Search Documents

By Gaifeng Xue, Lijun Lu, Honghui Fang, Jiannyang Hwang

"Steel slag has been stockpiled in many steel mills due to its poor performance in various construction related applications. Free lime in steel slag has been considered as a major barrier for its utilizations. Composite of steel slag and powders of granulated blast furnace slag have been found an excellent cementitious material for concrete. Portland cement is not required in this kind of concrete. Concretes with various amounts of steel slag and powders of granulated blast furnace slag additions have been investigated. Physical and chemical properties of the products were examined. High performance concrete can be obtained. Field testing of the concrete products was conducted for various applications, including buildings and pavements, and the results demonstrated the soundness of the concrete. Drill cores of field tested concrete, with ages up to 26 years, were examined for the microstructures under SEM.IntroductionIn the steel industry, a major source of the solid waste is steel slag. Steel slag has poor stability in construction applications. This is a major reason that only a small amount of steel slag has been utilized. Some of the reported applications include the land filling/creation in the sea, road base materials, soil treatment for acid neutralization and micronutrients supply, and sintering aid in the sintering plant of the steel industry [1].To solve the stability problem for using steel slag as construction materials, the common approach is to find a method capable of depressing or eliminating the expansion of steel slag. Free lime in steel slag is the major component that causes the expansion. Aging and hydration pretreatment of free lime in steel slag are the well known methods for increasing the steel slag stability. However, there has been limited success on these approaches due to that a large portion of free lime is locked in the grains during the pretreatment process."

Jan 1, 2012

By Markus A. Reuter, Robert Matusewicz

"Consumer products are a complex man-made mixture of sometimes in excess of 50 elements. In order to recover these complex mixtures of elements either as metals, compounds or energy requires versatile technology in physical separation but also smelting and energy recovery. This paper explores this by referring to the innovative application of Top Submerged Lance (TSL) technology and associated theoretical and environmental aspects to process (recycle) post consumer materials and industrial intermediate products and residues. A diversity of applications has been tested in Ausmelt’s pilot plant in Dandenong and many have gone to commercial scale globally. This paper reviews the varied applications ranging from e-waste recycling, lead and NiCd battery recycling, metals recovery from slags, zinc leach residue processing, electric arc furnace (EAF) dust, Municipal Waste Incinerator bottom ash processing, carbon containing residues such as retort ashes and spent pot liner from the aluminium production process as well as use of the technology for materials such as automotive shredder residue (ASR) and plastics. Introduction The modern resource cycle is a link between primary production of metals linked to the recycling of post-consumer goods. The sometimes complex combinations of materials and metals in consumer products such as televisions depicted by Figure 1, does require a range of technology to recover materials, metals and energy for reuse and/or recycling in an economically feasible as well as environmentally friendly manner."

Jan 1, 2008

By Axel Hoppe

Although Tantalum is not usually regarded as a precious metal, its pricing structure is very similar to that of Silver. Different from precious metals, Tantalum has only industrial applications and its use is about 1000 metric tons per year. The intrinsic value of Tantalum already in .the past was a driving force for its recycling. Based on these facts the Tantalum industry world-wide is approaching the closed-loop concept of its recycling. A detailed material flow of Tantalum processing as well as recovery of residues and used products will be discussed.

Jan 1, 1995

By Hong Yong Sohn, Miguel Olivas-Martinez, Zhixue Yuan

A novel flash ironmaking process that directly reduces iron oxide concentrate particles by gas is under development. The goal of this work was to study the possibility of reoxidation of iron particles in various gas mixtures. As the product iron cools down in the lower part of the flash reactor, conditions may become favorable for reoxidation because of equilibrium and high reactivity of iron particles. The effects of temperature (823 – 973 K) and H2O partial pressure (40 – 100 pct., Ptotal = 86.1 kPa) on the reoxidation rate were examined. The pressure dependence was first order with respect to water vapor, and the activation energy was 146 kJ/mol. A complete rate equation that adequately represents the experimental data was developed. For oxidation in O2-N2 mixtures, the effects of temperature (673 – 873 K) and O2 partial pressure (5 – 21 pct., Ptotal = 86.1 kPa) were determined. Reoxidation in pure CO2 was also investigated at 873 – 1073 K for comparison.

