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By Gautam Chandra Mondal

An attempt has been made to carry out qualitative assessment of mine water discharges from the different mines of West Bokaro Coalfields of Hazaribag district of Jharkhand, India. A total of 33 mine water samples were analyzed for pH, electrical conductivity (EC), major cations (Ca, Mg, Na, K), major anions (HCO3, SO4, Cl, NO3), and heavy metals (Fe, Mn, Cu, Zn, Pb, Cr, Ni, Co, As). The hydrochemical data has been evaluated in terms of major ion chemistry, solute acquisition processes and suitability of mine water for domestic, industrial and irrigation uses. The pH of the analyzed mine waters varies from 5.27?8.43 indicating acidic to alkaline nature of the water. The electrical conductivity (EC) values varied from 276 µScm-1 to 1598 µScm-1 for measured samples and spatial differences between the EC values reflects the wide variation in lithology, surface activities and hydrological regime prevailing in the region. The anion chemistry of the analyzed water samples shows the dominance of SO4 and HCO3 with a minor contribution from Cl, NO3 and F. The observed high values of sulphate in the mine water of the area may be attributed to the oxidative weathering of pyrites. On average chloride is contributing 5% of the total anionic balance (TZ-). Fluoride and nitrate have low concentrations and on average contributing <2% the total anions. The cation chemistry indicates that 79% of the samples are Ca>Mg>Na>K, while the 6% belong to Ca>Na>Mg>K and 1% of Ca>Mg>K>Na. Weathering of rock forming minerals and cation exchange processes normally control the levels of these cations. Concentrations of some heavy metals (Fe, Mn, Ni, Cr) are found to be well above the prescribed permissible levels recommended for the drinking water. The water quality assessment for drinking purposes indicates that most of the mine water having high TDS, total hardness (TH) and sulphate concentrations. This suggests that mine water of the study area is not suitable for direct use in drinking and domestic purposes and needs a proper treatment before its utilization. The assessment of water for irrigation uses show that the water is good to permissible quality and can be used for irrigation uses. However, high values of salinity, %Na, SAR, RSC and Mg-hazard at certain sites restrict its suitability for agriculture uses. Keywords: mine water; ion chemistry; quality assessment; West Bokaro coalfields

Sep 1, 2012

By A. Vidyadhar

Printed circuit boards (PCBs) constitute a majorpart of electrical and electronic equipment containing valuable metals such as Cu, Ni, Au, Ag, Pd, Fe, Sn, Pb, etc. The concentration of base and precious metals in PCBs is observed to be several times more than those in their respective ores. Therefore, the recycling of PCBs is necessary to recover the valuable materials. However, the ultrafine particles pose a big challenge. Removal of them is suggested prior to processing by flotation. Froth flotation is observed to be a promising technique for rejecting the plastics from the comminution product. In the present work, enrichment of ground 1.0 mm PCB powder was investigated through flotation route by varying the operating variables such as frother dosage, pulp density, air flow rate and rotational speed of the impeller. The liberation studies indicate that excellent liberation of metal values is achieved from the non-metallic constituents at -1.0 mm size and below. The particulate system is quite rich in metal value with about 23% total metal content. The non-metallic constituents such as plastics are observed to possess strong hydrophobicity while the metal particles in the pulverized mass are hydrophilic in nature. Froth flotation kinetics is studied in depth with a view to facilitate high rejection of plastics and identify optimum operating conditions for the same. A number of experiments are performed to establish the influence of the operating variables on flotation performance. The conditions for achieving higher yield of the metal-rich fraction with respect to a specified grade are discussed in the light of the experimental results. It is found that the requirement of reagents is negligible which could be a very important factor from the commercial stand point. Single-stage flotation increases the metal content from 23% to over 32% with a mass yield of around 75% and over 90% recovery of metal values. 32% of the materials in the feed could be effectively rejected in the float fraction losing less than 4% metal values. The dependence of kinetics on the process variables is also discussed. It was concluded that a high rotor speed helps in efficiently rejecting the plastics. Frother should be added to help stabilize the froth and enhance the kinetics. A moderate air flow is required while pulp density must be kept low for efficient pre-concentration. It is established that the entire -1.0 mm comminution product could be treated by flotation for generating a pre-concentrate. Keywords: printed circuit boards, recycling, froth flotation, kinetics, recovery

