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By Jagdish C. Agarwal

Although copper ranks very low in the order of abundance of elements in the crust of the earth, it has been one of the first metals utilized by mar, at his emergence from the Stone Age, about 10,000 years ago. Use of copper for weapons, tools, utensils and ornaments dates back to the twilight of history, 6,000-5,000 B.C. Native copper outcrops and the malleability of the metal explain its very early use by the cave-dwellers. The working, melting and extraction of copper from its minerals are among the oldest metallurgical achievements of the human race. The oldest complete smelting installations for the extraction of copper from its minerals, dated about the fourth millenium B.C., were recently discovered in the Timna Valley, Wadi Arabah, Israel. (1) The history of the developments of the extractive metallurgy of copper has been adequately reviewed recently. (2,3) The center of copper production migrated from the Eastern Mediterranean to Northern Europe (Mansfeld, Germany, Swansea, Wales) towards the end of the Middle Ages (1500 A.D.). The production of the metal was boosted tremendously in North America since the end of the nineteenth century (Fig. 1).

Jan 1, 1976

By Patrick R. Taylor

Sub-micron sized boron carbide powders have been synthesized in a non-transferred arc thermal plasma reactor. Precursors for this synthesis are boric acid or boron oxide powders and methane. The powders produced were characterized in terms of size, shape and purity. Methods to increase the purity of the product were evaluated and included hot water leaching to remove unreacted oxides and controlled temperature, air roasting to remove excess carbon. Theoretical results are also presented on the thermodynamics and mechanisms of the synthesis reactions.

Jan 1, 1994

By S. M. I Kytö, J .. K. Mäkinen, K. Saarhelo

"At the Outokumpu Oy Harjavalta Copper Smelter the control philosophy of the flash smelting process has been changed from the slow feed-back control to feed-forward control. This is important as the fluctuations in the flash smelting furnace matte grade and slag temperature are desired to be minimized.The system is based on a specially designed automatic sampling device and the Outokumpu Courier 20 on-stream X-ray fluorescence analyzer. A microcomputer-based Analyzer Operator Station (AOP) controls the system and calculates the process parameters for the furnace from the analyzed chemical composition and other existing data.A considerable reduction in the deviation of the matte grade and slag temperature has been gained. This has resulted in conservation of energy and refractories, lower copper losses and higher through-put in the flash smelting furnace and converters.1.0 IntroductionThe flash smelting technology for copper concentrates was developed at the Outokumpu Oy Harjavalta Smelter soon after the World War II. The incentive for this development was shortness and high price of any form of energy. The fact that smelting can be carried out autogenously, without external energy by utilizing the latent heat of sulfide combustion was known decades before, but Outokumpu Oy was the first company to take the advantage of this knowledge in practical operation. A further advantage of this technology was that the SO2 containing gases suited well for sulfuric acid production, thus minimizing the detrimental effects on the environment (1).The very heart of the flash smelting process is the reaction shaft of the flash smelting furnace (see Appendix I). Heating up of the dried feed mixture, dissociation of several compounds, ignition and oxidation of the feed take place very intensively in the reaction shaft during 2 - 3 seconds, which the fine grained particles reside in the reaction shaft. A very accurate control of the amounts of the feed materials as well as of oxidizing gases, fuel, etc. is of primary importance."

Jan 1, 1989

By Timothy W. Ellis

This paper presents the basic theory of operation, physical chemistry and phase equilibria which allow the development of liquid-liquid extraction circuits based on metallic solvents. The incorporation of reduction and reduction/diffusion processes into the process 'scheme is discussed and a detailed description of ,several liquid-liquid extraction schemes are developed. A synopsis of experimental results obtained using this: method to separate rare earth and other metal based materials will be given.

Jan 1, 1996

By Patrick R. Taylor

Ilmenite concentrate and methane are fed to a non-transferred arc thermal plasma reactor to produce a powder that is primarily TiC and Fe. This material has promising characteristics for powder metallurgy applications. Free energy minimization plots were used to predict the feasibility of the reaction. An estimate of the optimum molar ratio between the ilmenite concentrate and methane was made based on the mineral composition. Argon-helium mixtures were used as plasma gases. The effects of power input level, carrier gas flow rate, powder feeding rate, and methane-ilmenite molar ratio were studied and the behavior of the system characterized. Two different powder injection angles were tried. A mathematical model to describe the temperature profiles in the reactor was formulated and solved. The product has been characterized by x-ray diffraction and atomic absorption. A conversion of 97 % of Ti to TiC was achieved. It was found that minor amounts of titanium oxides, iron carbide and free carbon are also present. TEM and SEM were used to study the morphology.

