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By T. Bednarski, L. Thomas, G. Banza, D. Muteba, P. Cole, M. Soderstrom

"In copper solvent extraction, aqueous-in-organic entrainment results in the carry-over of unwanted species into the electrowinning process with negative cost implications. The need to bleed is increased and the purity of the copper cathode is potentially compromised, depending on the impurities being transferred (Cl, NO3, Fe, Mn). In some cases, entrainment results in elevated levels of manganese in the electrolyte which can cause oxidative conditions to develop and degradation of the organic phase. Degraded organic phase detrimentally affects the physical performance of the copper solvent extraction process, contributing to even higher aqueous-in-organic entrainment. Aqueous entrainment may be minimized through good operating practices and maintenance of the organic quality, but the accurate measurement of entrainment remains a challenge. This paper presents coalescing devices designed to provide more exact measurements of aqueous-in-organic entrainment. IntroductionMany copper solvent extraction (SX) plants experience high aqueous-in-organic (A-in-O) entrainments but are unaware of the extent of the problem because entrainment is often not measured. Aqueous entrainment results in the carry-over of unwanted species into the electrowinning (EW) process and the need to bleed to maintain acceptable concentrations in the electrolyte. The costs associated with the bleed are exacerbated in copper plants where aqueous entrainment levels are high. Other than these direct costs, there are operational consequences of the build-up of certain species in the EW circuit that can have deleterious effects on plant performance.Minimizing aqueous entrainment in operating plants requires an understanding of the factors that affect entrainment levels. Both chemical and operational influences are discussed in this paper. The difficulty of obtaining a representative sample makes it challenging to obtain an accurate measure of aqueous entrainment from a continuous process like SX. Coalescing devices used to get a more precise measurement of A-in-O entrainment are useful to complete mass balances around the SX circuits. Alternatively, mass balances can be used to estimate aqueous entrainments and are helpful as a tool to troubleshoot operations with a view to improving plant performance."

Jan 1, 2016

By F. R. Deist, R. P. Plewman

Discussion: A. Hazell (Associate Member) and T. J. Kotze (Graduate Member): The authors must be congratulated on the development of a versatile computer programme for determining the stresses and displacements resulting from mining operations. As a design tool it will no doubt take its rightful place together with the analogue computer. Union Corporation made use of this digital computer programme whilst still in its development stage to determine the stress distributions which were causing the unexpected failure of the Marievale sub-incline shaft. Two features arising from this investigation may be of interest to members, namely: A. The solution to the problem of stabilizing a rectangular inclined shaft, which turned out to be contrary to accepted mining practice, and B. A comparison between the results obtained with the pure digital system and the analogue computer. A. The shaft is nine ft high and 20 ft wide, dipping at 9° to the horizontal and crossing the bedding planes. Fig. 1 is a plan and Fig. 2 is a section of the sub-incline shaft pillar area showing the relative positions of the shaft and reef as well as their respective dips. The deepest point in the shaft is 3 300 ft below surface and the requirement of a stress free ground surface may not be satisfied. It also means that the original gravitational stresses are low. A 900 ft wide pillar was left to protect the bottom section of the shaft, the top section being understoped years ago. Extraction of the pillar was started at the beginning of last year, mining operations being carried out in the accepted manner, starting beneath the shaft and mining outwards. The approach did, however, turn out to be the wrong one, because failure of the shaft was noticed soon afterwards. Even small movements were serious in this case due to the low clearance between the skips and the shaft supports. During October, 1968, failure between benchmarks 8 and 10 (see Fig. 1) became so excessive that hoisting speeds had to be reduced. Failure continued to occur and, by the end of March, 1969, failure had propagated up the shaft as far as benchmark 7, and down as far as benchmark 12. As this shaft had a tight hoisting schedule it was imperative that a quick solution be found to arrest the failure.

