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By Peter J. Coghill, Michael J. Millen, Brian D. Sowerby, Kirby D. Cunningham

"CSIRO Minerals has developed an integrated particle size analysis system for deployment in the grinding circuits of minerals processing plants. The system includes a slurry sampling station, a de-aeration tank and an ultrasonic particle size analyser (UltraPS). The UltraPS analyser is based on ultrasonic attenuation and velocity spectrometry combined with gamma-ray transmission. The technology is applicable to the measurement of 0.1 to 1000 µm diameter particles directly in highly concentrated slurries without dilution. The analyser incorporates a gamma-ray transmission gauge utilising an ultra-low activity radioisotope source that is exempt from International Atomic Energy Agency (IAEA) and Australian licensing regulations.The UltraPS analyser consists of a submersible probe and an electronics package. The probe can be immersed directly in a minerals processing plant stream if the aeration level in the stream is low. For applications where a de-aerated slurry stream is not available, CSIRO has developed an integrated system that includes a sampling station, a de-aeration tank as well as the UltraPS analyser itself. A schematic drawing of the continuous flow gravity fed system is shown in the figure. A commercial sampling system is used to supply slurry at a rate of 2.5m3/hr to the deaeration tank. The aim of the de-aeration tank is to remove air in the slurry to a level where meaningful particle size measurements can be performed. The tank volume is about 0.2m3, thus giving the slurry flowing through the tank a mean residence time in the tank of approximately five minutes. Tests at a number of concentrators have shown that five minutes is sufficient time for slurry to de-aerate to a level where ultrasonic measurements can be made. The tank incorporates an ultrasonic level detection sensor and flow to the deaeration tank is adjusted based on the level of slurry within the tank. The UltraPS probe is mounted through a flanged section of duct, which is bolted to the bottom of the de-aeration tank."

Jan 1, 2003

By Yuri Yemelianov, Stanislav Balikov, Alexander Epiforov, Andrey Boldyrev, Andrey Bogorodsky

"Test work was carried out using copper gold-bearing flotation concentrate with 6.85%Cu, 14.30%Fe, 20.70%S and 2.34%As. Gold and silver grade in the concentrate is 54.6 g/t and 92 g/t, respectively. Gold and copper are valuable components in the concentrate. Gold is partially associated with pyrite and fahlores. Copper in the concentrate can be found as tennantite (Cu12As4S13). The 71% of gold from the flotation concentrate is recoverable by cyanidation with simultaneous cyanide consumption in the amount of 96 kg/t. The major reason of refractoriness is that gold is fine encapsulated into sulfides and the presence of cyanicide-copper. The concentrate ground as much as 95% minus 10 µm was treated using low-temperature POX at the temperature of 100±5°C, L:S ratio of 5:1 and the process time of 1-5 hours. Residual sulfide sulfur in the cake is 2.28% which is 89% sulfide oxidation. The highest copper recovery to POX solution is 91%. It was found that gold recovery to cyanide solution is 85-94% during alkaline pre-treatment of POX cakes followed by cyanidation. In this case, cyanide and lime consumption is 75-90 kg/t and 120 kg/t, respectively. In order to recover precious metals from POX cakes leaching using sodium sulfite was carried out. Test work was conducted at varied reagent concentration, L:S ratio and leaching time. Gold and silver recovery achieved was 85-95% and 59-63%, respectively."

