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02, NaCI03, H202, Na0CI and Ce+4 have been examined as oxidants in an alkaline carbonate system for uranium in in situ leaching. The South Texas and New Mexico ores contained up to 2.6 meqJg of reducing compounds which consume oxidants in the leading operation. Leaching rates did not increase linearly with the oxidation potential of the oxidants. A mild oxidant can be used to maximize uranium oxidation selectively and oxidant efficiency. 02 can oxidize most of the uranium mineral with an adequate rate and high oxidant efficiency.

Jan 1, 1990

By A. Barba, M. P. Gómez, F. Puertas, M. Palacios, M. F. Gazulla, S. Martínez-Ramírez, I. García-Díaz

"The present study explores the reactivity and burnability of cement raw mixes containing fired red or white ceramic tile wastes or combinations of the two as alternative raw materials. The results showed that the new raw mixes containing these wastes are technically viable. The reactivity and burnability of the new raw mixes have been evaluated; confirming very good results when the particle size of wastes was less than 90 µm. The chemical and mineralogical compositions of the new clinkers were comparable to clinker manufactured with conventional raw materials. The mix of red and white ceramic tile waste was found to perform as well or better than each type of waste separately, a promising indication that separation of the two would be unnecessary for these purposes.IntroductionPortland cement clinker production consumes large amounts of energy (850 kcal/kg clinker) and has a considerable environmental impact. This involves massive quarrying for raw materials (limestone, clay etc), as it takes 1.7 tonnes to produce one tonne of clinker, as well as the emission of greenhouse and other gases (NOx, SO2, CO2) into the atmosphere. Around 850 kg of CO2 are emitted per tonne of clinker produced.The cement industry is looking for solutions to these problems, to attain sustainability and comply with the Kyoto Protocol commitments [1,2]. For that reason, experimental ways are being explored to develop cements whose manufacture is less energy-intensive, less damaging to the surrounding environment and with lower tendency to emit polluting gas. One of the reach this objective is the use of industrial waste and by-products as alternative materials for cement manufacture. Such alternative materials may partially replace fuel [3,4], conventional raw materials [5-8] or clinker in the final composition of the cement [9]."

Jan 1, 2008

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 Vasil Kopaleishvili

The bainitic Fe-C-Si alloys with optimum content of retained austenite serve as ?containers? for storing of hydrogen. Both the vacancies of fcc lattice and the possibility of forming hydrides of silicon and other alloying elements will be used. The idea is based on our scientific hypothesis. There is the silicon threshold (Si=0,50%) in "Fe-Si" system and Fe-C bainitic alloys, above which it causes self-organized phenomena: sudden increase of hydrogen solubility and amount of retained austenite in the alloy after ??ß transformation, formation of two supersaturated solid solutions <a??r>, "rejuvenation? and its reverse process. Rapprochement of iron atoms when Si=0,50%, causes appearance of new covalent forces where uncompensated electrons of 3d-subshell are involved and it provokes synergetic phenomena. They ?free? silicon atoms from the previous bonds. After that silicon itself becomes a getter of hydrogen using vacancies (14) of 3P2(6)d0(10) subshell and it results in sudden increase of hydrogen solubility in metal. Simultaneously sudden decrease of iron activity takes place. That in its turn ?releases? the carbon. Thus, its redistribution, controlling the bainitic transformation, is hastened. It stipulates for creation of ?brittle bainite" B[a(C,H)+?r(C,H)] after ??ß transformation. While weathering of metal, "rejuvenating", hydrogen diffuses in ?islets? of retained austenite and ?relaxed bainite? (B[(C)+?r(C,H+H)]) is obtained. When heating austenite ?(C,H) is obtained, and after cooling ?brittle bainite? is obtained, etc. Presented scientific hypothesis explains the available experimental facts ("rejuvenation? and its reverse process, graphitization, weldability, forming of flakes, reaching high strength, etc.) in a new manner, as well as, gives real opportunity for creating of new trends in many fields, e.g. iron based HAA. Provisional data having been obtained are encouraging.

Jan 1, 2006

By Bob Hannah, Peter C. Hayes

The changes that are happening in the world of metallurgy, and with it university education, are generational and require generational responses. Some of the key issues facing metallurgical education and ongoing professional training are explored. What will be required of metallurgical engineering professionals in the coming decades? What knowledge and skills will be needed? How to provide the educational and learning pathways, and how to attract smart young people into this profession? These are issues more readily addressed by tertiary institutions in conjunction with industry; perhaps the greater challenges lie in building and maintaining competencies post-graduation. There is a need to establish and maintain a system that supports graduates and enables them to develop further into competent expert engineers able to successfully address complex engineering challenges.