By G. Voiloshnikov, P. Koblova, Ye. Musin

Preg-robbing activity of the carbonaceous matter negatively impacts the process of precious metals recovery from gold-bearing ores and concentrates. In this paper, ore heap leaching (HL) using a blinding agent which inhibits ‘preg-robbing’ is a promising method. A carbonaceous ‘preg-robbing’ gold ore with head gold grade of 1.92 g/t from a Russian deposit was studied. Corg was 1.12%. In accordance with the Irgiredmet technique, preg-robbing activity was 65.3%. Surfactant reagent DN was used as the blinding agent. Column tests on the ore HL were conducted using two options. They were: a conventional flow sheet (Column 1) and a flow sheet with the reagent addition (Column 2). Gold recovery in Column 1 was 55.39% while gold recovery in Column 2 was 68.48%. The test results confirmed the efficiency of reagent DN. Keywords: Carbonaceous ore, organic blanking, preg-robbing, recovery

Jan 1, 2020

By Z. Levinson, R. Dimitrakopoulos

A mining complex is an engineering system where raw materials are extracted from several mines, processed, transported, and sold to the market. The uncertainty and local variability of material grades and their locations within the related mineral deposits are critical for determining the optimal life-of-mine extraction sequence, destination policy, operating modes, and capital investment decisions, which define the production schedule of a mining complex. Infill drilling is used to further characterise a mineral deposit and reveals information that changes the representation of the resource model and potentially the resulting optimal long-term production schedule. A self-learning reinforcement learning approach is proposed to determine the optimal drilling locations that maximise the net-present value of the long-term production schedule and the associated financial forecasts by adapting the schedule to additional information. A case study at a copper mining complex demonstrates a $70 M increase in project value by collecting drilling information with a $1 M budget.

Sep 1, 2021

The International Colloquium on Developments in Froth Flotation, which replaced the Annual University of Cape Town (UCT)/University of Stelenbosch (US) Minerals Processing Symposium, was held at the Van Riebeeck Hotel in Gordon's Bay on 3rd and 4th August, 1989. The Colloquium attracted 150 delegates from the mining, metallurgical, and chemical industries, including 9 from overseas.

Jan 1, 1989

By R. G. B. Pickering

The Faculty of Engineering at the University of the Witwatersrand and the Mining Technology Division of the CSIR have co-operated to define the problems associated with deep level mining and in this paper they will identify what they consider to be the critical areas requiring technological solutions. This perspective will then be applied to work currently being carried out by both the organizations and gaps for additional developments will be identified. Finally the Co-operative Research Centre methodology operating in Australia is described. The purpose of this CRC is to provide a vehicle for R&D co-operation to develop and implement technologies which will increase the competitiveness of the mining industry. A further objective is to develop an appropriately skilled human resource base.

Jan 1, 1996

By A. Mainza, I. Govender, Elbasher M. E. Ahmed

A mechanistic description of axial segregation in rotating drum flows remains an open question. Consequently, optimal mixing of grinding balls and rocks for efficient breakage, maximum production of fines, and slurry transport is seldom achieved. Experimental and numerical studies of granular mixtures in rotating drums identify alternating axial bands that eventually coarsen in the long-term limit. Most models of axial segregation are limited to binary mixtures and cannot always predict the logarithmic coarsening effects observed experimentally. A key missing factor is a robust description of the axial free surface profile that is valid across a wide range of flow regimes. We present a practical model of the axial free surface profile by linking it to readily-derived geometric features of the cross-sectional S-shaped free surface profile. A parametric study shows good agreement with experimental measurements reported in the literature and heuristically valid trends.

May 1, 2021

By R. G. B. Pickering

The Faculty of Engineering at the University of the Witwatersrand and the Mining Technology Division of the CSIR have co-operated to define the problems associated with deep level mining and in this paper they will identify what they consider to be the critical areas requiring technological solutions. This perspective will then be applied to work currently being carried out by both the organizations and gaps for additional developments will be identified. Finally the Co-operative Research Centre methodology operating in Australia is described. The purpose of this CRC is to provide a vehicle for R&D co-operation to develop and implement technologies which will increase the competitiveness of the mining industry. A further objective is to develop an appropriately skilled human resource base.

