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By Gabriela Pino, Maurício Torem, Diego Veneu

Because of its simplicity, economy and biocompatibility, research regarding the use of microorganism for decontaminating heavy metals produced by many industries is an area of growing interest. Also, there is a stringent need for the control of toxic metals produced during various production processes and released into the aqueous environment in order to avoid damage relevant to soil or groundwater contamination. Among the available treatment technologies, sorptive flotation has been considered as a promising alternative for the wastewater treatment. In the present study Streptomyces lunalinharesii strain was applied as bioreagent for the removal of copper, cadmium and zinc. The removal of those metal ions depends mainly on the respective pH value, influencing the aquatic speciation during the process, as well as the zeta potential of the system and biomass concentration. Langmuir and Freundlich isotherms have been depicted. Dispersed air flotation was applied as the subsequent separation method for harvesting the suspended metal laden microorganisms, following the biosorption of copper, zinc and cadmium. The investigated parameters (in batch mode, laboratory scale) were in this case the saturator pressure, the coagulant concentration and the recycled flow. Applying the optimum defined conditions, over 60% removal of metal ions have been achieved in one stage and simultaneously, quantitative separation of the used (metal-loaded) biomass has been obtained.

Jan 1, 2014

By S. Sheng, Y. G. Huang, W. Chai

"Polyacrylamide (PAM) is a typically synthetic depressant and may be used as a depressor of pyrite. The modification of polyacrylamide may improve its physicochemical properties and performances. Sulfonated polyacrylamides (SPAM) with different sulfonation degree (SD) were prepared using sodium sulfite as the sulfonating agent, and the interactions of SPAM and pyrite were investigated by the adsorption experiment in this work. The adsorption tests of SPAM on pyrite were conducted as a function of sulfonation degree, pH value and contact time. Pyrite and SPAM were constructed and optimized through MS software. The interaction mechanisms of sulfonated polyacrylamide and pyrite were simulated by molecular dynamics simulations. The results show that the adsorption capacities of SPAM at neutral and weak alkaline conditions are higher than that at acidic and strong basic conditions. The high sulfonation degree favors the adsorption of SPAM on pyrite surface. The adsorption process can be described best by the pseudo-second order kinetic model. Molecular dynamics simulations show that the adsorption of sulfonated polyacrylamide on pyrite is better than that of polyacrylamide. Sulfonated polyacrylamide can be used as a potential depressant of pyrite with the main interacting mechanism of hydrogenbond force.INTRODUCTIONPyrite is the most abundant sulfide mineral and often associated with valuable minerals such as galena, chalcopyrite, sphalerite, molybdenite, gold, diaspore as well as coal (Forrest et al., 2001; Jaiswal et al., 2015; Maier and Dobiáš, 1997; Qiu et al., 2017; Xin and Liye, 2010). Froth flotation is the most popular method to remove pyrite from valuable minerals. Pyrite could be floated as the flotation concentrate either by its hydrophobicity or activation by metal ions (Chandra and Gerson, 2009). What is more, pyrite could be seperated as flotation tailing by adding highly selective depressants including inorganic and organic modifiers. Polysaccharides polymers and lignosulfonate-based biopolymers are common natural organic depressants (Deng et al., 2017; Mu et al., 2016). While the synthetic organic products have proved to be particularly versatile in terms of molecule tailing capability and controlled structures (Boulton et al., 2001a; Raffa et al., 2015)."

Jan 1, 2018

The flotation efficiency of magnetic concentrate of the Anhui hematite ore, which includes a great quantity of iron-bearing silicates, has been studied through reverse flotation test with a new type of collector Fly-102. The results indicate that collector Fly-102 has a strong adaptability to the variation of temperature, when the flotation temperature is in the range of 10? to 35?, using collector Fly-102 can obtain good flotation indexes. Collector Fly-102 has a strong adaptability to the variation of the slime contents and grades of the flotation samples. When the content of slime and the grade of the flotation feeds are 30% and 55.63% respectively, under the condition that the temperature is 15?, the open circuit flotation test was carried out with collector Fly-102. After one-stage roughing, one-stage cleaning and two-stage scavenging, a better result is got, the grade of iron concentrate reaches 67.12%, and the recovery of iron concentrate comes up to 84.15%.

