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By I. Baltov

The Chelopech Mine, located in Central Bulgaria, is one of Europe?s largest underground copper- gold mines, currently mines and processes approximately one million tonnes of ore per year. Copper concentrates containing gold and silver with significant arsenic content are produced and sold on the world markets. The operation was acquired by Dundee Precious Metals in 2003. A modernization program for the Mine and Plant has since been in progress to increase both production and mechanical reliability, and also to optimize metallurgical recoveries. Since then, mine output and plant throughput have doubled, plant availabilities and utilization have increased significantly, and overall metallurgical performance for copper and gold improved. The paper presents the systematic approach for obtaining and analyzing data, communicating it, and making suggestions for changes to the technological parameters and flowsheet in order to maximize metal recoveries. These studies have correlated the ore characteristics (particle size distributions, metal assays, and Cu and Au mineralogical and phase analyses) with the actual plant performance (kinetics, recoveries, and throughput). Cu recovery by size has been calculated from the mineralogical analyses of feed, concentrate and tails, with the most significant losses being identified in terms of fraction and phase recoveries. This has provided the recommendations (some of them tested in plant) for changes in the grinding and flotation circuits.

Jan 1, 2014

By S. Mohanta

In composite washeries optimization of operating parameters to achieve maximum clean coal yield at the desired clean coal ash level is a major problem. This problem is more acute in countries like India, which have predominant reserves of difficult-to-wash coals. The constrained operational parameters of washing for some equipments make it more severe. In addition to this, the dependence of separating performance of different equipments upon various variables aggravates the situation. Here an attempt is made to find a numerical solution to get maximum yield and minimize the difference between the actual and the theoretical yield. The solution is arrived through constrained non-linear optimization of a multivariable objective function that utilizes spreadsheet tools; the method accommodates any number of source coals or washing size fractions. By using a designed Ep value the predicted yield of composite clean coal has been calculated and the yield is optimized subject to constraints on both the ash and specific gravity. It is shown that operational constraints of different washeries in the composite plant that utilizes gravity separation methods can also be over-come. The technique offers the coal preparation engineer an effective and straightforward method for determining the optimum cut-points of separation for different coals or blended coals to obtain maximum product yield at a specified level of ash content.

Jan 1, 2014

By C. Igathinathane

Coal is the most widely used fossil fuel in the world, providing more than 25% of world?s electrical power. Since, the behavior of coal particles in crushing and grinding circuits, concentration operations, and solid-liquid separations is strongly dependent on size, a reliable and accurate measurement of particle size and particle size distribution (PSD) is a vital aspect in coal cleaning. This paper presents a method for the characterization of ground coal particles using image analysis. We utilized a machine vision (MV) approach that used a document scanner as the imaging device and a user-coded ImageJ plug-in that processed the image and automated the PSD analysis and output results in textual and graphical forms. This approach used a sum of volumes (SVolume) as weighting factor for particle length as the primary dimension of analysis and was successfully applied to ground coal. The plug-in was further improved for computational performance in this study. Mechanical sieving (MS) was also used to compare the MV results. MV results showed that the PSD of ground coal followed a uni-modal normal distribution, and the log-normal plot against particle size exhibited a linear trend for most of the range. MS results, however, had three linear segments, when the width-based sieving results were transformed to lengths by applying the shape factor (width/length), but a definite deviation between the PSD plots was observed. This study demonstrates successful application of the MV SVolume approach for PSD analysis of ground coal, which can be extended to similar particulate minerals and products. Keywords: dimension, fiji, image j, image analysis, coal, particle size, plug-in

