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By Anjan Kumari, B. K. Soni, Manis Kumar Jha, A. Vidyadhar, Vinod Kumar

"In the present paper, recovery of valuable metals from the poly-cracked ash obtained by pyrolysis of discarded PCBs has been studied following physical beneficiation and a hydrometallurgical process alternate to smelting. The ash is subjected to comminution for the separation of metallic components from non-metallic fractions by scrubbing, tabling and froth flotation which enriched the metal in the concentrate -97% which was further screened to separate high and low metal concentrate. The finer fraction containing -12% metallic value was leached in acidic solution. Almost all (Cu, Pb, Fe, etc) were leached in 4M HN03 at 90°C in 75 min at a pulp density 100 g/L. The characterization of both ash and residues were made by XRD, EPMA, EDS, etc. to validate the experimental results. The metals from the leach liquor could be recovered/separated using solvent extraction techniques which can further be processed to get pure metal salts/ sheets.IntroductionPrinted circuit boards (PCBs) are an essential component of electrical and electronic equipments (EEEs) as it plays an important role during operation of these devices. The world market of PCBs has reached nearly $60 billion in 2012, with 1.7 percent real growth over 2011 [1]. The diverse technology-driven global market is expected to grow at an average annual rate of 5% by 2014 [2]. The waste EEEs are generated due to replacement of obsolete equipments with modem ones and thus their demand is also increasing rapidly [3]. The discarded e-wastes are being piled up as landfills which affect the environment and cause health threats to living organisms, if not disposed of properly. These e-wastes contain metals some of which are precious, few are hazardous and others as valuable."

Jan 1, 2014

By Alex Heath, Andrew Barycki, Baladron. Javier

"Efficient flocculation is important to thickener performance, affecting the overflow clarity, solids settling flux, underflow density and operability. Many factors affect flocculation; from the material/flocculant type, dilution of the feed and flocculant solution, mixing, to the shear rate and shear history. The flocculant addition point (or points) can be used as a tuning method to alter the effective flocculation time in a feedwell, with addition further up the feed pipe increasing the residence time but making the aggregates more prone to breakup if they experience high shear later in the process. Conversely, adding the flocculant later, eg under the feedwell shelf decreases the mixing time but allows some free (unadsorbed) flocculant to be available at the feedwell exit. An extensive trial has been performed on an operating thickener comparing seven individual different flocculant dosing positions through a Vane feedwell, and some combinations of two dosing points simultaneously. Measurements of the velocity, solids concentration and aggregate size were made throughout the feedwell at the different positions, with the dosing points significantly changing the aggregate size and clarity, and also affecting the solids concentration at some positions. The results are accessed in terms of flocculation kinetics and used as CFD validation data."

Jan 1, 2014

In this paper High Pressure Grinding Rolls(HPGR) was utilized to pretreat CVRD southern specular hematite for enhancing the pelletization of the refractory hematite. The process parameters of HPGR, balling and firing were optimized, and the mechanism of HPGR was demonstrated by determining the surface activity by means of Blaine specific surface area tester, laser size analysis, scanning electron microscopy (SEM),X-ray diffraction (XRD), micro calorimeter and pelletability index. It is shown that the pelletization of the refractory hematite was greatly improved. The drop strength of green balls increases from 3.4 times to 13.6 times from 0.5m height while the bentonite dosage decreases from 2.2% to 1.3%.The compressive strength of roasted pellets also reaches 2500N/pellet. The mechanism of the pretreatment of CVRD southern specular hematite concentrates by HPGR is revealed that the surface activity is improved by an increases in specific surface area and the amount of micron size fractions, and higher lattice deformation and defects due to the fractures occurring inside particles during static pressure comminution, resulting in more wetting enthalpy, higher pelletability index and good property of roasting.

