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By V. Grujic, M. Grujic, D. Salatic

"Two areas are involved in the research work of the comminution process (crushing and grinding). The first one involves the changes of the size class distribution values that are definded by the differential equations in the function of the ore property and working conditions. The second area involves the comminution of the different levels in order to optimize the working parameters and to decrease the operational costs in the grinding process.We have studied, in detail, the possibility of functioning the crusher at the maximal loading, over 4500 kN, ball mills with diameters larger than 5.0 m and semiautogenous mills with diameters larger than 10.0 m.Using the computers, we have achieved the maximal loading range of the crusher, over Fc ? 4500 kN in the crushing process. In the grinding process, using the adequate differential equations in the automation process, we have established the correlation between the pulp mass capacity in the mill, pulp dencity, ore fineness in the pulp and recirculating ore charge.With the appopriate text, equations and graphs, this paper shows the results of our several years research work in the laboratory and in the ore comminution plant of Majdanpek Copper Mine."

Jan 1, 2003

By Leon Lorenzen, Charlene Gokhale

"In excess of 24 x 106 tons (Eskom, 1997) of coal-derived fly ash is produced annually in South Africa for the production of electric power. A large quantity of this ash is disposed of as a solid waste in landfills, thus posing a serious environmental problem. Due to the shortage of landfill sites, new ways of utilising fly ash are needed. Recently several authors have shown that various combustion fly ashes can be converted into zeolites to obtain industrial products with applicability in environmental management. Geopolymerisation has emerged during the last few years as a possible solution to some waste stabilisation and solidification problems. henolic compounds have been shown to be toxic to soil microorganisms at the parts-per-million level. Indeed several of the organic compounds classified by the U.S. Environmental Protection Agency as priority pollutants, are phenols. Immobilisation of phenols by adsorption on zeolites and encapsulation in a geopolymer appears to be a promising solution to this problem.This paper reports a technique for the production of a low-silica sodium zeolitic material from fly ash (zeolite NaP1), and its application for the stabilisation of phenols by adsorption and subsequent encapsulation in a geopolymer matrix. A commercial zeolite, clinoptilolite was also utilised as an adsorbent. Due to their uniform pore sizes and large surface areas, zeolitic materials are suitable for ion exchange and adsorption of certain organic substances. Adsorption data show that the commercial zeolite, clinoptilolite was an effective adsorbent for organics. Adsorption data showed that between 51.2 ppm and 74.3 ppm of chlorophenol or between 15.4 ppm and 32.5 ppm of phenol could be adsorbed. Physical encapsulation of the coated zeolite loaded with organic within a geopolymeric matrix increased the compressive strength of the matrix from 28.80 kN to 40.79 kN. Leaching data for the various geopolymer matrices with encapsulated and loaded zeolites show no organics being leached from the system at a detection level of 2ppm. According to the SABS these would have been acceptable organic concentrations within a waste water stream."

