Search Documents

By Mark Craddock, Johan Swanepoel

In this paper we present The Ultimate Flotation Cell, a newly developed flotation cell that is proving very popular in the industry. All flotation cells have only one purpose and that is the recovery of the required product, the patented impeller and disperser system of the Ultimate Flotation Cell allows total flexibility in order to achieve the optimal recovery. This ability to tune the cell performance provides the optimization of the ?capture? (collection) stage, all existing models address the need for a wide bubble size distribution (100µm-2 mm) to obtain a better flotation size-by-size, Yoon, 1999,Yoon 2000, Franzidis and Manlapig, 1999. The Ultimate Flotation Cell provides flexible performance optimization. This ability to optimize the flotation regime particular to a specific ore is achieved by the following factors: ? The impeller allows vastly improved air induction rates compared to conventional and sparged cells. This ability to induce and disperse large quantities of air, in a controlled manner, allows the cells to be tuned to give the optimal Sb by varying the rotational speed via a VSD which every cell is fitted with. ? The patented impeller gives a very constant and stable air induction rate, which ensures that the cell?s circulation pattern is constant, giving a very stable surface, allowing optimal froth depth. ? Although conventional dart valve, level control can be offered, great success has been achieved with a simple draft tube/sand relief device. ? The cells have a inlet design similar to the old Denver ?Cell-to-Cell? design, which guarantees the at lease one pass through the mixing zone in each cell. Actual plant performance data will be presented from two plants, one in Zambia and the other in the DRC.

Jan 1, 2007

By E. J. Margi

Deep gold exploration such as is used for Witwatersrand gold deposits is both expensive and time-consuming. This paper provides quantitative guidelines as to the economic optimum number of boreholes and deflections within each borehole for a certain reef characterized by its variability pattern and depth below surface in order to maximize the level of confidence for a fixed drilling budget or to minimize the total drilling cost for a given level of confidence. Portions of the Basal, Vaal, and Elsburg Reefs that show a wide range of variability (sample logarithmic variances of 0,63, 1,05, and 2,06 respectively) are examined at depths below surface ranging from 1000 m to 4000 m over a simulated mining property covering 7000 ha (7000 m by 10000 m). It is concluded that four intersections per borehole are optimum in al the cases considered, which cover the majority of current Witwatersrand exploration, with the exception of the highly variable Elsburg Reef at depths of 1000 m and 2000 m, where boreholes with one and two intersections respectively should be preferred.

Jan 1, 1987

By Z-B. Cheng, X-J. Liu

"Intensive mining of shallow coal seams tends to result in severe subsidence of the ground surface. Surface subsidence is a complex dynamic spatiotemporal process that constantly changes as mining advances. With Liangshuijing coal mine as a case study, 3DEC numerical software was used to simulate the development of the moving subsidence field from open-off cut to full subsidence on the working face. The results demonstrate that the formation of a subsidence field is directly related to the coal seam depth H and the extent of the mine workings. Taking the advance distance of the working face as the unit of scale, the process of surface subsidence can be divided into four stages: micro-change (H/ p), the development of surface subsidence (2H/ p), the formation of a movement subsidence field (3H/ p), and dynamic balance (4H/ p). The changing movement of a subsidence field can be fully described by the characteristics of surface subsidence value, curve slope, and the inflection position. The results provide important technical support for predicting surface subsidence and the temporal–spatial evolution features of mining subsidence. IntroductionChina’s coal output was about 3.52 Gt in 2017 (China National Coal Association, 2018), making it the largest coal producer in the world, accounting for almost half of total world coal production. Coal production and distribution play a vital role in the energy industry of China. However, entire overlying strata, from coal seam to surface, are disturbed as a result of long-term, high-intensity and large-scale mining, causing surface subsidence. This results in groundwater loss, surface desertification, vegetation loss, and mud-rock flows. These issues have become topics of common concern throughout society. According to related research results (Liu 2008), the area of surface subsidence caused by coal mining in China has reached about 600 000 ha, some 0.2 ha (and up to 0.42 ha) of surface subsidence for every 10 000 t of coal produced. Surface subsidence disasters not only damage buildings, water conservancy, transportation infrastructure, and farmland, but also cause adverse effects on individual and community lifestyles, environmental hygiene, and economic development. Deterioration of the ecological environment in mining areas has a long history and is very harmful (Lu, 2015)."

