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By J. R. Cui

The production of electric and electronic equipment (EEE) is one of the fastest growing areas. This development has resulted in an increase of waste electric and electronic equipment (WEEE). In view of the environmental problems involved in the management of WEEE, many counties and organizations have drafted national legislation to improve the reuse, recycling and other forms of recovery of such wastes so as to reduce disposal. Recycling of WEEE is an important subject not only from the point of waste treatment but also from the recovery of valuable materials. Consumer electronic equipment (brown goods), such as television sets (TV), radio sets, and video recorders, are most common. However, recent work on recycling of waste electric and electronic equipment (WEEE) primarily focused on personal computer and printed circuit boards scraps. Based on a detailed characterization study of consumer electronic scraps, recycling of TV scraps oriented to recovery of metals is highlighted by utilizing air table separation, eddy current separation, and optical (metal) sorting process. The result indicates that a high recovery of copper could be obtained by utilizing an effective gravity separation process. The separation results reveal that air table separation is an effective technology to recover metals from consumer electronic scraps. By using a DGS table, approximately 90% of non-ferrous metals were recovered in the heavy product with a purity of 40%. Printed circuit boards and cables in TV scrap cause metals loss due to the fact that metals in printed circuit boards and cables are not liberated from plastics and ceramic materials. The study shows that eddy current separation and optical (metal) sorting process provide alternatives for recovery of metals from shredded TV scraps.

Jan 1, 2014

By Scott C. Brown, Brij M. Moudgil, Ivan U. Vakarelski

The manipulation of the apparent hydrophobicity of particlute surfaces is necessary to achieve optimal selectivity in flotation processes. Previously a number of works have investigated the role of microscale surface and particulate morphologies on chemically modified substrates. These works have suggested that microscale surface asperities lead to an increase in flotation efficiency by assisting in the rupture of wetting films. Yet, in mineral processing the presence of surface asperities may lead to a reduction in flotation. The reason for this may-in part-be due to the presence of nanoscale irregularities at the interface. In this work, it is proposed that the presence of roughness at the nanoscale may have a dominant impact on the apparent hydrophobicity of mineral surfaces during flotation. It is suggested that as inter-asperity seperation distances are reduced capillary effects are enhanced for high energy mineral surfaces leading to the formation of liquid domains, which adversely impact hydrophobicity. In addition, as these distances approach the surfactant headgroup size obstruction of surfactant self-assembly process may occur, thereby further limiting flotation.

Jan 1, 2003

By Valentin V. Shatalov, Irina V. Pastukhova, Alexander V. Kurkov

"We have developed a technology to improve the quality of low-grade concentrates containing minerals of tantalum, niobium and tin on the basis of given conception by the way of improving selectivity and using certain reagents composition. The basic collector presents a traditional or complex-forming collector used together with organic diphilic reagents – the secondary reagents regarding the basic flotation regiment, capable of forming associates with the main collector on the surface of the mineral, thus altering the interaction energy. In the given process the main collector is the fraction of hydroxamic acids C7-C9, the reagent of the secondary action – sulphosuccinamate, which added in moderate concentrations range provides for a synergistic effect.We have determined the parameters of the process stability and necessary modifying reagents for a selective recovery of tantalum, niobium and tin minerals from refractory products. Variants have been studied where the main collector and the secondary action reagent were substituted with some more efficient flotation reagents. A possibility of a more flexible reagent compounding for the process has been shown. The flotation process is highly stable regards the saline composition of the liquid phase in the pulp. It can operate under conditions of the complete water recycling with the total salt content up to 12 kg/m3, iron up to 1.2 kg/m3.The given results consider the efficiency testing of the suggested technology for the gravitation products, which were obtained from ores of various genesis and contain large quantity of the most refractory minerals, such as topaz (80%), gamet (55%), tourmaline (30%). High selectivity of the process has been registered with the metal recovery about 92-98%, which appears to be similar to hydrometallurgical operations under certain conditions."

