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By L. E. Kun, R. O. Oelofsen, E. J. J. van Vuuren

High-rate floc-blanket clarification of gold pregnant rotary filtrate was introduced at the Vaal Reefs South gold plant of the Anglo American Corporation during February 1978. A. daily 12 000 to 15 000 t of filtrate, with an average suspended-solids concentration of 350 mg/I, is continuously clarified to a concentration of less than 2S mg/I of suspended solids in a modified plant pachuca (10 m in diameter) at throughput rates of 7,7 to 8,5 ma/m2.h by the addition of 5 g/t of ferric chloride inorganic coagulant and 0,2 g/t of Superfloc NI00 flocculant. The pachuca overflow is then clarified further in seven Stellar candle pressure filters of 54,S m2 surface area to under 5 mg/I of suspended solids. The combined clarification cost when the hopper clarifier is used in conjunction with the Stellar filters is R0,0032 per ton of liquid treated, which is approximately 60 per cent lower than the cost of Stellar filtration on its own. The savings are mainly due to the reduced use of filter pre-coat, the consumption of which has dropped by 70 per cent since the introduction of hopper clarification.

Jan 1, 1979

By A.M. Edwards

1. Book reviews Platinum in South Africa, compiled by A.M. Edwards and M.H. Silk. Randburg, Council for Mineral Technology (Private Bag X3015, Randburg, 2125 South Africa), 1987. 55 pp. U$30. Reviewer: R.D. Wintle Scientific and technological developments in extractive metalurgy-G.K. Wiliams Memorial Volume. Parkvile (Australia), The Australasian Institute of Mining and Metalurgy, 1986. $A12 (incl. surface postage). Reviewer: T.Y. OweD Ion exchange and sorption processes in hydrometa/urgy, edited by M. Streat and D. Naden. Chichester, John Wiley & Sons, 1987. 229 pp. Reviewer: B.R. Green Role of Government in mineral resources development, edited by Michael J. J ones. London, The Institution of Mining and Metalurgy, 1985. 180 pp. £40. Reviewer: K.E. Ducat 2. Recent publications Annual report 1987. International Tin Research Institute, Kingston Lane, Oxbridge, Middlesex UB8 3PJ, England, 1988.Tin and its uses no. 156. Address as above. 3. Mintek reports Application Report no. 5 The production of and alusite and other refractory minerals. 1988. 16 pp. . Application Report no. 6 The development up to commercial application of a process for the recovery of lead, copper, zinc, and silver from the Black Mountain deposit. 1988. 14 pp.

Jan 1, 1988

By R. H. C. Andrew

With the advent in recent years qf mechanization in deep-level gold and platinum mines, large quantities of rubber was are being used on both production and support vehicles. Conditions in these types of mines are extremely harsh and, as a result, we performance is significantly lower than in other types of mining such as open-cast base metal mining, where more favourable conditions prevail. Various options are available to the user to reduce tyre costs, including the use of retreads, the filing of tyres, and the repair of damaged tyres. While these methods may be generally successful in open-cast conditions, their use in deep-level mining needs to be carefully evaluated for each particular set of conditions. A basic requirement for any evaluation of we costs is the availability of reliable data on tyre performance and, for this reason, it is essential that proper tyre records are maintained This paper reviews the performance of tyres in deep-level gold and platinum mines in Johannesburg Consolidated Investment Company, Limited (JCI) over a period of about 8 years, and shows how the costs of retreading and tyre filing can be evaluated in practice. It also discusses the cost implications of repairing damaged tyres.