Jan 1, 2014

By Shuji Owada, Yang Geng, Natsuko Kuroki

Micro-bubble flotation is considered to be an ideal method for the separation of fine or ultra-fine particles, which are difficult to be separated with conventional flotation and other solid separation technologies. Micro-bubble flotation can increase the probability of bubble-particle collision more than conventional milli-bubble flotation. However, there are also some problems. For example, it is known that the rising velocity of micro-bubble is quite low; therefore, the flotation rate reduces. And also, the bubble-particle adhesion probability becomes lower than that of milli-bubble flotation, which is proved in our prior research. In this paper, we applied ultrasonic irradiation to the micro-bubble flotation system in order to solve the above problems and focused on the bubble-bubble and bubble-particle interactions. For clarifying the behavior of bubble-bubble interaction, bubbles behavior was recorded by high-speed camera under irradiation of various ultrasonic frequencies. As a result, in the case of bubble-bubble interaction, it is proved that bubbles are highly coalesced by ultrasonic irradiation especially in the lower frequency and it can enhance more precise separation. In the case of bubble-particle behavior, it is found that the floatability become higher with the ultrasonic irradiation of higher frequency, and it is indicated that ultrasonic irradiation might improve the bubble-particle adhesion probability. Additionally, it is also found that the apparent CMC of the micro-bubble flotation under the ultrasonic field become much lower with higher frequency than with lower frequency, and it is suggested that the dramatic improvement of hydrophobization is achieved.

Jan 1, 2014

By Jian Zhang, Yongfu Yu, Fuguang Zhang, Liping Che

There is one large-scaled iron ore deposit in Inner Mongolia of China, but it is very complex which includes about 170 types of minerals and 71 elements. The hematite, magnetite are mainly iron ores. It is difficult that the iron mineral can be separated efficiently by common dressing methods due to the complexity, and the iron concentrates in the mineral processing factory contains many foreign substance such as K, Na and Si so that the process in iron mill is influenced because of the foreign substance, so it is vital reducing the foreign substance.

Jan 1, 2003

By Bertil I. Pålsson, Sture V. Persson, Kent T. Tano

"Grinding is one of the most energy consuming unit operations and is also a very inefficient and costly process. Therefore, it is of great importance to run the grinding process as efficiently as possible. The most common way today to control grinding processes is by measuring the power draw of the mill and try to keep it at a maximum level. However, some studies (Kawatra, 1989, Koivistoinen, 1989, Moys, 1989) have shown that this measurement doesn.t reflect everything that takes place inside a mill. Among other parameters like slurry rheology, temperature and charge behaviour, the volumetric filling of a grinding mill seems to have a large influence on the grinding efficiency (Herbst, 1988, Koivistoinen, 1992, Vermeulen, 1988). A problem in attempting to measure those parameters has been to get a sensor that is both robust and sensitive enough for continuous on-line measurement.This paper presents a method for the measurement of the apparent filling level in a pilot ball mill equipped with the Metso Continuous Charge Measurement system (CCM). In this technique a strain gauge sensor is mounted on a flat steel spring which is fitted into a recess underneath a lifter bar. In addition, a conductivity probe, the Boliden Grinding Measurement System (GMS), is mounted in another lifter bar with the purpose of comparing the two measurements. To visualise the behaviour of the charge a DEM modelling technique is used.The results indicate that the system is capable of following the normal variation that occurs in the mill. The signal also very well reflect changes in operating variables such as ball charge level, pulp density and rotational speed. By studying the nature and different features of the signal one can get a better understanding of milling circuit dynamics. Another feature of the technique is the possibility for an operator to continuously follow the grinding process and thereby run the process under optimal conditions."

