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By Rong Fan, Andrea Gerson

"The small recovery of Ag, often in the order of 50%, by traditional flotation and leaching process strategies is closely related to the complicated and heterogeneous nature of Ag-bearing minerals with Ag typically being associated with numerous minerals within any given ore-body. Moreover, grain sizes may be extremely fine with micron-scale common. In order to design cost-effective Ag-bearing mineral flotation and leach recovery strategies it is firstly necessary to characterise the speciation of Ag and its correlation with other elements, e.g., Cu, As and Sb, within the ore matrix and process streams. The traditional QEM-SCAN analytical approach can prove problematic for some mineralogies due to difficulties in recognising degrees of crystallinity, polymorphs, complex solid solution series, high value trace element mineralogy, very fine grained materials; and the requirement for a comprehensive data base. Moreover, there is difficulty ‘seeing’ either surface films or surface contaminants which can both lead to poor flotation performance. There is therefore clearly a need to develop confirmatory and complementary approaches when these uncertainties arise. Synchrotron X-ray microprobe analysis provides a powerful tool for the mineralogical characterisation of finely segregated heterogeneous Ag-containing materials. These measurements enable comprehensive characterisation of the Ag-bearing components using synchrotron microprobe X-ray fluorescence mapping (µ-XFM), X-ray diffraction (µ-XRD) and X-ray absorption spectroscopy (µ-XAS). Further analytical strength is provided by principal component analysis of laboratory ToF-SIMS data which enables the statistical identification of correlated surface species enabling examination of surface chemical characteristics responsible for mis-reporting of Ag containing components within flotation streams. We describe the application of these techniques to a selected Ag-containing feed and tail and demonstrate how these compliment and extend traditional analytical methodologies."

Jan 1, 2014

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

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

Jan 1, 2003

By Jens Markowski

The EU Directive 2000/53/EC on end-of life vehicles (ELVs) states that in 2015 at least 85 wt.-% of a vehicle has to be reused or recycled. This result in the obligatory need to separate additionally metallic and other components of the automotive shredder residues (ASR), so that they can be professionally prepared for recycling and reuse further. Currently the iron-containing fines of ASR are deposited as it is not possible to process in blast furnaces due to its particle size (< 4 mm), composition and material properties. Additionally problems are also caused in handling and transportation (dust) of the material. This work focuses mainly on the ASR materials utilization in blast furnaces. Material was further separated into two consecutive fractions by carrying out repeated crushing and magnetic separation twice. The two fractions have significantly higher iron content (up to 75 wt.-%) compared to the initial material mixture. The materials were assessed for their usage in blast furnaces based on the possible pelletisation with and without binders, stability of pellets, shape and size of pellets, etc. Pelletisation of the material was carried out with a single mould pellet press. Further lignite coal was added to the mixture as additive which improved the pelletisation behavior and the mechanical stability of pellets. Lignite coal was chosen as a reducing agent in the blast furnace process contributing towards additional savings in energy supplied. The experiments reveal that the production of pellets from iron-containing fines is possible with a lignite coal admixture of about 15 wt.-%. These pellets displayed good mechanical stability and can be used in blast furnace processes in recovery of the recyclable metals which are currently not recycled. The recycling of not yet recyclable metals would reduce the deposition and can be easily adopted into the economic cycle by their utilization. Keywords: Automotive shredder residue (ASR), FE-fines, pelletisation

Sep 1, 2012

By Klaus M. Hahn, Kurt Aasly, Jutta Lennartz, Hermann Wotruba, Ben Snook, Przemyslaw B. Kowalczuk, Rolf Arne Kleiv

