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By Diego Mesa, Willy Kracht

Frothers may be classified as weak or strong depending on their ability to produce stable froths, which is related to the amount of water that they transfer from the pulp to the froth. They can also have an effect on the non-selective mechanism of recovery by entrainment, implying that both selectivity and froth stability are, at least to some extent, frother dependent. Solids, on the other hand, also have an effect on froth behaviour. Clays, which are characterized by their small particle size, laminar shape, and high specific surface, tend to report to the froth phase and have an enormous impact on both froth stability and the overall performance of the flotation process. The purpose of this work is to shed light on the effect that different frothers have on the froth behaviour when clays are present. In order to do that, two sets of experiments were conducted using frothers from the families of alcohols and polyglycols. For each test, the equilibrium froth height was measured at different frother concentrations in an agitated machine with an acrylic square-base cell that was 11 cm wide and 25 cm high. The cell was designed in such a way that froth was able to grow without concentrate discharge. In the first set of tests, pure clays such as kaolinite and montmorillonite were used. In the second set, an actual copper sulphide ore with a high content of clays was used as solid phase. The results, expressed as curves of equilibrium froth height against frother dosage, showed a coupled effect of frother-clay on froth behaviour for both sets of experiments. In some cases, the froth grew up until the border of the cell with only a few parts per million of frother. In other cases, the equilibrium froth height varied smoothly with frother dosage. The results suggest that choosing the right frother can be of use for controlling the froth behaviour when dealing with clay-rich froths, using frother dosage as the control variable. The application of these findings at industrial scale are discussed and some recommendations are given.

Jan 1, 2018

By Ghislain Bournival, Seher Ata, Graeme J. Jameson

A common method to prevent bubbles from coalescing in a flotation cell is by the addition of surfactants, called frothers. The gas dispersion properties in a column were tested for solutions of 1-pentanol, tri(propylene glycol) methyl ether, and poly(propylene glycol) in the presence of sodium chloride. The dependency of surfactant on the gas holdup can be divided into regions. It seemed that for a sufficiently low concentration of surfactant, even a stronger surfactant could show a transition in gas holdup from constant/decreasing to increasing with concentration. This region, however, was not marked by a decrease in the average bubble size. In addition, PPG gave higher gas holdup values while averaging larger bubbles. On the other hand, sodium chloride mostly affected the gas holdup when the concentration was high enough to prevent bubble coalescence. Another parameter affecting the gas holdup was the superficial gas velocity. A linear dependency was found between the two under a bubbly flow regime. The current study showed that both surfactants and salt could slightly affect the influence of the superficial gas velocity on the gas holdup.

Jan 1, 2014

By Tamara Matveyeva, Tatiana Ivanova, Nadezhda Gromova

"The paper presents the results of study of the sorption and flotation properties of the reagents of plant origin - tannin and natural extracts of the oak bark and stems of plants, with a view to their application as a low-cost environmentally friendly modifiers of iron sulfide flotation for the recovery of minerals containing precious metals. The technique of preparation of plant extracts with a fixed content of extractable tannins has been developed.The mechanism of flotation reaction of tannin extracts has been identified as based on their adsorption on the surface of pyrrhotite and arsenopyrite to form strong complexes with iron (III) at concentrations below micelle concentration. It has been found that adsorption of plant extracts occurs without displacement of primarily adsorbed xanthate, and preliminary adsorption of xanthate did not preclude fixation of tannin on the mineral surface.It has been shown that plant extracts having hydrophilizing properties at low concentrations could be applied as selective depressants for pyrite, pyrrhotite and arsenopyrite in a weakly acidic, neutral or weakly alkaline medium. The use of plant modifiers could help to increase the quality of gold- and platinumcontaining concentrates and reduce the ecological impact on the environment."