Sep 1, 2012

By A. V. Bogdanovich, S. A. Urnysheva

"Gravity and X-ray luminescent separation methods are generally used in processing of diamond ores. X-ray luminescent separators are applied for separation of diamonds from feed ore size fractions from 100 to 10-15 mm size and for final treatment of gravity concentrates over 1 mm size. Gravity separation machines used for diamond ores separation are heavy medium cyclones and pneumatic jigs. One of the most important parameters, to a large extent affecting diamonds recovery from ore, as well as processing costs and specific energy costs, is size of dumped final tailings. That was exactly the purpose of the studies, the results of which are described in this paper. The studies performed on different ores showed that in order to achieve high recovery results, it is necessary to dump heavy medium separation tailings below 3 mm size. Separation of final tailings of -6+1 mm size by jigging is also possible. However, with a view to exclude extra diamond losses, it is necessary to maintain jigging concentrate yield approximately at 25% from starting feed, with its subsequent cleaning in heavy medium cyclones. In addition to that, it is necessary to separate 20-25% of middling with diamonds content at feed ore level and subject it to grinding. This will complicate flow sheet, but reduce load on heavy medium cyclones. In order to develop optimal flow sheet for gravity concentration of a specific diamond ore, large-scale investigations are required, including technical-and-economic assessment of separation alternatives. INTRODUCTION In processing of diamond ores, gravity and X-ray luminescent separation methods are generally used. It is common practice to apply X-ray luminescent separators for separation of diamonds from feed ore size fractions from 50 (100) to 20 (10) mm size and for final treatment of gravity concentrates over 1 mm size. With that, X-ray luminescent separation tailings larger than 3-6 mm size are reground and delivered to gravity concentration processing stage. Middling products circulation volumes are large, not infrequently necessitating decrease in concentrating plants capacity, especially with mining in deep workings of deposits, where ore strength is higher (Goryachev, 2010; Vaginov, 2000; William, 1988). Diamond ores preparation before processing is accomplished by means of roll-screw crushers and autogenous grinding mills, minimizing probability of free diamonds damage in liberation from barren rock. In re-crushing of size fractions that are “difficult” in autogenous grinding, high pressure grinding rollers are applied (Burchardt, 2014; Fedotov, 2011a, 2006b)."

Jan 1, 2018

By Lev O. Filippov, Inna V. Filippova

"Flotation of metal-organic precipitate in column is sensible to the hydrodynamic conditions determined by the diameter and dispersion of rising bubbles. Thus, the dissipation energy in the system resulting of ratio between superficial fluid velocities (gas and feed) in the column is main parameter for precipitate flotation in pilot or industrial scales. The knowledge of aggregate structure can lead to better understanding and control of many solid-liquid separation processes (sedimentation, filtration, thickening and flotation). Many authors highlight the importance of structural properties (i.e. floc density) for different industrial applications.This approach was applied to achieve the flotation of molybdenum precipitate obtained with organic collector a- benzoin oxime for molar ratio 1:2. Flotation tests were carried out at lab and pilot scale with rigorous control of the size distribution of bubbles and the values of dissipation energy in the systems.Structural evolution of Mo precipitate and the destruction phenomenon were described by using of the various fractal dimensions, which were deduced from experimental data of laser sizer devices and optic microscopy pictures of precipitate. The boundary fractal dimensions Df of large aggregates allows the detection of a structural scaled organisation of the precipitate flocs (elementary germs-microflocs-flocs). The fractal dimension of the particle mass distribution Dm=1.94+/-0.15 suggests, for the floc structure, a cluster-cluster aggregation process either with structuration or breakage phases.The destruction process characterised by a fractal dimension Dg controls the final size distribution. The floc destruction occurs for the lowest values of the dissipation energy (0.02 – 0.05 W/kg). The relation between Dg and the system dissipation energy Et (for various energy E dissipated in the agitation cell) involves the different breakage mechanisms of aggregates in function of the aggregation bonds (Fig. 1).Besides, the destruction of floc produces very fine particles (elementary germs or/and microfloc according to E), and thus induces the difficulties of bubble-particle attachment during the precipitate flotation in column. Yet, very small bubbles, which increase the collision probability, would make the flotation feed rate decrease. The optima ratio between superficial gas and feed velocities are determined for bubble size and flotation results control at pilot scale. Thus, it is possible to providing the catastrophically changes of precipitate column flotation by using the following established experimental relation: the mean diameter d of the flocs under the action of dissipated energy Et follows a power like law (d~Et -0.5). This allows estimating the size distribution of flocs for the E values which can appear in column."

