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"Mixing phenomena in a bottom blown air-stirred one-seventh water model of CLU (Creusot-Loire Uddeholm) reactor was studie9-using three different configurations of straight circular nozzles fitted axially at the bottom of the vessel. The mixing time has been determined by pH measurements at various gas flow rates, bath heights and nozzle orientations in the presence and in the absence of a second phase.Experimental results reveal that the mixing time decreases with increasing gas flow rate. For a given gas flow rate the mixing time increases non-linearly with increasing bath height. Off-center configuration gives slightly lower mixing times as compared to center configuration. It is found that the contribution of buoyancy to the total stirring energy density is very small, but its contribution increases with increasing bath height. In the presence of an upper oil layer, the mixing time increases significantly for all configurations.IntroductionIn high temperature metallurgical melts mixing is carried out by injection of a gas either from top or bottom of the vessel in order to accelerate the rates of chemical reactions and to promote bath homogenization. When a gas is injected into a liquid through a submerged lance, porous plug or nozzle, the gas, rising as a two phase plume to the surface, imparts momentum to the surrounding liquid and causes gross circulation in the bath which promotes mixing."

Jan 1, 1997

By W. K. Choi

Stainless steel exposed to wet environments at ambient temperature is subject to the formation of a surface biofilm. Depending upon the prevailing environmental conditions (dissolved oxygen, pH, Eh, concentration of cationic/anionic species), the biofilm may stimulate corrosion through formation of differential aeration zones and concentration cells. Corrosion significantly impacts the United States economy, since on a yearly basis, corrosion induced losses are estimated to be over $200 billion. A large portion of this corrosion is imputable to bacterial activity, and basic information is needed for a better understanding and control of the biocorrosion phenomenon. The present study has investigated the influence of Thiobacillus ferrooxidans in the corrosion of American Iron and Steel Institute (AISI) 304, 316 and 416 stainless steel samples. The formation of biofilm and microstructural changes on the surface of stainless steel samples and their weldments were assessed by microscopic examination, and the changes in the mechanical properties by stress-strain measurements. The significance of the results will be discussed.

Jan 1, 1993

By Michael A. Krstich

A soil washing pilot plant to treat soils at the U.S. Department of Energy (DOE) owned Fernald Environmental Management Project (FEMP), was designed based on extensive bench-scale testing. The system's design incorporated a combination of physical separation and' chemical extraction processes and was tested on two soils. The textural composition of the two soils was approximately 20 percent sand, 60 percent silt, and 20 percent clay. Since this grain size distribution was not considered optimum for physical separation techniques, thesoil washing pilot plant had to be designed with selected equipment to provide specific soil size fractions during processing operations. A trommel, vibrating screen deck, centrifuge, and attrition scrubber were used in the system to selectively separate specific soil size fractions at 4.75, 2, 0.3, and 0.02 millimeters (mm). The trammel used high pressure water [1000 pounds per square inch (psi)] during the initial step of the process to reduce soil aggregates to single grain composition, separate out greater than 4.75 mm gravel, and dislodge chemical contaminants from the individual soil particles. The vibrating double-screen deck provided 2 - 4.75 and 0.3 - 2 mm soil fractions that, when combined, averaged greater than 75 percent solids for both soils. The centrifuge was designed to take the less than 0.3 mm soil slurry from the screen deck and produce a particle size of 0.02 mm. The centrifuge produced a high solids stream that averaged greater than 70 percent solids for both soils. These 0.02 to 0.3 mm soil solids from the centrifuge were combined with the 0.3 to 4.75 mm soil solids from the screen deck and processed through the attrition scrubber. The data collected from the pilot-plant operation was used to aid in the design of a full-scale system and was instrumental in formulating full-scale process operations and the selection of equipment.

