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By Y. M. Zhao

The dry coal preparation technology based on air dense medium fluidized bed is an innovative dry highly efficient technology of coal by introducing fluidization technology into beneficiation.. A modularized 40-60 tones/hr system (KZX-40) with an air dense medium fluidized bed separator was established. The construction cost of the modularized system is only 1/3 of the traditional wet heavy-medium coal preparation plant construction cost with the same capacity, and the consumption of dense medium can be reduced by 50%-60%. The footprint and volume of the system are decreased by 75% and by 89.81%, respectively. These facts show the improved intensity, efficiency and economy of modularized coal preparation technique. The modularized KZX-40 system can be used to separated 50-6 mm coal over a separation density range of 1.3-2.2g/cm3 depending on the variation of <1mm fine coal content. The separation efficiency of the system was investigated at low and high separation densities by float-sink experiments. The partition curve of the products at low separation density shows that the separation density (d) is 1.33g/cm3, and the probable error (E) value is 0.05g/cm3. Using 50-6mm coal with an ash content of 55.35% as feedstock, at a high separation density of 1.61g/cm3, the clean coal with an ash content of 14.67% and the tailing with an ash content of 71.26% are produced with an E value of 0.06g/cm3. It is clear that the modularized KZX-40 system is suitable for separating 50-6mm coal effectively. During the dry coal preparation process, the dust is removed by the bag collector and recycled back into the separator. So the system has the advantages to work without environmental pollution and water. The modularized system greatly reduces the construction and operating costs and decreases the area and volume required, compared with wet dense medium system. The system is applicable to the coals located in arid regions and also to the coals that tend to slime during wet separation. Keywords: modularized, KZX-40, fluidized bed, beneficiation

Sep 1, 2012

By M. Saghaeian, R. Hejazi, L. Hosseini

The specific surface area (Blain value) of iron ore concentrate entering the pelletizing plant is one of the characteristics most effective on the overall performance of the plant such as producing harder pellets, decreasing additives consumption, and decreasing energy consumption. Therefore, preparing the feed entering pelletizing plant is required. The iron concentrate entering Ardakan pelletizing plant located in Yazd province, Iran bears relatively low Blain value (approx. 1600 cm2/g) which necessitates one stage of regrinding so as to increase the Blain value to more than 1800 cm2/g. Studies were conducted and results showed that HPGR is the best regrinding equipment for increasing specific surface area. Conducting pilot plant tests on the concentrate sample revealed that specific throughput is 181 to 263 ts/hm3 and specific energy consumption is 1.6kWh to 2.2 kWh. Pilot tests also showed that one stage of grinding results in 407 cm2/g to 553 cm2/g increase in specific surface area. Based on these results, diameter of rolls, length of rolls, power consumption and grinding force were calculated to be 1.3 m, 0.9 m, 1276 kW and 13800 kN, respectively. Therefore, an HPGR with a roll diameter of 1.52 m, roll width of 1.1 m, power of 1660 kWh and a capacity of 500 t/h has been selected and implemented in Ardakan pelletizing plant. Industrial performance of HPGR and its effects on the plant study results show that limestone and bentonite consumption has reduced about 60% and 30%, respectively. Total Fe of the final pellet has increased from 65.5-65.7% to 66.2%. Cold compressive strength (CCS) and porosity of final pellets are approximately 292 kg/pl and 20.4, which are in the acceptable range.

Jan 1, 2014

By D. H. Xiong

Low grade oxidized iron ores are usually not economic to utilize. However, the development of SLon magnetic separators and other new technologies make the process cost lower and lower. In this paper, several low-grade oxidized iron ore process flowsheets are introduced. The key procedure is that at the early stage, SLon magnetic separators are applied to discharge as more tails as possible with very low cost, only a small portion of rough concentrate going to the cleaning stage, showing the new technologies are profitable for such iron ores.

