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By R. S. Wang

The flotation of pyrite which be pretreated by electrochemical ways under external controlled voltages in different pH is explored. The floatability of pyrite is increased indistinctively after being pretreated in acidic and xanthate environment; Whereas, it is increased obviously between 400~800 millivolt in alkaline and xanthate condition. The reason for higher recovery of pyrite is that oxida-tion reaction, which results in S0 and S02, takes place on its surface, and that ethyl xanthate is oxi-dized into dixanthogen. In the meantime, the kinetics and mechanism is also studied.

Jan 1, 2014

By J. Lampke

The superior characteristics of iron ore pellets compared with natural ore and sinter are well known. Due to the higher grade and bulk density they show improved transport and material handling properties. While charging blast furnaces with pellets an increased productivity is realized through pellet?s uniform structure and composition. The increased productivity is caused by a high permeable furnace burden with a decreased coke usage via fuel injection and oxygen enrichment. Therefore, a narrow pellet size distribution and a minimum content -6.3 mm are necessary (Meyer, 1980). The required pellet size distribution can be achieved on the one hand by screening the fired pellets after the induration furnace and recycle the undersized pellets. On the other hand it is possible to produce high quality iron ore pellets with a high degree of sphericity, the important narrow grain size distribution ranging between 9 to 16 mm with high green strength directly in the pelletizing device. To produce high quality green pellets, possibilities and knowledge about adjustments of the pelletizing device are necessary. The paper presents a classification of state of the art pelletizing systems in accordance with the advantages of the pelletizing disc and pelletizing drum in issues like adjustability, green pellet quality, the recycling rate and the space requirement. By a systematization of the influences on pelletizing the common reliance of objectives on influence like pelletizing moisture, disc inclination, rotational speed, mass flow and rim height are given. A variety of industry-proven examples are shown, too. Keywords: Pellet, iron ore, pelletizing, pelletizing disc

Sep 1, 2012

By M. M. Kulkarni1

Kaolin clay is used as a filler and pigment in various applications such as paper, paint, rubber, plastics, adhesives, ink and ceramics etc. Major mineral content in crude kaolin clay is kaolinite along with some accessory minerals as quartz, hematite, mica, feldspar, anatase, rutile, illemnite etc. The Fe and Ti bearing minerals play very important role in determining quality of the kaolin, as these minerals impart yellow, pink or darker color to the white kaolin. Conventional beneficiation methods used in kaolin processing are de-gritting, classification and sodium dithionite bleaching, which improves the optical properties of kaolin, wherein reduction of color imparting constituents such as Fe2O3 and TiO2 is marginal. In the present study, these coloring impurities are separated using selective adsorption of water-soluble polymers. Degritted kaolin samples after passing through 45 micron sieve is used in the study for selective flocculation by polyacrylamide based polymers. The effect of pH, zeta potential, and polymer dose on the reduction of impurities is studied. Analytical tools such as XRF, XRD, SEM, and TEM techniques are utilized and results are discussed in detail.

Sep 1, 2012

Low-grade ore bodies, increase in rock competency, finely disseminated valuable minerals in the ore bodies, ore variability and water scarcity are among the technical challenges faced by the mining industry. These challenges have increased the business risk, capital investment and operating cost of the mining projects. Since the last 20 years, many large-scale concentrators have been built to cope with the above-mentioned challenges. Comminution, especially the fine grinding is an energy-intensive process. For example, the ball mill has a limitation in the fine grinding regime where the energy consumption increases exponentially when the product size is below 45 µm. The industry has been seeking for solutions that have a minimum risk and total cost of ownership. The stirred milling technology such as the TowerMill is well accepted by the industry as it has demonstrated the attributes required for fine grinding. TowerMill is a matured technology that has been adopted since the 80s for regrinding duty. Recently, this technology was installed in secondary and tertiary grinding duty to prepare a finer feed to rougher flotation. Four units of TowerMills were installed in a magnetite concentrator in Western Australia in tertiary grinding duty. Recently, Nippon Eirich has conducted process performance evaluation on the TowerMill circuit. The outcome of the exercise had indicated that the circuit is consuming 3.4 kWh/t to reduce from 55 µm to 35 µm with a narrow product size distribution. The effect of operating variables such as the specific energy, grinding media size, mill content % solids and mill feed configuration on the grinding efficiency were evaluated at the plant scale. Furthermore, the scale-up methodology was validated. The scope of this paper includes the performances of TowerMill and the validation of scale-up methodology.