Jan 1, 2014

By Seher Ata

This paper is concerned with the coalescence behaviour of two bubbles in dilute solutions of cetyltrimethylammonium bromide, methyl isobutyl carbonil and triton x-100. Two bubbles were produced at the tips of adjacent capillaries and the time elapsed between the first contact of the bubbles and film rupture was determined by means of a high speed camera. It was found that the amount of surfactant required to stabilise the bubbles increased in order of CTAB>TX-100>MIBC. The probability of coalescence decreased sharply with increasing surfactant concentration in CTAB and TX-100 solutions while with MIBC each bubble pairs resulted in coalescence, giving hundred per-cent coalescence probability.

Jan 1, 2014

By Josefin Lannefors, Anders Klingberg, Natalija Gorochovceva

"Development of new anionic collectors becomes more and more important. This can be explained, on the one hand, by the fact that over the years phosphate ores have become more fine grained and complex (example weathered). On the other hand, a development with a focus on sustainability (sustainable development) of new anionic surfactants is required by authorities and society. Within the sustainable development several characteristics of a collector have to be taken into an account: efficiency, selectivity, froth characteristics, environmental profile, raw materials used for the synthesis, manufacturing complexity, stability upon storage, etc.Several anionic surfactants based on ester and amide chemistry were synthesized, characterized and used as flotation agents for calcium phosphate containing ore. The surfactants were used in a formulation together with other anionics, since in a pure form, during the flotation, they did not provide right froth characteristics.A new anionic collector/formulation was developed, that fulfills all above listed requirements."

Jan 1, 2014

By Steve Kral

"The Rapid Excavation & Tunneling Conference (RETC) is a world-renowned event that attracts some of the best minds in the global underground construction and tunneling industry. The experts gather at this conference to impart new technologies, discuss challenges to their projects and learn about new technologies that have become available to them.The 2015 RETC will be held June 7-10 at the Sheraton New Orleans, in New Orleans, LA. This biennial conference, of which SME is a sponsor, is expected to attract about 1,400 attendees from around the world. These professionals represent all parts of the global tunneling and underground construction industries - contractors, engineers, owners, consultants and equipment suppliers.More than 110 technical papers in 21 sessions will be presented over two-and-a-half days. Paid attendees will receive a proceedings volume of the conference. The proceedings will also be available from SME. In addition to the technical programming, the accompanying exhibit will include 155 exhibitors occupying 175 booths, providing RETC attendees the opportunity to get a look at the latest in equipment and service technology. Three short courses will be held on the Sunday preceding the start of the show. And there will be plenty of opportunities for attendees to meet and chat during several social activities that are scheduled throughout the conference."

Jan 1, 2014

By A. Wieniewski

The observed progress in technology of non-ferrous ores enrichment and condition of machines and equipment in the ores concentrators on the one hand have brought a possibility and on the other resulted in necessity for introduction of modernization actions. Positive results of investigations into influence of chemical modification of selected products of enrichment process on copper ores enrichment results gave possibility for implementation of chemical-flotation technologies of ores enrichment. The substantial development in flotation machines structure has contributed to modernization of flotation process resulting in increase of enrichment efficiency. The paper presents the idea and results of chemical modification of difficult in enrichment semi-products in the technology of copper ores enrichment and the results obtained after application of the modernised technology. The structure of large-volume flotation machines used in various stages of flotation and current situation in modernization of flotation process in copper ores concentrators are also described. The paper presents industrial-scale results of flotation after application of modified flotation reagents of collector group. Introduction of modifiers into the widely used xanthates resulted in increase of copper recovery in concentrate.

Jan 1, 2014

By Cesar A. Urbano Jr., Gretchen T. Lapidus

A series of experiments examined silver extraction from a high-grade sulfide concentrate employing thiourea solution. Thiourea was initially oxidized with hydrogen peroxide (H2O2) to form formamidine disulfide (FADS) and used to extract silver from the as-received concentrate and after various pretreatments. Very low recoveries (~30%) were obtained with the as-received concentrate due to competitive cementation reactions by metallic iron and easily oxidizable copper phases. Over 80% Ag recovery was obtained when the concentrate was pretreated to remove this iron and copper. The results suggest that an oxidative acid pretreatment of this concentrates significantly improves silver recovery upon leaching with thiourea.