Jan 1, 2014

By Ying Gu

Automated mineralogy methods and tools, such as the Mineral Liberation Analyzer (MLA) and the QEMSCAN, are now widely used for ore characterization, process design and optimization. Several case studies published recently demonstrate that large gains can be obtained through grinding and flotation optimization guided by automated mineralogy data. However, since automated mineralogy can only provide the information pointing to where the process gains can be made, it does not directly impact the production gain. Thus, a question is often asked: how to value the contribution of automated mineralogy to process improvement of a particular plant. This appears to be a difficult question. On close examination however, it is found that this is essentially a question of the value of information and it is reasonably well documented in various other industries. Hubbard (2010), in chapter 7 ?Measuring the Value of Information?, dealt with exactly this type of problem. The value of information is the reduced risk of an investment and opportunity loss. The methods Hubbard developed can be applied to estimate the value of automated mineralogy, as well as metallurgical test work, which also produces information that reduces the risk of investment. This paper first introduces Hubbard?s theory on the value of information and how to measure it. It then applies his methods to estimate the value of automated mineralogy, using Anglo Platinum?s fine grinding project as an example. In this case, the value of automated mineralogy includes the reduction in investment risk worth US$ 62.5million, in project rejection worth US$197 million and in opportunity loss worth US$320 million. In the end, a general model is developed to allow the simulation of the value of automated mineralogy in different mining operations constrained by different parameters.

Sep 1, 2012

By T. Fujita

The incinerated bottom ash includes titanium oxides and a small amount of chromium oxides. Initially, 89 % of chromium was removed from ash at magnetic flux density at several stages of wet magnetic separation from 0.05 T to 6 T. The bottom ash from an industrial waste incineration process includes about 10 % of TiO2. The minerals that contain titanium are rutile and perovskite. These minerals are paramagnetic and show low magnetic susceptibility, therefore, the high magnetic field strength, created by a superconducting magnet, is necessary to capture these minerals. At the first stage of separation, a magnetic field strength of 6T was applied in order to attract the particles that contain iron oxides to the higher magnetic field region. At the second stage of separation, the magnetic capture rate of weekly magnetic particles decreased with increasing the magnetic susceptibility of the aqueous solution (i.e. the medium for dispersing the particles) in order to separate the highly magnetic materials. The para-magnetic salt such as ferric chloride was dissolved in the water to increase the magnetic susceptibility of the medium. After a two-step wet HGMS with superconducting magnet, the grade of TiO2was increased from 10 % to 28 % with a recovery of 64 %.

Jan 1, 2014

By K. Gonçalves

One of Vale?s sponsored research project is aimed at the implementation of a practical scale-up procedure for flotation. In this context, detailed flotation kinetics characterization is of critical importance. This work presents the results of a campaign aimed at characterizing flotation kinetic parameters with respect to particle composition. MLA analysis was carried out for 40 narrow-sized iron ore particles with known flotation time from a controlled flotation kinetic test. The iron ore sample studied (59% hematite and 41% quartz) comes from a mine in the southeast of Brazil and the type of reagents applied are the same as used in the plant. For the reagent conditions tested, the overall rougher concentrate (sink) yielded 79.1%, pure quartz and hematite recoveries to the froth were 56.0% and 4.8%, respectively. The results from the kinetic tests show that the flotation rate of the particles doesn?t vary much (~0.03s-1) with composition and that the fraction of floatable particles in each grade controls the separation action. The results show that the rate of flotation is controlled by transport and that the selectivity is controlled by the fraction of floatable particle of each phase.