Jan 1, 2003

By N. I. Um

The coal bottom ash generated from coal-fired power plant accounted for approximately 5 mil-lion tons in Korea. Almost all of coal bottom ash was treated as reclamation of the landfill because of the content of unburned carbon. For recycling of coal bottom ash, effective removal of that is required. So, in this study, the removal of unburned carbon by flotation was studied with respect to adsorption ability in surface of a bubble in order to consider its application to recycle the coal bottom ash. The sample A, B and C were that the coal bottom ash contained 2.73%, 7.01% and 10.49% of the unburned carbon (UC) respectively. The column flotation was carried out for each time as the artificial injection of air at 10.0L/min flow rate and the reagents of 500g/ton kerosene and 80g/ton MIBC were used. The samples per water of 1.3 liters were from 0.5% to 4% (w/w.%). In the result of this study, the kinetic curves of unburned carbon adsorption from injected air bubbles were in-creased rapidly as equilibrium was approached; only 5 sec was needed from the sample A and B and 10 sec was from sample C. And the equilibrium isotherms of unburned carbon adsorbed by the infected air bubble from the sample B and C could appear the BET adsorption isotherm; MT = KMEEO/(EO-E)[EO+(K-1)E](K: adsorption affinity), but not the sample A that was not enough to express the adsorption curve.

Jan 1, 2014

By Y. Q. He

The dynamic behaviors of the air bubbles in the dense gas-solid fluidized bed have a significant effect on the performance of dry coal separation. The combined method of experimental measurement and numerical simulation were conducted to conduct the research of the mean diameters and rising velocities of the bubbles in the fluidized bed. The calculation models of mean diameter and rising velocity of the single bubble were proposed. The results indicate that the models of the mean diameter raised by Rowe (1976) and the rising velocity raised in this work could be used to predict the bubble dynamic parameters in gas-solid fluidized bed. With the Geldart B type of magnetite powder as the medium solids and while the gas velocity of 1.5Umf=U=2.2Umf, the mean bubble diameter along the bed height is 36mm<Db<45mm, and the mean rising velocity of the single bubble is distributed in 40~65cm/s. The results of experimental measurement, numerical simulation and model predication provide well agreements finally. Based on the uniform fluctuations of air bubbles diameters and their rising velocities, the separation experiments of 50~6mm dry coal using the mixture of 0.3~0.15mm magnetite powder and <1mm fine coal as medium solids were carried out. The results show that the probable error, E is 0.06, which indicates a good separation performance by using the gas-solid fluidized bed. Keywords: dense gas-solid fluidized bed, bubble dynamic behaviors, numerical simulation, separation performance