Jan 1, 2003

By Zhou Yucai, Zhou Jing, Zhu Yimim

"In this article, research on the beneficiation process for a carbon containing copper-molybdenum deposit in Henan province has been carried out. The elemental composition, mineral composition and relative content, characteristics of embedded and symbiotic relationship, the forms of the copper-molybdenum particlesand their disseminated features, and particle size distribution have been worked out. Flotation behavior of copper-molybdenum mixed flotation and separate flotation in the systems of different collectors and depressants, and the influence of different flowsheets on the copper-molybdenum separation have been investigated by actual ore flotation tests, The separation problem of copper-molybdenum for a carbon-containing copper molybdenum ore has been solved.INTRODUCTION In this paper, technological mineralogy, small experiment of flotation recovery of copper Molybdenum ore, and expansion experiment of mineral recovery of copper Molybdenum ore are introduced. (1) The results of process mineralogyshow that the content of copper is 0.42%, molybdenum is 0.021% in the raw ore, they mainly exist in the form of sulfide, with low oxidation rate. (2) The results of flotation tests show that the combination of butyl xanthate and isopropyl ethylthionocarbamate reagents is effective collector of copper-molybdenum mixed flotation for carbon copper molybdenum, (3) When the grinding fineness is -0.074 mm taking 71%, and regrinding fineness is -0.038 mm taking 85%, the flowsheet of first copper-molybdenum mixed flotation and then regrinding rough concentrate and last separation flotation of copper and molybdenum was adopted, which realized the effective separation of copper and molybdenum for carbon-containing copper molybdenum ore. Good flotation indexes were gained with copper concentrate containing 20.96% copper and copper recovery 90.06%, and molybdenum concentrate containing 46.78% molybdenum with molybdenum recovery 72.68%. (4) The seven days average concentration index of scale-up the continuous dressing experiment is as follows, the copper content in copper concentrate is 20.16% and the recovery is 89.61%; the molybdenum content in molybdenum concentrate is 24.58% and the recovery rate is 74.09%."

Jan 1, 2018

By J. T. Liu

Packing in a flotation column is one way to increase separation efficiency and effective descending flotation-column height. In this paper, the difference between filling packing and sieve packing is described, and the flaws of filling packing in flotation columns in industrial application are pointed out. A change of flotation process and its effect on flotation results are reported. Based on sieve-plate filling, a high-efficiency mixed packing mode consisting of screen-plate packing and honeycomb-tube packing has been proposed, with the packing mode optimized in the cyclonic static microbubble flotation column in the separation zone. In the mixed packing mode, the honeycomb tubes are used to reduce the vortex effect at the base of the column and weaken the radial dispersion of jetting bubbles, and the sieve plates are used to comminute bubbles in the separation zone, to lengthen the bubble migration path, and to stabilize the foam layer. The superiority of honeycomb-tube packing is analyzed using bubble-particle collision theory, and the dynamic equations of collision probability are derived. The role of mixed packing in guaranteeing mineral recovery is analyzed by the axial dispersion method, and a dimensionless axial dispersion model is derived. When a high-turbulence flow is maintained, a static separation environment is formed in which secondary mineral processing is rendered more effective. In this way, a nonlinear separation environment is formed in the flotation column. Finally, mixed packing was applied in an industrial test. A large vortex developed at the base of the column. It was observed that the bubbles in the radial flow were homogeneously dispersed, the residence time of the pulp was prolonged, and the froth layer became thick and stable. Based on the test data, it was found that the sieve packing has the potential to yield a product of approximately 25.83% copper concentration with 91.78% recovery from a feed concentration of approximately 0.727%. If mixed packing were used, the product concentration could be further increased to 27.60% from a feed of approximately 0.739% concentration with 93.38% recovery.

Jan 1, 2014

By Kalle Härkki

Sustainability principles in the minerals industry are now becoming more and more important from the perspective of securing a license to operate and enhancing environmental, economic and social performance. This trend is also setting new challenges for the design and operation of future concentrator plants. It is evident that ore grades are declining and ores are becoming more complex requiring new technology innovations and holistic approach for process optimization. There is a demand for more energy-efficient process technologies especially in comminution that is the major energy consuming unit operation in the process chain. Energy is not only a major source of cost but also contributes significantly to the carbon and environmental footprint. There is also an increasing awareness that more intelligent water management is required for reduction of fresh water consumption and mastering the impacts of process water recycling will cause for process performance. In association with water recycling, tailings disposal is an integral part of concentrator plant representing significant environmental and economic issues to the operation. This presentation will discuss general trends and challenges of future minerals processing plants and how innovative technology solutions and better integration of unit processes in conjunction with intelligent process control would contribute to meeting the sustainability challenges.