"Seafloor massive sulphide (SMS) deposits have been identified as important marine metal resources for the future. However, literature on mineral processing of SMS is currently limited, and to date, no research has been published on processing of SMS from either active or inactive hydrothermal vent fields on the Arctic Mid-Ocean Ridge. In this paper, individual SMS rock samples from the Loki’s Castle area were tested. Chalcopyrite, isocubanite and sphalerite represented the main copper and zinc bearing minerals in the SMS samples, whereas the gangue consisted of barite and silica. Based on the X-ray transmission response (XRT), i.e. differences in the atomic number of elements in tested samples, and using portable XRF (PXRF) values of elemental composition, individual particles were classified as a either product (low barium / high to low silicon / high copper and zinc) or waste (high barium / high silicon / low copper and zinc). The classification was based on the elemental composition of the samples with the cut-off grade equal to 0.5% for copper. It was shown that the XRT discrimination analysis correlated well with elemental (PXRF) data classification. The results clearly indicate that X-ray transmission sensor-based sorting can be used a useful technique for preconcentration of SMS rock samples. INTRODUCTION Due to different compositions of investigated samples, sensor-based sorting is a useful technique for preconcentration of different materials. The aim of using sensor-based sorting is to upgrade an ore by reducing the quantity of overall waste material reporting to the next processing stage. This can be achieved by eliminating (reducing) the waste fraction. By applying sensor-based sorting, the energy consumption for particle comminution as well as the required process water and reagents can be decreased. The total volume of the waste rejection leads to a proportional reduction in the total energy costs (Lessard et al., 2014, 2016)."

Jan 1, 2018

By N. R. Mandre

In the present work an attempt has been made to study beneficiation of low-grade iron ore associated with manganese clay by selective flocculation. The representative samples obtained for this purpose were initially subjected to chemical and mineralogical studies. The chemical analyses indicated 42.56 % Fe, 6.25% Mn, 8.72 % SiO2 and 13.60 % Al2O3 in the representative sample. The mineralogical analyses carried out under optical microscope showed that the ore mineral predominantly comprised of iron oxides and hydroxides along with manganese and silicate as gangue minerals. Prior to the beneficiation studies, the samples were subjected to settling tests. These tests were carried out by using poly acrylic acid (paa), poly acryl amide (pam) and guar gum (gg) as the flocculants. From these studies it was observed that settling rate of particles increases with increase in pH and a maximum settling rate of 0.23 cm/secwas obtained at pH 9 in presence of poly acryl amide. Further, the samples were subjected to selective flocculation studies using above-mentioned reagents. From these studies better results were obtained in the experiments carried out with poly acryl amide as the flocculant. Thus, it was possible to upgrade the iron content from 42.5 to 53%, with a recovery of 92%. However, 51% Fe with recovery of 87% and 50% Fe with recovery of 94 % was obtained using poly acrylic acid and guar gum respectively.

Sep 1, 2012

By P. K. Fedotov

Centrifugal separation opens its new application fields in the Mining Industry. The up-to-date equipment for ultra-fine ore and concentrates grinding allows an efficient use of centrifugal concentration for micronic gold grains recovery. Moreover, advanced centrifugal concentrators are presented on the market: concentrators with continuous concentrate discharge designed both for ore and non-metallic minerals concentration process. The conducted tests proved the centrifugal concentration to be efficient process for gold recovery from finely ground concentrates and ores (less than 20 µm). Knelson concentrator application for such a fine material in different process circuits makes possible to raise the total gold recovery level of plants. In the circuits of coal plants and in course of coal slimes treatment the centrifugal concentration may be used before flotation in order to improve process performances. A centrifugal concentrator KC-CVD with continuous concentrate discharge working on 0.3 (0.5)mm fraction before flotation is