Sep 1, 2012

By Gautam Chandra Mondal

An attempt has been made to carry out qualitative assessment of mine water discharges from the different mines of West Bokaro Coalfields of Hazaribag district of Jharkhand, India. A total of 33 mine water samples were analyzed for pH, electrical conductivity (EC), major cations (Ca, Mg, Na, K), major anions (HCO3, SO4, Cl, NO3), and heavy metals (Fe, Mn, Cu, Zn, Pb, Cr, Ni, Co, As). The hydrochemical data has been evaluated in terms of major ion chemistry, solute acquisition processes and suitability of mine water for domestic, industrial and irrigation uses. The pH of the analyzed mine waters varies from 5.27?8.43 indicating acidic to alkaline nature of the water. The electrical conductivity (EC) values varied from 276 µScm-1 to 1598 µScm-1 for measured samples and spatial differences between the EC values reflects the wide variation in lithology, surface activities and hydrological regime prevailing in the region. The anion chemistry of the analyzed water samples shows the dominance of SO4 and HCO3 with a minor contribution from Cl, NO3 and F. The observed high values of sulphate in the mine water of the area may be attributed to the oxidative weathering of pyrites. On average chloride is contributing 5% of the total anionic balance (TZ-). Fluoride and nitrate have low concentrations and on average contributing <2% the total anions. The cation chemistry indicates that 79% of the samples are Ca>Mg>Na>K, while the 6% belong to Ca>Na>Mg>K and 1% of Ca>Mg>K>Na. Weathering of rock forming minerals and cation exchange processes normally control the levels of these cations. Concentrations of some heavy metals (Fe, Mn, Ni, Cr) are found to be well above the prescribed permissible levels recommended for the drinking water. The water quality assessment for drinking purposes indicates that most of the mine water having high TDS, total hardness (TH) and sulphate concentrations. This suggests that mine water of the study area is not suitable for direct use in drinking and domestic purposes and needs a proper treatment before its utilization. The assessment of water for irrigation uses show that the water is good to permissible quality and can be used for irrigation uses. However, high values of salinity, %Na, SAR, RSC and Mg-hazard at certain sites restrict its suitability for agriculture uses. Keywords: mine water; ion chemistry; quality assessment; West Bokaro coalfields

Sep 1, 2012

By M. P. Krasteva

The froth flotation process for separation of mineral ores depends on the establishment of care-fully controlled froth. The formation of very stable froth in the flotation circuit is a problem that may occur in many plants, resulting in down-time, low quality and grade of final product and considerable expenses. Froths build up on the top surfaces of thickeners, tanks and flotation cells until they overflow, or until the efficiency of the circuit is impaired. A similar problem exists in Assarel concentrator, Assarel-Medet PLC, Bulgaria. Copper and copper-pyrite ores are dressed in Assarel concentrator. They are characterized with variable and complex mineral and physical composition. During the flotation cycle, resilient and difficult to break-down froth is formed, which subsequently impedes the process of thickening and clear overflow obtaining. Due to this problem continuous sampling in the cycle of thickening was conducted. The mineralogical, chemical composition, particle size distribution and solid phase content of the products were determined. It was established that the solid phase of the froth build up on the top surface of the thickener differs considerably from this one of the thickener underflow. The data clearly indicates that a separation process takes place on the top surface of the thickener ? fine particles of chalcopyrite are concentrated in the froth. The role of chemical reagent addition in the break-down of the flotation froth is investigated in terms of surface chemical phenomena involved in the stabilized froths. Measurements of the coper minerals wettability and surface tension at the air/liquid interface were performed. The surface active agent AERODRI® dewatering aids were laboratory tested. Bench-scale froth collapse tests were conducted. Reagent addition into pulp-froth system promotes and leads to a bubble coalescence, an improvement of the wetting of the mineral particles and a decrease of the surface tension at the air/liquid interface. The results of the laboratory experiments showed that the presence of the surface active agent leads to considerably decrease of the froth stability and the destruction of the deleterious froths build up on the top surface of the thickeners in Assarel concentrator.

Jan 1, 2014

By K. B. Venkatesh

In view of the importance of size reduction operations from the energy consumption point of view, during the past one hundred and fifty years a number of attempts have been made to develop a general energy-size relationship. However, to date it has not been possible to clearly define the scope of application of various laws proposed, though Bond law has been widely used with a moderate degree of success. It was, therefore, decided to carry out a thorough analysis of the batch ball mill grinding data available in the literature on several minerals that were ground under normal range of operating conditions. In particular, relationships proposed by Bond, Kapur, Voller and Morrell were examined in detail. It was found that the relationship proposed by Kapur in terms of the mean particle size provided a more accurate basis for estimation of energy. The value of the exponent of mean particle size in this relationship, a, is same as the exponent of the particle size in the expression for the grinding rate parameter: ki = Axia, provided the particle size distribution range corresponds to the self-similar or self-preserving regime. In this regime, mean particle size is proportional to the 80 percent passing size and size modulus. From the practical application point of view, it was possible to describe the variation of µ1 over limited, but significantly broad size range, using a constant value of a. Thus, by carrying out a few batches, grinding experiments over the size distribution range corresponding to the contents of the production mill, the applicable value of a can be determined. Keywords: energy-size relationship, ball mill, mean particle size, self-similar size distribution regime

