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A General Meeting and Colloquium was held in Kelvin House, Johannesburg on Wednesday 29th September, 1971. The theme of the Colloquium was "The Ferro-alloy Industry". Prof D. D. Howat (President) was in the Chair. The meeting was attended by 106 delegates and was opened by the President at 10.05 a.m. OBITUARY The President: "It is my sad duty to announce the death of G. C. Needham, Fellow, who joined the Institute in 1966 and passed away on 27th September, 1971. As a mark of respect to the memory of the deceased and in sympathy with the bereaved I would ask you all to rise and observe a few moments silence." MEMBERSHIP The President: "I have much pleasure in announcing that the names of the following candidates, having been published in accordance with By-Law 5.2.2, Council has elected them to membership of the Institute. Fellows: Richard Lloyd Blandy, Brian Roger Borton, Brian Teversham, Peter Donald Dickson. Members: Frederick Brian Peacock, Peter John Stacey, Kenneth Niles Thanstrom, Byron J. Hayley, Ian Flemming Buchan, Abraham Hercules le Roux. Graduate: Ian William Coy. Students: Peter Boesley J ames, Kenneth Brian Perel. TRANSFERS From Member to Fellow: Cecil Eugene Fivaz, Peter Edwards. From Student to Graduate: Roy Stavely Traviss. From Student to associate: William Mitchell. I welcome the new members to the Institute and congratulate those members who have been transferred to a higher grade. COLLOQUIUM The first paper, presented by Mr S. Selmer-Olsen, Consulting Metallurgist, Amcor Limited, on 'Trends in Ferro Alloy Production' was published in the May issue of the Journal and comprised information and data relating to new developments in ferro alloy production in various parts of the world. This was followed by a paper-'Conductivity and Viscosity Properties of Slags produced in ferro-alloy manufacture' by D. 1. Ossin et al. This was a record of laboratory test work on slags containing both lime and magnesia, corresponding with the composition of slags encountered in the production of ferro chrome alloys when a dolomite flux is employed. The third paper-'Review of the work of the Pyrometallurgical Research Group of N.I.M. and Metallurgy Department, Wits.' presented by Dr P. R. Jochens, leader of the Research Group, outlined the progress made on ten different research projects presently under way in the Department of Metallurgy. These projects range from studies of the kinetics and mechanism of the reduction of chromite ores through the determination of the activities of MnO in slags to phase studies and melting point determinations in the alloy systems Cr-Fe-Si-C and Cr-Fe-Si. A new feature of this Colloquium was the introduction of the discussion panel composed of four or five individuals known to have special knowledge or interest in the subject under duscussion. Mr J. J. Coetzee was chairman of the first panel, Professor D. D. Howat of the second and Dr R. E. Robinson of the third. During the discussion of Mr Selmer-Olsen's paper an interesting contribution was made by Mr Jack Hayley of Transalloys (Pty.) Limited who pointed out that the lowest power cost in the U.S.A. was that from the TV A at 6 mils per unit (0,43 cents S.A.) while costs from other sources were 7 to 8 mils per unit (0,50 to 0,57 cents S.A.) He also referred to the use of 'pile sintering' of ore fines plus coke at certain ferro alloy plants in the V.S. and to the recent practice of 'graphitising' the paste used for Soderberg electrodes. The last session in the afternoon was devoted to a group discussion on 'Practical problems in Arc Furnace Operation', Mr H. R. Reid of Middelburg Steel Alloys (Pty) Limited occupying the chair, members of the panel being Mr J. Meintjies (Rand Carbide Limited), Mr J. Benn (Amcor) and Mr E. J. Jackson (Transalloys (Pty.) Limited). Mr Reid initiated the discussion by talking of the design and composition of electrode shoes, mentioning the use of the 85/15 Cu/Zn alloy and the comparison of hollow shoes and shoes cooled by tubes. Mr Meintjies discussed electrode management with particular reference to breakages, and dealt with casing and fin design and the welding of fins. Mr Benn dealt with aspects of closed top furnace operation with particular reference to the control of eruptions in the furnace and indicated that preheating of the raw materials might be well worth considering together with the development of a system for the detection of the water vapour present. Mr J ackson was concerned with shells, linings, refractories and tap holes. He deprecated the use of oxygen for opening the tap hole emphasising how uncontrolled use of oxygen led to loss of shape of the tap hole and quite severe burning out of the front hole resulting in time and labour in repairs. A notable feature of the Colloquium was the free discussion 'from the floor' of the hall. Many valuable and highly pertinent contributions were made spontaneously and usually in reply to some controversial topic raised by the discussion group.

