Search Documents

By B. McFadzean, P. E. Ngoepe, P. P. Mkhonto

"The theoretical technique of computational modeling and the experimental determination of the enthalpy of adsorption of a ligand molecule onto a mineral surface deliver the same output parameters and, therefore, complement each other in investigating the affinity of different ligand types for mineral surfaces.This study ran parallel experimental tests and computational calculations to determine the enthalpy of adsorption of a series of increasing chain length xanthates onto a pyrite surface. The outcomes showed that, while the absolute energy values were different, the trends were similar. Both computational and experimental approaches showed that the extent of the interaction of the xanthate molecule increases with increasing carbon chain length. The computational values were larger than the experimental values, which could be explained, in part, by the addition of water to the computational system, which resulted in a decrease in the heat of adsorption on the (100) surface, compared to the adsorption of the collector in a vacuum. The computational method showed that, in the case of the pyrite (100) surface, the most exothermic reaction was obtained when the two xanthate sulfur atoms bridged two pyrite 5-coordinated iron atoms. The (111) surface was found to be more reactive and different adsorption mechanisms were predicted for each of the C2, C3, C4 and C5 chain length xanthates.The experimentally determined exothermic increase in heat of adsorption for the addition of each CH2 group was found to be -8.17 kJ/mol. The contribution of the thiol head group was -34.9 kJ/mol. Previous studies on self-assembled monolayers have shown that these values are compatible with lateral interactions between CH2 groups and the exclusion of water. This study provides a rigorous experimental and computational approach which is intended to afford confidence in modelled data for the screening of new ligands for flotation processes.INTRODUCTIONComputational modelling is a fast and cost-effective method of screening collector molecules for the efficacy of their adsorption onto mineral surfaces. However, it is desirable to measure the computational outputs against experimental outputs to check for congruency. Computational modelling and experimental microcalorimetry both deliver the same output parameter: the energy of adsorption of the molecule onto the solid surface. These techniques are therefore ideally suited to complement one another in investigating the affinity of the interaction between collector molecules and mineral surfaces."

Jan 1, 2018

By Fengnian Shi

In the current energy-sensitive world, sustainable development in the mineral industry will require new, better and more efficient processes. Novel comminution methods, which offer the prospect of achieving the required outcomes of size reduction and mineral liberation at lower energy consumption, are continually being sought. In the past five years, extensive research using high voltage pulse electrical comminution technology has been carried out at the Julius Kruttschnitt Mineral Research Centre (JKMRC), in collaboration with selFrag AG. The major outcome of this research is the development of the concept of pre-weakening ore particles by electrical comminution procedures to reduce the energy consumption in the downstream grinding circuit. The research has also verified the preferential liberation of valuable minerals by electrical comminution. Given the advantages, several potential applications of electrical comminution in the mineral industry are proposed, including AG/SAG mill feed pre-weakening, pebble treatment, ball mill feed pre-weakening, early recovery of the liberated valuable minerals, crack/micro crack generation for improved leaching, and smelter slag treatment. For the mineral industry to utilize electrical comminution, two emerging issues identified from the research need to be address. They are the energy consumption by electrical comminution in the locked cycle treatment and the facilities scale up necessary to move this technology from the laboratory to the plant. Keywords: high voltage pulses, electrical comminution, energy efficiency, mineral liberation

Sep 1, 2012

By M. Mirnezami

Pentlandite samples were obtained as Ni concentrate from three Canadian plants and one specimen sample from Ward?s Scientific Establishment. The samples were upgraded using gravity and magnetic separation techniques. Nickel concentration was determined by atomic absorption spectroscopy. Microprobe analysis identified a range in Co and Cu lattice substitutions. All samples exhibited similar zeta potential-pH trend with isoelectric points from 2 to 3, and similar responses to copper activation and addition of xanthate. The similar trends indicate that the variations in lattice substitution identified have no significant effect on electrokinetic properties; that is, samples from any source likely yield results that can be generalized.

