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By A. W. Bester

Paper written on project work carried out in partial fulfilment of B. Eng. (Mining Eng.) Cullinan Diamond Mine currently handles 3.2 million tons of run of ore per annum. This is done by means of an underground train system, which is located at 763 metre level. Four trains, one in each quarter of the pipe, collect ore from passes and transport it to centrally located tips in the north and south of the pipe. The ore is then split into coarse and fine fractions. The coarse fraction proceeds to the primary crushers in the north and south. Historically, mining has been performed in such a manner that an equal amount of ore has reported to each quarter of the pipe. However, the tonnage profile of the mine will change such that the ore will no longer be split equally. For approximately five years the majority of ore will report to the east and thereafter most of the ore will report to the western portion of the mine. This will continue for the remainder of the current infrastructure level?s operational life. Coupled with this is the fact that the mine is aiming to increase its annual production to 3.8 million tons. The result is that the current ground handling system cannot accommodate the additional tons and therefore alternative ground handling options have been investigated. The continued existence of Cullinan Diamond Mine relies on finding a system that can economically handle the additional tonnage. Three options were investigated. Firstly, a train option, which would be an upgrade of the current system, was investigated. Two truck options were also investigated, the first of which was a conventional truck option. The second truck option was more interesting and involved an unfamiliar Combi truck system. The truck options were investigated primarily due to the fact that the block height of the BA West (a new production block) can be increased by 15 meters if a truck option is decided upon. This would create a significant increase in revenue for the BA West project. Each of the options was assessed in terms of its physical and financial feasibility. In terms of the physical constraints, it was found that all three systems could work. Detailed financial analysis indicated that either of the two truck options would be a suitable solution. However, due to the limited information regarding the Combi truck option, it should be further investigated. This applies particularly to the actual running and maintenance costs for the equipment.

Jan 1, 2005

The 105th Annual General Meeting of The South African Institute of Mining and Metallurgy was held in the J.C. Lemmer Auditorium, SA National Museum of Military History, 22Erlswold Way, Saxonwold, Johannesburg on Thursday, 8thAugust, 2002. Welcome The President extended a special welcome to the guests and representatives of our sister institutes and other associations. Also to recipients of awards, senior members of industry, Honorary Life Fellows, Past-presidents, our Members and other guests, among them the following: Mzolisi Diliza, Chief Executive, Chamber of Mines of South Africa Dawie van Wyk and Rod Tucker, Vice-presidents, The Geological Society of South Africa Vaughan Townsend, President, Institute of Certificated Mechanical and Electrical Engineers, South Africa Karel Landman, President, Institute of Mine Surveyors of South Africa Frik Grobbelaar, South African Colliery Managers? Association Pierre Ballot, President, South African Institute of Electrical Engineers Trueman Goba, President, South African Institution of Civil Engineers

Jan 1, 2002

By P. A. Olubambi

The leaching of zinc and copper from Nigerian bulk sulphide ore with sulphuric acid in the presence of hydrogen peroxide was studied. The aim of the study was to investigate the effectiveness of hydrogen peroxide as an oxidant for the sulphuric acid leaching of zinc and copper from a complex sulphide ore. Distribution of elementals within the various particle sizes was initially determined by ICP-OES and XRF to provide a basis for explaining the dissolution process. The effects of concentration of hydrogen peroxide, particle size, stirring speed, and leaching time at a constant temperature of 298K were studied. There were variations in elemental and mineralogical composition within the different sizes. The concentrations of zinc and copper reduced as particle size decreased while silica, sulphur, iron and lead contents increased. Dissolution results showed that the leaching rate of copper was lower than that of zinc. The highest recoveries of zinc and copper were obtained at a leaching time of 180 minutes, stirring speed of160 rpm, particle size of 75 µm and a concentration of 1M H2SO4/1MH2O2. It was observed that the leaching rate of zinc and copper increased with increasing hydrogen peroxide concentration. Increased stirring speed had a negative leaching effect as it promotes hydrogen peroxide decomposition. Keywords: Nigerian sulphide ore, zinc, copper, hydrometallurgy, sulphuric acid, hydrogen peroxide.