Sep 1, 2012

By Chenyang Zhang, Zhigang Yin, Jianyong He, Yuehua Hu

"A lot of floatation reagents (collectors, inhibitors and regulators) for the beneficiation of copper ores have been well developed in the past century. However, it is still unclear about the micro interaction mechanism of these flotation reagents with copper ores. In this paper, the interaction mechanism of these flotation reagents with the copper atom on chalcopyrite has been systematically investigated by first principle DFT (density functional theory) calculations. Thirty-four specific common functional groups linked with the same hydrocarbon chain (ethyl) are optimized at a B3LYP/def2-TZVP level, the solvation effect was included with the SMD solvation model. The analysis of the highest occupied molecular orbital (HOMO), the lowest unoccupied molecular orbital (LUMO) and nature bond orbital (NBO) charge of these reagents reveals their potential applications to other types of copper-bearing mineral. Further investigation of the thermodynamics calculations gives more reliable data to screen collectors or inhibitors for copper-bearing mineral. The flotation results from carefully reviewed literatures are in good agreement with the calculation results. This work might also shed new light on the development and discovery of highly efficient and selective flotation reagents with low cost based on the computational methods.INTRODUCTION Froth flotation,(Shean & Cilliers, 2011) a mineral processing approach, is applied to efficiently enrich valuable minerals from the mixture, which is achieved according to the dictinctive surface properties of minerals. In the past century, researchers have develped an aboundant of flotation reagents by extraction or synthetize, and many carefully selected reagents might die in the bench tests or the pilot tests before the pratice.(Bulatovic & SrdjanM, 2007) Generally, it involves a lot of cost and tedious works by conducting flotation tests to screen flotation reagents. Flotation reagents have been boomed robustly with the developing of the organic synthesis.(Liu, Yang, & Zhong, 2017) Reseachers found the specific properties of a reagent are determined by its functional groups and the length of the hydrocarbon, where the functional group is assigned as the adsorption site to adsorb onto mineral surfaces and the hydrocarbon chain is called as a hydrophobic group."

Jan 1, 2018

By E. V. Konoplev

Russia is one of the largest manufacturers of potash fertilizers in the world. Processing of potash ores basically is carried out by a flotation way. Potash ores of the Verhnekamsky potash deposit contain sylvite (KCl), halite (NaCl) and water insoluble impurity (up to 8 %), presented silicate- carbonate minerals, easily slimed by ore crushing in rod mills. Ore of some deposit sites, developed by ?Uralkali? Co, contains a significant amount of a carnal-lite (KCl.MgCl2.6H2O). Work practice of flotation potash plants has shown, that increase of car-nallite content in ore leads to increase magnesium ion content in a circulated plant brine (saturated salt solution of potassium and sodium chlorides-sylvite brine) and to deterioration of indicators of ore processing. In the Paper we present results of researches of floatability of various size sylvite and influences silicate-carbonate slimes on sylvite flotation in brines with the various magnesium chloride content. It is established, that with increase magnesium chloride content in the brine mainly decreases the flotation of coarse sylvite and amplifies adverse effect of silicate-carbonate slimes on sylvite flotation. In this connection deterioration of potash ore flotation is caused not only decrease sylvite floatability but also strengthening adverse action of water insoluble impurity on potash flotation. It is shown that the application of frothing agents, which render the stronger dispersive action on the colloidal-micellar structures of amine in the salt solution increases the absorption of collector on the sylvite and improves the flotation of sylvite into magnesium the containing salt solutions. The application of an organic depressor to the greatest degree of decreasing the absorption amine on the slimes and to the smallest degree possessing anionic properties proves to be most effective with the flotation carnallite of the containing potassium ores. It is offered the application the frother on a basis of glycol ethers and organic depressor on a basis of urea-formaldehyde resin. Results of industrial tests developed reagent modes for flotation treatment of ores with the raised carnallite content (to 6 %) on ?Uralkali? Co plant have shown that their application has allowed to receive equivalent indicators potash flotations at change of magnesium chloride content in the brine from 0.7 % up to 2.4 % .

