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By Georges J. Kipouros

Anhydrous neodymium trichlorids (NdCl3), containing ~1 weight percent neodymium oxychloride (NdOCI) was prepared by the dehydration of neodymium trichioride hexahydrate (NdC13.6H2O). Dehydration of the hexahydrate was conducted in three steps. First, the hexahydrate was slowly heated in air to about 250 °C until all the low temperature water of crystallization was removed. In the second stop, the neodymium hydroxychloride (Nd(OH)2C1) fanned in the first step was decomposed by heating under argon to 430 ° C. Finally the salt was ground and then treated with HCl gas at 330 °C until practically all of the NdOCl was converted to NdCl3.

Jan 1, 1992

By Godwin Beene

During recent years, copper and acid production from Nkana Smelter has formed a significant proportion of ZCCM's total output, but a number of problems affecting the smelter over the last decade have only been recently overcome. This paper discusses recent developments in the smelting practice, highlighting some of the operational problems experienced and associated solutions. The smelter performance over the decade is discussed and the innovations in the smelting technology employed to sustain production in the wake of limited re-capitalization are dealt with in detail.

Jan 1, 1999

By Xinli Wang, Matthew Andriese, Jiann-Yang Hwang, Zhiwei Peng, Byoung-Gon Kim

"The microwave reflection loss (RL) of ferric oxide is studied in the temperature range from 297 to approximately 1400 Kat frequencies of 915 and 2450 MHz. It is shown that the maximum microwave absorption with RL of -38.46 and -35.97 dB can be obtained for ferric oxide having thicknesses of 0.03 and 0.01 m at 915 and 2450 MHz, respectively. The maximum absorption peak with RL below -10 dB is in a 250 K temperature range from 723 to 973 Kat 915 MHz, which shifts to the range between 823 and 1073 K at 2450 MHz. This migration is in good agreement with the variation of the dielectric loss tangent of ferric oxide.IntroductionMicrowave irradiation has distinguishing characteristics such as volumetric and selective heating compared with conventional methods, leading to extremely broad applications in materials heating and processing [1-5].The efficiency of microwave heating was found to be dependent on various factors, such as microwave power [6], frequency [7,8], radiation time [8], applicator geometry [8], sample microwave absorption properties and position as well as dimension [9-11 ], etc. Among these parameters, sample dimension plays an important role but is usually neglected by researchers in microwave processing of materials. In fact, although numerous studies have been directed toward the utilization of microwave energy to assist materials heating and processing, few reports were released on the effect of sample dimension [12,13].This is because all aforementioned factors influencing microwave heating generally exert interactive effects to each other during the heating process, making clarification of the effect of sample dimension difficult. Therefore, it is necessary to propose a parameter or concept for quantifying the effect of absorber dimension on microwave heating, increasing heating efficiency."

Jan 1, 2013

By W. William Culver

James Douglas became known in the nineteenth century for two reasons fundamental to his mining career: (1) his experimental work with copper hydrometallurgy, and (2) his grasp of the idea that the quantity of copper ore matters more than the quality. On the first reason, there is a moment for any technology that’s critically important—when it moves from an area of scientific interest to one that companies are founded on. This paper examines the original 1869 Hunt and Douglas Copper Process in the context of science and engineering as they were in the 1860 and 1870s. It was a “humid” process, developed at Quebec’s Harvey Hill Mine. Chemically, the Hunt and Douglas vat leaching process succeeded, but not the original companies using it. On Douglas’ understanding of ore quality versus quantity, luck had it that the first company to field test the Hunt and Douglas Copper Process was in Chile. The Hunt and Douglas patent made that transition from experimental model to operational plant in 1870 when the Compañia de Minas de la Invernada was organized in Valparaíso. As a joint-stock company, Invernada spread the risk of investing in the revolutionary, but untested, Hunt and Douglas Process. The company brought Douglas to Chile as a consultant in 1871. His experience with hydrometallurgy, combined with what he learned about the copper business while in Chile, set him off on a career in metal mining that both surprised Douglas and made him wealthy.

