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By S. M. Viduka

This paper presents a numerical investigation of solid separation in jigging device, which is a gravity separation method widely used in ore processing. Separation is recognized as being heavily dependent on fluid motion in the jig. This study explores the effects of the inlet time dependent velocity profile on jigging performance. Modelling of the liquid-solid system is performed through a combination of computational fluid dynamics (CFD) to simulate liquid flow and discrete element method (DEM) to resolve particle motion. The initial packing conditions consist of a binary-density particle system of 1130 particles each 1 cm in diameter. A variety of jigging profiles are implemented in jigging. The saw tooth pulsation profile is selected with three variations in both amplitude and frequency. The performance of each profile variant is compared in terms of solid flow patterns, separation kinetics, energy, and mean particle position. These quantitative comparisons demonstrate significant differences in the segregation rate, energy, and solid phenomena, helping find an alternative optimum operating setting for the system.

Sep 1, 2012

By R. A. Kleiv, H. Havskjold, N. Church, T. Malvik, M. Tro, E. Larsen

Liberation is one of the major purposes of comminution in mineral processing. In the simplest form, two or more minerals are present in a particle and have to be reduced such that the individual particles contain only one mineral. The complexity of the mineral intergrowth varies from ore to ore. Poor magnetic separation of iron ore may have many causes. In this paper, the emphasis is given to the problem of fine magnetite inclusions in quartz or other gangue minerals. This is highlighted by two Norwegian cases: one on a magnetite ore and the other on a hematite/magnetite ore. The inclusions in question are so small that they are not liberated by reasonable grinding. In both cases, the result has been either poor recovery or lower grade concentrates than desired. The first example concerns production of direct reduction concentrates from magnetite. Magnetic inclusions in gangue particles will be magnetized enough for the particles to pass into the concentrate. The second example is given a more detailed study, where the problem is caused by silicates with small inclusions of magnetite in a combined LIMS and WHIMS separation. This study included microscopy, Davies tube testing, and magnetization measurements. In particular, large gangue particles with magnetite inclusions were shown to have a tendency to bypass the LIMS separators as drag forces in presence of hematite are large. Such particles will then be picked up by the WHIMS as their magnetization is higher than for hematite. This was demonstrated by Davies tube tests, which indicated that such particles were picked up in preference to hematite particles. However, the Davies results did not give a good quantification. Magnetization measurements of gangue particles with magnetite inclusions was shown to be a better tool to quantify the magnitude of the effect of magnetite inclusions in magnetic separation.

Jan 1, 2018

By N. D. Ilankoon

"The use of thiosulfate as an alternative lixiviant for cyanide to treat complex refractory ores followed by the use of ion exchange resins (IX resins) for gold recovery has become an industrial reality. In this study, polyethylenimine (PEI) coated iron oxide magnetic nanoparticles (MNPs) were used to recover gold from the leaching solutions that consist of calcium thiosulfate, copper and gold. The gold loaded MNPs were easily separated from the solution using an external magnetic field. Proposing a novel adsorbent with characteristically easy solid-liquid separation, to recover gold from synthetic thiosulfate leaching solutions and gold elution and reuse of MNPs were the main objectives of this study. Adsorption isotherm studies revealed that the data fitted both Langmuir and Freundlich isotherm models equally well. The maximum adsorption capacity was 18.5 mg/g at pH 8 and 50?C. According to thermodynamic studies the physisorption process was exothermic and spontaneous. Gold and copper elution, and the regeneration and reuse of the nanoparticles were investigated and promising results were obtained. Different elution systems comprising sulfites, chlorides, glycine, EDTA (ethylenediaminetetraacetic acid) and sodium hydroxide were considered. Among them, EDTA for copper elution and NaOH for gold elution were the most efficient eluants. Regeneration and reuse studies revealed that the MNPs can be used for several cycles without significant performance loss. INTRODUCTION Although cyanidation has been used for gold leaching for more than 100 years, some major drawbacks associated with cyanidation have led to a quest for alternative lixiviants for gold leaching. Cyanide is ineffective in treating carbonaceous refractory ores as gold cyanide complex is adsorbed onto the native carbon in the ore itself known as preg-robbing. On the other hand environmental concerns associated with cyanidation drives the need for environmental friendly alternatives for cyanide. As of today, thiosulfate is known to be the most extensively studied and most promising alternative lixiviant for cyanide in both technical and environmental perspectives (Aylmore and Muir 2001, Oraby 2009)."