Jan 1, 2003

By Yuhua Wang, Haitao Zheng, Guangli Zhu, Yuehao Zhao, Fushun Yu, Dongfang Lu

"Spodumene, feldspar and quartz possess similar surface properties, which make the difficult to separate spodumene from other silicate minerals by flotation. The differences of crystal structure, surface property and floatability of three minerals were studied by various technical means. The results show that Li-O and Al-O bonds in spodumene structure are not strong and easy to be broken. However, Al-O and Si-O bonds in feldspar and Si-O bond in quartz are very strong and not easy to be broken. High contents of Al and Li on spodumene surface were found by XPS measurements, which is benefit for the adsorption of anionic collector. The surface energies of main cleavage planes of spodumene (110), feldspar (001) and quartz (001) are 1.88 J/m2, 2.97J/m2 and 2.68J/m2, respectively. Hence, the exposed surfaces of feldspar and quartz are not saturated and easy to adsorb OH- ions from solution and cause the lower IEP than spodumene. The contact angles of three minerals in water are lower than 16º, suggesting that the hydrophilicity of three minerals is high, and the order of hydrophilicity is quartz > feldspar >spodumene. Correspondingly, contact angles and flotation recoveries of spodumene are bigger than that of feldspar and quartz in presence of a combined anionic and cationic collector named YOA.INTRODUCTION Flotation technology plays most important role for the recovery of spodumene from pegmatite ore. Generally, spodumene with fresh surface is easy to be floated using soap and oleic acid as collector, and the best flotation pH range is 4.0 to 9.0. However, the flotability of spodumene will become worse when its surface was polluted by slime which produced by the weathering of spodumene and other silicates (Dresler et al. 1998; Moon and Fuerstenau 2003; Menéndez et al. 2004; Yu et al. 2015). In addition, the species of Ca2+, Fe3+, Mg2+ and other metal ions in pulp can not only activate the flotation of spodumene, but also the activation of gangue minerals, and then the flotation selectivity of spodumene from gangue minerals became wores (Wang and Yu 2007; Yu et al. 2014). In order to eliminate the negative effects of slime and metal ions on the flotation of spoddumene, the desliming and long time scrubbing with the addition of NaOH and Na2CO3 were adopted. Usually, NaOH shows the activation for spodumene flotation, and the recovery of spodumene increases with the increase of NaOH dosage. Na2CO3 can eliminate the non selective activation of Ca2+, Fe3+, Mg2+ ions in the pulp, and the concentrate grade of spodumene increases with the increase of Na2CO3 dosage. Anionic collectors such as chelants, hydroxamic acid, oxidized paraffin soap, naphthenic acid and oleic acid were widely used for the flotation of spodumene (Dresler et al. 1998; Moon and Fuerstenau 2003; Menéndez et al. 2004; Yu et al. 2015)."

Jan 1, 2018

By Olga D. Khmelnitskaya

The paper presents the results of research on the development of gold recovery technology from oxidized gold-copper ore of one of deposits in Russian Federation. Gold and copper grades in the ore are 9.5 g/t and 0.4%, respectively. Various options of flowsheets, such as direct cyanidation, thiourea leaching, flotation and gravity concentration followed by subsequent cyanidation of con-centration products, were tested. It was established that gravity-cyanidation technology with filtra-tion leaching tails and the use of solutions in the recirculation is the optimal option for ore treatment. The proposed flowsheet provides gold recovery for 91.0% at NaCN consumption 2.5 kg/t ac-cording to the results of pilot testing. Ammonia-cyanide gold leaching was also examined. In comparison with cyanidation, gold leaching solution in system NaCN-NH4OH-(NH4)2CO3 allows NaCN consumption to be reduced three times from 4.5 kg to 1.5 kg per 1 ton of the ore and provides the same gold recovery. Based on the laboratory and pilot plant tests results of gravity-cyanidation technology of gold dissolution, process design criteria were developed.

Jan 1, 2014

By Mary Stewart, Jim G. Petrie, Geoff Brent

"Life Cycle Assessment (LCA) is gaining increasing acceptance as a decision-support tool by which to evaluate the environmental performance of a product, process or service. This is evidenced by its inclusion in international policy documents (for example in the European Union’s Integrated Product Policy) and in environmental management standards (the ISO 14 040 series of environmental management codes relate to LCA). In response to this, the minerals industry has conducted a number of commodity-specific LCAs. These include studies for global production of a number of commodities including copper, nickel, aluminium and steel. In addition, a number of minerals companies profess to use LCA as part of their suite of project and technology assessment tools. Often, this collected use represents more a situation of “we do this because we’re told it’s good for business” rather than from any demonstrable evidence of this fact. This has led to a situation of much confusion and disillusionment within the industry, exacerbated by the obvious current limitations of LCA to accurately reflect the environmental performance of minerals and metals.Our point of departure here is that LCA, conforming as it does to the tenets of environmental systems analysis, is a valuable starting point, and that there is merit in exploring to what extent the methodology can be enhanced to better reflect the environmental performance of minerals and metals. Specifically, we explore here the further development of LCA to address the following:• Land Use issues• Consumption of Abiotic Resources including metallic and non-metallic minerals, water and soil)• Human and Eco-toxicity issues relating to mobility and bio-availability of metals• Salinityand address these through selected experimental and simulation case studies relating to energy- and base minerals production. Advances resulting from the United Nations Environment Programme/Society for Environmental Toxicology and Chemistry Life Cycle Initiative are presented in that they directly affect the application of LCA to mining, minerals and metals. Comments are offered on how best the mining and minerals industry might interface with future developments resulting from this Initiative in order that the Initiative can deliver outcomes which render LCA a useful tool for decision making in mining and minerals processing."