Jan 1, 2003

By M. M. Fan

In Florida?s phosphate industrial practice, the most favorable upper size limit of froth flotation is 1.18 mm which corresponds to particle weight of about 2.8 mg. Conventional froth flotation is not efficient in upgrading coarse particles (+0.425-1.18 mm). A limited number of studies have been devoted to understanding and improving coarse particle flotation. We have shown that the coarse particle flotation performance can be significantly improved by the presence of picobubbles generated by hydrodynamic cavitation. In this study, the size of picobubbles produced under certain hydrodynamic conditions was measured by a laser particle size analyzer. A size-by-size flotation performance analysis of coarse phosphate froth flotation in the presence of picobubbles is conducted in terms of flotation kinetics, selectivity and recovery. It was found that picobubbles doubled the flota-tion rate, increased the P2O5 recovery more significantly for +0.85-1.18 mm particles than +0.425- 0.6 mm and +0.60-0.85 mm particles. At a given acid insolubles (A.I.) rejection, the presence of picobubbles increased the P2O5 recovery by up to about 25%.

Jan 1, 2014

By Victor Avdokhin, Valery Morozov, Valery Stolyarov

"The adaptation-determination method provides for keeping given relationship between concentrations of ionic and molecular components of a pulp liquid and correction of parameter of the model on the basis of analysis of ore composition, technological parameters of flotation, and cost of valuable components.• optimisation program “ADDEFLOT” and combined analyzer of pulp “RA-931”An adaptation-determination method provides for two-level control of bulk and selective flotation of polymetallic ores. The lower level provides for control of reagent dosing on the base of control of ionic composition parameters in the pulp liquid phase. The control goal is to keep the basis relationship among parameters of ionic composition (ions A, B, C) in pulp liquid phase given by equations of type:• alg[A] + blg[B] + clg[C] = K (1)Values of a,b,c coefficients are uniquely determined by a physico-chemical model used. Kind of the model depends on mineral composition of an ore and reagent regime applied. As parameter of ionic composition, also values of one or two parameters (or their combinations) can be used, for instance, pH, concentration of sulfide ions, ions of collector.The upper level of control is based on calculation and use of technological results of selective flotation. At the level, an adaptation of the model (1) is conducted. A principle of the adaptation is in determining (and including in pre-setting function of the lower level) such value of K parameter, at which maximal economic effectiveness of the process is reached. As a criterion of economic effectiveness of the process, a function of losses of several valuable components, taking into account cost of the metals lost, is used. For 2-component ore, in simplified form, the function is as follows:"

Jan 1, 2003

By Peter Ay, Matthias Schmidt, Christian Stollberg

"The aim of the study is the development of a seamless reprocessing procedure for plastics from automotive parts which are to be recycled (figure 1). Before automatic sorting can be performed, the materials first have to be identified by a near and middle infrared (NIR/MIR) system.Materials reprocessing basically includes research on size reduction, decoating, and roughening of the materials. Variants of the necessary technologies such as different shredders and mills and physico-chemical or mechanical decoating and roughening procedures together with the fundamental approaches underlying these methods are investigated and benchmarked. This allows the theoretical determination of the impact of each method not only on the overall process but also on the result achieved within the identification and sorting procedures."

Jan 1, 2003

By Claudia Ríos Figueroa, Gonzalo Montes-Atenas

"Among the many variables mentioned in the literature that may influence the froth flotation performance, particle size is perhaps one of the most renowned. Empirical knowledge has indicated that recovery of fine particles will inevitably drop below certain particle size threshold. Several processing alternatives have been suggested to improve the recovery of fine particles. Some of these initiatives have been reached the status of patents and other intellectual property related documents; however, there is still a disconnection between the scientific knowledge available and the industrial operations practicalities implemented to address this matter. In fact, in general terms, none of these ideas or processes concepts have become a final solution to this problem. At first glance, economical reasons may be argued as the main cause hindering the development of these and other ideas, but it would be an oversimplification as technical issues behind them are still themes to be discussed and sorted out. This study aims to review technical aspects behind scientific ideas and processes concepts suggested to solve the problem of low beneficiation of fine particles in froth flotation. The analysis was performed using the theory of inventive problem solving (TRIZ) which allows identifying technical gaps these initiatives have not considered or overlooked. Statistically the scientific databases indicates that reports on fine particles froth flotation only represented less than 50% of all reports involving fine particles processing. Most of the solutions derived from classic contradictions derived from bubbles and particles hydrodynamics only (reducing the bubble size or increasing the turbulence would increase the rate of bubble-particle aggregates formation but may reduce the recovery). This contradiction encompasses a small range of contradictions possible to be accounted and to be resolved. The method is expected to provide insights towards designing definitive solutions for the industry in this field."