By S. J. Moema, M. G. Maruma, L. A. Mampuru, M. E. Maja

"The most commonly used high-chromium white cast iron (HCWCI) is the hypoeutectic white cast iron that contains 2–3.5 wt.% C and 10–30% Cr. This type of material relies on hard, brittle M7C3 carbides to impart good wear resistance. Due to its good wear resistance, this material has found application in the mining industry and cement industry. However, it has low fracture strength and this challenge led to research aimed at refining the microstructure. This was done by the addition of niobium in the range between 0.1 and 0.6 wt.%. In the as-cast condition, the addition of niobium was found to increase the fracture strength due to the finer eutectic microstructure. The hardness was also found to have increased slightly compared to the reference alloy with no niobium additions. Low fracture strength after heat treatment was observed in the Nb-added HCWCI, which is believed to have been caused by the precipitation of secondary carbides and the transformation of the matrix from austenite to martensitic. IntroductionFor the past few years Mintek has been involved in a project in which a number of alloys have been identified for grinding media applications. The high-chromium white cast iron (HCWCI) alloys were among the alloys researched for this application. The knowledge acquired from the grinding ball media research has now been extended to mill liners, which have traditionally been made of manganese-, chromium- and chrome-molybdenum steels. The replacement of worn mill liners costs the mining industry a significant amount of money and this has led to a need for continuous research to prolong the life of the liners. During milling operations, liner wear has an adverse effect on the capacity of the mill, the energy efficiency and milling efficiency and finally leads to relining, to replace worn liners."

Jan 1, 2016

By N. J. Alderman, D. J. Clowes, N. I. Heywood

The effects were studied of the presence of comminuted flint on the rheological characteristics of chalk slurry pumped through a 92-km long pipeline from Kensworth Quarry to Rugby Cement Works in the UK, and their impact on the pipe flow conditions. Flow curves were measured for 63different chalk slurry samples; these were described by the Bingham plastic model. In addition to observing trends in the yield stress parameter and plastic viscosity in the model with variations in both flint concentration and dispersant additive, use was also made of slurry viscosity values at a reference shear rate of 60 s-1for the pipe flow. It was found that chalk slurry viscosity decreases with increasing flint content up to 10% by weight for a given additive concentration, and increases with increasing additive concentration from 0.7 to 1.0%, for a given flint content. The pipeline flow regimes were identified using the critical value of the Bingham Reynolds number for laminar flow breakdown. For Bench 11 (quarry bottom) chalk slurries, it was observed that all sections of the pipeline operate in the turbulent flow regime for the nine different formulations and for the three pipe diameters used along the pipeline. However, this was not always the case for Bench 1(quarry top) slurries. It was therefore recommended that chalk slurries prepared from Bench 1 should not be used because of the strong likelihood that laminar flow conditions will occur owing to the presence of higher clay concentrations within this bench. This, in turn, will lead to an unsafe operation of the pipeline because of the potential for coarse particle settling. Likewise, blending of chalk from Bench 1 with the lower benches such as Bench 11 could be problematic and this requires further experimentation.