Sep 1, 2012

By S. K. Pan

The process flow-sheet adopted in treating hematite iron ore in India through wet circuit generates not only 15-25% slime of Run-of-Mine (ROM), but also results in loss of very high quality fine iron ore particles along with it. As the reserves of hematite iron ore is depleting, it is necessary to explore the possibility of upgrading other types of low grade iron ore and slime for recovery of iron minerals; extensive research in this field is being carried out. While beneficiation of low grade ore is yet to be established, slime beneficiation has been quite successful and many installations of slime treatment plant are underway. In SAIL mines, the slime is mainly the discarded particles from Classifiers, which are less than 0.2 mm sizes. R& D initiative has been focussed on the beneficiation of the slimes (49-60% Fe, 3-10% Al2O3 & 4-10% SiO2) of Dalli mines to generate concentrates assaying 62-64% Fe, 2-3% Al2O3, 3-4% SiO2 and a few innovative facilities for the same has been introduced at this mines of Bhilai Steel Plant (BSP). At Dalli mines, the slime is of very poor quality. A typical slime analysis assays 48.54% Fe, 15.1% SiO2, 8.5% Al2O3 and consists nearly 60% (by wt.) particles less than 38 micron. Slime analysis revealed substantial quantity of very high density mineral particles, those causes jamming of Thickener due to faster settling. A novel technique has been implemented to classify the concentrate ore particles from the gangue mineral particles by processing through Fluidized Bed Classifier (FBC) system, which is a gravity concentrator, to treat 50% of the slime generated and the rest is treated through de-sliming hydro-cyclone followed by Medium Intensity Magnetic Separator (MIMS). A special self-vibrating launder has been designed and introduced into the system to recover tiny iron ore particles, which could not get captured by the permanent Neodymium rare earth magnet in MIMS. The classified iron mineral particles from FBC are further treated in a battery of hydro-cyclones followed by modified Slow Speed Spiral Classifier (SSSC) unit. Multiple feed entry system to the SSSC unit is unique and use of particular feed entry point depends on the desired quality of the product and thus converted to a beneficiation equipment rather than mere de-watering unit. By processing slime in FBC system, the valuable iron ore particles with 62.5% Fe, 5.2% SiO2, 2.23% Al2O3 has been recovered from the slime at a material yield of 30%. And very high valued concentrate particles with more than 65% Fe has been sorted out through the magnetic separation route. The overall extra production of beneficiated slime concentrate is 40-45 tph with 63-64% Fe from a slime feed of 120-130 tph solid. This paper outlines few new approaches in iron ore slime beneficiation at Dalli mines for maximum recovery of valuable minerals. Keywords: fluidized bed classifier (fbc), iron ore slime of dalli mines, medium intensity magnetic separator, slow speed spiral classifier (sssc)

Sep 1, 2012

By Indrajit Paul, Atanu Pal, Kapil Modi, Sanjay Chandra, Chandra Sekhar, Srinivas Dwarapudi

"High alumina content in the Indian iron ore fines (2.5% Al2O3) resulted in poor quality pellets at the recently commissioned 6 MTPA pelletizing plant and a study was under taken to establish suitable pellet chemistry through proper fluxing agents. Limestone fluxed pellets were prepared at varying basicity (0 to 0.8) and pyroxenite fluxed pellets at varying MgO contents (0 to 3%) to study their effect on the metallurgical properties. Fired pellets were tested for their strength, RDI, reducibility and swelling. Microstructural studies, optical and SEM-EDS, were carried out to quantify different phases and their chemistry. Acid pellets exhibited poor quality whereas limestone pellets at 0.8 basicity and pyroxenite pellets at 1.5% MgO exhibited optimum metallurgical quality. Formation of widely distributed silicate melt in limestone pellets and high melting point slag & magnesioferrite in pyroxenite pellets found to improve their quality. However during commercial production of MgO bearing pyroxenite pellets, their room temperature and low temperature properties found to be inferior, but exhibited better high temperature properties, viz. softening-melting behavior. Contrary to this, commercially produced limestone pellets, comprising CaO, exhibited better strength and RDI but showed poor high temperature properties. To yield the benefits of both CaO (for good strength and RDI) and MgO (for low swelling and high softening), a dual flux combination was established by using both limestone and pyroxenite/olivine together that resulted in optimum metallurgical properties. Coke rate at the blast furnaces found to be reduced by 1kg for every1% increase of dual flux pellets in the burden.INTRODUCTION Iron ore agglomerate quality plays a vital role in decreasing the reducing agent consumption and increasing the productivity of blast furnace. In most of the integrated steel works, the burden mix for blast furnace is decided as per the availability of the iron ore agglomerates like sinter and pellets. More attention has been given in recent years to the use of fluxed pellets in blast furnace due to their good strength and improved reducibility, swelling and softening melting characteristics. Generally, quality of pellets is influenced by the nature of ore or concentrate, associated gangue, type and amount of fluxes added and their subsequent treatment to produce pellets. These factors in turn result in the variation of physicochemical properties of the coexisting phases and their distribution during pellet induration. Hence properties of the pellets are largely governed by the form and degree of bonding achieved between ore particles and the stability of these bonding phases during reduction of iron oxides (Panigraphy et al., 1990). It is important to note that conditions and parameters of pelletizing are specific to given ore or concentrate; the present study is undertaken for typical Indian hematite ore fines high in alumina. Except authors earlier work on quality of pellets from Indian iron ore (Dwarapudi et al., 2008, 2010), there is no considerable literature reported on the effect of pellet basicity and MgO content in the basicity range of 0 to 0.8 for Indian hematite ore."