Jan 1, 2018

By R. C. Miranda

Flotation is an operation widely used in mineral processing because of its aptitude to recover minerals of interest very efficiently. Flotation is often responsible for making possible the exploitation of mineral deposits of low concentration. In flotation various processes phenomena occur, some of which have still not been explained scientifically. Due to this fact, there are no models that can be widely applied in flotation control. Thus, in most cases, the control is done by experienced operators who are able to visually classify the types of foam into different categories and each one of them is associated with an operating actuation. In this situation, image analysis is configured as a solution that has already been employed in several ways. In this paper, a control strategy based on the colour of froth on a direct flotation of a nonferrous metal is presented. Moreover, the paper reveals the theoretical basis of the method, the critical points, difficulties and improvements that can be implemented. Data of grade were collected from the mineral of interest and RGB (red, green and blue) data of final concentrate of the froth. The mineral grade was collected and analysed during one month of operation and RGB was obtained using a camera. It was verified that the red colour showed the same trend of the grade curve in the concentrate. Thus, the use of this online data in optimising control was introduced. The laboratory grade is used to calibrate the colour set point. Therefore, it was possible to monitor in real time the trend of enrichment and depletion of a non-ferrous mineral in a flotation. It was possible to establish an online control strategy based on simple data acquisition. The result was an increase of 10% on production.

Sep 1, 2012

By T. Wajima

"A novel carbonaceous immobilizing agent for heavy metal contaminated soil was prepared from rice straw using sulfur immersion and pyrolysis, and the lead immobilization in artificial contaminated soils using sulfur-impregnated carbonaceous material was estimated. The rice straws were cut to 1 cm pieces, and then immersed in 0.1 - 1 M K2S solution for 0 - 24 h to prepare sulfur-immersed materials. The immersed-materials were heated at 400 oC for 1 h in nitrogen gas to produce the sulfur-impregnated carbonaceous material by pyrolysis. The abilities of the product to immobilize lead from aqueous solution were examined to obtain the product with high lead immobilization ability. With increasing K2S concentration, the immobilization ability of the product for lead gradually increases and then above 0.5 M K2S those are almost constant, while 15 min is sufficient for the immersed time to obtain the product with high lead immobilization ability. The product prepared from material immersed in more than 0.5 M K2S solution for less than 15 min has a maximum immobilization ability for lead ion. The lead immobilization using the sulfur-impregnated product is sustainable due to the formation of leadhillite [Pb4SO4(CO3)2(OH)2] and anglesite [PbSO4]. The product can immobilize lead ion in various artificial lead contaminated soils. By mixing artificial lead contaminated soil with the sulfur-impregnated product, the eluted solution became neutral, and the eluted concentrations of lead ion dropped below the Japanese elution standard for soil.INTRODUCTION Soil contamination with heavy metals is a worldwide problem. Accumulation of heavy metals in soils affect soil ecology, agricultural productivity, quality of agricultural products, water resources, and serious health problems for human and animal (Raicevic, et al., 2005). In the United States, for example, approximately 63 % of the sites on the National Priority List (NPL) for the treatment of contaminated soils are contaminated by metals, and lead is the most common metal, found at 15 % of the sites. In Japan, according to a report by the Ministry of Environment, 43 % of the contaminated sites that exceed the environmental quality standards are contaminated by lead compounds. Soil contamination by lead compounds is also prevalent in other developed and developing countries where lead compounds are used extensively in industrial activities without careful contamination management. Lead is a ubiquitous heavy metal pollutant in soils due to their use widely. The primary sources of Pb contamination include industrial activities such as mining, smelting of metals, and the use of Pb-containing products such as paints, lead-acid batteries, bullets, gasoline and pesticides (Cao, et al., 2009). It can damage human nervous (especially children) and reproductive systems (ATSDR, 2007). The high concentration of Pb in the soil poses risks to human and animal health by the leaching of metals from the soil into water and the consumption of edible plants growth in the contaminated soil. Therefore, proper remediation is necessary to reduce metal availability in soil for protecting human health."