Jan 1, 2003

By A. V. Kanarskay?

The research is aimed at involving in the processing of poor platinummetal natural and technogenic raw materials. The purpose of the research is the creation of a multifactorial complex of innovations in the system of ore preparation and separation cycles, which ensure a high efficiency of flotation enrichment of hard-to-treat raw materials. In the usual practice of enrichment, minerals of the platinum group (PGM) of less than 10 microns in size are the source of inevitable process losses. For poor raw materials, it is precisely thin PGMs that are characteristic, their proportion sometimes being almost 100%, and their opening leads to the formation of a large amount of slime, which adversely affects the efficiency of flotation. To reduce the yield of slimes and increase the selectivity degree of the opening of the PGM in the ore preparation cycle, a dry grinding scheme and pneumoclassification of the milling material has been developed to obtain fractions of different fineness, density and morphology of the particles. From 2 to 5-fold reduction in the yield of slurries for various ores has been achieved. The separation cycle successfully tested are: flotation of fractions in separate cycles with a differentiated choice of the reagent regime; preliminary selective flocculation of slime fraction material; use of a new generation of bioreagents for flocculation and flotation. A new approach to subsoil research is protected by a patent. The dependence of the efficiency of biocollectors on the composition of biomineral extract from the processed raw materials, which forms the basis of new reagents, is established. The possibility of obtaining the degree of extraction of PGM, native gold and sulphides from finely ground pre-fractionated poor ores with the use of biocollectors of at least 85% is proved. With conventional reagents, the extraction of PGM is 12-23% lower, with the use of traditional ore-preparation apparatuses, the PGM recovery rate was halved. Methods for the long-term storage and preparation in industrial conditions of biocollector reagents that do not require the purification of waste waters from them have been developed. The developed multifactorial system of intensification of flotation enrichment can be introduced to recovery PGM from tailings of enrichment of titanomagnetite, chromite and copper-nickel ores.

Jan 1, 2018

The effect of the acid anion on chalcopyrite (CuFeS2) leaching has been examined, under care-fully controlled conditions, in a range of acids in stirred reactors and columns at pH 1. Solution speciation calculations were performed to determine possible rate controlling species. The relative leach rates of Cu from chalcopyrite can be explained quantitatively entirely on the basis of solution speciation without the need to invoke any rational relating to surface structure/speciation. The rate of Cu release is first order with respect to Fe3+ activity. The stirred batch reactor experiments at fixed pH 1, Eh of 750 mV (SHE) and 75? showed that chalcopyrite leach rates were rapid in both HClO4 and H2SO4 with 100 % Cu recovery after 73h and 97 h respectively. However, the leach rate in H2SO4 was slower as compared to the HClO4 leach due to a slower increase in the activity of Fe3+ due to the formation of FeSO4-. The presence of Cl- in the leaches (HCl and H2SO4 with NaCl added) led to a low activity of Fe3+, due to the high activity of FeCl2+, resulting in very low leach rates. For the column leach experiments dissolution of Fe and Cu from the pH 1 HCl eluted chalcopy-rite column with quartz proceeded at several times the rate of any other column (chalcopyrite with and without quartz and/or pyrite leached with H2SO4, HClO4, HCl). Three observations indicate that galvanic interactions are not leach rate controlling role: a) The rate of leaching was not uniformly increased for the non-quartz containing columns where the two sulfide minerals, chalcopyrite and pyrite, are in physical contact as compared to the analogous quartz containing columns where they are not; b) there exists a reasonable correlation between the rate of Cu release and the effluent Fe3+ activity for all columns thus indicating that the leach rate is determined by solution speciation; and c) in all cases the proportion of Fe to Cu leached indicates preferential dissolution of Cu over Fe. However, the proportion of Fe to Cu is either the same or greater than expected on the basis of the single mineral columns. This indicates that chalcopyrite is not dissolving preferentially to pyrite.