Jan 1, 2014

By Sirish L. Shah

It is now common to have archival history of thousands of sensors sampled every second over long time. Yet we frequently have process engineers complain:??.We are drowning in data but starving for information??. How can these rich data sets be put to use? This paper addresses the issue of information and knowledge extraction from data with emphasis on process and performance monitoring including fault detection and isolation. Most of the major plant, factory, process, equipment and tool disruptions are avoidable, and yet preventable fault detection and diagnosis strategies are not the norm in most industries. It is not uncommon to see simple and preventable faults disrupt the operation of an entire integrated manufacturing facility. For example, faults such as malfunctioning sensors or actuators, inoperative alarm systems, poor controller tuning or configuration can render the most sophisticated control systems useless. Such disruptions can cost in the excess of $1 million per day and on the average they rob the plant of 7% of its annual capacity. Over the last decade the fields of multivariate statistics and data visualization and analysis methods have merged to develop powerful sensing and condition-based monitoring systems for predictive fault detection and diagnosis.These methods rely on the notion of sensor fusion whereby data from many sensors or units are combined with process information, such as physical connectivity of process units, to give a holistic picture of health of an integrated plant. Such methods are at a stage where these strategies are being implemented for off-line and on-line deployment. This article attempts to outline the field of sensor fusion - the application of signal processing methods, in the temporal as well as spectral domains, on a multitude and NOT singular sensor signals to detect incipient process abnormality before a catastrophic breakdown is likely to occur Keywords: Process analytics, process and performance monitoring, multivariate statistical analysis, sensor-fusion

Sep 1, 2012

By A. Norori-McCormac

"Air recovery, the fraction of air entering a flotation cell that overflows the cell lip, is linked to flotation performance, and it has been shown through industrial testwork that operating flotation cells at air rates that yield the Peak Air Recovery (PAR) results in high mineral recovery. For operating parameters over which flotation plants have little control, such as particle size, investigating the effect on the position of PAR, and the subsequent effect on flotation performance, proves more challenging. To this end, we have developed a bench scale flotation system that runs continuously and exhibits froth behavior similar to that found industrially, allowing the study of such parameters as particle size in addition to air rate. The bench scale system comprises a 4 l baffled cylindrical flotation cell, stirred by a Rushton impeller. The concentrate is recycled back into the pulp, allowing for continuous operation. Glass beads are used as solid particles, allowing a wide range of particle sizes to be tested, with TTAB as collector and MIBC as frother. The system allows operation at air rates typical of industrial flotation systems (1 -2 cms-1 superficial gas velocity), in addition to yielding a froth that coalesces and bursts and exhibits a peak in air recovery as cell air rate in increased. Solids and water recovery is also measured. The results show that air recovery is sensitive to changes in particle size. The intermediate size distribution showed a peak in air recovery (PAR) that corresponded with the maximum solids flowrate, as found industrially. It is shown that finer particles do result in more stable froths and higher recoveries, particularly at low air rates. The effect of particle size on the position of PAR is not yet unequivocally determined from these results."

Jan 1, 2014

By Yury V. Kulikov, Rakan Rahbani, Arkady Y. Senchenko

"The relevancy of complex minerals treatment is constantly increasing taking into account mineral resources depletion. Different refractory ores and concentrates, oxidized and polymetallic ores, as well as metallurgical products (slags) can be assigned to such mineral type. The treatment of such products via conventional flowsheets requires considerable capital and operational costs and does not always provide high recovery level of valuable components into a saleable product. Therefore, considerable amount of ores and metallurgical products are not treated, or treated inefficiently. One of the most promising approaches that allows economic treatment of refractory products is their ultrafine grinding down to 5-20 µm with subsequent processing or hydrometallurgy. Horizontal bead mills - the IsaMillTM, developed by Xstrata Technology, received their wide application in mining industry. Standard testing is performed under laboratory conditions in an M4 IsaMillTM (volume - 4 liters) to define the parameters of fine grinding. This mill completely simulates the operation of full scale industrial mills up to 50 m3 in volume (up to 8000 kW motor). The paper describes fine grinding technology performed in bead mills, and the importance of testing according to a certified method for industrial equipment selection. The paper contains description of promising directions of fine grinding technology application for several projects in Russia and Kazakhstan."