Jan 1, 2018

By Garren Edwards, van der Westhuizen. Andre

"Due to the depletion of easily treated coarser ores, more mineralogically complex ores with smaller valuable mineral grain sizes are treated, the means to liberate these minerals lies in grinding finer (Partyka & Yan, 2007). Grinding to these fine sizes is energy intensive, and using standard ball mills are energy inefficient at these sizes (P80 < 75µm). Therefore, stirred mills are becoming increasingly prevalent in the mineral processing industry. In order to optimize these mills, the effects and mechanisms of the significant variables need to be understood. This paper investigates a laboratory scale vertical stirred mill (Deswik mill) in an ultra fine grinding application of a South African platinum ore. The operating variables that are considered are stirrer speed, media size, media filling, and slurry density. The resulting grinding efficiencies are considered in two ways. Firstly, a statistical model is fitted to identify the effect of the significant variables on grinding efficiency, and secondly, the grinding efficiencies are also considered in terms of a stress energy model to determine whether this can partly explain the grinding mechanism in this mill. A factorial design of experiments was used on three levels for each variable, such that only linear interactions, second order interactions and two variable interactions are included in the statistical model. The results show that tip speed, media size, percent solids and mill filling are all significant to the grind, at differing energy inputs in the grinding process. The interaction effects of these variables are also dependent on the energy inputs. The results also found that the Kwade stress energy model is applicable to this mill and can be very useful to find the most efficient operating conditions for this system. The most energy efficient operating conditions in terms of mill speed and media size were typically somewhat below the standard operating conditions and it is expected that this is most probably done in order to increase the grinding rate, but at the expense of sacrificing some grinding efficiency."

Jan 1, 2014

By N. Acarkan

Beneficiation of the pyrite concentrate of the Kastomonu-Küre (Northern Turkey) copper ore seems to be attractive due to its high Cu, Co, and Zn contents. Pyrite concentrate were used in the experimental studies. Cu, Co, and Zn were recovered from the concentrate by the sulphatizing roasting, leaching and the precipitation using H2S. Sulphatizing roasting experiments were carried out in a rotary furnace and the optimal roasting conditions were found to be at 650°C roasting temperature and 3.0 h roasting period and addition of Na2SO4 of 3 % for the concentrate containing 0.58% Cu, 0.22% Co, and 0.04% Zn. Then, the roasted product was repeatedly leached with 10 g/L H2SO4 solution. Optimal conditions were found to be 60 oC leaching temperature, 2 h leaching period, and 30% pulp density. Leaching efficiencies for Cu and Co were over 99 %. The valuable metals in the pregnant solution were selectively precipitated by H2S as sulfides. Selective precipitation of Cu, Zn, Co was achieved by adjusting the pH and the temperature of the leach solution. Final metal recoveries of 99.20% Cu, 99.40% Co, and 95.60% Zn were attained. The precipitated sulphides are marketable products. Roasting gases with their 15% SO2 content are suitable for the production of H2SO4 and the leach residues can be integrated with the iron ore processing plant as they contain 57.50 % Fe, 17.70% gangue (SiO2, CaO, etc.), 0.04% S, and 0.06% non-ferrous metals.

