with two major copper– cobalt processing facilities: the Usoke and Etoile plants. In 2016, Chemaf acquired the Mutoshi mine, which belonged to Gecamines and had been explored by Anvil Mining since 2004 under a joint venture with Gecamines. Chemaf appointed African Mining Consultants Ltd (AMC) to undertake a preliminary economical assessment, then develop a JORCcompliant Mineral Resource estimate and finally a full life-of mine feasibility study. Both a Mineral Reserve and Mineral Resource were developed and the final life-of-mine feasibility study is to be published shortly. A metallurgical test work programme was initiated and carried out by Chemaf’s research and development laboratory with assistance from the Chemaf process team. After completion of the initial test work, Chemaf developed a process design criteria document for a 20 kt/a copper cathode and 8 kt/a cobalt in hydroxide production plant, followed by a flow sheet and supporting METSIM mass balance. As the drilling progressed, the plant design capacity was revised to 16 kt/a cobalt production. The life of the mine at this production rate is over 40 years."

Nov 1, 2018

It is widely accepted that the type of grinding media has an impact on the grinding chemistry and subsequent flotation behaviour of the sulphide minerals being separated. There are countless laboratory investigations demonstrating that inert grinding media produces more oxidizing pulp potentials, reduced levels of grinding media corrosion products, and superior concentrate grades and valuable metal recoveries. However, taking these results to industrial scale has proved difficult. This paper provides details of the protocol developed and used during a high-chrome grinding media plant trial. It describes the test regime employed to measure changes in pulp chemistry as well as concentrate grades and recoveries to produce a statistically meaningful result. The work also highlighted the need for close cooperation between the metallurgists on site and the researchers conducting the trial. To demonstrate the protocol, data gathered during a plant trail in a PGM concentrate will be presented describing the changes in pulp chemistry and metallurgical response observed.

Jan 1, 2012

By N. Mulaudzi

The use of SO2/air gas mixtures as an oxidant to precipitate Mn from Co(II) leach liquors was investigated. The effects of SO2/air ratio, pH and temperature on Mn precipitation were evaluated. It was found that the use of SO2/air gas mixtures resulted in significantly higher Mn precipitation kinetics compared to using air or pure O2 alone. The SO2/air ratio was varied from 0% to 6% SO2(v/v) in air and similar Mn removals were achieved at 0.75% to 3% SO2 at pH 3. The solution pH was varied from pH 2 to pH 4; Mn precipitation did not increase considerably from pH 2 to pH 3, but increased significantly at pH values higher than pH 3. Cobalt co-precipitation also increased as pH increased, with 1% Co co-precipitation at pH 3. An increase in temperature from 30°C to 60°C also increased Mn precipitation and 100% Mn precipitated at 50°C. Cobalt co-precipitation also increased significantly with an increase in temperature. An activation energy of 25 kJ/mol was calculated from the Arrhenius plot, which is an indication that the precipitation reactions were both chemically and diffusion controlled. XRD analysis showed that Mn precipitated in the form of Mn2O3 instead of MnO2 that was predicted from thermodynamic data. SEM and XRD analysis also revealed that the precipitate consisted mainly of gypsum or bassanite (99%), with the Mn containing phase (< 1%) distributed within the gypsum phase. The co-precipitated Co reported to the Mn phase. Keywords: manganese precipitation; SO2/O2 gas mixtures; cobalt solutions.

Jan 1, 2009

By А. Klemyatov, T. Vologdina, U. Gordeeva, S. Zbinets, А. Kalugin, N. Rozhdestvenskiy

The plants integrated in the PhosAgro group of companies perform processes from scientific research to the project, from ore mining to shipment of fertilisers and feed additives to consumers. An extensive process chain maintains smooth interaction at all stages from research to production. As an example, the paper shows the revamp of two beneficiation plants (ANOF-2 and ANOF-3), requiring a comprehensive approach to task solving. The intention of the revamp was to increase the total yield of apatite and nepheline concentrate, taking into account the gradual decline in the quality of ore being processed and ensuring the yield stability of final products during re-equipment of the plants. At ANOF-3, the crushing and grinding cycle was modernised, the production of nepheline concentrate was implemented, and the capacity of apatite flotation, dehydration, and drying was increased. At ANOF-2 a new process chain was implemented for the production of apatite concentrate in workshops previously used for the production of nepheline concentrate. The main building was withdrawn from operation, where ore grinding, apatite flotation and apatite concentrate thickening had been carried out. The total increase in apatite concentrate yield at two beneficiation plants was 1.3 times. A further increase in concentrate production is planned. Keywords: Apatite, nepheline, fertilisers, beneficiation, flotation, column flotation machines, revamp, fine screening