Jan 1, 2018

By S. Banisi, A. R. Hasankhoei, A. R. Ghasemi, E. Razi, G. A. Parsapour

At the pelletizing plant of the Gol-E-Gohar mining and industrial company two parallel dry closed grinding circuits, each with the average throughput of 300 t/h, are used. Each grinding circuit consists of a burner, a dry ball mill (6.2 m×13 m) and an air separator. The ball mill consists of a 2 m-long drying and an 11 m-long grinding chambers. The iron ore concentrate is fed to the drying chamber by a feed chute. The first 1.35 m of the drying chamber consists of 56 flights in two rows to decrease the feed moisture from 5% to below 0.2% and the rest of dryer chamber consists of deflectors to pass the material to the grinding chamber. It was found that when the feed moisture content increased from 1.3% to 3.5%, the throughput decreased by 12% (35 t/h) indicating a low performance of the dryer. Monitoring the wear rate of flights for a period of 12 months showed that the first 0.8 m length of the flights length did not experience any wear. This means that about 59% of flights do not contribute in material distribution and drying. A DEM simulation of feed chute and the drying chamber demonstrated that due to the inappropriate design of feed chute most of materials do not get in touch with the first 0.8 m length of the drying chamber. To overcome this problem, various feed chute designs with different geometries were simulated by the KMPCDEM© software. With the aim of arriving at a proper material trajectory, where the total length of the flights are used, a new feed chute was selected. The simulation results indicated that if the height of the flights is increased from 1.60 to 2.26 m and the slope is increased from 45 to 48 degrees the material arrive at the first 0.48 m of drying chamber. In this manner, the unused part of the drying chamber decreases from 59% to 36% of the length. After installation of the new feed chute, during a period of three months the throughput increased by 36 t/h.

Jan 1, 2018

By Sanchita Chakravarty, Sumantra Bhattacharya, Divya Jyoti, A. K. Mukherjee, Soni Jaiswal

"Release analysis is independent of collector and frother dosage and type, but it is primarily influenced by the degree of liberation or “state of release of the sample”. The shape of release curve is an indication of the degree of liberation. This paper briefs about the effect of reagent combination, particle size and surface characteristics on the release analysis of difficult-to-clean LVC coal.Release analysis of three LVC coal fines obtained from two different coalfields of India was carried out at three different size levels such as -0.5mm, (-0.5+0.1) mm, and -0.1mm. The collectors used were n-dodecane and commercial diesel oil. Incomplete liberation of coal fines even at a size of -100µm, corroborated by photomicrographs of ROM and clean coal macerals, in a great measure reduced the flotation-based cleaning potential of the fines. FESEM images of fines reveals that the adherence of ultrafine onto the surface of relatively coarser particles reduced the clean coal recovery. The results obtained also appear to be coal, reagent combination and, particle size and particle surface specific. Only one coal indicated the liberation as is usually expected for -0.1mm particles with a reasonable yield of 65% at 18% ash. INTRODUCTION Froth flotation has a long history of being used to treat coal fines. Coal flotation is considered to be difficult, if the percentage of Near Gravity Material (NGM), i.e. essentially locked particles, in flotation feed is >10% [Aplan, 1993], which is usually the case with all the coking coal fines in India. The fines are rich in vitrinite, so valuable for coking coal. Unfortunately, there appears to be no standard procedures to determine the separation efficiency of froth floatation. Release analysis proposed by C.C. Dell in 1953 [Dell, 1953], aimed to determine the ultimate floatability of coal. Several other techniques had been proposed but release analysis technique has been considered to be a vast improvement over the batch flotation process [Forrest et al. 1994]."

