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By R. R. Odle

A laboratory and pilot-scale investigation of direct smelting of copper concentrates was conducted to determine the effect of concentrate analysis and the degree of roasting on the yield and quality of copper produced in a subsequent smelting step. A stoichiometric :mOdel of direct smelting is presented which predicts the? quantity of copper; slag, and white metal' prOduced'and the distribution of copper in these phases as a function? of the concentrate '(calcine) analysis.

Jan 1, 1983

By Feng Liu

A thermal upgrading process by which nickel value can be concentrated in a ferronickel alloy is a possible alternative to treat Sudbury pyrrhotite (Po) tailings with nickel content of 0.5–1.5 wt%. The basis of this process is precipitation of Ni from Po at high temperature once Fe/S ratio in the iron-deficient Po is shifted towards stoichiometric or near stoichiometric FeS (troilite) either by the addition of iron and/or the removal of sulfur. For the iron addition route, the reaction between elemental iron and nickeliferous pyrrhotite to produce ferronickel alloy and Ni-depleted iron sulfide phase plays a critical rule. In this paper, the formation mechanism of ferronickel alloy was investigated using the diffusion couple technique to better understand the nickel diffusion behavior in the iron and sulfide phases.

By Yuanbo Zhang

Zinc leach residues produced by hydrometallurgical zinc plants contain many valuable elements (zinc, iron, lead, gallium, indium silver, etc), while they have not been utilized effectively hitherto. In this paper, a new process of flotation-reduction roasting-magnetic separation to recover these valuable elements from zinc leach residues is developed on a basis of mineralogy investigations of them. The results show that silver concentrate with grade of 4321.6 g/t and recovery of 80.69% have been obtained, using 1750 g/t Na2S as conditioner, 750 g/t ammonium dibutyl dithiophosphate and SN-9 (assistant collector) as combined collector and 100 g/t terpenic oil as frother, if zinc leach residues with 523 g/t silver are floated at pH = 5.0. When the flotation tailings are subjected to reduction roasting at 1100? for 2 h, the volatilizations of zinc, lead and indium are over 96%. After roasted products are treated by wet-grinding and magnetic separation, the grade of gallium and gallium in the concentrates achieved respectively reaches 1805 g/t and 1536g/t, and the recovery of them is high to 94.67% and 93.20%, respectively.

Jan 1, 2006

By M. T. Thomas

Sufficient development of the X-Ray Photoelectron Spectroscopy (XPS), the Auger Electron Spectroscopy (AES), and the Secondary Ion Mass pectroscopy (SIMS) has made these instruments ideal for solving problems related to mineral processing -particularly gold ore processing. XPS can determine both the surface composition and chemistry of ores and tailings, and the various phases within either of them. AES can also determine surface composition with the further advantage of having greater spatial resolution so the surface chemistry associated with specific minerals in the ore can be identified. This identification helps to clarify why some minerals pass through a chemical process unaffected, while others can be successfully treated. SIMS has an elemental sensitivity from one to four orders of magnitude greater than XPS or AES which makes it useful for detecting the presence of some elements in very low concentration (parts per million).

Jan 1, 1981

By Gabriella Tranell

In the manganese ferroalloys industry, there is increasing focus on the performance of different carbonaceous materials within the smelting processes. With a developing scarcity of traditional raw materials, new carbon sources are being identified for potential use in the processes. For this purpose, it is important to be able to predict the suitability of different materials in the process. Hence, the effects of both the physical and chemical properties of the carbon material on the reduction kinetics of manganese and silicon from slag to metal, have been investigated using an advanced sessile drop technique. Using this technique, the reaction patterns of SiO2-MnO containing slag droplets in contact with various solid carbon materials (graphites with different properties as well as cokes and charcoals) at 1400 to 1600\\176;C were studied in-situ. In addition, slag and metal reaction products from kinetic experimental series were analysed. From these results, differences in reactivity between various carbon materials and slags were demonstrated and explained. Mechanisms for both manganese and silicon reduction were proposed.