Jan 1, 2007

By J. T. Nel

The Kroll process is the traditional method of producing zirconium metal by reduction of zirconium tetrachloride with magnesium metal. This paper discusses the production of zirconium metal in a plasma reactor. Anhydrous low-hafnium ZrCl4 and Mg metal were fed continuously to a 30 kW non-transfer plasma reactor at a rate of 0.31 kg.h-1. Due to losses in the system the recovery of crude product was 77.5 %. After purification to remove unreacted feed material and MgCl2 by leaching, >98 % pure zirconium metal powder was obtained. The overall recovery of purified Zr was 74 %. The conversion efficiency of the process was 95 %.

Jan 1, 2012

By P. H. Botha

An account is given of the procedures used by the South African Iron and Steel Industrial Corporation (Iscor) for tests on the flotation of coal fines, and some of the beneficiation problems encountered with coal from Durnacol, Grootegeluk, and the Soutpansberg area are discussed. These, and other South African coals differ from overseas coals in that they contain a high percentage of fixed ash, which means that they have to be crushed more finely for liberation and that they then contain more fine material (smaller than 0,84 mm). In addition, the coal from the three areas mentioned occurs in fine layers and seams, and contains many intergrown particles.

Jan 1, 1980

By A. Koursaris, Y. Turan

The object of this study was to investigate the i1Jfluence of nitrogen on the structure and properties of AISI 310S steel. Experimental ingots of the steel with nitrogen contents of up to 0,525 per cent by weight were prepared, hot-rolled, and tested after various treatments. The rollability of the material was adequate. The yield strength, tensile strength, hardness, and fatigue properties of the new alloys improved with increasing nitrogen content. The impact properties improved slightly. Empirical equations were developed for the calculation of the yield and tensile strengths, as well as the difference between these two properties, with increasing nitrogen content.

Jan 1, 1995

Council and Standing Committees - 1982/83 President: Prof. A. N. Brown Vice Presidents: Prof. R. P. King and J. D. Austin Honorary Treasurer: Prof. D. G. Krige Immediate Past President: G. Y. Nisbet Members of Council: B. C. Alberts, R. H. English, P. T. Fewell, C. E. Fivaz, J. S. Freer, Prof. G. G. Garrett, J. J. Geldenhuys, Dr A. K. Haines, P. N. Harris, H. E. James, Dr B. K. Loveday, Dr J. Lurie, D. G. Malan, G. Pienaar, B. E. Protheroe, Dr 0. K. H. Steffen, G. C. Thompson, Dr H. Wagner, Dr P. T. Wedepohl. Chairman, Witbank/Middelburg Branch: H. C. van Zyl.

Jan 1, 1983

By M. A. Belokrys, F. O. Milovich, D. D. Aksenova, V. A. Ignatkina, V. A. Bocharov, A. A. Kayumov

Copper remains one of the most sought-after metals in the industry. Tennantite (Cu12As4S13) and tetrahedrite (Cu12Sb4S13) that occur in pyrite copper, copper-zinc and polymetallic ores are an additional reserve for increasing technological parameters of flotation. Pyrite mass (85% and more) has similar flotation properties to other sulfide minerals, and imperfection of reagent regime is a common problem that occurs during quality copper concentrate processing. Due to tennantite's and chalcopyrite's differences in flotation properties with butyl xanthate at pH > 10, tennantite often reports to the flotation tails. Hight alkalinity of the medium increases the oxidation level of sulfide minerals, thus increasing the concentration of S2O3 2-, SO3 2- SO4 2-. At processing facilities in the Russian Federation, the concentration of thiosulfate ions in pulp is in the range of 0.5 to 1.5 g/l and higher, which leads to a decrease in flotation activity of the tennantite. The effect of butyl xanthate (as standard), thionocarbamate, dithiophosphate and M-TF (a mixture of dithiophosphate and thionocarbamate) on monomineral (tennantite and pyrite) flotation in the presence of sodium thiosulfate was studied. The variable parameters of the "thiosulfate-collector" flotation complex were thiosulfate concentration (100-900); pH (8-12,5). The scientific methods included contact angle for hydration assessment; TEM for surface studies; UV spectroscopy and iodometric titration for solubility control. Comprehensive studies have established a connection between the concentration of thiosulfate ions and tennantite flotation selectivity. Flotation activity of tennantite is higher at pH 8 with a thiosulfate concentration under 300 mg/l. Pyrite remains active with butyl xanthate under the same conditions. TEM images of the surface films of the collectors on pyrite were acquired at pH 8. The MTF provides the biggest difference in adsorption, wettability and flotation activity between tennantite and pyrite at pH 8 and thiosulfate concentration under 300 mg/l, in comparison with butyl xanthate. The results of the research will be applied to improve selective reagent regimes of tennantite minerals flotation. Keywords: Tennantite, pyrite, chalcopyrite, sphalerite, flotation, sulfhydryl collectors, thiosulfate, adsorption, mechanism, reagent regime