Jan 1, 2014

By C. Abbruzzese, F. Vegliò, S. Ubaldini, R. Massidda

"Gold solubilised during cyanidation can be recovered by precipitation (Merrill-Crow process) or by adsorption onto activated carbon, these being the techniques applied in industrial plants.Precious metals (Au, Ag) adsorbed onto activated carbon are extracted during a subsequent stage in aqueous phase, by various technologies, such as hot elution (70-80°C) or under pression desorption (100-130°), with hydro-alcoholic solutions.This stage is of great interest from an economic point of view, due to the high energy costs. Temperature represents the critical kinetic factor.The aim of this paper was to study the influence of different water/organic solvent mixtures (isopropyl alcohol, ethanol and ethylene glycol) on the desorption process.The experimental work was carried out on laboratory scale, using activated coconut carbon with different temperatures and extraction times, without adding cyanide.Best results have been obtained in this order: isopropyl alcohol > ethylene glycol > ethanol. Starting from gold concentration of about 5 g Au per kg of carbon, best kinetics resulted in 97-100% of gold extraction, after 8 hours of desorption, at a temperature of 80ºC."

Jan 1, 2003

By Atsushi Shibayama, Toyohisa Fujita, Luo Lin, Toshio Miyazaki

A novel process is developed in this study for separation of tungsten and vanadium from a leach solution of tungsten alloy scraps. Specifically, a magnesium salt combined ammonium solution is employed to precipitate vanadium and impurities in the purification of the leach solution. This separates vanadium from tungsten by rejecting tungsten in aqueous solution. Finally, tungsten is recovered as the form of ammonium para-tungstate (APT). Vanadium is recovered as the form of ammonium meta-vanadate(AMV).

Jan 1, 2003

By Peter N. Holtham, Geoffrey J. Lyman, The University of Queensland, Matthew S. Brennan, Vijay Subramanian, Rui X. Rong

"The cyclone would have a claim to be the commonest, least understood and most abused piece of mineral processing equipment available for study by researchers. It has certainly generated its fair share of publications – 1,000 in the last 60 years would be a fair estimate. However this remarkable degree of interest and scale of investigation is not reflected in our understanding of how they work; cyclones are still installed inappropriately and run poorly, which suggests that there are still things to learn about this deceptively simple process.In mineral processing there are two broad classes of cyclone: the hydrocyclone, used in classification, thickening and dewatering, and the dense medium cyclone, used for concentration by density. Although rarely studied together, the laws of physics presumably apply equally to both and so it seems that there would be interesting things to learn by considering them as a single class of device. The good news is that in recent years there have been spectacular advances in the computational and measurement tools available to study these devices, including computational fluid dynamics (CFD), tomography, and laser doppler anemometry (LDA), and some good progress has been made in an understanding of the fundamental principles involved.The JKMRC has made many experimental studies of hydrocyclones and DM cyclones, leading to useful empirical models. However some recent CFD and tomographic work, in association with work of other institutions, has thrown important light on the workings of these processes. Progress has also been made in novel designs of cyclone to achieve improved separating efficiency, based on an attack on the subprocesses believed to contribute to inefficient operation. This paper describes the work to date.Modelling of the dense medium and classifying cyclone was conducted using the Fluent computational fluid dynamics code. Three phase simulations of the dense medium application (air/water/medium) showed appropriate medium segregation effects but over-predicted the level of segregation compared to segregation measured by gamma-ray tomography. This is believed to be because the basic Algebraic Slip mixture model in Fluent does not model any back-mixing of the dispersed phase due to turbulence."