Jan 1, 2006

By Lassi Klemettinen

For better understanding and maximal value utilization of the WEEE smelting process, the behavior and distribution of different trace elements must be known. In this study, the behavior of nickel as a trace element was studied in an equilibrium system with metallic copper—spinel saturated iron silicate slag (with 3 wt-% K2O)—iron aluminous spinel—gas. The experiments were conducted in alumina crucibles at 1300 °C, in oxygen pressure range of 10−10–10−5 atm. A time series of 15–60 min experiments was also conducted for investigating the formation rate of the primary spinel phase in the system. The results show that the distribution coefficient of nickel between metallic copper and liquid slag changes from approximately 70 to 0.4 along the increasing oxygen pressure range. In addition, a significant part of the nickel deports into the spinel phase. The spinel formation was investigated based on composition analysis results and visual observations from SEM-images.

By Teixeira

An experimental investigation on the kinetics of oxidation of As(III) with H202 in synthetic effluent solutions followed by precipitation of Fe/As (V) compounds was carried out. The variables investigated were: As concentration (200 -3000 mg/l) , oxidation pH (2.0 -11.0), oxidation temperature (25 -800C) , H202 stoichiometric excess (50% -100%), precipitation pH (5.0 -7.0), precipitation agent (Fe2+ -Fe3+). Fixed conditions were, Fe/As molar ratio (6:1) and stirring speed (560 rpm). The results were empirically modelled. The precipitates obtained were amorphous. The precipitates were checked upon their environmental stability according to the United States Environmental Protection Agency (U.S.E.P.A.) Toxicity Test, and were considered to be adequate for deposition in impermeable waste dumps. The combined Fe/H202 detoxification process, in selected conditions, was able to reduce the As contents of effluents containing 1600 mg/l As to 0.1 mg/l, in about 2 1/2 hours of total processing time.

Jan 1, 1990

By Onder Guney, Erdem Demirkesenm

"In this study, the crystallization behavior and thermal expansion coefficient of a lithium disilicate (LS2) based glass-ceramic derived from SiO2-Li02-AhO3-K2O-ZrO2 system was investigated by using x-ray diffraction (XRD), high temperature x-ray diffraction (HTXRD), differential thermal analysis (DTA) and dilatometer techniques. Analytical reagent grade chemicals were chosen as raw materials for preparing glass batches. Nucleation and crystal growth heat treatments were planned according to DTA results. The amounts of the amorphous and crystalline phases developed during the heat treatments were determined by quantitative XRD. XRD results of crystallized samples showed simultaneous formation of lithium silicate (LS) and quartz in the early stage of the crystallization followed by formation of lithium disilicate (LS2) at higher temperatures. The thermal expansion coefficients of glassceramics were also measured depending on the applied heat treatments.IntroductionSignificant developments occurred in all ceramic materials provide the fabrication of high quality dental implants [1]. Glass ceramic based dental restorations like dental inlays, crowns, bridges and veneers are becoming increasingly popular with their reliable and durable performance [2,3]. In addition to their advanced functional properties, glass ceramic implants especially lithium disilicate glass ceramics also face the esthetics expectations of patients and dentists and in this way they are starting to take the place of metal based restorations today [1,3,4,5]. Lithium disilicate glass-ceramics derived from multicomponent glass systems have some superior mechanical and optical properties comparable to natural teeth [ 6]. In restorative dentistry, mechanical characteristics of biomaterials play very crucial role in order to resist the masticatory forces occurred during biting and chewing [7] According to three point bending test results of Roland, flexural strength of the lithium disilicate glass-ceramics were 400±40 MPa and their fracture toughness (K1c) are approximately 3,3 MPa m112 [2,6]. In addition to high mechanical strength, aesthetic appearance is another important prerequisite as material for dental restorative applications. Translucency and light transmission of the LS2 glass ceramics mimic enamel. Moreover, opacity of the material can also be adjusted depending on the restoration types [2,6, 7]. These superior properties of the LS2 glass ceramics are directly related with chemical composition of the base glasses and controlled crystallization heat treatments [ 4, 7]. The aim of the present work is to determine the effect of heat treatment schedules on the crystallization behavior and thermal expansion of the LS2 glass-ceramics."