Jan 1, 2014

By Ho-Sang Sohn

The kinetic study on desulfurization of copper matte by gas bubbling was designed under the presumptions of lower FeO activity and of no slag formation, Copper matte with 59% Cu and 22.6% S in weight was oxidized at 1523K by bubbling of Ar + O2 gas through a submerged nozzle. The effects of oxygen partial pressure and flow rate of gas on the oxidation rate of matte were discussed. The desulfurization rate and the evolution rate of SO2 gas of copper matte were significantly influenced by the oxygen partial pressure, but the dependence on gas flow rate was rather complicated. The desulfurization rate and evolution rate of SO2 gas of copper matte were described by the mass transfer rate through the gas film around the rising gas bubbles. Thermodynamic correlation equations between the partial pressure of gaseous species and matte composition were incorporated to the kinetic calculation, The present model shows that the reaction path starts to transiently cross over an isobar line of PSO2 to asymptotically approach to the particular isobar line drawn in a matte composition plane of %S and %O.

Jan 1, 2003

By Evgenii Pavlov, Ivan Tronin, Viktor Timofeev, Vladimir Kislov, Sergei Bogovalov

"Modeling of the magnetohydrodynamical (MHD) and thermodynamical processes during the industrial scale Direct Chill (DC) casting of aluminum slabs is performed using a combination of ANSYS/CFX and ANSYS/EMAG software. The electromagnetic field is modeled through ANSYS/EMAG, while hydrodynamic and thermodynamic processes are modeled through ANSYS/CFX. Both packages were modified in order to calculate MHD flows in the liquid pool that forms during aluminum DC casting, and they were unified into a software combination that provides simultaneous simulation of all the above processes. The simulation shows that the electromagnetic stirring of the molten aluminum changes the shape of the solidification front (solid-liquid interface) very dramatically, namely it becomes significantly flatter. This effect should improve the internal structure of aluminum DC slabs and allows us to increase the casting velocity.IntroductionProduction of Aluminum alloys with high mechanical properties and structural uniformity is one of the main goals of industry. The preferred production method of aluminum alloys in most modern plants is Direct Chill (hereafter DC) casting because it offers high productivity and commercial success. One important limitation of this technology is the development of centerline shrinkage in slabs larger than about 1 meter. The improvement of the internal structure of long DC cast slabs can be achieved by electromagnetic stirring (hereafter ES) of the liquid metal above the solidification front. This intensifies heat transport in the zone close to the solidification front and suppresses shrinkage formation."

Jan 1, 2013

By Bryn Harris

Much has been written over the past twenty years on the removal and chemical stabilization of arsenic from metallurgical process solutions. This paper reviews again the latest developments in this field, and concludes as before that the high-iron arsenical ferrihydrites, together with the high temperature arsenic minerals, scorodite and Type II, remain as the best and most viable vehicles for industrial control and disposal. However, a cautionary note is introduced, in that chemical environments cannot be considered in isolation, and that cogniscence has to be taken of microbiological activity in determining the disposal method. Data are also presented on a survey of industrial practice, which shows that arsenical ferrihydrite is by far the most widely-practiced and accepted method used worldwide. Finally, the disaster in Bangladesh is briefly discussed with reference to lessons that the metallurgical community might learn from this.