Jan 1, 2014

By Bertil I. Pålsson, Sture V. Persson, Kent T. Tano

"Autogenous (AG) and semi-autogenous (SAG) mills often operate in an unstable state because of the difficulty to balance the rate of replenishment of large ore particles from the feed with the consumption in the charge. This has led to an increased interest in obtaining an accurate and direct measurement of mill load and the behaviour of the mill charge. A problem in attempting to measure those parameters is getting a sensor that is both robust and sensitive enough for continuous on-line measurement.Techniques that measure the force acting on the lifter when it hits the charge inside the mill have got an increased interest recently because of the ability to combine it with DEM modeling. This paper presents a method for the measurement of the apparent filling level in a pilot ball mill equipped with the Metso Continuous Charge Measurement system (CCM). In this technique a strain gauge sensor is mounted on a flat steel spring which is fitted into a recess underneath a lifter bar. In addition, a conductivity probe, the Boliden Grinding Measurement System (GMS), is mounted in another lifter bar with the purpose of comparing the two measurements. To visualise the behaviour of the charge a 2D DEM modelling technique is used with Metso HFS software.The pilot mill is a grate-discharge mill, equipped with 12 rubber lifters of square size 0.1 m, face angle 45 degrees. Steel balls in the size range 10-30 mm and density 8000 kg/m3, are used in the experiments. Test material is a hematite pellet feed, d50 around 45um, chosen to get stable grinding conditions with respect to feed size variations.The experiment is meant as a first test of the equipment’s performance, and to study how the sensors respond to changes in some operating variables. To get an understanding of, and distinguish between correlation and causality, experiments are performed according to a full factorial design with two levels, and in addition two replicates of the experiments at a center-point in the charge level setting."

Jan 1, 2003

By T. J. Chen

Stone coal containing vanadium is an important vanadium resource in China. Roasting and oxidation of vanadium is the foundation for extracting vanadium from stone coal. This article takes stone coal vanadium ore in Tongshan of Hubei Province as research target to conduct oxidation roasting test on it by using a self-developed low-sodium compound additive and a new optimized technology. Firstly, use potentiometric titration, X diffraction, energy spectrum and electron probe to study valence change, occurrence and phase transition of vanadium during oxidation roasting process. On this basis, primary work is done on oxidation kinetics of vanadium by exploring the steps that control reaction rate during vanadium oxidation process and determining the related dynamic parameter ? apparent activation energy. The study shows that occurrence of vanadium in stone coal of Tongshan is mainly in illite, and that the result of phase transition in roasting process is disappearance of illite containing vanadium, formation of soluble vanadate and potassium feldspar, albite. It further demonstrates that oxidation process of vanadium is step by step (V(?)? V(?)? V(?)), and its oxidation reaction is controlled by diffusion kinetics whose dynamic apparent activation energy is E1=81.19kJ.mol-1.

Jan 1, 2014

By P. V. Malyarov

"This paper examines the grinding and wear processes in drum mills. A summary of the industry’s long-term experience with the proposed linings is presented. A method is proposed for assessing the efficiency of the grinding energy distribution between the successive stages. A case study is presented of grinding energy redistribution at Talnakh Concentrator by replacing spiral classifiers with a drum-type hydraulic screen. The problems of the kinetics of grinding processes in ball mills and semi-autogenous (SAG) mills are examined. It is demonstrated that in ball mills the feed particles are disintegrated by triaxial compression in the mill zones where discrete slippage of the charge occurs at major force interactions between the layers. Mechanism underlying increases in the specific energy consumption in grinding circuits based on SAG mills is shown.The problem of improving the throughput and reducing the specific energy consumption in mineral feed grinding is highly relevant because of the significant energy intensity. Up to 80% of the consumed energy is used to disintegrate ore fed into the drum mill. At all development stages of the drum mill grinding theory, the researchers have paid a great deal of attention to studying the patterns of the charge motion and the kinetics of the feed particles disintegration processes. In [1], it was shown that, due to the slippage between the charge layers being lifted, drum mills at concentrator plants operate in a mixed cascade and waterfall mode. A feature of the mixed mode is the toe zone, where the charge contacts the lining and the transition to a circular path takes place. Studies of the charge motion in the toe zone made it possible to develop a method for designing cross-sectional profiles of lining plates [2] for ball mill drums. The method is based on the principle of interaction between the balls and the lining, where the non-working rear surfaces follow the relative motion path of the balls before impacting the lining, while the working surfaces are orthogonal to the rear ones. Lining with the proposed profile provides contact with the charge and slippage-free transition to a circular path. This ensures an longer service life of the lining, a reduction in specific energy consumption, and an increase in the mill’s feed rate. The proposed method is applicable when designing lining plates of various materials. Steel liners with the proposed profile have been successfully operated [3] for more than 40 years at a number of projects in the industry."