Jan 1, 2014

By J. D. Miller

The more efficient production and use of mineral resources is a major objective of our sustainability efforts. Resource characterization is a critical component for optimization of the mine-to-mill process, including innovative processing for sustainable growth. Such characterization is now referred to as geometallurgy, with advanced instrumentation including, for example, particle size analysis, XRF, XRD, NIR, automated SEM/EDAX analysis (QEMSCAN, MLA), and high resolution X-ray micro tomography. Geometallurgical information is important for exploration, deposit evaluation; mine planning, design and analysis of separation processes, etc. Characterization of mineral processing particles in 3D is now possible using high resolution X-ray micro tomography (HRXMT), and such HRXMT systems have been installed at several laboratories around the world. After review of principles, the features of such HRXMT analyses are presented including size/shape, damage state, mineral phase identification, and evaluation/isolation of trace mineral particles. With new algorithms for image analysis, quantitative data treatment is possible for construction of liberation-limited grade/recovery curves, for the determination of specific crack surface area, and for complex texture analysis including grain exposure. Finally, new tomographic characterization possibilities are discussed to provide the foundation for the development of advanced, innovative processing strategies for sustainable growth. Keywords: X-ray tomography, resource characterization, HRXMT, particle size analysis XXVI INTERNATIONAL

Sep 1, 2012

By M. A. C. Goes

Over the last twenty years CETEM has been involved in the preparation and certification of reference material from ores, concentrates and related materials for use in analytical laboratories associated with mining, metallurgy and earth sciences. CETEM provides reference materials from mineral samples, not available from the existing sources, to meet the needs of the mining and mineral industry. CBPA-1 and CBPA-2 respectively are samples of copper sulphide ore and flotation concentrate, both originated from Sossego Mine, located in Pará State, Brazil. The batch characterization was carried out by a collaborative measurement program with participation of 20 industrial, commercial and government laboratories from South America, North America, Europe, Asia and Africa. The certificates and report were issued in December 2007 (http://www.cetem.gov.br/ mrc/ing). The objective of this paper was to describe the procedures for material preparation and the collaborative approach involving a collaborative interlaboratory measurement program to certify CBPA-1 and CBPA-2.

Jan 1, 2014

By L. Y. Zhang

The metallic sulphides in Jinchuan Mine are relative friable and the gangue minerals suffer of wide secondary change, the overgrinding of metallic sulphides and sliming of gangue minerals are the main cause that makes the mineral separation indexes difficult to improve. So changing the process of grinding, and classification, and optimizing the particle size distribution of grinding product is the key improving the separation performance of Jinchuan nickel and copper ore.

Jan 1, 2014

By A. Mainza, H. Hill, L. Bbosa

"The main objective of ore breakage characterization is to quantify the relationship between the energy supplied for breakage and the size of the resultant progeny. In this study, the ore breakage characteristics of drill core particles and crushed particles were compared. Single impact breakage tests were conducted on a basalt ore sample using the JK rotary breakage tester. The size-dependent model by Shi and Kojovic was used to fit the breakage data because the effect of initial particle size is accounted for in the model. It was found that crushed particles consistently gave a higher degree of brokenness than drill core particles and the differences were attributed to the internal structure of the particle. Drill core particles contain a lower crack density (paths of weakness) than crushed particles which have been pre-weakened during the crushing process. An increase in crack density is directly related to a decrease in the minimum threshold energy. Upon application of a stressing force above the stress threshold, particles with a higher crack density will fracture more easily because of a higher rate of crack propagation due the numerous paths of weakness available. It was therefore concluded that under the same conditions, drill core particles are more competent than crushed particles. INTRODUCTION Comminution devices have commonly been reported as being the largest energy consumers in mineral processing circuits (Napier-Munn, 2015). Cleary (1998) reported that the inefficiency of comminution devices is a result of less than 5% of the supplied energy being utilized for breakage, with the majority being expended as heat and noise. With steadily declining fossil fuel supplies and a looming global energy crisis, the mineral processing industry has increased its focus on energy reduction measures. Ore breakage characterization plays a critical role in the design and optimization of comminution circuits (Tavares and King, 1998). The main objective of ore breakage characterization is to empirically quantify the relationship between the energy supplied for breakage (specific input energy) and the size of the resultant progeny through laboratory particle breakage tests (Napier-Munn, 1996). Commonly used laboratory breakage devices include the Drop Weight Tester (DWT), Split Hopkinson Pressure Bar (SHPB) and more recently, the JK Rotary Breakage Tester (JKRBT). Typically, a standard single impact breakage test procedure consists of a matrix of experiments on particles in four to five narrow size fractions each tested at low, medium and high energy levels. The resultant progeny of each test is sized to obtain a particle size distribution (PSD) from which the degree of breakage, usually in the form of a t10 value (percentage of the progeny material that passes 1/10 of the feed size) can be obtained for each size fraction and energy level (Napier-Munn, 1996)."