Jan 1, 2003

By T. T. Chen

Canadian Electrolytic Zinc has developed the "cement-stabilization of jarosite residue" Garofix) process to stabilize zinc plant jarosite residues for disposal. The cement-jarosite mixtures cure quickly, have good mechanical strength and low hydraulic permeability; they possess good neutralizing capability and chemical stability. In the jarofix process, Portland cement partly decomposes jarosite to form (SO4MOH)12.nH2O, ferric hydroxide and an alkali sulphate. Approximately 40% of the jarosite reacts in mixtures containing 30% cement. The jarofix product also contains various Ca-Al-Fesilicate-sulphate-hydrate phases and gypsum, which bond the individual particles together imparting mechanical strength and reducing the permeability. Most of the reactions take place in the first few hours of curing. Ammonium jarosite is slightly more reactive than sodium jarosite but releases NH3 gas; water-soluble Zn in the jarosite residue is stabilized in the cement reaction products.

Jan 1, 1996

By Robert E. Moore

Synthetic spinel is proving to be a highly effective refractory for specific applications, but its cost limits applications. Formation of spinel from a raw material such as diaspore or bauxite could provide a suitable and less costly starting material. In the study reported here, finely ground (-325 mesh) diaspore from Missouri and bauxite from Guyana and China are combined with hardburned MgO (-325 mesh) in appropriate proportions to yield spinel and spinel with secondary phases. A classical sintering and creep study was completed, accompanied by a microstructure study to determine completeness of the reactions and morphologies of the reaction products.

Jan 1, 1991

By Michael Altepeter

Big River Zinc Corporation, located in Sauget, Illinois, operates a neutral leach residue circuit. The residue produced in the circuit is sold to lead smelters for subsequent recovery of valuable metals. A research program was initiated several years ago to find a means of treating the residue at Big River Zinc to recover the valuable metals. The Ausmelt submerged lance reactor was selected as the best alternative for the first step of the process. Pilot scale tests were conducted at Ausmelt's facilities in Melbourne, Australia. Separations were excellent. 99%+ of the Zn, Pb, Cd, and Ag contained in the residue reported to the oxide fume. 99%+ of the SiO2,, Fe, Mg, and Ca in the residue reported to the slag which passed the EPA TCLP test. Subsequent leaching of the oxide fumes and purification of the leach solutions using conventional procedures produced solUtions suitable for zinc electrowinning and an upgraded lead sulfate cake for sale.

Jan 1, 1992

By M. Wu, A. Kharicha, A. Ludwig

"The droplet formation during melting of a 400 mm diameter electrode is simulated with a multiphase-MHD approach. The computational model includes a layer of slag and a layer of liquid steel. A VOF approach is used for the interface tracking and a potential formulation is used for the electric and the magnetic field. The Lorentz force and the Joule heating are recalculated at each time step in function of the phase distribution. The first results provided by this model are presented.IntroductionThe Electro-Slag-Remelting (ESR) process is an advanced technology for the production of components of e.g. high quality steels [ 1-9]. An alternating current (Figure 1) is passed from a conventionally melted and cast solid electrode through a layer of molten slag to the baseplate. Because of the electrical resistivity of the slag, Joule heating is generated and the slag transfers this energy to ingot and mould surfaces and to the melting electrode tip. The molten metal produced in the form of droplets passes through the slag and feeds a liquid pool from where directional solidification takes place. The slag and the ingot are contained in a water cooled copper mould. As also the baseplate is water cooled, a heat flow regime is imposed that gives controlled solidification, and this results in improved structure characteristics of ESR ingots.This process involves two liquids, a liquid metal and a liquid slag. Each liquid is subject to a phase change due to melting and/or solidification. From a fluid dynamic point of view, the ESR process is clearly a multiphase process, with free interfaces (slag/pool, gas/slag), and with a mixed area (slag and falling steel droplets) [ 10-15].Physically, the development of the heat and mass transfer at the slag/droplet interface is important for the final ingot quality, composition and cleanliness. Visual observations of the droplet formation just under the electrode being melted is almost impossible. Due to the presence of high temperatures, opacity of the materials, and the presence of the mould it is not possible to directly observe the behaviour the slag/pool interface. Although usually assumed flat [1-9], a previous work [10] using a Volume of fluid (VOF) model has shown that the interface shape between a layer of slag and steel layer in a cylindrical cavity is highly coupled with the distribution of the electric current. A full scale simulation of the ESR process using a VOF model has shown that the shape of the pool interface is likely to be non flat."