Sep 1, 2012

It is well known that the crushing and grinding steps in the mineral processing of ores represent a substantial proportion of total energy, cost and carbon emission in mining. For instance a recent study calculated that 36% of the energy consumed by gold and copper producing mines in Australia was attributable to comminution (Ballantyne et al, 2012). Understanding this component of a business is essential in a world seeking to lower production costs, improve earnings and reduce its carbon footprint. The issue commands the attention and support of industry leaders in the mining sector, government, equipment manufacture, engineering design and research organizations. Furthermore, several researchers have often stated that globally, comminution processes consume between 3-4% of the world?s electrical energy production (Daniel and Lewis-Gray, 2011). In 2009-10, Australia?s Federal Government Energy Efficiency Opportunity (EEO) participants in the mining sector used 336.5 PJ, representing approximately 6 percent of Australia's total energy use. It is evident that the current practices of breaking rocks in tumbling mills are relatively inefficient (Fuerstenau and Abouzeid, 2002). Research and improved engineering design has established that a range of improved blasting, crushing and grinding techniques and flow sheets may lower project costs and carbon footprint. These include relatively simple process flow sheet strategies such as gangue rejection or pre-concentration prior to size reduction, a better combination of grinding technologies (both current and new systems), and selection of coarser grind sizes where ore and waste mineralogy allow. Yet, despite this systematic and detailed research, the industry remains somewhat reluctant to implement these strategies. CEEC (Coalition for Eco-Efficient Comminution) was established in 2011 to support knowledge sharing and change in an area of high-energy consumption for the global mineral industry. CEEC is a not-for-profit industry company, funded by grants from world wide industry companies, whose mission is to accelerate knowledge and technology transfer in the field of energy-efficient comminution. The key benefit to the mining sector arising from CEEC?s activities will be an increase in the rate at which more energy-efficient comminution data sets, processes, and technologies are developed, demonstrated, shared and applied. This will contribute directly to the industry?s target of reducing operating costs and carbon emissions. CEEC International Ltd and JKTech Pty Ltd teamed together to facilitate the inaugural CEEC Workshop, in June 2012. The purpose of the workshop was to produce a roadmap to provide guidelines for how (1) operations can achieve best EEC practice in the short to medium term, in collaboration with vendors, engineering companies and other service providers, and (2) what R&D is needed to achieve paradigm change in EEC in the medium to long term, e.g. 75% reduction in comminution energy in 10 years.

Sep 1, 2012

By Naoki Hiroyoshi, Hajime Miki, Tsuyoshi Hirajima, Masami Tsunekawa

"Acidic solutions for chalcopyrite leaching contain cupric, ferrous and ferric ions, and the oxidizing power of the solutions is indicated by a redox potential, determined by the concentration ratio of ferric to ferrous ions. This paper reviews our previous studies on the redox potential dependence of chalcopyrite leaching in sulfuric acid solutions. Leaching experiments indicated that copper extraction rate was accelerated by cupric and ferrous ions , and was higher at potentials below a critical value (critical potential) in the presence of these ions. This was in good agreement with the results of electrochemical measurements, i.e. in the anodic polarization curves for a chalcopyrite electrode, active-passive behavior was observed when cupric and ferrous ions co-exist, but the activation at low potential did not occur without these ions (Figure 1). The analysis of the AC impedance spectra for chalcopyrite electrode indicated that a high-resistance passive layer grows on the chalcopyrite surface without cupric and/or ferrous ions, and that coexistence of these ions causes a formation of another product layer and inhibits the passive layer growth at low potentials.These results are explained by a reaction model assuming the formation of intermediate Cu2S due to chalcopyrite reduction and the subsequent oxidation of the Cu2S. The critical potential corresponds to the redox potential of the Cu2S formation and the predicted values matched with the experimental results. Catalytic effect of silver ions on chalcopyrite leaching was also discussed based on experimental results and the above model."

