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By Lokesh K. Thakur, Peter Radziszewski

"For the cases tested (11 mills with 15 operating conditions), the Bond abrasion test steel media wear rate prediction gives an overall error of 73% and a standard deviation of 192.5%. However, total steel media wear in a given mill (ball or SAG) grinding process is a product of three recognised wear mechanisms -- impact, abrasion, and corrosion. A total media wear model can be defined on the assumption that the effect of each wear mechanism can be independently determined which allows for a total media wear model to be defined as the summation of the wear result of each mechanism (eqn. 1). It is assumed that impact and abrasive media wear is a function of the energy dissipated in impact and abrasion as estimated by a DEM charge motion simulation. Corrosive media wear is assumed to be a function of the media surface area present in a mill.The 3 initial tests developed (steel abrasion wheel, corrosion batch mill, impact chamber) coupled with the impact and abrasion energy spectra from a DEM charge motion simulation produced total steel wear rate results for the same cases as the Bond abrasion test giving an overall error of 0% and a standard deviation of 66.1%. However, if one were to consider the general observation that wear is proportional to energy and maintain the assumption that corrosion is proportional to media surface area then one would realize that the total media wear eqn. (1) can be reduced to eqn. (2). As this is a linear equation and one has, for the same mill, media wear and operating data for three different operating cases, one obtains three equations with three unknowns. This defines a simple matrix manipulation to determine the constants k1, k2 and k3. From the previous data set, we had 6 identical mills grinding the same ore but having different worn liner profiles and charge volume which provided the opportunity to average out the ki values over 20 combinations of 3 cases. With the determined ki values, it was possible to determine a second estimate of the contributions of impact, abrasion and corrosion to total media wear giving an overall error of 0% and a standard deviation of 56%."

Jan 1, 2003

By O. N. Mohanty, S. Mohan Rao, N. D. Rao, T. Mukherjee, P. V. T. Rao

"Chromite ore is an indispensable raw material in the manufacture of ferro-chrome and charge-chrome, which are used for the production of stainless and other alloy steels. The demand for chromite ore is ever increasing because of increasing consumption of these steels. Keeping this in view, Tata Steel is keen to recover values from fines and wastes, and also to produce value added products from their captive chromite mines and its processing plants.Tata Steel has its captive chromite resources at Sukinda, Orissa. They contain two ore types, i.e. (i) Ferruginous and (ii) Siliceous. The generation of off-grade ores is an increasing trend and simultaneously customer quality requirements are becoming ever more stringent. The ferruginous type ore also contains a considerable quantity of in-situ fines (~20% particles below 0.5 mm) that compound the beneficiation problem.In many places, in India and abroad, mined non-marketable off-grade and low grade chromite ores are upgraded by using either simple classification techniques like screw classification, hydrosizing, hydrocycloning or conventional gravity concentration processes such as Heavy media separation, Jigging, Spiraling, Tabling etc.At Tata Steel, the ferruginous type ores are treated in Chrome Ore Beneficiation (COB) Plant that comprises: a crushing and grinding circuit; a classification circuit using hydrocyclones; and a beneficiation circuit using 4 stage spirals in the coarse circuit (-0.5+0.1 mm) and 3 stage spirals & tables in the fine circuit (-0.1+0.038 mm). In this process, 3 types of tailings are being generated and together analyses about 17 % Cr2O3, which is high. From the present operation the chromite recovery is around 70% and could not produce coarse concentrates (+0.5 mm size). Whereas the siliceous type ore is treated in the Lumpy Ore Processing (LOP) plant, consisting of crushing-washing & classification-hand sorting operations, to produce marketable grade lumpy ore and –10 mm de-slimed fines. These fines are intermittently treated in the COB plant. The higher silica content (greater than 1%) and low Cr/Fe ratio (less than 2.8) are the problems with these concentrates."

Jan 1, 2003

By M. Pelser, Lorenzen L.