Jan 1, 2018

By E. Guerrini, M. Maccagni, J. Nielsen

"Lead is the most important material able to meet the current demand for energy storage. The lead acid battery is reliable, efficient and inexpensive. Continuous developments in battery construction are providing improvements in all aspects of the batteries’ performance. The lead acid battery is both the main lead product and the main raw material for lead production. More than half of the lead produced is from secondary smelters where batteries are the most important feed material. The environmental pressure on lead production has been increasing for many years, and continues to become stronger and stronger. The lead production processes and technologies themselves will require updating to meet the new regulations. Although they are very strict now, they will become even more so and current technologies may not be sufficient. Because recyclability is a strong point for the lead acid battery, the secondary smelters need to reduce the environmental impact as much as possible. In recent years, the secondary smelters underwent impressive changes in this direction, but some more improvements are possible. Electrochemistry can offer a step change improvement in making secondary lead production more environmentally friendly. Engitec has developed an electrochemical process base on a very high current density (high productivity) cell using an inexpensive electrolyte and at a relatively low cost. In this paper, the latest update on the technology is provided. INTRODUCTION The lead acid battery is considered the “walking dead” by some new technologies trying to replace it. It has played and will continue to play a very important role in our lives because it is inexpensive, fully recyclable and the existing lead and the mine reserves guaranty enough material for the extended future. According to the life cycle, the lead acid battery is the cheapest and the most effective system to store energy. Lead is practically a close loop where lead battery production consumes more than 80 % of the produced lead but contemporarily it is the most important raw material for the production of metallic lead. In fact, nowadays, the secondary production has overcome primary production and this trend is expected to continue. Primary lead is the make-up material for the existing battery production and the source of lead for the construction of the new ones."

Jan 1, 2018

By J. Lampke

The superior characteristics of iron ore pellets compared with natural ore and sinter are well known. Due to the higher grade and bulk density they show improved transport and material handling properties. While charging blast furnaces with pellets an increased productivity is realized through pellet?s uniform structure and composition. The increased productivity is caused by a high permeable furnace burden with a decreased coke usage via fuel injection and oxygen enrichment. Therefore, a narrow pellet size distribution and a minimum content -6.3 mm are necessary (Meyer, 1980). The required pellet size distribution can be achieved on the one hand by screening the fired pellets after the induration furnace and recycle the undersized pellets. On the other hand it is possible to produce high quality iron ore pellets with a high degree of sphericity, the important narrow grain size distribution ranging between 9 to 16 mm with high green strength directly in the pelletizing device. To produce high quality green pellets, possibilities and knowledge about adjustments of the pelletizing device are necessary. The paper presents a classification of state of the art pelletizing systems in accordance with the advantages of the pelletizing disc and pelletizing drum in issues like adjustability, green pellet quality, the recycling rate and the space requirement. By a systematization of the influences on pelletizing the common reliance of objectives on influence like pelletizing moisture, disc inclination, rotational speed, mass flow and rim height are given. A variety of industry-proven examples are shown, too. Keywords: Pellet, iron ore, pelletizing, pelletizing disc

Sep 1, 2012

By V. Hudecek

Problems of sudden outbursts of rock and gas present in deep mine mining ones of the most complicated interrogation. It is searching for the methods of prediction and prognosis that can be most useful for the government of these phenomena. Till now the pressure and the desorption of gas in bore holes was consider to be the decisive criteria. By the work of authors with using of statistical date was verify that for considerable reliability of forecast and prevent outbursts is necessity investigate characteristics of workplace and other indicators. These indicators were analyzing and assemblage into mathematical dependences which represent active and passive force asserting with in the process of rush. It was validated by using the equations which are presented in the manuscript that the accuracy of pre-diction of the phenomena is higher and methods of preventions are better also.