Jan 1, 2006

By P. A. Olubambi

The leaching of zinc and copper from Nigerian bulk sulphide ore with sulphuric acid in the presence of hydrogen peroxide was studied. The aim of the study was to investigate the effectiveness of hydrogen peroxide as an oxidant for the sulphuric acid leaching of zinc and copper from a complex sulphide ore. Distribution of elementals within the various particle sizes was initially determined by ICP-OES and XRF to provide a basis for explaining the dissolution process. The effects of concentration of hydrogen peroxide, particle size, stirring speed, and leaching time at a constant temperature of 298K were studied. There were variations in elemental and mineralogical composition within the different sizes. The concentrations of zinc and copper reduced as particle size decreased while silica, sulphur, iron and lead contents increased. Dissolution results showed that the leaching rate of copper was lower than that of zinc. The highest recoveries of zinc and copper were obtained at a leaching time of 180 minutes, stirring speed of 160 rpm, particle size of 75 µm and a concentration of 1M H2SO4/1MH2O2. It was observed that the leaching rate of zinc and copper increased with increasing hydrogen peroxide concentration. Increased stirring speed had a negative leaching effect as it promotes hydrogen peroxide decomposition. Keywords: Nigerian sulphide ore, zinc, copper, hydrometallurgy, sulphuric acid, hydrogen peroxide.

Jan 1, 2006

By David J. Blackwell

The challenge; to design production facilities and in particular separation equipment which have the ability to deal effectively with the ever changing composition of well fluids, over the life time of the field in which it is operating, ensuring maximum uptime of the asset coupled with consistently effective separation. Design engineers are, however, continually confronted with a dilemma when selecting materials of construction for Oil/Gas separation equipment, since they are generally obliged to select an acceptable material of construction, based on ?predicted? operating conditions, at the lowest acceptable cost. Consequently many designs are somewhat basic and do not take into account the constantly varying dynamics of the well fluids being released into the separator. As oil fields mature, oil companies endeavour to maximize revenue by maintaining oil and gas throughputs. This often results in an associated increase in water and sand volumes and, in order to maintain efficient separation, an increase in operational temperature and pressure; subjecting the equipment to operational conditions for which it was never designed. In reality, therefore, the limitations and constraints placed upon new construction design often result in Maintenance Engineers having to solve the ensuing problems in difficult ?in-field? environments. Should refurbishment or upgrade be required then the status of the platform and that of the vessel during shutdown will dictate how this is achieved. Hotwork on the vessel is generally not preferred due to the requirement for post weld heat treatment and re-classification of the pressure vessel, not to mention the added risk in terms of safety. Unfortunately, until recently, there have been few alternatives to conventional ?hotwork? repair and protection systems, especially since the performance of cold curing polymer based repair and coating systems, for use in oil and gas process equipment, has, until recently, been limited by their resistance to temperature and pressure in immersed conditions. In line with the continued development of high temperature / high pressure oil and gas fields however, recent breakthroughs in polymer technology can now offer both repair and protection solutions which are able to function effectively at temperatures up to 180°C in immersed conditions combined with resistance to the destructive forces of explosive decompression from pressures in excess of 90 bar. This paper will look at recent work that has been undertaken to determine the suitability of modern polymer based repair and protection systems as an alternative to hotwork; thus enabling newly designed and upgraded internals to be cold bonded into position and further protected with temperature resistant coatings, in order to minimize the downtime of the asset and further to protect the vessel internals from the Erosive Corrosive environment.