Jan 1, 2014

By Andries Van Wyk, Steven Bradshaw, Guven Akdogan, Jacques Eksteen, Cornelius Snyders, Cleophace Mpinga

"In order to exploit lower grade and complex platinum group metal resources, cheaper and more efficient alternatives to the conventional mill-float-smelt-refine route are being sought, particularly for resources’ in areas that are water-scarce and where electrification is costly and problematic. Leaching with cyanide is a promising process option and although recoveries are lower than in the conventional process routes, progress into the understanding of cyanide leaching of PGM containing ore and concentrate has been made. Research regarding the feasibility of upgrading the pregnant PGM leach solution using activated carbon has, however, been lacking and hence forms the focus of this paper. Bottle roll adsorption tests for dilute PGM solutions (0.15ppm Pt, 0.38 ppm Pd, 0.1 ppm Au) onto granular activated carbon showed high rates within the first 60 minutes (giving more than 90% recovery of precious metals). Comparison of the Pt isotherm to Au isotherms from literature indicated a similar loading capacity, while that of Pd was found to be significantly lower. The effects of solution pH, temperature, base metal concentration, free cyanide concentration, thiocyanate concentration, initial PGM concentration and activated carbon concentration were investigated and are discussed. Elution of the Pt and Pd, with the AARL elution process, was found to be effective with recoveries of 95% after 5 bed volumes of eluant at the optimum pre-treatment concentrations and a temperature of 80°C. Temperature, NaCN and NaOH pre-treatment concentration and the ionic strength of the eluant were found to be the most important factors affecting elution while base metals concentration, acid-pre-treatment, carbon loading and thiocyanate concentrations to a lesser extent. Simplified combined flow sheets are suggested and the corresponding mass balances are compared."

Jan 1, 2014

By Glaser. C., J. Balz, F. Logsch, R. Heiduschke, M. Leiker, P. Ay

The treatment of iron-hydroxide-containing water from ground water and surface water is achieved by a combination of the process steps of flocculation and subsequent mechanical dewatering. The aim is to create solid pellet structures by extending the structure forming flocculation process with a build-up pelletizing process which can be transferred directly into a drying unit. A Taylor-Couette-reactor (diameter of the inner cylinder – 40 mm, gap width – 5 mm) was used for these experimental studies. To produce the necessary flow profile the inner cylinder was rotated at a speed of 230 rpm. The iron hydroxide-containing suspension (dry matter content: 2 mass %) was added simultaneously with the addition of a cationic high-molecular flocculant in various flocculant dosages and residence times of 5 to 15 min. The pellets were examined for parameters such as geometric dimensions, dry substance content and dewatering behaviour. As the results show, there is a direct relationship between the residence time and the geometric dimensions of the pellets. After a residence time of 5 min, round pellets with an average diameter of 6 mm were formed. With an increase in the residence time up to 15 min, a compaction of the pellets could be observed, which resulted in an increase in the dry substance content of 8.0 to 11.2 mass % on average. After completion of the pelletizing process, the pellets were mechanically dewatered by filtration. By applying this innovative wet pelletizing of iron-hydroxide containing suspensions in a Taylor-Couette-reactor, it is possible to carry out the process of flocculation combined with the pellet formation with simultaneous pellet compaction in a single process step. The resulting pellet structures are distinguished from conventional floc structures by an improved water discharge capacity. After classification the pellets can be marked directly as easy-to-handle bulk material, suitable as feedstock in percolation columns for the purification of contaminated fluid streams

