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By Chai Li-yuan

The anodic behavior of AZ31 magnesium alloy in NaOH alkaline solution was investigated in this paper. The effects of anodizing parameters, such as applied current density, concentration of NaOH and temperature of the solution on the formation, structure and surface morphology of the anodic films were also studied. The formation of the anodic film was analyzed by analyzing the anodic polarization curves, the potential-time curves and XRD, SEM graphs of samples obtained at different anodizing time. The results of corrosion resistance tests, XRD and SEM observation showed that the temperature greatly affected the formation and anti-corrosion property of the anodic film, but the concentration of NaOH not. The film with best anti-corrosion resistance was obtained at applied current density of 10mA/cm2, 353k in 1mol/l NaOH solution.

Jan 1, 2006

By Pierre-François Bareel

EU legislation imposes ambitious recycling targets for various consumer goods. End-of-Life Vehicles (ELVs), scrap iron and various proportions of Waste Electrical and Electronic Equipment (WEEE) are processed by shredding plants which recover most of the metals but produce Shredder Residues (SR) which are landfilled. They represent 20 to 25 wt.% of the shredder input. Energy issues for the coarse fraction of SR are now largely studied. However, below 2 mm, the calorific value falls off drastically. These Fine Shredder Residues (FSR) represent up to 55 wt.% of the total SR. To meet European objectives other alternatives to landfilling must be considered for the FSR. The present paper describes a study carried out to characterise the FSR and investigates ways to process them and produce marketable products. Applying Gy's theory, a sampling procedure was conducted over two years to statistically quantify the variability of the physical and chemical properties of FSR produced by a Belgian post-shredding treatment plant. Macroscopic characterisation has led to the identification of four material categories which could be separated according to their physical properties: ferrous metals (more or less oxidised), non-ferrous metals, an organic fraction (plastics, rubber, textiles, foams, wood) and a minerals fraction (glass, ceramic, concrete). The entrainment of small metallic particles within the pores of organic fragments will affect the quality of the separations.

Jan 1, 2006

By Ahmad Umar

A variety of ZnO nanostructures such as sea-urchin-like structures composed of nanowires and nanorods, nanocombs, nano/micro spheres and cages, star-shaped ZnO nanostructures, flower-shaped nanostructures, needle-like nanostructures etc. have been synthesized applying two different fabrication techniques i.e. thermal evaporation and cyclic feeding chemical vapor deposition techniques at different reaction parameters such as reaction temperature, growth period, reactant concentrations, types of source material and substrates etc. It was observed from the experiments that the morphologies of the grown structures were highly influenced by the reaction parameters and fabrication techniques and specific morphology can be obtained at particular reaction parameters in a specific synthetic procedure. Extensive morphological investigations of the obtained products demonstrate that the grown structures are single crystalline and having a wurtzite hexagonal phase. Room-temperature photoluminescence spectra of all the deposited products exhibited good optical properties. Finally, the growth process of the fabricated structures were proposed and discussed in detail.

Jan 1, 2006

By Gretel Parker

In situ Raman spectroscopic investigations of copper iron sulfides in leach solutions have been undertaken. Coupling potentiodynamic techniques to Raman spectroscopy produces a powerful tool for studying mineral surface response to changing conditions, while ESEM and high-vacuum techniques provide complementary ex-situ information on surface structure and composition. Oxidative acid leaching of chalcopyrite at ambient temperature yielded a product with S-S bonds that were shifted from those seen with covellite, with little evidence of elemental sulfur formation. Leaching of chalcopyrite led to non-homogeneous product distribution. Raman spectroscopy was able to identify the products formed on the mineral surfacein situ while leaching was occurring. Raman mapping and imaging demonstrated a surface distribution of the products which can be related to composition and structure changes of the mineral surface. The surface formed on chalcopyrite after anodic oxidation at 0.570 V vs. Ag/AgCl in 0.1 mol dm-3 HCl undergoes laser-induced transformation.

Jan 1, 2003

By Jong-Oh Jo1

Thermodynamics of Ti, N and O in liquid iron was studied in order to establish a data base for the prediction of TiN and TiOx formation in liquid stainless steels containing various alloying elements including Cr, Ni and Si as a function of temperature. The interaction parameters of these elements on Ti and N were determined using the metal-nitride-gas equilibration technique. The TiN stability diagram for a commercial stainless steel grade was constructed from the measured thermodynamic parameters, and its validity was confirmed experimentally. The interaction parameters between Ti and O, and the equilibrium constants for Ti deoxidation reactions for the formation of Ti2O3 and Ti3O5 were also determined by the equilibration of the melts with those oxides identified by the XRD and the EPMA analyses.