Sep 1, 2012

By Thenepalli Thriveni, Seong-Young Nam, Nam-Il Um, Joobeom Seo

In the present work, we report a novel microstructure of synthesized scalenohedral PCC (precipitated calcium carbonate) without any additives by a simple and ecofriendly carbonation process carried out in a liquid-gas system on the crystal growth of the scalenohedral calcite phase. Especially, the process parameters of Ca(OH)2 concentration and CO2 flow rates were investigated to enhance the sensitivity of the process. The highest average length of the scalenohedral calcite was obtained at pH 6.0, temperature 450C, Ca(OH)2 concentration 0.2M, CO2 flow rate 80mL/min, and total volume 1L. The utilization of flue gas-derived CO2 from coal fired power plants could be a form of carbon capture and storage using carbonation reaction with scalenohedral PCC. Finally, the synthesized scalenohedral PCC was used as a filer for ONP recycling. We demonstrated all these experiemnts at semi pilot plant scale.

Jan 1, 2014

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 Lj. D. Andric

Development of modern devices for mechanical and mechanochemical materials activation has been dated since the beginning of last century. Rapid development of high-energy mills that are different in type, size, design and performances, has been occurred during the last four decades. Because of complete understanding of mechanical processing, entire knowledge of theoretical principles of high-energy mills is necessary. These principles are main causales of process that are happened in materials during the mechanical activation. This paper is occupied by theoretical principles of operation of high-energy mills. Conventional high energy mills with balls, high-energy planetary mills and high-energy vibrational mills are particularly considered in the paper.

Jan 1, 2014

By K. S. McClure, S. B. Chitralekha, R. B. Gopaluni, Chmylek. T., S. L. Shah

This is a tutorial paper on industrially successful approaches for nonlinear process monitoring. Online process monitoring is essential to continuous operation of plants at high efficiency. The problem of process monitoring is one where an impending but undesirable process condition has to be identified and used to alert process engineers. This problem has traditionally been solved by practicing engineers using statistical techniques that detect a change in the underlying correlation structure of process variables. For linear correlation structures, algorithms such as principal components analysis, independent component analysis and partial least squares have been proposed. However, many industrial processes exhibit nonlinear correlation structure between the process variables. In this tutorial we describe various nonlinear monitoring techniques and elaborate on two recently developed methods, namely Support Vector Machine and Local Linear Embedding. The two methods are evaluated by application on two experimental case studies, a SAG mill and a polymer extruder.

Jan 1, 2014

By B. Rath

An effective process plan is an important part of maintaining consistent recoveries in mineral processing operations. Traditionally, Mineralogical studies are completed using chemical and metallurgical methods to monitor recovery and elemental distribution. The development of mineralogy and more efficient processes in mineral analysis techniques means that mineralogy is now more accessible as an efficient and comprehensive study tool. As operating costs increase and feed grades decrease it is important to maintain tight control of process and ensured maximum recovery is maintained at all times. Just a few days of losses in recovery caused by changes in ore type or processing conditions can have a large effect on total metal recovery and profit. Mineralogical audits can be used to minimize these losses by monitoring the fundamental behavior of feed ore on a regular basis. Smart use of mineralogical studies can develop mineralogical and ore type benchmarks in a detailed, which can be used in process control and monitoring. Geological ore types can be used to identify key mineralogical parameters that may be used in routine and cost effective analysis. Mineralogical systems ideally suited to this because of the depth of information on everything from modal mineralogy to locking/liberation characteristics and mineral associations. Mineralogical studies can equally be applied to specific unit operations within the process, which can allow more detailed information to be gathered on areas of the process that have been identified as critical. This will be especially effective for flotation or oxidation processes where process parameters can be very sensitive to small changes in mineralogy. This paper deals with the Ore Morphology, Ore Mineralogy, Gangue mineralogy, Photo micrographs under reflected, transmitted light and XRD studies Ore, Mineral studies of Sub grade Iron ore of Bacheli Complex, Bailadila Sector, India. Keywords: mineralogy, liberation, liberation studies, ore mineral, gangue mineral, morphology, jasper, ferruginous clay