Jan 1, 2006

By C. Musingwini

The subject of optimal planning of level and raise spacing for inclined narrow reef deposits has received intermittent attention over the years because the subject matter is inherently complex. Previous work has approached the problem as simply that of simultaneously minimizing the total excavation and haulage cost associated with the development workings. However, when level and raise spacing are altered, other factors such as productivity are negatively affected, thus requiring a delicate trade-off of contradicting planning or optimization criteria. The paper concludes that the problem is actually of the multi-criteria decision analysis (MCDA) type, contrary to traditional thinking that the planning problem is achieved solely by minimizing waste development.

Jan 1, 2010

By J. H. Zietsman, M. W. Erwee, P. J. A. Bezuidenhout, Q. G. Reynolds

"Pyrometallurgical furnaces are tapped through tap-holes that are opened with drills and oxygen lances. The lance is often used on its own or as the last step of opening the tap-hole. Interaction of oxygen with molten material inside the tap-hole can occur, and is a phenomenon that is not well understood. As part of a study that focuses on the effect of lancing on flow inside and around the furnace tap-hole, a cold-model validation was done. The validation study focuses on validating the MULTIPHASEINTERFOAM multiphase flow solver in OpenFOAM® for the problem involved. The sensitivity of the model to different materials properties (viscosity and density in particular) is presented with both cold models and the results from flow simulations in OpenFOAM®. IntroductionMany pyrometallurgical operations are carried out in furnaces where molten material accumulates continuously. Once enough material has accumulated and is ready to be removed from the furnace, material is tapped through one or more tap-holes in the furnace. Tap-holes differ significantly in both geometry and materials of construction, depending on the process involved – examples of different types of tap-hole configurations can be found in, for example, Nelson and Hundermark (2014). Tapholes all share one common feature: they are high, wear areas of the furnace. Molten material at high temperature flows through these areas, after which the tap-hole is sealed, usually using tap-hole clay. The purpose of the tap-hole clay is to harden inside the tap-hole and seal it until the next tap.Once ready to tap, a pneumatic drill and/or oxygen lance is used to open the tap-hole. The extent of lancing a furnace tap-hole depends strongly on the type of furnace. In, for example, many blast furnace operations lancing is limited as much as possible, and done only if drilling was not effective. In other operations, such as on small-scale pilot furnaces with short tap-holes, only lancing is used to open the tap-hole."

Jun 1, 2019

By R. A. Puchner

The location of a decline shaft portal can have far reaching implications if the geotechnical conditions are not suited for safe and cost effective excavation. Ideally the portal should be positioned in an area where the excavation requires minimal support and the portal can be formed in reasonably competent rock. In many cases, however, the shaft is linked to an underground mining plan and the shaft may have to pass through poor ground conditions. Determining the optimal position at which tunnelling can commence i.e. the portal, is critical and requires a thorough geotechnical investigation. Methods used to acquire information for the assessment of the ground conditions are discussed in this paper. Selection of the appropriate methods is dependent on the anticipated ground conditions, the phase of investigation and restrictions due to site access and budget. Non-invasive techniques are often used during preliminary phases and invasive techniques for the detailed investigation. The methods used during each phase of investigation are discussed. Two case studies are then presented to provide examples of the investigative methods used in two different environments. The first being a flat featureless site with thick soils and deeply weathered bedrock, while the second is a mountainous site with differentially weathered rocky outcrops. Based on these cases, it is clear that an understanding of the geology and geomorphology of the site is vital to the final geotechnical assessment. Key words: Decline shaft, boxcut, geology, geomorphology, geotechnical, portal.