Jan 1, 2014

By A. V. Bogdanovich, S. A. Urnysheva

"Gravity and X-ray luminescent separation methods are generally used in processing of diamond ores. X-ray luminescent separators are applied for separation of diamonds from feed ore size fractions from 100 to 10-15 mm size and for final treatment of gravity concentrates over 1 mm size. Gravity separation machines used for diamond ores separation are heavy medium cyclones and pneumatic jigs. One of the most important parameters, to a large extent affecting diamonds recovery from ore, as well as processing costs and specific energy costs, is size of dumped final tailings. That was exactly the purpose of the studies, the results of which are described in this paper. The studies performed on different ores showed that in order to achieve high recovery results, it is necessary to dump heavy medium separation tailings below 3 mm size. Separation of final tailings of -6+1 mm size by jigging is also possible. However, with a view to exclude extra diamond losses, it is necessary to maintain jigging concentrate yield approximately at 25% from starting feed, with its subsequent cleaning in heavy medium cyclones. In addition to that, it is necessary to separate 20-25% of middling with diamonds content at feed ore level and subject it to grinding. This will complicate flow sheet, but reduce load on heavy medium cyclones. In order to develop optimal flow sheet for gravity concentration of a specific diamond ore, large-scale investigations are required, including technical-and-economic assessment of separation alternatives. INTRODUCTION In processing of diamond ores, gravity and X-ray luminescent separation methods are generally used. It is common practice to apply X-ray luminescent separators for separation of diamonds from feed ore size fractions from 50 (100) to 20 (10) mm size and for final treatment of gravity concentrates over 1 mm size. With that, X-ray luminescent separation tailings larger than 3-6 mm size are reground and delivered to gravity concentration processing stage. Middling products circulation volumes are large, not infrequently necessitating decrease in concentrating plants capacity, especially with mining in deep workings of deposits, where ore strength is higher (Goryachev, 2010; Vaginov, 2000; William, 1988). Diamond ores preparation before processing is accomplished by means of roll-screw crushers and autogenous grinding mills, minimizing probability of free diamonds damage in liberation from barren rock. In re-crushing of size fractions that are “difficult” in autogenous grinding, high pressure grinding rollers are applied (Burchardt, 2014; Fedotov, 2011a, 2006b)."