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 Yimin Zhu

This paper introduces the sixteen mappings and rules of mineral flotation and the subgroup, period etc in periodic table of chemical element to provide mineral flotation workers to refer in theory and practice research. the nine mappings and rules of mineral flotation and the subgroup, period are Saline minerals including the first main groups and collectors of aliphatic acid and aliphatic amines, Minerals including the second main group elements and collector of aliphatic acid, Hydrated ion of the second main group elements and quartz flotation, The floatability of oxidized minerals including the four main group elements, Organic acid including the fifth main group elements and wolframe, tin flotation collectors, The floatability of sulfide minerals including the fifth main group elements, Inorganic compounds including the seventh main group elements and mineral flotation regulator, Oxidized minerals including the forth Subgroup elements and organic flotation agents with phosphorus and arsenic, Oxidized minerals including the fifth subgroup elements and organic floating agents including the fifth main group elements, Minerals including the first subgroup elements and CN-, Sulfide minerals including the second subgroup elements and CN-, The effect of the highest N-valency inorganic acids or salts including p area elements of the third period in mineral flotation, Oxidized minerals including transition elements of the forth period and 3# flocculating agent, The floatability of minerals including elements of the sixth period, Element area of generating compositions and the collecting theory of mineral flotation and so and. Keywords: mineral flotation, periodic table of chemical element, subgroup, period, regulator, coordination chemistry

Sep 1, 2012

By Guanghua Ai, Xiong Huang, Huashan Yan, Ting Li, Tingsheng Qiu

"Cyanide tailings of gold and silver concentrates contain considerable quantities of copper-lead-zinc sulfide minerals that can be recovered. However, the strong inhibition effect of cyanide often makes it difficult to recover these sulfide minerals effectively. In this research, a sample of cyanide tailings was investigated based on the principles of process mineralogy; activating flotation tests were carried out for the target minerals in the tailings, and the activation mechanism of the activator and its influence on the target minerals were investigated by Fourier transform infrared spectroscopy (FTIR). Mixed flotation of copper and zinc was carried out using QJ-01, a combined agent containing sulfite, as the activator of copper and zinc minerals, and ammonium dibutyl dithiophosphate (ADD) and butyl xanthate (BX) as the combined collector. Copper concentrate was obtained from the mixed concentrate by using a combined inhibitor of sodium sulfide and zinc sulfate to inhibit the zinc mineral. Zinc concentrate was extracted from the copper tailings by using copper sulfate as the activator and BX as the collector. The flotation test yielded copper concentrate with a grade of 22.56% and recovery of 76.96%, and zinc concentrate with a grade of 42.56% and recovery of 82.29%, which shows that comprehensive recovery of the sulfide minerals – copper and zinc –from the cyanide tailings was realized. The FTIR analysis showed that CN- was chemisorbed on the surface of chalcopyrite and sphalerite following cyanide treatment, while the combined activator QJ-01 containing sulfite reduced CN- into SCN- and weakened the complexing ability of CN- with metal ions on the mineral surface, thus achieving a good activation effect on chalcopyrite and sphalerite. The results of this study can provide practical guidance in increasing the resource utilization ratio of cyanide tailings in gold mines, and thus contribute to alleviating environmental problems caused by stockpiling cyanide tailings. INTRODUCTION Cyanidation, the most widely used technology for extraction of gold, has several advantages such as high recovery, process maturity, low cost, etc. According to available data, the annual discharge of cyanide tailings from China's gold mines exceeds 20 million tons (Li et al., 2011). Lower grades of exploitable gold ore entail increased discharge of cyanide tailings. Huge quantities of cyanide tailings are regarded as waste and stored, resulting in significant wastage of land resources. Moreover, residual beneficiation reagents, cyanide ions, and heavy metal ions in cyanide tailings cause severe pollution of water and land (Laitos et al., 2013; Donato et al., 2007; Mudder and Botz, 2004). In addition, cyanide tailings often contain valuable elements such as gold, silver, copper, lead, zinc, sulfur, and iron, which, if not recycled, would result in considerable wastage of resources. Hence, it is imperative to study the reduction and safety of cyanide tailings, and the mineral resources present in them."