Jan 1, 2003

By Y. H. Wang

Micro-flotation tests of spodumene, beryl, quartz and feldspar have been carried out by using CaCl2 and FeCl3 as modifiers and a blending collector of oleic acid and hydroximic acid. CaCl2 shows efficient activation for spodumene when pH is above 11.5, and FeCl3 exhibits a markedly activation and good selectivity for spodumene in the range of pH 4 to 10. The main species of CaCl2 are CaOH+ and Ca(OH)2 when pH is above 11.5, and the main species of FeCl3?6H2O are Fe(OH)+2 and Fe(OH)3 during the pH range of 4 to 10. A selective flotation of spodumene and beryl from pegmatic ore had also been completed while using FeCl3?6H2O as activator and the blending collector. A bulk concentrate containing 1.087% BeO and 4.70% Li2O has also been obtained in the flotation of spodumene and beryl from pegmatic ore assaying 0.097% BeO and 0.45% Li2O, and the recoveries of BeO and Li2O in concentrate are 74.38% and 69.50% respectively.

Jan 1, 2014

By V. A. Feofanov

Technogenic water of ore mining enterprises, nonferrous metals operations, the enterprises of electroplating and instrument making, containing copper in the form of those or other connections can serve as perspective sources on receiving the copper-bearing raw material. Extraction of copper from the given water also solves a problem of water treating from a toxic component that reduces environmental load at evacuation of water in an open basin. The method of case hardening allows extracting copper selectively with reception of a deposit with the content of copper up to 70%. Weakness of the method is its efficiency basically in acid reduction, and also its low degree of copper extraction. On the basis of case hardening the method of galvanic coagulation is devised. It is based on the work of a short-circuited galvanic cell of iron-coke at variable contact of coupled metals components among themselves, cleared by the oxygen of air. The following processes of galvanic coagulation are considered: ? Extraction of copper; ? Formation ferrites of copper; ? Copper sorption on just-aggregated oxide forms of iron. Establishing conditions for passing the given stages provides an opportunity of copper extraction from technogenic water at any value of ??, content of salt and concentration of copper with reception of a compact deposit from which it is possible to extract copper by the known ways of enrichment and metallurgy. Investigations on optimization and intensification of galvanic coagulation with the purpose of reception the maximum rich deposit on copper have shown that the average contents of copper in a solution of 100~200 mg/dm3 the contents of copper in a deposit is 6%~10% at extraction 85%~90%, depending on characteristics of treated technogenic water. Using methods of scanning microscopy it is determined structures, composition and mechanism of phase formation in investigated electro-chemical process. The second stage of galvanic coagulation increases a degree of copper extraction up to 98%~99% that allows returning the cleared waters in circulation for waste recycling or evacuation in an open basin. Nowadays the method of galvanic coagulation is the most acceptable for copper extraction from technogenic water both from the point of view of efficiency and instrument setting that allows applying the method in conditions of the working enterprises.

Jan 1, 2014

By S. Gomez, P. A. Bebswa, A. N. Mwale

"The research aimed at improving the way screen performance analysis is conducted using a model that accounts for most feed and design parameters in its formulation. Thus, the aim was to validate the fine screen model that was developed at the Centre for Minerals Research (CMR) unit at the University of Cape Town. Fine wet screening is increasingly becoming an important application in fine grinding operations. Minera Saucito, a lead-zinc Mexican mine has replaced hydrocyclones with eight stacks of five decker derrick screens to close the ball mill in their concentrator plant. The five decker stacks have improved the overall plant throughput by 20% and have had the ball mill circulating load reduced considerably. As a continuous plant optimization process, a number of surveys were carried out to assess the performance of the 75 µm panel aperture installed screens. The surveys were conducted at seven different feed rates to the entire nest of screens to collect performance data. Using the fine screen model to analyze the results, it is found that as the feed rate increase, the sharpness of separation reduces. The CMR fine screen model was fitted to these results. The model fits the plant data with good accuracy. Simulated results based on this model are also presented.INTRODUCTION The potential of high frequency vibrating screens has long been identified as an alternative to hydrocyclones in grinding applications (Rogers and Brame, 1985). However, high frequency vibrating screens have had two main disadvantages, low capacity and high wear rates (Kelley and Mckeon, 2005; Teknikk, 2009). Current vibrating screen technology overcomes these challenges by multiple deck screen design and use of wear resistant urethane materials for panel construction (Kelley, 2007; Valine and Wennen, 2002). For a example, the Derrick screen’s material of construction is a tensionable urethane that provide high open area ranging between 35 to 45% with considerably reduced blinding (Valine and Wennen, 2002). Thus, there has been an increased uptake by the mining industry in the use of wet fine vibrating screens closing the ball mill as the final classification stage in the comminution circuit (Barkhuysen et al., 2010; Frausto, Ballantyne et al. 2017; Pelevin and Lazebnaya, 2009; Teknikk, 2009). Even though there is a number of models in existence, none of these models adequately predict the performance of high frequency vibrating screens (Karra, 1979; Rogers, 1982; Subasinghe et al., 1990; Trumic and Magdalinovic, 2011). Recently Mwale et al., (2016) developed a model for predicting the performance of high frequency vibrating screens using the partition curve properties. The input parameters of the model include screen open area (??) in m2, tonnage feed rate (????) (tph) and the weight fraction of solids (??) in the feed for a given panel aperture size. The model was developed based on data collected from a single deck industrial size derrick screen, in a pilot setup. The work presented in this paper is an attempt to test this model using data collected from Minera Saucito concentrator, an industrial plant whose comminution circuit is shown in Figure."