Jan 1, 2006

By María Guadalupe Sánchez-Loredo

Silver from nitrate aqueous solutions was extracted by commercial organophosphorous extractants (tri-n-butylphosphate, Cyanex 471x, Cyanex 301 and Cyanex 302). Quantitative silver extraction was obtained using the Cyanex reagents. After loading, aqueous solutions of several reducing reagents were used to prepare fine silver powders by reductive stripping. Only both extractants Cyanex 471x and tri-n-butylphosphate (TBP) could be reductive stripped and regenerated by aqueous solutions of ascorbic acid, and Cyanex 471x was decomposed to the corresponding phosphine oxide by using sodium borohydride as reducing agent. Silver was recovered as fine particles, which were characterised by means of scanning electron microscopy (SEM). Micrographs showed that the powder size and morphology were directly affected by the composition of the applied organic phases and aqueous reducing media.

Jan 1, 2003

By Xiaojie Gao, Shufeng Yang, Jingshe Li, Chengsong Liu

In the blast furnace process, the dust entrained in the blast furnace gas enters into the down-comer, flows through the gravity dust separator (to eliminate coarse particles) and then is collected in a bag-house. The powder collected by the baghouse is called bag dust, while both fractions are called blast furnace dust whose main components are C and Fe. The dust also contains small amounts of nonferrous metals such as Zn and Pb, which have some value. Also, due to the small particle size and low density the dust is easily suspended in air and so can endanger human health. Therefore it is necessary to develop a process to both treat the dust to recover the metal values and to dispose of the residue – preferably by recycling to the blast furnace itself via the sinter strand. These objectives will result in good economic, environmental and social benefits [1].

Jan 1, 2014

By Laihua Wang, Peter Hayes, Hae-Geon Lee

"This paper introduces a new process for the efficient removal of dissolved gases and inclusions from liquid metals. This process involves the creation and dispersion of fine bubbles in molten metals by introducing inert or reactive gas into a region of turbulent flow. The highly turbulent metal flow splits the gas into fine bubbles and results in good mixing between the gas and molten metal phases. These conditions are ideal for contacting inclusions in the metal with the bubbles and subsequent flotation of the inclusions to the metal-slag interface where the inclusions are then absorbed by the covering slag layer. Dissolved gases, such as [H], [0], [N] in the metals are also transferred to the gas bubbles and removed from solution.The process concept has been previously demonstrated using a full-scale air/water model to simulate the ladle-to-tundish system of continuous casting of steel. The present cold modelling work has further demonstrated the ability of the process to remove gas solutes. The results indicate that the efficiency of new process is several hundred times greater than that of conventional high speed rotating injectors which are currently applied in the treatment of liquid light metals.IntroductionDuring metal smelting, refining and alloying processes, unwanted gas and second phase liquid or solid impurities are incorporated into liquid metals. In the case of steelmaking, the gas-forming impurities include [0], [H] and [N], and the solid impurities as a result of deoxidation include Ah03, Si02 inclusions. Common impurities in liquid aluminium are dissolved hydrogen and solid Ah03. To avoid subsequent problems during processing and to improve the physical properties of the metal products it is necessary to significantly reduce the level of impurities."

Jan 1, 1996

By Guozhu Ye

Hydrometallurgical zinc recovery from EAF dust has several advantages compared to pyrometallurgical alternatives in terms of low temperature operation, lower energy consumption and higher flexibility. Many hydrometallurgical processes have been suggested and tested over the years without success. The main reasons are: -Low leaching yield of zinc due to the fact that a high fraction of ZnO in the EAF dust exists in the zinc ferrite structure which makes selective leaching of ZnO not possible -Many of the proposals could not handle the halide in the EAF dust To eliminate these two disadvantages, two zinc ferrite elimination concepts have been tested and developed in the REZIN project of the EU 5th Framework Programme. The two concepts for zinc ferrite elimination could be shortly described by the following chemical reactions: A. ZnOFe2O3 + 2CaO = Ca2Fe2O5 + ZnOfree B. ZnOFe2O3 + C = Femet + CO/CO2 + ZnOfree These two concepts were investigated in details in combination with a subsequent leaching step using the novel EZINC process for recovery of zinc from EAF dust. Leaching of pretreated samples has shown great increases of a zinc recovery yield. A zinc recovery of over 90 % could be reached, as compared to about 50 % for no-pretreated samples. This paper will describe the two concepts in details.

Jan 1, 2006

New method for processing of copper and nickel production feed has been developed and tested at pilot unit having 10 t/hr capacity. The process allows single-stage treatment of ore feed including that with high magnesium oxide content and resulting in the production of rich matte, high-grade matte, or moralised alloy for further leaching, as well as dump slag and off-gasses suitable for production of elemental sulphur, liquid sulphur dioxide, or sulphuric acid. Tests results and principal technical and economical parameters are presented.