Jan 1, 2018

By G. P. Wong

"The Inco Matte Separation process was the first commercial application using mineral processing techniques to separate nickel from copper from a slow-cooled matte in Sudbury since 1945. In Inco Sudbury operations, bulk sulphide concentrate containing chalcopyrite, pentlandite, pyrrhotite and some gangue minerals is flash smelted and converted to Bessemer matte. During the controlled slow-cooling of the Bessemer matte, discrete mineral grains of new mineral phases are formed: copper sulfide precipitates as chalcocite (Cu2S), nickel sulfide as heazlewoodite (Ni3S2) and a Cu-Ni-Fe alloy is also formed. Flotation is employed to separate Cc from Hz under high lime conditions (pH>12) with diphenyl guanidine (DPG) as both collector and frother.A simplified matte separation flowsheet is as follows. After grinding, the Cu-Ni-Fe alloy is removed by magnetic separation. All precious metals are recovered in the metallic alloy. Following the rougher flotation, a Cu concentrate is produced after cleaner and re-cleaner flotation in mechanical and column cells. Two Ni concentrates are produced: a high-grade Ni product containing less than 0.8% Cu from the scavenger column tails and a low-grade Ni product containing 5% Cu from the middlings circuit tails. A stream containing the inseparable Cc and Hz from the middlings circuit is generated and recycled back to the smelter. The quantity of this stream is typically about 3% of total feed and can be as high as 5%, greatly decreasing the overall matte separation efficiency. The large mass of the recycle stream is a direct result of poor Cc/Hz separation selectivity in the middlings circuit. The middlings circuit, consisting of a thickener, a regrind mill and two columns, processes two streams: cleaner tailings and scavenger concentrates. The thickener contributes significantly to oxidation due to the long residence time of the pulp in this unit."

Jan 1, 2003

By B. K. Saikia

A preliminary attempt has been made to study the particle size distribution (PSD) of minerals in one of the industrially important pulverized Indian coal sample using computer-controlled scanning electron microscopy (CCSEM). The results show that clay minerals, quartz, pyrite, and pyrrhotite form the bulk of the mineral matter. Minor minerals, such as calcite, dolomite, ankerite, barite, oxidized pyrrhotite, and gypsum are also observed in the coal sample. The PSD of the included minerals is generally observed to be finer than that of the excluded ones in the coal. Thus, the coal rich in included minerals has more small mineral particles, which may affect its reactivity. The proportion of included to excluded is found to be higher in major cases. Si is found to be mostly occurred as quartz and clay minerals, while Al mostly occurs as silicate minerals. Fe is primarily present as iron sulfides, iron oxide, and Fe-Al-silicate. S is partitioned into iron sulfides and gypsum. Most Ca occurs as carbonates and gypsum, with a minor fraction associated with clay minerals. Mg is found to be mainly present as dolomite and clay minerals, with a very minor fraction present as ankerite. The majority of alkali elements are associated with aluminosilicates. P is mostly associated with kaolinite and/or present as more complex compounds containing Al, Si, and other elements as apatite are found to be absent in the coal studied. Ti is mainly present as rutile and kaolinite. The geo-chemical association of the trace elements has also been discussed. Keywords: minerals, Assam coals, Indian coals, CCSEM study