Jan 1, 2014

By S. K. Chaurasiya

o meet the ever increasing demand of iron oxide feed stock for rapidly growing domestic steel industries and to effectively manage the depleting reserve of high grade lumpy iron ore, Pelletization of iron ore fines/slimes are expected to play a dominant role in the near future. Use of pellets will also enable the blast furnace operator to achieve higher levels of productivity with lowering of operating cost. The effective utilization of Iron Ore Slimes is important not only from the point of view of optimum utilization of Iron values in the mined ore but also for preventing environmental pollution. A significant amount of slime is being accumulated at the tailing dam of one of the iron ore mines and with the present scale of operation the tailing dam will be filled in another 10 years. Hence to increase the life of tailing dam and for better utilization of the iron values a study has been carried out for the suitability of pellet manufacturing with slimes and fines at our laboratory. The pelletization studies are aimed for optimization of various parameters for production of Blast furnace/ DR grade pellets from beneficiated slimes and Fines. This paper attempts to describe the production of blast furnace grade pellets from beneficiated slime and fines and its characterizations.

Sep 1, 2012

By G. Mucsi

This paper deals with the laboratory investigation of cathode ray tube (CRT) glass based glass foam, a relatively new product so called ?Geofil bubbles?. The main process engineering material properties of raw materials, such as particle size distribution, moisture content, density and specific surface area are shown. Then the preparation of raw cathode ray tube glass waste is presented including the following steps: crushing in impact crusher, grinding in laboratory scale ball mill, mixing, pelleting and sintering. We found that it was possible to produce foam glass (with proper mechanical stability and particle density) from the investigated waste CRT glass. The material characteristics of the final product strongly depend on the sintering conditions. Optimum conditions were determined particle size fraction was found to be 4-6 mm, temperature 800 0C, residence time 7.5 min. Keywords: waste CRT glass, grinding, pelleting, sintering, glass foam

Sep 1, 2012

By Girolamo Belardi, Silvia Serranti, Giuseppe Bonifazi, Roberta Palmieri

Ore textural and structural characterizations play a fundamental role in any preliminary study (i.e. comminution, classification, separation) addressed to the design and set up of beneficiation flow sheets. The possibility to utilise automatic tools able to perform a classification, and a quantitative description, of the mineralogical and petrographical characteristics of raw ore samples thus represents an important step to define, to control and to verify the entire set of parameters, ore-texture-related, that can affect the final beneficiation results. The procedure usually adopted is based on the analysis of polished sections and more in details the recognition of the different mineralogical species and associations and the measurements of some quantitative parameters estimating both the geometrical characteristics of each species and the possible spatial relationships between them. This approach, originally carried out by experts, utilising optical and/or electronic microscopy, was ‚replaced? during the years by more and more sophisticated devices integrating analytical facilities and acquired data processing. Such integrated analytical devices formed the breakthrough platforms into what is now known as modern Process Mineralogy. In this paper the possibilities offered by chemical imaging based devices and techniques, to perform ore minerals recognition/classification, and to perform their topological assessment, are presented. Tests have been carried out and are discussed in order to analyze the problems related to the development of suitable and low cost strategies addressed: i) to realize a full mapping of ore minerals/gangue inside selected samples, ii) to define the optimal data-flow handling to optimize the speed of processing versus the quality of the results and iii) to start to define logics and procedures finalized to implement innovative smart detection engines, chemical imaging based, for mineral processing addressed to perform both a preliminary characterization of the ore, at laboratory scale, and a further possible control of the different processed minerals flow streams.

Jan 1, 2014

By Daniel Saramak

"Issues concerning effectiveness of the high-pressure comminution process in technological circuits of copper ore treatment were presented in the paper. Crushing processes taking place in high-pressure grinding rolls devices (HPGR) are currently one of the most efficient methods of hard ore size reduction in terms of the energy consumption. The HPGR products are characterized by a fine particle size and the micro-cracks formation in individual particles, which appear in downstream grinding processes, decreasing their energy consumption. The purpose of this paper was to analyse the effectiveness of a ball mill grinding process depending on the changeable conditions of run for the HPGR crushing process. The research programme carried out included crushing tests in the laboratory scale HPGR device at various settings of the operating pressure volume and selected qualitative properties of the feed material (i.e. particle size distribution). Particle size distribution analyses of all HPGR products were performed and in the next stage the material was a feed to the ball mill grinding process. Grinding process kinetics were investigated through the determination of mass recoveries of individual particle size fractions after defined grinding time intervals. The models, defining the grinding process effectiveness as a function of changeable conditions of HPGR process run, were determined on the basis of obtained results. Based on these models the optimal grinding time in a ball mill was specified which is, in turn, the basis for optimization of operation of the technological comminution circuits for a given material type. The obtained results proved that the application of HPGR devices in a given copper ore comminution circuit may improve the effectiveness of the downstream grinding process which leads to improvement of the entire circuit work efficiency through decreasing the process energy consumption and enhancing product size reduction."