Jan 1, 2014

By A. Chattopadhyay

Porphyry copper deposits are the most important source of copper and also gold within the orogenic belts. These deposits are characterized by low grade copper ore (0.2% to 1% copper) and host precious metals like gold, silver and platinum. A characterization tool has been developed for complex porphyry type copper-gold deposits with an aim to quantify copper and precious metal deportment. This quantification is a challenging task due to low grades and also due to the presence of both visible and invisible precious metal content in different sulphide and non-sulphide phases. Studies were initiated on various complex, ore deposits and also on samples representing various processing streams such as flotation and leach products. This paper presents the development of a systematic approach to diagnostic metallurgy using state-of-the-art optical and automated mineralogy, micro-probe, dynamic SIMS and TOF-SIMS analysis for quantification of invisible and visible precious metals content in various species. The relevance of this characterization to metallurgy will also be briefly discussed in this paper.

Sep 1, 2012

By Sravya Kosaraju, Christian Ekberg, Stefan Allard

Li-ion batteries are now used in electric vehicles (EVs), plug-in hybrid vehicles (PHEVs) and, hybrid electric vehicles (HEVs). Nanostructured Li(NiyMnzCo1-y-z)O2 is one of the more popular cathode chemistries for automotive Li-ion battery, due to its enhanced properties such as large surface area, short diffusion length, enhanced ionic and electronic conductivity, improved mechanical strength and structural integrity [Pan et al, 2013]. Recycling of Li-ion batteries helps to mitigate environmental effects of virgin metal extractions along with improper disposal of end of life batteries. To fulfill these objectives of the recycling, recovery of pure streams of the involved metals should be considered. In this study, the batteries were first discharged and dismantled in an inert atmosphere (Ar). The electrodes were then heat treated in a box furnace. This was done in order to break the chains of the adhesive (PVDF) and consequently separate the metallic substrates Cu and Al from the electrochemically active compound. This heat-treatment also helped to simplify the dissolution of the metal constituents in the electrochemically active compound from the cathode in the acid leaching process. Solvent extraction was chosen to achieve separation and recovery of metals with higher purity from these leachates. In the scope of the present work, a complete process from the point of dismantling to separation of constituent metals using solvent extraction was studied.

Jan 1, 2014

By S. Titkov

At present, Russia is engaged in processing, 3new plants of hard-to-process potash ores with increased content (up to 10 - 12%) of insoluble impurities (insoluble residue ? I.R.). This required additional research to improve the process of potash ores flotation. Based on the study of the effect of dispersive properties of frother and its flow rate on the efficiency of aliphatic amines with different length of the hydrocarbon radical (as sylvite collector) there was showed the possibility to apply high molecular amine with length of hydrocarbon radical C20 ? C26 by normal temperature of circulated plant salt solution (saturated solution KCl ? NaCl ? H2O). There was designed and tested in plant conditions the modified amine collector with the length of the hydrocarbon radical C16 - C26, improving flotation of Sylvite under normal temperature of circulating salt solutions at potash flotation plants. There was made the study of the influence of the hydrocarbon radical length of alkylmorpholine on the Halite flotation from intermediate products of sylvite recleaner flotation with different content of I.R. (silicate-carbonate slimes), at normal and elevated temperature of salt solution. On the basis of the application of modified alkylmorpholine for Halite flotation, there was developed the process of further beneficiation for the intermediate products of sylvite recleaner flotation from potash ores with increased content of insoluble impurities, which can eliminate the circulation of the intermediate products in the process flow sheet of sylvinite ore processing and increase the KCl recovery into the finished product. Keywords: flotation, potash, halite, alkylamine, alkylmorpholine

