Search Documents

By Matthew Thurley

Optimisation and control of comminution, pelletization, and agglomeration processes is a complex task with large potential for gains in productivity, energy efficiency, and particle size distribution quality. One factor in realising these gains is the requirement for fully-automated online particle size distribution measurement. Moreover, online particle size distribution measurement that is based on the particles on the visible surface and can avoid or mitigate substantial errors that result from under-sizing overlapped particles and over-sizing areas of fines particles. Literature review indicates a body of substantially 2D photographic based particle size measurement systems that suffer from a large number of significant errors except in the simplest case of a monolayer of particles under good illumination with limited color variation in the material. In order to measure the visible particles on a pile there are a number of requirements including; avoiding particle delineation errors due to variation in material color and shadows, detect overlapping versus non-overlapping particles, and identify areas of fine particles as fines and not large rocks. Results are presented using a fully-automated online measurement system of crushed rock on conveyor belt using a 3D surface laser profile. The system provides continuous online measurement and results are shown on over four hours of production after the primary crusher. Size distribution results are calculated using volumetric estimation of the particles on the surface of the pile. The results show a strong capability to discriminate size variation especially in the 10% and 20% passing values. Furthermore results show that if areas of fines are misclassified as large rocks, and overlapped particles misclassified as small rocks, then a near complete loss of discrimination occurs for the P10 and P20 values which become largely constant values.

Jan 1, 2014

By G. Aguilera

It is known that an addition of rigid particles into a fluid medium changes the flow field. Therefore, the rheological behavior of suspensions will be hardly Newtonian, such as their continuum phase. This phenomena was studied by Einstein in 1906 (Einstein, 1956) for the single case of spherical particles in a continuum liquid of a very dilute suspension. The final analysis applied for suspensions was derived from the evaluation of the behavior of ideal gases, finding a simple expression for the viscosity of the dispersion. All the following works about the hydrodynamics of suspensions at low and high solid contents was based in the Einstein´s model. For clay minerals suspensions where the physical and chemical properties of the particles are complex, it was found that the Einstein´s model is not a good approximation, even so for the most dilute dispersions. The present paper shows a new approximation that describes the non-Newtonian behavior of the suspensions of clays, and the attempt of understand how the different fine sizes, shapes and physico-chemical properties of clay particle surfaces give specific characteristics of plasticity, viscosity or visco elasticity to suspensions. Keywords: viscosity, clay minerals, einstein´s model, dilute suspensions

Sep 1, 2012

By Ingvar Ymén, Anders Sandc, Jan Rosenkranzc, Lisa Malma, Ann-Sofi Kindstedt Danielssonb

The understanding of particle surface properties is essential for the study and evaluation of froth flotation phenomena, particularly in the investigation of various chemical or reagent effects. Dynamic Vapor Sorption (DVS) is a method used for the analysis of surface properties of powders for instance in the pharmaceutical industry. To the knowledge of the authors, it has however not been used before in applications related to mineral processing. The DVS technique involves measurement of the water uptake of a relatively small amount of sample as a function of the relative humidity (% RH) in a temperature-controlled environment. The purpose of this work was to evaluate the method and investigate how it can complement existing techniques for surface characterization in mineral processing. Four samples (feed, CuPb concentrate, Cu concentrate and Pb concentrate) from the Cu – Pb flotation process in the Garpenberg concentrator, Sweden, were analyzed by DVS and the traditional capillary absorption technique (Washburn capillary rise). This enabled comparison between the two methods and evaluation of their respective advantages and disadvantages. Both methods give the expected ranking of the hydrophobicity for CuPb concentrate, Cu concentrate and Pb concentrate, but a discrepancy was observed for the feed. Washburn gave a value for the contact angle which was in the same range as for the CuPb concentrate, whereas DVS gave a value for the moisture uptake which was much higher than for the CuPb concentrate. Thus, DVS ranks all samples correctly, but with an unexpectedly high value for the feed whereas Washburn gives good ranking for three samples out of four. Potential reasons for the discrepancies are discussed.