Jan 1, 1995

By Marc Liebman

We present the results of a telephone survey of electric arc furnace (EAF) steel producers. This report characterizes the current status of EAF dust generation, treatment and disposal. It indicates the quantity generated, zinc content, other relevant constituents, and plans and trends that will impact on the quantity and characteristics of the dust generated. The survey covers EAF based steel producers in the United States and Canada. It identifies the processors currently employed, opinions about the use of these processors and services, as well as new technologies being considered.

Jan 1, 2000

By Travis Knight

Mixed uranium and refractory metal carbide systems have been proposed for space nuclear power and propulsion applications. Solid-core space nuclear reactors could be utilized for low- earth-orbit (LEO) to geosynchronous-earth-orbit (GEO) transfers, manned missions to the moon or mars, and orbiter missions to the outer planets. However, these high performance space nuclear reactors present some challenging materials engineering requirements for operating in a high temperature, high radiation, and hot hydrogen environment. Since the RoverNERVA programs were concluded in 1973, significant advances in ultrahigh temperature materials technology have been made which can be applied to the development of an advanced solid-core nuclear fuel. Nuclear thermal propulsion (NTP) was first studied in the U.S. beginning in the mid-1950's during the RoverNERVA programs. During that time, about 20 rocket reactors were built and tested. More recently, Russian nuclear rocket reactor tests with pseudo-ternary carbide nuclear fuels (U, Zr, Nb)C and (U, Zr, Ta)C have been operated at temperatures as high as 3300 K for one hour. This study examined the processing parameters for fabricating the pseudo-ternary carbide, (U, Zr, Nb)C.

Jan 1, 1999

By Shadia J. Ikhmayies

SnO2:F/CdS:In bilayers were produced by the spray pyrolysis technique on glass substrates. The structures were characterized by recording and investigating their transmittance curves, I-V plots, X-ray difractograms (XRD) and by observing their scanning electron microscope (SEM) images. From the I-V plots it was found that the SnO2:F forms an ohmic or quasi-ohmic contact with CdS:In. XRD patterns show the polycrystalline nature of the films and show that there is a small shift in the position of the (200) line of SnO2:F without the appearance of new peaks. The morphology of the structures are compared with those of SnO2:F alone and CdS:In alone on glass substrates.

Jan 1, 2009

By Jogre A. S Tenório

he aim of the present investigation was to investigate technological features of the Fe-NbC dissolution in liquid Fe-C alloys. Fe-NbC is a Ferro-niobium alloy with 7%C, has a particle size smaller than 150 pm and its micro constituents are polygonal niobium carbides and an iron matrix. The obtained dissolution time was less than one-minute and the yields were in the range of 80-90% at 1873 K. In the Fe-NbC dissolution process, the dissolution occurs at first, and as a consequence the niobium carbides become free to dissolve. These carbides will dissolve until the melt reaches a saturation point. The non-dissolved carbides remain trapped in the liquid or will form a dross. The addition yields decreases when the niobium concentration reaches this limit value, that depends on the carbon concentration. These define a saturation curve.

Jan 1, 1994

By Hiroyuki Sano

A closed recycling process for the low-grade scrap of Al-based composite materials was developed. In this process flux treatment with water-soluble halide is a key technique. In the present work, flux treatment conditions were discussed from the viewpoint of the separation and the recovery of the base material, reinforcement and flux. Optimum separation condition was obtained for the NaCl-KCI-KF flux treatment. The recovered aluminum alloy can be recycled for various usages. The recovered SiC particles cannot be reused as reinforcement because of the coexistence of the contamination, therefore it is necessary to eliminate these contaminates or to find another use. The recovered flux is reusable with supplemental addition of fluoride.

Jan 1, 2003

By A. Elizabet Serna

The weak acid is a by product obtained in a pre-treatment of gases from a copper smelter prior to sulfuric acid manufacture and the main components of this weak acid are: sulfuric acid. copper, arsenic. antimony, bismuth and iron. Usually, this effluent is neutralized with lime and the solid residues are stored in a landfill as a hazardous waste. This work was directed at determining the optimal conditions to recover copper from weak acid using a cementation process before the neutralization of the effluent. The variables investigated are: Effluent temperature, iron scrap amount and acid concentration versus reaction time. The results of these experiments show that the cementation process of copper and the co-cementation of impurities such as arsenic, antimony and bismuth were in accord with the theory of the electrode potentials.