Jan 1, 2014

By Rong Fan, Roger Smart, Ning Xu

As part of an Australian Research Council project with Newmont and Newcrest mining companies studying the influence of clay minerals on rheology, hydrodynamics and flotation response, the cryo-SEM technique has been used to capture and image the clay (low crystallinity kaolinite Q38) aggregate structures in the flotation pulp immediately after collector and before frother addition. Samples were also collected from the earliest froth phase and the froth overflow corresponding to early and later concentrates. In this technique, a copper tube is filled with the sample during operation of the cell. The tube is immediately plunged into liquid nitrogen vitrifying the water phase before it can crystallise as ice thereby retaining the structures without volume or other physical change. After sublimation of the vitrified water surface, the aggregate structures are revealed and can be compared between pulp and froth phases from clays in different feeds and flotation conditions. The images from both low-clay ore and ore with clay content reveal various levels of aggregation as predominantly edge-edge connected aggregates similar to those found in our previous studies of high-clay tailings. For the samples from the ore with clay content, more extensive edge-edge clay strings are found in the early froth phase as compared to exiting froth overflow and the pulp phase with short edge-edge connected strings. It is suggested that the strings of clay particles result from edge-edge aggregation in the Plateau borders of the bubbles before breakage during sampling and the more extensive edge-edge aggregation in early froth phase is induced by crowding in the bubble borders. The clay strings collected into the overflow concentrate are almost all broken up compared with the Froth before drop-back. The implications for entrainment and entrapment mechanisms of gangue capture in froth will be discussed.

Jan 1, 2014

By Katarina Theander, Robert J. Pugh

The generation of froth with a critical degree of stability and height is an important aspect of the froth flotation. In this paper we have studied the synergism and anti-synergism in frothing behaviour in a mixed flotation collector/frother mixture (a model fatty acid; sodium oleate and a model frother; nonionic (polyethyleneoxide alkyl C14E6). Values of the collector / frother molecular interaction parameters (the ß-parameters) were determined from the surface tension data using regular solution theory. The frothing characteristics of the system were evaluated using a glass column equipped with a series of conductivity electrodes, which enabled the water content of the froth to be determined. From these measurements, the dynamic frothability and static froth stability were determined. It was concluded that the synergism/anti-synergism in frothability was depended on the molecular composition of the surfactant system, the diffusion of monomer to the thin film interface and on the breakdown of the mixed nonionic/anionic micelles.

Jan 1, 2003

By Lei Wang, Qi Zheng, Xiao-kui Che

"The wastewater emitted by gold chemical industry contained vast of different heavy metal ion, such as Zn, Cu and Ni etc. Among them Zn is the main ion in the waste water which causes the serious environment pollution. A method of preparing a kind of resin which is used for the removal of Zn by magnetic adsorbent was developed and was applied in practice. This adsorbent is a chitosan made of a kind of Fe3O4-chitosan modified by epichlorohydrin. The adsorption capacity of the absorbent and it was concluded that under the laboratory conditions, the maximum adsorbing capacity of this adsorbent could be 287.58 mg/g. The absorbent was also applied in the wastewater emitted by a gold industry in Shandong province. Its performance was tested and the result showed that the concentration of Zn ion in the wastewater was reduced from 0.58 mg/L to 0.0174 mg/L. What is more, the adsorption rate could be more than 97% when the dosage was 100L/m3 after adsorbing for 1h. KEYWORDS Selective, preparation, laboratory experiments, industry experiment, comparation INTRODUCTION Currently, most gold chemistry use cyanide to leach gold ore. Many different metals participate to this reaction besides the gold ion in this processing, so that the composition of the water is very complex. The waste water emitted by gold chemistry industry contains large amount of heavy metals. Definitely, if it was discharged without any treatment, the water would threaten the environment. The recuperation of any ion in the water would mitigate the pollution. Ion exchange resin, which is an effective material to do the water treatment with low cost, became widely applicated in this field [Yu-jiao Wang,2013]. Different kinds of resin were developed and the influence factors such as pH, adsorption properties and selectivity for different ions were investigated [CA Cruz et al,2018; PawanKumar et al.2016; Y Zhang, et al,2010; and ShengingSun, Aiqin Wang, 2006;]. The waste water mentioned in this article has a high Zn concentration, so a magic resin for Zn adsorption selectively we designed was used to manage this water. And the recovery of Zn could not only contribute to pollution abatement but also a best way to settle a dispute to the short of Zn resource. So the article mainly describes the preparation and the application of a kind of magnetic adsorbent used for the removal of Zn both in laboratory and industry. The aim of this article is to compare the effect of this resin in industry and laboratory?"

