Search Documents

By Mingming Zhang, Mallikharjuna R. Bogala, Ramana G. Reddy

Steelmaking desulfurization slag samples were characterized using chemical, X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS) methods. The objective of this work is to investigate the occurrence of sulfur and phosphorus components in the slag samples and to identify their origin and associations with the iron phases. Thermodynamic calculations results confirm the presence of phosphorus and sulfur components in the slag sample at high temperatures (1400 to 1800oC). The main constituents of slag include Ca3SiO5 (28.1%), MgO (9.31%), Ca3(PO4)2 (9.18%), CaS (8.39%) and CaO (5.68%). The major phosphorus and sulfur components of the slag are Ca3PO4 (99.2%) and CaS (79.3%) respectively. Characterization studies indicate the presence of microparticles of different sizes and shapes in the slag sample. Elemental analysis of these particles confirm the presence of major elements (O, Mg, Al, Si, S, Ca and Fe) in the slag sample.

Jan 1, 2015

By Alex Luyima, Honglan Shi, Lifeng Zhang, Yongqing Jiang

"Leaching process has been suggested to recover most metals from waste PWBs. In this study, the leaching behavior of most metals present in waste PWBs is evaluated before and thermal treatment. Different leaching acids: hydrochloric acid (HCl), nitric acid (HNO3) and aqua regia are compared. The effects of acid concentration, particle size of sample, leaching time and temperature are examined. Results revealed that most metals are present in small particle size and sequential leaching of PWBs with a combination of HCl acid and aqua regia is capable of dissolving most of the metals content of PWBs. Leaching of thermally treated PWBs produced the highest leaching percentages for similar leaching conditions.IntroductionApproximately 20–50 million tonnes of electronic waste (e-waste) is produced globally per year. Waste Electrical and Electronic Equipment (WEEE) or E-waste is one of the fastest growing waste streams in the world. In developed countries, it equals 1% of total solid waste on an average [1]. The growing stockpile of used and obsolete consumer electronics has been called the “largest toxic waste problem of the 21st century [2]. Printed wiring boards (PWBs) is an essential part of almost all WEEE, and accounts approximately 3% of all WEEE by weight [3]. PWBs are a platform upon which microelectronic components are mounted. PWBs contain metals (~40 wt. %), ceramics (~30 wt. %) and plastics (~30 wt. %) [4]. The metallic part includes; Cu, Pb, Zn, Fe, Cd, Be, Cr, Au, Pt, Pd, Ag, etc. The plastic part of the PWBs is mostly epoxy resins. These plastic resins also contain very toxic halogenated flame retardants (HFRs) [5]."

Jan 1, 2012

By V. J. Ramirez, A. M. E. Noguez, M. J. Navarrete, B. G. Salas, N. T. Robert

"The close die forging stress in truncated conical cavities is evaluated with dimensional analysis. Five dimensionless groups are proposed from the process variables in order to simplify the forging stress determination. These groups are experimentally related and graphically expressed. This methodology can be used to predict the actual forging stress in industrial close die forgingThe use of the dimensionless groups allow to comprise more cases than the presented here, provided similar geometries and operational conditions.Introduction.Closed die forging is essentially a plastic deformation inside a two piece mold (forging die) with the inverted shape of the actual forging geometry. This plastic deformation will always be the result of a compressive stress. There are theoretical models which include complex calculations for the analytical determination of stresses (1, 2, 3, 4). Results of these calculations are approximate, requiring generally ulterior tests to obtain the true operational conditions(5).In this paper, it is presented a simplified approach to the actual compression stress needed in the forging. A well known tool in engineering: the Buckingham's Pi theorem in conjunction with dimensionless groups and a working piece scale model is used. Dimensional analysis will give the dimensionless terms needed to experiment with a selected scale model geometry to make the stress determination. The results presented demonstrate the reliability of this methodology."