Feb 1, 2019

By C. A. Young, J. L. Bowden

"Cyclic voltammetry experiments were conducted on copper and chalcopyrite (CuFeS2) in the absence and presence of ethyl xanthate, and compared to mass-balanced EH–pH diagrams. The results for copper duplicate those found in the literature and confirm xanthate chemisorption. However, the, results indicate that chalcopyrite oxidizes to chalcocite (Cu2S) and only afterwards is chemisorption observed due to small currents appearing with xanthate. This phenomenon suggests that the mineral's hydrophobicity is induced by more than dixanthogen and copper xanthate. Hydrophobicity was found to be pH-dependent over a range of alkaline conditions (pH 7–11) at narrow potentials (0 to –200 mV). An EH–pH diagram for chalcopyrite with xanthate is presented to illustrate the conditions under which chalcopyrite would be hydrophobic and thereby more thoroughly explain the results in the literature. IntroductionSulphide minerals are generally concentrated from ores by froth flotation, a physiochemical process that induces separation based on differences in hydrophobicity. In this process, a gas is bubbled into a slurry and the minerals that are hydrophobic (water-repelling) adhere to the bubbles and float to the surface while the hydrophilic (water-loving) minerals remain in the slurry. With sulphide minerals, the hydrophobicity is generally established in two ways. The first is by the addition of a collector, which is a heteropolar molecule with a reactive inorganic head group and an inert organic tail. Typically, the head group bonds with the sulphide mineral surface by adsorbtion either chemically (chemisorption) or physically (physisorption) or by complexing with atoms that solubilize somewhat at the surface (surface precipitation). These interactions leave the organic tail protruding from the mineral surface, thereby inducing hydrophobicity. The second method is by oxidation of the mineral surface to form a layer that is metal-deficient/sulphide-rich or comprised of elemental sulphur. Because the layer mimics naturally hydrophobic sulphur, this enables ‘collectorless’ flotation. Furthermore, this oxidation phenomenon adds an electrochemical dimension to the understanding of sulphide mineral flotation."

Jan 1, 2016

By G. W. Healy

The smelting of calcium carbide has always been plagued by eruptions, too often with serious injury y or loss of life. To find their causes, the author calculated an internal energy balance using 1992 data for CaC2 and CaO, and older data for the remaining items. The heat content of the charge, and that of the hot gases formed at the reduction temperature, showed that only a fraction of its heat content can be supplied by these gases. Laboratory data on the electrical resistivity of fine mixtures of coke and non-conductive solids were extrapolated to a commercial carbide charge, and then used to calculate the heat produced by current flowing through the mix from the electrode surface to the hearth, which, under favourable conditions, sufficed to bring the charge to 1900 K and higher, at which temperatures reduction could take place.

Jan 1, 1995

By G. J. Krige

The extent of ground movements and stress concentrations in the vicinity of the reef in the deep mine-shafts used in the South 4frican gold-mining industry have led to the requirement that special tower structures be developed to span the reef intersection zone in several new shafts. So that structural engineers are able to design these towers, it is necessary to model the dynamic behavior of conveyances traversing them in some way, to provide a means to determine the magnitude of the forces generated. This paper describes the development of two such procedures. The first is a numerical method, utilizing a step by- step integration technique to track the motion of a conveyance through a tower. This technique has been implemented in a computer program, and some results are given.

Jan 1, 1995

By L. Gunnewiek

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

Jan 1, 2008

By J P. van Dyk

The dramatic strengthening of the rand against the dollar as well as a decline in quantity and quality of locally available concentrates have had a dramatic impact on Zincor?s operations during the previous two years. Zincor has responded with the implementation of a number of technical improvements to the process to decrease cost and increase revenue and plant flexibility. Among the initiatives is the pre-leaching and pelletising of the zinc concentrate, de-bottlenecking and process improvements in the leach and purification circuits, the introduction of cathode washing and automated cathode stacking in the cell house and the installation of a new furnace to produce pre-alloyed jumbos. This paper will describe these initiatives and others that Zincor have recently taken to stay competitive in changing global base metals market.