Jan 1, 1994

By N. C. Joughin, A. C. Buckmaster

The use of face conveyors in gold mines by N. C. JOUGHIN. B.Sc. (Eng.). Ph.D. (Wits) (Member) and A. C. BUCKMASTER; M.A. (Cantab.) A mechanized stope-cleaning system has been developed around an armoured face conveyor, which was tested on the surface and in two underground trials. In the second underground trial, an average face advance of 8,5 m per month was obtained with a labour productivity of 27 ca/worker/month on a two-shift blast cycle. Two new face cleaning systems have been built, each incorporating an armoured face conveyor, a loading plough, a collapsible self-advancing barricade, and an integral roof-support system. These are about to be tested. A new type of reciprocating flight conveyor is being developed for stope use. This is cheaper, lighter, and more compact, and exhibits better wear characteristics, than an armoured face conveyor. In the early stages of the trials, this conveyor frequently achieved a singleshift blast cycle. It should be possible to achieve face advances of up to 40 ca/worker/month with a consistent one-shift blast cycle. The use of drill rigs and a self-advancing roof-support system would improve the productivity to over 50 ca/worker/month.

Jan 2, 1976

By C. S. Northcote, I. F. Buchan, L. F. Baars

In 1969 the Coal Division of the Anglo American Corporation was awarded the tender to supply coal to the new 3000 MW power station to be erected at Kriel, which is situated midway between the towns of Ogies and Bethal in the eastern Transvaal. The coal was to be supplied from the No. 4 Seam in the Kriel Area of the Witbank Coalfield. The No. 4 Seam in this area varies in depth of overburden from 75 m to 6 m, with an average of 55 m. Initially, the mine was planned as an underground mine incorporating a three-shaft system for transporting some 8 million tons of coal per annum to the power station. As the result of negotiations between Anglo and Escom to improve the volumetric extraction of coal from the new mine, the Kriel Division of Anglo Power Collieries was finally planned to produce 4,1 million tons of coal from an underground mine and 4,5 million tons from an opencast mine, with a resultant increase in volumetric extraction. This paper describes the opencast operation at Kriel, with particular reference to the water problems encountered and to the operation of the draglines on sloping ground to a depth of 40 m to the top of the coal seam.

Jan 1, 1980

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

All photographs by Carlos Pais Pictures only.... no script.

Jan 1, 1985

With the advent of the First World Conference on Sampling and Blending (WCSB1) in Denmark in 2003 and the subsequent biannual meetings, together with other sampling conferences held on a regular basis, the central tenets of sound sampling practice and theory are spreading throughout the minerals industry. End-users and project houses, or groups who execute the projects, are all now better-informed about the principles of ?correct? sampling and preparation. To support this, many large mining companies now have their own in-house champion who will advise and ensure that the supply of sampling equipment is correct in terms of design and application, which further contributes to improved metallurgical accounting. The presence of a sampling champion also ensures that consistent and acceptable standards in regard to sampling practice are maintained throughout the group. This has, in turn, placed a greater degree of responsibility on the shoulders of sampling equipment suppliers, in terms of their equipment designs and product offerings, as well as applications knowledge for effective installation of equipment on client plants. This paper attempts to highlight the significant challenges that sampling equipment manufacturers often face with regard to complying with the newly understood requirements of best practice and sampling equipment design. Manufacturers invariably face issues with end-users or project houses, including project cost control, restricted headroom for samplers in plant layouts, and a lack of knowledge in certain quarters. These all have a potentially negative effect on the final outcome of a proposed sampling solution or implemented project. In reality, what is intended by all parties and what is ultimately installed are at times very different, with undesirable consequences for all concerned. Against this challenging background, there are, however, a number of instances where intent and implementation are complementary, with very satisfactory results. Keywords sampling, mechanical samplers, design, installation, sampling theory.

Jan 1, 2014

By J. Petersen, H. Naderi, H. Zare, M. H. Nikzad, M. Karimi

In the copper electrorefining process, the dissolution of anodes is significantly reduced or even stopped when the passivation phenomenon occurs. The results of this phenomenon are increasing energy consumption, residual formatting, and voltage levels in the cell. In this study, the electrochemical behaviour of blister copper in the presence of sodium persulfate (PDS) was studied. The electrochemical methods of LPR, Tafel, and Electrochemical Impedance Spectroscopy (EIS) were used. The results showed that the addition of sodium persulfate activates the electrode surface and increases the open circuit potential. In the presence of PDS, the polarisation resistance of the electrode shows an increasing or decreasing tendency, based on the PDS concentration. This tendency is probably due to the formation of surface layers (such as slime layer or copper sulfate) and dissolution of this layer at various concentrations of PDS. The lowest polarisation resistance of 1.8 ohms and the highest corrosion current of 60.6×10-3 and 36.6×10-3 A/cm2 from LPR and Tafel techniques respectively were obtained at the concentration of 40 g/l PDS. Based on the results of potentiodynamic and electrochemical impedance spectroscopy tests, the addition of sodium persulfate to the solution reduces the corrosion resistance, therefore the passivation time of the blister copper anode increases. Keywords: Blister copper, electrorefining, sodium persulfate, anodic passivation