Jan 1, 2020

By Piotr M. Kapias

Keywords: extraction, lead refining, Pb-Tl solutions, PbCl2-TlCl solutions. The theoretical part of the paper presents an analysis of the conditions of Tl extraction from Pb using different extractants and determines the activity coefficients in liquid solutions of Pb-Tl and PbCl2-TlCl. The dependence of the solution activity coefficients upon the composition and temperature is presented in the form of Krupkowski and Krupkowski-Fitzner equations. An analysis and evaluation were made of the influence of the methods of PbCl2 introduction into a Pb-Tl solution upon the efficiency of the Tl extraction process under thermodynamic equilibrium conditions. The analysis made it possible to formulate relevant equations describing the dynamics of the process of Tl extraction from Pb under stirring conditions as well as under the extractant injection into the liquid Pb-Tl solution conditions. In the part concerning experimental work, results are given for tests on the Tl extraction process from Pb-Tl liquid solutions of initial Tl content of approximately 0.05% mass using PbCl2 or, alternatively, Cl2(g) conducted in laboratorial scale. The tests made it possible to establish the influence of time, temperature, mass and the method of introducing the extractants into the liquid upon the level of Tl extraction from a Pb-Tl solution. Labels used in the text. WT1m - TI content in metallic phase, % mass WT1s - TI content in chloride phase, % mass wpTlm - TI content in metallic phase in initial state, % mass W°Tlm - TI content in metallic phase in equilibrium conditions, % mass m°m - initial mass in metallic phase mm - mass in metallic phase mPbC12 - lead chloride mass fed to the system MPbC12-TIC1 - mass in chloride phase MPb - lead atomic mass, g/mole MT1 - thallium atomic mass, g/mole K - Nernst distribution coefficient Xi - mole friction of solution component X°PbC12 - mole friction of PbC12 in saturated solution X°T1C1 - mole friction of T1C1 in saturated solution T - temperature, K R - gas constant, J/(mole K) k - kinetic equation constant, 1/(%-min.) ?i - solution component activity coefficient e - extraction rate, %