Jan 1, 2018

By Skinner. W.

"Introducing cutting-edge development work, which aims to simplify mineral processing flow-sheets, reduce costs and address environmental issues. Over the past four years Innovative Mineral Processing Technologies Pty. Ltd (IMPTEC) Australia have developed a Super-fine Crusher and a Planar Magnetic Separator which offer low cost, wet or dry alternatives to conventional grinding and conventional magnetic separation. Each of these machines has been successfully trialed at pilot scale and are now in the process of transitioning to commercial scale. This paper reports on the progress made in each of these fields. The potential scope for application of super-fine crushing technology as an alternative to grinding is potentially expansive and could include beneficiation of metalliferous ores, precious metal ore processing, hydrometallurgical processing, industrial minerals and coal processing, plastic fillers and ceramics processing as well as processing of cementitious slags and fly-ash. IMPTEC have recently achieved outstanding results at pilot scale with a dry combination of super-fine crushing and planar magnetic separation, which offers an alternative to the wet processing of magnetic iron ores. The dry combination has set new laboratory performance benchmarks when compared with the industry standard wet Davis Tube Tester. The test results have also established a strong evidence base showing that super-fine crushing achieves liberation of value minerals at coarser sizes when compared with grinding. The dry combination of super-fine crushing and planar magnetic separation also addresses environmental issues and completely eliminates grinding. An IMPTEC super-fine crusher is currently undergoing commercial trials, generating ultra-fine products from granulated lead blast furnace slag for use as cement substitutes. The performance of the super-fine crusher on this extreme duty highlights the potential benefits of super-fine crushing over the wide range of industries and applications where conventional grinding is employed.INTRODUCTION Present day mineral processing practices can become anchored in convention, where, inefficient methodologies are recognized and accepted as “best practice” or “industry standard”. Motivated by this challenge, IMPTEC has undertaken the development of radically different and improved methodologies in the fields of fine comminution and magnetic separation. Whilst, crushing is much less energy intensive and generally less capital and maintenance intensive than grinding, the technology has stalled due to the lack of crushing devices, which have the capacity to adapt to fine and ultra-fine duties. Grinding practice advances have been achieved through major increases in machine size and power. However, these advances are also accompanied by major escalations in capital, operating and maintenance costs. The economics of this strategy has become increasingly questionable. A typical example is the viability of low-grade magnetite beneficiation, which can hinge largely on the cost of grinding to fine and ultra-fine liberation sizes."

