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By David Morrow

Fly ash is a by-product from coal-fired power stations that is captured from the exhaust gas stream by electrostatic precipitators (ESPs) or bag houses. It is mainly derived from the inorganic components in coal but also contains residual carbon from unburnt fuel (measured as LOI). In the past, nearly all fly ash was sent to landfills or tailings ponds by power generators but this trend is quickly changing due to landfill costs, sustainability requirements and the inherent value in correctly processed fly ash. The main property that makes fly ash suitable for recycling is its use as a pozzolan. Pozzolans exhibit cementitious properties that make them suitable for partial cement replacement, and that can have beneficial properties for concrete mix designs. Fly ash can be used to replace up to a third of the of the Ordinary Portland Cement (OPC) requirement. Suitable fly ash nearly always requires the removal of the less reactive coarser fraction from the finer fraction. Due to the pozzolanic nature of fly ash, it must be processed dry and separation is normally required at 45 micron. In response to the increasing demand from a range of dry classification applications, Metso purchased an established air classification technology suitable for both mining and construction applications. The classifiers intelligent design efficiently utilizes the air flow which keeps power requirements low whilst including a scrubbing/recirculating function within the classifier that allows extremely efficient separations even at very fine sizes. This technology is of global interest to Fly Ash processors, but should be of particular interest in India which is both the second largest cement producer in the world as well as producing 80% of its power from thermal sources. This paper is intended to give a brief overview of fly ash and requirements for use as a pozzolan, air classification of fly ash and a case study from an established and experienced fly ash producer. Keywords: air classifier, fly ash, pozzolan, fineness, cement, cholla, salt river materials group

Sep 1, 2012

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 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 C. Perez

In mineral processing plants it is important to estimate rock composition, size and grindability to improve control of the grinding process. It is well known that variation in ore grindability and size distribution directly affects mills power consumption and throughput. This paper extends a general machine vision approach for on-line estimation of rock mixture composition using color information. Our proposed rock lithological recognition method requires the following steps: division of each image into sub-images, color feature extraction using the Binary Quaternion-Moment-Preserving thresholding technique (BQMP) and support vector machines (SVM) for classification. The BQMP thresholding technique splits the image in two and chooses representatives of each half using the histogram as features. The statistical parameters of the color data can be expressed using the quaternion moments into the representatives. This method can be recursively applied to the sub-images, obtaining 5x2n features in n iterations. Once the feature vector has been computed, each vector is assigned to one of three classes using a classifier. The method was tested on a database containing 20480 sub-images (64x43 pixels) of five ore types as follows: massive sulphide (MS), disseminated sulphide (DS), net textured (NT), gabbro (G), and peridotite (P). These ore types were assigned to three grindability classes: soft (MS), medium (DS and NT) and hard (G and P). The database was divided in 2 subsets: 15360 sub-images used for training and cross validation and 5120 sub-images used for test. The classification accuracy was compared with a method previously published based on a mixture of principal components analysis (PCA) for color, and wavelet texture analysis (WTA) for texture feature extraction. WTA-PCA approach reached a 76% accuracy in test while our BQMP method reached 90% of classification accuracy using only color features. Experimental results show that our proposed method yields excellent results compared to previously published results. Keywords: rock classification, lithological classification, grindability estimation

Sep 1, 2012

By M. Mirnezami

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

Sep 1, 2012

By Abhilash

Different methods of utilizing refractory bauxite and disposing red mud are practiced throughout the world, but none of them are known to be environmentally innocuous due to the complexity and /or high cost, and none has been found to be feasible on an industrial scale. Under these conditions, the use of bioleaching process seems promising. The present study emphasizes on the isolation of native extremophiles from the source Indian bauxite and red mud, with their detailed cellular and physio-chemical, and biochemical characterization. These organisms were tested for their ability to thrive in physically or geochemically extreme conditions. The gram positive capsule rich mesophiles and thermophiles were tested for removal of gangue minerals from the bauxite and red mud samples. Keywords: refractory bauxite, red mud, extremophiles, bio-beneficiation, gangue