Jan 1, 2018

By F. v. d. Meer, G. Kretschmar, T. Mütze, T. Leißner

"Dynamic air classifiers separate particles in a gas flow due to different particle trajectories utilizing differences in the settling velocity of particles as characteristic property for separation. The present contribution takes a close look at the separation of heterogeneous mixtures, in which valuables and gangue minerals show significant differences in density. The focus was on a moist iron ore sample, which was characterized in terms of mineralogy, grain size distribution, and particle size distribution. The material was classified at a cut size of 45 µm and at feed moistures between 0 and 6 wt.-%. Additionally to standard characterization techniques, the moisture of both products was measured as well as the yield of fines as product fraction in a corresponding processing plant. In addition, an automated mineral liberation analysis (MLA) provided information of the enrichment and segregation of individual mineral phases in the products. The MLA of the classification products reveals a selective comminution of the mineral phases and especially on overmilling of the valuables. For the first time, the separation of individual mineral phases has been assessed and compared to the classic assessment of classification processes by means of particle size analyses. KEYWORDS Dynamic classifier, segregation, MLA, selective comminution INTRODUCTION Dynamic air classifiers separate particles in a gas flow due to the different trajectories of the particles. The result of such a separation process depends on the gas throughput of the classifier, the dimensions, design and rotational speed of the deflector wheel, as well as the state of dispersion and thus the geometry of as well as the turbulence and interparticle interactions in the separation zone. Air classification of moist feed materials can be divided into several sub-process (Leschonski, 1977; Mütze et al., 2016): - dosage of the feed material, - dispersing the solid feed material into a gas stream, - feeding the dispersed material into the classification zone by pneumatic conveying, - drying of moist particles during pneumatic conveying, - separation of coarse and fine particles, and - separation of fine particles from gas."

Jan 1, 2018

By Mingfei He, Xianyang Qiu, Hongling Wang, Yude Gao, Qingbo Meng, Xiaoping Xu, Hao Bu, Guosheng Wang

"By the “HGMS-gravity separation-Flotation” combined technology, a Ta-Nb-Sn concentrates with the grades of Ta2O5 10.00%, Nb2O5 9.13% and Sn 42.62% at the recovery of 44.73% , 9.13% and 14.62% respectively , a Li concentrate with Li2O 3.11% at the recovery of 51.83% and a feldspar product are obtained. All the value elements are recovered. INTRODUCTION Tantalum and niobium widely used in electronics, atomic energy, aerospace and chemical industries with the advantages of high melting point, good ductility, low vapor pressure, strong corrosion resistance and high thermal conductivity are important strategic resources which occupy a special position in rare metals (Crockettand, 1993; GAO and Zou, 2004; LI and HUANG, 2012). China's tantalum and niobium resources are poor, and most of them are low grade, fine grain size, complex composition, and polymetallic associated with refractory mineral resources (GAO and Qiu,2013; Liang and Li, 2016). The Yifeng Lion Ore containing lithium and other rare metals (tantalum, niobium and tin) is an important lithium polymetallic deposit in China Jangxi province. While extensive previous studies have settled on the recovery of lithium minerals by flotation only for the extremely low grade of Ta, Nb and Sn. The regular gravity concentration is used, and the recovery of tantalum niobium is low. This paper sets out to investigate a combined flowsheet of “high gradient magnetic separation (HGMS),-gravity separation-flotation” to effectively comprehensively recover the Li, Ta, Nb, Sn and the feldspar resources in the Yifeng Lion Ore.ORE PROPERTIES Chemical analysis The run of mine comes from Jiangxi Yifeng Lion ore. The main elements of the ore chemical analysis results shows in Table 1. From Table 1, the grades of lithium and rubidium are relatively high, but the grades of tantalum and niobium are lower than the industrial grade; feldspar with high content of potassium and sodium and low content of iron can be used as high-quality ceramic raw materials."