Jan 1, 2011

By Tiebao Yang

In high pressure die casting processes, a die plays a critical role in removing heat from the molten metal during the cavity filling and solidification stages. Proper control of die temperature is essential for producing superior quality components and yielding high production rates. This paper proposes a local temperature control scheme for die thermal management based on a computerized intelligent real-time monitoring and control system (IRMCS). In this scheme, cooling water lines are controlled by a pump and solenoid valves. A controller is designed according to the law of die temperature fluctuations. The results obtained from the experiments carried out on a laboratory die casting process simulator indicate that the controller can limit the local die insert temperatures in a given band. Hence, the desired thermal pattern of the die insert becomes achievable.

Jan 1, 2006

By Vinay Kumar

The disposal of large quantities of electronic scraps generated world wide is causing not only environmental problem but also loss of resources. Therefore, R & D efforts have been made to develop a suitable process for extraction and separation of metals viz. copper, zinc, cadmium and nickel expected from the leaching of e-scraps using solvent extraction process. Different process parameters viz. pH, aqueous to organic ratio, kinetics of extraction, extraction isotherm to establish stage requirement for extraction in continuous mode etc have been studied to optimise the condition for the separation of metals. The studies showed the selective extraction of copper after iron precipitation from the sulfuric acid leach solution of e- wastes containing ~1.0 g/L Cu and minor impurities with 2-hydroxy-5- nonylacetophenoneoxime (LIX 84) above pH 2.0 in single stage. A scheme for separation of cadmium, zinc and nickel has been proposed using di(2-ethylhexyl) phosphoric acid (D2EHPA) under controlled pH of the aqueous solution. The order of extraction was found to be Zn> Cd> Ni.

Jan 1, 2009

By M. W. Kennedy

Prediction of the thermal duties of copper coolers in freeze lined furnaces is challenging. Where copper coolers are immersed in liquid slag the heat transfer is often defined by a natural convection cell immediately adjacent to the wall, in the absence of other factors producing forced convection. Slag coolers are typically not fully immersed, slag temperature, liquidus and superheat can vary, and bath levels may change significantly with batch tapping, leading to substantial variations in radiation heat fluxes. Radiation heat transfer is discussed with reference to the non-obvious impact of slag liquidus on radiation losses in the exposed cooler sections. Reference is made to literature and the results of analytical and FEM models.

By Ángel Ruiz-Sánchez

Ethylene glycol additions to aqueous acid solutions for leaching copper sulfides increase both copper and iron extractions compared to a conventional sulfuric acid leach with hydrogen peroxide (H2O2). The role of ethylene glycol is to prevent peroxide destruction, which normally occurs in solutions that contain both cupric and ferric ions. However, despite this improvement, ethylene glycol and sulfuric acid concentrations must be high (3.5 M and 0.7 M, respectively) to obtain satisfactory conversion levels at room temperature. In the present investigation, EDTA was used as an additive to complex the cupric and ferrous ions, lowering the requirements of ethylene glycol and H2SO4 to 0.11 M and 0.007 M, respectively, while minimizing oxidant decomposition. The experimental results for a mainly chalcopyrite, copper concentrate showed complete copper extraction in 24 h at room temperature, with the stoichiometric quantity of EDTA for the copper and iron dissolved. Tests using seawater were equally as successful.

By Lloyd R. Nelson

The feasibility of producing low carbon (LC) ferromanganese (FeMn) by lime-'ore' melt refining of high-grade ferromanganese silicon (FeMnSi) was investigated. Thermodynamic simulations demonstrated significant benefits in moving from a single-stage ladle operation to a two-stage counter-current reladling operation (to emulate the commercial Penin Process). The theoretical alloy silicon content was predicted to be refined from 1.57 to 0.005 per cent silicon, at a 6.2 per cent higher manganese yield (yield predicted to increase from 82.3 to 88.5 per cent). Extension of this counter-current refining principle, to a multistage Counter-Current Reaction Launder (CCRL) was investigated using the Slag Metal And Gas Klnetics (SMAK) software to model the mass transfer kinetics of the multicomponent coupled reaction system. Simulation results suggested that commercial production of 50 000 tonnes per annum (tpa) of refined LC FeMn, containing less than 0.5 per cent silicon, at manganese yields of up to 90 per cent, should be feasible in a compact CCRL (7 m long by 0.7 m wide).