Jan 1, 2005

The quality of life in many countries of both the developed and the developing world is strongly affected by the products and processes of mining industries. The first Issue in this new series brings together a set of review articles by leading authorities in the field which, taken together, provide a thorough and detailed survey of many of the key topics of current concern relating to the environmental impact of mining. The level of treatment of most topics is at first introductory but evolves through to the advanced level of current research, backed up by extensive citations of relevant primary literature and other sources. Thus the Issue as a whole will be found equally valuable by students of environmental science and those actively engaged in research related to this theme.

Jan 1, 1995

Financial Times Mining International Year Book 1979. London, The Financial Times Limited, 1979. 712 pp. Price: airmail, U .S. $60,00; surface mail, U .S. $42,00. International Wrought Copper Council. Glossary of terms applicable to wrought products in copper and copper alloys. London, the Council (6 Bathurst Street, Sussex Square, London W2 2SD), 1978. 170 pp. 80 Swiss francs (approximately £25). Council of Mining and Metallurgical Institutions At a meeting of the Council of Commonwealth Mining and Metallurgical Institutions held on 15th January, 1979, it was unanimously agreed that the name of the Council should be changed.. Assaying and analytical techniques This year sees the Diamond Jubilee of the South African Institute of Assayers and Analysts, which held its first meeting on the 3rd of May, 1919.

Jan 1, 1979

By N. Sinclair

"In open pit dozer bulk push operations, the material left resting against the highwall after blasting poses an issue. This is because dozers cannot physically get in behind the waste to begin the bulk pushing process. Instead, an excavator can be used to side-cast this waste for the dozers to access. An alternative technique is to have the dozers ‘side-cut’ the material, which involves the dozers running parallel to the wall, digging out the material, and eventually rotating their blades to begin bulk pushing. Industry practices suggest the latter technique is less productive and economical than using an excavator. However, such excavator sidecasting ‘economic viability’ assumes that smaller/ancillary type excavators are used (i.e. less than 23 m3 bucket capacity). So, what happens if some mine sites are restricted to using relatively larger excavators (> 23 m3 bucket) that are preferred for higher priority digging tasks? When can they avoid using their excavator? This paper explores multiple scenarios that have been designed and developed to simulate data results, which identify conditions in which the dozer side-cutting technique becomes more economically viable than excavator side-casting in terms of decreased unit cost per loose cubic metre. IntroductionOptimizing the cost of waste removal operations is important for the profitability of opencast coal mines. In the past decade, dozer bulk pushing has emerged and taken over from traditional waste removal operations such as dragline and truck-and-shovel methods at various sites around the world (Beatty, 1994). In a typical bulk push operation, once the bench has been blasted, waste is left resting against the highwall, which can either be cleared using a loading unit or by having the dozers ‘side-cut’ the highwall.Dozers perform most effectively when slot dozing side-by-side, perpendicular to the highwall. However, when dozers are required to remove material off the highwall, they must push parallel to the highwall, rather than perpendicular, hence ‘side-cutting’ the material to ensure a clean face. While dozer sidecutting is possible, it has been found that the majority of mine sites use a loading unit in this situation to avoid dozer inefficiency. Other perceived issues with dozer side-cutting include higher maintenance requirements and safety risks to dozer operators working in close proximity to the highwall."

Jan 1, 2019

The following notes have been compiled to assist authors in the preparation of papers for presentation to the Institute and for publication in the Journal. All papers must meet the standards set by the Council of the Institute, and for this purpose all papers are referred to at least two referees appointed by the Council. Although the worldwide readership of the Journal results in a preference for papers in English, the Council treats papers in Afrikaans on an equal basis, but, to meet the needs of the majority of readers, an English summary of some 5OO to 750 words should be provided.