Jan 1, 2020

By M. de Paiva Bueno, G. Barakos, S. Luukkanen, K. Luolavirta

Lifelong development of skills and knowledge of mining professionals has been recognised worldwide as a challenge for the development of a sustainable mining sector. Practical training and learning over the mine value chain are among the key components of this knowledge building. However, the number of available mining sites for continuous education in real-life conditions is limited; also the specifications for practical training are not clearly defined. The project MINETRAIN was developed to (i) evaluate the potential of the shortly-closing Pyhäsalmi Mine, in Finland, as an educational and training underground facility, and thus, prolong the utility of the existing modern mine site, and to (ii) develop and test practical training programs for mining and mining industry related professionals. Pyhäsalmi facilities enable training among all disciplines related to the overall mine value chain and hence, the project has potential in providing education for sustainable management of any phase of mining operations. The philosophy underpinning the MINETRAIN approach to mining activities is to assist the clients in minimising the technical and financial risks by providing a competitive and skilled personnel asset while optimising the value drivers in their operations. As a first major step of the project, a pilot training course, involving basic-level online theory and hands-on training at the Pyhäsalmi mine site, was undertaken in summer 2019. Feedback from the pilot test group of mining professionals has proved to be very positive. The comments from the participants strongly emphasised the added value of the practical onsite training for improved understanding in the large scale picture of mining on the entire value chain. As a second phase of the project, a new test course was launched in June 2020. The second MINETRAIN course focuses on new technologies and digitisation in mining. Keywords: Lifelong learning, mining education, mine value chain, research and education mine, educational research project

Jan 1, 2020

By S. Langea, H. Lieberwirth

Impact crushers are common machines in comminution plants. Their high size-reduction ratio and relatively simple design, make them a preferred tool even when subjected to harsh wear, and producing a large quantity of fines in some applications. Until now the alignment of the operational parameters was an operator’s responsibility. Due to the random process characteristic this is mostly done based on empirical values and sensor data, such as power consumption. This paper describes a new approach for online process monitoring of the horizontal-shaft-impact crusher. The application of robust, low-cost acceleration sensors enables the permanent observation of the process characteristics. The operational and evaluation methods are determined on the basis of experiments. Subsequently the recorded measurements are analysed in regards of throughput, rotational speed and product particle size distribution. Occurring signal characteristics are described based on physical and technical principles. The measured data of the acceleration sensors at varying operation conditions provide insight in the course of process. The accurate utilisation yields the determination of the preferential process conditions providing the best balance between the pros and cons of an impact crusher. Both the experimental method and the data processing is discussed from a scientific perspective, displaying a completely new approach for the operation of impact crushers. Keywords: Impact crusher, acceleration sensors, data processing, particle size

Jan 1, 2020

By M. M. Ali, C. Musingwini, R. A. Phillips

The long-term open-pit mine production scheduling problem (OPMPSP) is typically solved in two broad stages. The first stage entails optimisation of the ultimate pit limit, which delimits the economical final pit and maximises the undiscounted value of the deposit. The second stage entails optimisation of the long-term open-pit mine production scheduling, which maximises the discounted value of the deposit. The long-term OPMPSP is a type of an NP-hard problem, such as the travelling salesman problem (TSP), because it is intrinsically complex to solve since it incorporates both hard and soft constraints. Therefore, metaheuristic approaches have been used to find global optimum solutions to the long-term OPMPSP. This paper presents a metaheuristic approach utilising a dual interchange algorithm (DIA) to solve the long-term OPMPSP. The DIA is a parent algorithm which supervises two subservient algorithms, namely, simulated annealing (SA) and Tabu search (TS). The DIA selects the better solution generated in each run from the two algorithms, and simultaneously penalises the algorithm that produced an inferior solution, while rewarding the one that produced a better solution. The DIA was tested on the three-dimensional Arizona Copper Deposit (KD) dataset, which is publicly available for research purposes from the online MineLib repository. It was set to generate net present values (NPVs) in five-minute intervals and the solution improved until it plateaued at about 30 minutes of runtime. The NPVs compared favourably to those obtained on the same KD dataset but obtained over 24-hour runtimes, when solved using simulated annealing and Tabu search algorithms, and the NPV generated from the work of Muñoz (2012) using the modified TopoSort as found on the MineLib repository at the time of this study. Therefore, this paper demonstrates that DIAs can be developed and used to solve the three-dimensional long-term OPMPSP.