Jan 1, 1996

By Basant L. Tiwari

An electrolytic process, based on a three-layer concentration cell, to extract magnesium from commercial aluminum alloy scrap has been examined. The process was repeatedly tested at 1025 K with two cells of d1fferent sizes, 0.6 kg and 5 kg feed aluminum, to have a better understanding of the opera ting parameters and evaluate the scale-up potential. In both cells, the magnesium content of the scrap was selectively reduced ?from 1. 1 to less than 0.1 wt.% at anodic current dens-Hy as high as 1. 1 A/cm2 with current efficiency exceeding 85%. Magnesium was recovered in the form of salt coated globules. Comparison of performances for the two cells suggests that the process can be scaled up. With further development, this process could become a viable alternative for demagging secondary aluminum.

Jan 1, 1985

The effect of change in slag composition upon metal losses to the slag and the relationship between slag composition and slag matte separation was investigated at 1400°C. The synthetic slags containing CaO, MgO, SiO2,, A1,0, and FeO were similar to those employed in the electric furnace smelting of sulphide Cu-Ni concentrates containing PGM (Precious Group Metals) from the Merensky Reef of South Africa. The matte with a grade of 9.3% Cu and 16.0% Ni was a typical electric furnace product. The results indicated that the Cu and Ni solubility in the slag increases with the increase of the basicity ratio and CaO and MgO contents of the slag. At constant CaO/MgO ratios the rise in basicity decreases the metal losses. When FeO and SiO2 contents of the slag are kept constant, the substitution of MgO with CaO decreases the metal losses. The relationship between slag composition and matte-slag separation was found to depend primarily on the basicity ratio and the FeO content of the slag. The net effect comes from a strong interaction of the two in such a way that increasing basicity and decreasing FeO contents deteriorate the clean separation of the two phases.

Jan 1, 1994

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 H. Fukuyama

The wetting behavior of single crystalline MgO by fayalite-type slag melts has been studied by the sessile drop technique incorporated with high temperature X-ray radiography. The experiments were performed under oxygen partial pressures of 10-6 and 10-4 Pa at 1473 K. Mass ratios of iron to silica, Fe/Si~, in the slag employed were 1.4 and 2.0. To investigate the interfacial reaction, experiments using high density MgO crucibles were also conducted. The reactions at the interfaces were examined by Electron Probe Microanalysis. The contact angles between the slag melts and the MgO substrates were found to be relatively low, ranging from 30 to 10 degrees. The surface tension of the slag was 0.4 N/m for a slag of Fe/Si02 = 2.0. Two phases, magnesiowiistite and olivine, were observed at the interface. Interdiffusivity in magnesiowiistite solid solution was determined as a function of iron oxide content. Phase relations between magnesiowilstite and olivine, and the growth rates of both phases, are also discussed

Jan 1, 1996

By J. Smuts

The mixed-valence iron silicate ISCORITE (Fe7Si010) was identified recently in a number of ironmakingmater1als, some of which were first produced more than a century ago. Although the existence of iscorite was not reported before 1967 and published phase diagrams do not make provision for it, the morphology of the phase in all the materials that were examined suggests that it is stable under a variety of conditions. It is shown that is-corite can accommodate various foreign cations in its lattice where they can replace Fe and/or Si. The morphology of is-corite in a number of materials of different origin is shown in relation to iron oxides and silicates in optical and SEM/BSE images.

Jan 1, 1991

By N. S. Raghavendran

Based on the weld pool length and width calculations due to an empirical model (1) for submerged arc weld metal, an elegant quantitative definition of tandem submerged arc welding is established. On the basis of this theoretical consideration optimum welding parameters for joining 25 mm thick low carbon steel plate in two passes by tandem wire submerged arc welding have been experimentally found out. An assessment of the metallurgical quality of weld metal and the dependence of mechanical propenies on pool overlap has been made. Also the solution of Rosenthal (2) etc. for a moving point source of welding, which was used as a guide line in formulating the empirical model for the calculations of weld pool dimensions, is compared with the solution of empirical model for submerged arc weld pool dimensions.