Jan 1, 1996

By C. M. F. Viera

In this work the properties of a clayey ceramic incorporated, up to 10 wt.%, with three types of wastes from a water treatment plant was evaluated. To determine the physical and mechanical properties such as linear shrinkage, water absorption and diametrical compression, specimens were prepared by 18 MPa uniaxial pressure and then fired in laboratory furnace at 700oC. The results indicated that the wastes incorporation changed the properties of the clayey ceramic. From the results it was found it possible to recycle these wastes into clayey ceramic in low amounts to avoid deleterious effect on the quality of the fired product.

Jan 1, 2008

By Zhang Libo, Li Wei, Peng Jinhui, Guo Shenghui, L. Jing

Partially stabilized zirconia ceramics (PSZ) were prepared by microwave sintering using natural baddeleyite which was obtained by flotation of baddeleyite ore as starting materials. Because of using natural baddeleyite as raw and the process producing no waste, it realized shorter process, energy savmg, environmentally-friendly and non-damage processing. In this work natural baddeleyite stabilized with 3.8wt.% CaO were sintered at 1300°C for 60min in a multi-mode 2.45GHz microwave furnace. Microwave sintering could fast heating and sintering. Besides that, microwave sintering could heat materials wholly, low the sintering temperature, improve the materials properties and save energy. X-ray spectrum displayed the product composed by the tetragonal phase and monoclinic phase that also showed the product was PSZ. Fine and uniform microstructures were observed in the product through scanning electron microscopy. PSZ which was with high density was confirmed by the method of the Archimedes technique.

Jan 1, 2011

By A. Dadgar

Extraction of gold and silver from two refractory concentrates using cyanide and bromine reagents was reported at the 12th International Precious Metal Conference (1). The objective of this paper is to present the gold extraction, recovery, and economics for two refractory concentrates using cyanide and bromine reagents. Gold extractions for cyanide leaching (24- 48 hours) and bromine leaching (6 hours) were the same and ranged from 94% to 96%. Gold recoveries from bromine pregnant solutions using carbon adsorption, ion exchange, solvent extraction, and zinc and aluminum precipitation methods, were better than 99.9%. A preliminary economic analysis indicates that chemical costs? for cyanidation and bromine process are $9.50 and $10.50, respectively per ton of calcine processed.

Jan 1, 1989

By Xiangru Chen, Qijie Zhai, Haicheng Li, Chao Yang, Zhang Wei

The Nb-rich phase generated by the addition of trace amounts of Nb(<0.1wt%) \ and the effects of different content of Nb on the morphology and distribution of graphite in ductile iron were studied in this paper. The results showed that when the content of niobium less than 0.1wt%, the two-dimensional morphology of Nb-rich phase existed in microalloyed ductile iron were mainly regular pattern such as square, triangle, polygon etc. Besides, Nb-rich phase in large size distributed in the matrix with a certain distance from graphite. With the increasing amount of niobium, the dispersion degree of graphite diameter, average diameter and roundness increased slightly, and the number of graphite decreased slightly.

Jan 1, 2015

By J. Alexandre

The use of bricks of soil-cement is proving to be an important constructive methodology due to low environmental impact in the production process of these blocks comparing with conventional bricks are burnt, besides being easy to produce. However during the process of production of bricks, which are compressed, knowledge of the properties of the soil used is critical to the quality and durability of the blocks. The objective of this work is to evaluate the feasibility of using soil from the municipality of Goytacazes for the production of soil-cement bricks. Assays were performed the compaction, liquid limit, plastic limit, particle size analysis, EDX and X-Ray diffraction for later pressed blocks and analyze their compressive strength and water absorption.