Jan 1, 2008

1. Book reviews A report by the Monopolies and Mergers Commission on the efficiency and. costs in the development, production and supply of coal by the NCB (Chairman G. Le Quesne). London, Her Majesty's Stationery Office, Jun. 1983. £20 for report and appendices (2 vols). Reviewer: M. J. Martinson Canadian mines handbook 1983-84, edited by M. R. Brown. Toronto, Northern Miner Press Ltd, 1983. 444 pp. $22. Reviewer: Northern Miner Review Editor 2. New publications Developments in geophysical exploration methods-5, edited by A. A. Fitch. Barking. Applied Science Publishers Ltd (Ripple Road, Barking, Essex IG II OSA, England), 1983. 255 pp. £35.75. High-pressure researches in geoscience--behaviour and properties of earth materials at high pressures and temperatures, edited by W. Schreyer. Stuttgart, E. Schweizerbart'sche Verlagsbuchhandlung, 1983. 545 pp. DM 188. Dynamics of oil and gas accumulations, by Alain Perrodon. Pau, Elf Aquitaine (Documentation Centre Micoulau, 64018 Pau, France), 1983. 368 pp. 240 FF. New paths to mineral exploration, edited by F. Bender. Stuttgart, E. Schweizerbart'sche Verlagsbuchhandlung, 1983. 169 pp. DM 58. Results of the First Workshop on Standards in Geothermics, edited by R. Haenel and M. Gupta. Stuttgart, E. Schweizerbart'sche Verlagsbuchhandlung, 1983. DM 98. E&MJ book of jlowsheets edited by Paul C. Merritt. New York, McGraw-Hill, 1983. 214 pp. $42. 1983 E&MJ international directory of mining. New York, McGraw-Hill, 1983. 808 pp. $70. The future of heavy crude and tar sands - volume 11. New York, McGraw-Hill, 1983. 1300 pp. $1l0. 3. Mineral Policy and Energy publications Aluminium, by A. Johnston. 12 pp. . Arsenic, by J. J. Hogan. 4 pp. Cobalt, by D. G. Fong. 6 pp. Selenium and tellurium, by A. G. Johnston. 7 pp. Stone, by D. H. Stonehouse. 13 pp. Uranium, by R. T. Whillans. 16 pp. 4. Mintek publications Report M88 'l'he recovery of platinum-group metals and gold by the lead-collectionstep of thefire-assay procedure. Report MI04 The preparation and analysis of reference materials, and the provision of recommended values. Progress report no. 5. Report Mll1 The determination, by flow-injection analysis, of iron, sulphate, silver, and cadmium. Special publication 3 A guide to the presentation of papers.

Jan 1, 1983

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 I. Bock

This presentation describes a technique under development referred to as Selective Blast Mining. The technique involves millisecond sequential blasting. It applies to mines where the gold bearing conglomerate band is clearly demarcated, and separated from the waste rock in the foot and hanging wall. The width of the conglomerate band should be less than ± 0,7 metres. A research program was initiated in August 1994 by Drs RE. Robinson and I.E. Bock. The objectives were to develop new blasting methods that can reduce: ? the losses of gold in narrow reef stoping. Losses of gold can be as much as 10-15% ? and to introduce selective mining to reduce ore dilution with waste rock.

Jan 1, 1996

By F. J. N. Stassen

SYNOPSIS The effect of conditioning energy on the flotation of gold, U308, and pyrite was investigated in the range 0,1 to 100 kWh per tonne of dry ore for various combinations of conditioning time and impeller speed in a cylindrical con¬ditioning tank. It was found that, when the conditioning energy was increased to between 5 and 10 kWh per tonne of dry ore, the total recovery and flotation rate of the valuable minerals (expressed as Klimpel parameters) increas¬ed substantially. The Klimpel parameters are dependent on conditioning energy, but are independent of condition¬ing time or impeller speed (at constant conditioning energy). The Klimpel parameters of the gangue are indepen¬dent of conditioning energy.