Sep 1, 2012

By A. S. Choudhary

Most of the coal reserves in India are of drift origin and have very poor washability characteristics and a high level of near gravity materials. At least 30 new coal wash plants are expected to be set up in the next 5years.In such a scenario, adequate sampling followed by sink float test work for washability analysis becomes very critical for designing these new plants. For coal sampling purpose, stipulations of different standards are sometimes formidable and on the border of ?impracticality?; sometimes are self contradictory in terms of gross sample weight vis-a-vis minimum number of particles required in each size fraction and in each relative density fraction and also the minimum mass in the latter. Validation of the generated data is another important aspect of washability analysis. These issues can easily be addressed by using straight forward mathematical relationships, well known RR plots and by using simple MS Excel tool, etc.

Sep 1, 2012

By Alex Joseph

A tertiary amine containing polyamine in its back bone was grafted to exfoliated graphite oxide by means of a series of chemical reactions.The synthesized amine functionalized polyaniline grafted to exfoliated graphite oxide (EGAMPANI) was characterized using various techniques such as, FTIR, TGA, Raman, and X-Ray diffraction.The synthesized EGAMPANI was blended with carbon paste electrode, and used to study the response of Hg2+ in acetate buffer solution.Preliminary analysis showed that the anodic current intensity using the EGAMPANI modified electrode was higher during a potential sweep and 10-4 M concentration of mercury could be detected which could be improved to 10-6 M using anodic stripping voltammetric technique. Keywords: metal sensor, exfoliated graphite oxide, functionalization, polyaniline

Sep 1, 2012

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 Sumantra Bhattacharya

The per capita energy consumption in India is 510kgoe/year, the global average being nearly 1818kgoe/year. Correspondingly low is the per capita CO2 emission at 1.25t against the world average of 4.39t.65-70%, at times more, of India?s power generation from about 190,000 MW installed capacity, is however coal fired.India therefore has to secure diversified sources of energy and solar power is increasingly being looked as the real alternative to the existing over dependence on coal. To ensure sustainable solar power it is essential to secure its raw material base that is ?silica?, hitherto considered as ?minor minerals?. That calls for immediately addressing the issues of land availability, solar power cost, developing a dynamic inventory of silica containing minerals, appropriate processing technology and strong regulatory framework for sustainable mining and processing of all silica rich minerals. Keywords: silica, silicon, Thar, power generation, India, quartz, solar power

Sep 1, 2012

By C. S. Gundewar

Indian National Steel Policy envisages ambitious three fold rise in steel production by the year 2020. This paper covers the iron ore industry in India which cater to the need of iron ore requirement of Indian iron and steel sector as well as export commitment in addition to addressing the industry?s key concern to attain the same. The main contents are (i) resources and its exploitation; covering status of exploration, reserves and resources, province wise occurrences, distribution, nature of mineralization and generation of fines, etc ; (ii) use of iron ore in iron and steel making, covering physical and chemical requirements for pig iron and sponge iron production; (iii) ore characteristics and beneficiation practice in vogue; (iv) projected steel demand and requirement of quality iron ore and provision thereof; (v) recovery of iron values from in situ low-grade ores and stacked fine rejects (-10/-6 mm) inclusive of slimes (-0.15 mm) from tailing ponds; (vi) agglomeration of fine concentrates preferably by pelletization; (vii) measures to augment iron ore availability for future requirements.

