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By Caisa Samuelsson

Experimental studies in laboratory-scale equipment have been carried out to study the vaporisation from dust generated during the copper converting process. In the present work the vaporisation of Zn, Pb, As, Sb, and Bi from a dust collected in the electrostatic precipitator after the copper converter were studied. The results show that Pb, Bi and As were vaporised to a high degree from the dust at a temperature above 900°C in a gas containing N2, SO2 and a small amount of H2. The vaporisation was high for these elements also in a gas containing N2, SO2 and 02 at temperatures above 1120°C. In an earlier study, thermodynamic calculations showed that it is possible to selectively condense metals at high temperature' in a gas atmosphere generated during a copper converting process. The present study was carried out to verify the thermodynamic model. The results indicate that it should be possible for a selective condensation of Zn at high temperature. The temperature required for a selective condensation of Zn is dependent upon the gas atmosphere, e.g., the oxygen potential.

Jan 1, 1998

By D. A. Salinas G., A. H. Castillejos E.

Pachuca tanks are commonly used in the hydrometallurgical industry to carry out leaching operations. The fluidynamic characteristics of the liquid phase, resulting from the injection of gas into the draft tube, are important to achieve the complete suspension of the mineral particles and has a decisive influence in the mass transfer processes occurring in this reactor. This study investigated the effect of different design and operating characteristics on the liquid velocity field. using a laboratory-scale Pachuca tank. The transparent model was filled with water, and air was injected through the bottom in the absence of mineral particles. The liquid velocities over the whole reactor were measured under several experimental conditions using particle image velocimetry (PIV). This technique allowed to obtain a very detailed picture of the liquid motion even in the draft tube, as long as bubbles were absent from the measured field of view. The experiments have shown that the liquid velocities increase with increasing the draft tube to tank diameters ratio, the distance from the conical bottom to the draft tube entrance, or the gas superficial velocity. On the other hand, an increase in the water level with respect to the draft tube outlet caused a decrease. A mathematical model, which used the no-slip model, to calculate the variation of axial effective density along the two-phase region, was found to predict liquid velocity fields which agree very satisfactory with the experimental results obtained under all the conditions studied.

Jan 1, 1999

By Truan-Sheng Lui, Li-Hui Chen, Fei-Yi Hung, Cheng-Yi Chen

"This research used the austempering heat treatment on the SCM435 thin specimen with a type of double loop and obtained the Cr-Mo bainite structure, and then we could further investigate the mechanical properties of SCM435 bainite structure. Experimental data showed the stability of the mechanical properties of specimen with austempering temperature 830°C for 25 minutes was better than that of 15 minutes. The size of austenite grain affected the strength of thin specimen. After austempering at 830°C-25minutes and salt bath at 290°C, the stability of UTS was better than that of salt bath at 310°C and 330°C. The average hardness of all specimens was about more than HRA70. The specimen with austempering at 830°C-25minutes and salt bath at 290°C-30minutes had bigger grain size of austenite and retained y, it also had higher hardness and strength toughness. So, its stability was improved for tensile strength comparing with traditional tempered martensite process.IntroductionSCM435 is a Cr-Mo steel with high strength and high hardness properties, and it has been widely used in machine parts, shafts, gears and strength screw products [1-3]. However, this system often has lower reliability due to the brittleness of high-temperature tempering and quenching inequality. Considering the austempering heat treatment can obtain the uniform bainite structure to improve the temper brittleness, and the austempering heat treatment is a continuous process that it also has efficiency and uniformity. For the thin plate specimens, the mechanical properties of the bainite structure are better than traditional martempering structures."

Jan 1, 2013

By Jacqueline JAlexander

Two of the most important phenomena which govern the continuous casting process and determine the quality of the product are the fluid flow and the heat transfer. Steel flows into the mold through the ports of a bifurcated submerged entry nozzle (SEN), which directs the jet to the mold narrow faces where the superheat contained is dissipated on the solidifying shell. Many important aspects of the fluid flow in the mold are transient and difficult to control. However, the time-averaged flow pattern in the mold is greatly influenced by the nozzle geometry, the submergence depth and the mold dimensions. The aim of this work is to analyze the relationship between the heat transfer and the fluid flow pattern inside the mold using the CFD technique at several operating conditions.