Jan 1, 2018

By Paul W. Weiblen, Louis J. Cabri, Rolando Lastra

"Preliminary tests were done to determine whether comminution by electric-pulse disaggregation, or E-PD (cf. Rudashevsky et al; 1995), was more effective than using conventional crushing for Merensky Reef ore. A hand sample of the Merensky Reef was sawn in two: then one sub-sample was comminuted to .2 mm using E-PD at the University of Minnesota, and the other sub-sample was crushed to .2 mm using a conventional jaw crusher at CANMET.The products of the electric-pulse disaggregation and jaw crusher were fractionated by sieving and by a separation using a heavy liquid with a specific gravity of 3.3, because the proportion of platinum-group minerals (PGM) and sulphides to silicate minerals is very low. Thus, four mineral separates were produced: .2000 + 833 µm, -833 +208 µm, -208-µm float and -208-µm sink. All the mineral separates were studied by image analysis (Lastra et al; 1998). The main objective was to determine the liberation of gangue (silicate minerals), chromite, pyrrhotite, chalcopyrite, pentlandite and PGM. In the case of the PGM, a specific image analysis program was written to search and measure these minerals.The results show that the liberation obtained for gangue was similar (~99%) using either method of comminution. However, the liberation obtained for chromite (~89% vs. ~38%), pentlandite (~50% vs. 1%), pyrrhotite (~56% vs. ~38%), and PGM (~56% vs. ~1%) by E-PD was higher than that obtained by conventional jaw crusher, whereas the liberation obtained for chalcopyrite (~20% vs. ~71%) by E-PD was lower. Nevertheless, the image analysis of the products also showed that the PGM are strongly associated with pentlandite. Thus, for the Merensky Reef, liberation of pentlandite from the gangue minerals and chromite is important to recover more of the PGM. This maybe be significant because, in addition to increased recovery of platinum-group minerals (PGM), Merensky Reef pentlandite also contains significant quantities of valuable platinum-group elements like Pd and Rh (Cabri, 1981; Cabri 1988, Kinloch 1982, Peyerl 1983). Hence, the results indicate that for the Merensky Reef, electric-pulse disaggregation would represent a better comminution operation than a conventional jaw crusher would. In addition, the greatly improved liberation for chromite may find application for the PGM-rich UG2 chromitite."

Jan 1, 2003

Froth flotation is an industrial process commonly used for the separation of mineral particles. Bubbles sparged in a pulp collect and carry hydrophobic particles to the top layer of a flotation cell, the froth zone. There is a strong correlation between the stability of the froth phase and the flux of solids. However, flotation units placed in series operate, as a whole, in a non-steady state regime with the concentration of particle decreasing from one cell to the next resulting in a decrease in froth stability, which can compromise the recovery of valuables. Organic chemical reagents, frothers, are generally added to prevent fine bubbles from coalescing and to increase the stability of the froth phase. Frothers represent the second largest group of mining chemicals. It is crucial to understand the resulting properties of the frother on the froth phase in order to select the most suitable reagent for a particular operation. The bubble coalescence dynamic of three different surfactants, 1-pentanol, poly (propylene glycol), and tri (propylene glycol) methyl ether, were investigated in this study. In the first stage, the stabilisation mechanism of bubbles in a solution of surfactant was investigated using a specifically designed experimental setup. The coalescence behaviour of bubble pairs was recorded using high-speed video imaging in which information such as the coalescence time and the deformation of the resultant bubble upon coalescence could be extracted. The results were then compared between the different surfactants for several concentrations. It is shown in a study that the coalescence time increases with surfactant concentration until the Gibbs-Marangoni effect is suppressed by bulk diffusion. Conversely, the oscillation of the resultant bubble was found to be affected only at concentrations at which the film is saturated. The implications of the effects of surfactant type and concentration on the coalescence time and bubble oscillation in froth flotation are discussed. Keywords: froth flotation, frother, bubble coalescence