"The presence of calcium and magnesium in the hydrometallurgical processing of base metals, results in a number of process difficulties. These problems range from the contamination of the final product (where the final product is a precipitate) to high energy consumptions and large bleed streams during electrowinning. Calcium poses an additional problem in sulphate solutions owing to the low solubility of its sulphate salts. This can easily lead to a process stream that is supersaturated with calcium sulphate, resulting in unwanted solids formation within the process equipment.A review of literature has proven that there is no conventional method for the control of calcium and or magnesium, although a number of potential processes have been identified. The technologies investigated included precipitation, ion exchange and solvent extraction, for which at least one method was found under each. To make the reader aware of these processes a short description was provided of each within the text.Of these processes, fluoride precipitation was selected for experimental investigation based on the low solubility of calcium and magnesium compared to the base metals. This process involves the addition of a soluble fluoride to precipitate CaF2 and MgF2. The experiments were designed to investigate the equilibrium of the system at varying parameters of which the level of fluoride addition, the ratio of calcium to magnesium, and the identity of the soluble fluoride was reported. In all of the instances the process showed high selectivity towards calcium and magnesium over the base metals. The experiments proofed the process to have a higher affinity towards the removal of magnesium at compositions where the molar ratio of calcium to magnesium was higher than 1:3. It is often the case that the calcium to magnesium ratio is in the region of 1: 10. From this it follows that the fluoride addition has to be stoichiometric or greater for calcium and magnesium combined, if the calcium is to be precipitated. This was demonstrated as well. On the identity of the soluble fluoride hydrogen fluoride was compared to ammonium fluoride, of which the latter was found to be preferred."

Jan 1, 2003

By Sanggono Adisasmito

"The quality of the higher education in Indonesia is being improved by implementing a program financed by the World Bank under a project named QUE (Quality for Undergraduate Education). The investments are provided to selected study programs through a competitive selection process. The grant finances staff development, the purchase of equipments, textbooks, consumables, technical assistance, and incentives for outstanding faculties such as teaching grants, project grants, lecture note awards, and educational policy studies. These additional investments are provided to produce chemical engineering graduates that will compete beyond the national market.Chemical Engineering Department of Institut Teknologi Bandung in Indonesia has been selected to receive the QUE grant beginning the year 2000 and ending the year 2004. The department is actively involved in the mineral processing issues, particularly in the aspects of energy supply and the environmental protection. The activities are distributed in different laboratories and areas of expertise, such as: thermodynamics and utility systems, process equipment, chemical reaction and catalysis, microbiology and bioprocess engineering, process control, ceramics, as well as polymer and membrane technology. The main objectives of the QUE project are to improve the undergraduate program in the following aspects: Relevance, Academic atmosphere, Institutional management and commitment, Sustainability, as well as Efficiency and productivity, or abbreviated as RAISE. At the end of every fiscal year, the progress of the program is evaluated to measure the effectiveness of the project.The achievement of the QUE project objectives were assessed using performance indicators developed during the program design. There are six indicators to measure the performance of the individual program of study, such as: (1) Admission Test score, (2) average students' Grade Point Average (GPA), (3) average graduates' length of study, (4) graduates' waiting time before getting first job, (5) Test of English as Foreign Language (TOEFL) score, (6) Graduate Record Examination (GRE) score. Essentially, the RAISE evaluation criteria will be used to perform three main functions, such as (1) to measure the achievement through the six quantitative performance indicators, (2) to support the progress of evaluation and reporting throughout the implementation of the program, (3) to provide a universal framework for qualitative evaluation."

Jan 1, 2003

By Xiong Dahe

"SLon vertical ring and pulsating high gradient magnetic separator utilizes the combined force field of magnetism, pulsating fluid and gravity to beneficiate weakly magnetic minerals with the advantages of large beneficial ratio, high recovery, matrix not easy to be blocked and excellent performance.We have developed SLon-750; SLon-1000; SLon-1250; SLon-1500; SLon-1750 and SLon-2000 VP HGMS. Now more than 200 of them have been successfully applied in China.Application in Qi Dashan Mineral processing Plant of Anshan Iron and Steel Company: The iron ore consists of magnetite and hematite. In 2001, six SLon-1750 magnetic separators are applied to control the tails grade of fine hematite. The results of flowsheet is: feed grade 30.15%Fe, concentrate grade 67.00%Fe, iron recovery 75.86%. The results set up the historic high record of this plant and the processing coast is greatly reduced.Application in Gushan Iron Mine of Ma Anshan Iron and steel Company: There are 6 SLon-1750 and 4 SLon-1500 magnetic separators applied in this mine to treat refractory hematite ore. The feeding grade is about 45%Fe. The final iron concentrate grade is about 60%Fe and the iron recovery is about 76%. The results are much better than the previous gravity flowsheet.Application in Meishan Iron Mine of Shanghai Baoshan Iron and Steel Company: The mined ore consists of magnetite, hematite and siderite. Because of a relatively high content of phosphorus, the iron concentrate could not meet the market requirements. Now 18 SLon-1500 magnetic separators are applied to reduce phosphorus, which is reduced from about 0.4%P to 0.246%P. The quality of iron concentrate is greatly upgraded.Application in Panzhihua Ilmenite Processing Plant: In the past, the -0.045mm ilmenite fraction was discarded in to the tails because of lack of high efficient equipment. In 2001, the plant built up a magneticflotation flowsheet to recover the fine ilmenite from the -0.045mm fraction with 6 SLon-1500 magnetic separators. The total results are: feed grade 11%TiO2, concentrate grade=47% TiO2, recovery 44%. Each year the flowsheet recovers 60,000t fine ilmenite concentrate."