Jan 1, 2009

By Karl-Michael Zett, Marcus Kirschen, Ashraf Hanna

"Bottom purging systems are well established practice in refining metallurgy and an increasingly important technology for the EAF process in steel industry. Direct bottom purging provides efficient mixing of the entire melt volume, increases turbulence intensity in the melt, and improves mass exchange of alloy additions or oxygen. Continuously rising columns of dispersed gas bubbles helps to increase removal of volatile components carbon monoxide and hydrogen avoiding boiling retardation. Direct purging (DPP) systems provide cost benefits especially for EAF processes where metallurgical constraints have to be considered, e.g. for alloyed and stainless steel production, foundries. Case studies are presented.IntroductionCurrent EAF Technology and Production Constraints in Steel IndustryApproxinlately 30 % of steel, 446 Mio. tonnes in 2011, was melted in the electric arc furnace (EAF) with increasing tendency due to its large flexibility in production volume and raw materials. With recent increase of prices for ferrous raw materials the requirements for production of high quality steels from low quality scrap, direct reduced iron (DRI) and blends of ferrous raw material in various qualities increased. Maximum yield of ferrous raw material, oxygen, carbon, and alloys and minimum energy costs are of high importance. At modem high productivity levels even small process improvements provide considerable cost savings. Such improvements are caused, e.g., by efficiency increase of mass and energy transfer in the EAF. Optimization of flow pattern in the steel bath is therefore important for efficient melting of scrap and DRI and high homogeneity of the melt [1-4]."

Jan 1, 2013

By Rudolf Keller

"EMEC Consultants is developing a process to extract oxygen, aluminum and silicon from lunar anorthositic soil. The process will provide oxygen in space for propulsion, aluminum as a structural material, and possibly silicon for the construction of solar cells.The evolution of the process concept in the course of our present NASA-sponsored SBIR effort is discussed. A molten salt electrolysis producing aluminum and oxygen is the central step; inert anode technology is to be employed. Silicon will be produced by reducing the anorthite, CaAI2Si20S' with aluminum. In a steady-state operation, all components of the ore added have to be removed from the process, and the removal of calcium is a major topic of our experimental studies.Utilization of Lunar ResourcesUtilization of lunar resources may play an essential role in the exploration of the solar system and the conquest of space. High costs are involved in overcoming Earth's gravity to supply missions in space. Even at a low projected cost of $ 300 for transporting a pound of payload into Earth orbit -- today's costs are many times higher -- it appears attractive to use resources in space to produce needed materials. Processing of lunar resources on the lunar surface is an obvious possibility.Oxygen is a product of major interest. It is required for support of human life in space. Even greater quantities may be needed for propulsion, to conduct further missions into space. To satisfy this demand for oxygen through lunar processing requires a quite different solution than to supply oxygen on Earth, where oxygen gas is abundant and easy to extract from air or water. On the lunar surface, solid oxide materials have to be used. Hydrogen reduction of ilmenite and subsequent electrolysis of the resulting water is being studied [1]. Other suggestions include fluorination of lunar soil [2], reduction with lithium and electrolytic decomposition of the resulting lithium oxide [3], and aqueous HF leaching [4]."

Jan 1, 1988

By Bo Zhou

During secondary aluminum recovery, complex aluminum scraps are melted and refined often in a rotary melting furnace and the aluminum metal has to pass through a molten salt layer and melt down in a bottom aluminum bath. Previous experimental study and industrial observations have indicated that salt shell formation and re-melting on the metal solids in the early stage plays a critical role in the overall melting process of the scrap. In the present paper, mathematical models are developed to simulate the process of salt shell formation and its re-melting, as well as aluminum melting in the molten melt. Influence of the salt layer properties, the residence time of the metal particles in the salt layer, the particle size, the temperature of bulk melt were investigated. Reasonable agreement with the measurement data was reached. The developed melting model will be used to construct a population balance model of the scrap melting behavior for a rotary melting furnace, taking into account the distributed characteristics of the scrap. Finally, an overall process model based on Computational Fluid Dynamics (CFD) for the rotary furnace will be constructed, coupling with the population balance model for the scrap melting.