Jan 1, 2006

By Du Sichen

The present paper presents the modeling of gas-solid reactions in the case of the decomposition of CaCO3, describing the reaction kinetics on the basis of heat-transfer concepts which could be compared with thermogravimetric results. In the case of solid-solid reactions, the present paper describes the model developed for describing solid-solid reactions from dynamic X-ray diffraction technique, developed by the present team. The model has been successful in explaining the formation of spinel from MgO and Al2O3.

Jan 1, 2006

By Kai Tang, Casper van der Eijk

Natural gas has been used as reductant in the production of iron for several decades. Recently, the use of natural gas as reductant for other metals has been drawing attention because of the low price of natural gas, as well as the reduction of CO2 emissions compared to the use of coke and coal. In this work, the reduction of a mixture of Ti- and Ni-oxides by natural gas has been studied. Within the Ni-Ti system, the intermetallic compound Ni3Ti is thermodynamically the most stable one. Therefore, powders of Ni-oxide and Ti-oxides were mixed in an atomic ratio of three to one and subsequently pelletized. Reduction was performed in a TGA furnace at constant temperature with varying reducing gas atmospheres. In a natural gas containing atmosphere, the Ni-oxide was easily reduced to metallic nickel while the Ti was reduced to Ti-oxycarbides or Ti-oxynitride when nitrogen was present. Depending on the process parameters, several percent of Ti was dissolved in the nickel-based solid phase.

Jan 1, 2014

By Larry M. Southwick

Pneumatic converting (Bessemerizing) of iron revolutionized the steel industry. Bessemerizing of copper (conversion of copper sulfide matte to copper metal) was proposed at almost the same time, but it was slow in being accepted. The differences between iron and copper converting were great and technical problems were substantial. It took 25 years for the process to become viable and another 25 years before a truly economical solution was found. A major economical and productivity problem was the short life for converter refractory linings. The first converters had acid (silica) linings, which were quickly consumed since silica was a flux for the process. Converters had to be relined at least once per day, a laboriously expensive manual process with only the most rudimentary mechanical aids available to assist. The industry was revolutionized almost overnight when finally a viable basic (magnesite) lining was developed. This lasted 100's of days versus less than one, leading to converters that were easier to operate and which handled larger charges. This change occurred after W.H. Peirce and E.A.C. Smith, with support from the Guggenheim interests, successfully operated a basic lined converter in a copper refinery in Baltimore. While Peirce and Smith are generally given credit for the development and explosive acceptance of this idea, a Pittsburgh industrialist, Ralph M. Baggaley, working in an independent smelter in Butte, Montana, successfully built and operated a basic lined converter four years before they did. In fact, the early support for Peirce and Smith likely occurred because Guggenheim's staff were encouraged after thoroughly examining Baggaley on his earlier successes. The questions of technology primacy between Baggaley and Peirce/Smith are ironically similar to those between Wm. Kelly and Bessemer in converting iron to steel. This paper will review what Baggaley (and other early researchers) accomplished, examine why he (or they) did not receive credit equal to Peirce and Smith and explore what his (their) place should be in the development of successful basic linings. More suspects than a Victorian Whodunit.

Jan 1, 1999

By Mao Chen, Baojun Zhao, Zhixiang Cui, Leonel Contreras, Chuanbing Wei

Bottom blown oxygen copper smelting process developed at Dongying Fangyuan Nonferrous Metals shows many advantages such as flexible feed requirement, high productivity, low energy consumption and high direct copper recovery. However, the weak acid generated during the process is not stable which influences the waste management and continuous operation. The amount of the weak acid is determined by SO3 formed in copper smelting process. SO3 can be formed inside copper smelting furnace and boiler at different conditions. Effects of temperature and oxygen partial pressure on the formation of SO3 during copper smelting process have been discussed thermodynamically. Understanding of the mechanisms for SO3 formation will enable the operation of bottom blown copper smelting furnace to be optimized and generation of the weak acid in the process can be managed. The fundamentals developed in this study can also be applied to other copper smelting processes.

Jan 1, 2016

By W. C. Chang

Phases and magnetic evolutions of melt spun Nd9.5(Fe1-xCox)85.5B5 (x=0, 0.05, 0.1 and 0.15), (Nd1-yLay)9.5Fe85.5B5 (y=0, 0.0.5, 0.1; and 0.15) and (Nd0.95La0.05)9.5(Fe1-zCrz)81.5B9 (z=0, 0.033, 0.067 and 0.1) nanocomposites: have been investigated. It was found that a. dilute Co substitution for Fe, x=0:05-0:15, in Nd9.5(Fe1-xCox) 85.5B5 improved not only Curie temperature but also the remanence and maximum energy product. Partial substitution of La for Nd in(Nd1-yLay)9.5Fe85.5B5 may suppress the grain growth of the materials during thermal treatment. Exchange coupling between the Nd2Fe14B and a-Fe was found: to increase with increasing La content. A dilute La-substitution, y=O. 10, has proven to decrease the optimum wheel speed required for preparing melt spun ribbons with better magnetic properties; Furthermore; a slight substitution of La for Nd in (Nd0.95La0.05)9.5(Fe1-xCrx)81.5B9 nanocomposite reduced the crystallization temperature of the over-quenched ribbons and led to the formation of a multiple phases mixture. Nevertheless, a dilute Cr addition increases the Tg of (Nd0.95La0.05)9.5(Fe1zCrz)81.5B9 and also suppresses the formation of the undesired (Nd,La)2Fe23B3 and Fe3B phases: Cr was found to play an important role in grain smoothening or magnetic separation which consequently increased the Hc of Cr-containing materials.