Sep 1, 2012

By M. McClintock

"High Pressure Grinding Rolls (HPGR) is increasingly being chosen for comminution circuits for its energy-efficiency for hard rock mining operations. Despite HPGR’s growing popularity, geo-metallurgy programs are still prohibitively expensive because of large sample requirements. Traditionally, sizing HPGR application requires a significant amount of sample, in the order of 1 to 10 tonnes, depending on the level of study and complexity of the resource. Therefore, engineering and design of HPGR circuits typically are reliant on few composites that are required to be representative of the resource and mine plan. Three bench scale HPGR test methodologies were developed in 2015 at NBK Institute of Mining Engineering at the University of British Columbia (UBC) capable of defining the energy size breakage relationship of pilot HPGR. These methodologies were developed to allow bench scale testing for different levels of study from PEA (Preliminary Economic Assessment) to detailed design and operations. The Piston Press test defines the energy size reduction relationship by measuring specific energy consumption and corresponding feed and product size distributions. The advantage of Piston Press testing is the small sample requirement of 5 to 10 kg. Small sample requirements allow multiple samples to be tested across a deposit. Piston Press testing allows extensive geo-metallurgy programs that can determine ore variability and inform in optimization and production planning. To date, the Piston Press methodologies have been validated on a pilot-scale HPGR unit located at UBC. Recently, testing was conducted to calibrate and validate the Piston Press test against full-scale HPGR on a gold sulphide ore deposit. The program included the collection of operational data with the respective HPGR feed and recycle sample. Sample collected was used both for Piston Press testing and HPGR piloting. This paper discusses the test-work and results as carried out during this program, using the aforementioned methodologies."

Jan 1, 2018

By Roberto Galery, Priscila Esteves, Braz Cardoso, Marcelo Stopa

"It was developed in this work a computational tool to aid in anomaly detection present in the operation of ball mills. The tool uses a torque estimator that is based on measurements taken exclusively in the drive motor. The ball mill equipment widely used in the mining industry has, inherent to its principle of operation, high energy consumption and low efficiency. These characteristics are accentuated when the mill operates outside the ideal conditions of velocity and loading. Direct measurement of these variables is extremely difficult because it requires the installation of sensors in moving parts of the mill. Thus, systems that can help monitoring the operating conditions and predict anomalies are useful because they contribute to improving the performance of the process, help to reduce the energetic consumption, wear on the mill surface and frequency of maintenance shutdowns. The detection strategy implemented in this work is based on the fact that operational anomalies such as an inadequate percentage of balls and incorrect angular velocity manifest itself as a change in spectral components of the torque signal in the mill driven by an electric motor. The mill torque was estimated by processing motor variables measured by sensors commonly used for control purpose and installed exclusively in the motor. The mill was operated at various fault operating conditions and signals from electric motor and vibration on the mill shaft were measured. The spectral components present in the estimated torque signal were then compared with signals from a vibration sensor in order to establishing a correlation with anomalous operation condition of the mill. The experimental results showed that the signals obtained has an excellent correlation with other variables obtained by direct measurement and have potential to be used to construct a system for automatic fault detection in the operation of ball mills."