Jan 1, 2009

By R. A. Puchner

The location of a decline shaft portal can have far reaching implications if the geotechnical conditions are not suited for safe and cost effective excavation. Ideally the portal should be positioned in an area where the excavation requires minimal support and the portal can be formed in reasonably competent rock. In many cases, however, the shaft is linked to an underground mining plan and the shaft may have to pass through poor ground conditions. Determining the optimal position at which tunnelling can commence i.e. the portal, is critical and requires a thorough geotechnical investigation. Methods used to acquire information for the assessment of the ground conditions are discussed in this paper. Selection of the appropriate methods is dependent on the anticipated ground conditions, the phase of investigation and restrictions due to site access and budget. Non-invasive techniques are often used during preliminary phases and invasive techniques for the detailed investigation. The methods used during each phase of investigation are discussed. Two case studies are then presented to provide examples of the investigative methods used in two different environments. The first being a flat featureless site with thick soils and deeply weathered bedrock, while the second is a mountainous site with differentially weathered rocky outcrops. Based on these cases, it is clear that an understanding of the geology and geomorphology of the site is vital to the final geotechnical assessment. Key words: Decline shaft, boxcut, geology, geomorphology, geotechnical, portal.

Jan 1, 2009

By S. Parada, P. T. Jones, M. Guo, S. Smets

The corrosion behaviour of a high-quality rebonded magnesia-chromite refractory in contact with a vacuum oxygen decarburization (VOD) slag with high Al2O3content (15?20 mass per cent) is investigated under VOD process conditions by rotating finger tests in a vacuum induction furnace. The refractory degradation mechanisms are studied by the characterization of corroded microstructures using scanning electron microscopy, equipped with energy dispersive spectroscopy. The influence on the refractory wear of the process temperature and the Al2O3content in the slag is discussed. Keywords: corrosion, magnesia-chromite refractory, VOD slags, vacuum induction furnace

Jan 1, 2004

The processes by which particles and bubbles interact capture many of the central concepts of colloid science and hydrodynamics. This area of research embraces hydrodynamics, interfacial(including capillary) forces, particle and bubble behaviour and solution chemistry. In this review, we discuss collision, attachment and stability efficiencies. We deal with the identification of a flotation ?domain?, the deformation of a bubble surface upon interaction with a solid surface, the kinetics of three phase contact line expansion and the determination of attachment efficiencies through to the direct measurement of bubble-particle interaction forces. We have recently carried out a test of collision theory where the latter embraces both inertial and centrifugal forces. The real challenge is now to quantitatively describe the behaviour of real systems and to incorporate a reliable description of the behaviour of particles in flotation froths. The approach described is very robust when applied to flotation, both from qualitative and quantitative points of view, providing an intellectual foundation for understanding this complex process in separation science and technology.

Jan 1, 1999

By S. J. Lötter, J. T. Nel, W. Purcell

"SynopsisGlow discharge optical emission spectroscopy (GD-OES) is an analytical technique used in the analysis of solid, conducting materials. Though primarily of interest as a depth profiling technique on samples with varying layers of both conducting and non-conducting materials, it is also capable of rapid bulk analysis of homogenous, solid samples. GD-OES combines the advantages of ICP-OES (wide detection range, speed, and lack of interferences) with the solid sampling of XRF techniques. This allows the analyst to not only quantify the elemental composition of a sample, but to evaluate it in terms of homogeneity with depth, a field in which auger electron spectroscopy (AES) and secondary ion mass spectrometry (SIMS) have traditionally been the primary techniques. Although GD-OES does not replace these useful techniques, it does offer various advantages over them, making it an excellent complementary analytical tool.In GD-OES analysis, a low-pressure glow discharge plasma is generated with the sample material acting as a cathode, accelerating the cations in the plasma towards the sample surface. This bombardment causes the sample material to ‘sputter’, essentially knocking free atoms or molecules of analyte material, which are then drawn into the plasma where they are excited. The light emitted by this excitation is then diffracted to separate the wavelengths emitted by the specific elements and detected by a spectrophotometer. The intensity of the signal is directly proportional to the quantity of analyte element present in the sample, allowing simple calibration and quantitative determination of the elements. Technological improvements made in the past twenty years or so have significantly increased the usefulness of GD-OES for surface analysis. Faster plasma stabilization and start-up allow for the quantification of surface layers as thin as 1 nm. Sputter rates have been accurately measured for many common materials, allowing them to be built into software libraries in the instrument’s control software. This dramatically expands the usefulness of this software and the ease of performing analyses.GD-OES analysis of nuclear materials allows for the rapid determination of the elemental composition without the requirement of initial dissolution. The thickness of any corrosion layers on nuclear materials can also be determined."