Jan 1, 2018

By F. Boylu

In this study, Ca-bentonite was subjected to a series of systematic hydrocyclone tests with the aim of developing separation procedures and in turn achieving optimum recoveries. In hydrocyclone tests, vortex and apex diameters and also feed pressures were investigated. In each hydrocyclone set, vortex diameter was kept constant while the other two parameters varied to produce bentonites con-centrates of various smectite contents. The separation efficiencies were evaluated based on the cation exchange capacity (CEC), particle size and swelling index. The detailed hydrocyclone tests showed that, upgrading of Ca-bentonites require procedures different from the bentonites reported in the literature. Sodium and mixed bentonites are easy- to-disperse and easy-to-separate whereas calcium types need to be scrubbed rigorously for disintegration. Scrubbing properties of ca-bentonite were investigated as a function of scrubbing time and percent solids by weight (PS). The scrubbing conditions at 700 rpm for 1.5 hours and percent solids of 30 % were found more effective for achieving a better quality bentonite. In addition to the parameters mentioned above, the effect of percent solids on hydrocyclone separation was also studied. Although Ca-bentonites permit studying at higher percent solids, increasing solids content of the pulp deteriorated the quality of the clean products. Application of an appropriate separation scheme enabled the development of a unique separation procedure involving stage wise scrubbing followed by hydrocycloning which yielded calcium bentonite concentrates with CEC of 90 meq/100 g and high swelling indexes of 12 mL from the original bentonite of 65 meq/100 g and 7.0 mL, respectively. These results indicate that upgraded bentonite products can be conveniently used in various diverse industrial applications including bleaching earth, desiccant, cat litter, paper etc.

Jan 1, 2014

By Luis Cáceres, Genny Leinenweber

"We have designed a planar perpendicular flow cell for electrochemical measurement of a mineral available as a fine powder. The working electrode consisting of mineral powder supported on a carbon paste surface as a 4 mm diameter disk, was concentrically positioned inside a vertical tubular reactor. The counter electrode was a 316L tube embedded in the body cell. The supportive media was a 1.2:1 mixture of candle wax and graphite powder respectively, which is a good electrical conductor. The concentrate electrode as a film attached on a carbon paste disk was prepared rubbing the surface carbon paste against dried powdered mineral. An Ag/AgCl 1 M KCl cell as a reference electrode was attached to the body cell by using a fast coupling fitting. A stable flow rate was achieved using a frequency inverter to drive the pump motor. The flow through the cell verified to be laminar due to the Reynolds number in the cell flow passage. Cyclic voltammetry from - 1200 a 600 mVSAgE were measured using a carbon paste with and without mineral attached to the surface. The main findings of this work were: a). Electrochemical measurement of mineral powder in contact with flowing samples was easily achieved using ground mineral. This is important where massive samples are not available. b). The voltammetric curve features of ground mineral coincided with reported data. c). The working electrode could be quickly replaced while maintaining very good reproducibility."

Jan 1, 2014

By M. J. Lottering

Gold deposits in South Africa are invariably associated with uranium bearing minerals. Although it is low grade uranium by international standards, averaging around 0.3 kg U3O8 per ton of ore, recovery of uranium as a by-product improves the overall economics of gold extraction. Moreover, the current high uranium prices as well as increased demand due to renewed interest in nuclear power provide significant incentives for dedicated uranium production. An understanding of the uranium leaching response to changes in operating conditions is an important first step to-wards optimisation of uranium recoveries. In South African acid leaching plants, uranium dissolutions higher than 90% are difficult to achieve, and the chemical origin of this limit is not clear. To study leaching behaviour, an important consideration is the mineralogical characteristics of the ores. Typically, a diagnostic leaching approach can be followed. In this paper, a mineralogy-leachability explanation is presented to rationalise the difficulty in exceeding 90% dissolution from low grade uranium ores on the basis of a simple diagnostic leaching method. It was found that brannerite was the main reason for the existence of a dissolution limit in Witwatersrand ore and that chemical liberation was more effective to increase end dissolution compared to physical liberation. The findings from these investigations will form guidelines for developing economically viable flow sheets for improved uranium recovery, at least in a South African (Witwatersrand) context.