Jan 1, 2015

By Norihisa Iida, Yutaka Koshiba, Tsutoipu Masui

"Mitsubishi Materials has many years of experience in the production of oxygen free copper (OFC) and its alloys with a fully continuous-casting process. Four grades of OFC, commercial, electronic, superconductor, and ASTM class I are available according to user needs such as stabilizer for superconductivity, magnetron, and ultra-vacuum systems. Along with Cu-Ag and CuSn, we offer OFC based copper alloys such ·as Cu-Cr-Zr, Cu-Fe-P, Cu-Ni-Si and others, that are suitable for lead frame and connectors. Within the maximum sizes of 260mm X 1050mm for cakes and 385mm diameter for billets, we are very flexible and can adjust the ingot size to customer’s requirements. Other products that we can supply are semi-finished products such as hot rolled sheet, ·forged blank, extruded rod and finished products like mold for continuous casting of steel, ring mold for non-ferrous casting and backing plate for sputtering target.IntroductionMitsubishi Materials Corporation developed mass produced high quality oxygen free copper and. high copper alloy ingots in the 1960's. We produce 60,000 - 70,000 tons annually giving us 22 - 23% share of the world's market.Our oxygen free copper and. copper alloys are produced with a fully continuous casting process using only high-grade copper cathodes from our Naoshima and Onahama refineries. The raw material is melted and cast in' a carefully controlled atmosphere resulting in a product with low impurities and excellent properties.Using a controlled atmosphere it is possible to produce high quality copper alloys including active elements like chromium (Cr), zirconium (Zr), titanium (Ti), and magnesium (Mg) which are difficult to produce using standard batch casting methods.Using our own cakes and ·billets we produce and supply worldwide wrought materials like molds for ferrous and non-femous casting. These products receive special patented thermo-mechanical· treatments resulting in high strength and excellent conductivity with low cost."

Jan 1, 2000

By Peter G. Mason

Over the last 15 years numerous Pressure Oxidation and Pressure Leach plants have been installed throughout the world. The technology is no longer regarded with awe and trepidation as plants designed to treat a wide range of feedstocks continue to be successfully brought on line. Important aspects of the design of such plants include feed preparation, slurry pumping, heating and heat recovery, pressure control and let-down, vessel design, safety and provision of associated services.

Jan 1, 1999

By Yukio Ishikawa

Sumitomo Metal Mining Co,. Ltd. (SMM) has been producing 22,000 t/y of electrolytic nickel at Niihama by nickel matte electrorefining process since 1970. Although the matte electrorefining is an established process and the productivity has been greatly improved in the last 20 years, SMM has intensively developed the chloride process for the nickel production since 1970&apos;s. The nickel and cobalt refining process involving solvent extraction and electrowinning from the chloride solution has been successfully developed for the treatment of the mixed sulphide in 1975. The first application of chlorine leach to the anode slime has been succeeded since 1986. Based on those technology, the matte chlorine leach electrowinning process (MCLE) has been developed as an alternation to the relatively old technology of matte electrorefining. The new process offers significant cost down and excellent quality of the product. In 1986, the feasibility of MCLE was confirmed by the test work using the integlated pilot plant. The innovation of the chlorine leach process has been undertaken by this work. The new refining process can be divided into three stages including chlorine leach stage, purification stage and electrowinning stage. More than 99 % of nickel was extracted in atmospheric chlorine leach. Although copper ion was used for electron carrier in the chlorine leach, the excess copper from the feed matte is bled off from the leach circuit by de copperizing electrolysis. The copper ion of the pregnant solution is fixed on nickel matte by the cementation reaction. The nickel matte containing copper is processed in the chlorine leach. In the purification circuit, cobalt, iron and other impurities were removed from the nickel chloride solution. The nickel chloride solution is then fed into the electrowinning cell. Based on the process established, the new plant with a capacity of 330 t/M electrolytic nickel was commissioned in order to obtain the engineering data for design of the full scale plant in 1989. The performance of the plant was fully satisfied and the new process demonstrated the potential application of modern process control.