Jan 1, 2018

By Georgios N. Anastassakis

"The depletion of the high-grade chromite ores and the inefficiency of the gravimetric methods to process fine particles has shifted the industrial and research interest from gravimetric separation methods to flotation. However, the response of the minerals to various flotation schemes is not clearly established. In this work, the physicochemical behavior of chromite and olivine is studied using a fatty acid collector.The minerals used were from Vourino area (Kozani, Northern Greece). Macroscopically pure samples of chromite and olivine were selected by hand picking, crushed and subsequently ground to the required size. Each sample was then submitted to panning and magnetic separation for the removal of impurities. The mineralogical and chemical analysis of the purified samples revealed the following: a) The purity of chromite was 95% while the minor constituent was mainly magnetite. Its chemical analysis was: 12.50% Fetot, 2.50% SiO2, 54,54% Cr2O3, 9.31% Al2O3, 0.47% CaO, 13.10% MgO. These analyses show that Cr3+ has been substituted by Fe3+ and Al3+ as well as Fe2+ has been significantly substituted by Mg2+. b) Forsterite is the main constituent of olivine either as pure forsterite (Mg2SiO4), which is the prevailing form, or as iron-forsterite [(Mg,Fe)2SiO4] in less amount. Chrysotile, which belongs to the serpentine group, was also detected at a percentage of 10-15%. The chemical analysis of olivine was: 36.90% SiO2, 0,53% Cr2O3, 7,43% Fe2O3, 0.72% Al2O3, 0.91% CaO, 47.00% MgO, 6.02% LOI.The electrokinetic behavior of the minerals was studied in a electrophoretic mass transport equipment Model 1202 of Micromeritics. The reagents used were sodium hexa-metaphosphate of commercial grade and sodium oleate."

Jan 1, 2003

By F. K. Ikumapayi

An approach to environmental sustainability and improved process economy, in sulphide minerals production is recycling of process water in flotation of complex sulphide ores, although the chemistry of process water may be a critical issue to flotation efficiency. The influence of major components of calcium and sulphate ions in process water on xanthate collector adsorption and flotation response using pure chalcopyrite, galena and sphalerite minerals were investigated by Hallimond flotation, zeta-potential measurement, FTIR and XPS spectroscopy studies, while bench scale flotation tests were also carried out using complex sulphide ores. The impact of the species in flotation was comprehended using deionised water, tap water, process water and simulated water containing equivalent amount of calcium and sulphate species in process water. Hallimond flotation results showed a decrease of chalcopyrite and galena recovery in process water and also in the presence of calcium and sulphate ions in both deionised and process waters, whereas sphalerite does not respond to flotation. The adsorption of calcium and metal ions but not sulphate ions on the minerals is evidenced by zeta-potential data. FTIR and XPS studies revealed the presence of surface oxidized sulfoxy species and surface calcium carbonates on chalcopyrite in the presence of process water and water containing calcium ions, surface oxidized sulfoxy and carbonate species on galena in the presence of deionised water, process water and water containing calcium and sulphate ions, all at flotation pH 10.5, and these surface species influenced xanthate adsorption. The presence of surface oxidized sulfoxy and carbonate species at the sphalerite flotation pH 11.5 were seen in the presence of deionised water, process water and water containing calcium and sulphate ions, but the surface species does not influence xanthate adsorption. Bench scale flotation using two different complex sulphide ores showed that chalcopyrite, galena and sphalerite recoveries are better in process water than tap water. The studies showed that the process water can be recycled in flotation with no detrimental effect on grade and recovery of sulphide minerals. Keywords: sulphide minerals, flotation, zeta-potential, FTIR, XPS