Jan 1, 2014

By Pengfu Tan

Electric arc furnace (EAF) dust from the steel industries is listed by the United Sates EPA as a hazardous waste under the regulations of the Resource Conservation and Recovery Act due to the presence of lead, cadmium and chromium. The disposal of the approximately 650,000 tons of EAF dust per year in the U.S. and Canada is an expensive and unresolved problem for the majority of steel companies. The Waelz process has been considered as the best process for treating EAF dust. A process model, combined thermodynamic modeling with heat transfer calculations, has been developed to simulate the chemical reactions, mass and heat transfer and heat balance in the kiln. The injection of air into the slag and the temperature profile along the kiln has been modeled. The effect of (CaO+MgO)/SiO2 on the solidus temperature of slag has been modeled also and discussed. Some optimizing results have been presented in this paper.

Jan 1, 2005

By Mishark Nnabuchi

A heterojunction of PbS - CuS thin film has been grown on glass slides by SGT. The films were annealed for 1hr at temperature of 373K and 423K respectively. The optical properties were characterized using a UNICO UV - 2102 PC Spectrophotometer at normal incidence of light in the wavelength range of 200 - 1000nm. The minimum percentage transmittance was observed to be 34% for sample A and 25% for sample B within the same optical region. The band gap energy was determined from the spectra to be 2.05eV for sample A and 1.85eV for sample B which gave a band shift of 0.20eV. It can thus be concluded that the optical properties of the films within the VIS - UV - NIR can find application in solar thermal technology, particularly as antireflection coating, window materials and as good materials for selective solar cell fabrication.

Jan 1, 2010

By Payman Roonasi

Having knowledge of mechanism of magnetite formation is essential in a number of industrial processes including magnetite synthesis and corrosion of iron. In this study, magnetite nanoparticle was synthesized via two different ways; coprecipitation of iron (II) and (III) and oxidation of ferrous hydroxide. The samples were characterized using X-ray diffraction (XRD), Mid-Far IR spectroscopy, scanning electron microscopy (SEM), chemical analysis for determination of Fe II/Fe III ratio and ICP-MS for iron isotopic ratio (56Fe/54Fe) measurement. Since fractionation of iron isotopes depends on reaction rate and bonding strength, interpretation of the isotopic data with respect to the possible mechanisms is discussed. No fractionation of iron isotopes was observed for the magnetite synthesized by coprecipitation, whilst magnetite formed from ferrous hydroxide showed higher abundance of 54Fe compared to 56Fe in the beginning of reaction, implying the significance of the following reaction:

Jan 1, 2009

By Jae R. Lee

Keywords: Self-propagating high temperature synthesis, AlN, Powder synthesis The particle size and shape effects of starting raw powders on the synthesis of aluminum nitride by self-propagating high temperature technique under high nitrogen pressure were investigated with various AlN diluents and Al reactants. It was found that the structure of beds of the starting raw particles largely affected the pore channels for nitrogen gas infiltration as well as the passages for combustion propagation before and during the reaction, resulting in the morphology and purity changes of the synthesized products. The AlN product of purity over 98% with about 30 microns was obtained.

Jan 1, 2005

By Tammy G. R. Portela

A comparative characterization of the dimensional and mechanical properties as well as structural aspects of two different types of fibers extracted from the leaves and petioles of the buriti palm tree was performed. A statistical analysis revealed that both types of fibers present a significant dispersion in length and equivalent diameter. However, the corresponding intervals of dimensional variation are sensibly different. The tensile properties showed that both types of fibers display a tendency of higher strength for smaller diameters. Moreover, the fibers extracted from the leaves depict a comparatively lower strength. By contrast, the fibers from the petiole present an average strength sufficiently high for the use as reinforcement of polymeric composites. The structural aspects of tensile-rupture fibers, characterized by scanning electron microscopy, showed marked distinction in the microstructure and fiber behavior of both types of investigated fibers. This could explain the differences in mechanical behavior

Jan 1, 2010

By R. Ressel

Keywords: ferrovanadium, thermodynamics, phosphorus Recyclable material is rapidly gaining in importance as a source of raw materials in industrialized countries. This is also the case in the production of ferrovanadium, where, increasingly, materials such as discarded capacitors, spent catalysts, slag, dust and sludge are used. As the V-content in the raw material varies greatly, the demands on process technology are very high. The share of perturbing elements depends very much on the source of the raw materials, which, in turn, makes a corresponding optimization of the various refining steps necessary. The raw materials are mostly available as oxides, which means that carbon, silicon or aluminium are used as reducing agents. Thermodynamic calculations were used to show especially the behavior of vanadium and phosphorus at different process conditions.