Jan 1, 2014

By D. W. Feng

Thiosulfate leaching has been considered as the most promising alternative to cyanidation for the recovery of gold from ores. The chemistry of the ammonia-thiosulfate-copper system is complicated due to the simultaneous presence of complexing ligands such as ammonia and thiosulfate, the Cu(II)-CU(I) redox couple and the stability of thiosulfate in solution. However, acceptable gold leaching rates can be achieved by maintaining suitable concentrations of thiosulfate, ammonia, cop-per and oxygen in the leach solution. The leaching of gold in thiosulfate solution is an electrochemical reaction involving the oxidation of gold to gold thiosulfate and the reduction of Cu(II) to Cu(I). Previous studies have shown that the reaction rate of gold was much higher in the presence of am-monia thiosulfate than corresponding sodium thiosulfate. This indicates that cations may affect the anodic oxidation of gold in thiosulfate solution. The present study utilises electrochemical tech-niques to study the anodic oxidation of gold in thiosulfate medium in the presence of the different alkali metal and alkaline earth metal ions. It has been shown that the presence of the heavier cations such as potassium, calcium, and caesium enhance the oxidation of gold in thiosulfate solution. Leaching tests also indicated the improved recovery of gold from a sulfide ore with the addition of heavier cations. XPS results demonstrated that the binding energy for gold shifted to lower values in the presence of the heavier cations, indicating the ready formation of ion-pair with gold thiosulfate at the gold surface during adsorption.

Jan 1, 2014

By A. P. Das

Biomining technology focuses on achieving effective recovery of precious metals from their ores and concentrates using microbial techniques. Biomineral extraction of manganese from low-grade manganese ores using bioleaching was investigated in this paper. Five fungal strains were selected for screening of bioleaching of low-grade Mn ore collected from Sanindpur iron and manganese mines, Koira Sector, Keonjhar, Odisha, India. A fungal strain, Aspergillus niger was selected as it showed high efficiency of manganese leaching. Growth of the fungus was determined in terms of sbiomass dry weight and the final pH was monitored. The selected fungal strain was used for bioleaching of low-grade manganese ore of -150µm size particle size at 2 % pulp density with 2g/100ml sucrose concentration for duration of 20 days. About 60 % of Mn bioleaching was obtained with A. niger. The fungal species proved to be useful for manganese biomining.

Sep 1, 2012

By P. Braga, A. Chaves, S. França, A. Luz

"In Brazil, there are no official reserves of molybdenum, and the unofficial reserves are modest. Therefore, the molybdenum ore (molybdenite) produced as a co-product or by-product of emerald mining in the region of Campo Formoso, BA, has arisen as the only economic option. The flotation process is commonly used in Brazil for the recovery of molybdenite from emerald mining tailings, but it produces low-content molybdenite concentrates, thereby resulting in a product with low economic value. The molybdenite concentrate produced in Campo Formoso contains 83.5% MoS2 (50% Mo), which is less than the international standard product that contains > 90% MoS2 (54% Mo).This low value is due to the presence of talc, which is a naturally hydrophobic mineral that is also floated with the molybdenite during the flotation process. Separability studies were done in a Partridge-Smith cell using dextrin and quebracho as a molybdenite depressor in solution at different concentrations and pH values to produce a technical-grade concentrate (i.e., 90% MoS2). These basic studies were accompanied by measurements of the zeta potential and contact angle, which was determined by the capillary rise method. The results of these floatability studies were used in bench flotation tests, which were performed in a Denver laboratory flotation cell. A molybdenite concentrate of 93.4% MoS2 was obtained when dextrin was used at a concentration of 100 g/t."