Jan 1, 2003

By F. L. Mentg

The utilization of acid leaching tailings was studied. It is obvious that the Fe in acid leaching tailings can be leached into solutions as Fe2+. In this paper, the influence of conditions, including the concentration of ferrous sulfate, pH, temperature and velocity of air flow was investigated. The optimum conditions for preparing seed crystal are as follows: the concentration of ferrous sulfate is 20 g/L; pH is 9.5~10; reaction temperature is 10~20?; velocity of air flow is 0.4m3/h. The optimum conditions for preparing iron oxide red are as follows: the concentration of ferrous sulfate is 5 g/L; reaction temperature is 80~85?; velocity of air flow is 0.13m3/h. At last, the product of iron oxide red could be prepared by ammonia method.

Jan 1, 2014

By Jan Svoboda, Atsushi Shibayama, Toyohisa Fujita, Toshio Miyazaki, Kenji Murata

"The electrical disintegration (ED) method and disintegration by underwater explosion were investigated as new fragmentation techniques for the kimberlite ore and tungsten scrap of superalloy (carbide bit). The results of various breakage tests demonstrated that both fragmentation methods as new disintegration techniques for recycling were able to liberate various components of materials of different resistivity and elastic impedance.SUMMARYThe breakage of the kimberlite ore from South Africa (sample size: 15 mm x 15 mm x 6 mm) was achieved by the ED method. A relationship between the sample size, voltage, the electrical current and the energy needed for the disintegration was found from the experimental results. Kimberlite exhibited a high degree of breakage, when the high voltage of 60 kV and the pulse current of approximately 5000 A were applied to the sample by the generator during 0.2 microseconds (Fig. 1)."

Jan 1, 2003

By Aubrey Mainza, Malcolm S. Powell

"A hydrocyclone with two vortex finders, named the three-product cyclone (3PC), has been successfully tested in the Platinum industry for dealing with the dense Chromite found in UG2 ores. This dense component preferentially reports to the cyclone underflow, resulting in an over-ground fine Chromite component in the final product. The dense media effect caused by a high concentration of this in the cyclone feed produces a coarsening of the cyclone overflow, which results in loss of recovery through over-size silica in the PGM carrying component material in the float feed. The fine barren particles of Chromite that report to the overflow are recovered through entrainment in the flotation process, resulting in detrimental contamination of the slag produced from the concentrate.Data from many industrial scale tests of the 3PC have shown that three distinct products are obtained when the inner vortex finder length (LIVF) is extended to the region either above (normal classification) or below (reverse classification) the transition zone (a region were the inner and outer overflow streams are identical). Due to wear problems arising from extending the IVF deep into the cone of the cyclone, it is advantageous to use the shorter IVF. Only the normal classification results are reported here, but similar outcomes (to opposite overflow streams) were obtained for the reverse classification. The results showed notable differences in the percentage split of the plus 100µm material in the product streams, confirming that three distinct products are discharged from the 3PC. About 12% of the plus 100µm material in the feed reports to the middlings stream, 1% reports to the final product, and the remainder to the cyclone underflow.Results of silica and chrome splits to the three distinct products namely, the inner overflow (INO), the outer overflow (OUO) and the underflow (U/F) are given in Table 1. These show that the 3PC can be used to recover coarse silica through screening the middlings product - which has a high silica content. When the vortex finder ratios (ratio’s of cross-sectional areas) are carefully selected, the split of plus 100µm silica to the middlings product ranged from 2.9 to 9.6%. Large amounts of oversize silica and chrome report to cyclone underflow, explaining their high percentages in the underflow stream."