Sep 1, 2012

By M. Bhartia

India is the 5th largest producer of steel in the world and is slated to produce more than 180 Mt by 2020. Expectedly about 50 % of this would be through the Blast furnace route and the rest through Sponge iron / DRI route. Considering that there will not be any major change in iron making technology by that time, the Blast operation would require lump ore (10-40mm) with around 64% Fe grade and sinter fines (<10mm) with 60% Fe (min) as its feed. DRI process would need calibrated ore of size 5-18 mm as the most suitable size of feed. It is also expected that of the total requirement of ore for the DRI route a significant part would be DRI pellets. In India, there is considerable debate going on regarding the technology to be adopted for the processing of iron ore and there is a lack of clear consensus. The above scenario indicates that the processing requirement of iron ore in the country would involve both washing technology as well as beneficiation technology. CDE Asia Ltd is in the forefront of iron ore processing in the country and the experience gained by the company over the last few years of functioning has led the company to believe that route to be adopted depends on the end product requirement and the starting grade of the feed. Keeping in mind the nature of the feed required for the Blast furnace & DRI operation; it is obvious that good washing technology would be highly beneficial to the iron ore industry. Depending on the grade of ore available the limits of washing will be decided and equipment for lump ore beneficiation such as jigs could be incorporated into the washing circuit. Scrubbing of ore either before washing or selectively scrubbing the lumps could be necessary. Very low grade ore and jig rejects would be required to be totally ground and beneficiated for the production of pellet feed in order to utilize the iron ore resources entirely. Another source of ore for pelletisation would be slimes generated from the washing process as well as the huge quantities already available in the tailings dams in the operating mines. Deslimimg and magnetic route of beneficiation could release at 30-40% of the Fe locked up in these tailings ponds/dams. The paper describes the concept with examples from operating plants and proposes how the adoption could be engineered through test work and proper plan of integration. Keywords: washing, beneficiation, iron ore, lumps, sinter fines, pellets, jigs, screens, evowash, nanowash, thickeners, log washers, drum scrubbers

Sep 1, 2012

By Zoran S. Markovic

The extensive laboratory investigations were carried out in order to determinate behavior of sulphide and nonsulphide copper bearing particles during the flotation. The present ore sample were contained 0.55% Cu with 20.1% of nonsulphide copper in it and gangue material with higher contents of alumina about 19.07%. In this paper will be presented some results such as: effect of particle size, pH and applied collectors. The main goal was in application of collectors S-7518, as well as mixture of KEX and Z-96. Z-96 is a product from Chemical Industry Zupa Krusevac which was used as auxiliary collector in mixture with xanthates. The best results were done with this mixture in ratio KEX / Z-96 as 77/23 % in area of oxidized minerals flotation, but the collector S-7518 was achieved better results in sulphide mineral flotation. The S-7518 has better selectivity between copper minerals and pyrite comparing to mixture of KEX/Z-96 in mentioned optimal ratio. Flotation recovery and copper grade in concentrate were studied by flotation kinetics tests.

Sep 1, 2012

By Chandra Sekhar Gahan

The present study aimed to investigate the depyritization of coal using iron oxidizing and sulphur oxidizing acidophilic chemolithotrophic microorganisms in an iron free 9K growth medium at varying pulp densities. Three different coal samples used in the shake flask study from three different countries such as domestic anthracite (Korean), Indonesian and Chinese lignite. Experiments were carried out in batch at a controlled temperature of 35 °C and varied pulp densities of 8%, 10% and 12% (w/v) with a working volume of 100 ml containing 10 ml of microbial inoculum and 90 ml of the iron free 9K growth medium. Coal samples were crushed and ground to fine size fractions <100 microns by attrition mill wet grinding. The progress in the experiments were followed by the regular measurements of pH, redox potential, viable planktonic cell count, residual Fe2+ ion concentration, amount of acid addition and amount of slaked lime addition. The pyritic sulfur removal percentage varied between 90-95% with highest sulfur removal with China coal (95%) followed by Korean Coal (93-94%) and slightly lower level for Indonesia coal (90%). However the pyrite oxidation was highest for Korean coal ranging between 78-80% followed by a similar level of pyrite oxidation of 50-61% for the Chinese and Indonesian coal. It was found that 10-12% pulp density would be fairly feasible for all the different coals tested leading to an economical process. Another benefit from this study is the iron free 9K growth medium, which will reduce the operation cost and overall it?s an environment friendly process.