Jan 1, 2014

By Rui Mao, Ke-Xin Nao, Jian-Liang Zhang, Xiang-Nan Xu, Meng-Fang Wei

"In this research, fundamental characteristics of dust and sludge containing iron from the dusting system of sintering process, blast furnace, oxygen converter and rolling process in steel enterprise were studied by chemical analysis, X-ray diffraction analysis, optical microscope analysis, scanning electron microscopy analysis, particle size analysis and other analysis means. Development direction of resource utilization for dust and sludge containing iron from steel enterprise was put forward on the basis of above study.IntroductionDust and sludge containing iron for steel enterprise mainly come from the dusting system of sintering process, pelletizing process, blast furnace, oxygen converter, rolling process and other related process. Iron content of dust and sludge is between 30% and 70%, and they also contain certain content of carbon, calcium oxide, magnesium oxide and harmful elements [1-3]. Output of dust and sludge is determined by raw materials conditions, technological processes, equipment configuration and management level. Dust output in sintering process accounts for about 2% to 3% of the sinter production, while dust and sludge from iron making and steel making process respectively take up 3% to 4% of hot metal and crude steel production, and the solid waste from rolling process accounts for about 0.8% to 1.5% of the output of rolled products [4,5]. Dust and sludge contains Fe, CaO, MgO, C and other valuable resources, it will not only result in the waste of resources, but also cause serious pollution to environment ifthe dust and sludge are not recycled. China's crude steel production in 2012 is about 700 million tons and output of dust and sludge containing iron is nearly 60 million tons, so, it is of great significance to have a resource recycling for dust and sludge containing iron from steel enterprise."

Jan 1, 2014

By Chee Theng

"So many talks, so little time.One of the toughest challenges associated with attending the SME Annual Conference and Expo is deciding how to allocate one’s resources. After accounting for keynote and plenary sessions, committee meetings, networking events, luncheons and exhibits, attending even one of the 109 technical sessions and more than 600 technical paper presentations can be a labor of love. Many, however, managed to make it to many of the sessions, including the mineral and metallurgical processing technical session on solvent extraction, ion exchange and electrowinning.At one point, that room was seated to near capacity, with a considerable number of the audience members standing by the walls at the back. Brittany Valera of Freeport-McMoRan Inc. was one who came early and enjoyed the session in its entirety. "Everything was pretty exciting," she said. "I really liked the modular plants. I think the future of mining, just like what we talked about in there, lies in thinking about things like remote locations, lifetimes of plants, anything that would be reusable and sustainable; and lower-cost and user-friendly would be really beneficial."Michael Moats, associate professor of metallurgical engineering at Missouri University of Science and Technology, started off the session by presenting on behalf of post-doctoral student Alex Luyima, who, like many before him, had been snapped up by industry and is now working for a secondary-metals refining company in Texas. Their team studied the nucleation and growth mechanism of copper on stainless steel from synthetic acidified copper sulfate in the absence and presence of chloride ions and three commercial organic additives: Hydrostar 4208, DXG-F7 and Cyquest N-900. Currenttime data were analyzed using known models, with reference to scanning electron microscope images. Good agreement was achieved between the models and SEM micrographs of deposits at a commercially relevant current density of 30 mA/ cm2. The addition of 20 mg/L chloride was found to increase the size and reduce the number of nuclei. The addition of 2.5 mg/L of each additive did not change the mechanism, but all three reduced the size and increased the number of nuclei, leading to more uniform coverage of the substrate with smoother deposits produced in twohour electrowinning experiments. N-900 had the best deposition coverage while DXG-7 was the easiest to dissolve."