Jan 1, 2018

By S. Chuanyao

In last decade, along with its booming Chinese economy, China?s higher education has experienced rapid growth. In 2010, the number of various colleges totals more than 3500, with 2.2 million faculties registered. Currently there are almost 30 million students studying in the colleges, 3 times more than 10 years ago. Mineral Processing was initiated in 1949 as a sub-discipline of Mining Engineering, one of the 13 first level disciplines. Mineral Processing is now established in 34 Chinese colleges, recruiting 2600 undergraduate students, 540 postgraduate students and 100 PhD students every year. A further 9 institutes offer postgraduate education in this field. More than 3000 graduates majoring in Mineral Processing join the industry or institutions each year. The four-year undergraduate teaching and practical training in the colleges is designed to produce qualified mineral processing professionals. This includes courses in mathematics and natural science, fundamental engineering and basic and specialization courses. Recently, the ?Excellent Engineer Program? was launched to strengthen students? practical capabilities. This is a 3+1 teaching and training model; 3 years of theoretical course study plus 1 accumulated year of various practical studies, either inside or outside the college. As for graduate employment, mining-related major graduates have been in a good demand thanks to the intensive investment in mineral sector by Chinese companies. The shortage of experienced metallurgists generates a greater than 90% employment rate for Mineral Processing graduates. However, the biggest problem we are still facing is the gap between the quality of the graduates and the requirements of industry, as a result of occupation attraction, teaching systems, faculty quality, and so forth. Another problem is international orientation. Although nowadays Chinese-foreign cooperation in college education is popular, collaborative mineral related projects are far less common, leaving much room for improvement. Looking ahead to the next 10 years, we still have the right reasons to estimate continued prosperity in the minerals sector as well as mineral processing education in China. A brief analysis and views on this will also be shared in the presentation. Keywords: China, mining engineering curriculum, excellent engineer program

Sep 1, 2012

By Kyoungkeun Yoo

A citric acid leaching test after heavy medium separation process was performed to remove the heavy metal contaminat such as Pb, Cu, and Zn from contaminated soil. The lead component was removed from soil by heavy medium separation whereas zinc component shows 0 % - 37.9 % removal ratio with particle size. The citric acid leaching was conducted to remove the remained zinc component. The removal ratio of Zn reached to more than 95 % under the conditions; 10 % in pulp density, 200 rpm in agitation speed, 50 °C, 2 mol/L in citric acid concentration at 2 hrs in leaching time. These results suggest that the heavy medium separation method followed by citric acid leaching is effective for treatment of soil contaminated with various chemical forms of heavy metal. Keywords: metal contaminated soil, citrate, heavy medium separation, zinc

Sep 1, 2012

By Arkady Senchenko, Andrey Vasiliev, Alexander Aksenov, Metodi Zlatev

"This paper considers the issue of treating argillaceous oxidized ores with low gold grade (around 1.0 g/t). These ores according to their gold recovery level can be treated by heap leaching and agitation cyanide leaching, but low gold grade makes this treatment uneconomic. Heap leaching of argillaceous ores requires high consumption of binding agent for pelletizing to create suitable hydro-physical properties of material, which leads to increasing process cost and makes the material treatment unprofitable. Agitation cyanide leaching of this ore requires grinding processes; these expenses would not be paid back by the amount of gold recovered. Considering the above, poor argillaceous oxidized ores are recommended to be treated according to a combined technology including fractionation of ore, heap leaching of coarse fraction and agitation leaching of argillaceous fraction. Complex approach application allows one to avoid expenses incurred for material grinding and high consumption of binding agent for pelletizing. The success of this technology implementation will firstly depend on the quality of material fractionation, therefore the section of disintegration and division of ore into different components will be the most important part of flowsheet development for gold production. When disintegrating minerals at positive temperatures both standard (mechanical disintegration - scrubbers) and innovative (hydraulic method of disintegration - HydroClean units) equipment is applicable. HydroClean units are characterized by lower energy and water consumption. In a number of cases it is required to treat frozen ores. When treating frozen material standard approaches to disintegration are not reasonable due to their low efficiency. In order to treat frozen material a two stage disintegration flowsheet with screening after each stage is recommended. The first stage is recommended to be performed in a scrubber, the second - in a HydroClean unit. This technological flowsheet will provide high and steady values for ore separation into fractions at low energy consumption for disintegration."