Sep 1, 2012

By O. Güven

In recent years, there is an increasing demand on manganese consumption which stems from the important role of manganese in carbon steel production. And the growing need for manganese ores makes the beneficiation of low-grade manganese ores more economical. In this study, the characterization and beneficiation studies were carried out to propose a flow sheet for typical low-grade Turkish manganese ores. For this aim, different gravity separation methods were applied. According to the mineralogical analysis, the major mineral phases are pyrolusite (MnO2) and psilomelane (MnO2) while the major gangue mineral is radiolarite. Gravity separation tests were accomplished by using jigs, shaking table, MGS (Multi Gravity Separator) and in order to obtain products with high Mn ratio, high intensity magnetic separation was also performed. As a result, different combinations of flow sheets were utilized and a concentrate assaying 56.5% Mn with 85 % recovery was obtained.

Sep 1, 2012

By Liu Yong

A complex rare metal ore, containing various valuable elements is used in this study. The mineralogy results indicate that the mineral composition of the raw ore is complex, and there are more than thirty-eight kinds of minerals in the raw ore, and the elements, such as Nb, Ti, Fe, REO, Be etc, always form isomorphism relationship. The REO content of the raw ore is 0.45%, and the contents of other rare metals Nb, Ta, Ti and Zr are 0.33%, 0.02%, 0.93% and 2.00% respectively, and the main gangue elements are Si and Al, and their contents are 71.84% and 8.5% respectively. The beneficiation-metallurgy combination process of ?preconcentration-reduction and magnetic separation-acidification and leaching-precipitation? is used to treat the raw ore. The preconcentration of raw ore is realized through high intensity magnetic separation, and the magnetic field intensity is 1.0T, and the rough concentrate with 2.88% REO and 1.95% Nbresidue can be obtained, and the iron recovery is 92.83%, and the REO recovery is 95.87%, and the Nbresidue is treated by hydrometallurgy process of ?acidification-leaching-precipitation?, then the rare earth oxide, niobium concentrate and zircon-bearing residue can be obtained, and the REO recovery is 80.10% and the Nbresidue and the gangue obtained from the high intensity magnetic separation process is separated by gravity separation, and then the zirconium concentrate can be obtained. The indexes of the beneficiation-metallurgy combination process used to treat the complex rare metal ore are as follows. The REO content of the rare earth oxide is 92.58% and the recovery is 58.44%. The Nb2O5 and 27.42% TFe can be obtained. Iron in rough concentrates is removed after reduction and low intensity magnetic separation, then the iron powder with Fe content over 88% and nonmagnetic rare-metal 2O5 recovery is 94.77%. The rare-metal 2O5 recovery is 80.04%. The mixture of the zircon-bearing 2O5 content of niobium concentrate is 28.34% and the recovery is 54.02%. The ZrO2 content of zirconium concentrate is 28.43% and the recovery is 52.35%. The TFe of iron powder is 89.53% and the recovery is 78.13%. Keywords: rare metal ore, separation and extraction, beneficiation-metallurgy combination, comprehensive utilization

Sep 1, 2012

By K. Kiangi

On installing the Metso Superior MK 54x75? primary gyratory crusher in Nkomati mine the crusher experienced severe power spikes greater than 1000kW which subsequently led to the crusher tripping under load while processing some of Nkomati?s MMZ ores. Likewise significant losses in throughput were also experienced while processing some of Nkomati?s MMZ ore types. Interestingly the crusher was capable of processing the PCMZ ores without experiencing any power spikes or losses in throughput. Investigations into the challenges faced by the crusher while processing Nkomati?s MMZ ores were conducted using the DEM model in conjunction with the fast breakage model present in Metso?s High Fidelity Simulator. The intentions of the study were to establish the most suitable operating conditions or cavity design that would potentially enhance the performance of the crusher. Likewise an understanding of the effects the feed conditions (size distribution and hardness) had on the crusher?s performance was established. Ore characterization tests were conducted on Nkomati?sPyroxenite, Diabase, Calc silicate and quartzite ores which were from Nkomati?s MMZ ore body. The ore characterization tests conducted were drop weight tests, slow compression tests and elastic modulus tests. Four simulations were conducted used the existing cavity design with various open side settings (OSS) and throws. This established the effects of changing the crusher?s operating conditions on its performance. Four additional simulations were conducted on two cavity designs with reduced volumes. This established the effects of changing the crusher?s cavity design on the crusher?s performance. Thus through the simulations a better understandings of the impact of the crusher design, operating conditions and feed conditions on the crushers performance. Furthermore an analysis of the crusher?s performance was made which was used as a basis for comparisons with the base case simulation. Keywords: crusher, discrete element method, simulation, ore characterization