Jan 1, 2014

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

"Silver is currently lost as jarosite during the pressure oxidation of sulphides and cyanidation of the residues yields 5-10% of silver. Efforts to recover silver from complex sulphides, which contain economic fractions of silver require an understanding of the behaviour of acanthite during pressure oxidation. However, previous studies of acanthite (Ag2S) reaction have been complicated by the formation of argento-jarosite and uncertainties arise on the interpretation of the results.In this work, the acid pressure oxidation of high-grade natural silver sulphide mineral (acanthite) was carried out at 110-150°C and under the conditions similar to that of pressure oxidation of complex sulphide. The predominant product of reaction is elemental sulphur. The rate of reaction increases with increasing temperature and with the presence of ferric ions. The kinetics is controlled by chemical reaction with activation energy of 72.6 kJ/mol. The rate of reaction decreases with the presence of silver sulphate in the initial slurry. The proposed overall reaction is close to: []"

Jan 1, 2003

By A. D. Ramirez, L. E. Gutierrez, M. A. Garces

"Scarcity of freshwater in mining operations in arid zones in different parts of the world has led to the mining companies to think about using seawater as an alternative source in mineral processing operations. Examples of this situation are Minera Centinela (AMSA) and Minera Sierra Gorda (KGHM), both plants located in northern Chile. Previous studies showed that molybdenite flotation is depressed at high pH values in seawater as a result of the action of hydroxy-complexes of magnesium and calcium that attach to the faces of the molybdenite particles, reducing its hydrophobicity and as a result flotation recovery. In this work, a study of the interactions between molybdenite and kaolinite is presented. The effect of sodium hexametaphosphate (SHMP) dispersant on the recovery of molybdenite in the presence of kaolinite is studied in different aqueous media and it is correlated with induction time data. The results allow to conclude that kaolinite has a stronger depressing effect on molybdenite in seawater compared to its effect in freshwater. Magnesium and calcium are the cations that have the strongest effect in enhancing the interactions between molybdenite and kaolinite. SHMP reduces the negative effect of kaolinite on the floatability of molybdenite both in seawater and freshwater. The induction time data correlate well with the micro-flotation results.INTRODUCTION The need for water in mining processes in arid and semi-arid zones has led to the search for new alternatives for this resource, among which seawater has gained an important space. In Chile, most of the mining operations are located in the northern part of the country, an area that has limited availability of freshwater for the processing of copper and molybdenum sulfides (Castro and Laskowski, 2011, Castro et al., 2012 a). Seawater is an aqueous solution with high concentrations of ions such as Na+, K+, Mg2+, Ca2+, So42-, Cl-, and other less concentrated species which generate important effects in the flotation process as they modify the properties of the solid/liquid, and liquid/gas interfaces, and also increase the consumption of some important reagents used to depress pyrite such as lime. It has also been proposed that flotation of copper sulfides is negatively affected in seawater because of the reduction of oxygen solubility compared to freshwater (Millero et al., 2002; Duan and Sun, 2003). In contrast, it has been shown that the presence of ions in solution in the process of flotation of natural hydrophobic resources improve recovery as result of the compression of the electric double layer (Laskowski, 1974; Klassen and Mokrousov, 1963, Laskowski and Castro, 2008."