Jan 1, 2020

At the Annual General Meeting of the Chamber of Mines of South Africa, held in Johannesburg on 29th June, 1982, the following leading members of the mining industry were elected to office for the 1982-1983 term: Mr W. W. Malan President Mr C. T. Fenton Vice-President Mr G. Y. Nisbet Vice President William Wouter Malan was born in Springs on 7th November, 1928, and was educated at the Springs High School and the University of the Witwatersrand, where he obtained a B.8c degree in mining engineering. Diamond Mines. Mr Nisbet became a consulting engineer of the Anglo American Corporation in 1972, and a deputy managing director of the Gold Division in 1974. George Young Kisbet was born in Benoni in 1923 and was educated at Pretoria Boys High and the University of the Witwatersrand. Mintek reports Report 2010D A process for the recovery of rare-earth oxides from monazite. (First published 16th March, 1979). Report 2073D A preliminary investigation of the concentration process at Ucar Minerals Corporation. (First published 19th September, 1980). Report 2092D The recovery of pyrite from gold ore by gravity separation. (First published 28th November, 1980). Report M13 Factors affecting the production of fines during the screening and handling of highcarbon ferromanganese.

Jan 1, 1982

By W. Wilmans

Electrokinetic dewatering of kimberlite slime under constant direct curents of 0,5 to 2 A and dewatering under constant applied potentia Is of 16,5 to 46,5 V are considered. The combined efects of electrophoresis and the addition of 8,3 x 10-3 M Mg2+ ions on the one hand, and 1 to 10 p.p.m. of the anionic polyacrylamide flocculant Praestol 2935 on the other, were investigated in a 3-litre Perspex electrophoretic cel. .The electro-osmotic dewatering experiments were conducted in a 3-litre Perspex electro-osmotic cel at various electrode spacings, as well as with a moving anode (top electrode). During electrophoretic dewatering, the zeta potential of the kimberlite particles did not change significantly, whereas the pH and temperature showed marked increases with time. The addition of Praestol 2935 enhanced the setling of the sludge bed owing to the additional effect of flocculation. The addition of electrolyte Mg (CIO4)2 retarded the separation process, partly as a result of gel formation in the slurry. During the electro-osmotic experiments, the rate of dewatering was found to be approximately proportional to the applied constant direct current, and to be independent of the electrode spacing. In general, electro-osmotic dewatering seemed to be more energy-efficient than electrophoretic dewatering.

Jan 1, 1987

By J. Petersen, K. Shaik1, H. Kolev, Z. Cherkezova-Zheleva

Sperrylite is one of the most abundant platinum minerals globally, valued for its economic importance but also known for its highly refractory nature, making it difficult to process via the conventional route. This study explores the oxidative leaching of sperrylite using a cyanide–ferricyanide system, with a key focus on characterisation of the mineral and surface speciation under varied leaching conditions using x-ray photoelectron spectroscopy. The parameters investigated include the effect of sodium cyanide concentration, the use of potassium ferricyanide as an oxidant, copper sulphate pentahydrate as a catalyst, as well as the effects of temperature and particle size. A limited set of leaching tests was carried out to study the surface chemistry rather than optimising dissolution conditions. This approach identified mineral oxidation states and shifts in binding energies, prior to and post leaching. XPS analysis of sperrylite’s surface chemistry identified key species, comprising the bulk Pt(II)–As (≈73 eV) and As(–I)–Pt (≈41.8 eV) states, together with surface oxidation products Pt(II)–O (≈72 eV), Pt(IV)–O (≈74.5 eV), As(III)–O (≈43 eV) and As(V)–O (44.5 eV). Leaching led to the removal of pre-existing oxides on the ultra-finely ground sample, exposing the underlying bulk species. In contrast, the crystalline sample with an initial low concentration of oxides, generated higher amounts of fully oxidised species after leaching, reflecting greater surface reactivity.