Jan 1, 1996

By Stephen Yirenkyi

The mining industry remains the backbone of many economies in the developing world. Its resurgence in Ghana since 1989 was driven by the global paradigm which emphasizes private sector-led development as the engine of economic growth in developing countries. The historical importance of mining in the economic development of Ghana is evident in the country?s colonial name, Gold Coast (Akabzaa T. and Darimani A., 2001). Ghana earned $2.5 billion from mineral exports in 2007. 20,000 people are employed in large-scale mining whilst 500,000 are employed in the small-scale sector. Mining contributes about 7% of Ghana?s total corporate tax earnings, 41% of total exports, 12% of revenue collected by the Internal Revenue Service and 5% of Gross Domestic Product (Ghana Chamber of Mines, 2008). Gold dominates the mining sector and the country is Africa?s second largest gold producer after South Africa. Surface Mining, which refers to a method of extracting minerals from the earth by their removal from an open pit or borrows, requires a large tract of land for its operations (Wikipedia, 2008). There is therefore a continuous divergence of interest between land required for surface mining and other land uses such as farming and housing, among others. In recent years, surface mining has been promoted in many mining countries because of the following reasons: ?Cost considerations compared to underground mining; ?Safety considerations, compared to underground mining; ?Low grade ore which requires processing huge quantities; ?Location of the ore bodies; and ?Competition among gold producing countries for investors. This paper looks at the socio-economic impacts and challenges of surface mining by using Gold Fields Ghana Ltd. Tarkwa, Ghana as a case study. The company has a concession of about 208 sq km located in the heart of the Wassa communities in the Western Region of Ghana and undertakes surface mining like most of the other mining companies in the country. Gold Fields, Tarkwa mine produces 700,000 ounces of gold a year with the potential of increasing this output to 800,000 ounces after its current expansion programme. Some of the effects of surface mining identified were: 1. Relocation/Resettlement of host communities and its negative effects; 2. Disturbance to Flora and Fauna; 3. Disturbance to Sacred Places; 4. Land Degradation; 5. Noise and Air Pollution; and 6. Water Pollution. This paper sought to investigate the measures put in place by the government and the Gold Fields Ghana Ltd. to mitigate the above effects in order to ensure peaceful coexistence between the mining company and its host communities. It concludes that most mining companies presume the provision of socio-economic development in mining communities will lead to the company securing a social license to operate. This however is not true but rather effective community relations combined with socio-economic development. According to Gold Fields Ghana Ltds. model, this involves continuous community engagement, conflict resolution and comprehensive environmental monitoring programme which will all lead to effective community relations. The strategies to ensure socio-economic development involves community development programme, livelihood restoration programme and community training and employment. All these will then lead to sustainable development which will ensure the company?s social license to operate. Gold Fields? model is in line with the principles of responsible mining. With this model, the community feels they are part of the company and the social license of the company is guaranteed. Gold Fields? model, which has been tried and tested for the past five years, could serve as a template with suitable modification for local conditions for other mining countries where surface mines operate.

Jan 1, 2008

By J. E. Forbes, B. K. Loveday

The role of gravity concentration in the recovery of gold from typical South African gold ores is described. The location of the concentrator in the grinding circuit is discussed, and typical capacities and operating costs are given. Some operating problems are mentioned, but the performance of concentrating equipment is not dealt with in detail since this to some extent depends on the nature of the ore. It is concluded that the main benefits are an improved recovery of coarse gold and a reduction in soluble loss. The use of a long leaching time and a carbon-in-pulp recovery system may eliminate the need for gravity concentration. but gravity concentration is seen as an inexpensive way of improving the recovery on existing plants.

Jan 1, 1982

By H. White

The applicability of ground penetrating radar (GPR) in numerous qualitative applications has been demonstrated over the past five years in the South African mining industry. These applications include the delineation of faults and dykes, fracture mapping, delineation of shear zones, mapping of depth of weathering, and the delineation of contact between different rock types. The qualitative nature of the data collected using existing commercial GPR systems, often relying on expert interpretation, has however mitigated against the full scale routine application of GPR in the mining industry. The recent development of the RockRadar system by ISS International has, to a large extent, overcome these problems. The result is that quantitative rock-mass studies can now be performed with the RockRadar system.

Jan 1, 1996

By W. F. Lorch

Growing use of deionised water in surface coating techniques by w. F. LORCH Production engineers in the metal plating, paint, plastics-coating and printed circuit industries are increasingly aware of the cost of sub-standard or blemished items which have been poorly processed. An area where quality control can quickly produce higher efficiencies is in the choice of suitably purified water for making up solutions, for rinse baths and 'drag-out' baths, for cleansing lines and electrophoresis tasks, for maintaining electrolyte density and hence consistency, and for facilitating the recovery of valuable minerals. The author of this article examines the general problems of using nonpurified water, and shows how purified water has become accepted by the principal surface coating industries to improve processes and effect economies.