Sep 1, 2012

By Achilles Dutra, Everton Santos, José Oliveira

The beneficiation of phosphate ores by froth flotation is the most efficient process used to separate apatite from gangue minerals like calcite, dolomite and quartz. However, the similarity of surface properties between apatite and calcite generally lead to non-selective adsorption of reagents, rendering the selective separation of these minerals a worldwide problem. The phosphate deposit of Itataia, State of Ceará, Brazil, studied in the present work, presents a complex mineralogical composition having uranium associated with the apatite mineral. The main gangue minerals are calcite and quartz. The bulk flotation of apatite and calcite with anionic collectors in an alkaline medium followed by the selective flotation of calcite at pH 5.5 using phosphoric acid as well as citric acid as depressant have been suggested for this ore. This paper presents the results of contact angle measurements obtained using jojoba oil, a natural reagent composed mainly of gadoleic acid (C20:1) and long-chain fatty alcohols (eicosenol and docosenol), as an alternative collector for the selective separation of apatite and calcite minerals. The hydrophobicity studies were carried out using a computer controlled contact angle goniometer. Additionally, the collector adsorption was evaluated via electrophoretic mobility and FTIR measurements. The results indicated that a high selectivity can be obtained by using jojoba oil as collector in a slightly acid pH range, without the use of depressant. The best results were achieved with a jojoba oil concentration of 200 mg.L-1 at pH 6.5, where the apatite was fully hydrophilic and calcite showed a high hydrophobicity (? > 60 º).

Jan 1, 2014

By J. K. Afidenyo

Microbial pretreatment of a double refractory gold ore was investigated using a white rot fungus, Coriolus versicolor (ATTC 20869) to improve gold extraction. A series of preliminary tests were conducted to determine the amenability of the ore to fungus degradation. Pulp density, temperature, pH and retention times were the process variables considered. Both a single. Stage and two-step processes were studied to establish process conditions. During the single stage process, the ore was contacted with the fungus culture (biotic) for 3weeks at 30°C and pH 10.0. For the two-step process, the first step involves ore contact with the culture medium (abiotic) at 45°C and pH 10.0 followed by fungal contact (biotic) at 30°C. Results indicated that carbonaceous matter is not degraded but passivated by the fungus; as preg-robbing activities dropped significantly from 18.1% to below 1.0%. The single stage process resulted in higher gold recovery than the two-step process Gold ex-traction by cyanidation of the pretreated ore was 78.9% for the single stage compared with 15.0% for the untreated ore. In the two-step process, only 73.3% gold extraction was achieved. Application of the two step process conditions to a high grade flotation concentrate, resulted in 93.3% gold ex-traction as against untreated concentrate of 30.5%. The results show that the microbial pretreatment process degraded sulfide sulfur, passivated carbonaceous matter and enhanced gold extraction from double refractory gold ore and concentrate.

Jan 1, 2014

With shortage of sulfide nickel ores, laterite ore was paid more attention by scientists. Because its grade is commonly lower than sulfide nickel ores, laterite ore can not be utilized effectively be-coming the bottleneck of study. Leaching laterite ores from Yuanjing, Yunnan province, organic ac-ids show better selective than sulfide acid in nickel and cobalt recovery. Organic acid has low de-pendent on pH, keeping leaching capability even higher than 3. On the other side, when pH up to 2, sulfide acid can not leach laterite ores any more. After four kinds of organic acid leaching laterite ores, besides citrate, malate and succinate have good leaching and effectively selective capability. Especially, succinate has the best selective leaching capability of nickel and cobalt in four kinds of organic acids for latter anion purification and separation. Isolated from waste water with sugar, Aspergillus niger (zs1) has great capability to produce organic acids and vigorous growth. Laterite ores have been respectively processed by direct-leaching and indirect-leaching. Indirect-leaching gives a better result than direct-leaching. Extraction of nick-el by indirect-leaching reaches 44.3%, far more than that of direct-leaching. Moreover extraction of nickel at pulp density of 5% is higher than that at pulp density of 10%, reaching 63% in 11 days and extraction of cobalt also is 48.1% in the same period. Compared with nickel and cobalt, iron gives low extraction in solution, containing organic acids produced by Aspergillus niger .

