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By Yongfeng Jia

Lime neutralization and co-precipitation of As(V) with iron(III) is the most widely used and most economical method for the removal of arsenic from mineral processing solutions and effluents. However, the arsenate fixation mechanism in the coprecipitated solids is not fully understood. It was suggested by various researchers to be a ferrihydrite precipitation process during which arsenate is removed by adsorption on ferrihydrite. In this study, XRD, EXAFS and microprobe were employed for the speciation of arsenic and the effect of various factors on arsenic solubility was also investigated. The results indicate that coprecipitation is a more complicated process than simple adsorption resulting in lower arsenic solubilities. Poorly crystalline ferric arsenate was observed for the first time to be present in the coprecipitated solids. In case of lime as base, there exists some type of Ca-Fe-arsenate association. A general term ?coprecipitate? is suggested to describe the precipitated arsenic-bearing solids instead of those widely used specific terms ?arsenical ferrihydrite? or ?arsenic-bearing ferrihydrite?.

Jan 1, 2005

By R. Hamar, G. Lamanthe

"To realize complex shaped pieces, like turbine blades, superalloys are cast with the lost-wax process. The end properties of these parts depend upon their microstructure as well as upon the occurence of casting defects such as micropores and hot tears. Such features are governed by the local solidification conditions which may be describe by the calculation of thermal transfers between alloy and mould. It needs the evaluation of numerous parameters which are fitted from experimental measurements in real castings. In further simulations, any parameter may be changed, in order to determine its influence. Such a single modification is quite impossible to realize in real castings, which shows that numerical modeling is a very good way to study casting processes.This modeling technique of casting is applied here to the real study of a typical low pressure turbine blade of a civil engine.IntroductionAircraft engine manufacturers use superalloys to produce turbine blades. They have to obtain a given microstructure and to avoid solidification defects to give good mechanical properties to theirs castings. For example, microporosity is induced by a large shrinkage that cannot be completely fed with the remaining liquid alloy .The optimization of casting processes needs a good Knowledge of the solidification process, that must be controlled at every place in the casting, and at every time of its freezing. Material and heat transfers that occur during the solidification, can be estimated from rather complex calculations. To model these physical phenomena, the evaluation of many parameters must be made. In this aim, some casting experiments are fitted with numerous thermal captors. The identification of experimental and computed thermograms let us estimate these parameters.A long-range scientific cooperation between SNECMA and INPG has enabled the realization of such studies on this topic. From all of them, this paper describes an experimental and computed investigation which has been led on a typical low pressure turbine blade of a civil engine."

Jan 1, 1986

By Kazuhiro Asai

Nippon Mining and Metals Company has an annual indium production capacity of 30 tons at its Saganoseki smelter and refinery. Lately, indium content in the. zinc smelting dust, one of the main sources, has been on the decrease while the amount of impurity in it on the increase. The present process at Saganoseki does not permit efficient elimination of a large. amount of impurity. Therefore, studies were conducted to improve its recovery process. As a result, a new indium recovery process consisting of leaching, solvent extraction and electrowinning has been developed. The new process was tested at a pilot plant and satisfactory results were obtained. This new process is discussed in this paper.

Jan 1, 1995

By Chao Du, Xiaohui Ning, Hongmin Zhu, Qiuyu Wang, Shuqiang Jiao

"TiCxOl-x solid solutions were synthesized by sintering a mixture of titanium carbide and titanium monoxide at 1600 °C. The corresponding structures and morphologies of the TiCxOl-x solid solutions were characterized by XRD and SEM. A series of tests has been performed on the electrochemical dissolution behavior of TiCxOl-x solid solutions in NaCl-KCl molten salt. The influences of synthesis time and electrokinetic parameters on the anodic dissolution behavior were also investigated. The results showed that TiCxOl-x solid solutions can dissolve as Tin+ into alkali chloride melt. Titanium ion species dissolved from TiCxOl-x solid solutions changes between Ti2+ and Ti3+ depending on the applied potential. The tail gas on the anode was monitored by a mass spectrometer. It was found the synthesis time significantly affects the components of the anodic gas.IntroductionTitanium and titanium alloys have been desired greatly because of their many uses. The critical factor that restricts the range of uses for Ti is its high cost of extraction. The primary titanium metal, sponge titanium, is still produced industrially worldwide by a process invented by Dr. Kroll in the 1940s[1] •Since the early 1970s, the research focus of the titanium industry has been directed towards developing a continuous process to produce high purity titanium at low cost. [2-10] Of the many alternative methods that have previously been investigated, the electrolytic process has been considered a promising method for titanium metallurgy [4-10]. Recently, several electrolysis and related methods such as the PFC-Cambridge process[11-15], calciothermic reduction[16-18], USTB [19,20] and MER[21] process were extensively investigated.The USTB process is a new approach where the pure titanium can be directly obtained by the electrolysis with an anode of titanium oxycarbide in molten salts[19, 20]. The titanium oxycarbide was produced by carbothermal reduction of titanium dioxide under vacuum at a temperature"