Jan 1, 2003

By C. Y. Sun

Flotation of chalcopyrite and unactivated malachite with xanthates (ethylxanthate, butylxanthate, octylxanthate and dodecylxanthate) is studied in this paper. Minerals interacted with xanthates are detected by FTIR, and simulated by molecular mechanics. It shows that chalcopyrite can be floated with 4 kinds of xanthates, and unactivated malachite can?t be floated with ethylxanthate but can be floated directly with later 3 kinds of xanthates while characteristic absorption peaks of those four kinds of xanthates are all detected by FTIR on chalcopyrite and malachite surface. After simulating the interaction between xanthate and mineral, it shows that H2O and OH-can interact with chalcopyrite and malachite, and their interaction energy may be so called energy bulwark which must be overcome by collector when collector interacts on minerals; the two sulfur atoms in xanthate group interact with copper and neighbor iron atoms on chalcopyrite. It also shows that molecular mechanics results with logP of collectors can interpret the mechanism of xanthate-mineral on atom scale.

Jan 1, 2014

By S. M. Bradshaw, C. Dorfling, F. Ngandu

"Selenium removal and platinum group metal (PGM) recovery from copper sulfate leach solutions form an integral part of platinum producers’ base metal refinery operations. Recent studies found that substantially higher PGM recoveries can be achieved if excess thiourea instead of sulfurous acid is used as precipitation reagent; however, the impact of the proposed process on downstream processes was unknown. The objective of the current study was therefore to investigate the effects that excess thiourea and residual selenium present in the rich copper sulfate electrolyte have on copper electrowinning. This was achieved by performing cyclic voltammetry tests using a platinum rotating disk as working electrode, a graphite auxiliary electrode and a saturated calomel reference electrode. A synthetic copper sulfate electrolyte containing 0.01 M Cu2+, 1 M H2SO4 and varying amounts of selenium (20 – 150 mg/L) and thiourea (10 mg/L and 100 – 300 % excess) was used. The results obtained have shown that both thiourea and selenium interact with the cupric ion cathodic reduction reaction. Thiourea polarized the working electrode and lowered the efficiency of the cupric reduction reaction. Tests on the solutions with high selenium concentration showed simultaneous reduction of copper and selenium, which led to copper selenide formation. Nodule formation on the deposit surface also became significant at higher selenium concentrations. Based on these results, it was concluded that precipitation of PGMs from the copper sulfate solution with excess thiourea is not feasible due to the detrimental effect on downstream electrowinning operations.INTRODUCTION During the high pressure oxidative leaching stage in a typical base metal refinery (BMR) circuit, selenium, tellurium and some platinum group metals (PGMs) are dissolved along with the desired copper ions. The impurities (selenium and tellurium) may pass to the copper electrowinning circuit where it can result in the formation of nodular copper electrodeposits or reduced current efficiency. The presence of PGMs in solution, on the other hand, increases the precious metal inventory and potential losses of the operation. Currently, sulfurous acid is widely used for selenium and tellurium precipitation from copper sulfate leach solutions. Sulfurous acid is capable of reducing cupric ions to cuprous ions; the generated cuprous ions then react with Se4+ and Se6+ to precipitate selenium as a copper selenide (Bello, Dorfling, 2014). Recent studies have, however, proposed the use of excess thiourea as a precipitating agent for the removal of selenium and tellurium; it has the advantage of improved PGM recovery in the Se/Te precipitation step (Lottering, Eksteen et al., 2012; Mulwanda, Dorfling, 2015)."