Sep 1, 2012

Geopolymers are novel engineering materials with the potential to play a highly significant role in the transformation of the construction materials and building products industry in the push to-wards sustainable development. These materials are formed by activation of industrial aluminosilicate waste materials such as coal ash or blast furnace slag with alkaline solutions. Some mineral waste can also be used, either as fillers or as reactive components. The use of waste-based geopolymers results in significant (up to 90%) reduction in carbon dioxide emissions when used in cement replacement applications. In addition to the formation of conventional pre-cast products, these high performance mineral binders are ideally suited to use in the conversion or encapsulation of toxic waste, including radioactive waste, due to their chemical stability and resistance to acid attack. It is the aim of this paper to review recent developments on the science underpinning this ?green? technology, and to discuss the technical and commercial drivers governing the large-scale adoption of the technology. Some of the recent fundamental breakthroughs in the study of geopolymer technology at the University of Melbourne will be presented. Despite the complexity of this reactive sol-id-gel system, progress has been made in the development of a thermochemical reaction kinetic model that has been validated using both calorimetric data and synchrotron kinetic data. Geopolymerization is potentially a disruptive technology, so that it is normal to expect strong resistance from established companies in the construction materials industry. It is increasingly necessary that waste generating industries such as mining collaborate with industries such as construction that could utilize this waste. The world?s first full scale geopolymer plant utilizing waste and re-cycled material has been commissioned recently in Melbourne, Australia, so progress on commercialization will also be presented. The authors frequently present keynote lectures on geopolymer science and technology at materials science, ceramics and construction materials conferences. However, this interdisciplinary technology that is still in its infancy, deserves more attention in the mineral processing and mining industry in view of its potential use in the mining industry, and also in view of the importance of mineral processing techniques in recent advances in geopolymers.

Jan 1, 2014

By C. Dorfling

Experimental work was performed using a bench scale autoclave to evaluate the effects that leaching temperature, pressure, initial acid concentration, and the solid to liquid ratio have on the behaviour of base metals and platinum group metals in a high-pressure sulphuric acid oxygen leaching system. The concentrations of metals in the leach solution were measured over time at different leaching conditions. At the conditions investigated, the initial acid concentration had the largest influence on the copper leaching kinetics, while the leaching rates of the other precious metals (OPMs: rhodium, ruthenium, and iridium) were highly dependent on the leaching temperature. A set of chemical reactions that can be used to describe the leaching chemistry was proposed, and the associated reaction kinetics were quantified. As a first estimation, the rate expressions were considered first order, and the rate constants were determined using the method of least squares, considering the experimental and predicted concentrations obtained for the different leaching conditions. Of the OPM compounds, the sulphides showed the fastest dissolution rate, followed by OPM alloys, and finally the OPM oxides. During the initial leaching stages, base metals and OPMs competed for the available dissolved oxygen, with oxygen being preferentially used for copper leaching. Precipitation of OPMs during the initial leaching stages can be ascribed to copper and nickel dissolution according to exchange reactions between dissolved OPMs and copper present as digenite or nickel present as polydymite. Control of the autoclave residence time is of particular importance to enhance the selectivity of this leaching step, given the dependence of the PGM leaching rates on the extent of copper dissolution.

Sep 1, 2012

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 M. Ito

Cobalt-rich ferromanganese crust and nodule ores from seamount areas contain volcanic and sedimentary rocks as substrate or nuclei and these ores require mineral processing to remove the substrate/nuclei rock before smelting. This paper reviews the results of jig separation and air table treatment for the coarse fraction and flotation and hybrid jigging for the fine fraction. Using these techniques substrate/nuclei rock was removed from the cobalt-rich ferromanganese oxide components. The mineralogical properties and metallurgical treatment methods including hydrometallurgical treatment of low grade ore is also reviewed.

Sep 1, 2012

By Dave Deglon

The Western Cape Mineral Processing Facility (WCMPF) is a collaborative educational initiative between the Departments of Chemical Engineering of the University of Cape Town, the University of Stellenbosch and the Cape Technikon. The WCMPF was established in 1989 with the aim of improving mineral processing education in the Western Cape. Since its inception the WCMPF has had a number of successes in this area, especially in improving the quality of mineral processing practical training. In addition, the WCMPF has played an important role in promoting liaison and interaction between tertiary educational institutions teaching mineral processing in the Western Cape. Over the past decade the WCMPF has played a key role in the education of over five hundred mineral processing graduates and diplomates. This paper presents an overview of the activities of the WCMPF and attempts to encapsulate the ‘lessons learned’ from over a decade of successful functioning as a collaborative educational initiative in mineral processing.