Jan 1, 2014

By Ljudmil S. Grigorov, Eric Forssberg, Hanumantha Rao Kota, Robert J. Pugh, Lidia B. Alexandrova

"We have used the microscopic thin balance developed by Scheludko at al. (1970) technique to study the stability and interactions within the thin film between the silica surface and air bubble with (i) a long chain C10 amine and (ii) a cationic/anionic surfactant systems consisting of mixtures of a long straight C10 chain amine with long straight chain C8, C10 and C12 sulfonates. It was found that the mixed surfactants caused lower contact angles, lower rates of the thin aqueous film rupture and longer film lifetime, compared to the pure amine system.This behavior was explained by the initial strong adsorption of positively charged interfacial complexes from the mixed surfactant system at the air/solution interface followed by adsorption at the silica interface. It was also shown that the chain length compatibility between the anionic and cationic surfactants controls the strength of the interfacial complex, determining an inhibition in the thin film rupture and dewetting of the film. The rupture mechanism was explained by an earlier established heterocoagulation mechanism between the positively charged air/solution interface and the solution/silica interface which remained negatively charged. The formation of the interfacial complex at the air/solution interface was confirmed by using surface tension data."

Jan 1, 2003

By J. A. Venter

Mineralogical studies indicate the Pt-Pd-Bi-Te class to react poorly on the flotation stimuli and indications are that these minerals are slow floaters. However, recent studies performed on a number of minerals from this class indicated strong interactions with potassium ethyl xanthate resulting in the formation of dixanthogen (only one of several xanthate species). The poor flotation response is not a result of poor interaction of xanthate with the surface. It is proposed that the oxidation products of sulfides in the process water interact with the PGM surface. To test this, the effect of thiosulfate (an important oxidation product of sulfides) was investigated by employing electrochemical measurements and FTIR spectroscopy. The electrochemical investigations indicate no strong effect of thiosulfate on the interaction of xanthate with the minerals surface as well as the reduction of oxygenthiosulfate is likely not responsible for the poor flotation response of these minerals in industrial plants.

Jan 1, 2014

By Peter Kondos

The need for a sustainable development of ore deposits makes it imperative to be innovative and mindful in creating an economically and environmentally viable operation, while maintaining a good working relationship with the various stakeholders involved in developing and operating a large and complex mining project. This is becoming immensely important as gold ore deposits are becoming more mineralogically complex along with lower grades presenting both metallurgical and environmental challenges that need to be addressed in mitigating risks and improving project economics. This paper presents Barrick?s approach to development of strategic technologies for our long-term sustainable growth through conversion of valuable resources into reserves for both our green-field development projects and the expansion of our existing mining operations. Some of the key strategic solutions, including mineral processing, metallurgical and energy technologies, developed by Barrick and their impact on some of our complex gold and copper-gold ores will also be discussed in this paper. Keywords: gold ores, copper-gold ores, processing, breakthrough technologies

Sep 1, 2012

By S. N. Titkov

Flotation of halite?new, recently begun to be developed method of processing water-soluble minerals. In the paper the results of studies of the new directions of the application of halite flotation are represented. Studies on the flotation separation of halite and sylvite in the salt solutions of different composition, showed the possibility of the halite flotation realization not only in the carnallite brine (content of salts: MgCl2 25.5% ~ 26.0 %, chlorides of potassium and sodium 5.5% ~ 6.0%), but in the sylvinite brine, which contains 10.5% ~ 10.8% KCl and 20.5% ~ 21% NaCl. On the basis obtained results are carried out experiences on the halite flotation from samples of the converted products of sylvinite ores by flotation method and by the method of the electrostatic separation. It is shown that in all cases it is possible to accomplish effective and selective recovery of halite. The halite recovery into the foam product of flotation makes 80% ~ 90% with an increase in the content of KCl in the cell product of flotation in comparison with a composition of flotation feed: - from the product after the electrostatic separation of ore ? from 76% KCl to 95% ~ 97% KCl; - from the small fraction of ore (- 0.25 + 0 mm) ? from 30% KCl to 60% ~ 64% KCl; - from middlings (intermediate products) of sylvite flotation from 16% ~ 31% KCl to 45% ~ 80% KCl. An increase in the molecular weight of alkylmorpholines increases the selectivity of the flotation separation of halite and sylvite. Halite recovery from small size fraction of ore or/and middling of sylvite flotation with the sub-sequent joint filtration halite product and tails of sylvite flotation allows to reduce considerably expenses for manufacture potash chloride from Pilot-industrial tests for the first time confirmed the possibility of the effective halite flotation in the saturated solutions of chlorides of potassium and sodium (sylvinite brine).