Sep 1, 2012

By Hajime Miki, Gde Pandhe Wisnu Suyantara, Tsuyoshi Hirajima, Keiko Sasaki

"Hydrogen peroxide (H2O2) is frequently used as an oxidizing agent in various applications. It has also been reported to reduce the recovery of sulfide minerals. Moreover, the previous work applied H2O2 aqueous solution in selective flotation of chalcopyrite and molybdenite. However, the oxidation method suffered in pilot scale test due to too long conditioning time. Furthermore, the excessive reagent consumption increased the reagent cost, causing the method not economically feasible. Consequently, further improvement is required to reduce the conditioning time and the reagent consumption. The oxidation performance of H2O2 can be improved by using ferrous iron as catalyst, producing a Fenton’s reagent which is more powerful oxidizer than the H2O2 itself. Therefore, the effect of Fenton’s reagent on the floatability of chalcopyrite and molybdenite was investigated in this study. The flotation test results show that selective flotation of chalcopyrite and molybdenite might be possible at low concentration of H2O2 aqueous solution by adding ferrous iron. Moreover, the conditioning time could be shortened by this improvement. To understand the phenomenon, surface characterization using atomic force microscopy (AFM) along with x-ray photoelectron spectroscopy (XPS) analysis were carried out. The AFM images show that the surface of chalcopyrite was readily covered with mountainous features which alters its hydrophobicity after the oxidation treatment. Meanwhile, the molybdenite surface remained clean and relatively hydrophobic. The XPS results indicate that the mountainous features are various oxidation products (i.e., FeOOH, Fe2(SO4)3, CuO, Cu(OH)2). Possible mechanisms of this phenomenon were proposed in this work.INTRODUCTIONConventionally, copper and molybdenum ores are separated in selective flotation circuits by using copper depressants (i.e., sodium hydrosulfide (NaHS), sodium sulfide (Na2S), and Nokes reagent (P2S5+NaOH)). However, these depressants are usually toxic or hazardous. Therefore, various methods have been developed to replace these toxic and hazardous depressants, for example, by synthesizing new non-toxic or low-toxic depressants or by using various oxidation methods such as sodium hypochlorite in an alkaline medium, manganese dioxide, oxygen, ozone, and plasma pre-treatment (Arbiter and Young 1951; Barzyk et al. 1981; Curtis 1941; Hirajima et al. 2014, 2017). Recent study by Chimonyo et al. (2016) reported the effect of H2O2 on reducing the recoveries of sulfide minerals. Moreover, Hirajima et al. (2017) demonstrated that H2O2 depressed the floatability of chalcopyrite and could deliver a selective separation on copper and molybdenum (Cu-Mo) bulk concentrate in flotation process. However, they reported that this method required a higher concentration of H2O2 and a longer treatment time (4.5 h) to get a comparable result to that of using NaHS as copper depressant. Therefore, further improvements are necessary to reduce the conditioning time and reagent consumption."

Jan 1, 2018

By B. Orberger, J. M. Milazzo, S. B. Blancher, J. Lützenkirchen, J. L. Dubos

"Industrial dusts are commonly agglomerated using empirical recipes with binders such as bentonite, while Sludges are agglomerated into mixes. Those materials contaminate the products, are expensive and generate significant amounts of slag. Achieving cold dust agglomeration with little or no binder requires understanding the controlling parameters in order to predict and optimize the process behavior. This in turn necessitates comprehensive dust characterization to base predictions on measurable characteristics. In the present work we collected 13 Mn-rich dusts over all the process chain: feed fines, smelting, and refining dusts, as well as ferromanganese alloy dust. This is the first systematic study of dusts along the Mn-processing chain for chemical, physical and mineralogical parameters. X-Ray Diffraction, Qemscan® and laser granulometry analyses show that the mineralogy, Particle Size Distribution (PSD) and morphology evolves from complex heterogenous to simple, homogenous along the process chain: The mineralogy of the primary ore dusts shows various hydroxides, oxides, carbonates, tectosilicates and phyllosilicates. The furnace dusts contain oxides, tectosilicates and carbonates with volatiles, while the refining dusts present only oxides and metal. Finally, the Metal dust is nearly pure metal. Particle morphologies and PSD vary from jagged, irregular particles with broad PSD (>1 mm to <0.3 µm) to smooth and spherical with narrow PSD (100 µm to <0.3 µm). The Metal dust is an exception with angular particles. The Cationic Exchange Capacities (CECs) of all samples range from 0 to 22 meq/100g. Specific surface areas (SSAs) range from <0.1 to 27m²/g, and seem to decrease with from ore feed to Metal dust. This may be due to the disappearance of hydrated and/or sheet-bearing minerals, since a smaller grain size usually implies an increased SSA. The zeta potential varies strongly over the range of the samples tested. However, beside the Gabon ore which has an Isoelectric Point (IEP) ~ 4.1, the other IEP ranges between 2 and 2.5."