Jan 1, 2014

By Z. M. Dai

Microorganisms in AMD (Acid Mine Drainage) were enriched in 9K culture medium. The enrichment was applied to leach copper pyrite after the microbial community structure and metabolism was stable. Before and after bioleaching, the microbial DNA was extracted and applied to RFLP (restricted fragment length polymorphism) analysis to demonstrate the relationship between the leaching efficiency and the change of microbial community. Atomic absorption spectrometry results showed that when concentration of the pulp was 10% and pH were 1.5, 2.0 and 2.5, the leaching rate were 56%, 57% and 34% on the 18th day respectively. These results indicated that the rise of pH resulted in the decrease of leaching rate. In lower pH condition, the growth of microbe was faster: when pH was 1.5, the microbial cell number reached to 1.4×107cells/mL on the 9th day; while pH was 2.5, the microbial cell number decreased to 4×106cells/mL. The analysis of microbial community structure showed that Acidithiobacillus ferrooxidans and Leptospirillum ferrooxidans were dominant species before bioleaching (account for 43% and 32% respectively). And after bioleaching, these two species were still dominant when the initial bioleaching pH were1.5 and 2.0. While the initial bioleaching pH was 2.5, the proportion of these two species decreased. These results demonstrated that the initial bioleaching pH would affect the microbial community structure in bioleaching system at room temperature, and this affect could lead to different copper pyrites bioleaching efficiency.

Jan 1, 2014

By V. Sovmen

The gold-ore Olympiada deposit is located within the Yenissei range (Krasnoyarsk Region, Russia). Primary sulphides ores are metasomatic changed rocks, mica-calcite-quartz structure with impurity amphiboles, chlorites, carbon, the rare thin grains of sulfides (up to 3%~5%) and native gold. The structures of ores are fine-grained, prevailing texture of ores - interspersed, vein-interspersed, band-interspersed, veinlet. The most important minerals in the deposit are: gold, arsenopyrite, pyrrhotite, antimonite, Sb-sulphosalt, quartz, muscovite, calcite, siderite, titanium minerals, chlorite and minor sulfides like chalcopyrite, galena, sphalerite, etc. A common problem in mineralogical studies applied to mineral processing (concentration, cyanidation, etc.) is the characterization of gold in ores and technological products. This paper discusses the behavior of minerals during technological process at operating factory in Olympiada Mine and gold distribution in the ores and products. For the mineralogical characterization of minerals ? combination of analytical techniques was used. Gold is encountered in the primary ores as free grains among rocks, growth with sulfides and nonmetallic minerals, inclusions in sulfides, sulphosalt, and nonmetallic minerals. The gold-sulphide ores of Olympiada deposit can be quite complicated for enrichment. With the purpose to increase the extraction of metal from concentrates by liberating the dispersed gold, forming inclusions in sul-fides, there is used technology of biooxidation of flotation concentrates in Olympiada Mine. Gold and the basic ore-forming minerals in the ores feed, sulphidic concentrates, biocakes, tailings of concentrates of flotation and products of hydrometallurgical leaching have been studied in the mineralogical research. During researches it is established that pyrrhotite was completely oxidized while arsenopyrite was oxidized almost completely in the bacterial oxidation process. Pyrite and antimony minerals behave similarly and were oxidized only partially. The main oxyhydroxides in the bacterial oxida-tion process are goethite, limonite and jarosite. The results of mineralogical researches showed reasons of losses of gold during hydrometallurgical enrichment.

Jan 1, 2014

By B. W. Zhao

Quantitative analysis of minerals composing in ore is primary in process mineralogy, a veracious quantification and analysis is very crucial to optimize or design a beneficiation process, especially for a low grade and complicated ore. This paper will discuss a SEM-EDS based quantitative analysis developed in JKtech Australia through an example from Jinchuan lean ore. For a low grade, com-plex intergrowths and texture lean ore, chemical phase analysis of value minerals and identification by optical microscope are very essential, unite the SEM-EDS based quantitative analysis, we can understand exactly the lean ore, explain and quantify the process performance.