Jan 1, 2018

By Ashok M. Raichur, S. P. Vijayalakshmi

"Recent advances in technology and the growing environmental concern have laid emphasis on the usage of fine clean coal. Coal fines are also generated in large amounts during various coal processing operations and are difficult to be treated, handled and disposed. Since most of the operations use water as the carrying medium, the fines so generated contain lot of moisture. Conventional technique for processing coal fines includes flocculation by a polymeric reagent followed by moisture removal using a rotary drum or a pressure plate filter, which produce a product with more than 30% moisture. Polymeric flocculants though required in small amounts, need high shear mixing for good performance and operate only in a narrow pH range. Moreover they increase the viscosity of the solution by many folds. Hence it becomes imperative to emulate newer methods for efficient fine coal processing. One such method is the novel use of microorganisms in coal processing.The present investigation deals with the utilization of two gram-positive microorganisms, Mycobacterium phlei and Bacillus subtilis, as bio flocculants and dewatering aids in fine coal processing. Preliminary characterization done on J-coal and M.phlei showed that they are negatively charged over most of the pH range. B.subtilis was found to possess positive charge below pH 4.7. The adhesion studies proved the high potential of microorganisms for adsorption to surfaces. Adhesion tests were conducted at various experimental conditions by varying parameters like pH and ionic strength of the suspension. Results obtained showed that adhesion is always higher in the presence of an electrolyte like KNO3 and most of the adhesion takes place in 15 minutes. With change in pH the amount of B.subtilis adhering on to J-coal remained almost constant and for M.phlei it decreased at higher pH values. Increase in ionic strength did not increase the adhesion of bacteria. Flocculation experiments confirmed the ability of the bacteria to act as bio flocculants. It was seen that about 98% of the coal settled in about 2 minutes on the addition of bacteria along with the addition of the electrolyte. The electrolyte was found to be indispensable for efficient flocculation of the coal suspension and for the attainment of a clear supernatant after flocculation. Also the optical micrographs revealed the formation of large, tight flocs when the electrolyte is present along with the bacteria. Further, flocculation tests were done in the pH range of 2-10 and the flocculation efficiency was found to be independent of pH."

Jan 1, 2003

By Sonia Helle, Ursula E. D. Kelm

"From a metallurgical point of view, acid leaching of oxide zone copper ore is considered in the first place in terms of ore grade, whole rock mineralogy, rock granulometry, crushed aggregate size distribution, porosity, permeability and corresponding fluid flow characteristics. Despite exhaustive physicochemical and general mineralogical characterization, drops in copper recovery occur and are often attributed to and “unquantified mineralogical misbehaviour” of the gangue phases. This study establishes an experimental link to monitor and quantify the chemical interaction of chrysocolla, malachite and atacamite with reactive gangue phases.Laboratory-scale sulphuric acid (15%) leaching in small columns is carried out using a synthetic rock composed of 57% quartz, 1% ore phase, and 42% reactive gangue. Gangue phases were selected to represent mineralogy found in argillic, advanced argillic, and propylitic alteration zones. Exotic copper ores of Codelco Norte (in particular Mina Sur) served as model for the modal distribution of mineral phases. Natural reactive gangue phases (<200 Tyler mesh) were chosen as pure as possible: Saz-1 and Swy-1 montmorillonites, KGa-1B and KGa-2 kaolinites (all Clay Mineral Society, USA, Source Clays) Nau-2 nontronite, Imt-1 illite (both Clay Mineral Society Special Clays) and Chilean mordenite, laumontite and bentonite. Ore phases are: mineraloid chrysocolla from Radomiro Tomic (Codelco Norte), reagent grade malachite and a purpose synthesized atacamite-paratacamite mixture. Complete chemical, physicochemical and mineralogical characterizations were carried out for ore and gangue phases.The following observations hold for samples with and without mineralization: Smectite-rich gangue increased up to 75% in volume. Once wet, air-filled vesicles formed due to the rapid sealing effect of overlying smectite in the column. No volume change occurred for illite, mordenite and kaolinite gangues. For kaolinite mixtures acid puddles formed on top of the column during initial leaching due to the delamination and barrier formation of this phyllosilicate. Fluid recovery was <60% for expandable phases and reached up to 80% for non-expandable mixtures. These observations confirm the very low extractions obtained in ore with a combined smectite – kaolinite gangue for Mina Sur. The most important mineralogical changes observed in the solid residues are: reduction of basal smectite phase reflections (XRD), and slight loss of illite intensities. This is also reflected in the major element composition of the residues, which demonstrate a loss of Mg, Mn, Ca, Na, K followed by Fe, Al and Si; with their proportions depending on the starting materials. Furthermore, alunogen and meta-alunogen formed, with related phases coquimbite (illite) and godichite (nontronite) also depending on gangue mineral chemistry. For laumontite samples, meta-alunogen and alunogen precipitated from the leachate."