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 J. Wiese, K. Corin, Z. Song

"Relating flotation performance to the electrochemical characteristics of a pulp is complex both in fundamental research and in practice. In the case of thiol collectors, different Eh values in the flotation system can result in the formation of the dimer or the metal thiolate which may or may not enhance the hydrophobicity of the mineral. Reducing or oxidizing conditions in a flotation system, viz. changing the Eh value, are usually manipulated to achieve an optimum flotation response by control of pH and dissolved oxygen levels in the system. A variation in pulp potential may also be achieved by the addition of potential modifiers such as sodium hydrosulphide (NaHS), sodium hypochlorite (NaClO) or hydrogen peroxide (H2O2). There exists anecdotal evidence which suggests that the addition of small amounts of H2O2 to the flotation process can improve sulphide mineral recovery. The objective of the present study was to investigate the effect of the addition of the potential modifier, H2O2, on sulphide mineral recoveries and grades in the flotation of sulphide minerals from two copper bearing ores from China and compare the results to those obtained for a PGM bearing ore South Africa. Batch flotation tests were conducted using the three different ores at the natural pH of the different systems, in the presence of a xanthate collector and the absence and presence of H2O2 as a potential modifier. The results indicate that the addition of carefully controlled low concentrations of H2O2 resulted in improvements in flotation performance. INTRODUCTIONElectrochemical potential as a control parameter in the flotation of sulphide minerals has been widely studied (Allison et al., 1972; Gardner and Woods, 1979; Ross and Van Deventer, 1985; Chander, 2003; Woods, 2003; Javadi, 2013). There is concensus that in order to be recovered during flotation, sulphide minerals require a suitable redox environment. During the flotation process thiol collectors and sulphide minerals are involved in electrochemical reactions which result in the formation of hydrophobic species at the mineral surface (Finkelstein and Goold, 1972; Rand and Woods, 1984). Sulphide minerals act as semiconductors and electrons are transferred during the interaction of the mineral with collector. The resultant potential difference and its magnitude are responsible for the transfer of electrons and the rate of the reaction (Bard and Faulkner, 2001; Fuerstenau et al., 2007). Reducing or oxidizing conditions in a flotation system, viz. changing the Eh value, may be manipulated to achieve an optimum flotation response by control of pH and dissolved oxygen levels in the system (Heyes and Trahar, 1979). The use of potential modifiers viz. reducing or oxidizing agents which include H2O2, NaClO, and NaHS, is an alternative method by which to control the potential of the pulp in a flotation system which may or may not promote the flotation of desired minerals (Rao, 2004). The oxidizing agent, H2O2, undergoes a cathodic reaction which can result in the enhanced flotation of valuable minerals. The potential of the system is increased which results in a shift in the mixed potential of a mineral. The magnitude of the over-potential influences the rate of the oxidation process and thus the flotation response of sulphide minerals (Kocabag and Guler, 2008). Equation 1 shows the proposed oxidation of xanthate by H2O2 (Lipkina and Streltysn, 1970)."