Jan 1, 2003

By Paponetti B. . A.

Gold is usually recovered by cyanidation, thiourea leaching and amalgamation, however the efficiency of these technologies, in the case of refractory ores, is low ever when fuie grinding is practised. For example, .if the gold particles are included in sulphide minerals, the leachant cannot reach them, so they are often lost in the tailings. Hence .it is first necessary to break the sulphide crystals by preliminary treatment such as roasting, nitric .acid oxidation, pressure leaching and bacterial oxidation and then apply a conventional extractive technique for satisfactory gold recovery. This paper describes the effect of biological pre-treatment with Thiobacillus ferrooxidans) on the? extraction ? and? recovery of gold by conventional cyanidate. leaching from; a refractory arsenopyrite ore from Golcuck (Turkey).

Jan 1, 1991

By Y. Fukunaka, M. Niinae, E. Kusaka, T. Kuzuya, R. Ishii

"Samarium oxalattr particles was precipitated in oxalic acid aqueous solution from samarium-loaded D2EHPA solution emulsified with a conventional impeller. The calculated fractional precipitation of samarium oxalate was reasonably compared with the value determined by chemical analysis. Morphological variation of oxalate precipitate particles was then examined with H2C2O4 concentration in aqueous solution, Sm(III) and D2EHPA concentrations in organic phase. The needle-like precipitate was identified as Sm2(C2O4)3 10H2O by XRD. Precipitates obtained at higher H2C2O4· or Sm(III) concentration greatly decreased the length of major axis of precipitate, while those at higher D2EHPA concentration increased it. The oxalate was further precipitated under ultrasonic irradiation. However, the morphological variation caused by theses processing variables was not so evident under ultrasonic irradiation as in an impeller or shaking mixer.IntroductionThe materials processing of the rare earth elements must be reviewed from the scope of industrial ecology, since they have the potential applications of magnetic materials as well as secondary battery in developing programs of the electric vehicle. The technological trend to develop the electric vehicle may greatly influence the concept of materials processing, since the global· environmental problem must accommodate with the sustainable development for mankind. The recycle design must be a key issue in the materials science and engineering.Solvent extraction provides a unique separation technology -in this sense. Doyle (1)(2) reported the integrating solvent extraction with processing of advanced ceramic materials, whose chemical composition and microstructure must be precisely controlled. In her paper, the higher productivity inherent to the present process superior to hydrolyzing metal alkoxides was emphasized. Oxalic acid has been used as precipitant for rare earth purification process, since rare earth oxalate has a very small solubility in water and can be easily decomposed to oxide. It is thus suitable for precipitation stripping agent in cationic exchange type extracting system (i.e. D2EHPA, VA-10, PC-88A and so on)."

Jan 1, 2000

By O. Barbosa F.

The thermochemistry of the systems SCN-H2O, Au-SCN-H2O and Ag-SCN-H2O is discussed. Potential-pH diagrams at 25°C are drawn for each system considering several sets of concentrations of the species involved. The information provided by the potential-pH diagrams is.complemented by distribution curves for each series of gold and silver complexes with thiocyanate. The analysis includes comparisons between the thiocyanate systems and the analogous cyanide systems, pointing out analogies and differences between the leaching of gold and silver with thiocyanate and with cyanide. The possibility of using soluble oxidizing agents such as ferric ions, hydrogen peroxide and Caro's acid is evaluated. The thermodynamic data used in the calculations and the chemical reactions represented in the Pourbaix diagrams are all reported in three Appendices. The overall results indicate the thermodynamic conditions for gold and silver leaching by thiocyanate.