Jan 1, 2018

By Lev Filippov, Vyacheslav Severov, Inna Filippova

"Reverse cationic flotation is a very efficient method of beneficiation of oxidized iron ores when you need to separate hematite and quartz. This method can be also applied to reduce silica content in the magnetite concentrates obtained by wet low-intensity magnetic separation. However, cationic flotation in this case is less effective due to the presence of Fe-Mg-Al-bearing silicates as amphiboles in magnetite ores. These silicates are concentrated in magnetic products and determine the difficulties of their separation from iron oxides when amines and starches are used as collectors and depressants, respectively. The recalculation of the results of the electron microprobe analysis of three calcic Fe-Mg-Al-bearing amphiboles used to characterize cation distributions in structural units and to obtain structural formulas in accord with stoichiometric limits was conducted. The Mössbauer spectroscopy was used to examine the validity of the empirical estimation of cation distributions in amphiboles. The studied samples are metamorphic pargasite and ferrotschermakite and volcanic magnesiohornblende. The crystallographic analyses of the amphibole samples exhibited their heterogeneous surfaces explaining worse floatability of amphiboles with dodecylamine at pH 10. The electrokinetic measurements showed that the position of the isoelectric point of amphiboles is related to a substitution of Al3+ for Si4+ in tetrahedral sites and to an amount of Mg2+ cations in octahedral sites. Thus, the dodecylamine adsorption onto amphiboles through electrostatic interactions is mainly affected by a distribution of these cations in tetrahedral and octahedral sites of amphiboles. In addition, the effect of starch on the depression of Fe-Mg-Al-bearing amphiboles during flotation can be attributed to the presence of metal ions on the amphibole surface, which are capable of forming strong chemical complexes with starch molecules."

Jan 1, 2014

By A. Akcil, O. Celep, C. Erust, E. Y. Yazici1, H. Deveci1

"Recycling of WEEE has already gain prime importance from both environmental and economic point of view. For the recovery of metals from e-waste, many conventional physical, bio/hydrometallurgical and pyrometallurgical processes are proposed. Economic potential of e-waste is mainly driven by its precious metal content. Physical separation methods (e.g. electrostatic, magnetic, eddy current and gravity separation) exploit the differences in the physical properties of metals and non-metals. Physical separation methods are simple and economically sound but they suffer from metal losses and ineffectiveness at fine sizes. Hydrometallurgical processes are promising owing to their relatively low cost, reduced environmental impact, potential for high metal recoveries and suitability for small scale applications. Hydrometallurgical processes can be developed for selective extraction of base/precious metals using suitable reagent systems. Sulphate-based leaching with a suitable oxidant (e.g. H2O2, O2, Fe3+) is effective for copper and other base metals. After removal/recovery of base metals, precious metals can be easily extracted using various lixiviants including thiosulphate, thiourea, cyanide and chloride. However, further research is required to develop new, cost effective and environmentally friendly processes and/or refine existing ones for leaching and, in particular, downstream processes. INTRODUCTION Electrical and electronic equipments are indispensable to modern societies with numerous applications in the field of medicine, transport, communication, education, security and environmental protection. With technological developments and innovations, the replacement of old equipment leads to ever fast accumulation of waste materials such as waste electrical and electronic equipment (WEEE or e-waste). People are upgrading their mobile phones, computers, televisions, audio equipment and printers more frequently than ever before (Babu et al., 2007; Lee et al., 2007). With the rapid growth in technology today, the life span and utilisation period of most electronic and electrical equipment has been reduced considerably with concomitant generation of huge amounts of WEEE over the past several decades. According to statistics presented by Balde et al. (2015), total WEEE produced around the world was 41.8 million tonnes in 2014 and expected to rise to approximately 50 million tonnes by 2018. Kumar et al. (2017) estimated that annual growth rate for the WEEE stream is 3–5% (Singh et al., 2016). The aim of this paper is to provide an overview of physical separation and hydrometallurgical methods available for the treatment of WEEE."

Jan 1, 2018

By Carlos Rabanal, Levi Guzmán

"The concern regarding grinding media consumption rates is as old as the invention of the tumbling mill. Over the years many materials and grinding media shapes have been tested. Through all this, steel grinding balls have proved to be the most effective media for comminution in tumbling mills. There have been several approaches to be able to the wear of the ball charge in any given mill, all of them based on limited empirical evidence. The mining industry still utilizes the Bond Abrasion test that was developed in the 1960´s. As shown later in this publication, this approach shows error greater than 60%. More recently, in 2007, Radziszewski from Mc Gill University has proposed a different total grinding media wear model; this model is based on decoupling the effects of the abrasion, corrosion and impact wear mechanisms. Also in 2007, Benavente, at the time with Moly-Cop Peru, presented an empirical model relating both ore properties and operational conditions that would affect the wear performance of the grinding media. For the database referred in this article, Benavente’s model shows an average error of ± 12% which represents a higher degree of improvement in comparison with previous approaches. The current paper presents recent research conducted by Moly-Cop Peru to further improve the capability of the empirical model originally developed by Benavente to estimate grinding media wear rates. The work performed included extensive determinations of the Bond Abrasion Index for different types of ores, collected at industrial grinding applications where the corresponding operational information was made available. The results of the research enabled us to build a more robust and confident model for estimating the grinding media wear rate. The average error of this new model is in the order of ± 9% which is a significant improvement over the models previously described."