Jan 1, 2014

By Bianca Foggiatto, Marcos Bueno, Rajiv Chandramohan, Eddie McLean, Greg Lane

"With the increasing depletion of high-grade ore deposits, smarter mineral processing solutions are required to achieve sustainable and economic methods for mining and processing low-grade deposits. In order to make the treatment of low-grade deposits economically viable, large quantities of rock need to be mined and processed. The associated infrastructure costs (power, water supply, accommodation and support services, waste storage) result in a substantial penalty on the project, from both capital and operating cost perspectives. As a consequence, the challenge for the mining industry is to overcome the associated rise in energy and water consumption as well as increased project complexity when processing large amounts of low grade ore. Ore sorting technologies have been used for many years, predominantly on small projects, enabling the upgrade of marginal ores. Several sorting methods based on characteristics including specific gravity, radiometry, colour, particle size, grade and other detectable physical characteristics have been employed. The challenge for large low-grade ore bodies is to crush and sort at coarser rock size in order to minimise specific energy consumption in comminution and to reduce waste disposal costs. For large projects, the understanding of the economic impact of ore sorting is limited. The economic drivers include plant head grade improvement; sorting infrastructure capital, operating and maintenance costs; waste material handling and other environmental costs related to waste disposal. This paper analyses the economic impact of ore sorting in a large mineral processing operation. The focus of the analysis is to compare NPVs for a circuit including screening and ore sorting stages. A project for processing an Australian copper sulphide ore is considered as an example for this study."

Jan 1, 2014

By S. J. Dai

The cadmium and cyanide are main poisonous components in cyanide electroplating cadmium waste water of an electroplating plant in Shenyang. The content of cadmium is about 26 mg/L and the content of cyanide is about 11.782 mg/L in this waste water. The main form of cadmium and cyanide are ions which are Cd2+and CN?. Because the cadmium and cyanide exceeded the standard seriously, the waste water must be disposed before it discharges. The microbiological method of treating heavy metals in wastewater has many advantages. For example, it has a fast adsorption velocity, high processing efficiency, wide range of pH and temperature, few invest, low running cost, no the second pollution and so on. At the same time, the CN? could be degradated by some microbiology. The physical nature, the chemical nature of Bacillus mucilaginosus, the adsorbing condition and adsorbing regular of Bacillus mucilaginosus to cadmium in the wastewater are studied by using Bacillus mucilaginosus as adsorbent removing cadmium from electroplating wastewater. The experimental results show that the adsorbing rate of cadmium is over 92%, under the room temperature(about 25?), stiring revolution in adsorption being 800 r/min for 30 min, pH being 5 , the bacteria being cultured after 5d with the biomass of Bacillus mucilaginosus 40g/L (wet weight). The mechanism in biosorption process of Bacillus mucilaginosus to cadmium is analyzed and discussed by TEM , Zeta potential,and infrared spectroscopy analysis. The results showed, the chemical involving is main adsorbing form, while electrostatic attraction, ions exchange, hydrogen bonding and Van Der Waals force are concerned cooperatively. ?NH2 ?, ?C=O?, ?C=O?NH?CH2, ?CH3, ?OH are main adsorbing groups. At the same time, the floatablity of removing cyanide by Bacillus mucilaginosus is explored.

Jan 1, 2014

By B. Csoke

As opposed to large household appliances, in the processing of which dissambling has an important role, this possibility is pushed into the background as the size decreases. The practicable solution is physical liberation of the used small electronic household devices (by comminution) and separation of the liberated components according to their physical properties. In the first phase of the experimental work the structural/material composition of the typical products (mixer, kitchen robot, hair dryer, coffee machine, iron, bread toaster, vacuum cleaner, oil fryer) was determined. In the second phase a physical liberability test for each appliance using a rotary shear/shredder for crushing and a hammer shredder for milling was carried out. In the third phase the experimental separability tests using an air classifier and a shaking air table, as well as an eddy-current and an electrostatic separator were performed. In the present paper the results obtained using the air classifier and the electrostatic separator, are reported. To follow the life of a grain a new methodological procedure was elaborated. The particle size fractions after comminution were sorted into material fractions (copper, aluminium, plastics, etc.), then separated, and finally the recovery of the material components in the products were determined. Furthermore, the joint separability was investigated from two points of view: 1) for grain fractions and 2) for each waste appliance. According to the tests carried out so far, it was established that it is reasonable to form appliance groups by selection (e.g. mixer, iron, bread toaster and similar appliances form the first group, while the sandwich oven,