Jan 1, 2015

By G. Swan, E. Nordlund, P. Zhang

"SynopsisThe most widely used support design damage criterion for rockburst-prone mines is based upon kinetic energy, which is proportional to the square of the ejection velocity and is commonly expressed in terms of peak particle velocity (PPV). Field monitoring and back-analyses have shown that ejection velocities of the order of 10 m/s and higher can result from seismic events of moderate magnitude. Such velocities are much higher than those predicted using PPV obtained from scaling laws. It has also been found that the peak ground motion (i.e. PPV) on the surface of an excavation is preferentially amplified (by four- to tenfold) compared to the motion in solid rock at a similar distance from the source. However, the wave propagation and interaction processes involved within the fractured rock in generating high ground motion are very complex and are not well understood at this time.In this paper, velocity amplification was investigated by modelling the dynamic interaction between fractured rock and a free surface using a 2D discontinuum-based numerical program, UDEC (Universal Distinct Element Code). A 1D model with a fractured zone was used to represent the fractured rock. Velocity amplification, quantified by PPV, predicted at the free end of the model was 2.0–3.6 times higher than the input velocity. It was found that the wave frequency, fracture stiffness, fracture spacing, and thickness of fractured zone are the main factors that affect the velocity amplification. The results have proved that the interaction of the seismic wave and multiple fractures near the free surface strongly influences the ground motion.IntroductionSince mining-induced seismicity is almost inevitable in deep mines, ground support is generally employed to mitigate the risk of seismically-induced damage. The most widely used support design criterion for seismicallyprone mines is one that seeks to maximize the absorption of the kinetic energy (plus potential energy if a gravity component is considered) of key rock blocks. Based on this criterion, design methods for rock support were first proposed by Wagner (1984) in South Africa and later improved, among others, by Roberts and Brummer (1988) and Kaiser et al. (1996)."

Jan 1, 2015

Gullies are the vital in-stope excavations that provide access for mining personnel and material to, and mined ore from, the producing faces in the tabular hard rock mines. They pose a serious problem in most mines because they induce stress orientations, which, combined with blast damage, produce adverse rock fracture patterns that contribute to the loss of hangingwall and sidewall integrity. Rock-related injury statistics confirm this by highlighting gullies as the second-highest risk area in South African hard rock mines. Inappropriate gully geometries, poor blasting practice, and non-adherence to accepted standards worsen the problem. The aim of this work is, firstly, to provide guidelines to select the correct gully geometry and appropriate support for a particular geotechnical environment and, secondly, to review the practical issues behind gully safety and stability. In order to meet these aims, this paper reviews the available literature on gullies and their history, and reports on an industry-wide survey of practices and opinions. Then it covers observations from underground visits to 107 gullies situated in the respective geotechnical environments of the Basal Reef, Beatrix Reef, Vaal Reef, Carbon Leader Reef, Ventersdorp Contact Reef, Kimberley Reef, Kalkoenkrans Reef, Merensky Reef, and UG2 Reef. Despite the differing geotechnical conditions and gully geometries, common problems are experienced with geological structure, stress, and fracturing. Results from numerical modelling are also presented to help analyse the underground observations and to quantify the merits of the different gully layouts. It is concluded that there are no new techniques available to improve gully stability, but that significant improvements in safety are attainable by employing the correct gully geometry for the geotechnical environment, good blasting practice, and appropriate support.