Jan 1, 1997

By ZhiLong ZHAO, Lin Lin, Zhancheng Guo, Jingtao GAO, Huiqing Tang

Grain sticking often occurs in the fluidized bed reduction of f ine iron ore, which is closely related to the precipitation morphology of metallic iron on the surface of ore particles. In this work, simulating the gas-solid reduction process of iron ore, in situ observations were carried out to investigate effects of doping mineral oxides on the precipitation morphology evolution of metallic iron during reduction of iron oxides with CO. Results indicate that the precipitation morphology of metallic iron is related to the quantity of doped mineral oxides. The minimum mole fraction of doped oxide ( xyOA N ) that can inhibit the growth of iron whiskers is related to its cation radius ( Ax r ), extranuclear electronic layers ( Ax n ) and valence electrons ( Ax q ). Their relation can be expressed as:

Jan 1, 2016

By J. Priede, G. Gerbeth

"Two different instability mechanisms of electromagnetically levitated bodies are analyzed. The first is due to the virtual coupling between the electric current passing through the magnetic system and the variation of position of the body. This mechanism can result in unstable mass center oscillations of a levitated solid body. Another type of instabilities may occur because of the coupling between the motion and the electric currents induced in the body. This effect can cause a spontaneous rotation of the body setting in as the frequency of the alternating magnetic field exceeds certain critical threshold depending on the configuration of the field. This instability can be suppressed by an axial steady magnetic field of strength comparable to that of the levitating field. 1 IntroductionAn alternating magnetic field interacting with eddy currents induced in a conducting body causes repulsion between the body and the coil generating the field. Besides, the eddy currents provide a contactless heating of the body. In such a way metallic samples can be levitated and melted without a contacting crucible. This technique allows to avoid contamination of the melt with container material and so to achieve a considerable super-cooling of the melt before it solidifies. Nowadays electromagnetic levitation is widely used in material research for measuring of the thermophysical properties of molten metals (2) .It has been observed since early fifties when the first experiments on the electromagnetic levitation were done that under certain circumstances solid levitated samples start to rotate or oscillate [l]. Surface oscillations can appear in addition when the sample is melted. Such phenomena are undesirable because they often result in failure of the levitation. Recently we showed that rotational as well as oscillatory instabilities can have electrodynamic origin related to additional eddy currents induced by motion of the body in an alternating magnetic field [3] , [4].In the first part of the present paper we analyze another possible cause of oscillatory instability due to the coupling between the electric current passing trough the magnetic system with variation of the position of the levitated body. The second part of the paper deals with the origin and suppression of rotational instability in a uniform alternating magnetic field."

Jan 1, 1999

By W. D. Keller

Scanning electron microscopy (SEM) accompanied by X-ray energy dispersive analysis (XES) is a useful tool in process clay mineralogy. The texture of kaolin, illustrated by SEM, gives a clue to its mode of genesis and probable industrial application. One type of kaolin, originating dominantly by weathering, has an open texture, slakes readily, and is used for filling and coating paper. Another type, in contrast, originates by diagenesis of Al-silicate sediments, and spectacularly resists slaking, thereby enabling it to maintain its bulk density and controlled size and shape of particles after crushing and moistening; this meets an important requirement for the manufacture of refractories. Ratios of elemental Al:Si that may be rapidly determined by SEM and XES yield information on the origin and purity of bauxite and bauxitic clays, and aid in quality control and processing of them. SEM of dissimilar textures of quartz, as in chert and novaculite, are evidence for geothermometry on a stratigraphic scale that is potentially useful in delimiting thermally favorable or unfavorable areas for hydrocarbon exploration, and possibly for unexposed metallic ore deposits.

Jan 1, 1982

By William Petruk

The primary requisite for a successful extractive metallurgy operation is to grind an ore fine enough to liberate the minerals so that they can be concentrated, or to expose mineral surfaces so that the minerals can be leached. The ease or difficulty of liberating or exposing the mineral grains is dependent upon the mineral textures such as grain size, crystallinity and bonding between mineral grains. In particular, mineral grains with straight grain boundaries and a weak bonding to other minerals are easily liberated and readily concentrated into high grade concentrates. In contrast mineral grains that have re-entrant boundaries and are strongly bonded to their neighbours are not easily liberated and will not produce high grade concentrates, even with regrinding. Similarly, inclusions that occur along fractures and grain boundaries can be readily exposed and leached. Whereas minute random inclusions in large grains will not be liberated or exposed unless they occur along planes of weakness.