Jan 1, 2018

By T. S. Qiu

In view of the bad effect that Na-bentonite direct adsorb Pb2+-containing wastewater, this article has carried out two kinds modification treatment on Na-bentonite: the direct microwave radiation modification and microwave radiation organic modification by adding quaternary ammonium salt?cetyltrimethylammonium bromide,and analysis the main influencing factors of the modification effect. In static conditions, preparing Pb2+-containing wastewater as the research object, it has respectively studied the effects of Na-bentonite, microwave soil of direct microwave modification and microwave soil of organic modification on the process of adsorption Pb2+, and discusses the effects of pH value, temperature, adsorbent dosage, stirring time on the adsorption Pb2+ in wastewater by modified bentonite, at the same time it does a verification test to the practical Pb2+-containing wastewater. Comparison the effects of adsorption Pb2+ in wastewater, the results show that organic modified microwave bentonite is obviously better than direct microwave modified bentonite and Na-bentonite, and can make 6 mg/L Pb2+-containing wastewater meet the national discharge standards. Through scanning electron microscope, the result of test is that organic modified microwave bentonite is the cause of improving adsorption Pb2+ in wastewater. Preparing modified bentonite by microwave heating will not only shorten the response time, reduce energy consumption and work-load, but also modified effect is good.

Jan 1, 2014

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

"The solution for the treatment of the EAFD has not yet been fully achieved. Some of this dust has still not found an appropriate final destination. Large consortium treatment plants are quite expensive both in terms of investment and operating cost. Meanwhile, the tolling expenses for steel production companies are becoming very important, causing them to look for alternatives. Some steel plants are looking to close their production loop by internal treatment of their dust. Some years ago, Engitec began studying the coupling of the EZINEX® Process, an ammonium chloride electrolysis to recover the zinc contained in the EAFD, with the INDUTEC® Process, a pyro process based on an induction furnace that can convert EAFD into a C.Z.O. similar to the Waelz oxide. The combination of these two processes provides an alternative to the existing treatment options and is particularly interesting for relatively small capacities. In this paper, we would like to give the latest update about these two processes and their possible integration INTRODUCTION Zinc is contained in numerous wastes and secondary raw materials that can be thought of as high zinc concentrate mines. This is a very interesting source of Zn that is typically easily exploitable. Unfortunately, only a portion of these materials are currently processed to recover the metal value, while stabilized or unstabilized landfilling is often the final destination. Pyrometallurgical processes are mainly used to convert the zinc into crude zinc oxide (CZO). The various processes are very similar and characterized by the fact that the zinc bearing materials are usually submitted to a thermal treatment [1] in which the zinc is reduced, vaporized and re-oxidized producing CZO. This material not only contains zinc oxide, but also relatively high concentrations of heavy metals. Many potential CZO sources, such as electric arc furnace dust (EAF), galvanizing ashes, brass foundry and converters fumes also contain chlorides, fluorides and alkali metals that will transfer to the CZO. The classic example is the Waelz oxide [2]. This CZO is an intermediate product that must be transformed into zinc salts or zinc metal. Until now, the conversion to zinc metal is done through two main processes: the sulphate leaching and electrowinning system and the Imperial Smelting Process (ISP). ISP is facing a crisis for technical and economic reasons that has led to the closing of most of the existing plants. In any case, before being fed to one of these two processes, the CZO must be treated to eliminate or reduce some of the contained impurities. In particular, the halides are most harmful to these processes."

Jan 1, 2018

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

"The solution for the treatment of the EAFD has not yet been fully achieved. Some of this dust has still not found an appropriate final destination. Large consortium treatment plants are quite expensive both in terms of investment and operating cost. Meanwhile, the tolling expenses for steel production companies are becoming very important, causing them to look for alternatives. Some steel plants are looking to close their production loop by internal treatment of their dust. Some years ago, Engitec began studying the coupling of the EZINEX® Process, an ammonium chloride electrolysis to recover the zinc contained in the EAFD, with the INDUTEC® Process, a pyro process based on an induction furnace that can convert EAFD into a C.Z.O. similar to the Waelz oxide. The combination of these two processes provides an alternative to the existing treatment options and is particularly interesting for relatively small capacities. In this paper, we would like to give the latest update about these two processes and their possible integration INTRODUCTION Zinc is contained in numerous wastes and secondary raw materials that can be thought of as high zinc concentrate mines. This is a very interesting source of Zn that is typically easily exploitable. Unfortunately, only a portion of these materials are currently processed to recover the metal value, while stabilized or unstabilized landfilling is often the final destination. Pyrometallurgical processes are mainly used to convert the zinc into crude zinc oxide (CZO). The various processes are very similar and characterized by the fact that the zinc bearing materials are usually submitted to a thermal treatment [1] in which the zinc is reduced, vaporized and re-oxidized producing CZO. This material not only contains zinc oxide, but also relatively high concentrations of heavy metals. Many potential CZO sources, such as electric arc furnace dust (EAF), galvanizing ashes, brass foundry and converters fumes also contain chlorides, fluorides and alkali metals that will transfer to the CZO. The classic example is the Waelz oxide [2]. This CZO is an intermediate product that must be transformed into zinc salts or zinc metal. Until now, the conversion to zinc metal is done through two main processes: the sulphate leaching and electrowinning system and the Imperial Smelting Process (ISP). ISP is facing a crisis for technical and economic reasons that has led to the closing of most of the existing plants. In any case, before being fed to one of these two processes, the CZO must be treated to eliminate or reduce some of the contained impurities. In particular, the halides are most harmful to these processes."