By A. J. S. Spearingt

The hydraulic transportation of relatively dense slurries for backfill purposes is typically carried through vertical and horizontal pipelines under gravity. Wear in backfill pipelines has become such a major problem that it is now one of the main reasons for the relatively slow build-up of placed backfill in spite of encouraging performance results in the gold-mining industry. This paper describes tests on pipeline wear that were carried out on classified tailings from the backfill plant at Vaal Reefs East. The testwork was carried out under various conditions of slurry relative density, slurry velocity, and pipeline diameter. Empirical relationships are presented for each transportation and pipeline parameter evaluated and, finally, overall relationships between pipeline conditions and transportation parameters are proposed.

Jan 1, 1992

By H. C. Voges

An account is given of the tests being conducted by Iscor on the following processes for the beneficiation of coal fines: froth flotation, gravity separation, heavy-medium separation, and pneumatic and column flotation. The coals used in the tests came from the Durnacol, Tshikondeni, Grootegeluk, and Hlobane collieries. The problems involved in the dewatering of fine products are stressed. From a theoretical study of the efficiencies that should be possible for a hypothetical South African coal, it is concluded that future fines-beneficiation plants in South Africa may use standard heavy-medium cyclones for coal down to 1 mm in size, fines heavy-medium separation for the 1 mm to 450 µm fraction, and column or pneumatic flotation for the minus 450 µm fines.

Jan 1, 1991

By N. Naude, R. Foisy, F. Bornman

Spiral separators have been widely accepted as one of the most flexible gravity separation devices for several decades. The International Journal of Mineral Processing, 84, pp. 118 – 132 mentioned that spirals are for treating material too coarse for flotation and too fine for dense-media separation. Powder Technology V 102, pp 244 – 252, 1999 stated that there exists a genuine need for extending the performance envelope of spirals – whether to treat finer or coarser material than the traditional size ranges. In recent times there has been an upsurge in interest, particularly in the development of newer fine gravity separators. Spiral separators for the recovery of ultra-fine particles have a unique profile, pitch and features to ensure efficient performance. The flow on the spiral trough must be controlled to minimise turbulence that will entrain fine particles in the outer section of the trough. The experimental test work showed a movement of mass from the outer region towards the centre column of the spiral, i.e., from the fine tailings band towards the concentrate. As recovery on the spiral trough is a function of mass yield and grade, the ultra-fine 7 spiral had a better recovery than the HX5. This makes the UF7 an ideal rougher spiral. Keywords: Ultra-fine particles, spiral, design, recovery

Jan 1, 2020

By M. Saghaeian, R. Hejazi, L. Hosseini, M. V. Sheikhzadeh

HPGR equipment has been well proven to be energy-efficient in the first stage of grinding in iron ore beneficiation plants. Numerous advantages of utilising HPGR grinding prior to ball mill grinding, such as reducing the power consumption in a ball mill through generation of micro-cracks, has been thoroughly studied. Less attention has been paid to efficiency of the HPGR circuit rather than the downstream ball mill circuit. In this study the HPGR circuit has been optimised through feed size reduction by crushing, and feed iron content upgrading by dry cobbing. This optimisation leads to better operation of the HPGR, and a smaller product size which is expected to result in a lower wear rate of ball mill liners and balls. It is also expected that the top size of the ball mill balls be reduced. Additionally, by reducing the feed size of HPGR from 30 mm to 15 mm, it is possible to achieve similar K80 of HPGR product in lowered pressure, i.e. 2.5 N.mm-2 instead of 3.5 N.mm-2 which translates to ease of operation. Similarly in a given roll pressure, smaller feed sizes result in higher specific throughput of ~10% which means higher production capacities. The results also reveal that this optimisation increases the concentrate weight recovery by about 10%. It also results in slight increases in the Fe grade of the product iron concentrate. Keywords: HPGR, HPGR circuit optimisation, crushing prior to HPGR, dry cobbing prior to HPGR, ease of operation, concentrate grade optimisation, weight recovery optimisation

Jan 1, 2020

By R. Mumbi, M. Peart, E. Arinaitwe, B. Mbao, J. Zulu

Since 1925, xanthates have been widely used in sulfide flotation due to their low cost, ease of manufacture, and ability to float most value species. However, the industry's increasing need for safer and more selective alternatives, driven by low head grades, poor-quality, difficult-to-process ore with complex mineralogy, and stricter environmental regulations, has led to the development of Solvay's AERO® XR series of collectors. These custom-formulated products are based on greener chemistries and offer metallurgical benefits that are similar to or better than those of xanthates, without the safety concerns. Developed through Solvay's Flotation Matrix (FM) 100 approach, the XR series collectors are suitable for a wide range of applications, including the processing of Cu, Zn, and Cu-Ni, as well as the flotation of precious metals. This paper will highlight the differences between xanthates and XR series collectors, and present case studies of their successful commercial application at various global operations.