Sep 1, 2012

By N. I. Tyushkova

This is a brief survey of the technological solutions for deep cleaning of baddeleyite?s concen-trate. Baddeleyite is part of kamaphorite of composite apatite-magnetite ore in alkaline-ultrabasic mountain range of Kola Peninsula. Baddeleyite?s concentrate, which is being produced by Kovdorsky GOK (ore mining and processing enterprise) contains 97.5%~98.5% (Zr?2 + ?f?2) and also scandium oxide (0.05%). It is usually used without any chemical processing. World demand for zirconium oxide is constantly on the rise. Its consumption grows in ceramic industry and in high-tech spheres. That?s why the demand for its purity is very important nowadays (additional cleaning from phosphorus, silicon, iron, aluminium). The mechanism and kinetics of interaction of activated bad-deleyite with sulphuric acid has been studied as well. While applying method of mathematical mod-eling it was confirmed that the mechanical activation is effective for the intensification of sulphation process of baddeleyite?s concentrate with the aim of purifying it from dirt. The use of the calculated optimal regimes allows to reduce such technological operation factors as: temperature, the du-ration of process, the sulphuric acid consumption. It also allows to determine the conditions of anticipatory abstraction of scandium and main dirt in solution in comparison with zirconium oxide.

Jan 1, 2014

By F. L. Mentg

The utilization of acid leaching tailings was studied. It is obvious that the Fe in acid leaching tailings can be leached into solutions as Fe2+. In this paper, the influence of conditions, including the concentration of ferrous sulfate, pH, temperature and velocity of air flow was investigated. The optimum conditions for preparing seed crystal are as follows: the concentration of ferrous sulfate is 20 g/L; pH is 9.5~10; reaction temperature is 10~20?; velocity of air flow is 0.4m3/h. The optimum conditions for preparing iron oxide red are as follows: the concentration of ferrous sulfate is 5 g/L; reaction temperature is 80~85?; velocity of air flow is 0.13m3/h. At last, the product of iron oxide red could be prepared by ammonia method.

Jan 1, 2014

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 V. G. Prikhodko, G. I. Sukhinin, I. V. Yarygin, A. V. Fedoseev, S. A. Novopashin

"The first experiments on the vacuum drying of spherical clay sample are presented and the theoretical model of the process is considered. The model is based on the solution of the heat and the moisture transfer equations with the effective thermal conductivity and water diffusion coefficients for wet porous clay-like medium. The time and radial dependence of the temperature and the moisture were calculated for different initial conditions. The results obtained for the time dependence of the moisture content are in good agreement with the experimental results obtained in the initial period, when all the moisture in the sample did not freeze to form an ice crust. INTRODUCTION Capillary-porous materials very often occur in nature and in industry. A porous medium is a solid matrix with voids, or pores, which are continuously connected. These pores are usually filled with fluids or moisture, water vapor and air that can pass through the medium because the voids are interconnected. The void fraction in the solid matrix is referred to as the porosity. Porosity or void fraction is a measure of the void (i.e. ""empty"") spaces in a material, and is a fraction of the volume of voids over the total volume. The moisture content in porous media determines the properties of the porous body, its mechanical and thermo-physical properties, such as density, plasticity, viscoelasticity, swelling, cracking, and so on. Complex processes of heat and mass transfer occur in porous bodies when they are heated or cooled, during drying or freezing (Luikov,1966). The course of these processes depends essentially on the physical-chemical composition of the solid matrix of the porous body, on its fractal dimension, porosity and morphology. The clay and clay minerals are the most important porous materials in the history of the mankind (Mukherjee, 2013). Clay is a very fine grained, unconsolidated rock matter, which is plastic when wet, but becomes hard and stony when heated. It has its origin in natural processes, mostly complex weathering, transported and deposited by sedimentation within geological periods. Clay is composed of silica {SiO2), Alumina (Al2O3) and water (H2O) plus appreciable concentrations of oxides of iron, alkali and alkaline earth, and contains groups of crystalline substances such as quartz, feldspar, and mica. Building materials, bricks, and tiles, pottery, porcelain and faience are made from clay. Clay is used in the food and medical industry, and, not least, in the mining industry as a carrier containing aluminum, silicon and other valuable elements, as well as metals (copper, gold) as constituents, contained in the pores in the form of micro- and nano-particles or grains."