Jan 1, 2018

By H. Z. Kuyumcu

Coking of coal blends using high volatile coals with poor coking abilities to produce a high quality coke for blast furnace application can be achieved by compacting the coal blend prior to the carbonization process. Here densification up to a relative material density of 80 %, i.e. a compact density around 1100 kg/m3, has proven to be advantageous. Coal is compacted by stamping, if the so-called stamp charging process applied. Compacting of the coal by pressing is practised in case of the cokemaking with so-called heat-recovery ovens. Stamped and pressed coal cakes require over the cake volume uniform high density and mechanical stability. Besides the aspects of the coal selection, the efficiency of the process is mainly determined by the operating parameters compacting time and compacting energy for coal cake making. At the Department for Mechanical Process Engineering & Solids Processing of the Technical University Berlin the two sub-processes of densification and strengthening during stamping and during pressing are theoretically and experimentally investigated using specially developed lab-scale compacting test units and a strength test device. Describing cake density in terms of coal properties for a given coal and measured compacting energy input then leads to a compacting equation with the so-called Stampability as the integral model parameter for the stamping process. For the pressing process the cake density can be calculated with the measured compacting pressure and the Compressibility factor, respectively. Investigations were carried out to provide evidence of a significant influence of coal type, coal surface moisture, coal granulometric and mechanical properties on the densification process. The overall objective of the work is to establish a comprehensive mathematical model on the compacting behavior of large coal bulk quantities and the optimization of the compacting processes by stamping and by pressing. Keywords: coal compacting, agglomeration, stamping, pressing, cokemaking

Sep 1, 2012

By A. A. Novoselov, U. Kelm

"Large volumes of mine tailings accumulated in surroundings of porphyry copper deposits represent a growing threat to environment. They contain significant concentrations of toxic metal and metalloids which can contaminate river runoff, ground waters or can be transported by wind. Both extreme pH of fluids in tailings impoundments and high surface areas of processed mineral grains provide their increased reactivity. As a result, during only a few decades, As, Cu, and Mo can be mobilized, redistributed through the tailing column and accumulated through post-deposition leaching, evaporation and contamination with natural fluids. Those processes are reflected in the forming of secondary minerals. Gypsum, Fe oxides/hydroxides, efflorescent salts and clay minerals are typical alteration products in tailings. Here we present the results of reactive transport simulations implemented on the base of PHREEQC and SUTRA codes. The one-dimension model emulates the mass balance between rainfall, evaporation and subsurface runoff, the kinetically- and thermodynamically-driven dissolution of tailing minerals, advective and diffusive transport of tailing fluids, and precipitation of secondary phases. A typical tailing column is composed of four unequal layers with predominance of (i) evaporation, (ii) secondary mineralization above, (iii) below water table, and (iv) near the bottom of dump. Those horizons are characterized by contrasting pH, chemical composition and bulk mineralization of pore fluids, distinct accessibility of atmospheric oxygen and, as a consequence, distinct intensity of sulfide oxidation. The modeling and its verification on Chilean tailings impoundments reveal the complexity and high rates of secondary mineralization. The accumulation of toxic alteration products is controlled by fluid transport through the tailing column induced by both rainfall/evaporation and exchange with subsurface runoff. The geochemical modeling is a powerful approach which allows comparing the processes in tailing deposits produced by distinct flotation regimes and providing the long-term predictions of their environmental impact as well as identifying sectors of tailings for possible re-processing."