Jan 1, 1991

By Nelson Sánchez

The Los Bronces Development Project (LBDP) was approved in October 2007 by the Anglo American plc Board at a capital cost of some US$1.74B, and is scheduled to be completed by the end of 2010. The project represents a big step forward for the Los Bronces mine since it will increase the treatment rate by 140%, the mining rate by 64% and almost double copper production during the first four years of the project. This economy of scale will also position Los Bronces as a much bigger and efficient mining operation, better prepared to face adverse market scenarios and allowing Anglo to consolidate its position in base metals. The project addressed numerous scope alternatives such as plant capacity vs mine capacity, cut-off grade strategy to maximise value based on the existing flotation and leaching process, cutback strategy, etc. Main infrastructure aspects of the project are as follows: ?Dump area with 2400Mt capacity for waste and low grade material ?Mining equipment: 1 x electric shovel, 12 x 300t trucks, 1 x drill ?Primary crusher: 60? x 89? ?Three new power lines (144MW capacity) ?Grinding plant at 87kt/day nominal capacity (includes a 4.3km tunnel with a regenerative conveyor belt) ?Grinding plant: 1 SAG mill 40? x 25?, 2 ball mills ?Slurry pipeline (52 km from grinding to flotation plant) with five choke stations ?Flotation plant (rougher, cleaning, regrinding circuits and molybdenum flotation). The history of Los Bronces started in 1867 when it was discovered. In 1978 ENAMI (Government company) sold Los Bronces to Exxon for US$112M. The same year a snow avalanche destroyed San Francisco Flotation Plant. In 1979 the plant was rebuilt at 4.9kt/day and from 1979 to 2002 several plant expansions were made up to 54kt/day capacity. In 2002 Anglo acquired Los Bronces for US$1.3B. The 2002 resource and reserve statement showed reserves at 459Mt at 1.02%CuT and resources at 780Mt at 0.80%CuT. The 2007 statement shows reserves at 1,480Mt at 0.67%CuT and resources at 1,644Mt at 0.45%CuT. Defining the size of a plant expansion is the key challenge that any expansionary project faces. The scope of this paper is a general review of the project, describing all the mining techniques that were used to define the best options that maximise value. In this context, a range of plant capacities (from 58 to 230kt/day) combined with a range of mining capacities (from 83 to 166Mt/a) were evaluated in detail, defining for each option a mine plan, Capex and Opex, and cut-off grade strategy for flotation and leaching processes and the associated Net Present Value (NPV) that was used as the selection criteria. The Los Bronces mineral resources potential provides good growth opportunities for the mine beyond LBDP implementation, offering an exciting invitation to continue studying new initiatives that maximise the value of this deposit.

Jan 1, 2008

By O. S. Tinkler, K. C. Sole

"Although the first large-scale application of copper recovery by solvent extraction took place in Zambia in the early 1970s, it is only in the last decade that this technology has become widely employed in this part of the world and is now a mainstay unit operation in copper hydrometallurgical flow sheets. The mineralogy of the ores of the African Copperbelt, and hence the characteristics of African leach liquors, differs significantly from those in Chile and the southwestern USA, where copper solvent extraction has had a long and successful history. These differences provide operators, metallurgists, reagent vendors, and engineers with many challenges: new approaches are needed to adapt solvent-extraction technology for successful implementation in this region. This paper examines typical operating practice in the African Copperbelt, discusses differences compared with other parts of the world, and looks at some of the challenges and opportunities presented by these flow sheets. IntroductionFollowing the success of the Rancher’s Bluebird and Bagdad solvent extraction and electrowinning (SX–EW) operations in Arizona in the late 1960s, the Tailings Leach Plant at Chingola, Zambia, became the first large-scale copper SX plant in the world, commissioned in 1974. Despite the equipment design now being outdated, this plant still continues to operate successfully, indicating the versatility and adaptability of this technology. Today, there are some 75 copper SX operations worldwide with cathode production above 10 kt/a. The top ten producers currently account for about 40% of the global 4.3 Mt/a SX–EW copper production. South America (predominantly Chile and Peru) is the largest copper cathodeproducing region, with annual production of some 2 Mt. The Central African Copperbelt (Zambia and the Democratic Republic of Congo (DRC)) is second, with cathode production of 1.2 Mt/a, and North America (USA and Mexico) third, producing close to 0.8 Mt/a Cu (Solvay Cytec data, 2014). The remaining 0.35 Mt/a comes from all other regions combined (referred to as ‘Rest-of-World’)."