Jan 1, 2018

By Ruiyang Zhang, Ping Fang, Dezhou Wei, Shuling Gao

A CFD based numerical simulation of flow characteristics of hydrocyclone was conducted with different structural and operational parameters to investigate its distribution characteristics and influencing mechanism. The results show there exist several unsymmetrical envelopes of equal vertical velocities among both upward inner flows and downward outer flows in the hydrocyclone, and cone angle and apex diameter have remarkable influence on the vertical location of the cone bottom of the envelop of zero vertical velocity. It is also found that some tangential velocity isolines exist in the horizontal planes located in the effective separation region of hydrocyclone, and feed pressure has almost no effect on the distribution characteristics of both vertical velocity and tangential velocity of flow in hydrocyclone, however the magnitude and gradient of tangential velocity are made increased obviously, so as to make the high density particles motion velocity to the wall increased and to make the cyclonic separation effect improved. The simulation results also show when the apex diameter increased, the pressure of the fluid field decreased, however the pressure grads in the apex district increased, and the degree of changing is different as the cone angle, which showed some interactive influence of cone angle and apex diameter on the fluid field of hydrocyclone. While the feed pressure also has almost no effect on the pressure distribution characteristics, however the its magnitude and gradient are made increased accordingly, which can improve the separation accuracy according to particle density.

Jan 1, 2014

By V. A. Zhilina, I. V. Shadrunova, O. E. Gorlova

"The aim of the study is to develop and scientifically justify a new adaptive approach to the separating processes of deep and complex processing technogenic mineral raw materials. Technogenic mineral resources as a waste of mining and processing industry are mostly complex objects that have specific features of material composition and technological properties and make it processing ineffective with traditional schemes of mineral raw materials enrichment. Mineral wastes are regarded in this study as a complex object with a large number of signs in conditions of uncertain environment and object. However, adaptation is regarded as the process management system’ adaptation to the specific the properties of the object and the environment that has several hierarchical levels corresponding to different stages in the management of complex object. An adaptive approach is considered as a methodological basis of multivariate schemes for opening the mineral resources and creating mechanisms that could transfer these potential technogenic resources to the actual that significantly expand the mineral resource base of the country's black, coloured, rare, noble metals and construction materials. In this case, potentially the solution to the most pressing social and environmental problems associated with the adverse effects of past economic activity simultaneously with the commercial objectives. This approach to the wastes mining and related processing manufacturers meets the core idea of sustainable development as the balance of interests of State, society, business, private enterprise and each person in the areas of rational use of resources, economic efficiency and environmental safety. On the example of metal-containing raw materials in the form of slags of ferrous and nonferrous metallurgy, ferrous metallurgy sludge, mature fine tailings, the application of adaptive approach illustrates to the development of technologies of its deep and complex processing as phased, thoughtful movement from a comprehensive study of technogenic raw materials to build optimal topologies of technological schemes for processing the mineral wastes. INTRODUCTION Involving the Russian economy in the system of global economic relations significantly changes the nature of the country's competitiveness in the development of the world market and urgently requires competent management of its own natural and mineral resources. The latter at the present time in real economic processes cease to be a passive material foundation and become the producing basis in the production processes in the status of so-called natural capital. Introduced in the field of economic theory at the end of the 20th century, this term means both the flow of natural services and real natural resources. Consequently, natural objects, which act as natural resources of a certain production, today must necessarily be evaluated in a strategic sense. Modern standards of sustainable development presuppose that the economy should equally be oriented to balance the interests of the state, society, business, individual enterprise and each person in the spheres of rational use of resources, preservation of healthy ecosystems, ensuring well-being, high quality of life and environmental safety of not only the current generation, but also respect for the rights of future generations, that is, intergenerational equality. Most types of minerals are classified as non-renewable resources, therefore resource-saving in the sphere of mineral and raw materials complexes is one of the most important factors-indicators characterizing the degree of approximation to the model of rational subsoil use, and, consequently, sustainable development (State Report, 2017)."