Jan 1, 2018

By Zhiyong Gao, Ruiying Fan

"Crushing and grinding are the prerequisite processes in many industries, such as minerals processing and powder technology. During crushing and grinding, minerals will cleave or fracture along the directions by broken the interlayer bonds (e.g., ionic bonds), generating some commonly exposed surfaces. The broken (or dangling) bonds at the generated surface makes the surface more active and determine the reactivity of the surface. In this work, the population of broken (or dangling) bonds on commonly exposed surfaces of fluorite mineral (a chosen model mineral) was calculated. Based on the calculated broken bonds information, the anisotropic surface reactivity of fluorite such as surface energy, surface relaxation, dissolution, wettability, surface charge and adsorbability, were discussed. The results show that the surface broken bonds density, which is positively related to the surface energy, can be used to predict the cleavage nature, surface relaxation degree and surface stability of fluorite crystal. The distribution characteristic and the number of broken (or unsaturated) bonds of surface active atoms (like Ca for fluorite crystal) can be used to predict and explain the anisotropic wettability, surface charge and adsorption mode and strength of organic molecules on different commonly exposed surfaces. It is easy to conclude that the calculation of surface broken bonds can serve as a fast and accurate way to start the mineral chemistry studies. These findings will be helpful to the mineral/material chemistry research in related interfacial science communities.INTRODUCTIONGrinding for mineral liberation is a prerequisite for a successful flotation separation. Also grinding for size reduction is a prior process for a favorable powder technology. During the grinding process, the minerals / materials will cleave and fracture along certain crystal directions with relatively weak interlayer chemical bonds1 to form a number of common exposed surfaces. Exposed surfaces are the outer boundary of a solid substance. In the mineral / material block, the bonding orbital of the atoms is filled with electrons and the atoms are in a steady state. Atoms on these exposed surfaces appear to show dangling bonds (or broken bonds) by losing chemical bonds to adjacent atoms in the previous block. Therefore, surface broken bonds serves as an initial property of a fresh surface. The lattice arrangement and crystal orientations causes differences in the number of dangling bonds on each exposed surface, i.e., anisotropic surface broken bonds2. The anisotropic dangling bonds enable the exposed surfaces to show varying degrees of surface reactivity (including surface energy, surface charge, surface relaxation, dissolution, wettability and adsorption behavior), known as anisotropic surface reactivity."

Jan 1, 2018

By Zofia Swierczek

This paper reports the results of a detailed mineralogical study of typical, low-grade Australian nickel laterite run-of-mine ores. Successful development of an effective beneficiation process for upgrading such low grade laterite ores relies on good knowledge of the laterite mineralogy and the value metal(s)? distribution characteristics. Both QEMSCAN and quantitative X-ray diffraction techniques were used to conduct the mineralogical analysis of three types of laterite ores, and the results were compared with those obtained by chemical analysis. Some of the major challenges faced included accounting for the mismatch between the nickel values measured by QEMSCAN and those recorded by chemical analysis. This was primarily due to the relatively low concentration of nickel in the ores and its wide dissemination among several major host minerals in complex association. Careful analysis showed that the limit of nickel detection in iron oxide host mineral grains under normal operating conditions was around 4%. Keywords: nickel laterites, mineralogy, characterisation, QXRD, QEMSCAN

Sep 1, 2012

The present study investigates the nature of gold mineralogical distribution and association in a Cu-Au flotation circuit (1.6 g/t Au, feed head grade). The approach used in this study involves a combination of bulk gold assay and quantitative X-ray diffraction (QXRD), on a size-by-size basis, followed by QEMSCAN analysis on the -75+53 µm, -53+38 µm and -38+20 µm size fractions. The QXRD and QEMSCAN analysis showed that gold mineralogy is complex and fine-grained in the flotation feed, particularly in the -38+20 µm size fraction. Gold and pyrite concentration follow each other closely, suggesting gold-pyrite association. Quartz as the major gangue mineral shows a bi-modal distribution with respect to particle size. The identified gold particles were completely locked (~94 %) in pyrite as fine inclusions and 6 % locked as complex aggregates (-75+53 µm size fraction) whereas in the -38+20 µm size fraction, the identified gold grains occur as fine inclusions (~1-3 µm) within pyrite and silicates. However, in the intermediate size fraction (-53+38 µm), 75 % of the identified gold grains (10-22 µm) were over 90 % liberated and 25 % associated and locked in pyrite and complex aggregates (~2-4 µm). The identified gold grains in the -53+38 µm size fraction occurred as native and electrum with varying silver concentration between 8 and 20 % by weight. In the -38+20 µm size fraction, a gold telluride was also identified. Based on the mineralogical analysis of the feed, possible flotation strategies are discussed. Optimizing the flotation of pyrite is suggested as the primary Au recovery strategy. Keywords: flotation, pyrite, gold, liberation, QXRD, QEMSCAN

Sep 1, 2012

By Wei Sun, Ruolin Wang, Jianjun Wang, Xiaodong Li, Honghu Tang, Yuehua Hu, Anh V. Nguyen, Haisheng Han, Kefeng Chen, Zhao Wei