Mar 6, 2026

By N. Mangesana

The effect of high solids concentration and coarse particle sizes (d50 ranges 90?300 µm) on the viscosity of a suspension of water and silica sand was investigated. The experiments were designed to include conditions that have been tested by other authors and those encountered in the operation of tumbling mills. The rheological data was measured using a tube rheometer with operating pseudo shear rates of up to 1500 s-1. The rheograms obtained depicted dilatant behaviour. The Otswald-de Waele, Bingham, Herschel-Buckley and Casson models were fitted to the experimental data. The Herschel-Buckely model, which approximates the yield point and gives an indication of the shear thinning or shear thickening behaviour of the suspension, was found to provide the best description of the flow curves for all slurries. The Herschel-Buckely model was then used to determine the apparent viscosity of all the tests. The apparent viscosity and yield stress increased with solids concentration and particle size at the different pseudo shear rates. The increase in slurry viscosity with solids concentration was attributed to increased frequency of particle-particle interactions. The increase in slurry viscosity with particle size was attributed to increased inertial effects. At low shear rates the sand slurry exhibited shear thinning behaviour for all solids concentrations. At higher shear rates above 1000 s-1the high solids concentration suspensions exhibited a transition from shear thinning to a shear thickening behaviour.

Jan 1, 2008

By R. McGregor

You wouldn't start excavating before testing core samples, so why would you approve a project plan before all factors have been identified, reviewed and addressed? Even a champion sports team made up of the best players can't produce optimal results without a well understood and agreed game plan. Could an F1 racing team produce their outstanding performance without rigorous evaluation and testing of the factors for successful performance? Why would we expect a capital works project team to be able to get it right without an understanding and an involvement in setting and implementing the overall game plan and without an understanding of all stakeholder requirements? For International Power's Hazelwood (IPRH) mine in Victoria, the challenge was development and delivery of a 40 year mine plan, ultimately involving relocation of existing mine operations into an adjacent new coal field, land acquisitions and major environmental and other approvals to allow diversion of three streams, a highway, an Over Dimension route and other infrastructure in a political and environmentally sensitive atmosphere. The lessons from International Power Hazelwood's (IPRH) experience are: ? that the clear set of project principles and guiding values ensured delivery of a robust plan; ? a robust plan can withstand significant change; and ? value management (VM) played an important role in providing assurance, to all, that the plan was sound at both the strategic and micro levels. This Hazelwood mine project included five major VM workshops. The first was a critical review process in addition to design and cost reviews. This VM workshop was used to analyse, at a high level, the preferred coal mining sequence and design concepts, together with the interaction between design elements, risks and costs. In addition to this, the workshop provided an agreed common pathway for all downstream decisions. A second VM study was conducted to ensure that the proposed plan and design for relocation of the conveying systems from the existing mine into the new field were planned for optimum achievement from a whole of life cost, time, operational and maintenance perspective, plus the logistics of continuing operations while relocating assets. A third study followed to review the Conveyor Transfer Alliance and review functional design. A fourth VM study workshop was formed at the start of Phase 2 Alliance to ensure that the best value for money was being achieved through the current design, schedule and project arrangements and that all interfaces between parties had been reviewed and responsibilities were clear and understood. Other studies are outlined later in this paper. This paper details the evaluation criteria and processes used in the project evaluation that led to the WestField Mine Development.