Jan 1, 2011

By Varadarajan Seshadri

The performance of mould fluxes in satisfying its quality requirements can have a significant effect on the efficiency of the continuous casting process and on the surface quality of the products. This performance is affected by various parameters including the characteristics of the mould fluxes, the quality of the steel being cast and the operational conditions of the caster. The extremely complex relationships involving the parameters mentioned above make it very difficult to have simple criteria for selecting mould fluxes for casting a certain grade of steel in a continuous casting machine. These difficulties led steelmakers and mould flux suppliers to select mould fluxes based mainly on plant trials. In the present work, a software to help in the analysis and development of mould fluxes for continuous casting was developed_ This software includes several models for prediction of mould flux viscosity and consumption. A mathematical model was also used to predict the heat flux through the mould flux. The proposed methodology was applied to continuous casting of crack sensitive steels_ Some of the results given by this software are presented, discussed and compared to plant data.

Jan 1, 2003

By Z. Jing, L. Qihou, C. Jun, L. Hui, Z. Yumeng

Three phases of Bi2O3 were first synthesized by extraction-stripping precipitation and post decomposition from BiCl3 leaching solution. The as-prepared Bi2O3 were characterized by X-ray powder diffraction (XRD), Fourier transform infrared spectra (FT-IR), scanning and transmission electron microscopy (SEM, TEM), UV-vis diffuse reflectance spectroscopy (UV-vis DRS), Brunauer-Emmett-Teller (BET) and X-ray photoelectron spectroscopy (XPS). The photocatalytic performances of the oxides were investigated by decomposing rhodamine B (RB) under visible irradiation. It shows that the Bi2O3 with different crystal structures and morphology were obtained under different decomposition temperature. The band gaps of as-prepared samples were 2.36, 2.41, and 2.78 eV for b-Bi2O3, a-Bi2O3, and d-Bi2O3, respectively, and the photocatalytic activities followed the order: b-Bi2O3 > a-Bi2O3 > d-Bi2O3, which was in good accordance with the photoluminescence spectra measurement results. The b-Bi2O3 exhibited the best photocatalytic performance which can effectively degrade 99.23% RB within 240 min.

Mar 1, 2018

By N. J. Themelis

In the last two decades, the Outokumpu flash smelting process has become the dominant new technology for copper smelting and has? also been applied to the smelting of other metal sulfides. The application of oxygen enrichment and improvements in concentrate burner and furnace design have resulted in ever increasing smelting rates per unit volume of the reaction shaft. This paper examines the. rate phenomena taking place in the reaction shaft of the Outokumpu furnace and compares information obtained from a mathematical model of heat and mass transfer rates to results obtained in pi1ot tests conducted at Pori, Finland, and to actual performance of a number of flash smelters around the world. 2?

Jan 1, 1985

By Feng Gao

A general unsteady- state model, based on a cracked substrate, has been developed to account for reaction and diffusion within porous substrate during oxidation of Carbon Fiber Reinforced Carbon matrix (CIC) composites. The effects of several parameters, such as diffusion and reaction rate ratio, oxygen concentration, and composite density, on oxidation process are explored. Also, theoretical results for a set of parameter values of the CIC composites are compared with experimental data. It shows that the model predicted values agreed well with the experimental data in weight loss. Based on this model, quantitative predictions of oxidation of a composite with cracked substrate can be made.

Jan 1, 1993

By S. Mondon

Hibi Smelter which is a Copper Smelter lining a blast furnace, produces 2,700 metric tons of anode copper per month. Generally, in a copper refinery, arsenic and antimony are considerably troublesome impurities. With regard to the elimination of antimony, Hibi Smelter has two handicaps described as follows. (1) Smelting under the slightly oxidizing atmosphere in the blast furnace. (2) Recycling the converter slag to the blast furnace after cooling. Therefore antimony and arsenic, mainly antimony, elimination tests, in which the alkaline flux was injected through the two tuyeres in the blowing stage, were carried out in the rotary anode furnace. Antimony and arsenic were respectively removed more than 90 96 from the molten copper, and their high eliminations are discussed by application of the transitory and permanent reaction model with the flux injection, which was presented by T. Lehner.