Jan 1, 2003

By Reza M. Rahman, Seher Ata, Graeme J. Jameson

"This paper presents the results of a through investigation into the froth recovery measurements in a controlled plant environment using a device that allows direct collection of dropback particles from the froth phase. Test work was performed at the Northparkes concentrator (NSW, Australia), using a feed taken from the head of the cleaner scavenger bank. The feed slurry had a relatively higher copper grade varying from 5.2% to 6.8%. Experiments were performed to investigate the effect of important flotation parameters such as air flowrate on the froth recovery. The size of the particles in the relevant streams was also analysed to acquire in-depth knowledge about the froth dropback mechanism. The results suggested that the froth recovery could be as low as 70%, although it was relatively easy to achieve the values in the range 75% to 85% by the correct choice of operating variables. It was found that the air flowrate has a positive impact on both collection (pulp) and froth zone recoveries. However, the effect was more prominent in the froth zone. It appeared that the froth recovery is a strong function of particle size."

Jan 1, 2014

By Hongchun Lou, Yan Zhang, Xianjun Lu

"The potential of Fe(NO3)3 modified attapulgite was assessed for the adsorption of phosphorous removal from aqueous solutions. Natural attapulgite was modified by Fe(NO3)3, and thus the composite adsorption materials could be obtained. Also phosphorous adsorption characterization on the iron-coated attapulgite was investigated in this research. Taken overall the results suggested that phosphorous adsorption capacity could be improved markedly by adopting ferric modified-attapulgite. The optimum phosphorous adsorption were developed in the experimental conditions of the solid-to-liquid Ratio 1g/L, the initial phosphorous concentration 5 mol•L-1, reaction time 120 min, temperature 25 ? and pH=4.0, the removal efficiency is 92.28% for the modified attapulgite. In comparison of batch experimental results of phosphorous adsorption onto natural and iron-coated attapulgite, it has provided much more likely the same change trend. On the other hand, the outcomes of this analysis indicated that ferric modified adsorbent was notably influenced by adsorption element over natural attapulgite. The Freundlich isotherm adequately described the adsorption course of phosphorous onto ferric modified-attapulgite with the correlation coefficient R2 goodness of fit of 0.9690."

Jan 1, 2014

By Yi-jun Cao, Jin-cai Ran, Guo-sheng Li, Jiong-tian Liu, Li-jun Deng, Shu-lei Li

A fly ash sample from a power station in Guangdong province has been characterized by size separation, X-ray diffraction, contact angle measurements and X-ray Fluorescence. The ash sample had a loss-on-ignition (LOI) (%) of 15.54% and a large proportion of the unburned carbon was distributed in the +74 µm and -20 µm fractions. Contact angle measurements suggested that the removal of unburned carbon from the fly ash using flotation would present some challenges. The effects of various operating variables on the removal rate of unburned carbon (RUC) (%) and (LOI) (%) were determined using a cyclonic-static micro bubble flotation column (FCSMC). Within the range studied, the optimum diesel oil dosage was 1200 g/t, abies oil (frother) dosage was 600 g/t, pulp density was 20%, superficial gas velocity was 1.4 cm/s and circulating pressure was 0.20Mpa. Column flotation tests indicated that the FCSMC method a viable and effective separation process for removing the unburned carbon from the fly ash. Under the optimized conditions, a clean ash with 2.13% LOI and 94.21% RUC was obtained.

Jan 1, 2014

By S. Kelebek, A. Khan, J. Caceres, D. Beckett

"Pyrrhotite in nickel-copper sulphide ores is nickeliferrous and intimately associated with pentlandite. Due to its low nickel content, pyrrhotite rejection is an important step in processing of these ores. In our laboratory, various reagents were investigated for their effect on pyrrhotite depression. Among these, a combined use of triethylenetetramine and sodium metabisulphite was found highly promising.The work described in this paper has two parts. The firs part is a summary of results obtained on process samples from the pyrrhotite rejection circuit at Falconbridge’s Strathcona Mill. The second part involves simulation of the circuit performance based on the reagent conditions used in the experimental work and the concept of split factors.Two sets of reagent conditions were evaluated. The first one involved baseline conditions, simulating the current reagent performance. The second one simulated the impact these new reagents can have on the circuit performance.The simulation results obtained under baseline conditions indicated a good agreement with the current circuit performance (Figure 1). The simulation results suggest that at practically the same pentlandite recovery and tailing grades, the circuit concentrate nickel grade can be doubled through effective pyrrhotite rejection by these new reagents (Figure 2)."