Jan 1, 1989

By Saskia Duyvesteyn

Small ion-exchange resin particles provide faster mass transport than conventional-sized beads. Unfortunately, high pressures are needed to pump solutions through columns containing small resin particles. It is preferable to disperse fine resins in the solution being treated. Screens have been used to separate the resin from the solution, but screens do not retain fines created by attrition of the resin particles. We have developed a separation process based on flotation, which relies on the surface characteristics of the resin, instead of size. The resin is conditioned with a surfactant before dispersing it in the solution to be treated; this increases the hydrophobicity of the resin sufficiently for froth flotation, without introducing surfactant directly into the solution. The surfactant adsorbed on the resin surface does not appear to impair the kinetics of metal ion removal. A flowsheet for an effluent treatment process is proposed; other applications are clearly possible.

Jan 1, 1998

By Masahiro Hirasawa

"As a fundamental study on pyrometallurgical process that involves recycling steel-making dusts, of which major components are oxides of Zn and Fe, and waste polyvinyl chloride simultaneously ·at. a temperature below 1273 K, the reactions between the mixture of ZnO + Fe20 3 and PVC or the compound ZnFez04 and PVC are investigated in a series of thermogravimetric and small scale reactor experiments under inert atmosphere at below 1273 K. The reaction mechanisms are discussed· on the .basis of the thermogravimetric data. From the results of reactor experiments, it is shown that the chlorination of Zn in the oxides by Cl in PVC, the vaporization of ZnC12, the reduction of iron oxide to metal Fe by C and H in PVC, and, thereby, the separation of Zn and Fe in the oxides take place simultaneously at the temperature ~= 1200 K.IntroductionSteelmaking dusts are metallurgical wastes consisting mainly of oxides of Zn and Fe with smaller amounts of other heavy metal elements, such as Pb. In the recent investigation, [1] the present authors have investigated the fundamental aspects of a potential pyrometallurgical process· of recycling steel-making dust with polyvinyl chloride (PVC) at temperature T < 1273 K under Ar atmosphere. The performance of a similar process, in which HCl in the combustion gas of PVC is used to chlorinate Zn in the EAF dust under oxidizing atmosphere, has been investigated by Tailoka and Fray [2] with fundamental experiments. Figure 1 shows an example of the potential ·diagram of Zrt-Cl-0 and Fe-Cl-0 systems. In the figure, we can find two regions where ZnCl2(g) can be separated from Fe containing compounds. One is ZnCiz-Fe20 3 coexistence region at higher oxygen and chlorine potentials and the other is ZnCl2-Fe coexistence region at lower oxygen and chlorine potentials. The process adopted by Fray and coworkers is aimed mainly at the performance of Zn/Fe separation in the higher oxygen potential region. In the present study, the lower oxygen potential region is focused on."

Jan 1, 2000

By Susanne Pignolet-Brandom

Reflected light microscopy scanning electron microscope energy dispersive spectroscopic analysis and backscatter electron image and electron microprobe chemical analysis have been used to study lead sinter and lead blast furnace slag. These studies provide invaluable information on the phases present their intergrowths, and their chemical composition. Such information increases the understanding of the nature of pyrometallurgical processes and the behavior of minor elements during these metallurgical processes.