Jan 1, 1983

By C. D. Seybert, J. W. Evans

"The elimination of convection is essential in experimental investigations of diffusive transport (of heat and matter) during solidification. This paper describes an investigation of an approach whereby a magnetic field gradient is applied to a electrically non-conducting diamagnetic liquid. A magnetic body force then arises which is dependent on the volume susceptibility of the liquid and thereby on the density. With the field gradient aligned vertically and of correct magnitude, the variation of gravitational body forces due to density variations (arising from temperature variations, for example) can be counterbalanced by a variation in magnetic body force.Preparatory to a study of convection control in diamagnetic liquids, PN measurements have been made of the convection occurring during the solidification of water. A peculiar flow arises because of the density maximum at 4°C. Modeling of the flow the steady-state solidification of water in an extremely high field magnet at the NHMFL indicates that flow can be significantly reduced, but it is suggested that, due to field gradient variations within the cell, flow cannot be completely halted. INTRODUCTIONNatural convection is inherently a part of terrestrial solidification. Density-based convection during solidification, due to gradients of temperature and/or concentration, has a significant effect on a material's properties. The design of products with specific material characteristics has required the development of many processes to control convection (such as in the growth of semiconductor crystals, and electromagnetic stirring in steel casting). The expansion of fundamental knowledge about the process of solidification requires collecting data in the absence of density-based convection, while most of science's solidification data (and thus the equations that science has fitted to those data) have been obtained under the influence of gravity. Only relatively recently, through clever experimental design (e.g., drop towers, high altitude parabolic flights, and space laboratories), have investigators been able to study solidification in an environment with ""micro-gravity""."

Jan 1, 2001

By G. Djambazov, V. Bojarevics, K. Pericleous

The AC electromagnetic (EM) field effects are investigated for the possibility to extract particles (impurities, precipitates, oxides, bubbles, etc.) from molten silicon during the directional solidification of silicon ingot. The dynamics of particles are affected by the hydrodynamic drag, buoyancy, turbulent fluctuations and the EM force via the local pressure distribution. The EM force leads to high mixing rates, transitional flow structures and turbulence of the melt, contributing to the particle dispersion, transport and separation to a desired location. Application to silicon kerf loss recycling by melting and solidifying in the presence of AC EM field is presented for a variety of cases using 3D models for general flow structure and axisymmetric models for moving solidification front long time tracking. This paper demonstrates the effects of flow on the time dependent particle ‘swarm’ transport and the eventual modified distribution in the final ingot.

Mar 1, 2017

By K. Adham, T. Buchholz

Debottlenecking of high temperature processes within an existing metallurgical plant can significantly increase the throughput to meet new production demands. Modeling and simulation can help to fulfil that aim through incremental changes and operational improvements, rather than the more expensive option of building new plants and facing new environmental and infrastructure challenges. This paper describes a methodology of how modeling tools can be used to simulate the processing steps, how to estimate their existing and ultimate capacities, and how to determine the minimum cost points for a plant capacity expansion. This technique is presented through a generic description that can be applied to different metallurgical processing studies. We start with heat-and-mass balances, draw a bottleneck diagram, brainstorm capacity increase options, and prepare a cost-capacity curve. Hatch has successfully applied this technique to a number of plant capacity studies, with great benefits to our industrial clients (Adhametal et al. in A Success Path from Process R&D to Commercial Plants, Montreal, Canada, [1]).

Mar 1, 2017

By Patrick R. Taylor

This investigation studied the inflight calcination kinetics of nuclear waste simulant using a thermal plasma reactor. A series of experiments were performed to determine the conversion of insoluble aluminum compounds to the soluble compounds and the decomposition of complex organic and nitrite compounds present in the simulant waste. Thermodynamic calculations based on free energy minimization were performed to establish a theoretical basis for this investigation. A kinetic model to describe the conversion of gibsite to sodium aluminate has been proposed. The products of the calcination were characterized using XRD, Gas Chromatography, and chemical analysis by ICP. The results of this investigation indicated 85% gibsite conversion to sodium aluminate, 90% of nitrate decomposition, 52% TOC decomposition and 90% conversion of chromium to soluble compounds. A process is identified for inflight calcination of wastes. Key words: Plasma, waste, simulant, calcination