Jan 1, 1995

By Varadarajan Seshadri

A physical model based on similarity principles was constructed for simulating the RH degasser of CST (Companhia Siderurgica Tubarao, Vitoria, ES, Brazil) to evaluate the circulation rate of the metal which essentially defines the degree of exposure of the metal to vacuum in the chamber and thus of the refining rate. The circulation rate on the other hand will influence the decarburization rate and removal of dissolved gases like nitrogen and hence it is essential to optimise this parameter to get maximum refining efficiency with minimum refming times, thus improving the productivity of the secondary refining process. Mixing characteristics in the ladle is evaluated by pulse tracer addition using conductivity-meters located at the down leg as well as at several locations in the ladle. The influence of gas injection through nozzles in the upleg with simultaneous bottom injection of gas as well as nozzle blockage on the circulation rates were investigated. Also simulation experiments of kinetics of decarburization were carried out using C02 adsorption-desorption process in sodium hydroxide solution as circulating fluid and the effect of, bottom gas flow rate in this case was also evaluated. The results were carried over to prototype and to optimize the process.

Jan 1, 2003

By Fjeldstad Karin Jusnes

Two quartz types used in the silicon and ferrosilicon industry were heated to temperatures of 1600 and 1700 °C. The parameters varied were the temperature and the holding time at maximum temperature. The amount of quartz, cristobalite and intermediate amorphous phase were measured using XRD and the internal standard method. Type P showed a much larger ability to transform to cristobalite at lower temperatures than type A. Type P had a larger amount of alkali and alkaline earth impurities. This could have enhanced the transformation to cristobalite. For quartz type A the amount of cristobalite was larger at 1600 °C than 1700 °C. This can also be seen for some of the samples of type P at shorter holding times.

By Bhagyadhar Bhoi, Chitta Ranjan Mishra, Hara Prasanna Mishra

"In the Sukinda Valley of Orissa, India, the total quantity of nickel ore reserves comprising of both lateritic and chromite over burden(COB) have been estimated at around 231 million tonnes containing 0.3 to 0.9% Ni. While mining of one tonne of Chromite ore, around 6-7 tonnes of chromite over burden are removed. These overburden materials are disposed as waste materials, which causes lot of environmental hazards and ecological imbalance. India imports a large amount of nickel and ferro-nickel to meet its growing demands in various sectors. For import substitutions, efforts have been made to produced ferro-nickel from the lean deposits of nickel bearing lateritic ores/ chromite over burden materials by reduction roasting followed by magnetic separation and then the nickel rich magnetic fraction is smelted to produce ferro-nickel. It has been possible to produce ferro-nickel of grade varying from 4-25% nickel.IntroductionDuring mining of chromite ore, large quantities of overburden materials are being generated. The materials amount to approximately 10 million tones per year contain around 0.3-0.9% Ni, 0.02-0.06% Co, 20-50% Fe and 4-9% Cr2O3 depending upon the location and the depth of the mine. These materials presently do not find any application for the extraction of nickel due to lack of a suitable technology. The materials are also unsuitable for ferro-nickel making because of their very high iron to nickel ratio. The country is seriously looking for a suitable technology to utilize these resources as its entire domestic requirements of nickel is met though imports. In this connection, a systematic approach has been made at the Institute of Minerals and Materials Technology, Bhubaneswar to develop a process for ferro-nickel making from this indigenous resource."

Jan 1, 2011

By Zhao wen Wang, Ramana G. Reddy, Min Li

"The electroreduction of Co(II) in l-butyl-3-methylimidazolium tetrafluoroborate (BMlMBF4) ionic liquid was investigated by cyclic volatrnmetry at 353 K. The results show that the reaction of Co(II) to Co is irreversible in one step with two electrons transferred. The diffusion coefficient of Co(II) was estimated to be 7.6 x 10-8 cm2 s·1 at 353 K. Then the electrodeposition of cobalt was studied at different cathodic potentials (-0.80 to -0.95 V) and different temperatures (333 to 363 K) in BMIMBF 4 containing 0.20 mol L-1 Co(BF4)z. The deposits were characterized using scanning electron microscope (SEM), energy-dispersive spectroscopy (EDS), and X-ray diffraction (XRD). SEM images show that a uniform, dense, and compact deposit was obtained at -0.80 V and 333 K. The deposits were identified as high-purity metallic Co for all experiments by EDS and XRD.IntroductionCobalt is known as a hard magnetic material and cobalt alloys have been shown to have excellent magnetic properties with adequate mechanical durability and corrosion resistance, which are needed for high performance magnetic recording applications [1-4]. The electrodeposition of Co alloy in the aqueous solution is generally difficult because of the narrow electrochemical potential window of water, which leads to the low current efficiency and worse quality of deposits due to the hydrogen embrittlement. Thus, aprotic ionic liquids (ILs) are expected to be the ideal alternative media for electrodeposition of cobalt or its alloy since ILs usually provide a wide working potential windows, negligible vapor pressure, and acceptable conductivity for electrolysis without the occurring of hydrogen evolution [5, 6]."