By P. N. Anyalebechi

The effects of a cross-hatched grooved mold surface topography, casting speed, and superheat on the morphology of solidifying shells of aluminum alloy 3003 have been characterized by a series of immersion tests. The cross-hatched grooves were 0.232 mm deep with wavelength or spacing between 1 mm and 15 mm. The shells solidified at casting speed of less than 10 mm/s on the 1 mm spaced cross-hatched grooved mold surface were fairly uniform with little or no localized variations in thickness. However, the propensity for non-uniform shell growth morphology was exacerbated by an increase in casting speed, melt superheat, and the wavelength of the cross-hatched grooves. This is provisionally attributed to their effects on interfacial heat transfer and wetting of the mold surface by the molten metal.

Jan 1, 2008

By T. V. Swaminathan

Monazite sand is normally processed by, the caustic soda route to produce mixed rare earths chloride, thorium hydroxide and trisodium phosphate. Bulk of the mixed rare earths chloride is used for the preparation of FC catalysts. Recently some of the catalyst producers have shown preference to cerium depleted (lanthanum enriched) rare earths chloride rather than the natural rare earths chloride obtained from monazite. Therefore, a process for producing cerium depleted rare earths chloride, cerium p thorium and uranium from Rare earths + thorium hydroxide obtained by treating monazite based on stepwise hydrochloric acid extraction, was developed in our laboratory. The process involves drying of the mixed rare earths-thorium hydroxide cake obtained by monazite-caustic soda process followed by stepwise extraction of the dried cake with hydrochloric acid under specified conditions.

Jan 1, 1989

By Sasa Djokic

In developed countries, the difference between demanded and produced quantities of non-ferrous and rare metals are compensated by secondary raw materials recycling and reprocessing of by-products from both ferrous and non-ferrous extractive metallurgy. Utilization of non-ferrous and rare metals from the metallic secondary raw materials is very significant, both for recovery of the metal value and contribution to the environment protection. Similar to all non-developed countries, the extractive metallurgy in Serbia was based on available natural resources and not so strict environment protection regulations, which was either insufficient or completely absent. Today, Serbia is at the beginning of development of efficient and economical technical and technological solutions in order to ?ecologize? technogenic systems by waste materials, secondary raw materials and degraded soils regeneration (by recycling and revitalization). Several metallurgical technogenic systems in Serbia, together with secondary raw materials classification according to their potentiality for metal extraction by using the existing technologies and expected economical and ecological effects of recycling, are discussed in this paper.

Jan 1, 2005

By José R. Parga

In some parts of the Comarca Lagunera with population of about 2.5 million people, situated in the central part of northern México, chronic arsenic poisoning is endemic and severe adverse effects attributed to As exposure have been reported. Lifetime exposure to arsenic will develop classical symptoms of arsenic poisoning such as skin pigmentation changes, gastrointestinal disturbances and neurological changes. There are several methods available for removal of arsenic from well water in large conventional treatment plants, however a very promising electrochemical treatment technique that does not require the addition of chemicals or regeneration is Electrocoagulation (EC). The EC operating conditions are highly dependent on the chemistry of the aqueous medium, especially conductivity and pH. In this study, Powder X-ray Diffraction (XRD), Scanning Electron Microscope (SEM), and Transmission Mössbauer Spectroscopy (TMS) were used to characterize the solid products formed at iron electrodes during the EC process. This study will provide an introduction to the fundamental concepts of the EC method. Finally the results of this study suggest that the presence of maghemite and magnetite particles can be used to remove arsenic (III) and arsenic (V). In the field pilot plant scale study more than 99% removal of As species from groundwater is achieved.

Jan 1, 2005

By Jesús Contreras

Within its programme for continuous improvement and cultural change, Atlantic Copper has installed the Six Sigma methodology as a basic tool for the improvement of management techniques in all its production centres. Following an implementation period, the methodology is widely used for analysis and improvement, not only in the fields of production and maintenance, but also in other areas of the business such as supplies or energy management. The present paper describes, phase-by-phase, the project that was developed to improve the quality of converter slag through the application of Six Sigma techniques, from the initial set up to the final results obtained.