Jan 1, 1996

By R. H. Crist

Reactive components of algal cell walls include uronic and alginic acids: In addition, many marine species have half ester sulfate groups which function as fixed anions. Associated metals vary with the media, eg., Ca and Mg in fresh water (FV) and Na, Ca, Mg in seawater. . These metals readily exchange with aqueous phase protons or metal cations. A plot of the total amount of metal cations displaced by protons vs .. pH shows one inflection at pH 4 for FV algae and' in addition a second inflection at pH 2, 3 for marine algae. The first inflection is interpreted as. Indicating the cations associated with carboxyl groups ,and the ,second with half ester ?Sulfate groups. The exchange capacities of various aigal ,species vary widely. When FV algae is placed in a Pb2+ solution,- the amount of Pb2"' deposited on the algae is. Equivalent to the. Total Ca2?, Mg2, and H+ displaced? thereby confirming the ion exchange mechanism. Ion exchange equilibrium constants are reported for the displacement of ca2+ from Vaucheria. With Mg2+, sr2+, Cd2+, Pb2+_ and Na+ as well as the reverse reactions. Cd2+ can .be removed partially from algae by precipitating it as CdS or Cd(OH) 2 Pb2+ and Cu2+ are also partially removed as the hydroxides. Rates of reaction for various alkali hydroxides decrease with increasing .unhydrated cation radius. It is concluded that theory is useful in predicting viable applications for algae in pollution abatement.

Jan 1, 1991

By H. H. Kellogg

The thermochemical properties of molten solutions in the binaries Cu-Bi, Cu-Sb and Bi-Sb, as well as the ternary Cu-Bi-Sb, have been correlated and described in mathematical form by use of the associated species concept combined with the three-suffix Margules equations to account for the non-idea 1 behavior of the solution species. Agreement of the correlations with experimental data is excellent (relative deviation of less than 2.5% in the values of the activity coefficients) in most cases. The correlations are applicable over the entire composition range of each system, and in the temperature range 700°-1250°C.

Jan 1, 1985

By L. Béjar-Gómez

The aim of this research work is to study and characterize precipitates in structural microalloyed steel by transmission electron microscopy and analysis by high resolution (HRTEM). Microalloyed steel with titanium was produced by casting in an electrical induction oven of 25 Kg. capacity. Carbon content in steel was less than 0.1 % and titanium content of 0.04%. Steel was processed thermomechanically; reheated to 1250ºC and hot rolled on a laboratory mill to a 13.0 mm thick plate with a finish rolling temperature of 900ºC and thickness reduction of 80%. Analysis by High Resolution Transmission Electron Microscopy (HRTEM) identified precipitates in the steel; type and morphology. Energy Dispersive Spectroscopy (EDS) analysis was applied to obtain the chemical composition of precipitates and the matrix. STEM-EDS analysis was also applied to obtain the element profile of precipitates. The results showed the presence of carbonitride precipitates of titanium, Ti (CN), with a circular morphology and size of 10 nm and less.

Jan 1, 2006

This symposium is dedicated to the lifetime achievements of Professor H.Y. Sohn. It covers the scientific fields, processing routes and investigation techniques in which Prof. Sohn has worked during his career and is based in the equally important three topical areas: Principles, Technologies, and Industrial practice. Professor Sohn was General Chair of the very first TMS Fall Extraction and Processing Symposium in 1983 in San Francisco which led to the Annual such symposia as this International symposium. Furthermore, the theme of that symposium was sulfide smelting, which is also included in this symposium. [ ] Professor Sohn was born in a beautiful dynastic capital Kaesung, Korea on August 21, 1941. He received his B.S. degree in 1962 from Seoul National University, M.Sc. in 1966 from the University of New Brunswick, Fredericton, N.B., Canada, and his Ph.D. degree in 1970 from theUniversity of California at Berkeley all in Chemical Engineering. After working as a Research Associate at the State University of New York at Buffalo and as a Research Engineer at Du Pont?s Engineering Technology Laboratory, Dr. Sohn joined the Department of Metallurgical Engineering at the University of Utah in 1974 and currently holds the ranks of Professor of Metallurgical Engineering and Adjunct Professor of Chemical Engineering.