Sep 1, 2012

By Ali Dehghani Ahmadabadi

Gravity separation technique is widely used in mineral beneficiation practices for its low cost, ease of operation, and eco-friendly nature. The most commonly used gravity methods for beneficiation of iron ores are shaking table, jig and spiral methods which aren&apos;t very effective for iron mineral fines. Multi-Gravity Separator (MGS) is suitable for the treatment of fines with a maximum particle size of approximately 500 µm. This study was performed on a low-grade haematite iron ore from Chadormalutailing dams. Detailed mineralogical, physical and chemical characteristics of a goethiticlateritic iron ore showed that the sample contained porous and friable oxides and hydroxides of iron. The ore sample had a feed grade of 35% Fe, 1.1% FeO, 15.5% SiO2 and 8.5% Al2O3. Haematite and goethite are the main iron-bearing minerals while quartzite and kaolinite are the major gangue mineral constituents. In this paper, the statistical evaluation and optimization of grade and recovery using a factorial design of experiment (DOE) method has been carried out for Chadormalulow grade ultra-fine haematite tailings with MGS. The input process parameters considered are drum speed, tilt angle, wash water flow rate and pulp density. The results show considerable improvements in both the quality characteristics such as grade and recovery with statistical evaluation and optimization, compared to the initial value of grade and recovery. Keywords: multi-gravity separator, mgs, statistical evaluation, optimization, haematite

Sep 1, 2012

By S. M. Viduka

This paper presents a numerical investigation of solid separation in jigging device, which is a gravity separation method widely used in ore processing. Separation is recognized as being heavily dependent on fluid motion in the jig. This study explores the effects of the inlet time dependent velocity profile on jigging performance. Modelling of the liquid-solid system is performed through a combination of computational fluid dynamics (CFD) to simulate liquid flow and discrete element method (DEM) to resolve particle motion. The initial packing conditions consist of a binary-density particle system of 1130 particles each 1 cm in diameter. A variety of jigging profiles are implemented in jigging. The saw tooth pulsation profile is selected with three variations in both amplitude and frequency. The performance of each profile variant is compared in terms of solid flow patterns, separation kinetics, energy, and mean particle position. These quantitative comparisons demonstrate significant differences in the segregation rate, energy, and solid phenomena, helping find an alternative optimum operating setting for the system.

Sep 1, 2012

By N. Gurulaxmi Srikakulapu

The demand for high-grade iron ore has increased the importance of beneficiation of low-grade iron ores. The captive mines of Tata Steel Limited, India has reserves of Banded Haematite Jasper (BHJ) ore assayed 40% Fe, 40% SiO2 and <1% Al2O3. QEMSCAN study has revealed haematite and quartz as a major iron bearing and gangue mineral phases respectively. Liberation characteristics have showed 80% liberation can be obtained at particle size below 10µm. In the present study, reverse cationic froth flotation of BHJ using ether diamines is explored in Denver-D12 flotation cell. Polynomial response surface regression equation coupled with six-factor Box-Behnken design of experiments is used to generate the correlation between process separation efficiency and flotation parameters. Flotation studies of BHJ indicated that concentrate of 62% Fe can be achieved with 62% Fe recovery from Jig concentrate at optimum conditions. The obtained product can blend with pellet fines to feed in blast furnace. Keywords: banded haematite jasper, flotation, box-behnken design, response surface methodology

Sep 1, 2012