Jan 1, 2014

By G. Aguilera

The mineral suspensions do not present a newtonian behavior as their continuous phase; they can be pseudoplastic, dilatant, or both. The viscosity becomes as the most important rheological variable because the different industrial processes involve a wide variety of rheological scenes, with a specific rheological behavior for each one. Some authors have tried to model the viscosity of suspensions considering the volumetric fraction of solids and others have also kept in mind the size of the particles (Einstein, 1906; Batchelor, 1977; Jinescu, 1974; Krieger and Dougherty, 1959; Tangsathitkulchai and Austin, 1988). Others consider the shear rate (Cross, 1965; Hershel-Bulckley, 1926; Bingham, 1916, etc). However, none of the models is able to simulate the viscosity involving the physical, chemical and mechanic factors at the same time for crowded suspensions. A new model based on Neural Networks is presented, taking into account all the variables of ceramic clay suspensions and chemical additives. Keywords: viscosity, clay minerals, neural networks, simulation, mathematical function

Sep 1, 2012

By L. W. Luo

Zeolite in some regions or countries of the world have been the subjects of materials for environmental remediation involving the use of removal to heavy metal ions and some organic pollutant as a sorbent because of its capacious ions exchange and huge surface area. This article addresses the equilibrium and kinetics for manganese adsorption using zeolite modified by hexadecyl trimethyl ammonium bromide (HTMAB) as a sorbent material over a range of pH between 3.4~7.2 with eight different Mn(?) solution concentrations. PHzpc (pH of zero point charge) of the sorbent was examined according to the method proposed by Tripathy and Kanungo, and a value of 6.91 was obtained. The experimental data fit langmuir?s model for the majority of pH and Mn(?) solution concentrations tested (0.92<R2<0.97). The maximal adsorption capacity, qm ascending with pH between 3.4~7.2, rise from 15.01mg?g-1 at 3.4 to 19.46 mg?g-1 at 7.2. Besides, the constant of Freundlich Kf have the same trend with qm, increases with pH ascending. And the sorption intensity, represented by parameter 1/n in Freundlich?s model, is favorable in entire range of metal ions concentration studied. Finally, kinetics data accurately fit to pseudo-second order which indicate that there must be sorption of Mn(?) behavior occurring on inner-sphere of the sorbent.

Jan 1, 2014

In looking to the future of mineral processing the focus is typically on improved processing units. Basically it is a search for an elusive wonder machine that could revolutionise the economy of mining: the sorter that strips 50% of the ore with only a few % loss of value; the comminution device that uses 5% of the energy while producing fully liberated particles; or the recovery device capable of producing a 99% recovery at 99% grade. These aspirations are propounded against a reality backdrop of sorters rusting in back yards, mill throughputs below design and varying by 30%, cyclones flaring and cut-sizes fluctuating, mediocre recoveries and soaring processing costs. This disconnect between aspiration and reality appears, to these authors at least, to be a mighty chasm. Moreover, it remains one over which we are expected to magically leap rather than methodically bridge. Indeed one may be forgiven for thinking that should such a wonder machine come along, taking advantage of it would be highly improbable. Questions would inevitably emerge on how to feed the correct material, how to cope with the wide variability of feeds, how to control such advanced equipment and how to handle the new product from such a machine. It is likely these questions might lie unanswered, or more regrettably, unasked. It is generally accepted that as an industry we are exceedingly unlikely to teleport from the current status quo to an entirely new reality in a single flash. It is our thesis that the probability of these magical machines materialising is remote, and even if they miraculously appeared, we simply wouldn?t know what to do with them. Rather, it is our contention, that a step change will only arise through a staircase rather than from a single giant leap. We should focus on building those steps and linking them together into a firm structure ? a workable mineral processing circuit. This paper addresses the alternative of a coherent set of modest but significant improvements, integrated to produce the step change we desire: essentially, a reduction of processing energy to below 40%, which we believe is achievable without recourse to any mystical machines. A key underlying capability to designing these dramatically improved processes, is the weaving of independent process models into a coherent circuit simulation, in order to design the new generation of mineral processing circuits. Keywords: step change, circuit design, circuit simulation, energy reduction