Jan 1, 2018

By M. Mezzetti, E. Anders, O. Popov, P. Hoske, H. Lieberwirth, M. Voigt

"The material breakage induced by high energy electric discharges is known in general as electric impulse technology. This technology can be used for processing solid materials, such as rocks and ores. The electric impulse technology has been around for about 60 years, originally developed and intensively investigated by Russian researchers. However, the application fields have been limited to research and laboratory scale projects. Currently, there are new attempts to transfer this technology into practical industrial applications. Practical examples include drilling of deep geothermal wells with an electric impulse driven drill-head. Traditional comminution implies high energy consumption, hence, high costs. The Electric Impulse Technology is interesting for comminution of mineral and complex ores since it could allow improved recovery and energy reduction, thus resulting in significant savings. Another advantage is the dust free processing, which contributes to make minerals processing environmentally friendly. The use of electrical comminution for processing complex ores is investigated within the ELIZE research project funded by the BMBF (project No. 033R161 A) and industrial partners. The main objective is the development of an industrial scale electrical comminution machine. The first development stages include the investigation and characterization of the electric impulse induced weakening on rocks and ores. The characterization results of the preliminary trials at the microstructural scale on granite, skarn and greisen will be presented and discussed in this article. INTRODUCTION The pioneer work in the area of electric impulse technology was conducted by Russian researchers about 60 years ago [1]. While there have been some successful attempts to transfer this technology into practical applications, such as rock processing [2], laboratory processing of mineral ores [3–5], recycling [5] and geothermal drilling [6–9], the jump into practical industrial large scale application has not been accomplished yet. The Institute of Mineral Processing Machines of the TU Bergakademie Freiberg currently leads a project which can be seen as the next logical step for the technology transfer to industrial applications, namely, the development of continuously operating complex ore processing machines based on the electric impulse technology."

Jan 1, 2018

By Rodrigo Carvalho, Marcelo Tavares

"The accurate prediction of the outcomes in SAG grinding has been a great challenge to researchers and process operators. The use of Discrete Element Methods for modelling charge motion in tumbling mills allowed extraction of not only visual data, such as the position of the charge, but also the energy transfer in terms of the energy dissipated in the collisions. One of the advantages of DEM technique is its scalability to different mill sizes and some operational conditions such as speed and mill filling. Recently the Authors proposed the coupling between DEM outputs and modified Population Balance Models that with proper dedicated ore characterization tests allows the prediction of the outcomes of an energy transfer example. This modelling framework is called the Multi-scale Mechanistic Modelling. This paper shows the application of the Multi-scale Mechanistic Model to a set of pilot plant tests ran at different operational conditions. The prediction of the grinding outcomes and even the stabilization of the charge was achieved by the use of the Multi-scale Mechanistic Modelling framework. This approach has a great potential to become a powerful tool to design and optimize AG and SAG mills."

Jan 1, 2014

By J. Bouchard, Ali Vazirizadeh, R. del Villar

"The amount of water reporting to the concentrate correlates well with the solid entrainment. It is well known that the frother and collector dosage as well as the froth depth and gas rate influence the amount of water reporting to the concentrate. This is also true for gas dispersion properties such as gas holdup and bubble surface area flux. On the other hand, a positive bias rate, required to reduce hydraulic entrainment, also affects water recovery and thus the particle recovered by entrainment (depending on the their size). Up until now, the effect of the gas rate on the water recovery has been studied, but no comprehensive investigation on the gas holdup, bubble size and bubble surface area flux has yet been reported. This research precisely aims at addressing this issue. The experimental work was carried out under a constant gas flow rate to eliminate the gas volume effect, while other gas dispersion properties have been varied by modifying the frother concentration and the shearing water introduced to the frit-and-sleeve sparger. A constant froth depth and no wash water were used, in order to be able to evaluate the exclusive correlation between the water recovery and the bubble surface area flux and/or the bubble size. It is worth mentioning, that the particle size of the hydrophobic particles did not show a significant effect on the amount of water going to the concentrate. Not surprisingly, experimental results demonstrate that water recovery increases with the bubble surface area flux and with the gas hold-up."