Jan 1, 2023

By K. Shame, H. H. Thiele

South Africa holds approximately 70% of the world’s total chrome reserves. Chromium is an important raw material for the production of stainless steel and ferrochrome alloys. Over the years, China’s ferrochrome market has been dependent on chrome ore imports from South Africa. In 2018, China imported about 75% of its chrome ore from South Africa. With the low platinum price and the rising demand for stainless steel, a growing demand to evaluate new beneficiation technologies for fine chromite was identified. Gravity separation of fine chromite (<75 μm) is inefficient, due to the limitations of the technology to upgrade fine particle size distributions. Potential for the recovery of chromite, specifically fines (<75μm), lost to UG2 PGM flotation tails, but also from MG and LG6 spiral circuit tailings exist. Flotation of podiform chromite ores from India and Kazhkhstan is successful in generating saleable product grade, following acid or alkaline flotation routes. Application to South African stratiform chromite is being evaluated, with the emphasis on evaluating reagent type, optimising dosages and the effect of pH in optimising flotation performance. Flotation can unlock additional value from chromite tailings material. The effect of ore characteristics such as gangue mineralogy, particle size distribution and headgrade are reported. The performance in terms of product quality and yield are evaluated and compared. The impact of this paper will not only prolong life of mine and increase revenue but will also alleviate environmental burdens associated with tailings dams. Keywords: Chromite, flotation, fine material, performance optimisation

Jan 1, 2020

By D. Mesa, J. Karvonenb, A. López, P. R. Brito-Parada, R. Grau, D. Davoise

The froth zone in flotation cells plays an important role in determining metallurgical performance. This is even more critical as cell sizes increase, since larger bursting surface areas can easily result in poor froth transport and even stagnant froth zones, which are detrimental to recovery. Generating additional overflowing lip length by adding internal launders and reducing surface area (while also directing the froth to the overflow) by adding crowders are well established design strategies to enhance froth mobility. However, comparative experimental studies of froth zone design modifications at industrial scale are scarce and often lack detailed froth characterisation. In this work, we present the results of two experimental campaigns that were carried out at Atalaya’s Riotinto concentrator in order to determine the effect of a new froth zone design on the flotation performance of a TankCell® e300 cell that operates as the first cell of the rougher bank. These campaigns provided a unique opportunity to assess froth phase phenomena and metallurgical performance before and after changes in design. The original cell design had an internal peripherical launder and a froth cone, while the new concentrate launder technology adds a centre launder and an adjustable froth crowder to the existing launder design. The new concentrate launder arrangement reduces significantly the froth area as well as the froth transport requirements, aiming to improve froth recovery and, consequently, enhance flotation performance, allowing copper recoveries in the TankCell® e300 cell to increase dramatically. In addition, radial profiles of froth height and froth velocity at the surface were determined, which provide valuable insight into the effect of design changes on froth stability and mobility. Keywords: Flotation performance, enhanced recovery, launder, crowder, froth stability

Jan 1, 2020

By H. S. Baloyi, J. J. Rust

Spiral concentrators are widely applied to beneficiate commodities such as Cr2O3, mineral sands, and ferrochrome. The application of spirals for heavy minerals has been limited to a feed top size of 1 mm. At particle sizes larger than this, friction retards heavy particles and the particles' primary velocity approaches zero, resulting in a solids build-up, therefore inhibiting further separation. Recently, a new Multotec SC25 spiral model was introduced to the industry, which aids in beneficiating particles of up to 3 mm, with successes having been demonstrated in ferrochrome slag and titanium-bearing minerals. This spiral also has potential in electronic waste applications. This paper examines the applicability of the SC25 spiral in coarse Cr2O3 recovery. This stems from the fact that junior chrome miners tend to discard particles larger than 1 mm as they neither have milling nor dense media circuits. Also, alluvial chrome miners discard +1 mm even though this size fraction contains recoverable and liberated Cr2O3. The SC25 spiral has shown better Cr2O3 separation efficiencies than the SC21 model and with higher SiO2 rejection at saleable grades, thus providing an additional revenue stream specifically for the coarser (+820 μm) size fractions. Keywords: Spiral concentrators, chromite recovery, specific gravity, SC25 spiral, coarse spiral

Jan 1, 2020