Jan 1, 2003

By Sami Makni, Ahmed Bouajila

"To remain competitive in an open market, mining companies are more and more requested to optimise their complex and highly multivariate processes. The increasing amount of process data, brought about by intensive use of instrumentation and the progress in computer data acquisition, enhances the need for more and more powerful and robust tools for the analysis and modelling of the process data. Now, with the emergence of multivariate data analysis (MDA) techniques, on-line clustering of mineral process behaviour is possible and could help in the extraction of valuable process operation indicators. MDA can be used in different mineral processes such as flotation, grinding, smelting etc. In this paper, the focus will be on grinding process as it is the one of the most costly node in the mineral processing scheme (i.e. power consuming) and it is a highly multivariable process. Particularly for primary grinding mills (SAG/AG), more instrumentation outputs and more powerful and significant process indicators are needed for efficient control and optimisation.MDA is a novel approach suitable for understanding mineral process behaviour compared to the traditionally approaches based on empirical and phenomenological modelling. Multivariate techniques can be used for several purposes. In this paper, the following objectives will be addressed:operation diagnosis: Shift differentiation and operation test differentiation can be showed by using MDA tools such as principle component analysis and factorial discriminant analysis.operation performance monitoring: operation regimes can be evaluated by clustering based on an economic criterion performance such as costs, tonnage, product quality, profit, etcIdentification of operation behaviour (monitoring) and selection of drift correction trajectories (control):MDA can be used to identify periods of unusual or abnormal process behaviour and to diagnose, if it is possible, causes for such behavior."

Jan 1, 2003

By D. Whittles, S. Kingman, K. Jackson, S. Bradshaw, N. Miles

The influence of microwave energy at high electric field strength on ore strength has been investigated. Two ores of varying mineralogy were treated in both multimode and single mode microwave cavities. After treatment, any change in strength relative to untreated ore was established. It was shown that in the multimode cavity reduction in strength was related to the applied power level. Results of tests carried out in the single mode cavities showed that, for both ores, reductions in ore strength > 50% could be achieved in very short periods (<1 second). Thermal stress analysis showed that the mechanism of microwave induced failure was the development of tangential stresses at the grain boundaries. It was concluded that operation at 915 MHz with high power and short residence times gives feasible scale-up possibilities.

Jan 1, 2003

By Benoit Clermont, Jan Lux

"Magotteaux and Anglo Platinum started a co-operation program with the main aim of establishing the optimum milling configuration measured in terms of throughput, fineness and energy consumption.For this purpose, a fully instrumented pilot milling plant, supplied by Magotteaux (Pty) Ltd, and equipped with a 0.9 x 1.0 m ball mill, was erected at Frank concentrator (Merensky Pt ore). The primary ball mills at Frank concentrator were surveyed in order to set the conditions for the base case. This data was then replicated in the pilot mill under the same configuration. Thereafter, a series of different parameters were varied in order to attempt to optimize the milling system.Only grate versus overflow discharge and open versus closed circuit will be discussed in this paper.It should be noted that this paper does not attempt to give a universal solution as to what milling configuration is optimum in all cases. The conclusions apply for this particular case and probably most others, but it would be advisable to consider each case on its own.CONCLUSION• Overflow versus grate dischargeAn overflow mill has a “pool” of slurry around the toe of the ball charge, which creates a counter lever to the ball charge. This will reduce the absorbed power in the range of 10-15% (depending on the case) and will consequently result in a coarser grind. The tests found a 4% gain in grinding efficiency (Wio) with an overflow mill but this is probably not significant.This lower absorbed power and coarser grind can be counteracted by increasing the ball charge (if below maximum) and/or by increasing the mill volume when removing the grate discharge (a typical grate takes up about 300mm of the mill length).• Open versus closed circuit"