Jan 1, 2003

By Roberto C. G. Oliveira, Scott C. Brown, Brij M. Moudgil

The wettability or surface energy of particle surfaces dictates a number of multiphase ensemble interactions that have a significant impact in mineral processing. Dispersion, bulk powder handling and flotation behavior are just a few of the parameters that are largely due to the degree of hydrophillicity or hydrophobicity on particulate surfaces. Because of the inherent impact of surface wettability in nearly all industries, fields, and multi-phase interactions, a number of simple, precise and accurate techniques for accessing surface wettability or contact angle on macroscopic flat surfaces have been developed. However, these techniques cannot be directly applied to the particulate surfaces that are often in query. Though a number of techniques are available for accessing the wettability of particulate surfaces, these methods are either relative, application specific or prohibitively tedious. In this study, key features of existing techniques are combined to formulate an improved method to delineate particle wettability that is simple, versatile and capable of providing reproducible measurements in an industrial environment.

Jan 1, 2003

By Ben Murphy, Alejandro Yanez, Tatu Miettinen

"Flotation using large volume cells has grown in importance during recent years, particularly given the increasing demand for minerals whilst ore grades are decreasing. Outotec introduced the TankCell® e300 in 2007 to enable concentrator plants to process these higher tonnages. From the beginning, TankCell® e300s with FloatForce® mixing mechanisms have demonstrated good metallurgical performance with decreased operating costs and high availability. This paper deals with specific engineering challenges that need to be considered when installing these units rather than giving examples of performance. Today there are over 100 TankCell® e300s operational worldwide. As more of these units are installed new technical challenges are encountered and solutions developed to maximize their productivity. Lessons have been learnt by operators, engineering companies and the cell manufacturers on how best to design and layout these cells in modern concentrators to ensure smooth transition from design to installation to operation. This paper presents information on important design considerations and learning that has been obtained through the design, installation and commissioning of the TankCell e300 around the world. Areas pertaining to cells layout such as feed and discharge arrangements along with items of metallurgical concern such as sampling, reagent addition and the potential benefits of installing a variable speed drive on the motor will be covered in depth."

Jan 1, 2014

By V. E. Vigdergauz

The work presented shows results of electrochemical study of pyrite hydrophobicity evaluated by air bubble induction time (IT) measurements. On the basis of measured IT?s an average thickness of the thin liquid film prior to its rupture has been evaluated, which confirms long-range character of the interactions between air bubbles and hydrophobic surfaces. Obtained data are discussed in the frame of recent studies of structures of solid-liquid interface based on molecular dynamics simulations and results of surface force measurements.

Jan 1, 2014

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

"Nickel-metal hydride batteries (Ni-MH) are storers of electrochemical energy, which have a higher specific storage capacity than lead or nickel-cadmium batteries. The demand for Nickel-metal hydride batteries is increasing rapidly since their market launch in the early 1990’s. Today there is no suitable and sustainable recycling process to recover nickel, cobalt and rare-earth metals. The discarded batteries are used today in the steel industry as alloy material because they contain nickel. Cobalt and rare-earth metals (RE) are lost; they are non-recycleable.In a German governmental funded research project, IME Aachen, ACCUREC Mühlheim and UVR-FIA Freiberg are cooperating in processing as well as in creating a feasibility study. The target of this project is the development of a new recycling process for metal recovery from Ni-MH-batteries. The proposed process described in this paper consists of a combination of mechanical, pyrometallurgical and hydrometallurgical processing steps. This process is capable of treating all types of Ni-MH-batteries. After comminution steel and organics are separated. The separated Ni-MH is smelted in an electric arc furnace. The products are a nickel-cobalt alloy and a slag phase enriched with rare-earth oxides for further treatment to ‘mischmetal’. Both the Nickel-Cobalt alloy and the ‘mischmetal’ will be directly used in battery production."