Jan 1, 1990

By Keiji Toyabe

Several purifying techniques have been developed for controlling the impurity levels in the copper electrolyte at Niihama Copper Refinery. These have been carried out as follows; i ) the study of the reaction in liberation made it possible to raise the current efficiency for arsenic removal by more than 50% and to decrease generation of arsine sharply. By applying this method, a good performance was attained at commercial operation. li) the antimony in the electrolyte can be successfully removed by contacting it with activated carbon. This procedure is applicable particularly when there is a large amount of antimony in the copper anode. lli) for the nickel sulphate recovery from the electrolyte, an electric evaporating system was developed. The characteristics of this process are, capability of continuous operation with less manpower, the high recovery ratio of nickel sulphate (more than 85% as nickel) and no black acid formation in the treated solution.

Jan 1, 1987

By R. E. Moore

The lining systems currently in use in BOF furnaces, certain steel ladles, and the slag line of electric are furnaces were developed during the late seventies through the mid-eighties using a trial and error method of combining aggregate, carbon sources, additives and binders. They are currently based on magnesia, graphite, metal additives and resin binders, the selections of each being tied to the anticipated intensity of the use conditions. The general functions of the respective constituents are well appreciated, however, there is still a great deal that is not known about how the socalled antioxidants protect the graphite nor how impurities from the graphite and the aggregate enter into the wear processes. In a simplified assessment of wear processes, it appears that if the deoxidized layer can be kept very thin, less than 810 mm in depth, and if the viscosity and quantity of the matrix glassy phases can be controlled to resist erosion of the deoxidized layer, lining life can be maximized for the various applications. This paper will discuss the characteristics of the starting materials systems currently being employed for applications requiring a deoxidation function to realize extended wear. It will not attempt to explain all the complex interrelationships between the respective constituents but will point to the potential for improvements through the use of improved constituents.

Jan 1, 1991

By Z. Yang

The flotation behavior of the. green algae Chlorella vulgaris and a wild Chlamydomonas spp. was studied in the presence of Zn(II) using dodecylammonium chloride as collector. At about pH 6. both organisms readily float as amine concentration approaches lx10-3 kmol/m3. In addition, electrokinetic measurements were made on the organisms as a function of pH in both the presence and absence of Zn(II). It was found that the Zn(II) has a considerably greater effect on the zeta potential of C. vulgaris than on Chlamydomonas. Zn(II) adsorption studies also indicated that C. vulgaris is able to accumulate more Zn from solution than the Chlamydomonas.

Jan 1, 1991

By K. A. Brunk

Newmont's research, operations, history and experience with pre-treatment of preg-robbing carbonaceous ores are described, with emphasis on the chemistry, physics and kinetics of chlorine treatment. Present operations, control strategy and projected changes are also described, including a summary of the adsorption of chlorine into pulps and off-gas scrubbing. Conditions of chlorination have been optimized by the use of Eh-pH diagrams of the gold-chlorine-water system, and have resulted in significant increases in gold recoveries and decreases in chlorine consumptions.

Jan 1, 1987

By O. Durand

The Cerro Verde Hydrometallurgical Plant, located at Arequipa in the southern part of Peru, started its operation in 1977 with a design capacity of 33,000 MT/year of copper cathodes. The plant has treated 61,055,000 MT of ore mainly oxides with a content of 1.01% total copper and 0.67% of soluble copper. The leaching plant has three pads that produce 4.0 gpl copper solution. The solvent extraction plant has four trains with three extraction stages, two stripping stages with a single mixer in all stages. The mixer-settlers are 316 stainless steel and the pumps are vertical turbines. The flowrates of 1,300 gal/mil of aqueous and 1,300 gal/min of organic at a 1/1 ratio. The electrowinning plant contains 208 commercial cells and 18 starting sheet cells. Each cell has 47 anodes and 46 cathodes. In addition to describing the hydrometallurgical plant, this paper also mentions efforts directed at reducing costs and improving operations. The initial results from leaching secondary sulfides, which started October 1985, are also discussed.