Sep 1, 2012

In this paper, the recovery of copper minerals and molybdenite in the rougher/scavenger banks of two separate mineral processing plants is compared with recovery in laboratory (batch) cells. A number of metallurgical surveys were conducted in two plants treating porphyry copper and molyb-denum ore. Batch flotation tests were performed on plant conditioned flotation feed slurry, in parallel with the plant metallurgical surveys. The effect of flotation feed density on recovery of copper minerals and molybdenite in the plant and batch laboratory cells was investigated. Changes in flotation pulp density had little effect on copper mineral recovery, in both plant and laboratory cells. The ultimate recovery for molybdenite, on the contrary, increased considerably when the pulp density was reduced, both at plant and laboratory scale. Recovery of copper minerals in the plant and laboratory cells was comparable, while molybdenite recovery in laboratory flotation cells was 3%~13% higher than in plant. It is hypothesised that the flotation rate of molybdenite is sensitive to cell hydrodynamic conditions (i.e. local turbulent energy dissipation) more than the flotation rate of copper. The flotation behaviour of molybdenite particles is likely to be predominantly controlled by bubble-particle collision frequency, which is enhanced in high local turbulent energy dissipation environment. For chalcopyrite, the flotation recovery is mostly determined by attachment and stability efficiencies. An increase in local turbulent energy dissipation, while increasing collision efficiency, may negatively impact on attachment and stability efficiencies. The outcomes may have a considerable impact on increasing molybdenite recovery from porphyry ores.

Jan 1, 2014

New technology for on-line particle size analysis of mineral slurries has opened up new applications for particle size measurement. In some cases the particle size distribution of the final concentrate is an important quality issue. This paper discusses established on-line particle size analysis technologies and presents experiences on the use of a new technique employing laser diffraction in several minerals processing operations. The main innovations in the new instrument are a simple dilution system and multiple scattering correction algorithm, which allows wide solids content variations of diluted sample in the measurement cell. Representative sample for laser measurement is produced by a simple and reliable dilution system. The applications discussed are; Blaine number measurement of Fe concentrate before pelletizing, grinding of variable batches of ore and paste thickener control.

Jan 1, 2014

By N. Pajunen

The basic objectives of current EU waste policy are to prevent waste and promote re-use, recycling and recovery to reduce negative environmental impact (2008/98/EC). In this paper, we focus on drivers and barriers for sustainable development by decreasing amount of waste and increasing material efficiency. Main target is to understand what are the most efficient drivers for environmental friendly decision making for reasonable consumption and use of raw materials. Environmental control instruments usually mean those actions the regulatory authority uses to control and limit environmentally harmful behavior of companies. A major change in the environmental control system took place in the 1980s with the focus moving from specific environmental issues to the environment as a whole. The environmental control system i.e. the legal (administrative), economic and informative instruments focuses on prevention. Before and still, the legislation is one of the main drivers in improving material efficiency. In this paper, we focus on drivers and barriers for effective industrial material use, and mainly on drivers. The objective of this study is to analyze how the drivers are working and are there any possibilities to influence on those. Our aim is also to introduce few examples of the existing supply chains and the drivers for better environmental performance and material efficiency. These examples are also compared with ideal reference scenarios. Our main research question in this article is: ?Are the financial issues the most important driver for environmental friendly strategic decisions?? In addition, retell the story from another perspective: ?The most important barrier for environmental friendly innovations seem to be the investment cost, the high risk involved in committing capital to unproven technology.? Other drivers, like the corporate social responsibility, stakeholder pressure, and general public pressure, will also affect the final decision. This article is based on research projects and literature. Keywords: drivers, decision-making, environmental management, saving primary raw material, material efficiency, sustainable production, critical raw materials

Sep 1, 2012