Jan 1, 2005

By T. W. Turk

In May 1984, Davy McKee Corporation was awarded a contract for engineering design, procurement assistance, project management and startup services for two gold recovery plants? in the People's, Republic of China (PRC). The basic design of these two projects was to be accomplished by a combined effort of the Chinese and Davy McKee Corporation (DMC). The, design goals were to provide a state-of-the art plant while maintaining Chinese standards and design practices whenever possible. Chinese-manufactured equipment was to be used as much as possible. This paper discusses the project organization and procedures developed to accomplish the design goals, the process selection and design, and the selection and procurement of equipment outside of the PRC. Design development for grinding, leaching and carbon adsorption, and gold recovery are discussed in detail. The major goal of process selection and design was to provide common criteria for both plants. Equipment .sizing and selection was identical for carbon-in-leach adsorption, gold recovery, acid washing, and carboo regeneration for both plants. Of special importance is the design of the wastewater treatment system. Due to the cl0se proximity of a major population area, slurry discharging from these mines must be treated to meet drinking water standards. The process development and design of this system is also discussed in detail.

Jan 1, 1989

By Peter Ryan

A patented process for agglomeration of Smelter ESP dusts is described. Addition of suitable binders followed by compaction, transforms fine, difficult to handle material into a dry, flowable agglomerate suitable for plant reentry. Details for the agglomeration process metallurgy and laboratory pilot plant testing are discussed. An example of full scale plant operations is described.

Jan 1, 1999

By Luciano R. G. Santos

Keywords: biosorption, cadmium, copper, biomass, spent zeolite. The majority of the industrial activities produce some kind of solid wastes. In this work two industrial residues (spent zeolite and wood sawdust) were chemically modified to increase their heavy metals sorption capacities. Manilkara longifolia (a Brazilian plant known as parajú) sawdust was first treated with NaOH and modified with different citric acid concentrations (0.6-1.2 mol/L) at 120°C, for 90 min. Infrared spectroscopy confirmed the presence of carboxylate groups in the wood structure as result of their mixing. Similarly, spent zeolites were also submitted to a chemical treatment (NaOH) to remove carbon deposited during oil cracking and to recover its sorption capacity. Batch experiments carried out at ambient temperature showed that both materials present sorption capacity for copper and cadmium comparable to weak acid ion exchange resins. A maximum of 78 mg-Cd/g and 59.7 mg-Cu/g as well as 29.9 mg-Cd/g and 14.6 mg-Cu/g were observed for the sawdust and the zeolite, respectively. The results were modeled according to the Freundlich and Langmuir equilibrium isotherms and compared with results of other studies.

Jan 1, 2005

By Seetharama C. Deevi, Mohammad R. Hajaligol, Sarojini Deevi

"Carbides and nitrides of iron are being considered as magnetic materials for high-density recording due to their chemical stability and high-saturation magnetization values (> 100 emu/g). Iron carbides and iron nitrides with magnetic properties suitable for magnetic media were synthesized by employing a novel synthesis procedure based on fluidization of powders in reactive atmospheres. Fluidized-bed reactors of laboratory, bench, and pilot scale were employed for the synthesis of iron carbide, FeSC2, by reducing and carburizing U-Fe203 in the temperature range of 300 to 550 ºC. A temperature of 400· ºC and a reaction time of 2 to 3 h are found to be optimal for the synthesis of iron carbide. When the carburization was carried out in a reducing and carburizing atmosphere such as carbon monoxide, nucleation and growth of FeSC2 occurred directly from Fe304 with no intermediate phases such as FeO or Fe. Longer carburization times resulted in the deposition of carbon on the surfaces of FeSC2 particles due to Boudouard reaction, and higher temperatures favored the formation of a mixture of carbides such as FesC2 and Fe3C. Iron nitrides were synthesized by reducing u-Fe203 in the temperature range of 350 to 550 ºC, followed by nitriding in the temperature range of 350 to 550·ºC. The powders were characterized using X-ray diffraction, scanning electron microscopy, thermogravimetric analyzer, and a vibrating sample magnetometer.IntroductionRecent demand for high-quality recording of optical, electrical, and audio signals generated interest in magnetic tapes with high-recording densities as compared to the conventional magnetic tapes based on U-Fe203. At present, commercially available magnetic tapes contain maghematite, U-Fe203, as a magnetic material with a saturation magnetization of90 emu/g and a coercive force of 400 Oe. Recording of signals at a higher density per unit volume of magnetic material demands magnetic materials with high-saturation magnetization and a reasonable coercive force. Although metallic iron particles possess a saturation magnetization of 130 to 150 emu/g and a high coercive force of 1000 Oe, the gradual oxidation of iron-to-iron oxides (of lower saturation magnetization) prevents the use of iron particles for high-density recording. In contrast, iron carbides such as FesC2, Fe7C3 and iron nitrides such as Fe4N and Fe3N possess excellent magnetic properties coupled with good electrical conductivities and high hardness. The carbides and nitrides of iron have generated significant interest as magnetic materials for the next generation of magnetic tapes due to their unique magnetic properties and relatively greater oxidation resistance as compared to metallic iron particles [1-4]."