Jan 1, 2014

By Nikkam Suresh

Dense medium cyclones have been in use for washing coarse and small coals for more than 50 years. There have been modifications in its design and today these units have become indispensable for washing of Indian coals possessing difficult washing characteristics. About 53 percent of the Indian coals (coking and non-coking) are being washed in jigs, about 38 per cent are washed in dense medium cyclones while the remaining 9 per cent is treated in other units like Barrel Washers, Heavy Media Baths and Drum Separators etc. The present paper deals with the attempts made for design of industrial Dense Medium Cyclones for enhanced coal recovery. Two industrial units of 500 mm diameter and 650 mm diameter were designed with their washing capacities being 200 m3/hr and 350 m3/hr, respectively. The results of the pilot tests conducted on 500 mm cyclone treating very high Near Gravity Material coals crushed to -3.0+0.5 mm gave an ash reduction of up to 19.5 percent with the new design i.e., from a feed ash of 34.5 percent to 15.06 percent in clean coal with an appreciable yield of 45 percent in one stage.

Sep 1, 2012

By Q. J. Liu

The flotation circuit and the reagents of the all-sliming flotation about low grade and hard operation on zinc oxide ore are researched in the paper. The results indicated that there are many types of zinc minerals in this ore, and the composition is very complex. They include hemimorphite, smithsonite, hydrozincite and so on. The ore is seriously sliming. In light of the ore properties, three kinds of flowsheets have tested. They are gravity concentration (cleaning tables), flotation, combined process of gravity concentration and flotation. The test showed that the recovery of zinc is only 17.08% in the gravity separation. In combined process of gravity separation and flotation, the recovery of zinc concentrate is close to 70%. But the flow-sheet is complex and hard to control in the production. The floatation circuit is feasible. In the test, it pay attention to investigate the new combined reagent which is used in selective all?sliming flotation process. The effects of slime are eliminated by the multi-loop treatment of middling. In flotation, the final recovery of concentrate is 88.76%; the grade is 29.50%. The recovery of physical ore is 93%; and the recovery of -10mm fraction is more than 65%.

Jan 1, 2014

By Duong Huu Hoang, Nathalie Kupka, Urs A. Peuker, Martin Rudolph

"The froth ability, froth stability and the froth structure are strong influences in flotation process i.e. on water recovery, bubble size, entrainment of gangue particle, flotation rate constants, grade and recovery. The labscale flotation of rich apatite ore with a high mass pull leads to significant changes in pulp and froth properties over time. The froth stability decreases with increasing the flotation time. These changes can be related to different solid contents, reagent concentration, froth heights and bubble size distributions. This study presents the results from froth studies and discussions on the particle size of fully liberated silicates and degree of entrainment based on automated mineralogy size-by-size analysis. The change of entrainment in a rich apatite ore batch flotation with time will describe more precisely by measuring froth properties using a Dynamic Foam Analyzer. It is concluded that the degree of entrainment is not only dependent on particle size but also the pulp density due to its effect on particle settling and also froth properties in varying resistance to particle drainage. Furthermore, entrainment models are applied to predict the effect of size, flotation time on entrainmentINTRODUCTIONFroth flotation belongs to the group of heterocoagulation separation techniques. Froth flotation is classically divided into two active zones, the pulp zone (where particle collection occurs) and the froth zone. A schematics drawing of the interaction between both zones is plotted in Figure 18 (Yianatos and Contreras, 2010). In froth flotation, the collision probability in the collection zone is governed by the physics of the process or hydrodynamics (Wills and Finch, 2016). The true flotation event in the pulp occurs when the hydrophobic valuable mineral particles collide with bubbles and formation of a stable particle-bubble aggregates moving upwards against gravity to the froth phase (Yianatos et al., 2009)."

Jan 1, 2018