Jan 1, 2018

By Cheng Xiang, Nan Ye, Xinyuan Ke, Yang. Jiakuan, Huabin Wang

Bayer red mud is a highly alkaline residue produced by the alumina industry through the Bayer process. Its disposal is a worldwide problem. The high alkali content and poor pozzolanic activity is aconstraint for its utilization on construction materials. In this study, the red mud was activated through an alkali-thermal method to improve its activity so that it can be utilized in geopolymerization. The red mud was mixed with different amounts of sodium hydroxide, and calcined under 800 °C to produce geopolymer precursors, and then mixed with water directly to prepare one-part geopolymer. X-ray diffraction was conducted to study the phase transformation of red mud and the mechanism of its geopolymerization. Nitrogen Isothermal Adsorption tests were conducted to analyze the pore structure of the geopolymer binders. The results show that calcinations with alkali would promote the Al in red mud transforming into glassy SiO2 to form the N-A-S phase which is soluble in water. When the red mud was calcined at 800 °C with a Na2O addition more than 10%, the dissolving of Si and Al from red mud was greatly improved. The thermal-alkali activated red mud with 10% Na2O obtaining a compressive strength of 9.77 MPa after it reacted with water and cured for 7 days at 20 °C and 95% RH. But the strength decreased as the curing time extended to 28 days. The reason is suggested to be that the polymerization of Al-O and Si-O is unstable due to the low Si/Al ratio of red mud. The alkali in the structure dissolves again into the pore water and corrupts the pore structure. Therefore, the thermal-alkali red mud should be combined with other reactive aluminosilicate materials such as granulated blast furnace slag to absorb the alkali released by the thermal-alkali red mud at the latter curing days.

Jan 1, 2014

By F. Ngoroma

Concentrators processing PGM bearing ores make use of polysaccharide depressants to reduce the recovery of the undesired naturally floatable gangue minerals, mainly silicates, present in the ore. Recent work has shown that high depressant dosages can completely depress naturally floatable gangue and thus prevent it from reporting to the concentrate. These high depressant dosages can, however, have a negative effect on the recovery of valuable minerals present in the ore by reducing the stability of the froth. In order to counterbalance the effects of depressant addition, frothers are added. It is, however, preferable to maintain independent control over bubble size and froth stability which is difficult to achieve with only one frother. An alternative strategy is, to use a blend of frothers, e.g. a weaker frother in combination with a stronger frother. Such a system allows an additional degree of freedom: changing the ratio of the two frothers, that would provide more independent control of bubble size and froth stability. This study demonstrates, through the use of batch flotation tests, how blending low molecular weight alcohols with commercially available frothers impact the solids and water recovery, as well as the valuable mineral recovery and concentrate grade in different PGM ores. Higher water and solids recoveries together with higher valuable mineral recoveries (>90% copper and >70% nickel) were obtained from tests using frother blends.

Sep 1, 2012

By P. Han

The preparation technological conditions and regeneration method of two novel granulated adsorbing materials of rectorite/fly ash composite (Material 1) and rectorite/water quenched - slag composite (Material 2) and the use of them to remove heavy metals from copper smelting plant wastewater have been studied. The experimental results showed that under the preparation conditions with the ratio of rectorite to fly ash or water - quenched slag of 1:1, the amount of the additive (Industrial Starch, IS) of 15% (Material 1) or 10% (Material 2), the addition of 50% water, and the calcination temperature of 500? (Material 1) or 400? (Material 2), the efficiency of heavy metal removal with the granulated materials was the best, whereas the ratio of disintegration loss was the lowest. Under the treatment conditions of natural pH, and with the addition of the granulated materials of 0.07g/cm3 (Material 1) or 0.05g/cm3 (Material 2), a reaction time of 60 minutes (Material 1) or 40 minutes (Material 2), and the adsorption temperature of 25?, the efficiency for the granulated materials to remove Cu2+Pb2+Zn2+Cd2+ and Ni2+ from the copper smelting plant wastewater was 98.9, 97.5, 96.7, 90.2, and 79.1, (Material 1) or 98.2, 96.3, 78.6, 86.2, and 64.2, (Material 2), respectively, and the quality indexes of the wastewater after treatment conformed with the first level of integrated wastewater discharge standard (GB8978-1996). When the adsorption of heavy metal ions on the surface attained saturation the granulated materials could be regenerated by washing with 1 mol/L sodium chloride (NaCl) solution and still with quite good heavy metal removal efficiency. The granulated adsorbing materials had the advantages of high efficiency of wastewater treatment, easy method of solid-liquid separation and regeneration, and a broad prospect of applications.