Jan 1, 2011

By Yoichi Takeda

Copper solubility in SiO2-CaO-FeOx slag equilibrated with copper matte in 10% SO2 atmosphere at 1573K was estimated. Essential parameters are activity coefficients of copper oxide and sulfide, oxygen and sulfur potentials and activity of copper in the slag-matte system. A large number of experiments provide proper parameters to calculate copper solubility in slag, A classical thcrmodynamic model postulating CuO0.5 and CuS0.5 moleculcs assists in estimating copper solubility in slag. Additions of Si02 and CaO reduce copper solubility almost in any condition. Copper loss, that is function copper solubility and slag volume, in the silica saturated SiO2-FeO. binary slag is minimally equilibrated with less than 66% copper matte while copper loss in the 50% FeO.-SiO2-CaO ternary slag saturated with 2CaOSiO2 is minimally equilibrated with over 66% copper matte. This slag composition has potential for continuous copper converting, direct copper production or high-grade matte production.

Jan 1, 2003

By Zhengjie Chen, Wenhui Ma, Jijun Wu, Kuixian Wei

The gasification reactivity of PC (petroleum coke), strengthened by addition of different potassium carbonate proportions using different grinding medium, was investigated by using thermogravimetric analysis (TGA). Results showed that the gasification reactivity of PC not only increased with the increase of catalyst-loaded, but also showed the effective improvement by anhydrous alcohol. The PC was mixed with potassium carbonate [K2CO3] catalyst at 0.5%, 0.8%, 1.0% and 1.5%, and then ground wet with distilled water. The CO2-gasification rate of PC was only 77.35%, 80.55%, 84.07% and 85.88% under the gasification temperature 1100 °C and holding time 120 min, at different K2CO3 respectively. However, when the PC was ground in anhydrous alcohol at the same condition of catalyst-loading, the gasification rate of PC reached 95.43%, 96.63%, 95.50% and 95.61% at the holding time of 108 min, 101 min, 74 min and 35 min, respectively. It was shown by FTIR, SEM and EDX determinations that the anhydrous alcohol used as the grinding medium can further improve the gasification reactivity of PC when compared with the distilled water.

Jan 1, 2016

By A. R. G. Azevedo, G. C. Xavier

"The search for technological innovations in the Civil Construction takes as an objective the reduction of costs and increase of the productivity. However, these technologies demand analysis and studies of parameters of control that provide the quality of the products. With the intention of improve the knowledge on industrialized mortars used in mechanized projection machines, a characterization was done in the state anidro, fresh and hardening of three mortars, being each one of a State, Rio de Janeiro, Sao Paulo and Bahia. The tenors of water/ mortar was obtained through tests done in built environment, it varied from 0,17 to 0,26. From these results, the mortars were projected by his respective consistency, analyzing its compressive strength, and traction adherence resistance, in this way, the good performance of the revetments was provided.IntroductionThe market competitiveness of Construction has led companies to invest in construction processes and techniques in order to rationalize and optimize the buildings. Thus, changes emerged in coating system providing improvements in conventional materials and novel construction techniques, such as mortar industrialized and mechanized projection.Adopting projection equipment mortar is flagged as one of the solutions to reduce the interference of hand labor in construction, optimizing the performance of internal and external coatings, as well as streamline the production process and transportation, reducing lossesMaterials and deadline for execution of the casing(l)The process has been used due to its benefits, however, studies are necessary parameters for quality control of these mortars used in the projection to greater knowledge of mixing and market acceptance. It is therefore quite relevant information processing techniques available on the subject, as necessary to carry out research aiming at defining specific indicators of quality."