Jan 1, 1994

By Neil E. Ryan

Because of their chemical reactivity and affinity for oxygen, rare-earth elements are difficult to extract, and due to their close chemical similarity, it is an exacting task to separate one from the other. Nevertheless, these same characteristics can be used to benefit other metals by enhancing their resistance to high-temperture oxidation/corrosion and by inhibiting their corrosion in aqueous environments. This paper gives an overview of the use of rare-earths: [a] as alloy additions, [b] in coatings, and [c] when added to hostile environments, to retard rates of high- temperature oxidation and inhibit aqueous corrosion.

Jan 1, 1992

By Sharif Jahanshahi

Calcium ferrite slags are often associated with Professor Yazawa due to his pioneering work on the thermodynamics of this type of melts. Over the past years CSIRO has invested some effort in studying physico-chemical properties of such melts to fill in some gaps in our knowledge and explore opportunities for application of the understanding developed. These investigations cover thermodynamics, transport properties of calcium ferrite based slags, as well as the kinetics of reactions of such slags with refractories. The present paper provides an overview of some of these studies and highlights some of the interesting behavior of such melts, The oxidation state of copper and arsenic in calcium ferrite based slags are predominantly Cu+ and As3+, respectively, at oxygen potentials below 10-7 atm. The concentration of CU2+ in such slags becomes significant at oxygen potentials of greater than 10-7 atm at 1300 °C. The activities of CuO0.5 and AsO1.5 in calcium ferrite slags show strong deviations from the Raoultian Law, while that of CoO is very close to ideal behaviour with respect to pure solid CoO. Addition of SiO2 to calcium ferrite slags can have significant effects on the activities of FeO and Fe2O3 and hence the stability of magnetite phase. Transfer of oxygen in calcium ferrite slags is fast with diffusivity of 2x 103 cm2/s at 1350 °C and activation energy of 16 kcal/mol. Presence of solid phases, such as magnetite, has pronounced effect on the viscosity of calcium ferrite slags. The observed dependence on solid loading and shear rate indicates deviation from Newtonian behaviour. The interfacial tension between copper mattes and calcium ferrite slags is strongly dependent on the matte grade, with the determined values being much lower than the corresponding ones for interfacial tension between similar mattes and iron silicate slags. MgO, Cr2O3 and MgCr2O4 have low solubility in calcium ferrite slags and their solubility increases with increasing copper oxide content of the slag at 1300°C. The oxidation state of the slag has strong effects on phase transformation, dissolution rate and disintegration of refractories in calcium ferrite slags. Other key factors with major impact on slag-refractory interactions include viscosity and surface tension of slags as well as the contact angle between slag and refractory material,

Jan 1, 2003

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 Yuanbing Ling

Keywords: Calcium sulfate, Sulfuric acid, Phase transformations, Thermodynamic analysis As part of a boarder research project, seeking the development of a cost-effective process for direct production of the high value material, -calcium sulfate hemihydrate, from sulfuric acid at atmospheric as opposed to elevated pressure conditions, the fundamental work presented here has been undertaken. This includes experimental monitoring of phase transformation reactions and thermodynamic analysis of the relationships among the various phases, namely, calcium sulfate dihydrate, hemihydrate and anhydrite in aqueous sulfuric acid solution at temperatures ranging from 20oC to boiling point.