Jan 1, 2014

By Yuri Yemelianov, Stanislav Balikov, Alexander Epiforov, Andrey Boldyrev, Andrey Bogorodsky

"Test work was carried out using copper gold-bearing flotation concentrate with 6.85%Cu, 14.30%Fe, 20.70%S and 2.34%As. Gold and silver grade in the concentrate is 54.6 g/t and 92 g/t, respectively. Gold and copper are valuable components in the concentrate. Gold is partially associated with pyrite and fahlores. Copper in the concentrate can be found as tennantite (Cu12As4S13). The 71% of gold from the flotation concentrate is recoverable by cyanidation with simultaneous cyanide consumption in the amount of 96 kg/t. The major reason of refractoriness is that gold is fine encapsulated into sulfides and the presence of cyanicide-copper. The concentrate ground as much as 95% minus 10 µm was treated using low-temperature POX at the temperature of 100±5°C, L:S ratio of 5:1 and the process time of 1-5 hours. Residual sulfide sulfur in the cake is 2.28% which is 89% sulfide oxidation. The highest copper recovery to POX solution is 91%. It was found that gold recovery to cyanide solution is 85-94% during alkaline pre-treatment of POX cakes followed by cyanidation. In this case, cyanide and lime consumption is 75-90 kg/t and 120 kg/t, respectively. In order to recover precious metals from POX cakes leaching using sodium sulfite was carried out. Test work was conducted at varied reagent concentration, L:S ratio and leaching time. Gold and silver recovery achieved was 85-95% and 59-63%, respectively."

Jan 1, 2014

By X. Q. Cao

As the second largest phosphate resource in the world, Chinese phosphate ores generally grades with low of P2O5. The presentation of beneficiation test on the low grade of phosphate rock in this paper may be used for a reference for development and utilization of the similar reserves. The ore is a marine sedimentary phosphate rock containing low grade of P2O5 and high content of MgO and R2O3; The banded structure shows its suitability for heavy medium separation. The laboratory heavy liquid testing results indicate that as specific gravity of the heavy liquid is 2.85 g/cm3, a rougher concentrate assaying 28.71% P2O5 could be obtained while the rougher tailings contain only 4.47% P2O5. When the combined process with heavy liquid separation followed by direct & re-verse flotation is employed to treat the feed containing 21.15% P2O5, 3.79% MgO, 1.86% Fe2O3, 3.66% Al2O3, 23.75% A.I, and specific gravity of heavy liquid is 2.84 g/cm3, the optimum mesh of grind is 67.5% minus 200 mesh, a phosphate concentrate contained 32.51% P2O5, 0.48% MgO, 0.81% Fe2O3, 1.69% Al2O3 can be produced at a yield of 55.24%. The concentrate P2O5 recovery is 85% with which quality comply with the Class A specifications for production of phosphate fertilizer.

Jan 1, 2014

By M. Abdollahy

Solvent extraction of gallium from Bayer solution of Jajarm Alumina plant was investigated us-ing Kelex100 as extractant. Taguchi experimental design method was used in order to optimize the separation factor of Ga and Al. Optimum conditions were obtained as follows: Temperatuer: 65°C, volume ratio of aqueous phase to organic phase: 3.0:1.0, process time: 60min and organic phase containing 15vol.% Kelex100, 5vol.% isodecanol in kerosene. In this conditions, 74% gallium and 0.3% aluminum was extracted and separation factor was obtained 828.63.

Jan 1, 2014

By Elena L. Chanturiya, Vladimir A. Bocharov, Roman A. Amosov

"In many volcanogenic base metal deposits of Russia the gold is closely associated with copper sulphides and pyrite. The recovery of gold associated with pyrite is especially difficult problem.Investigations of gold chemical state and mineral forms in copper-zinc sulphide ores of Gay and Barsuchiy Log deposits in the Urals have been made using EPMA, optic image-analysis, XRA, SEM, thermo-electrical force measurements and selective gold leaching experiments.Two gold varieties are determined: 1) free native gold particles (from 5 µm up to 0,25-1,0 mm), which can be liberated after grinding of ore up to 0,074 µm and named “free gold”; 2)”invisible” gold, including finely disseminated native gold and chemically bound gold. The second variety can’t be disclosed during grinding. Free gold can be recovered by gravitation and flotation while the processing behaviour of “invisible” gold is determined by properties of gold-bearing sulphides: pyrite and chalcopyrite. According to results of diagnostic leaching experiments in ores of deposits mentioned above the part by weight of free gold reaches 70%, the part by weight of the ”invisible” gold is up to 20%. About 10% of gold is enclosed in quartz and acid-soluble minerals.Theoretically (taking into account gold distribution data) it’s may anticipate gold recovery by gravitation up to 60%. However after grinding up to 50-60% of class –0,074 mm only about 40% of gold passes into oversize product including 30% of free gold and 8% of ”invisible” one. It can be recovered by gravitation. Remaining free gold and ”invisible” gold can be extracted by flotation – 25% in total. Inevitable gold losses in tailings may reach 8-10%."