Jan 1, 2014

By M. Pelser, C Aldrich

"The presence of calcium and magnesium in the hydrometallurgical processing of base metals, results in a number of process difficulties. These problems range from the contamination of the final product (where the final product is a precipitate) to high energy consumptions and large bleed streams during electrowinning. Calcium poses an additional problem in sulphate solutions owing to the low solubility of its sulphate salts. This can easily lead to a process stream that is supersaturated with calcium sulphate, resulting in unwanted solids formation within the process equipment.Several processes are reviewed for the control of calcium and magnesium. Of these, fluoride precipitation was selected for experimental investigation. This method involves the addition of a soluble fluoride to precipitate CaF2 and MgF2. The experiments showed high selectivity for calcium and magnesium over the base metals. The experiments also showed magnesium precipitation to dominate for calcium to magnesium molar ratios greater than 1:3.To avoid the domination of magnesium precipitation, a flow sheet is proposed whereby only a portion of the base metal stream is subjected to fluoride precipitation. For the precipitation, a 10% excess of ammonium fluoride is used to remove the maximum amount of calcium and magnesium. After precipitation and solid-liquid separation the split-stream is returned to reduce the overall calcium and magnesium concentration of the base metal stream."

Jan 1, 2003

By Stoyan Gaydardzhiev, Michel Shengo, Pierre Kalenga

Lab-scale flotation of copper and cobalt oxidized ore from the Luiswishi deposit in the Katanga province (DRC) has been done focusing on the influence of the degree of process water recycling on metals recovery. Results have shown that at 20 % recycling rate, the recovery of copper and cobalt in the cleaner stage have been respectively reduced to 23 % and 45 % in comparison to 53 % Cu and 63 % Co if process water has not been recycled. At 10 % recycling rate however, the system could still tolerate the effect from recycling, since Cu and Co recovery has remained respectively at acceptable levels of 52 % and 60 %. In order to explain the reasons for the observed worsening of flotation results if process water was recycled at rate higher than 20 %, electrochemical investigation of the pulp has been performed. It has been established that the chemical compounds formed in the pulp when process water was recycled, do influence the sulphidization of malachite and heterogenite and impact further collector adsorption. To confirm these assumptions, the effect from thiosulphate ions presence during the sulphidization of high purity malachite has been studied. It has been found, that thiosulphate ions depending on their concentration in water induce variations in pulp properties such as DO content, pH, Es and contribute to formation of undesirable chemical compounds on mineral surface as identified by DRIFT spectroscopy.

Jan 1, 2014

By M. Z. He

Attractive particle interactions which underpin the sliming of gangue mineral particles onto valuable mineral phases are encountered in a number of flotation circuits. Sliming leads to poor flotation recovery of the valuable minerals and high recovery of the gangue particles in the concentrate. To mitigate sliming, low molecular weight poly-electrolytes are commonly used as dispersants during pulp conditioning prior to flotation separation of the valuable and gangue mineral phases. In the present work, the sliming mechanism of sericite onto chalcocite and the influence of interfacial chemistry and two anionic copolymer dispersants (carboxylate substituted polyacrylamide, polymer Cyquest 3223 and sulfonate substituted polymaleic acid, polymer P80) on the sliming interactions were probed in the pH range 5~9. It was shown that the sliming occurred under solution conditions where both chalcocite and sericite particles were negatively charged, as evidenced by their apparent particle zeta potentials. The suspension pH had a profound effect on sliming process as the extent was markedly greater at lower than higher pH. The sliming was found to be due to the chalcocite dissolution, Cu (I) release and oxidation to Cu (II), followed by hydrolysis and specific adsorption, leading to sericite particle surface charge reversal and the formation of electropositive sites on chalcocite surface in the pH range 5~9. Addition of polymer Cyquest 3223 or P80 not only increased the magnitude of zeta potentials of both sericite and chalcocite particles but also reduced the formation of Cu (II) ions and complexes, which mitigated the sliming behaviour. The adsorption of polymer Cyquest 3223 or P80 at 3 g polymer / kg solid or more had a significant impact on the zeta potentials of both sericite and chalcocite particles. Sericite-chalcocite particulate adsorption studies showed that sliming was completely suppressed via an electro-steric repulsion mechanism resulting from anionic polymeric dispersant adsorption at dosages > 3 g polymer / kg solid.