Jan 1, 2003

By Osvaldo A. Bascur, J. Pat Kennedy

"The profitability of mining and metallurgical operations continues to lag behind that of other industries despite the technical advances that have occurred in recent years. A primary reason for poor performing in this economic sector is the lack of integration of mining and metallurgical information. The mine cut-off grade can be optimized if mining and metallurgical engineers have the data to optimize milling for the type of ore in hand.Integration of mine transactions, stockpile inventories, process flows and assays is the key to determining the economics for each blast strategy in a mining site. Real-time information from manufacturing assets greatly affects the profitability and flexibility of a company, but gross errors from faulty sensors, inaccurate instrument calibration, or incorrect process models may corrupt actionable information. New software tools can model the process, sift through available data to identify and eliminate gross errors, and use statistical data reconciliation to create materially balanced and consistent readings. The reconciled data is unified for use by both monitoring and decision making processes.Creating a real-time information environment where upgrade and change are allowed is becoming an accepted methodology to accelerate and simplify the integration of applications such as production monitoring, equipment performance management and yield and inventory management."

Jan 1, 2003

By Dave Deglon

"The Western Cape Mineral Processing Facility (WCMPF) is a collaborative educational initiative between the Departments of Chemical Engineering of the University of Cape Town, the University of Stellenbosch and the Cape Technikon. The primary objective of the WCMPF is to facilitate the education, development and graduation of suitably qualified engineering graduates and diplomates for the mining industry. The WCMPF consists of academics and Technical Officers in the Departments of Chemical Engineering of the three tertiary institutions. The Technical Officers are usually metallurgists, with several years of industrial experience. The main objective of the Technical Officers is to improve the practical education of mineral processing students. In addition, the Technical Officers are responsible for organising an annual mineral processing student field trip for students from all three tertiary educational institutions. In recent years the WCMPF has embarked on a number of additional initiatives aimed at improving the quality of mineral processing education. These include the development of several new pilot plant practicals, an initiative in pyrometallurgy, the introduction of novel ‘end to end’ or ‘integrated’ practicals and the use of mineral processing simulation packages to complement the practical training.The WCMPF has been functioning for well over a decade and, by virtue of this, might be considered a successful collaborative educational initiative. The WCMPF has played a key role in the education of over five hundred mineral processing graduates and diplomates. During this time period, the WCMPF has gained a body of internal knowledge which might be of benefit to other educational institutions, viz."

Jan 1, 2003

By S. J. Neethling

"Flotation is a complex process with many factors that influence the performance of a cell. This paper examines the impact of several key variables on the performance of flotation cells. The study makes use of a simulator for the froth phase of the flotation vessel, as the main purpose of this study is to separate the impact of different variables from one another.In experiments it is very difficult to separate the effect of variables from one another as a change in a singe input parameter, such as air rate, invariably also affects many of the other key variables, such as bubble size and bubble bursting rates. This interaction between variables makes it very hard to experimentally separate the impact of, for instance, the air rate from that of bubble size or bursting rate. In the simulator, though, it easy to make independent changes to these variables.In order to achieve this a base case simulation that is typical of many of the rougher cells found in sulphide flotation circuits was carried out. Four key variables, air rate, incoming bubble size, surface bubble size and the fraction of the bubbles flowing out of the cell unburst, were varied in order to obtain the system’s response.The most significant results were obtained when the bubble size was varied. An increase in the incoming bubble size has the effect of reducing the pulp zone recovery, but increases the froth zone recovery. If it were possible to vary the incoming bubble size without influencing the overflowing bubble size, the impact of the change would be unclear because of these two competing effects. The effect of a change in the overflowing bubble size has an opposite effect on the froth recovery, with larger bubbles resulting in lower froth recoveries."