Jan 1, 2014

By J. T. I. Poijärvi

The smelter off-gas cleaning and the weak acid treatment at Outokumpu Harjavalta Metals Oy are presented and described in this paper. The smelter consists of the copper and nickel smelters and the acid plant of three separate acid plants two of which are double contact and one single plant and of one liquid sulphur dioxide plant. The preliminary cooling and flue dust separation of the smelter off....,gases from the copper ?and nickel flash smelting furnaces and converters? in the waste heat boilers and in the hot electrostatic precipitators are described. The final cooling and cleaning of the gases in the scrubbers at the sulphuric acid plant and the treatment of the weak acid in the vacuum and in the submerged combustion evaporators for the removal of impurities are presented as well as the treatment of the condensates from the evaporators. The attention is paid to the generation of sulphur trioxide in the smelter off-gas.and to the treatment of that in the weak acid bleed-off and to the utilization of the treated acid.

Jan 1, 1992

By Maria K. Kojo

The interaction between various slags and a nickel concentrate containing pyrite, pentlandite, and violarite were investigated by submerging concentrate pellets in molten slags. The slags were contained in MgO-A12O3 spinel crucibles. The slag oxidizes the iron sulfides in the concentrate, resulting in a nickel matte. The amount of S02 gas formed during reaction was measured to determine the oxidation reactivity of the slags. The experimental variables included temperature, the ferric/ferrous ratio of slag, and other slag properties such as the FeO/SiO2 ratio and the MgO and NiO contents. The reactivity of the slag depended in a complex manner on its oxidizing power, viscosity, and interfacial tension. The slag composition for the greatest reactivity was determined to be Fe3+/Fe2+ = 0.3, Fe/SiO2 = 1.3, and % MgO = 2. This slag, however, caused substantial foaming. Increasing the MgO content to 10% or replacing it by 5% MgO + 8% NiO eliminated at a slight decrease in reactivity. The implications of the findings from this work in the bath smelting of nickel sulfide concentrates are discussed.

Jan 1, 1995

By J. T. I. Poijärvi

The smelter off-gas cleaning and the weak acid treatment at Outokumpu Harjavalta Metals Oy are presented and described in this paper. The smelter consists of the copper and nickel smelters and the acid plant of three separate acid plants two of which are double contact and one single plant and of one liquid sulphur dioxide plant. The preliminary cooling and flue dust separation of the smelter off-gases from the copper and nickel flash smelting furnaces and converters in the waste heat boilers and in the hot electrostatic precipitators are described. The final cooling and cleaning of the gases in the scrubbers at the sulphuric acid plant and the treatment of the weak acid in the vacuum and in the submerged combustion evaporators for the removal of impurities are pre¬sented as well as the treatment of the condensates from the evaporators. The attention is paid to the generation of sulphur trioxide in the smelter off-gas and to the treatment of that in the weak acid bleed-off and to the utilization of the treated acid.

Jan 1, 1992

By Juan Hernández Ávila

This work studies the Molybdenum effect on the microestructure, mechanical properties of an as-cast ductile iron. For this study five ductile irons with different amounts of Molybdenum each were made in an induction furnace. In this material nodule count and nodularity is affected by the Molybdenum additions; The iron´s matrix, nodules and the phase were analyzed using scanning electron microscopy detecting Molybdenum only in the matrix. Mechanical properties such as hardness, microhardness, tensile strength and yield strength show increments as the Molybdenum amount is increased. In the same way, ferrite and pearlite phases display a variation in their percentage as the contents of the alloy element increase. This element has a marked influence on the pearlite interlaminar spacing. From the obtained results we conclude that Molybdenum in these quantities dissolves in solid ferrite solution during the solidification process, improving the material´s mechanical properties.

Jan 1, 2009

Primary sulphidic gold ores in the Archean provinces of Western Australia can be broadly sub-divided into pyritic, pyrite-telluride, arsenical and antimonial types. Pyritic ores contain only native gold, and are essentially not refractory. Arsenical ores almost always carry some invisible gold, and may vary from mildly to highly refractory. Pyrite-telluride ores contain gold-bearing tellurides, and are refractory to varying degrees. Antimonial ores usually contain aurostibite, and may be very difficult to process. A classification scheme for metallurgical processing, based on mineralogy, is proposed for the ores, and implications for processing are discussed.