Jan 1, 2018

By R. Weyhe, B. Friedrich, H. Heegn

"Nickel-metal hydride batteries (Ni-MH) are storers of electrochemical energy, which have a higher specific storage capacity than lead or nickel-cadmium batteries. The demand for Nickel-metal hydride batteries is increasing rapidly since their market launch in the early 1990's. In 1999 the output of cells exceeded 80,000 tons per year (1 billion cells per year). Today there is no suitable and sustainable recycling process to recover nickel, cobalt and rare-earth metals. The discarded batteries are used in the steel industry as alloy material because they contain nickel. Cobalt and rare-earth metals are lost; they are non-recycleable.In a German governmental funded research project, IME Aachen, ACCUREC Mühlheim and UVR-FIA Freiberg are cooperating in processing as well as in creating a feasibility study. The target of this project is the development of a new recycling process for metal recovery from Ni-MH-batteries. The proposed process consists of a combination of mechanical, pyrometallurgical and hydrometallurgical processing steps.After shredding the steel shell, the various fractions of battery materials are carefully separated by mechanical processing. A hammer mill with one rotor with a perforated discharge grid of 20 mm opening, was found to be suitable for crushing the batteries to release the active mass of electrodes for metallurgical processing. The ground material is wet screened at a mesh size of 0.5 mm; thus a fine fraction is obtained with valuable components such as Ni, Co, and RE and an oversized fraction consisting of a mix of iron chips, electrodes grids, plastic chips, paper, and flocculent material of separators. The organic components are avoidable when there is a thermal step at the beginning of processing batteries.The separated fine fraction is smelted in an electric arc furnace. Any pyrometallurgical process relies on a suitable slag system. In this specific case, the process has to allow separation of nickel and cobalt as metal from the rare-earths almost quantitatively, collecting the rare-earths as well as impurities e.g. as oxides. The products are a nickel-cobalt alloy and a slag phase enriched with rare-earth oxides for further treatment to ‘mischmetal’."

Jan 1, 2003

By Gus Van Weert, Samuel A. Bolorunduro, David B. Dreisinger

"INTRODUCTIONAcid pressure oxidation of high-grade natural acanthite was investigated in the range of 110-150°C and in the sulphate media. High acidity and low pulp density were used to prevent the precipitation of silver.RESULTS AND DISCUSSIONTwo sets of acanthite specimens were obtained from La Valenciana and Ingleterra mines, Mexico. Pressure oxidation tests were conducted on 1 litre scale in a standard 2-litre Parr titanium autoclave.EFFECT OF TEMPERATURE ON THE REACTION OF ACANTHITEThe effect of temperature on the rate of oxidation is presented in Figure 1. The rate of reaction increased with increasing temperature."

Jan 1, 2003

By M. S. Eygi

This study covers the investigations based on the electrokinetic and rheological properties to explain the interactions between kaolin minerals and commercially available polyelectrolyte in anionic character. Additional adsorption test were also conducted to support the interaction mechanism. Adsorption tests showed that adsorption densities decrease by increasing the solid content. In-creasing the solids contents from 1% to 30% by weight resulted in the decrease on adsorption from 2.14 mg/g to 1.85 mg/g. Because of its difficulty, the solids ratio at 70% was not studied. However, following to trend of the curve plotted adsorption density-solid ratio, an estimation was made and adsorption density at 70% solid content was extracted from the curve as 1.75~1.80 mg/g. The electrokinetic studies pointed out that the presence of polyelectrolyte increase the zeta potential of kaolin from 40 mV to 60 mV which is reasonable conditions to disperse and stabilize the kaolin slurry and lower the viscosity. When these result of the different tests are combined and considered together, 2 mg/g polyelectrolyte concentration was noted as optimal concentration where adsorption density, viscosity and zeta potential of the slurries give maxima and remain constant after this concentration.