Jan 1, 2014

By Yuqing Feng, Ping Fang, Dezhou Wei, Zichuan Guan, Shuling Gao, Baoyu Cui

"Air core, as an inevitable phenomenon of rotational flow field inside hydrocyclone, has a major impact on hydrocyclone’s separation characteristics. The air core formation process, its structural features and its influencing factors were investigated systematically in this paper. Numerical study on the air core of a f50 mm hydrocyclone was carried out using a commercial computational fluid dynamics (CFD) modelling software package ANSYS/Fluent with the selection of Reynolds Stress Model (RSM) for the turbulence model and Volume of Fluid (VOF) for capturing the air-liquid interface. Physical experiments were conducted under the same geometry and operation conditions and the particle image velocimetry (PIV) technology was used to measure the liquid flow. The CFD results are compared with the experimental measurement with good agreement demonstrated. The air core was formed generally at around 0.7 s, air outsides of the air core was eliminated completely after 1.7 s. The centreline axial velocities and the water blocking hydrocyclone simulations showed that air of the air core entered the hydrocyclone from the underflow area and exhausted from the overflow area, but there was also some air flowing into the air core from the overflow area. The largest swing of the air core occurred on the top of the underflow pipe, and a protuberance similar to the shape of Adam’s apple appeared when the air entered the vortex finder. CFD simulation results also showed that the air core diameter was decided by axial position and parameters of hydrocyclone. The structural parameters have more effects on the air core diameter than the operational parameters."

Jan 1, 2014

By David De Klerk, Maximilian Richter, Thirunavukkarasu Pathmathas, Indresan Govender

We consider the average power dissipation distribution for dense granular flows of an idealised mono-sized charge (5 mm glass beads) in a 300 mm diameter tumbling mill operated in the cascading-to-cataracting Froude regime. By combining the inherent frictional nature of particles within a dense flow regime and noting that tumbling mills are typically characterised by collisional and turbulent stresses, we derive the power dissipation distribution for athermal boundary conditions. The input data to the model (velocity, solids concentration, pressure and flow depth) are obtained directly from non-invasive measurement using a nuclear imaging technique: Positron Emission Particle tracking (PEPT). The power dissipation due shear stresses is shown to be the dominant mode of dissipation in the tumbling mill with up to two orders of magnitude difference between pressure induced dissipation and shear.

Jan 1, 2014

By Michael Young, Rodrigo Araya, Cesar Gomez, Le Huynh, James Finch

The performance of flotation machines is closely related to the gas dispersion characteristics achieved in their operation. It is known that frothers play a major role not only in the size distribution of the generated bubble population, but also on the swarm rise velocity. A program to characterize frother effects on two-phase hydrodynamics (air-water) of Jameson cells was undertaken in a fully instrumented pilot unit installed at McGill University. Gas dispersion parameters (gas velocity, gas holdup and bubble size distributions) of the gas-liquid mixture generated in the downcomer were measured after its release into the separation chamber. The unit was operated under different conditions including gas velocity, liquid jet velocity and frother concentration (MIBC). Bubble size distributions for concentrations above the critical coalescence concentration (CCC) were narrow with Sauter mean diameter between 0.6 to 1.3 mm. The bubble size followed the general trend as encountered in other types of flotation machines, i.e., rapid decrease with increasing frother concentrations below 10 µL/L, and almost no change in size for concentrations above 30 µL/L. The CCC was between 10 and 15 µL/L. Strong correlations were found between bubble size and air-to-liquid flow ratio (APR), and between the bulk density of the aerated solution in the separation tank and the vacuum inside the downcomer. An equation is proposed to estimate gas holdup in the separation tank from vacuum and bulk density readings.

Jan 1, 2014

By Ross W. Seedsman

The logical framework recognises that a coal mine roof can be intrinsically stable or may collapse in one of four ways. Suspension of the immediate roof is one of fundamental ground control strategies available to a coal mine engineer and is recommended for three of the four collapse modes. Correctly implemented suspension offers the greatest improvement in roof stability and greatest reduction in longwall risk. For the control of maingates ahead of retreating longwall faces the ideal suspension support (if required) consists of angled, partially debonded, medium-length tendons installed as far behind the development face as practical. For situations where the roof may be subjected to tensile horizontal stress, immediate support by equally spaced short vertical tendons is required. The step away from fully-grouted tendons improves their survivability during the onset of compressive failure in the roof, minimises the risk of isolated loading, and allows a more robust TARP for roof movement. All suspension systems require a strap, sling or truss between the suspension elements.