Jan 1, 1994

By R. Elliott, H. Bayati

"Effect of time and temperature on microstructure and mechanical properties of an austempered ductile iron, ADI, of composition 3.6%C, 2.6%Si, 0.4%Cu, 0.2%Mn are reported. Xray analysis and. microstructural observations indicate that lowering the working temperature, aging temperature, increases the lifetime of ADI significantly. Results show· that lowering the aging temperature increases the strength and reduces the ductility of ADI. DSC traces for ADI austempered at 340°C are presented. Comparison of the DSC analysis and kinetic measurements demonstrates that the DSC traces can be· used to predict the life time of ADI successfully.IntroductionAustempered ductile iron, ADI, is one of the most significant developments in cast iron technology over the past two decades. Outstanding properties of high yield, ultimate strength, ductility, fatigue and wear· resistance make ADI suitable for a range of applications including gears, connecting rods, crankshafts and agriculture machine components. The austempering reaction in cast iron occurs in two stages, Fig. I, in contrast to the single stage reaction in steel. In stage I the relatively low carbon austenite produced during austenitising transforms into ferritic plates and high carbon austenite, a metastable structure called·ausferrite. The high carbon ailstenite and supersaturated ferrite produced in stage I decompose into ferrite and carbide in stage II: to form a structure similar to the bainitic structure in steel. This behaviour exposes a well-defined processing window, t1 - t2, over which the maximum amount of ausferrite is produced, Figure 1. Whereas the bainitic structure determines the properties of austempered steel, ADI properties are mainly affected by volume fraction of retained austenite (VRA), austenite carbon content (ACC), unreacted or martensite volume fraction (UA V), compositiori and amount of carbides, and morphology of ferritic plates[l,2]. Due to the detrimental .effect of martensite and carbides on properties of ADI, an ideal structure of ADI consists only of ausferrite [l,2]. Thus, it is common to determine the processing window for each austempering treatment in order to identify the optimized austempering time. Decomposition of austenite (stage II) signals the end of the life time for an ADI component, therefore, the aging behaviour of ADI at different working conditions can be studied by determining the t2."

Jan 1, 2000

By E. O. Ávila-Davila, F. R. Barrientos-Hernández, I. A. Lira -Hernández, Miguel Pérez-Labra, M. Reyes-Pérez, J. Antonio Romero-Serrano

Slag from smelting reduction processes were characterized by chemical analysis, XRD, SEM-EDS and XRF. The results revealed Ag concentrations of 362 g/t of slag, the slag mineralogical characterization by XRD and SEM-EDS showed mineralogical species oxidized complex containing Pb, Zn, Ca, Si, Fe, As, S in its structure, silver was found in globules associated lead in the slag and the furutobeite specie. The leaching study was conducted to evaluate process variables such as NaCN concentration: from 7.8x10-3M - 1.26x10-1M, temperature: 25-50°C, particle size: +140 mesh to -400 mesh, stirring speed of 750 rpm - 900 rpm. All studies were performed with a NaOH concentration of 0.2 M. The optimal values of silver recovery encountered in conditions of 7.8x10-3M NaCN, agitation rate of 750 rpm, temperature of 35°C and with a treatment time of 240 min. We also observed that a particle size -400 mesh will have optimum recoveries compared to +140 mesh, +200, +270 and +325.

Jan 1, 2015

By Batric Pesic

Solvent extraction of nickel and cobalt from the real leach solutions was studied by using a novel extraction system. The extraction system was a mixture of 2,6-bis-[5-n-nonylpyrazol-3¬y]] pyridine (BNPP) and dinonylnaphthalene sulfonic acid (DNSSA). The BNPP represents a novel molecule, which was designed and synthesized in our laboratory. Real solutions for the study were prepared by leaching of two different cobalt-nickel bearing concentrates, cobaltite [CoAsS] concentrate from Blackbird Mine, Idaho, and siegenite [(Ni,Co)3S4] concentrate from Missouri Lead-Belt. The major strength of the system was the selectivity of extraction toward nickel and cobalt from iron containing solutions. Other metals such as Mn, Mg, Ca, Al and As were not extracted. Due to the irreversibility of copper extraction, its removal from solution was required prior to the extraction of nickel and cobalt. Zinc was not as strongly extracted (i.e. its stripping was readily achieved) as was copper . Flowsheets for the recovery of nickel and cobalt were also developed.