Sep 1, 2012

By Francisco Cubillos, Jorge Menacho, Cesar Gomez, Juan Rodríguez

Mineral flotation is the most used process to selectively separate particles of one or more minerals of interest. The process uses natural or induced hydrophobicity to collect particles on the surface of rising bubbles through collisions and formation of bubble-particle aggregates. Flotation machines must keep particles in suspension and well distributed, while at the same time, disperse a mass of air into a population of small bubbles. The efficiency of the separation depends primarily on the characteristics of the bubble population generated in the machine and its distribution and flow throughout its volume. The formation and separation of bubble-particle aggregates create two zones, with strong interactions between them, and with markedly different hydrodynamics conditions. A model describing two-phase hydrodynamics of the continuous and dispersed phases (frother solutions and bubbles, respectively), moving along the whole unit, is proposed. Bubble populations are characterized at the formation stage including the effect of the presence of frothers. Flow through the aggregates formation zone, where bubbles move freely and are closely spherical, is modeled using drift-flux analysis. In the aggregates separation zone, bubbles initially pack maintaining a water layer thick enough to prevent capillary forces to affect their shape. As water drainage proceeds, bubbles deform, capillary channels form, and a network of channels with a diameter size distribution develops; channels become narrower (permeability is reduced) as the distance from the interface increases. Froth hydrodynamics is characterized using models originally developed to describe unsaturated flow through porous solid particle beds. Effects of hydrostatic pressure are considered.

Jan 1, 2014

By F. Burat

At the present time, methods of mining and coal preparation produce tones of coal fines. The removal of water from these fines is necessary for economical and technological reasons. Supplementary processes that utilize different physical and chemical methods have been developed to in-crease the productivity of mechanical dewatering processes. Researches have shown that chemical reagents used along with conventional systems diminish moisture and increase the capacity and the yields of the dewatering method. In this study, the parameters of the vibrating screen (incline, frequency, feeding rate and screen size), the effects of the application of additional vertical mechanical vibration and surface active reagents (CTAB, SDS, Umectante B-70 and Kerosene) were investigated. At the end of the optimization experiments, 61.0% moisture was decreased to 42.3%. By keeping optimum conditions con-stant, the experiments have been conducted to determine most effective reagent. 41.2% moisture has been obtained with 5 g/t CTAB at the normal pH of the pulp, which were 7.25. By using vibrating screen with combination of the vertical vibrating mechanism, CTAB gave the best result of 40.7% moisture. Finally, the effect of increased surface area of the screen has been investigated and de-creased the moisture level to 38.7%.

Jan 1, 2014

By Sashnee Raja, Mehdi Nemati, Ashley Sissing, Susan T. L. Harrison

"Extreme thermophiles, operating at 65 - 90°C, are finding increasing application in biohydrometallurgy These microorganisms have the advantage of exhibiting better oxidation kinetics in terms of reaction rate and extent of mineral solubilisation. These extreme thermophiles are Archae, characterised by a different cell envelope structure perceived to provide reduced structural strength in comparison to bacterial envelopes, and customised metabolic pathways.The active tank bioleaching process, used for high rate leaching, is conducted in a slurry bioreactor. Here sufficient energy dissipation is required to ensure suspension of the mineral phase as well as to sustain high rates of gas liquid mass transfer. It is well known that subjection to hydrodynamic stress of sufficient magnitude may alter the physiological state of a range of micro-organisms through changed viability (ability of the microbes to grow), metabolic activity and integrity.In this paper, we report on studies carried out to quantify the ability of the extreme thermophile Sulfolobus to withstand the hydrodynamic stress environment generated at high pulp densities in the slurry bioreactor. Both a pyrite system (as a model system) and a chalcopyrite system (as an application) were studied. In laboratory reactor systems, the nature of biological responses to stress induced at high pulp density have been identified in terms of ability of the microbes to grow, their metabolic activity and rate of leaching and cell integrity. Critical operating conditions within the laboratory reactor are identified and the mechanism mediating reduced performance considered."

Jan 1, 2003