Jan 1, 2004

By A. A. EI-Geassy

High-grade iron ore fines rejected from the DRI plants (>96%Fe2O3) were isothermally reduced in 30-60%CO/H2 gas mixtures at 973-1273K. The freshly reduced reaction products were then subsequently carburised in either Hz/CO or H2/CO/S mixtures at 823-1 073K for 30-120 min. The thermogarvimetric technique was used to follow up both of reduction and carburisation reactions as a function of time. The carburised samples were characterized by X-ray and Mossbauer techniques. Chemical and carbon analyses were also applied. The influence of temperature and gas composition on the reduction behavior was investigated. The calculated values of apparent activation energy, application of gas-solid mathematical formulations were correlated with the microstructures to predict the reduetion mechanism. The influenee of carburization time, temperature, CO contents in H2/CO or H2/CO/S were investigated. A conversion extent of Fe to Fe3C was taken as a measurable index for the efficiency of carburization rcaction under the different experimental conditions.

Jan 1, 2003

By D. Papazoglou

This work was undertaken to investigate the thermodynamic and kinetic feasibility of using hot sulfur dioxide bearing gases from smelting processes to selectively sulfate the nickel in nickel laterite ores for subsequent extraction in water. The environmental benefits of this approach, as opposed to releasing the gas to the atmosphere, and the economic benefit of directly utilizing the SO2 rather than converting it to sulfuric acid are strong drivers for such a process. A thermodynamic analysis indicated that selective sulfation of the nickel could be feasible under appropriate conditions and these were explored through a series of laboratory scale experiments. Laterite samples were reacted at temperatures between 500 and 800°C with an equilibrated mixture of sulfur dioxide, oxygen and nitrogen in a fixed bed reactor. Tests were conducted on saprolitic ore from Bulong, Western Australia:, limonitic ore from New Caledonia and gamieritic ore from Indonesia. Nickel extractions were highest from the limonite and relatively low from the other ores. The maximum selective extraction of nickel from the limonite in a single stage sulfation was 73%. Sulfation of other elements present in the laterites was also examined. A two-stage process was also identified which involved sulfation using a strong sulfation potenrial followed by weaker sulfation potential to attempt to convert ferric sulfate formed in the first stage to ferric oxide. This increased the extraction for the limonite ore to around 84% Ni, 95% Co and 2% Fe. Direct sulfation of laterite could be feasible in locations where sulfide smelting or roasting operations are relatively close to laterite deposits.

Jan 1, 2003

By H. Y. Sohn

The considerable progress made in the sulfide smelting technology since the first International Sulfide Symposium of 1983 is discussed. The new developments and innovations have largely been driven by the recognition of environmental concern as well as the need for increased productivity. The smelting technologies for various nonferrous metals are reviewed, with an emphasis on the industry trend towards larger plants and continuous processes. The tremendous advances made in process modeling and computer simulation to describe the complex smelting processes are also reviewed. The goal of these mathematical models is the quantitative description of the processes and the reactors that will provide a means for the control and optimization of smelting operations as well as the optimal design of the operating conditions and the reactors. Environmental issues remain a key consideration in the smelting industry. One of the most remarkable improvements made in the last fifteen years since the 1983 Sulfide Smelting Symposium is the rapid increase in the sulfur capture by nonferrous smelters. This and other related issues are briefly discussed. Finally, the challenges that the smelting industry faces as the new millenium approaches are discussed. The industry continues to face technical challenges to improve productivity and efficiency, while being responsive to ever-increasing public pressure for environmental protection. It also faces external challenges from factors that may cause the reduction of metal uses as a result of substitutions by other materials. Another serious challenge and dire consequence that the primary metals industry is expected to face is the serious diminution of university-educated manpower as well as basic-research output. To remain competitive and healthy, the industry should take up the void left by the complete disappearance, at least in the U.S., and the reduction in other nations, of the governmental support of higher education and basic research in the field of primary metals production.

Jan 1, 1998