Jan 1, 1997

By Amy Anderson

The Silica (SME) Technology has been utilized on three separate projects focusing upon the stabilization of mercury-contaminated materials: at the Mother Lode Mine in Oregon, the Sulfur Bank Mercury Mine in California and at a former chloralkali plant in British Columbia. Each of the projects relied primarily on the results collected via EPA Method 1311 TCLP, with additional tests such as SPLP, humidity cell tests and other supporting tests employed as well. Both technical and economic performance of the silica-based technology was evaluated as well as that of competing technologies in some cases. Results established that in each of the three projects an SME chemical dosage rate of 3% chemical by weight of soil/sludge was the optimal ratio required to achieve project treatment objectives, TCLP test results exhibited a reduction in the leachable mercury from the treated materials ranging between 75% and 99% as compared to untreated material, satisfying the technical objectives for each project, Project costs ranged from $l5.00 - $18.26 per metric ton.

Jan 1, 2003

By A. F. Kaczmarek

Cerro Negro is an undeveloped ore body located at the Cerro Verde mine near Arequipa, Peru. The mineable reserve contains 70 Mt of oxide ore grading 0.532% copper. Mineralization is hosted in three distinct rock types: tourmaline breccia, crackle breccia and granodiorite. Rock type effects copper recovery and acid consumption. The paper describes Cyprus' testwork philosophy and the resulting four-phase metallurgical program used to define the commercial leaching parameters. Copper recovery and acid consumption were monitored as functions of crush size, heap height, irrigation rate and acidulation conditions. Single lift, on-off and permanent multi-lift heaps were considered. Leach cycle times were based on incremental copper extraction and acid consumption rates, with added constraints imposed by operational requirements. The optimum leach system involves an on-off pad using tertiary crushed ore acidulated with 20 kg/t acid and stacked to a height of 6.5 m. The active leach cycle is 82 days at an irrigation rate of 0.26 l/min/m2. Under these conditions copper recovery is expected to average 81% over the life of the mine.

Jan 1, 1999

By Kazuya Koyama

We are studying the hydrometallurgical recycling process of indium from an Indium-Tin-Oxide(ITO) target. For this process, it is necessary to remove Sn(IV) ions from the aqueous hydrochloric acid solutions containing In(III). In this study, the removal of Sn(IV) ions by a potentiostatic electrolysis method was examined. The polarization measurements and potentiostatic electrolyses were carried out under a nitrogen atmosphere. In the Sn(IV) solution, current begins to rise at the cathode potential of -0.26 V vs. SHE, and increases with a reduction in the cathode potential. In the In(III) solution, current begins to rise at a cathode potential of -0.43 V vs. SHE. Metallic tin was electrodeposited without indium electrodeposition at the cathode potentials of -0.30 and -0.40V vs. SHE. More than 98% of the Sn(IV) was removed at the cathode potential of -0.40 V after the electrolysis for 3hrs. Both tin and indium were electrodeposited at the cathode potential of -0.50V vs. SHE.

Jan 1, 2006

By B. B. Agrawal

Iron ore fines is an area of concern in India. A possible avenue is to use these fines for sponge ironmaking. Work has been carried out to pelletize these fines with coal and a suitable binder, and cure them in ambient atmosphere to retain in-situ reductant. Pellets were characterized for physical strength and metallisation. Critical factors were granulometry was percentage of coal & binder. In laboratory tests, pellets got metallized faster compared to lump ore. Large-scale trials were conducted in a 12-meter long rotary kiln plant. For 90% metallization, required residence time was only 60 minutes against 240 minutes for lump ore. Coal requirement also decreased. Investigations established the fast reduction nature of pellets. This is due to reduction-reactions occurring simultaneously at many sited within the composite pellets, in addition to the diffusion of reducing gases from the surface of the pellets to its core. The developed process is a value addition in the conventional pelletmaking and is environment-friendly also.

Jan 1, 2006