Jan 1, 2018

By X. M. Yu

A large amount of polluted sludge is produced by a nonferrous metal factory after treating waste water with lime/ferrous salt. The concentration of arsenic in the dried sludge is high to 5.84%, a toxicity test is taken on the sludge according to GB5085.3-2007 and the extraction content is 15.75mg/L, which surpasses the arsenic extraction standard [As]=5mg/L, the sludge is categorized as hazardous waste. If put outside without disposal, it would be very harmful to environments. Here we report an optimum protocol to extract arsenic; S2- alkaline liquor is utilized to treat the arsenic sludge. At 85?, 10L 7% S2- liquor is added into 1kg dried sludge and the resulting mixture is stirred for 120min at 250r/min, then separated by centrifugation and the compressed waste residue dried naturally. The average arsenic content is 1.40mg/L, lower than GB5085.3-2007 Standard and arsenic-free residue is consistent with GB18598-2001 Standard, which can be bury safely. The extracted arsenic is transferred into copper arsensite for use as addictive in copper electrolysis and the waste water can be recycle after calcium is removed.

Jan 1, 2014

By Malcolm Mudge

"One of the oldest mining areas in the World exist in Africa and the Middle East. This area is being exploited by foreign and local mining entities. Several large plants, both foreign and local as well as small operators, conduct their mining business on a scale which would be could be prohibited in any other part of the world. Relatively recent European disaster with tailing disposal and breakout has highlighted the problem.More important to the author is that the presence of foreign entities in zones which have not remedied the situation but has heightened the concern due to those entities using similar outrageous methods in treatment of waste. The abject misuse of technology cannot be permitted to continue and the lack of any metallurgical knowledge in the treatment of gold ores is considered deplorable for the majority of third world countries.The destruction of cyanide is simple and straightforward and requires no special skills. In South America, we developed a system that is modular, compact and can be operated in batch mode to cater for several clients, as required. Larger installations would require a separate module, as treatmentwould be on a continuous basis."

Jan 1, 2003

By A. Morrison, D. Mesa, P. R. Brito-Parada

"Froth flotation is the most widely used mineral separation technique. It is based on the relative hydrophobicity of valuable and gangue particles. In a flotation tank, two distinct zones can be identified: the pulp and the froth. The pulp is a turbulent region in which hydrophobic valuable particles attach to air bubbles while hydrophilic gangue particles remain in the slurry. As the particle-laden bubbles rise, a mineralised froth zone is formed that overflows as a concentrate. Although the process is more than a hundred years old, there remain many aspects that are not completely understood, particularly for the froth zone. Thus, the rules governing the design of flotation tanks tend to focus on pulp zone parameters, which are largely based on operating data. An example of this is the design and operation of impellers. These tend to be designed paying attention to hydrodynamic phenomena in the pulp zone, but their effect on the froth zone has not been completely addressed. The role of impellers in a flotation tank is to break the air bubbles in order to generate smaller ones and to provide an environment that enables the collision between those bubbles and the particles in the slurry. This usually creates turbulent regimes that can affect the pulp-froth interface, destabilising the lower regions of the froth and affecting the overall performance of the process. Different impeller designs and retrofit modifications have been proposed in the past, addressing some of those issues. However, there is no systematic study of the effect of different impeller designs on the bubble size in the pulp and its links to the stability of the froth. This work tested the impact of an impeller designs combined with the use of a stator on the performance of an 87 litres continuously operated laboratory-scale flotation tank, with a focus on bubble size in the pulp and froth stability. The results showed that the implementation of a stator system decreased bubble size and increased froth stability. That resulted in an increase of mass pull, measured as a proxy of metallurgical recovery."

Jan 1, 2018