Jan 1, 1992

By Evgueni Jak

Recent advances in analytical, experimental techniques, and computer-based theoretical modelling of fundamental properties and elemental processes, provide new opportunities to develop the next level of whole-of-reactor pyrometallurgical furnace models. These models have the potential to significantly improve the prediction of, and adding value to, industrial operations. In non-ferrous smelting, the starting point of these models is the development of multicomponent thermodynamic databases for gas-slag-matte-speiss-metal-solids phases supported by systematic experimental research. The whole-of-reactor-models additionally should take into account kinetic processes taking place at micro- and macro- scales, and other key factors. Examples of applications of the latest research tools and modelling approaches to analysis of industrial flash and top submerged lance (TSL) sulphide smelting processes are presented. Different levels of industrial modelling are discussed from elemental local reactions, through general and more detailed whole-of-reactor-models, to plant sections and further to whole plant operation models. Some principles for development of pyrometallurgical reactor models are discussed.

By E. V. Verhoef

The proposed EU directive on the restriction of the use of certain hazardous substances in electrical and electronic equipment promotes the substitution of lead in consumer electronics to reduce emissions from lead in the end of life phase. In this paper, the consequences of substituting lead in solders is assessed using the Eco-lndicator-99 method for the examples. The base metal production system is considered as an interconnected network modeled dynamically in Simulink 4 and Matlab 6 (Mathworks Inc 2000), where the recovery and production of metal components of the assessed product partially overlap. This approach requires global modeling of metal production processes and mass balances and resulting allocation choices. It also reveals the susceptibility of LeA scores to different choices in the modeling and data availability and uncertainty. Besides the comparison between lead-free and lead-containing solders, other side effects are revealed. Lead is carrier material for the recycling and production of many co-elements in the interconnected production and recovery system. Substitution may have adverse effects such as temporary shortages of other connected metals that are often not considered in normal LeA assessments, thus leading to erroneous results. The suggested approach provides directions for including these external effects and for further assessment of the environmental effects of substituting lead. This paper shows that in order to assess the environmental aspects of metallurgy, dynamic modeling of the total system is required based on the fundamental thermodynamics in each metallurgical reactor, the basis of this dynamic model. With this the true environmental impact of metallurgy can be explained. In the case of lead free solder, it is shown that the mining of substitutes has a very much larger impact.

Jan 1, 2003

By JiaPeng Xu, Brian Lo, Uday B. Pal, Yihong Jiang, Soumendra N. Basu

"The Solid-Oxide Oxygen-Ion-Conducting Membrane (SOM) electrolysis process has been successfully tested on a laboratory scale, producing silicon directly from silica in a cost-effective and environmentally friendly way. A yttria-stabilized zirconia (YSZ) tube, closed at one end was employed to separate the molten salt containing dissolved silica from a liquid metal anode placed inside the YSZ tube. When the applied electric potential between the liquid tin cathode in the molten salt and the anode exceeds the dissociation potential of silica, oxygen ions are pumped out of the molten salt through the YSZ membrane and oxidized at the anode while the silicon cations in the flux are reduced to silicon at the liquid tin cathode. The presence of high-purity silicon crystals on the surface of liquid tin cathode was confirmed by scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS). Silicon crystals were extracted from tin cathode by chemical etching.IntroductionPhotovoltaics (PV) generate electrical power by using solar cells, and dramatically reduce the emissions of greenhouse gases (GHG). Through 2006 to 2011, it grew the fastest of all renewable technologies with operating capacity increasing an average of 58% annually [l]. However, the cost of manufacturing solar-grade silicon (SoG-Si) for high-efficiency solar energy production represents a major barrier to achieving the industrial goal for solar power of $1/Wp (watt at peak exposure) which would enable widespread grid parity. The current contract price of silicon to PV manufacturers is $50-$60/kg, with the spot market in 2007-2008 showing prices as high as $300/kg [2]. This makes the development of low cost and environmentally friendly manufacturing of high purity silicon very important."

Jan 1, 2013