Jan 1, 2003

By M. Rudolph, D. H. Hoang, N. Kupka

"Froth flotation has been subjected to modelling since the 1930s and there is a large variety of approaches that intend to portray the entire process. Among these, three fundamental models could be considered exhaustive: the Pyke model [1], the Yoon model [2] and the Schwarz and Koh model [3]. The first model makes use of the generalized Sutherland equation collision model, the Dobby-Finch attachment model and its own stability model, the second model considers an extended DLVO approach for the attachment and stability whereas the third model makes use of computational fluid dynamics. Using a scheelite ore as a test case, a specific batch flotation test was repeated ten times and analyzed for chemical assays, mineralogical studies and froth properties. The detailed data are used to feed the three flotation models aforementioned in order to compare the outcomes of the three approaches, their capacity to reflect reality and to predict it. This article intends to pave the path towards reliable process models incorporating in depth mineralogy information, e.g. surface liberation, particle size and particle shape. KEYWORDS Froth flotation fundamental models, scheelite, automated mineralogy, critical assessment. INTRODUCTION In mineral processing, only three approaches aiming at describing froth flotation fundamentally could be considered exhaustive: Pyke’s collision and sliding approach [1], Yoon’s kinetic approach [2] and Schwarz and Koh’s approach [3]. The models will hereafter be referred to as Pyke model, Yoon model and Schwarz and Koh model. The first model makes use of the generalized Sutherland equation collision model, the Dobby-Finch attachment model and its own stability model, the second model considers an extended DLVO approach for the attachment and stability whereas the third model makes use of computational fluid dynamics. All three approaches rely on the widely accepted idea that flotation is a kinetic reaction dependent on a flotation rate constant kp, as expressed in Eq. [4]:"

Jan 1, 2018

By Sanjeeva Latchireddi

The effective utilization of the energy in comminution devices depend on how efficiently the broken particles leave the breakage field as soon as they reach product size. In crushers the transport of broken particles smaller than CSS is done by gravity (vertical) thus allowing the energy to be applied to new particles. However, in AG/SAG mills, gravity becomes the energy field and the transport of particles is horizontal which needs a suitable discharge mechanism and has been found to have significant effect on grinding efficiency. The material transport in AG/SAG mills depend on how efficiently the discharge system (grate and pulp lifters) operates. Material transport plays a significant role on efficiency of horizontal grinding mills ? AG/SAG/Ball mills. The magnitude of benefits that can be achieved with efficient material transport in AG/SAG mills has been demonstrated in a Greenfield milling operation at Mirabela Mineração?s SantaRita Nickel operation located in northeastern part of Bahia in Brazil. This grinding circuit was commissioned in October 2009, which was designed as a typical SABC circuit to grind 4.6 mtpa (575tph) to produce a P80 of 125um with 10-12% ball charge in SAG mill. However, it has been operating as ABC circuit without any grinding media in SAG mill. The nameplate design capacity has been achieved in few days and has gradually increased to an average of +800 tph and still it is operating in ABC mode. The milling circuit commissioning resulted in small and relatively simple measures to rectify, which was reflected in the rapid commissioning of the milling circuit and it achieved the nameplate capacity within days. The Santa Rita grinding circuit consists of one 30?x 15.4? 8.5MW SAG Mill fitted with Outotec patented Turbo Pulp Lifters (TPL TM ) in close circuit with HP400 short head pebble crusher and one 20? x 28.4? 5.5MW Ball Mill in closed circuit with Warman cyclone cluster fitted with 10 x 26? CAVEX cyclones. This paper examines the comminution design process, operating philosophies, experiences, post commissioning optimization, and future development works. Evaluation of the milling circuit performance relative to the design criteria is also discussed. Keywords: Autogenous Grate (AG), Semi-Autogenous Grate (SAG, Turbo Pulp Lifter (TPL)

Sep 1, 2012

The reactivity of clay minerals and variety of these reactions are greater than any other known colloidal material. While it is acknowledged that clay minerals can cause problems in mineral flotation, the literature contains conflicting evidence, particularly with respect to the effect of clays on froth stability. It is well known that achieving and maintaining optimum froth stability is an influential factor in determining froth flotation performance. However, the presence of clay minerals in the ore is a major challenge to obtaining a stable froth. In fact, clay minerals could reduce froth flotation performance by both decreasing and increasing froth stability. The mechanism by which clay minerals affect froth stability is not fully understood and needs to be investigated further. In order to improve flotation performance, reliable knowledge of the effect of clay minerals on froth stability is essential which is discussed in this paper. Keywords: froth flotation, froth stability, clay, clay minerals

Sep 1, 2012