Jan 1, 2002

By T. Khumalo, L. P. Coetzer

This paper addresses the impact of the variable speed drive on the particle size distribution in the product of a fully autogenous UG2 grinding circuit. It further discusses the impact of a varying particle size distribution in the product of the mill on the downstream classification and milling circuits. An industrial case study was used and data is presented to illustrate the techniques applied to identify the root cause of the shift in operational efficiency. The results achieved from both the investigation into the shift in plant efficiency and the sub-sequent corrective action taken illustrate that the root-cause methodology used in advance control can be effectively applied on production sites to both detect the shift and identify probable root-causes. The industrial example used confirms that the variable speed drive in a UG2 autogenous milling operation is a critical control parameter to ensure that the plant operates to design specifications.

Jan 1, 2006

By H. Thomas, I. N. M. Nday

"*Paper written on project work carried out in partial fulfilment of BSc.Eng (Mining Engineering) degreeThe optimization of the cycle time to increase productivity at Ruashi Mining was an on-site project investigation conducted from December 2017 to January 2018. The main objective of the investigation was to determine the actual cycle time components. These comprise the queuing time, loading time, hauling time, and dumping time of ADTs (articulated dump trucks). Data was also collected on two hydraulic shovels to identify where these could be optimized. The actual cycle time obtained was compared to the theoretical cycle time to ascertain the constraints, which affect productivity. By applying Systems Thinking to the cycle time, man-made constraints of the actual cycle time were identified and recommendations to mitigate them suggested to optimize the cycle time. However, rainfall is a natural constraint that adversely affects the actual cycle time, and which cannot be mitigated.In addition, both the theoretical and actual cycle time were analysed, as well as the theoretical and actual productivity for the year 2017. Based on the findings, conclusions and recommendations were made to optimize the cycle time. IntroductionThe aim of the project was to increase Ruashi Mining’s productivity by 39%, from about 7.537 Mt of broken material mined to 12..367 Mt targeted in 2017.BackgroundRuashi Mining is a copper (main commodity), cobalt (by-product), and acid producer located in the Democratic Republic of Congo (DRC), 10 km from the city of Lubumbashi. Figure 1 shows the location of the Ruashi Mining open pit.Ruashi Mining started production in 1911 and in 2005 the mine was registered as a DRC company owned by Metorex Group Limited. In November 2013, the Chinese company Jinchua Group International Resources Co. Ltd. bought a majority stake in the business. Ruashi Mining currently produces 38 000 t of copper and 4400 t of cobalt per annum. The company has contracted NB Mining (a contract mining company) to transport its ore. To optimize the productivity of the mine, considering ore flow delivery at Ruashi Mining, the cycle time is the indicator used in this project. The cycle time components were recorded on site using a stopwatch."

Jul 1, 2019

By F. M. L. Mulaudzi

Metal dusting is a corrosion phenomenon that occurs in strongly carburizing gas atmospheres at elevated temperatures. Reaction kinetics and product characterizations of Alloys 602CA and 800 were examined by scanning electron microscopy with energy dispersive X-ray analysis (SEM-EDX) and X-ray diffraction (XRD).The results showed that Alloy 602CA is more resistant to metal dusting than Alloy 800. Visual examination and SEM surface analysis showed that Alloy 800 suffered metal dusting attack after a relatively short exposure period. The amount of coke deposits increased on Alloy 800 with increased exposure from 96 to 336 hours. X-ray diffraction on the reacted surfaces identified graphite and austenite in both alloys and some iron oxides/spinel for Alloy 800.