Jan 1, 2014

By M. C. Harris

"In the flotation process the contact angle is an important indicator of the hydrophobicity of a mineral particle. There is considerable literature showing that the contact angle increases when the chain length of the alkyl group associated with the collector molecule used to render the valuable mineral particle hydrophobic increases. The extent to which an alkyl group interacts with surrounding water molecules is quantified thermodynamically by the excess Gibbs energy. In the present paper it is shown that there exists generally a strong linear relationship between the excess Gibbs energy of the alkyl group associated with the collector and the contact angle. The structure-activity of such alkyl groups is in turn related to the total surface area, molecular volume, the molar volume, molecular weight of the functional groups in the molecule and interaction energies. It is proposed that the demonstrated relationship is indicative of the role which the alkyl group component of the collector, which is attached to the mineral particle, plays in increasing the extent to which water molecules at the surface of the mineral are rejected from the surface thus increasing the contact angle. The relationship between excess Gibbs energy and surface tension is further explored with a view to relating the observations quantitatively to the parameters in the Young equation.INTRODUCTIONThe issue of wettability of materials is of great importance to many industrial applications. Wettability studies usually involve the measurement of contact angles which indicate the degree of wetting when a solid and liquid interact. As is well known the contact angle (O) is the angle between planes tangent to the surfaces of the solid and the liquid at the wetting perimeter which is the zone where the air, water and solid phase merge. When the air bubble attaches to the solid surface there is an increase in the air/solid interface area and a decrease in the solid/water interface area. For attachment to occur the cosine of the contact angle should be less than 1 and this will be promoted if the interfacial surface tension between the air and the solid (? SV) is low. Classically the relationship between these parameters has been expressed through the Young equation (1) for a perfectly flat surface:"

Jan 1, 2018

By A. Singh, M. Ntlhane, V. Ross, M. Dlame

"Fine valuable particles are often lost to flotation tailings streams due to inefficient collection by air bubbles as well as passivation of surfaces by oxidation and slimes. The application of high-shear hydrodynamic cavitation devices (HCDs) to overcome this problem has already proven to be a considerable success in the industry. This paper details the results of further investigations that were undertaken at Mintek to better understand the mechanisms involved when preconditioning feed slurries in an HCD. By promoting inter-particle attrition and conditions of high shear within the reactor, cleaning of particle surfaces is enhanced as well as the formation of superfine (nano) bubbles which are believed to aid their agglomeration and subsequent collection by normal sized bubbles. In order to broaden the envelope of understanding with regard to application of the technology, rather than tailings material as investigated earlier, a Platinum Group Mineral (PGM) UG2 ore from the Bushveld Complex in South Africa was used in this study. The results of a series of batch flotation tests in a 10L Denver cell are presented, being conducted after the feed has been subjected to different methods of preconditioning. It was demonstrated that the preconditioning significantly improved the flotation kinetics of the PGMs, the optimum being obtained after around 20 passes through the reactor. This was accompanied by a much enhanced recovery-mass pull relationship and a significant improvement in the grade-recovery response. Significantly, the selectivity between the PGM and the deleterious chromite (expressed as Cr2O3) gangue more than doubled under these conditions. Modelling of the PGM data by means of the modified Kelsall model indicated that both the fast and slow floating rate constants were improved.INTRODUCTIONIt is well known that the flotation recovery of fine and ultrafine particles, typically less than 10 micron in size, is a challenge (Yoon et al., 1989; Miettenin et al., 2010). Although these particles are typically well liberated, due to their very low mass and inertia, the collision efficiency with air bubbles is low as a result of the inability of particles to penetrate the liquid streamlines around bubbles. Hence the probability of contact is often regarded as the ratedetermining step in flotation of ultrafine particles. Introducing more power into conventional flotation machines is likely to solve only part of the problem, as conventional mechanisms are effective only to a point in terms of shear and micro-turbulence. Further challenges are posed by the treatment of low-grade or oxidised tailings dump material, where valuables are passivated due to prolonged exposure to the atmosphere or slimes. Over the years, various mitigating strategies have been investigated, including the use of dissolved air flotation (Martinez-Gomez et al., 2013; Calgaroto et al., 2015), shear flocculation (Subrahmanyam and Forssberg, 1990), seed or carrier flotation (Tabosa and Rubio, 2010), sonication to clean particle surfaces (Aldrich and Feng, 1999; Newell et al., 2006), high intensity conditioning (Bulatovic and Salter, 1989; Chen et al., 1999; Tabosa and Rubio, 2010), and various electrochemical approaches such as changing Eh in order to promote formation of dixanthogen, dissolution of oxidation products by lowering the pH, activation by sulphidisation (Newell et al., 2006; Becker et al., 2014), and the use of alternative collectors."