Jan 1, 2003

The present study investigates the nature of gold mineralogical distribution and association in a Cu-Au flotation circuit (1.6 g/t Au, feed head grade). The approach used in this study involves a combination of bulk gold assay and quantitative X-ray diffraction (QXRD), on a size-by-size basis, followed by QEMSCAN analysis on the -75+53 µm, -53+38 µm and -38+20 µm size fractions. The QXRD and QEMSCAN analysis showed that gold mineralogy is complex and fine-grained in the flotation feed, particularly in the -38+20 µm size fraction. Gold and pyrite concentration follow each other closely, suggesting gold-pyrite association. Quartz as the major gangue mineral shows a bi-modal distribution with respect to particle size. The identified gold particles were completely locked (~94 %) in pyrite as fine inclusions and 6 % locked as complex aggregates (-75+53 µm size fraction) whereas in the -38+20 µm size fraction, the identified gold grains occur as fine inclusions (~1-3 µm) within pyrite and silicates. However, in the intermediate size fraction (-53+38 µm), 75 % of the identified gold grains (10-22 µm) were over 90 % liberated and 25 % associated and locked in pyrite and complex aggregates (~2-4 µm). The identified gold grains in the -53+38 µm size fraction occurred as native and electrum with varying silver concentration between 8 and 20 % by weight. In the -38+20 µm size fraction, a gold telluride was also identified. Based on the mineralogical analysis of the feed, possible flotation strategies are discussed. Optimizing the flotation of pyrite is suggested as the primary Au recovery strategy. Keywords: flotation, pyrite, gold, liberation, QXRD, QEMSCAN

Sep 1, 2012

By Q. R. Chen

Wet processes are commonly used in coal preparation field home and abroad. Dry coal cleaning technology is very necessary in China because more than 2/3 of coal resources deposited in arid areas, which are difficult to separate coal with wet processes. A particular interest of this article is the discussion of separation research development of dry coal cleaning in China, such as an air dense medium fluidized bed (ADMFB) beneficiation technology, a compound dry (pneumatic) separation technology and a triboelectrostatic separation technology. The fundament and importance of dry coal cleaning methods above were introduced. On the basis of analyzing parameters which influence the performance of separators, including that of structure, technologic and operating, the separation research status of dry coal cleaning methods, especially the ADMFB beneficiation technology, were discussed and reviewed. The recent developments, especially the fluidized bed beneficiation for <6mm fine coal with an external energy assisted, including a vibrated fluidized bed and a magnetically fluidized bed, and the triboelectrostatic separation for <1mm fine coal are also introduced. The study and application results in China show that dry coal cleaning technologies can efficiently beneficiate different coals with different sizes. The ADMFB can separate >6mm coarse coal with an E value of 0.05~0.08, the external energy assisted fluidized bed can separate <6mm fine coal with an E value of 0.07~0.09, the triboelectrostatic technology can efficiently separate <1mm fine coal, and the compound dry separation technology can efficiently separate >3mm coal with a easy washability. The dry coal cleaning provides an efficient and lower cost clean approach for coals distributed in arid areas.