Jan 1, 2006

By Gjergj Dodbiba, Toyohisa Fujita, Takahiro Kikuchi, I-Chen Wu

"In order to separate molybdenum (Mo) from the high-level radioactive liquid waste (HLLW), Pb-Fe based adsorbents were synthesized. The adsorbents were precipitated by adding sodium hydroxide in mixture of 1 mol/L lead nitrate and 1 mol/L ferric nitrate aqueous solutions. Each precipitate was then filtered, dried and ground to obtain a fine powder, which has been used as an adsorbent. Two main parameters were considered when synthesizing the adsorbents, i.e. the pH value at precipitation of adsorbent precursor and the calcination temperature of Pb-Fe based adsorbent. Moreover, the structures of the synthesized adsorbents were investigated by means of an X-ray diffractometer.The experimental results indicated that the calcination temperature of the Pb-Fe based adsorbent has a great influence on adsorption capacity of the adsorbent for Mo. It was found that when the Pb-Fe based adsorbent was calcinated at 500 oC, the sorbed concentration of Mo was the highest.1. IntroductionThe high-level radioactive liquid waste (HLLW), arising from the reprocessing of nuclear fuel are generally immobilized in an alkali borosilicate glass matrix. Broadly speaking, alkali borosilicate glasses are the matrix of choice for the immobilization of the HLLW, since they permit vitrification of waste stream of variable composition, [1]. Within this frame, the incorporation of molybdenum (Mo) is of particular interest in the vitrification of HLLW. Molybdenum is know to have a low solubility in borosilicate glass compositions and its presence in excess results in the phase separation of a complex yellow molten salt during vitrification, [1]. The formation of so-called “yellow phase” material during the vitrification process is undesirable since it leads to the accelerated corrosion of the inconel crucible liners. Furthermore, the “yellow phase”, which is reported to contain also other fission products, is soluble in aqueous solution providing a potential route for the leaching of radionuclides from the vitrified waste, should it come into contact with water, [1]."

Jan 1, 2008

By Serdar Aksu, Fiona M. Doyle

"CMP will be an essential process in the production of integrated circuits containing copper interconnects. This study aims to improve our mechanistic understanding of the role that organic chelating agents might play in the reactive slurries used in copper CMP. Copper dissolution behavior in EDTA arid glycine was first examined by producing potential-pH diagrams for the copper-water-EDTA and copper-water-glycine 'systems. The results of potentiodynamic polarization experiments were then considered in light of these diagrams. . In-situ polarization experiments were conducted to gain insight into the electrochemistry of copper during dynamic polishing in slurries prepared from EDT A and glycine.IntroductionCopper has recently started to replace aluminum as the interconnect metal in integrated circuits. Copper interconnection offers faster and more reliable integrated circuits due to its higher electrical conductivity and superior electromigration resistance (1). The damascene method is used to form multilevel interconnects in the manufacture of integrated circuit devices with copper metallization (2, 3). Copper is deposited by CVD or electroplating into vias and trenches etched in the interlayer dielectric (IDL), over a diffusion barrier usually made from titanium, tantalum or their nitrides. Chemical mechanical planarization (CMP) then prepares the wafer for the next deposition step, by removing excess copper and planarizing the surface. During CMP, the wafer is rotated and pressed against a rotating platen covered with a polishing pad. Chemically active slurries containing submicron size abrasive particles (Si02, Al20 3, ceria, diamond, etc.) are applied. Both the mechanical action of the abrasive particles and the chemical action of slurry constituents remove material from the wafer surface. Planarization results because material is removed faster from protruding regions on the surface than from recessed regions. Since CMP can globally planarize .the entire wafer, it has become one of the key technologies for producing integrated circuits with copper metallization."

Jan 1, 2000

By A. A. Hejja

The first part of this study deals with the importance of surface tension of slags produced in the smelting of sulphide concentrates. Theoretically the method of determining the surface tension of slags was laid down by Boni and Derge. The values obtained experimentally for a series of main oxide components were grouped into a useful correlation incorporating experimental constants for the relevant oxides present in the slag, some of these giving the surface tension value for the particular slag. These estimated values were coupled with or incorporated into the slag viscosity plots to show the correlation between the two factors. This is also important from a refractory attack point of view in the furnace operation. In the second part an attempt is made toward the optimisation of slag composition relevant for electric furnace smelting processes. Using the knowledge of the viscosity and electrical conductivity of the slags at the temperature of furnace operation, the mode of optimisation is based on correlations which utilize the trend of the mostly parabolic plots of viscosities and conductivities. The results obtained by this method agree well with the optimum slag compositions being used in established operations derived from years of practical experience for various slags used in the furnaces. However, due to extensive turbulence in suspension and gas injected bath smelting processes, the outlined methods cannot be used for these processes. Also great caution should be exercised in their application for three electrode circular furnaces with separate slag cleaning.

Jan 1, 1997