Jan 1, 2003

By Claudio L. Schneider, Reiner Neumann

Any serious study of stereological conversion procedures must be based on an as accurate as possible complete fractionation of a real mineralogical texture. The original work on the Dolomite- Sphalerite Magstream? separation provided excellent data for establishing a working stereological conversion procedure, which has been successfully applied to a number of ores since its implementation. The linear grade distributions measured from these fractionated particles have been published and are accessible. The procedure for stereological conversion from areal measurements is exactly equal to the procedure for linear measurements. Particle composition from the dolomite-sphalerite density-fractionated particle sets, derived from both linear and areal data (Figures 1 and 2, respectively) are redundant, after proper transformation, and match the particle’s compositional range (plotted against S.G.) expected from Magstream?; direct density measurements by Hemicropicnometry plots within the ranges. Linear data cannot be used without conversion, but areal measurements are often directly applied as liberation spectra. Our areal measurements, without stereological conversion (Figure 3), differ completely from the results after transformation, and its density range falls mostly out of the expected/measured values. Therefore non-transformed areal data cannot be directly applied as useful liberation information.

Jan 1, 2003

At times the phosphate industry, in Florida, encounters phosphate rock that gives lower than expected P2O5 recovery in the rougher plant section. The drop in recovery is typically 10% and as much as 30% or more. Variations in feed quality from day to day, shift to shift and even from drag-line to drag line, represent a challenge to the beneficiation plant operators and reagents? suppliers. Therefore, this characterization study has been initiated to identify the reasons for the differences in flotation behavior of such feeds. The study involves many samples to cover such variations. The characterization work includes: ? Mineralogical and chemical analysis; ? Size, shape, surface roughness and porosity analysis; ? Surface charge and surface contamination with other phases (minerals); ? Clay content and its relationship to phosphate and silica particles. The results correlated with flotation data and adsorption density measurements clearly establish the statistically significant variability in characteristic features that influence flotation response. This article discusses results from the above listed studies. On the basis of the obtained data, recommendations of practical approaches to overcome the problem of feed variability in phosphate flotation plants are delineated.

Jan 1, 2014

By S. K. Pan, M. P. Srivastava, N. Prasad

"Dalli mines of Bhilai Steel Plant, India is fully mechanized iron ore mine having wet processing system. It has a capacity to treat 5 Mt of ROM. In processing circuit of Dalli mines, scrubbing, wet screening and classification operation is being carried out. Average slime generation for the last five years is about 14% of ROM. As the mining has reached to the lower benches, fines generation is more. As a result, very fine and heavy particles, which settle fast, are being discarded with the slime to tailing pond. These heavy and faster settling particles were causing jamming in the thickeners.Laboratory investigations were carried out at Research and Development Centre for Iron and Steel (RDCIS) to suggest a suitable scheme to recover high quality fines so that the availability of thickener can improve. The slime samples were first treated in a floatex density separator. The concentrate obtained from the floatex density separator was treated in hydrocyclone. Laboratory investigations indicated that the slime with 49% Fe, 12.7% silica and 10.7% alumina can be upgraded to 62.1% Fe, 3.3% silica and 2% alumina with 36% material recovery. Based on the laboratory studies ,a system was installed at Dalli minesThe general arrangement of the system is shown in Fig. below."

Jan 1, 2003

By Gus Van Weert, Samuel A. Bolorunduro, David B. Dreisinger

"INTRODUCTIONThe objective of this work was to deport silver into a residue suitable for subsequent extraction without compromising the high base metal extraction during the pressure oxidation.RESULTS AND DISCUSSIONThe complex sulphide from the tailing pond of Cannington mine, Australia, was re-grounded and a bulk concentrate was recovered by flotation. The major economic sulphides are galena and sphalerite. The chemical analyses revealed 17.22% Fe; 4.88% Zn; 8.22% Pb; 9.49% S2- and 422 g/t Ag. The baseline cyanidation yielded 36.60% of silver at high cyanide consumption (24.17 kg/t NaCN). Pressure oxidation at 150°C (in the absence of iodide), followed by cyanidation of the residue yielded 8% silver extraction. Pressure oxidation was carried out at 110-150°C in sulphate media with additions of potassium iodide and the resulting residue was subjected to cyanidation. High recovery of silver was achieved because its incorporation into lead-hydronium jarosite during the pressure oxidation was minimised, while its deportment into the cyanide-soluble silver iodide was favoured (Figure 1). Silver recovery decreased slightly at high temperatures (140° and 150°C) because of the enhanced stability and kinetics of leadhydronium jarosite, but this could be overcome by increasing acidity and iodide concentration of the slurry."

Jan 1, 2003