Jan 1, 2014

By X. S. Yuan

With a demand for increasing energy efficiency and a need for improving bitumen recovery, a highly integrated solution for sustainable lease development of Aurora North of Syncrude has been proposed and implementation plans are underway. Flocculation and thickening technology as an important component of the integrated solution provides Syncrude an opportunity of rapid heat recovery from tailings and more flexible tailings closure and reclamation options. Flocculation of fine-particle suspensions by polymers is a non-equilibrium process whose performance is strongly influenced by physical and chemical variables. While polymeric flocculants are frequently used to establish the chemical conditions favorable for flocculation, the actual performance of a flocculation process generally depends more on the physical variables, such as the hydrodynamic conditions in mixing the flocculants and slurry. In order to study the effect of hydrodynamic conditions on flocculation of Syncrude fine tailings, a standardized laboratory test procedure called power flocculation has been developed in comparison with the conventional manual mixing methods. It is shown that the agitation speed and time in conditioning the flocculant solution and the slurry have a profound effect on the flocculation performances measured by initial settling rates, supernatant clarity and sediment density. It was found that the optimum bench test conditions for power flocculation of Aurora fine tailings with a sand-to-fine ratio (SFR) of about 1:1 are conditioning of the flocculant solution and the tailings slurry at 250 rev/min to 300 rev/min in 20 s to 40 s. The test results are inter-preted with a flocculant adsorption/redistribution kinetic model that helps understanding of the effect of hydrodynamic conditions on flocculant adsorption, floc formation and floc growth.

Jan 1, 2014

By Sebastian Fredes, Williams Calderon, Mauricio Toledo, Gonzalo Montes-Atenas

The influence of the temperature on leaching kinetics of copper-bearing minerals has been widely acknowledged: the leaching of copper oxide ores is generally described as exothermic reactions while copper sulfide ores are associated with endothermic reactions. Reports studying the influence of temperature on leaching kinetics at laboratory scale frequently involve the implementation of either fully flooded isothermal systems or jacketed column setups. Nevertheless, at industrial scale controlling or monitoring the temperature or temperature changes is almost impractical. In fact, leaching process is usually a large tonnage operation and changing the temperature of vast amounts of material would require an enormous amount of energy and highly specific heat transfer equipment. Preliminary computations on the amount of energy required to increase the temperature of a heap or dump in 1°C indicates that it would be impossible to find an energy source able to accomplish the task. In order to provide a solution to this matter it is suggested to create an energy managing protocol (EMP) that permits heat up or down the porous body locally taking advantage from the temperature gradients and from the reactivity of different regions within the material as a function of the leaching cycles. The aim of this study is to evaluate different heat transfer regimes in a 1 ton pilot column leach operation. It was found that best results of copper recovery are obtained when heating up the column in horizontal bands starting from the top of the column moving downwards as the leach cycle evolves. The system is expected to be suitable for industrial applications, but further development of the technique is required, particularly in the design of the heat transfer dispositive.

Jan 1, 2014

By Wayne van Drunnick, Mervyn Ruthnasamy, Olvier Guyot, Christophe Bouché

"Anglogold’s Mponeng Mine is situated in South Africa’s North West Province approximately 80km from Johannesburg. The reefs being mined in this area are among the deepest deep level mining operations in the world. These shafts often exceed several thousand meters making these operations complex and expensive.The gold plant is fed with run-of-mine ore which is stored in mill silos. Feedrate to the mills is controlled by a variable speed belt. Three parallel SAG mills (4.85 x 9m) treat 80-100tph, operating in closed circuit. Hydrocyclones classify the mill discharge, returning the oversize to the mill feed. Cyclone feed density and pressure are measured and are used with typical control loops to determine water addition rates to the mill. Control loops at PLC/SCADA level were historically used with limited success in the control of the milling circuits. Mill control for an installation of this type used mill mass (measured by load cells) and feedrate to control throughput. An online particle size analyser (PSI) was installed to assist grind control in tandem with pressure/density control on the cyclones. Although the accuracy of the measured grind was reliable, long term consistency of the PSI could not be guaranteed. Economic pressure from the business sector requires consistent mill throughput at optimum grind conditions. Fluctuations in production targets can manifest due to inconsistent control and the lack of real-time information from the process.This sensitivity to process movements may vary between shifts and also with changes in ore competency.Whilst tools are available to improve control, few have the sensitivity to process movements to provide real-time information for optimal grind control. For this reason an Advanced Control solution was sought. Advanced Control is often described as the supervision of basic PLC/SCADA control. Advanced control systems have to seamlessly compliment the existing control strategy and bridge the gap that exists between basic control and optimised control. A solution was found in the Metso Minerals CISA’s OCS (Optimising Control System). This French designed system makes changes to process setpoints to achieve peak performance and is distinguished from others by its soft sensor capabilities. The soft sensor is an embedded module in the OCS package that can be configured to estimate values normally obtained from field instruments. Advanced control using a Fuzzy Expert System assisted by Statistical tools (such as moving averages and a Soft Sensor using Phenomenological Models) would serve to bridge that gap. Metso Minerals CISA’s OCS is a modular system with various capabilities.It was successfully used to provide on-time process information via Soft Sensors. Circuit stability was achieved using Rule Based Expert Control in complete synergy with Fuzzy Logic. Two rule-based strategies were developed for this circuit. The first uses the online product size analyser as a primary control variable. The second uses a calculated kWh/t value and a modelled mill discharge density as primary control variables. The latter had more availability than the particle analyser and is currently in use."