Jan 1, 2007

By G. M. Brown, B. J. Ebacher, W. G. Koellner

Introduction There is a continual economic push to increase the productivity of mobile material handling equipment used in open pit mines. This includes the largest electrical machines: excavators (draglines and shovels) and haul trucks (Figure 1). Existing DC drive systems used on this type of equipment are a mature technology. They have no further economic potential to accommodate larger equipment be-cause of the high maintenance costs and the trade-off between power, speed and space limitations of their DC traction mo-tors. In recent years the large-scale introduction of AC drives in the rail transportation sector1,and the availability of poworful GTO and IGBT modules have led to the devolopment of compact, powerful, an drugged AC inverter drives specifically adapted to the mining market2,3. The major advantage of AC drives stems from the squirrel cage induction motor which eliminates the DC commutator. This leads directly to higher speed, increased power density, higher reliability, greater efficiency and lower maintenance of the traction motors. In the context of excavators and haul trucks, additional benofits driving the move to AC are (i) increased production rate due to higher machine speed, and power density, (ii) increased reliability and lower cost inverters using 3.3 kV IGBT's, (iii) active front-end (AFE) technology that improves compatibility with the mine power grid and an proved dynamic response,(iv) intelligent converter design that provides increased fault tolerance, (v) contextual maintenance software that facilitates trouble-shooting, and (vi) remote diagnostic capabilities. This paper describes how these and other features of AC drives lead to higher productivity in mining shovels, draglines, and haul trucks. Minimize the cost per ton of material moved The overall goal that drives design and sales of excavators and haul trucks is the constant requirement to reduce the cost per ton of material moved. Whether this involves blasting, loading trucks, or hauling material to the crusher or waste dump, equipment that reduces the cost per ton of material moved contributes to a more profitable operation. An accurate determination of the true cost per ton to move material must consider every aspect of the equipment and the circumstances under which it is used. Procurement and capital costs, fuel, operating, and maintenance costs over the useful life, and eventually the cost of scrapping should all be taken into account to determine the real cost per ton of moving material. We will focus on two broad areas that relate to the equipment itself; factors influencing the amount of material moved (Table I) and factors influencing the cost of material moved (Table II). Emphasis will be given to those elements in the tables that most influence the productivity of excavators and haul trucks due to the application of AC drive technology. Maximize the amount of material moved Maximize production rate he production rate refers to the quantity of material that can be loaded or moved per hour. This generally involves larger, faster, and more powerful equipment that operates more reliably to minimize down-time. AC motors Figure 2 compares the hoist motor speed-torque response of two 77 t (85 short ton) shovels, one AC the other DC. The absence of commutation limits on the AC motors enables the AC shovel to operate with a greater area under the speed-torque curve, resulting in faster lowering speeds and reduced times for the swing to return to the pit. This is especially important for short swing angles where the operator may have to wait for the dipper to lower. Reducing the cycle time by 6 to 8 seconds at the shovel translates into an increase in shovel production of about 20%. Larger equipment The bucket capacity of excavators has increased approximately 100-fold over the last century. Figure 3

Sep 1, 2001

By R L. Bowers, D S. Smit

In light of soaring commodity prices, Nkomati has investigated the potential of processing additional low grade nickel ores to add to their reserves. The Chromititic Peridotite Mineralised Zone (PCMZ) was identified as one ore type with the potential of producing a high grade nickel concentrate. In addition to the nickel, copper, cobalt and PGM?s, the ore also contains a significant amount of chromite which adds substantial value to the project. Pyrrhotite, pentlandite, chalcopyrite and chromite are the dominant minerals within the ore, which on average grades around 0.23% Ni and 12% Cr2O3. The PCMZ ore contains excessive amounts of fibrous silicates which makes it a challenging float, with gangue control as the key element to success. Extensive laboratory testwork, which eventually led to a pilot plant campaign, was undertaken with the aim of developing a process route for treating the PCMZ ore. Several flotation circuit configurations were tested and results from the optimal circuit indicated that a nickel concentrate grading at 8.5% is achievable at a recovery of 78%, with substantial recoveries for the copper, cobalt and PGM co-products. The chromite concentrate, grading at 45%, was extracted from the flotation rougher tailings via a spiral plant. These promising results were incorporated into the plant design and are currently being evaluated in a bankable feasibility study, which will see the current 100ktpm MMZ concentrator being upgraded to a 250ktpm PCMZ concentrator as part of Nkomati?s Phase II expansion.