Jan 1, 2014

By H. Araneda

Throughout Chile?s history, mining has consistently been a leading industry in the country. The 1990s marked the beginning of a boom in Chile?s mining industry, especially in copper mining, due to both foreign and local direct investment in the sector. Mining?s contribution to the GDP was 15.6% at current prices in 2009, and it accounts for 56% of the country?s exports. Chile?s copper market share reached 35% in 2009. The investment portfolio in mining in Chile for the coming decade has been estimated at 90 billion US dollars. The acute scarcity of human resources currently experienced by the mining sector in Chile will be accentuated in the coming decade as a result of this scenario of investments. The situation is, additionally, similar to the one confronted by other countries involved in the mining industry such as Australia, South Africa, Canada, and in Latin America includes, Peru, Colombia and Brazil. A study carried out by Fundacion Chile, ¨Labor Force in the Chile Mining Industry, Diagnostic and Recommendations, 2011-2020? shows the projected labor shortage for the operation of projects in the development stage, considering only the requirements of the process of extraction, processing, and maintenance. The demand, accumulated incrementally, will be around 115,000 technically skilled workers, professionals, and qualified workers. This figure refers to the operational work force, and does not include the human resources that will be required for the prior stage of the engineering and construction of the projects (brownfield and greenfield). The demand for technically skilled workers and professions for the stages of engineering and construction of the projects that have already received investments is estimated to be 190,000 people for the period 2012-2020. The peak of the demand for engineering is 2012, with a figure that surpasses the 12,000 professionals for all of the engineering specialties. The analysis of the formation of human resources at the tertiary level (where tertiary includes technical/vocational and academic degrees at the undergraduate level) for mining and related majors demonstrates that the programs are scarce with a bias toward theoretical contents and that they are excessively long (40% longer than comparable programs in Australia, Canada, and in OECD countries). The completion rates are low, especially in the technical-vocational programs, which have a completion rate of only around 30%. Finally, the rates of attraction of technically skilled labor and professionals towards careers in mining are insufficient to reduce the identified skill gaps. In the case of university professionals such as geologists, mining engineers and engineers in metallurgy, 80-90% will work in mining. In the case of graduates of relevant majors, that cover skills also utilized by other industries, not only mining?such as maintenance workers, operators of fixed and mobile equipment, etc.?the mining sector appears to be unattractive for reasons such as shift schedules, geographical location of work sites, and other factors. On the basis of the available diagnosis a strategy for the sector has been developed (Workforce Development and Skills Strategy) whose objective is (i) to define a Mining Qualifications Framework to identify the critical roles to be filled (ii) to start, with public resources, a ¨fast-track? training program to assure the availability of at least 28,000 operators (machinery operators, truck drivers, etc.) and maintenance specialists in 2015 (iii) to promote the development of training hubs for mining with learning technologies to train technical labor and professionals on the basis of world class standards (iv) to design and implement a campaign oriented toward the perception of mining as an attractive field of employment opportunity (v) to develop curricular innovations for tertiary education programs, on the basis of international benchmarks. Keynotes: Chile, mining, copper mining, skilled human resources

Sep 1, 2012

By A. Morrison, P. Brito-Parada

"The separation of valuable and gangue minerals according to their surface hydrophobicity in a froth flotation tank occurs in both its pulp and froth phases. In the pulp phase, hydrophobic particles must be brought into contact with rising bubbles introduced at or near the bottom of the tank. In a mechanical froth flotation tank, this is primarily achieved through the agitation of the pulp by an impeller or by a rotor-stator system. However, the turbulent and mixing effects of such an impeller or rotor-stator system, necessary to promote bubble-particle interactions in the pulp, are not confined to the pulp zone, but are transmitted into the froth zone at the pulp-froth interface. This impeller-induced turbulence at the pulp-froth interface is compounded by the impulse of buoyant bubbles entering the base of the froth phase, reducing the stability, and thus separation performance, of the resulting froth. Hence, turbulence improves separation performance if it occurs deep in the pulp phase, but diminishes it if it occurs close to the pulp-froth interface. For this work, a performance-enhancing pulp phase insert was designed to isolate the impeller-induced turbulence from the pulp-froth interface in a laboratory-scale, continuously-operated froth flotation tank. The result was a shifted grade-recovery curve that allows the insert to be designed to maximize the recovery from the system without sacrificing the grade of the concentrate, or vice versa, along a spectrum of improved performance. This paper will present the insert design and development process that resulted in this improved grade-recovery curve, as well as a set of heuristics that could be used to design a similar insert for pilotand industrial-scale validation and deployment.INTRODUCTIONAn almost ubiquitous design feature of commercial flotation tanks is the enclosure of the impeller to create a concentrated turbulent zone (Mavros, 1992). These turbulent zone enclosures are varied-- from the rotor-stator design of, for instance, Outotec cells, to the air disperser design of Wemco cells-- but all share the same rationale: that turbulence is desirable to promote bubble-particle interactions (Ralston, 1999), and to produce smaller bubbles (Wills, 2006), but also undesirable because it promotes the detachment of valuable mineral particles from bubbles, and exacerbates entrainment-inducing mixing at the pulp-froth interface (Jameson, 2010)."