It is difficult to separate scheelite especially from fluorite with fatty acid collectors because the adsorption mechanism of these collectors occurs through chemisorption of the oleate ion onto the mineral surface. A simplified flotation process using Pb-BHA complexes was developed to replace the energy-inefficient Petrov’s process of using a fatty acid, increasing the recovery of scheelite and reducing the cost. The relationship between surface chemical properties (crystal chemistry, solubility, and Zeta potential) of minerals and flotation by using a fatty acid or Pb-BHA complexes was studied in detail to provide new insights into the selective separation mechanism. The results indicate that the scheelite surface exposes more O atoms than Ca and that they are negatively charged due to the anisometric dissolution of Ca and WO4, which provides the possibility for separation using selective interfacial reaction. The FTIR and Zeta potential results indicate that both chemical and electrostatic adsorption play an important role in the adsorption of Pb-BHA complexes on the scheelite surface. The XPS results of the atomic composition and binding energies confirmed the presence of the adsorbed Pb-BHA complexes and that O and Ca may be the active adsorption sites. Therefore, scheelite was able to be collected by forming either a Ca-O-Pbcollector or W-O-Pb-collector (BHA). However, fluorite was only able to be collected by a fatty acid collector and colloidal [H2SiO3]n -, and a high temperature was needed improve the selective desorption of the adsorbed fatty acid collector by forming Ca-[H2SiO3]n - on the fluorite surface, resulting in serious problems in industry. However, the Pb-BHA complexes significantly contribute to improving the recovery of scheelite minerals, simplifying the flotation process, and circulation of the residual reagents and water. The new process has been applied in Shizhuyuan Mine, and improved the recovery by almost 10%.

Jan 1, 2018

By Tiago de Souza, Caroline Gonçalves, Carlos Eduardo de Castro, Everton Dias

The Miraí plant from Votorantim Metais, has two screening stages to the bauxite classification after scrubbagem. The final product has hold the larger size of 0,84 millimeters (20 mesh). There are two sieves Haver & Boecker (model R-TE 3658 x 10972), which have four modules with cut size sieves of 10 mesh (1.70 millimeters) and ¼ inch (6.35 millimeters) on the primary screen, and 20 mesh (0.84 mm) on the secondary screen, all made of polyurethane. The actual configuration was established according to the empirical tests realized that aimed the increase material load on the secondary screening. However, having in mind the screening process improvement and use the fractions smaller than 0,84 mm, which have significant levels of Alumina and low reactive silica, was proposed a new test of change the sieves opening for 6 mesh in the primary screen and 28 mesh for the secondary sieve. The objective of this work was measure the ore alterations on the particle size distribution on the screening steps, increasing the plant weight and ratio recovery before and after the test.

Jan 1, 2014

By Kwan Ho Kim

In this study, free fall tests are conducted with the objective of understanding the breakage properties of waste concrete for the guide of the direction of the better comminution process. Waste concrete of 75mm×53mm is tested at various drop heights with or without heat pretreatment. Test results indicate that a block of waste concrete does not break by free fall, but eventually breaks by repeated free falls. The number of free falls required for complete separation of large aggregates from the cement mortar considerably reduced when the samples were heated at 400?. Therefore, a great energy saving can be obtained when heating the waste concrete prior to crushing. The energy saving was found to be dependent on the height of free fall but in all cases, was still large enough to offset the additional energy required for heating. Also, it was found that the heat pre-treatment gives an additional advantage in that it produced cleaner recycled aggregates. This may result from easier detachment of cement mortar from the aggregates due to weakening of bonding forces by heating. By analyzing the size distribution of the crushed product, a free-fall breakage model is developed using the particle breakage ratio and the breakage pattern. The developed model can be used to predict and to analyze waste concrete processing circuit.

Jan 1, 2014