Jan 1, 1995

By D. J. Adams

Cyanide heap leaching is the predominant technology used in processing low-grade gold ores. During closure ora heap leach operation, residual cyanide must be removed from the process and waste solutions, as well as the heap. Biological cyanide oxidation is a proven, economical technology for destroying cyanide in process and waste waters and spent heaps; The use of biological cyanide degradation eliminates the need for toxic or corrosive chemical oxidizers and has- been implemented at full scale at treatment costs usually <$0.50/1,000 gal. The Applied Biosciences biological cyanide destruction (BCND?) process has been demonstrated to effectively treat cyanide, concentrations up to 350 mg/L. Treated process solutions and wastewaters also contained other contaminants such as arsenic, copper, iron, silver. selenium, mercury, nitrate and zinc, much of which was removed in the cyanide degradation process. Under optimal conditions, microorganisms can rapidly oxidize free cyanide in some process solutions from over 250 mg/L down to 0.1 mg/L in 4 to 5 hr. Cyanide is degraded to ammonia and carbon dioxide, with 50%ofthe cyanide carbon liberated as C02. In general, carbon tank based bioreactors degrade cyanide at significantly higher rates than process or wastewater pond configured treatments, which usually degrade cyanide-more rapidly than in heap treatments. Investigation of cell-free enzyme preparations as an alternative to live microbial cyanide degradation shows promise. Advantages of enzymes over live microbes for cyanide degradation include: (I) the ability to tolerate and degrade higher cyanide concentrations (> I ;000 mg/L), (2) nutrients to support live microbial cells are not required, (3) the effects of other toxic contaminants, such as metals, found in mining waters-are eliminated and (4) the potential for greatly increased kinetics.

Jan 1, 1998

By Konstantina Chalastara

Mixed phase titanium dioxide (TiO2) nanoparticles synthesized through hydrolysis of TiCl4 solution at different conditions, namely concentration, pH, and residence time are characterized and evaluated as photocatalysts. The process is operated in a continuous stirred-tank reactor, CSTR giving blends of anatase, brookite, and rutile nanoparticles that were further evaluated to find the optimum mixture for a photocatalytic sorption material. The titania nanoparticles are first characterized in terms of photocatalytic activity under UV light illumination using an organic model compound (methyl orange) and after that are tested for removal of toxic selenate and selenite species from simulated effluent waters.

By Tapio Ahokainen, Asmo Vartiainen

"Outotec's portfolio contains a wide variety of smelting solutions for non-ferrous metals. Some of these include flash smelting for primary copper and nickel, flash converting for copper, Ausmelt technology for primary and secondary copper, nickel, tin, lead, and zinc residues and waste, Kaldo technology for secondary copper, lead, and precious metals recovery. Outotec also offers slag cleaning technologies and much more.Company provides complete process solutions tailored to each customer's individual needs. Decades of experience have resulted in extensive metallurgical know-how that ensures the most profitable process choice and optimal performance. Outotec's life cycle technology partnership with their customers spans from the early stages of process solution design through the supply and commissioning of the entire process chain. They include integrated process control and holistic service and support concepts. Continuous research and development ensures that the customer is provided with the latest advancements in process and equipment solutions.IntroductionOutotec develops and provides technology solutions for the sustainable use of the Earth's natural resources. Solutions are ranging from various processes and special equipment needed for metallurgical extraction and mineral processing of ores to the production of refined metals and minerals. The processes include not only the grinding and physical separation of ores but also the smelting and leaching of base metals and precious metals. The company provides engineering services for whole projects as well as life cycle services on the equipment and products that they supply."

Jan 1, 2012

By N. Kanari

The thermal decomposition studies of two zinc basic carbonate samples were carried out up to 400 "C by thermogravimetric analysis, boat experiments and differential scanning calorimetry measurements &apos;DSC&apos;. The initial samples and the solid decomposition products were analyzed by scanning electron microscopy, x-ray diffraction and laser particle size analyzer. The thermal decomposition of both samples started at about 150 "C and the rate of decomposition became significant at temperatures higher than 200 "C. The apparent activation energies &apos;Ea&apos; in the temperature range 150-240 "C for sample decomposition were between 132 and 153 kJ1mole depending on the sample origin. The XRD analyses of the intermediately decomposed samples and the DSC results up to 400 "C suggest that the decomposition reaction probably occur in a single step.

Jan 1, 2002