Jan 1, 2016

By H. Karabulut, S. Gündüz, K. Karacif, M. A. Erden

The corrosion properties of iron-based composite materials containing graphite and silicon carbide (SiC) reinforcement were investigated. The effects of silicon carbide reinforcement were investigated by adding 0.5% graphite and 1%, 2%, and 4% SiC. A powder metallurgy method was used to produce the composite samples. Iron, graphite, and silicon carbide powders were blended for one hour with a threeaxis mixer and then unidirectionally pressed under a pressure of 750 MPa. After pressing, the composite materials were sintered at 1100°C for one hour. The corrosion properties and microstructure, density, and hardness properties of the composite materials that can affect the corrosion properties were also investigated. It was determined that the pore ratio and hardness of the composite material increased, and corrosion resistance decreased, with increasing silicon carbide content.

Jun 2, 2022

By A. F. Mulaba-Bafubiandi

Pseudomonas spp was isolated from mine water and tailings samples collected from mining effluents and mine dumps in the Gauteng and Northern provinces of South Africa respectively. Adsorption properties of Pseudomonas spp were then tested for the removal of Cu and Co initially from their synthetic sulphate solutions, subsequently from effluents derived from metallurgical operations. The effects of experimental conditions such as pH, temperature, time, volume and metal concentration on the efficiency of the biosorption process were studied. Absorption of 45% Cu (pH 6, 37°C, 24 hours) and 40% Co (pH 6, 37°C, 24 hours) was observed from solutions with low concentrations (0.07 M). A maximum of 73% and 65% of Cu and Corespectively were recovered from the mine water samples derived from effluents.

Jan 1, 2009

The aspect ratio (mill diameter/mill length) of autogenous and semi autogenous mills varies widely and can be as high as three or as low as 0.5. The literature on the subject of what effect aspect ratio has on grinding mill performance or energy efficiency is almost non-existent. However, at the design stage of many grinding circuits the subject is often vigorously debated amongst metallurgists. In this paper the performance characteristics of mills with different aspect ratios are examined to determine whether process performance characteristics are a function of aspect ratio and whether high aspect ratio mills are any more or less energy efficient than low aspect ratio units. Data from both pilot and full-scale mills are used for this purpose in open and closed circuit configurations.

Jan 1, 2007

By J. Ning, T. Bu, J-Q. Jiang, L. Jiang

"In coal mining in China, the cutting height of the shearer in longwall faces is increasing. Owing to the increase of extraction height, the caved roof strata area is enlarged, and new issues are being encountered, such as determination of a suitable working resistance for the shield and control of the roof. Through field observation and theoretical analysis of the first longwall face with a height of 6.0 m in the Bayangaole mine, a three-stage structural model was developed. Stage I is defined as the period in which the lower immediate roof (LIR) caves into the goaf and is broken into irregular shapes of various sizes. Stage II is defined as the period in which the upper immediate roof (UIR) breaks and impacts the LIR. In stage III, the main roof breaks into blocks and then impacts the UIR. With respect to these three stages, a suitable method was identified for calculating the working resistance of the shield support for a super-great mining height longwall face (SGMHLW). Introduction and backgroundThe coal seams in the Shendong coalfield, located in the northwest of China, are characterized by low dips and large thicknesses and are thus suited for full thickness extraction. Since the mid-1990s, the Shendong coalfield has been developed into one of the largest in the world (Ning, Liu, and Tan. 2014; Ning et al., 2017). Recent developments in mining equipment have made it possible extract entire seams up to 5.0 m thick in a single cut. This method, termed the ‘super-great mining height longwall face’ (SGMHLW) method, has been widely adopted in the Shendong coalfield (Table I) (Ju and Xu, 2013; Peng, Li, and Zhou 2015; Zhang, Fan, and Ma 2011). According to some studies, sudden support-closure incidents often occur when using the SGMHLW method. The key to solving this engineering issue is to have a clear understanding of the structural characteristics and movement laws of the overlying strata. For instance, the load on the supports is related to the movement of the roof stratum as a response to the mining activities."

Nov 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