Jan 1, 2018

By Z. L. Huang

A new porous apatite product was prepared using phosphorite from Yichang China by a tem-plate-directed method in self-made reaction equipment under constant temperature and pressure. The product was characterized by XRD, FT-IR and SEM. The results showed that the product was a kind of micrometer porous sphere three-dimensionally structured by apatite nanoflakes, that the average thickness of nanoflakes was about 50 nm, that the average pore size was about 1.2 µm and that the particle average size was about 20 µm. Great amounts of Ca2+channel, high special surface area and regular spherical shape show the potential promising applications of this special porous apatite product in the fields of catalyst, medication, chemical engineering and environment engineering

Jan 1, 2014

By R. A. Kleiv, H. Havskjold, N. Church, T. Malvik, M. Tro, E. Larsen

Liberation is one of the major purposes of comminution in mineral processing. In the simplest form, two or more minerals are present in a particle and have to be reduced such that the individual particles contain only one mineral. The complexity of the mineral intergrowth varies from ore to ore. Poor magnetic separation of iron ore may have many causes. In this paper, the emphasis is given to the problem of fine magnetite inclusions in quartz or other gangue minerals. This is highlighted by two Norwegian cases: one on a magnetite ore and the other on a hematite/magnetite ore. The inclusions in question are so small that they are not liberated by reasonable grinding. In both cases, the result has been either poor recovery or lower grade concentrates than desired. The first example concerns production of direct reduction concentrates from magnetite. Magnetic inclusions in gangue particles will be magnetized enough for the particles to pass into the concentrate. The second example is given a more detailed study, where the problem is caused by silicates with small inclusions of magnetite in a combined LIMS and WHIMS separation. This study included microscopy, Davies tube testing, and magnetization measurements. In particular, large gangue particles with magnetite inclusions were shown to have a tendency to bypass the LIMS separators as drag forces in presence of hematite are large. Such particles will then be picked up by the WHIMS as their magnetization is higher than for hematite. This was demonstrated by Davies tube tests, which indicated that such particles were picked up in preference to hematite particles. However, the Davies results did not give a good quantification. Magnetization measurements of gangue particles with magnetite inclusions was shown to be a better tool to quantify the magnitude of the effect of magnetite inclusions in magnetic separation.

Jan 1, 2018

By C. L. Tang

Parts of the wastewater are reused directly and the rest moderately purified and reused, so the utilization rate of wastewater of the whole processing plant reaches 100 percent. At the same time, beneficiation indicators have been improved stably, and great economic and social benefits have been achieved.

Jan 1, 2014

By V. Tsyplakov

This article reviews factors of preg-robbing effect, occurring in the course of pressure oxidation of ore and concentrates, containing chloride compounds and so-called 'organic carbon'. The article also summarizes the main results of the studies and testwork conducted to overcome this effect. The following efficient preg-robbing mitigation methods have been noted: higher temperature of pressure oxidation process, preliminary removal of natural carbonaceous material from concentrate, chloride removal prior to concentrate pressure oxidation, and addition of water-soluble organic blanking agents, which suppress the adsorption activity of the native ore adsorbents. Keywords: preg-robbing, double-refractory gold concentrates, pyrite, arsenopyrite, blanking agents, pressure oxidation, autoclave leaching

Sep 1, 2012