Jan 1, 2014

By R. Shiva Kumar, G. Sreedhar, S. Sharma

Some of the Indian origin iron ore deposits located in Bellary, Karnataka province are having peculiar characteristics of Iron ore deposits (Hematite) having Iron above 64% and 30-40% lump (-30+6mm) recovery which are not suitable to use in blast furnace due to not meeting the specification of Tumbler Index and Abrasion Index. In general for high grade Iron ores, process flow sheet involves crushing and screening (dry/wet). In the contest of high grade Iron ores located at Bellary sector of Karnataka state in India, lump generated from this process could not attain the required physical properties (Tumbler Index, Abrasion Index) and metallurgical properties , even though the grade of the lump ore is above 64% Fe. Washing techniques like Drum scrubber and Log washer play major role in improving the metallurgical properties of Iron ore lumps by removing the light and hard layers of clay, silica coated over the lumps. In this study the effects were compared of drum scrubbing and log washing on iron ore lumps. It is found that by incorporating simple washing technique i.e. drum scrubbing or log washing, Tumbler Index of Iron ore Lumps could be increased from 74% to 78% which is acceptable for use in Blast furnace. From the Drum scrubber and Log washer tests, it is clear that Log washers have an edge over Drum scrubber in removing hard coated clay on surface of Lumps. This simple washing technique facilitate us to utilize the lumps directly in blast furnace and eliminate the unnecessary crushing and grinding of the ore so as to meet the specifications of Sinter fines and pellet feed.

Jan 1, 2014

By Trevor Saldanha, Stephen Grano

A key uncertainty in flotation modelling is determining, a priori, the proportion of each mineral which will develop a certain rate constant for different feeds of variable liberation and hydrophobicity. First and foremost is the ability to predict the proportion of minerals that will not be recovered, even at very long flotation times, and which therefore report to the tailing stream as the non-floatable fraction (i.e., having a zero rate constant). Recent empirical evidence has shown there are at least two factors which contribute to heterogeneity in flotation rates and, in particular, the appearance of a non-floatable fraction - heterogeneity in the distribution of adsorbed collector amount on a particle-by-particle basis, even for the same liberated mineral in the same size fraction, and the existence of a critical contact angle below which the bubble-particle union is unstable. In this paper, inferred measures of the critical contact angle for liberated particles are compared with stability model calculations. This has demonstrated that the dependency of the critical contact angle with particle size and mineral specific gravity are explicable by bubble-particle stability considerations. This argument is further extended to the flotation behaviour of composite particles, as a function of liberation class, in which the wetting perimeter of the attached bubble on the composite particle surface is constrained by the presence of a surrounding hydrophilic domain for the case of simple binary composites. Reasons for the different flotation behaviour of composite particles having different textures, as noted in the literature, are also discussed in terms of the stability of the bubble-particle union.

Jan 1, 2014

By C. Gomez, J. Finch, R. Dalhke, J. Torrealba-Vargas

"The dispersion of gas into bubbles is an essential feature of flotation machines. Three measurements have typically been used to describe the dispersion: superficial gas velocity (Jg), gas holdup and bubble size along with the derived quantity, bubble surface area flux. Measurement devices continue to be developed. The McGill Jg sensor based on accumulating bubbles by natural buoyancy comprises a tube with a valve and pressure transducer (Figure 1). The tube is immersed at a desired location and depth (H1) in a flotation cell. On closing the valve pressure increases to a maximum (P1) when the tube is full of air. The Jg is estimated from the slope of pressure-time curve (dP/dt).The relationship between Jg and dP/dt is derived from first principles. Testing the relationship is difficult in a flotation machine as the spatial variation in Jg is generally not known. This problem is overcome using a specially designed experimental setup and the estimated Jg is shown to equal the known Jg.The derivation reveals the importance of bulk density (?b). The sensor was modified to provide an estimate of ?b (Figure 2). A second tube was added immersed to a different depth (H2) and kept full of accumulated air giving a pressure P2. The estimate of ?b is given by (P1-P2)/(H1-H2) (i.e., at the end of collecting the pressure-time data). This two-tube sensor also helps dampen process noise as illustrated by a sudden change in level when collecting the pressure-time curve. Both the original and modified versions have been widely used in plant test work."

Jan 1, 2003