Jan 1, 1997

By Dai Xi

In the present work, the viscosities of molten FenO-MgO-SiO2 and FenO-MgO-CaO-SiO2 semi-synthetic slags for nickel flash smelting were measured in the temperature range from 1473 to 1723K by a rotational viscometer. The ratio of Fe to Si02 was fixed at 1.2, calcium and magnesium oxide contents varied in the range from 2 to 8 mass% and 9 to 12 mass%, respectively. The results showed that silicate anions became smaller by increasing CaO content, which results in a decrease of the viscosity of the slag. In the case of MgO addition the viscosity behavior was complicated. At MgO content below II mass%, the viscosity increased with the increase of MgO at all temperatures tested. However, when the MgO content was above II mass%, the viscosity decreased slightly for FenO-MgO-CaO-SiO2 system. At higher MgO contents, low-viscosity slags can be obtained by adding CaO. At a given composition, .the viscosity decreased with increasing temperature. The higher the temperature, the more MgO can be added before saturation. The effect of Fe3O4 on the viscosity was quite significant. The viscosity of slag increased by 300mPa-s at 1573K when Fe3O4 content varied from 3 to 9 mass%. The viscosity values are presented as the functions of temperature and composition. A comparison between FenO-MgO-SiO2 and FenO-MgO-CaO-SiO2 systems is given in this study.

Jan 1, 2003

By W. G. Davenport

Most pre-t 988 Outokumpu flash furnaces were built with blast heaters. Many continue to use them. Blast temperatures in these smelters· are typically 400 to 700 K (Table 2. 1) This chapter: (a) shows how hot blast is included in our calculations (b) evaluates the effects orhot blast onauthothermal65% Cu matte production.

Jan 1, 2001

By Gregor Mori

Niobium electrolysis has been performed in a NaCl-KCl-NaF-NbCls electrolyte. By means of electrolytic .refining the average valency of the niobium ions was determined as well as the crystallization behaviour. In electrowinning runs the influence of the main parameters such as temperature, RF (mole ratio F/Nb), chemical prereduction, niobium content of the melt and current density has been determined with respect to low specific energy consumption and high purity of the deposit.

Jan 1, 1995

By Bart Blanpain, Tom Peter Jones, Muxing Guo, Liugang Chen, Huayue Shi

Fayalite based slag is formed during the smelting process of secondary copper resources. It was found that with the presence of high ZnO, the slag became viscous, causing a slag tapping problem. In the present paper, the phase relations of the slag system ZnO-“FeO”-SiO2-Al2O3- CaO (ZnO = 0-12 wt%, Al2O3% = 0-15 wt%, CaO = 0-1.5 wt%, with iron saturation) at 1150 °C is studied by using quenching technique followed by phase identification and compositional analysis of equilibrated samples. The dependence of FeO and Al2O3 solubility in the liquid slag on the chemical composition of slag is characterized. Based on the experimental data, the solid fraction of the slag, which may considerably, influences the slag viscosity, at the tapping temperature can be reasonably estimated and, therefore an appropriate modification of the slag composition can be made.

Jan 1, 2016

By C. Dresen

This paper discussed the reaction kinetics of the reduction of industrial phosphate pellets for P4 production. In the reduction process of various phosphate ores, the following parameters were investigated: Diffusion of the phosphorus oxide and other gaseous products from the reaction mixture after having been reduced on the reductant (coke) surface. Influence of silica on reaction kinetics. Temperature influence. Influence of mineralogy and morphology (different ores). Particle size influence of silica and coke. Experiments were carried out in a vertical tube furnace with 2 ores, 2 types of silica and one type of coke. Selected experimental conditions simulated furnace conditions. The following conclusions could be made: Reaction rate increases with the addition of SiO2 into the pellet. The reaction rate increases above 1350°C (melting temperature of the slag). Mixing different ore types in the pellets leads to differences in reduction kinetics. Particle size of the coke particles influence reduction kinetics. The amount of slag formation is influenced by silica addition, coke size and temperature.

Jan 1, 2002