Jan 1, 1987

By H. Kamiya, H. Hasegawa, M. Nojiri, S. Matsui, Y. Fukuda, M. Tsukada

"The present paper focuses on the action mechanism of anionic polymer dispersants in dense Si3N4 and SiC suspension. An atomic force microscope (AFM) was used to determine the relationship between the macroscopic suspension viscosity and the microscopic adsorbed structure of a polymer dispersant at the solid / liquid interface. The surface interactions within the suspensions were analyzed in various dispersant pH and additive conditions. The addition of an anionic polymer dispersant decreased Si3N4 and SiC suspension viscosity and increased electro-steric repulsion force on the non-oxide surface in solution at pH> 6 which was the isoelectric point of the materials. It was assumed that the increase of repulsive force was promoted by a hydrophobic adsorption of polymer dispersant on the non-oxide particles.IntroductionThe surface of silicon nitride and silicon carbide powders in a water suspension system has quite a complex molecular structure. In the case of Si3N4, hydroxyl and ammonium groups form on the surface and the pH of the suspension is increased from neutral to about 10 due to surface oxidation. The particle surface is negatively charged in alkaline solutions (pH=10), because the isoelectric point of silicon nitride exists in the pH range from 5 to 6. However, in spite of charging the negative surface charge, an anionic polymeric dispersant is generally used for the reduction in slurry viscosity.In dense SiC suspensions, an anionic polymer dispersant is generally used in order to disperse aggregates and reduce the suspension viscosity, too. Since an anionic dispersant is used in alkaline solutions higher than the isoelectric point of silicon carbide, the dispersant adsorbed on the negative charged surfaces of SiC.Few researchers have discussed and estimated the adsorption mechanism and structure of anionic polymeric dispersants on silicon nitride and silicon carbide surfaces. This is because it is difficult to observe the structure and measure the interaction at the solid/liquid interfuce directly. However, new developments in surface-force measurement technology have enabled the determination of non-DLVO type interaction for analyzing aggregation behavior2. The use of the AFM for analyzing the effects of various surfactants and co-polymers on colloidal dispersions and solid surfaces has also begun to rapidly expand to characterize the interaction between solid surfaces."

Jan 1, 2000

By Min Chen, Lei Xu

Sintering behavior and performance of high alumina refractory based on the ternary subsystem MgAl2O4-CaAl4O7-CaAl12O19 were investigated using ZrO2 as an additive up to 8 wt.% by solid state reaction sintering. It was found that the added ZrO2 could dissolve in the CA6 grains in the form of a solid solution, which enhanced the isotropic growth of CA6 grains and then improved the sintering. As a result, the densification process was improved and areas with enrichment of ZrO2 showed a more compact structure. With further increase of ZrO2 addition, tetragonal ZrO2 were found to locate in the grain boundaries for exceeding the solid solubility limit, which enhanced the thermal shock resistance, indicating that addition of ZrO2 exhibited a positive effect on sintering behavior and performance of this refractory. In addition, it is considered that the optimal amount of ZrO2 addition was about 4% considering the performance together with the cost.

Jan 1, 2015

By Mototsugu Matsuno

A new process has been developed to treat fly ash generated from municipal incinerators, which contains not only toxic metals such as lead and cadmium, but also dioxins. The process includes the following steps; fly ash is formed into green pellets with some additives and the pellets are then roasted to eliminate or stabilize the toxic metals and to decompose dioxins. A pilot plant with a capacity of approximately 100 kg/hr was used to test the process. The tests verified that heavy metals were either volatilized or stabilized and dioxins were decomposed by high-temperature roasting. The pelletized ash was found to be non-toxic, so that it can be recycled as artificial lightweight aggregate. It was also found that volatilized metals collected as secondary ash can be recycled as smelting resources.

Jan 1, 2003

By Eric J. Beckman

Recovery of metals from dilute solution, whether the matrix is solid, or liquid, remains a considerable technical and financial challenge. Methods currently exist whereby metals can be extracted from either type of matrix, yet these methods consume significant quantities of reagents and can also generate multiple waste ,streams in the process. Technology developed in our lab allows efficient application of environmentally-benign CO2 to a number of separation problems involving metals. For example, we have employed biphasic mixtures of C02 and water as a green acid leach medium. Metals have been extracted from a steelmaking process residue and then recovered as metal carbonates through depressurization. In this process, metals are extracted and recovered without the use of reagents other than CO2 and water, and CO2 is sequestered as a solid. In addition, through synthesis of Cal-miscible phase transfer agents, we have shown that CO2 can replace the organic solvent currently used in refining of precious metals, The sensitivity to pressure of phase behavior in a CO2-mixture may allow significant streamlining of the process as well. Finally, CO2 soluble chelating agents have been used to extract toxic metals from acidic effluent such as that found in plating facilities.