Jan 1, 2005

By Jun Lu, Min Chen, Wei-jian Su, Jian-zhong Luo, Yu-tao Lei

"In the case of treating phosphatizing wastewater containing zinc, zinc had an impact on the solution chemistry, especially on pH. Fe2(SO4)3 and CaCl2 were used as precipitators to remove phosphate from zincic phosphatizing wastewater and the optimum pH was investigated. Zinc ion had a significant effect on the optimum pH. The optimum pH ranges were 12.10(inlet concentration of 15.67mg/L, outlet concentration of 9.53mg/L), 3.04-5.50(inlet concentration of 11.97mg/L, outlet concentration of 0.44-0.26mg/L), and more than 10.72(inlet concentration of 12.24mg/L, outlet concentration of less than 0.47mg/L) under the conditions without precipitator, with Fe2(SO4)3 and with CaCl2 respectively.Introduction Phosphate coating is commonly used for protective coating of machine elements. Including oil removal by caustic washing, rust removal by acid washing, phosphatization and inactivation, the phosphatization process produces wastewater containing inorganic salt of high concentration, especially the phosphate, beyond the environmental standards and polluting environment seriously. What’s more, the wastewater from zincic phosphatizing technology also contains another pollutant, zinc. At present, Chemical Precipitation (CP) and Biological Nutrient Removal (BNR) are two of most common technologies of phosphate removal. BNR, such as A/O, A2/O and UCT technology, is suited for wastewater containing organ phosphorus of low concentration and CP for wastewater with phosphate of high concentration [1]. Researches on CP treating wastewater containing phosphate of high concentration, mainly focus on adding quantity of precipitators[2-5] and coagulants[2-4] and the choice of technologies[3-9]."

Jan 1, 2008

By William A. Enrico

Umicore acquired the Pirdop Smelter in a privatization offering by the Bulgarian government in September 1997. Since that time, an investment program has been conducted to increase capacity to 225 000 tons per year of anode copper, while improving the environmental performance to meet Bulgarian and European standards. A significant part of this investment program involved reconstruction of the three Peirce-Smith converters and the associated gas handling system. During the period June, 2000 through April, 2002, converter capacity was increased, the existing water-cooled hoods were replaced, the waste heat boiler was replaced by two evaporative coolers, the dry ESP&apos;s were rebuilt and extended, and a Converter Control System (CCS) installed. From 2002 until the present, a continuous improvement of operating and environmental performance has been achieved. This paper will describe the converter reconstruction project, the operational, maintenance, and environmental improvements achieved since then and additional projects presently under consideration.

Jan 1, 2005

By Christopher Gammons

In developing countries throughout the world, gold ores are being processed by mercury amal-gamation, a technique long banned in the U.S. - unless a retort operation is used for mercury recovery - due to mercury toxicity and its effects on the environment. Amalgamation is a simple process that involves contacting a ground, slurried concentrate or ore with mercury in a slightly agitated vessel, usually for several hours, The amalgamated mercury is separated by gravity and then filtered through a fine cloth to collect the gold amalgam as a sponge, which is then fired to remove the final remnants of mercury and produce high quality gold. However, in Peru and other developing countries in South America and throughout the world, tailings are simply discarded into uncontrolled drainages and ponds and the sponge is fired in the open air. Clearly, in this case, environmental friendly and, to make matters worse, is typically conducted by family members of all ages without proper protection. Furthermore, the technique is inefficient, yielding approximately 50% gold recovery. For the past two years, faculty members from Montana Tech in Butte, MT, USA and the Universidad Nactonal del Altiplano in Puno, Peru have teamed to study the La Rinconada Mine Complex located in southern Peru approximately 100 kilometers north of Lake Titicaca and 25 kilometers west of Bolivia. The mining complex is over 5,000 meters above sea level and exists at the foot of a receding glacier in the Andes Mountains. A suite of soil and water samples collected in 2001 documented extensive Hg contamination in the Rinconada area [1]. The present paper summa¬rizes a follow-up investigation in July-2002, in which water samples were collected at numerous locations along the 200 km length of the Rio Ramis, from the Rinconada mine com¬plex to Lake Titicaca, In addition, we report new results of Hg analyses of fish from Lake Titi¬caca, The results of this study have relevance to safety and health concerns for the miners as well as people in downstream communities.