Jan 1, 2003

By Shailin Lalloo, Allan B. Nesbitt

"Gravity separation by centrifugal equipment, particularly in the mineral processing industry is a novel approach of optimising product recovery. The manufacture and sale of centrifugal equipment by recently established companies is now beginning to have a significant impact on the industry. Some benefits of operating at increased gravity include: reduced environmental issues, a shorter lead time, lower capital cost and improved recoveries of elemental mineral before entering the grinding circuit.Of topical discussion is the use of centrifugal separators for the recovery of less valuable minerals that will form a greater proportion of the feed compared to traditional scalping circuits where the gold content is extremely low. This ultimately results in the centrifugal system having to have a greater mass pull. In addition, the relative density difference between gangue and valuable mineral is likely to be less and therefore modelling and optimisation of this separation process will be necessary. Some researchers have muted using fluidisation models to model the forces present in the separation zone of a centrifugal separator2. It is not unusual for the manufactures of centrifugal separation equipment to use fluidisation terminology to describe what happens in the separation zone. Most fluidisation models are based on the empirical/classic relationship between superficial fluid velocity and voidage postulated by Richardson and Zaki. However, no researcher has proved the effectiveness of this relationship in an increased gravity Environment."

Jan 1, 2003

By Johann Botha, Niel de Clerk, Tony B. Lange

"PROCESS COMPLEXITYDespite many years of research and development, mineral and metallurgical processes are in general highly complex and still difficult to understand and control. One of the biggest factors contributing to this complexity is the highly non-linear, multivariate, chaotic nature of such processes.This complexity is magnified in production environments where business optimisation rather than beneficiation is the primary objective. Return on investment, sustainability, and social issues such as Aids and the environment all form part of the goal hierarchy of industrial concerns. In addition, international competition and price volatility all have a huge impact on these processes in terms of operational constraints.Therefore the optimisation and control of beneficiation processes must take into account many factors other than pure process variables such as flow rates and levels. For example, commodity prices and client requirements all need to be added to the control problem, which together with incomplete process knowledge and non-linearities etc., make automation and optimisation extremely difficult.The ideal solution is to have a controller which in addition to performing full non-linear constrained optimal control can at the same time take into account other non-process factors such as price and client satisfaction."

Jan 1, 2003

By Jeremy Bosman, Niel Lourens

"Cyclones are used in four main applications in primary wet heavy mineral processing plants i.e. upfront desliming, densifying, and concentrate stacking and tails deposition.UPFRONT DESLIMINGMany heavy mineral ore bodies are associated with high slimes varying from 15 to 60%. The increased viscosities arising from the slimes impact negatively on heavy mineral recovery in the spiral plant. Recoveries can be reduced by up to 10%. Cyclones have proven to be able to remove slime efficiently with acceptable loss of valuable heavy mineral in the overflow. For low slime applications, typically below 25%, it is possible to achieve the desired results using a single stage of cyclones, whilst for higher slimes, two stages of cyclones are required. The overflow of the primary stage is retreated through a second stage to minimize heavy mineral loss."

Jan 1, 2003

By Ronald Smeink, Ton de Gouw

"Reagents are an important cost-factor in the flotation of minerals. The mechanism of collectors and frothers has been studied extensively, but on depressants – probably the biggest cost-factor in the reagent suite – very little is actually known. Theories are frequently faced with the bare facts, pointing in another direction. Fundamental research is complicated by the fact that the amount of possible interactions in the flotation cell is almost unlimited and makes “change-one-parameter-at-a-time” experiments questionable and at least difficult to interpret. Also, the adsorption of depressants on the ore is very strong and desorption merely impossible. Detection methods therefore tend to be indirect and – therefore - non-specific about the location of the depressant on the ore.Depressants are supposed to adsorb selectively on gangue minerals; not on the valuable minerals in the froth. In order to be able to develop better and ‘’smarter’’ depressants, an analytical method is therefore required that will enable to detect which (=qualitatively) depressant, in which concentration (=quantitatively) sits where exactly (= selectively) on the mineral surface. (Answering the question: ‘’ Which minerals is located direct under the depressant?’’)And also: does the depressant compete with other reagents for that location? (like collectors) This analytical method is under development. The actual status of the method is promising and the results will be shown."

Jan 1, 2003