Jan 1, 1999

By Giuseppe Granata

An innovative process using titanium tetrachloride (TiCl4) gas as reactant has shown successfully to obtain titanium through electro-winning of TiCl2 formed in-situ on titanium cathode. The process involves a continuous feed of TiCl4 gas reacting onto a titanium cathode immersed in a molten salt (NaCl-KCl), whereby in-situ formation of titanium dichloride (TiCl2) through a disproportion reaction. Simultaneously, the TiCl2, thus in-situ formed in the molten salt media, has been reacted into chlorine gas and titanium, the latest electrodeposited on the titanium cathode by electrowinning. The reaction kinetic of this innovative process was investigated in terms of TiCl2 in-situ formation rate and galvanostatic electrodeposition rate, where, in particular, the effect of operating variables such as TiCl4 partial pressure and flow rate, as well as temperature and galvanic potential applied was investigated.

Jan 1, 2014

By Roberto Parreiras Tavares, Frederico da Costa Fernandes, Guilherme Antonio Defendi, Vangleik Ferreira da Cruz, Júlio César de Sousa Pena

"Near-net-shape casting is an important area of research in the iron and steel industry today. Among the near-net-shape casting processes, the single-belt caster seems to be the most promising, since it is the only one that can achieve levels of productivity similar to those obtained with conventional continuous casting machines. One of the most important aspects in the single-belt casting is the feeding system used to deliver liquid metal over the belt. This system determines the velocity distribution and the levels of turbulence of the liquid metal and affects the quality of the strips. In the present work, a metal delivery system having a simple geometry was proposed. Using the CFD code CFX 5.6, a mathematical model to simulate three-dimensional turbulent fluid flow and heat transfer in that system has been developed. This model was used to analyze different configurations of the metal delivery system and the free surface shape of the fluid was also determined. A physical model of the feeding system was built and used to validate the predictions of the mathematical model. The fluid flow calculations have been validated by dye injection experiments and laser doppler anemometry. Measurements of the free surface levels have also been performed. These experiments provided supporting evidence for the predictions of the mathematical model.IntroductionTo maintain its competitiveness in the present market, the metallurgical sector, particularly the steelmaking companies, are developing new techniques of production. Some of these new processes are focussed on the strip casting technologies. Among these technologies, the SingleBelt process is considered the most interesting option, reducing the number of rolling steps and, consequently, the final cost of the product, especially the part associated to the energy consumption (fuel and/or electric energy). This process can also reach levels of productivity that can not be matched by other strip casting methods(1). One of the most important aspects concerning these new processes is related to the liquid metal delivery system. This system can have a significant effect on the final quality of the strips, since it determines the velocity distribution and the levels of turbulence of the liquid metal."

Jan 1, 2004

By Huimin Lu, Lian Zhou, Panpan Wang

"For the low concentration C02 exhaust gas from coal-fired power plant, steel plant emission trapping and recycle problem, a pressure swing adsorption process was studied, using a porous imidazolate framework materials (ZIFs) as adsorbent, separating carbon dioxide from fuel gas mixture. In the carbon dioxide reduction condition by electrochemical method, using ionic liquids as electrolyte, the oxygen and carbon products could be obtained, including carbon nanotube, nano carbon fiber and amorphous carbon. At last, a new C02 collection, recycling and reuse technology was formed.IntroductionDuring the combustion of fossil fuel in coal-fired power plant or steel plant, large amount of carbon dioxide has continuously emitted into the atmosphere. The phenomenon has resulted in the melt of arctic glacier and the frequent emergence of abnormal climate. How to reduce the emission of carbon dioxide and protect human living environment has become a worldwide challenge. Recently, there are three routes to resolve this problem: The first one is to adjust the energy structure and develop new energy, such as solar, wind, hydrogen; the second one is to improve energy efficiency and avoid waste; the third one is to research capture and sequestration of carbon dioxide (CCS). But many researchers have come to realize that the recovery and utilization of carbon dioxide are more important than the sequestration of it. Because the captured carbon dioxide just buried under the earth maybe cause secondary pollution if carbon dioxide leak out from the adsorbent."

Jan 1, 2013