Jan 1, 2013

By Ari I. Kogut

Impurity minerals in fluorspar ores and concentrates from a deposit in Southern Africa have been studied by reflected light, transmitted light, and cathodoluminescence microscopy. The principal impurities are quartz, calcite, aegirine, apatite, ankerite, magnetite, goethite, and synchysite [Ca(La,Ce,Nd)(C03l2Fj. Cathodoluminescence microscopy was found to be very useful in studying the character of the fluorite and especially for recognizing the presence of apatite and calcite impurities. Fluorite exhibits blue, calcite shows yellow, and apatite has white, light purple, and pink cathodoluminescence. The cathodoluminescent character of apatite varies with its geological environment and position in the orebody. The results of this microscopic study show that phosphorus present in flUorite concentrates occurs principally in binary locked apatite-fluorite particles. Successive fluorite cleaner concentrates contain progressively smaller amounts of locked apatite-fluorite particles. Free apatite has been effectively partitioned to the final tailings.

Jan 1, 1995

By P. N. Anyalebechi

The effects of Si (0.19-0.52 wI. %), Fe (0.20 wI. %-0.44 wI. %), and Cr (0-0.10 wI.%) on the response of ingots of aluminum alloy 3004 solidified at different rates (O.IO°C/s to 30°C/s), to homogenization heat treatment have been investigated. Response to homogenization was determined by quantifying the following microstructural parameters: (i) amount of Mn retained in solid solution; (ii) types, relative amounts, sizes, size distributions, shapes, and chemical compositions of second phases; (iii) extent of the alpha-transformation (i.e., AI6(Fe,Mn) --7 (XAI12( Fe,MnhSi) reaction; (iv) dispersoid formation; and (v) alleviation of dendritic microsegregation. Of the three alloying elements investigated, Si had the greatest effect on the response of aluminum alloy 3004 to heat treatment. Increase in Si content, fineness of cast microstructure, and homogenization temperature facilitated alpha-transformation reaction, dissolution of Mg2Si, loss of Mn supersaturation, and formation of AldFe,Mn)3Si and Mg2Si dispersoids.

Jan 1, 2008

By James M. Fragomeni

"The mechanical behavior of an Al-Li alloy was studied and related to the extrusion processing parameters, the plastic metal flow during defonnation, the anisotropy, and the microstructure. The extrusion temperatures, strain rates, extrusion ratios, billet temperatures, and extrusion geometries were varied during processing and correlated with the microstructure and properties. The extrusion processing variables were related to the mechariicar behavior, anisotropy, and microstructure through the ZenerHollomon parameter i.e., the temperature compensated strain rate. Based on optical and electron microscopy studies it was found that regardless of the extrusion conditions, the various microstructures for the most part were unrecrystallized for both the as-extruded and the solution heat-treated conditions. Smaller grain sizes were correlated to larger Zener-Hollomon parameters. The extrusion temperature and ratio did not significantly affect the strength or ductility as did the section geometry, which had a large affect on these mechanical properties. The anisotropy of the properties varied substantially when comparing the extruded longitudinal versus transverse grain orientations.IntroductionThe extrusion process also has a substantial influence on: the microsfructure and mechanical properties of a material that is Athens, Ohio, 45701 fonned The plastic defonnation that occurs during the extrusion process alters the grain size, crystallographic texture, anisotropy, subgrain size, dislocation density and various other microstructural features. Often the material being extruded is not homogeneous, therefore variations in the microstructure and properties occur across the cross-section of the final extruded product. The mechanical properties and microstructure can also vary with length since it is hard to maintain a constant temperature throughout the extrusion process. The extrusion temperature often varies from the heat generated during the extrusion process. The demonstration material that was extruded for this .study was an aluminum alloy containing 2.6wt, % lithium and 0.09wt.% zirconium. This alloy was strengthened by heat treatment causing nucleation, growth, and coarsening of coherent metastable o' (Al3Li) precipitates in the microstructure. The ? precipitates which are a consequence 9f artificially aging the AlLi alloy, are spherical, ordered, and coherent with the aluminum matrix and impede the dislocation glide inotion during plastic defonnation. Theo particles grow homogeneously in the matrix, and have the Cu3Au (L 12)"" superlattice crystal structure. Aluminum-lithium alloys are used primarily for aerospace structural applications since they have attractive properties such as a lower density and higher elastic modulus than conventional 2XXX and 7XXX alloys."