Jan 1, 2003

By L. Filippov

"Nickel is an important metal with the total global consumption of about 2 million tons per year. It is sourced from both sulfide and laterite ore, but currently laterites are becoming more attractive for nickel production due to the depletion of high grade nickel sulfide ores. Laterites are generally processed by hydro or pyro-metallurgy and therefore, pre-concentration of nickel before such processes is very important. In this paper the effect different physical methods (including flotation) on the pre-concentration of nickel in laterite ores will be discussed. The ore used in this study was a laterite from South East Asia. Nickel was upgraded using different methods such as magnetic separation, flotation and sizing. The effect of ore mineralogy on choosing the best strategy to upgrade nickel will be discussed. The findings of this project will help to unlock a substantial volume of nickel with significant value from laterite ores.INTRODUCTION Nickel is an important metal with the total global consumption of about million tons per year which has grown rapidly during last decades (Mackey, 2011). Nickel is sourced from two different types of ores, sulfide and laterite. The majority (about 70%) of the world’s nickel resources occur as laterite ores which are often complex, and low grade, and therefore expensive to treat using conventional methods (Xu et al., 2013). Today, nickel laterites are more attractive for production of nickel as the amount of high grade nickel sulfide ores has diminished (Janwong, 2012). Therefore more economic processes to recover nickel from these resources should be developed.It should be noted that nickel laterite mineralogy is complex, and nickel often presents as ultrafine inclusions in a number of mineral phases. Because of the low nickel concentration and variable distribution in these phases, effective upgrading by physical separation processes would be challenging. Researchers have tried to improve nickel laterite flotation recovery by using a number of feed preparation techniques. A summary of the nickel grades obtained using flotation and magnetic separation as reported in the literature is presented in Table 1. It can be seen that only minor nickel upgrades have been reported. Quast et al. (2015) have concluded that the complex mineralogy of nickel laterite ores makes it difficult to achieve any significant nickel upgrading by physical techniques, including flotation. They achieved 40% increase in the nickel content (from 1.0% to 1.4%) at a nickel recovery of 43% (Quast et al., 2015). Various attempts in USA, New Caledonia, India and Australia, to upgrade nickel in laterite using magnetic separation have not been successful (Quast et al., 2015). A recent comprehensive review on topics influencing nickel laterite flotation has shown that further investigations in the flotation of laterite ores are undoubtedly warranted (Farrokhpay & Filippov, 2016)."

Jan 1, 2018

By X. L. Song

In this paper, ZrSiO4-Cd(S1-xSex) inclusion pigments were synthesized by hydrothermal method. Microstructure, morphology and properties of the powder were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), infrared spectroscopy (IR) and CIE chromaticity, respectively. It shows that, precursors obtained at pH is about 6.0 are sol and products with higher crystallinity, red hues (a*=38.23) and inclusion ratio when hydrothermal synthesis temperature is 180? and holding time is 12h. Hydrothermal reaction mechanism was further analyzed as well. In particular, an ideal model of pigment formation was proposed.

Jan 1, 2014