Jan 1, 2007

By D. J. Bosman

Rapid fouling of condenser tubes in underground refrigeration plants is a frequent occurrence. It leads to low heat transfer efficiencies, with consequent serious reduction in capacity and increase in the horse-power requirement of the units. High pressures develop in the condensers, and frequent cleaning of the tube bundles is required. The cleaning operation takes up to 8 hours and in some cases results in significant loss of production. One of the possible causes of fouling is deposition of scale, but this can be readily overcome by controlling the concentration of the water. When water evaporates, the dissolved solids remain behind; thus evaporation increases the amount of dissolved solids per unit volume. If half the original volume evaporates, the concentration of the dissolved solids is doubled and the water is said to have a 'concentration' of two. Concentration may be controlled by regulating the amount of water allowed to bleed from the system. The actual concentration value required is a function of the chemical analysis of the circulating cooling water. In one instance, where the problem of scale formation had been eliminated, fouling still persisted, and the possibility of excessive quantities of dust in the re-circulating water was investigated. A dispersing reagent was added to the condenser cooling water as a means of preventing sludge deposition in the condenser tubes. As shown by curve A in Fig. 1 the reagent addition did not decrease the rate of fouling.

By S. Botes, H. van der Merwe

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

Jan 1, 2014

By T. Ono, B. Altansukh, S. Kawamura, K. Haga, A. Shibayama, Y. Takasaki

In recent years, the grade of silica in zinc concentrate has increased due to the degradation of zinc content and the increase in impurity content in natural ores. It implies that the development of silica removal technology from zinc concentrate is necessary to solve problems in the smelting process caused by the high content of silica in zinc concentrate. In this paper, the authors investigated the silica removal processes from silica-rich zinc concentrate by mineral processing approaches such as re-grinding and flotation. This study focused on the pulverisation process as a pretreatment for the investigation of individual minerals' liberation from the silica-rich zinc concentrates using different kinds of pulverisers. Flotation experiments were performed to separate silica and zinc concentrate from the pulverizsd feed sample using a pH regulator (NaOH), activator (CuSO4), collecting agent (PAX), and foaming agent (DOW froth 250). Results showed that the liberation rate of silica (SiO2) was reached 75% from 13% by pulverisation in an attritor with a 2 mm ball in diameter, while silica accumulated in a fraction over 20 mm in size. Flotation experiments indicated that silica removal efficiency was achieved by 44% from + 20 mm fraction obtained from pulverisation whereas the grade of silica in froth reached 1.85 mass% from 4.5 mass%. Results indicate that silica could selectively separate from silica-rich zinc concentrate, and 99.8 % zinc recovery is achieved under the studied conditions. Keywords: Zinc concentrate, silica, pulverisation, liberation, sieving, flotation

Jan 1, 2020

For practical reasons all basic input data for the gold mines of the Anglovaal Group conform to a regular grid of averages of sample values within 25-ft squares in the plane of the ore body; individual sample values with their metric co-ordinates are input and converted by a computer program to the basic 25-ft square averages. At the Prieska copper mine the bore- hole data are forced on to a regular grid of 15-m squares corresponding to the coordinates of the grid points nearest to the actual borehole intersections. As for the gold mines the Prieska ore body, although some 3 to 30 m thick, is also dealt with on a two-dimensional basis (Krige, 1973). On the gold mines the data subjected to geostatistical analysis cover: gold values (in cm g/t), uranium values (cm kg/t), and channel widths (cm). The gold and uranium values are normalised on the basis of log (value plus constant) and all the geostatistical analyses are performed on these transformed values. The channel widths usually conform reasonably well to the normal distribution and are, therefore, not transformed. At Prieska the metal grades analysed cover the two main products, copper and zinc, as well as the impurities lead and bismuth; in addition the specific gravity values and the hanging- and foot-wall deviations from a projection plane are also handled. These were all previously used on an untransformed basis but because of problems associated with the proportional effect the lognormal-de Wijsian model is now used for some of the grade variables. The key computer pro- grams can be summarised briefly as follows:

Jan 1, 1981