Jan 1, 2000

By K. Fagerlund

Methods for simulation of settler reactions, matte-slag separation and matte settling in copper flash smelting have been examined. The reaction, separation and settling phenomena of slightly oxidized chalcopyrite samples and cuprous sulfide-magnetite mixtures in fayalite type slags were examined at about 1300°C under inert atmosphere. Two methods based on introduction of molten samples of oxidized chalcopyrite concentrates or synthetic matte-magnetite mixtures onto the surface of molten iron silicate slag were tested. In the first method the samples were water quenched and polished specimens were studied and analysed using light optical microscope, scanning electron microscope, energy dispersive spectrometer. In the second method processes taking place after the introduction of samples onto the slag are followed "in situ" using X-ray transmission image monitoring. Great differences were observed in separation and settling behaviour of low and high grade copper mattes produced as a results of interaction of initial samples and slag.

Jan 1, 1997

By Shinroku Matsuzaki

Data the measurement sensor installed with spatial distribution on the blast furnace were successively accumulated online from the process computer to the database system over a long period. This is a new system that accurately considers the relation with the installation position of each sensor, and picture computerization of the measurement data was developed. The overall operation state of a blast furnace, which skilled operators can see in their mind?s eye, was objectively visualized as pictorial information.

Jan 1, 2006

By Kimio Itagaki, Torn Matsumoto, Makoto Ohtsuka, Kentarou Harada

"The structure and hydrogen-absorption properties of LaNis thin films were investigated in the present study. LaNis thin films were prepared by a sputtering method with a radio-frequency power, Ws, of 50 -400 Wat substrate temperature, Ts, of323 -573 K. Nickel content of the films decreased with increasing Ws, however, there was no dependence on Ts. At low Ws and low Ts, amorphous films were deposited. In other conditions, the films were polycrystalline. The films prepared at high Ws and low Ts, or at low Ws and high Ts, exhibited only a (h k · 0) peak in the X-ray diffraction profiles. This indicates that the c-axis of crystalline films was oriented parallel to the substrate plane. At high Ws and high Ts, the films with columnar structure were obtained. Hydrogen-absorption capacity of the thin films increased with increasing Ws. The pressure plateau did not appear on the pressure-composition isotherms. The films deposited at high Ts represented a higher equilibrium pressure.IntroductionThin films of hydrogen storage alloys can be applied for an electrode of rechargeable battery or fuel cell, a filter for H1 purification and various kind of sensor. Some studies on the preparation of the thin films of LaNi5 intermetallic compound, which is a typical hydrogen storage material, have been done hitherto. Adachi et al. , 2) and Sakaguchi et al. 3) prepared amorphous and crystalline LaNi5 thin films using flash evaporation of alloy powders and measured the pressure-composition isotherm for the prepared film utilizing a quartz crystal mass monitoring (QC:MM) method. It was found that the prepared amorphous film absorbed hydrogen without disintegrating into the powders and the hydrogen-absorption capacity of the films increased with the degree of crystallinity. Sakai et al. 4) reported that the maximum hydrogen storage capacities of amorphous and crystalline LaNi5 thin films, fabricated by a RF sputtering method using combination targets, were about 40 mA h g-1 (LaNisHo.7) and 160 mA h g-1 (LaNi5H2.6), respectively. Uchida et al. 5, 6) prepared LaNi5 thin films using flash evaporation of alloy powders and measured volumetrically the pressure-composition isotherm for the prepared film. It was reported that the hydrogen-absorption capacity of the films changed by the annealing treatment."

Jan 1, 1998