Jan 1, 2018

By Tohru Kamo, Shigeyuki Katano, Hideki Nakagome, Maiko Adachi, Shingo Nakamura, Kaneshi Taniguchi, Zar Zar Hlaing, Takaaki Wajima

Tantalum capacitor is a small-sized and has large capacity, and is indispensable for electric equipment. The demand increases year by year, and a quite large number of used tantalum capacitors is generated. Recovery of tantalum from tantalum condenser is recently important since production of tantalum have not been stable for the price and the quality. However, recovery of tantalum from tantalum-condenser is difficult since tantalum parts strongly cover with the flame retardant resin made of halogenated compound (mold resin). This research investigated recovery of tantalum parts from tantalum condenser using steam gasification with mixed molten carbonate. Mixed molten carbonate (Na2CO3:K2CO3:Li2CO3 = 1:1:1) (3 g) put into the reactor, and heated with electric furnace while flowing nitrogen (160 mL/min) and steam (1 mL/min) warmed by heater. After heating to setting temperature (450 - 650 oC), tantalum condenser (3 g) was put into the reactor, heated for 5-10 min, and then cooled to room temperature to recover the reacted capacitor by filtration after treating with distilled water. At relatively low temperature (550 oC) heating for 10 min, mold resin can be decomposed by using steam gasification with mixed molten carbonate, in comparison with using pyrolysis and steam gasification without carbonate, and decomposition reaction occurred over 500 oC by using steam gasification with mixed carbonate. Recovery of tantalum parts from capacitor is successful using steam gasification with mixed molten carbonate at 530 oC for 5 min, due to the effective decomposition and removal of mold resin from capacitor. Furthermore, most halogen gas generated from decomposition of mold resin can be trapped in molten carbonate not to exhaust halogen gas. These results suggested that recovery process of tantalum parts from used condenser using steam gasification with mixed molten carbonate is expected as a feasible way to recycle the rare metal in electric equipment.

Jan 1, 2014

By M. Ranjbar, M. Khosravi Rad, A. Tohry

"The filling degree is defined as the volume ratio of the load inside the mill, which determines the power drawn from the motor, as long as the filling degree is not more than the optimum level. As the filling degree increases beyond the optimum level, the impact energy inside the mill will decrease and as a consequent, the mill power output will also decrease. Therefore, the mill filling degree is a key parameter in evaluating the grinding circuit performance, as it determines the mill reaction to the input feed. Since this parameter has an impact on the mill capacity, measuring the mill load is vital for control and optimization of grinding process. As in Choghart Processing Plant no instrument is available to measure the AG mill filling degree, an empirical model based on the bearing-oil pressure is proposed. The AG mill filling degree was related to the differences between the average pressure of input and output bearings, the circulating load and power drawn. It was shown that a quadratic model could relate the mill filling to the above mentioned measurements. This model showed that when the power drawn and circulating load decreases the bearing-oil pressure needs to be checked. If the bearing-oil pressure increases the feed rate needs to be decreased and steel ball be charged to the mill to increase the grinding and prevent mill overloading. INTRODUCTION The feed quality (size and hardness) affects the grinding process in AG mills. Reducing the top feed size and increasing the ore hardness reduce the mill efficiency and increase the particles with critical dimensions inside the mill. These will result in increasing the mill filling degree and reducing the mill throughput and efficiency (Wills and Finch, 2015). The volume ratio of the load inside the mill is called filling degree, which determines the mill power drawn. It is believed that if more energy is mainly spent on grinding (Wills and Finch, 2015). Therefore the mill power draw is used as a mean to control the mill efficiency."

Jan 1, 2018

By David Newton, Christian O’Keefe, Robert Maron, Jerin Russell, Paul Rothman, Dylan Cirulis

"The presence of unwanted coarse material in flotation feed streams negatively impacts both recovery and throughput of concentrator plants. The detection of this coarse material is a long-standing problem in mineral processing that has been poorly addressed by existing instrumentation systems. This problem has been overcome by the development of two new systems that detect in real-time the presence of coarse material in the overflow stream of individual hydrocyclones. They both use sensors mounted to the overflow pipe of the hydrocyclone and provide a robust and maintenance-free system measurement that enables corrective actions through operator intervention or automatic control strategies. One system is non-invasive and detects very coarse material 6mm or greater in size. The other system uses a wetted sensor and detects coarse material down to a lower size limit of approximately 100 um. Both systems have been commercially deployed. The systems will be described in detail. Validation data and typical plant data will be shown"