Jan 1, 2014

By Jurgens J. Louw, Vincent C. Smith, Gareth C. Smith, Agit Singh, Dave G. Hulbert

"The flexibility of the PlantStar control platform has enabled Mintek to investigate and easily develop new control strategies for both milling and flotation. This includes a Solids Feed Controller, a Safety Limit Controller, Mill Power Optimiser and Flotation Optimiser, amongst others.The solids feed controller was developed for minerals processing plants using a specialised time delay compensator. Using conventional time delay compensators that are purely model based, results in robustness problems due to model uncertainties. The Mintek Solid Feeds Controller makes use of a plant model, but compensates for model inaccuracies, giving more controller stability and a more robust delay compensation algorithm.The safety limit controller has been developed to switch smoothly between normal and safety control loops without bumping the process. The safety loop output is chosen in accordance with a predefined list of priorities and whether the respective constraint boundaries are exceeded.The Mill Power Optimiser helps to find the power peak on the mill power curve. This insures maximum grind with maximum throughput. It also prevents power dips due to mill overloads, making the milling circuit easier to operate.The flotation optimiser algorithm analyses trends of all accessible variables in the process. The algorithm uses this information to calculate operating conditions that will control the residence times, mass pulls and circulating loads within a flotation circuit to a specified setpoint. Research is being done to now optimise these setpoints in order to achieve better recovery."

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 E. Barsky

The composition of multi-component materials is proved to be unambiguously determined by the composition uncertainty parameter (composition entropy). At the same time, every component, depending on its content, introduces a certain value into this parameter. Quality criterion of multi-component separation is determined by the total change of this parameter for all products obtained as a result of the separation process. This parameter can unambiguously estimate both multi-product separation and complicated schemes of modern beneficiation plants. It can be used to estimate binary mixtures separation, too. During the optimization of multi-product separation, another problem arises, which is not peculiar to binary mixtures. In this case, the total efficacy depends on the order of separation boundaries, as well. In the present paper, a specific example of initial product separation into seven products by six boundaries is investigated. It is clear that with respect to a single boundary, two products only can be obtained. In this case, the separation optimum is shown to correspond to the separation of boundary-class particles equally into both products. We have also established that from the point of view of entropy, the maximal possible separation efficacy corresponds to equiprobable composition of the initial mixture, i.e., the fine product quantity in the material to be separated is equal to that of the coarse product. Three groups of experiments were carried out. In the first group, the boundaries were consecutively specified from the finest to the coarsest one. In the second group, the boundaries were set vice-versa, i.e., consecutively from the coarsest to the finest one. In the third group, no sequence was observed. At every separation stage, a boundary was specified in such a way that the separated material composition was as close as possible to equiprobable one relative to this boundary. Total efficacy was different in all the three cases. In third group of experiments, its value is the highest, which confirms the advanced supposition. The obtained results are phenomenological, ? they can be applied to any processes of solid, liquid and gaseous materials separation.

Jan 1, 2014

By Y. M. Fu

In order to evaluate the flotation process, the process flow sheet was investigated. The process mineralogy of main products was studied. Through chemical mineralogical and screening analysis as well as surveying using a microscope and scanning electro-microscope, the oxidation degree and mineral composition of main-products the liberation of main minerals, the occurrence of elements such as Pb, Zn were revealed. It is pointed that to determine the flotation process, the type of prod-ucts optimum grind of original ore and middling was provided on the basis of liberation of main minerals is reliable. As correct finer ground original ore, first high-grade lead-concentrates and zinc-concentrates fast was floated from a great part of free of the galena and sphalerite of liberated. Then for finely re-ground middling of locked mineral grains of difficult liberation, mixing lead-zinc-concentrates second was floated. The four products was best in contact with characteristic of ore of Fan Kou. Therefore be obtained certain to successful economic effect.

Jan 1, 2014