Jan 1, 1984

Mining is a business involving extraction of commodities of value to society from non-renewable resources. Consequently there is only one opportunity to extract ore from the ore body in order to unlock the value potential encompassed in the asset. It is therefore imperative that the maximum value is unlocked during the extraction programme, considering the relative wealth generated for shareholders and society, the sustainability of society, the environment and the operation. The bulk of the value that is unlocked is usually embedded in the initial design process. How do you measure sucess The most common measure of success is the return on investment, which is unlocked during the extraction process. This is usually only determined and locked-in during the study process. Another measure of success is the profitability that is achieved on a monthly basis. A further measure would be the enhancement the asset affords to the share price of the operation. Increasing focus on sustainable development requires that the impact on the society and environment received high priority as well. All these measures are largely encompassed in the cash flow and the discounted cash flows. This paper focuses on the dynamics of the cash flow and the most significant elements influencing return in investment. These include the mine design, production volume, sustainability, risk and valuation techniques. When do you add the most value? There are many different phases and definitions noted by different authors to demonstrate and standardise the study process for new projects. This paper is based on a process with 3 major components namely a conceptual study, a prefeasibility study and a feasibility study.

Jan 1, 2007

By D. Clement

A comparison between hydraulic and pneumatic rockdrills by D. CLEMENT The regulation of compressed-air reticulation systems is very poor compared with that of electrical systems; this means that electrohydraulic rockdrill systems offer greater flexibility, additional power being readily available at the working face. Hydrometallurgy A new journal devoted to all aspects of the aqueous processing of metals is scheduled to appear this year. Entitled Hydrometallurgy, the journal will be published in quarterly issues, one volume per year. Mineral dressing Contributions are invited for the Symposium on Recent Progress in Mineral Dressing in South Africa, which is to be arranged jointly by the South African Institute of Mining and Metallurgy and the National Institute for Metallurgy. Mineraalbereiding Bydraes word verlang tot die Simposium oor Onlangse Vordering met Mineraalbereiding in Suid-Afrika wat gesamentlik deur die Suid- Afrikaanse Instituut vir Mynbou en Metallurgie en die Nasionale Instituut vir Metallurgie gereel gaan word. Rock mechanics The Sixteenth Symposium on Rock Mechanics is to be held at the University of Minnesota from 22nd to 24th September, 1975. The Symposium is the official Symposium for 1975 of the International Society for Rock Mechanics (I.S.R.M.), and the Council for I.S.R.M., consisting of members from 25 countries, will meet during the Symposium. Powder metallurgy The annual meeting on powder metallurgy organized by The Metals Society is this year to be held at the Stratford Hilton Hotel, Stratford-upon-Avon (the notification did not include the date of the meeting). Vacation School The South African Institute of Mining and Metallurgy has great pleasure in announcing its intention of holding a vacation school on the topic of electric-furnace melting. NIM reports Report no. 1681 The determination of sulphur and phosphorus in chromite. Report no. 1687 The viscosities and electrical conductivities of slags associated with the production of high-carbon ferromanganese alloys.

Jan 3, 1975

By N. Hanief

This research involves the investigation of phase transformations in the platinum-chromium coated system. Single-layer 0.1 µm platinum coatings were deposited via electron beam deposition on 99.98 percent pure chromium substrates. Specimens were subjected to systematic heat treatment in a vacuum furnace at 900°C for up to 20 hours. Phase formation and the changes in surface morphology were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM).Both CrPt and Cr3Pt phases are formed during heat treatment for different times at 900°C. Significant changes in the morphology of this coated system were detected after heat treatment at 900°C for 20 hours.

Jan 1, 2012

By S. M. Spottiswoode

A simple method for the application of excess shear stress (ESS) analysis to the mining of planar reefs is examined. The potential for seismicity associated with mining is expressed as the calculated increase in ESS on a regular grid of points 50 m above the reef, and is compared with observed seismicity around a deep-level, relatively geologicaly-undisturbed gold mine. Thirty regions were studied, involving over 2000 seismic events with magnitudes greater than 1,5 on the Richter scale and associated with almost 2 million square metres of stoping. The total seismicity, measured either as the number of seismic events or as the total radiated energy, corelated more closely with changes in ESS than with ERR. The incidence of rockbursts also favoured the ESS model. Corelation coeficients of around 0,8 for seismicity and ESS indicated that the assumptions inherent in the method used are collectively reasonable. The total seismicity in each region was found not to be strongly controlled by the presence of dykes and faults, although numerous individual seismic events were located close to such features.