Jan 1, 2014

By E. V. Bratygin, S. P. Elnikova

"In the article carrying out technique of experiments for estimation of power efficiency of process of crushing in cone crushers «in a layer». The conformity of the granulometric characteristics of the crushed products obtained as a result of the tests, the theoretical equations for the size characteristics, and the choice of the optimal equation for the prediction of the granulometric characteristics of the final products obtained by crushing ""in a layer"". Optimization of granulometric composition of power of crushers working ""in a layer"" is carried out with the purpose of reduction of the electric power consumption at reception of a product of required quality. As a result of the experiments, dependencies are obtained, the relevance and applicability of the crushing process ""in the layer"" for obtaining crushed stone of improved quality is proved. INTRODUCTION A number of equations have been proposed for calculating the breakage energy. These include equations by Kirpichev and Kick, Rittinger and Bond (Bogdanov, Olevsky, 1982). Another equation for calculating the specific breakage work in breakage by impact and in stratum was proposed by Devyatkin (Boiko, 2003). In these equations, the breakage energy is proportional to the particle size raised to some power. In the equation proposed by Devyatkin, the ore piece thickness or the feed average diameter is used. The relationship between energy and breakage can be expressed as an equation (Lynch, 1981; Tikhonov, no. 3, 2008) where k is a coefficient characterizing the energy parameter depending on the strength of the feed, l is size in microns. The Rittinger formula is obtained for n = 2, the Kirpichev-Kick formula for n = 1, the Bond formula for n = 1.5. For n = 3 or higher, the equation describes fine and ultrafine grinding. R. Hookey proposed a formula (Lynch, 1981, Tikhonov, no. 3, 2008), where the size exponent n is substituted by a size function In all of the above equations, a single value of the feed and product size is used; for example, in the Bond equation, size is defined as the particle size of the 20% oversize (P80 and F80). However, a single size value can represent multiple distributions, making that the Bond method inappropriate for determining the size (Lynch, 1981). Describing an equation for estimating the grinding energy will allow to design the electric drive and ore preparation circuit for the given breakage method."

Jan 1, 2018

By B. Mishra, Rahul Mohanty, Swati Mohanty, Swagatika Dash

Wet high intensity magnetic separators have been widely used in the mineral industry for separation of mineral particles based on magnetic properties. Usually, magnetic separators employ ordered array of grooved plates such as Lenoir and Jones plates onto which the magnetic particles get attached in the presence of a magnetic field. In the present work, we have carried out computational fluid dynamic (CFD) simulation, using Eulerian-Eulerian model to study the flow dynamics of magnetic and nonmagnetic particles within a matrix consisting of 2 mm size spheres of magnetic material, which are interconnected by wires, in the presence of a magnetic field. The three phases considered were the water, magnetic particles and non-magnetic particles. Model equations were developed considering each sphere in the matrix as a magnetic dipole, and the strength of the magnetic field at any point in the domain is due to all the dipoles. The size of the magnetic and nonmagnetic particles was 45 and 40 micron, respectively. The feed consisted of a slurry having 25 wt. % solids. The volume fraction of the magnetic particles was 0.04, and that of the non-magnetic particles was 0.045. The simulation was first carried out without the imposition of the magnetic field till a steady state was reached, and then the magnetic field was applied. The magnetic particles, as they flow down the matrix were attracted towards the region of maximum field gradient, which was in the central region of the matrix. A symmetrical pattern in the upper half as well as the lower half of the matrix was observed. As the particles moved downwards, the pattern changed, and near the outlet, most of the particles were found to flow out from the central part of the plane. This study can lead to a better design of a magnetic separator.

Jan 1, 2014

At times the phosphate industry, in Florida, encounters phosphate rock that gives lower than expected P2O5 recovery in the rougher plant section. The drop in recovery is typically 10% and as much as 30% or more. Variations in feed quality from day to day, shift to shift and even from drag-line to drag line, represent a challenge to the beneficiation plant operators and reagents? suppliers. Therefore, this characterization study has been initiated to identify the reasons for the differences in flotation behavior of such feeds. The study involves many samples to cover such variations. The characterization work includes: ? Mineralogical and chemical analysis; ? Size, shape, surface roughness and porosity analysis; ? Surface charge and surface contamination with other phases (minerals); ? Clay content and its relationship to phosphate and silica particles. The results correlated with flotation data and adsorption density measurements clearly establish the statistically significant variability in characteristic features that influence flotation response. This article discusses results from the above listed studies. On the basis of the obtained data, recommendations of practical approaches to overcome the problem of feed variability in phosphate flotation plants are delineated.

Jan 1, 2014