Jan 1, 2018

By Silvia França, Hudson Couto, Renata Barbosa

"The flotation process, largely used for mineral concentration processes, which is based on air bubble adhesion to the dispersed solid phase, is also being used for wastewater treatment purposes. Dissolved air flotation (DAF) is based on the separation of the solid-liquid phases with the aid of small air bubbles (10-100 µm), with high values of interfacial contact area, improving the process efficiency. In the process, the air bubbles and particles or flocs form aggregates, which rise to the surface of the flotation cell to be collected. The advantage of producing small bubbles is directly related to the fact that smaller bubbles result in greater bubble-particle interaction. Wastewater produced in alumina refinery - from the red mud filtration step - has a red colored aspect due to the presence of very fine particles of red mud and also dissolved matter that still remain in the filtrate. This wastewater might be treated, aiming to reuse the water in the refinery or discharge it properly in the environment. The aim of this study was to evaluate the DAF process efficiency for the treatment of red mud wastewater in order to decrease suspended particles and dissolved solids contents, in addition to mitigate the high causticity of this wastewater. The process efficiency was evaluated by comparing turbidity removal and total solids concentration in the treated wastewater to the feed. The influence of important variables of the DAF process as type and concentration of coagulant and flocculant were evaluated. It was possible to obtain good turbidity removal efficiencies (up to 90%) using low concentrations of coagulant (50 mg/L) and flocculant (0.5 -1.0 mg/L). In addition, for most of the experiments, the specification for effluent diposal, according to the Brazilian environmental regulation 430 (Conama, 2011): pH range 5 to 9 and turbidity < 40 NTU, was attained. These results emphasize the possibility of using the DAF as an alternative technique to settling and filtration process, that are traditionally used, for treating wastewater from the alumina industry, allowing the reuse of water in the plant or adequate discharge with less environmental impact."

Jan 1, 2014

By T. N. Matveeva, T. A. Ivanova

"The article presents the results of the research aimed at development and testing of new effective reagents – collectors and green modifiers for more complete extraction of gold and platinum to concentrates at reduced loss with waste products. The main deposits of Au and PGM ores of Russia and abroad are presented by refractory raw material with the non-uniform finely-interspersed sulfide mineralization, submicron gold and platinum, the low metal content, non-uniform distribution of valuable minerals. and show low indicators of recovery. The main losses of precious metals (up to 15 %) at flotation are associated with thin slam tailings because of inefficiency of standard reagent modes.In the paper, the new trends in design of collecting agents for extraction of gold and PGM sulfide minerals and their application in flotation tests are substantiated. The original technique for obtaining the modified collector reagents – dithiocarbamate, dithiophoshpinate and dithiazine, incorporated non-ionic compounds that are able to generate stable complexes with gold and platinum has been developed. A novel class of collectors – cloud point polymers showed high flotation recovery of fine particles of gold and platinum. The original technique to create the mineral samples of natural sulfides with ""invisible"" or sub-micron gold on their surface designed helped to indicate the mechanism of selective adsorption of novel agents on Au and Pt-sulfide minerals. Extractive UV spectrophotometry, potential measurements, X-ray phase and spectral analysis, scanning electronic microscopy (SEAM), laser SIM and AFM microscopy were applied to analyze the adsorbed layer of modified reagents on the mineral surface. Selective hydrophobic covering on the surface of micro- and nanoparticles of noble metals provided an increase in their extraction during flotation. New reagent modes of modified collectors and green modifiers were tested in scaled-up laboratory flotation and the results obtained demonstrated the increased quality of the concentrates in terms of gold content by 1.5 times and higher gold recovery by 1.5-5%. The studies have been supported by Grants of the President of RF “Scientific School of Academician Chanturiya” NSh-220.2012.5; NSh-748.2014.5."

Jan 1, 2018

By Mario Gerards, Sergej Podkow, Marco Steinberg

"The JONES® WHIMS technology is based on the magnetic separation process and is widely used for the recovery of magnetically susceptible iron ore particles. The conventional machine design is well-known within the iron ore beneficiation industry for more than 50 years and recognized to be highly reliable, robust and extremely compact with the advantages of high capacity and selectivity. In 1981 Rana Gruber AS, Norway bought 14 JONES® WHIMS DP 317 separators when the magnetic separation plant was built and erected. Today, 11 of these old machines are still operating profitably and efficiently. The former supplier was the coal and minerals division of Klöckner-Humboldt-Deutz (KHD) which is today MBE Coal & Minerals Technology GmbH (MBE). This paper outlines a detailed description of the project of revamping the above mentioned old machines and describes the challenge of incorporating enhanced and newly developed technology into an existing processing plant. Further it gives an overview of the recent developments on the design of the JONES® WHIMS. In order to meet modern product requirements and to increase and secure plant productivity, in 2012 Rana Gruber AS settled a contract covering two new designed JONES® WHIMS DP 317 HFR separators to be implemented into the existing building and the upgrading of all 11 older JONES® WHIMS under the use of as many refurbished items as possible. The two new machines were fully developed by the product specialists of the supplier in cooperation with the operator Rana Gruber AS, thereby taking advantage of their great experience. The design of the new machine is based on the conventional design, i.e. the general operating mode as well as the overall dimensions are identical. Finally this paper gives an overview about the erection and commission phase of the two new machines and gives a detailed comparison between conventional and enhanced WHIMS technology."