Sep 1, 2021

By T. Könighofer

Processing of copper-cobalt orebodies in Africa?s Copper Belt has received much recent attention with various flowsheet options being developed specifically for the refining of cobalt. The upfront leach and copper refining routes are well understood whereas the refining of cobalt is more complex, requiring numerous impurity removal steps to produce high purity metal. This paper describes an investigation into one of the possible processing steps in the refining of cobalt, namely, cobalt solvent extraction. The paper emphasizes the importance of upstream impurity removal to achieve the required cobalt solvent extraction feed composition. 18% (v/v) Cyanex 272 in an aliphatic diluents is used as the organic phase. The pH profiles in the various stages are evaluated in order to obtain a raffinate containing <10mg/l cobalt and with a low magnesium content reporting to the stripping section. The pH profile is also used to minimize the impurity deportment to the cobalt electrolyte. The effect of adding a pre-neutralization stage before feeding the organic phase to the extraction circuit is investigated. Zinc build-up in the stripping stages is also looked at. It is recommended for the purpose of this study that four extraction stages at an O:A ratio of 1 with a pH profile from 4.9 to 5.7 be employed. The pH is controlled with 40g/l NaOH. A pre-neutralization stage is required, where the organic phase is contacted with 10 M NaOH. Two scrubbing stages are recommended at an O:A ratio of 40, using the cobalt electrowinning advance electrolyte as the scrub liquor. Three strip stages are to be employed at an O:A ratio of 0.67.

Jan 1, 2009

By L. Zhou, J. Qiu, M. Tang, J. Wang, G. Dai

Coal spontaneous combustion in longwall gobs is a major concern in coal mines. In comparison to other hazards, this phenomenon is difficult to detect. Fifteen factors influencing coal spontaneous combustion in longwall gobs were identified from the literature. The logical relationships between these factors were evaluated and quantified by decision-making trial and evaluation laboratory (DEMATEL) and interpretive structural modelling (ISM) methods. A four-level hierarchical structure model was established. The research shows that combining DEMATEL and ISM can reveal the key factors that influence coal spontaneous combustion in longwall gobs and establishthe interactions and relationships among these factors. The results can provide the basis for preventing and controlling coal spontaneous combustion in longwall gobs.

Jun 10, 2024

By H. Ruthert

An understanding of wear in systems conveying solids is extremely important from the standpoints of design and economics. The lifetime of any bulk solids-handling system depends on the type of solids present and the operating parameters of the transportation system. The relationship between wear in backfill pipelines on South African gold mines and the transportation system&apos;s operating parameters is well understood. However, the effect of the transported solids on the pipe wear is less well understood, because of an inability to characterize particle sharpness. The sharpness of the particles, together with their size and hardness, is responsible for the aggressivity of particles, or their ability to cause damage and wear. This paper presents a novel method for the characterization of particle sharpness. The results presented rank particles according to the sharpness of their surfaces.

Jan 1, 1993

By T. Könighofer

Processing of copper-cobalt orebodies in Africa?s Copper Belt has received much recent attention with various flowsheet options being developed specifically for the refining of cobalt. The upfront leach and copper refining routes are well understood whereas the refining of cobalt is more complex, requiring numerous impurity removal steps to produce high purity metal. This paper describes an investigation into one of the possible processing steps in the refining of cobalt, namely, cobalt solvent extraction. The paper emphasizes the importance of upstream impurity removal to achieve the required cobalt solvent extraction feed composition. 18% (v/v) Cyanex 272 in an aliphatic diluent is used as the organic phase. The pH profiles in the various stages are evaluated in order to obtain a raffinate containing <10 mg/[l] cobalt and with a low magnesium content reporting to the stripping section. The pH profile is also used to minimize the impurity deportment to the cobalt electrolyte. The effect of adding a preneutralization stage before feeding the organic phase to the extraction circuit is investigated. Zinc build-up in the stripping stages is also looked at. It is recommended for the purpose of this study that four extraction stages at an O:A ratio of 1 with a pH profile from 4.9 to 5.7 be employed. The pH is controlled with 40 g/[l] NaOH. A preneutralization stage is required, where the organic phase is contacted with 10 M NaOH. Two scrubbing stages are recommended at an O:A ratio of 40, using the cobalt electrowinning advance electrolyte as the scrub liquor. Three strip stages are to be employed at an O:A ratio of 0.67.

Jan 1, 2009

By N. F. Mashinini

Optimization of current control systems, proper maintenance and efficient training of personnel are recommendations made to control the amount of dust that underground employees are exposed to on a daily basis in the coal mining industry. This dissertation forms as part of Sasol Mining?s commitment to protect the health and safety of their employees by suppressing and controlling dust at their mines. This study aims to understand the relationship among mining processes, exposure to dust and dust suppression control measures. The research phase of the project was done at the Sasol Mining Secunda complex where underground visits were undertaken to investigate current control systems and also new systems that are being implemented by Sasol Mining. This work was important because it helped determine the sources of dust underground and also to identify the shortcomings of current control systems and to test the efficiencies of the new systems implemented at Sasol Mining. The most important result of the research work was the identification of which underground operators were exposed the most to dust as this assisted in designing a dust suppression system for the areas where these operators worked. The main conclusions of this study are that the current control systems are sufficient for controlling dust and ensuring dust compliance if they are used efficiently and maintained properly.

Jan 1, 2008