Jan 1, 1987

By Z. M. Zheng

Cyclic voltammetry, potential step, and ac impedance techniques were applied to study the electrochemical reaction of arsenopyrite in chloride solutions. The relationship between anodic current density and time in potential step measurements indicates that the oxidation of arsenopyrite is irreversible. The results of the constant potential coulometry show that the stoichiometric factor of the total electron involved in the overall reaction is 14. It is proposed that the dissolution of arsenopyrite is retarded by coverage of sulfur produced in the reaction as an intermediate product. The measured results of ac impedance strongly support the proposition. The proposed reaction mechanism also explains satisfactorily the charging current density and Tafel slopes measured in potential step measurements.

Jan 1, 1995

By J. S. Pitsillos

A new furnace tapping technique involving the simulation of a control valve at the exit to a furnace is being investigated. The purpose of this new tapping technique is to regulate the flowrate of liquid furnace products( slags, metals and mattes). Numerical modelling and experimental work has been carried out on tapping of slags leaving a SIROSMELT reactor and the results found to be in good agreement. Numerical modelling has also enabled prediction of the important industrial conditions for the onset of blockage from the shape of the pressure versus flowrate curves. Slag launder experiments have been carried out and a one-dimensional heat transfer model was used to evaluate the effectiveness of launder covers and different coolants. From the experimental results and mathematical model some launder design guidelines such as inclination angle, covers and coolants have been developed.

Jan 1, 1991

By Eiji Iwamura

"Two types of diamond-like carbon (DLC) films with different microstructures were prepared by unbalanced magnetron sputtering, and the tribological properties of the nanoscaled DLC multilayer coatings consisting of alternating layers of graphitelike and amorphous-like microstructures were examined. The DLC microstructure was characterized by certain features of graphite-like clusters, in that some of them had onion-like structures. The films filled with the clusters were obtained in a condition with an incidence of high influx of energetic electrons, and the other films without apparent cluster structures were formed in a condition with ion bombardment controlled by negative bias voltage applied to substrates. Stacking each film layer-by-layer, the nanoscaled multilayered coatings showed superior tribological properties to individual single-layered films due to the combination of properties induced by the difference of microstructures.IntroductionIn various tribologiql applications, it is necessary for diamond like carbon (DLC) coatings to have adequate adhesion, significant hardness and a concomitant low friction coefficient. A number of deposition techniques and coating structures have been proposed to achieve suitable DLC properties [1-3]. However it is still difficult to obtain a satisfactory level of combination of the properties particularly desirable for engineering applications.In this study, the features of unbalanced magnetron sputtering were demonstrated with the effect of ion and electron bombardment. Two types of microstructures , namely amorphous-like and graphite-like, were prepared by changing the condition of the charged particles bombardment during deposition. Using the difference of properties induced by the microstructures, nanoscaled DLC multilayered structures were examined in an attempt to improve tribological properties."

Jan 1, 2000

By B. Q. Li, Y. Shu, K Lynn

"This paper discusses the effects of magnetic field and internal radiation on the melt flow and solidification morphology during solidification processing of oxide crystals for optoelectronic and remote sensing applications. The numerical solution of the integral differential equation characterizing the internal radiation and the magnetohydrodynamic equations describing the magnetic and transport phenomena is obtained by applying the combined discontinuous and continuous finite element method. The results show that both internal radiation and an externally applied magnetic field can have important effects on the melt flow and solidification behavior during the melt processing of oxide materials.IntroductionOptical single crystals are widely used in optical and electronic devices. These crystals are often grown from high temperature oxide melts under strictly controlled conditions. As in the well-known single crystal growth processes for semiconductor wafers, thermal gradient in the melt is a major contributing fuctor to the oxide melt pool. Unlike the semiconductor single crystal growth processes, however, the oxide melt is semitransparent and internal thermal radiation plays an important role in redistributing the thermal energy in the melt pool. Our recent experience with pilot-scale plant measurements also shows that the oxide melt is electrically conducting, although its electrical conductivity is considered much lower than the liquid metal or semiconductor melt.The fact that the oxide melt is absorbing and emitting in the thermal radiation frequency range makes it difficult to study the thermal energy transport in the melt pool. This is because thermal radiation is governed by a hyperbolic differential equation, which is different from those describing the transport processes in liquids. Also, our understanding of how thermal radiation interacts with other transport mechanisms such as convection and conduction is rather limited at point in time, in particular in high temperature oxide melts for optical single crystal processing."

Jan 1, 2004