Jan 1, 2014

By Wang Xu, Tao Dongping, Zhang Jie, Tao Youjun

Based on the principle of fly ash triboelectrification, the mineral electrical index and testing method are introduced. The electric differences of various mineral components of fly ash are discussed in view of the results of chemical and mineral composition analysis of the fly ash sample acquired from the Xin-wen power plant. The dielectric constant and charge-mass ratio of carbon and ash in the fly ash are determined. The data were then used along with the rotary triboelectrostatic separator (RTS) testing results to investigate the charging characteristic of fly ash particles in different sizes. The results show that the dielectric constant of fly ash with different particle size decreased with the decrease in particle size, which led to a poor electrical conductivity. Thus particle size has an important effect on conductivity. The charges of carbon and ash particles increased with decreasing particle size. The charge-mass ratio of carbon and ash particles of the same size increased with decreasing particle size. This indicates that finer particle size is more favorable for triboelectrification separation from the charging efficiency point of view. The rotary triboelectrostatic fly ash separation tests show that the best decarbonization performance was achieved with particles in the size range of 0.038-0.074mm with which the decarbonization rate and efficiency index reached 38.93% and 120.83% spectively.

Jan 1, 2014

"This research represents a shift away from empirical models that lock the industry into 50-year old inefficiencies with little response to operating variability. The mechanistic and intrinsically dynamic mill model under development steps up to a new paradigm using the latest computing capabilities and physical understanding of breakage and transport to transform predictive capabilities for design, optimisation and on-line control with variable feed. The milling process is broken down into discrete sub-processes, each of which can be modelled as an object in the whole model and in the model code. These objects can be upgraded or exchanged without having to rewrite or restructure the remainder of the code. Sub-processes include: feed into mill; transport along mill; presentation to impacting events; range of impacting forces; probability of being impacted in different zones in the mill as a function of particle size and density; suspension in slurry; and discharge out of the mill. The unit and processes surrounding the mill (feed and recycle conveyors, slurry pump and pipe, cyclone and recycle crusher) have also been modelled, in order to incorporate the effect of recirculating load coming from a cyclone or a recycle pebble crusher, respectively for ball mills or SAG mills. Each unit is modelled dynamically and PID controllers have been added to control pumping flowrate from sump and water addition for cyclone feed dilution. The paper demonstrates the predictive capability of a dynamic, mechanistic model and is used to test the sensitivity to the sub-processes, comparing different formulations and highlighting the aspects that require further development. Validation on pilot tests and application to industrial data is presented. This approach is currently undergoing industrial trial on sites, for use in on-line model-informed process control. Considerable further development is required to incorporate the full mechanistic structure planned for this model."

Jan 1, 2018

By Markus A. Reuter, Jacques J. Eksteen

The modelling of bath type furnaces tends to be either fundamental in nature or total empirical "black box models". While models of the first kind are robust, they tend to lack accuracy, in cases where they are to be used for process control, and may take an overly long in development time. On the other hand, black box models tend to lack robustness of prediction for all circumstances and tend to be limited to interpolate based on historical data. While this may very often provide short-term accuracy, the models may have problems with stability in the long term. Moreover, the model structure may not reflect any of the fundamental properties of the system and remains opaque to fundamental analysis. The aim of the model development is in obtaining a model that have robustness, high accuracy, a short development time and which is adaptive to a changing environment. The models are specifically developed for on-line decision support or control of furnaces. The modelling approach is evaluated for a chromite bath smelting furnace. The role of systems analysis, mass balance smoothing, thermodynamic analysis are integrated into one generic algorithm for bath type furnaces. Therefore, this paper argues that to understand complex metallurgical furnaces a hybrid approach is the only method to fully grasp the intricacies of metallurgy, to improve operations, economics as well as environmental performance.

Jan 1, 2003