Jan 1, 2014

By Artem Dolotov, Alexander Ter-Oranesyants, Saveliy Kaplan, Boris Axenov, Vasiliy Kovalev, Valeriy Tsyplakov, Konstantin Grigorjev, Nikolai Vorob’ev-Desyatovskii

The issues of double refractory gold ores pressure oxidation were considered. It was demonstrated that along with chloride autoclave preg-robbing which has been studied there are other negative external and intra-autoclave processes resulting in gold losses. It was found that an ingress of even low concentrations of NaCN, ferrum(II) and ferrum(III) cyanide complexes, as well as thiocyanate compounds into the autoclave leads to decrease of gold recovery during further cyanidation in a "carbon in leach" process (CIL). Admixtures depressing recovery of gold can get into the autoclave together with water in the result of industrial accidents or due to peculiarities of recirculation of industrial water used for feed pulp preparation or with quench-water used for process temperature maintenance. In contrast to a chloride preg-robbing which occurs only at pressure oxidation of double refractory gold ores, cyanide preg-robbing starts in the autoclave feeding tank (so-called «upper» preg-robbing). Possible causes of cyanide autoclave preg-robbing and requirements to the quality of water supplied to autoclaving were discussed.

Jan 1, 2014

By Longjiang Li, Mao Jiang, Zhihui Shen, Guizhou University, Yin Pan

This paper aims to study the influence and action mechanism of collector Y-89 on the flotation of auriferous pyrite. The measurement to identify adsorption quantity, IR and XPS spectrum analysis and flotation experiment made on the pure mineral were conducted. The research results show that when the dosage of MIBC is 20 mg/L, and pH of 8, the dosage of Y-89 over 60 mg/L, the pyrite recovery rate is greater than 80%.And when the dosage of Y-89is 60 mg/L, dosage of MIBC 20 mg/L, the pH in a wider range (pH=4~9), the recovery is greater than 75%. When the pH is above 10, the pyrite is depressed and its recovery rate is found to be dramatically dropping. Adsorption quantity measurement also shows that the strong alkaline conditions inhibit the adsorption of Y-89 on the surface of auriferous pyrite. IR measurement indicates that chemisorption of Y-89 occurs on the surface of auriferous pyrite. XPS spectrum analysis indicates that without adding Y-89, oxidation reaction occurs on the surface of pyrite. But when Y-89 is added, the chemical environment of Fe on the surface of pyrite has changed. Such findings indicate that with Y-89, chemisorption occurs on the surface of auriferous pyrite.

Jan 1, 2014

By J. E. Sepulveda, R. Morrow

"The Linear Wear Theory provides a reliable framework for the assessment of grinding media performance at full scale. This theory can be applied for analyzing grinding media consumption rates in any given grinding operation as well as the evaluation of alternative grinding media products, based on actual operational data, correcting for conditions like ore hardness, feed and product sizes, mill power and circuit throughput; all of them unrelated to the grinding media intrinsic quality attributes. A series of Moly-Cop Tools 3.0 applications have been developed to facilitate the calculations involved. Moly-Cop Tools 3.0 is available, free of charge, to all interested parties through the corresponding author.INTRODUCTION Mineral grinding circuit operators recognize the significance of grinding media (balls) consumption on the cost structure of any full scale grinding facility. The effective cost associated with this essential consumable depends on two factors: delivered price and durability (quality) of the grinding media. When evaluating alternative grinding media varieties, there is a well accepted evaluation criterion by which a given media type is considered to be “cost-effective” when its unit application cost – normally expressed in $/ton of ore ground – is shown to be lower than that of a nominal reference condition: Grinding Media Cost = Ball Price x Ball Consumption (1) ($ /ton ground) ($/ton balls) (ton balls/ton ground) Under this criterion, an alternative, higher-price grinding media product could be “cost-effective” if its associated consumption rate is sufficiently lower than the reference media, enough to yield a lower grinding cost, as dictated by Equation 1. For the proper application of the above criterion, evaluators must rely on representative indicators of grinding media quality, ideally independent of most mill operating conditions. In each particular case, ball price is always a known component; however, it is not so evident how media performance (quality) differences amongst alternative product types could be assessed with a reasonable degree of accuracy and precision."

Jan 1, 2014