Jan 1, 2003

By Ovidiu Pasca

The Phelps Dodge Miami Smelter utilizes four Hoboken converters to process molten matte from the Isasmelt vessel. This paper presents past and present improvements in operation, maintenance and process optimization, based on data collection, which has led to increased converter campaign life and copper throughput.

Jan 1, 2005

By Chao Li, Shuai Wang, Hongxu Li, Lifeng Zhang, Xie Yang

The method of chloride-hypochlorite leaching has the advantages of short process, low pollution and higher in reaction rate compared with the traditional leaching method. In this research, NaCl - NaClO solution is used to leaching gold from a refractory gold concentrate, and the influence of NaCl and NaClO concentration, reaction time to the leaching rate were investigated in this experiment. The raw materials and the leaching residue were characterized by a series of analysis methods such as XRD, XRF, SEM and EDS. Results indicate that the leaching rate and the desulfurization rate can be achieved at 96.26% and 98% with most optimum conditions as follows: NaCl concentration 50g/L, NaClO concentration 200g/L, Liquid-solid ratio 10:1, the best reaction time was 150 mins. And these conditions should be guaranteed pH<8.0, ORP>900mV.

Jan 1, 2015

By Hui Wang

With the great increasing use of nickel metal hydride batteries recently, the waste of this kind batteries have been paid for close consideration. For the main reason that the waste of the batteries contained precious metals and lanthanide which cost great lose. This paper introduces the pyrometallurgical process of recovering nickel and cobalt from the waste of the nickel metal hydride batteries. Particularly, the waste for the process was from factory during the producing program. The use of designed solvent to divide nickel and cobalt in melted state from the waste is described. Also, the result of the nickel and cobalt and melted gangue that mainly consist of lanthanide oxide are included in details. The aim of the paper is to find out a simple and feasible way to reuse waste from nickel metal hydride batteries.

Jan 1, 2009

By J. M. Tannenbaum

A depth-sensing micro-indentation technique is developed for evaluating mechanical properties of materials at elevated temperatures (to 1200°C). System description and design considerations of the test apparatus are described. Based on Hertzian spherical indentation approach, the micro-indentation test apparatus is capable of determining Young?s modulus and creep strength of test materials with flat, tubular, or curved architectures from room to 1200°C under either air or controlled gaseous environments. Calibration tests were conducted on a H13 Tool Steel coupon from 22°C to 500°C and single crystal Haynes 230 alloy at 1000°C with excellent agreement to the literature values. Indentation creep tests of Haynes 230 alloy were carried out at 1200°C with preliminary results showing good correlation to creep exponents. Further system refinements will be investigated, and additional testing will be conducted.

Jan 1, 2010

By Bowang Xiao

Recently more and more attentions are paid to high pressure hydrogen quenching (HPHQ) for its advantages such as environmental friendliness, low distortion, etc, compared to oil and water quenching. In HPHQ process, heat transfer coefficient (HTC) usually varies from part surface to surface because of the intense variation of gas velocity around the part. This article studies the effect of HTC distribution on part distortion after HPHQ and shows that finite element simulations considering HTC distribution predict different distortion from these without considering HTC distribution. It is also pointed out in this article that HTC distribution can be optimized by adjusting part orientation and HPHQ condition so that part distortion is minimized.

Jan 1, 2010

By Katsuyoshi Kondoh

The utilization of silica particles originated in rice husks as reinforcements of magnesium composites was discussed. By using the solid state reaction of rice husk silica particles with magnesium powder, P/M magnesium based composites dispersed with the magnesium silicide (Mg2Si) and magnesium oxide (MgO) were fabricated. High-purity silica particles were originated from rice husks, one of the major agricultural wastes, via the citric acid leaching treatment and combustion in air. The effects of the silica particle characteristics such as size, crystalline and porous structures, on the reactivity of silica and magnesium to synthesize Mg2Si intermetallic were discussed. Amorphous silica was more useful for this reaction than crystalline one. The reactivity of rice husk silica was superior to that of the conventional mineral silica particles because of not only its amorphous structure but the larger specific surface area due to their pore structures. In the case of the green compact of the mixture of the rice husk silica and Mg powder, the silica particle size was not effective on the reactivity because the coarse particles were fractured into fine ones by cold compaction. The distribution of Mg2Si intermetallics of magnesium powder composites consolidated by SPS process was investigated by XRD and SEM-EDS analysis. Their mechanical and physical properties were also evaluated in detail.

Jan 1, 2009