Jan 1, 1988

In Chapter 1 we mentioned that up to three components are considered to represent the variability of regionalized variables : a deterministic component, a correlated component, and a random component. In Chapter 2 we considered some of the models based on the assumption of randomly distributed values: the random component was assumed to be the only one present. In Chapters 3 to 11, more general but also more complex models were described, based on the assumption that the values were correlated with the possible presence of random noise. In this chapter we introduce a model used to analyse non- stationary data, for which a deterministic component (or drift) must be assumed. This model will be used for estimation purposes, and the corresponding optimal linear estimation procedure is known as universal kriging. The theory of universal kriging is much more complex than the theory of kriging. Fortunately, in the majority of mine valuation problems the drift can be ignored and the simpler form of kriging can be used.

Jan 1, 1978

By A. O. Filmer

An account is given of a study on the non-oxidative dissolution in aqueous acidic solutions of nickel sulphides of different stoichiometric composition, in which a rotating ring-disc electrode was used. The rate of dissolution was found to depend on the potential of the sulphide and the nickel-to-sulphur stoichiometric ratio. A maximum rate for the dissolution of nickel from nickel sulphides containing an excess of nickel was recorded at potentials around -0,2 to -O,3V. The rate decreased markedly at more anodic potentials. For nickel-deficient nickel sulphides, the nonoxidative dissolution rate increased with a cathodic shift in potential. Under open-circuit conditions, a nickel sulphide of a composition approximating Ni ,S. reacted most rapidly. The dissolution rate was controlled by either a chemical or an electrochemical reaction at the electrode surface, had an activation energy of between 50 and 65 kJ.mol-1, and was independent of stirring speed.

Jan 1, 1980

By G. Panopoulos, R. P. King, A. H. Juckes

The flotation characteristics of two South African coals were investigated: one from the Dumacol Colliery in Natal, and the other from Landau Colliery in the WitbankCoal Field. Samples of fine coal (smaller than 1 mm)were studied, the Dumacol coal showing significantly better ash-liberation characteristics than the Landau coal. Neither coal was found to produce satisfactory flotation concentrates, except at very fine sizes. The poor flotation performance can be ascribed to the non-selective flotation of unliberated particles that may contain considerable quantities of ash. Flotation recoveries were greatest for particles between 100 and 200 µ m, and fell of rapidly as the size increased above 200 µ m. Very fine particles were found to float adequately, and acceptable concentrates can be made at comparatively high yields from materials smaller than 75 µ m. The flotation of ultrafine coal was demonstrated successfully in a continuous pilot plant. This result opens the way to a potentially viable industrial process for the beneficiation of ultrafines from the Witbank No. 2 seam, which for decades has been regarded as non-floatable.

Jan 1, 1986

The treatment of gold-plant tailings with ferrous sulphate to remove the cyanide is currently in use, on several gold plants. In some cases there is scope for optimization the process. The present work provides a detailed study of the reaction between cyanide and ferrous sulphate. Optimal conditions for the removal of total cyande required a ph of 5,.5 to 6,5 and an Fe:CN molar ratio of 0,5. Ferrocyanide ion is shown to be unstable In aqueous acidic solution, with rapid oxidation to ferricyanide, (Fe(CN) 6 ), and formation .of Fe(CN)5H2O3- at pH values below 4, The precipitate from the reaction between cyanide and ferrous sulphate consists mainly 01 Insoluble Prussian blue, Fe4[Fe(CNI&!.3,and IS shown to be unstable in the presence of alkaline solution, since it decomposes rapidly at pH values above 7 to form ferrocyanide, (Fe(CN)6 ), in solution and various insoluble iron oxides,

Jan 1, 1992