Jan 1, 2012

By S. M. Spottiswoode

The aim of the hybrid location method is to improve seismic event locations by reducing the effects of errors in the wave velocity of ray paths between each event and each recording site. We report on further enhancements made to the hybrid location algorithm, which is based on the double-difference method developed by Spottiswoode and Milev1and Waldhauser and Ellsworth2. The term ?double-difference? refers to the residuals between the observed and theoretical travel-time differences and are obtained using either picked arrival times or various measures of time differences obtained from waveform pairs. These residuals are minimized for pairs of earthquakes at each station while linking together all observed event-station pairs. An important enhancement is that the double-difference term uses the median arrival time residuals to reduce the effect of outliers on the system of equations. In addition, the hybrid locations are further constrained by considering events of known locations, in this case along lines of development blasts. We relocated some 20 000 previously located seismic events in the Driefontein 5E area; 5 800 of these events were considered to have been development blasts and we constrained their locations to lie on the straight lines joining about 2 150 survey pegs from the mine?s database. Relocated events were shown to distribute more closely around advancing faces than had been the case before relocation. Wave velocities from the development blasts show evidence of anisotropy.

Jan 1, 2005

By David Colloby, Darelle T. Janse van Rensburg

Premature coating failures of new and refurbished structural steelwork of clarifiers have been a common occurrence at power generation plant in recent years. Several of these failures have ended in disputes regarding which party was actually to blame for the early degradation of the coating system, i.e. quality of the power station?s water, poor application, substandard materials, outdated corrosion protection specifications, etc. Having investigated several of these premature failures, it is clear that the corrosion protection of clarifier steelwork is a highly complicated process and that the painting work needs to be closely monitored in order to ensure long-term protection by whichever product that is applied. The need for quality control inspections during the painting of the plant is often underrated during the project planning stage, also the importance of detailed corrosion protection specifications that consider not only the practical application of the materials, but also the quality control responsibilities of the Contractor, End User and Third Party Inspectorates that may be involved. This paper considers the application constraints of coatings to clarifier structural steelwork and importance of stringent quality control procedures in order to ensure the long-term performance of the corrosion protection systems.

Jan 1, 2006

By D. Govender

Theoretical flotation models suggest that there is a positive relationship between bubble-particle collision rates and turbulent kinetic energy dissipation. Fine particle flotation performance is generally enhanced by increased collision frequency and hence higher energy dissipation. Contrarily, increased turbulence in the rotor-stator region is related to higher detachment frequency of the coarser size range. Therefore, the optimal modes of recovery for the 'fine' and 'coarse' size classes appear to be diametrically opposed. Industrial applications have previously confirmed that applying greater power to flotation slurries yields significant improvements in fine particle recovery. However, recovery of the coarser size class favours a different flotation environment. An improvement in the flotation kinetics of the fine and coarse size classes, provided there is no adverse metallurgical influence on the intermediate size ranges, is obviously beneficial to the overall recovery response. Managing the local turbulent kinetic energy dissipation, and hence the power imparted to the slurry, offers the benefit of targeting the particle size ranges exhibiting slower kinetics. FLSmidth recently introduced the practical implementation of this concept. In principle, it decouples flotation regimes where fine and coarse particles exhibit preferentially recovery. In the case of naturally aspirated machines (Wemco®), it is referred to as Hybrid Energy Flotation? and incorporates at least three phases: > Standard flotation machines (standard energy input, rotor speed (r/min), rotor size/type) at the beginning of the row, where flotation is typically froth-phase limited and operational and set-up parameters have a limited influence on the recovery > Higher-powered flotation machines (high rotor speed, high-power rotor size/type) at the end of the row to improve fine particle recovery > Lower-powered flotation machines (low rotor speed, low power rotor size/type) to enhance coarse particle recovery. A CFD-based flotation model is used to highlight the effect of turbulent dissipation energy on attachment and detachment rates. Preferential collection zones for fine, and 'coarse' particles are predicted for both forced-air and naturally aspirated machines. The greater predominance of UG2 ore types, coupled with the skewed feed distribution of platinum group metals (PGMs) to the finer size fractions, suggests that PGM flotation circuits are not designed for optimal recovery across the size distribution. The application of the hybrid energy concept to PGM flotation offers a possible shift towards a more efficient flotation circuit solution through a managed distribution of energy.

Jan 1, 2013