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By Mamoru Kuwabara

A high-power sound which can transmit through any continuous elastic medium with less attenuation, particularly in liquid allows us to externally control the system of concern by using the acoustic radiation force or the cavitation phenomena. These functions may eliminate gravitational and/or atmospheric constraints which are often encountered in conventional operations for producing clean and advanced materials. This paper outlines the recent development in the field of sonoprocessing of materials. Cold model experiments in some vessels have been performed to simulate ultrasonic operations such as inclusion removal from liquid, degassing of melt, emulsification of two liquid phases, solidification processing, and decomposition of chemical species in waste water. High speed visual imaging is carried out for better understanding of the cavitation phenomena as well as the followed microjets during the processing. The radiation force acting on fine suspending objects in a fluid can be utilized for eliminating or rearranging/orienting the objects in the fluid. Acoustically induced cavitation phenomena in liquid can be utilized as an effective dynamic means to control interfacial phenomena as well as micro- and macro-mixing of liquid. Sonochemical and thermal effects in cavitation multi-bubble can be also useful in a waste water treatment.

Jan 1, 2006

By F. Guevara

The paper presents results of physical and turbulent three-dimensional numerical simulation of the gas flow in the wind box and reaction shaft of the concentrate burner of a flash furnace. Physical simulation work was carried out in a 1:5 linear scale model, where the velocity field was measured using a Pitot tube. The mathematical model consists of the three-dimensional averaged Navier-Stokes equations, turbulent kinetic energy and dissipation of turbulent kinetic energy using the Renormalization Group (RNG) theory for the k-e turbulence model. Computations were performed using FLUENT, based in a finite- volume code. The geometry of the concentrate burner was separated in two sections: wind box and reaction tower. Results obtained at the exit of the wind box were used as boundary conditions for the reaction shaft. The effect of boundary conditions on the numerical results was also studied. Results of physical and numerical simulations show an asymmetry of the velocity field at the exit of wind box. This asymmetry is possibly due to existence of a separated flow in the back of the exit ring. The agreement of physical and numerical results assess the capacity of the turbulence RNG k-e model to reproduce correctly the behaviour of the velocity field at the exit of the concentrate burner.

Jan 1, 1999

By Jan Smit

Sulphidic copper concentrates are generally processed by pyrometallurgical means; while oxidative pressure leach processing of such materials has been shown to be technically feasible, there has traditionally been little incentive to choose this route in favour of a smelting option. However, for concentrates with elevated arsenic levels, oxidative pressure leaching offers distinct advantages, as smelter air emission standards and restrictions on concentrate importation have tightened. The current state of pressure leach technology allows for high copper extractions from arsenical copper concentrates, while producing an environmentally stable process residue, without atmospheric emissions of sulphur dioxide or arsenic. In its studies on pressure leaching of copper concentrates, Sherritt has shown that arsenical feed materials can be converted into environmentally stable residues, with excellent copper extractions. The results of recent batch and pilot plant test work are discussed, including the deportments of copper, arsenic and precious metals.

By Stein Tore Johansen

Some ferro-silicon furnaces have heat-recovery equipment. Here, the recovery of electric energy from the off-gases can be increased by increasing the off-gas temperature. This is easily done by reducing the amount of air which usually is mixed into the?off?gas to cool the gas mixture. If the off-gas becomes too hot problems with severe fouling or clogging of the gas channels close to the furnace is observed. The result is irregular stops to clean the off-gas channels. The paper focuses on the nature of the clogging phenomena and some of the ways to avoid clogging. A detailed experimental study was carried out at the Elkem Thamshavn Plant. Theoretical studies were performed to understand the particle deposition, turbulent multiphase fluid flow and off gas combustion in the off-gas channels. The study has resulted in reduced clogging.

Jan 1, 1992

By W. K. Rankin

Achieving continued economic growth with social equity within the natural limits of the Earth's eco-systems is the major issue facing the world today. The material and energy needs of the world cannot be met with the current ways of addressing this issue. The need for metals, an important class of materials, will continue into the future because their unique properties make substitution by other materials impossible in many applications and this need will continue to be met from primary metal production and recycling. However, the recycling rate will increase and the usage pattern of metals will change to reflect the environmental impact of their production and use. Pyrometallurgy has an important role in meeting the metal needs of the future since some metals can only be produced pyrometallurgically; the energy required to produce some metals pyrometallurgically is significantly less than by other methods; most metals are most efficiently recycled pyrometallurgically; and the release of harmful and toxic elements into the biosphere can sometimes best be controlled through pyrometallurgical processing. The development of strategies for pyrometallurgical processing for the future lies in the recognition that sustainable development calls for large step improvements in value delivered per unit of environmental impact over the entire supply chain. Pyrometallurgists can respond to this challenge by contributing to reducing the environmental impact of meeting metal needs using three broad strategies: "end-of-pipe" approaches to convert emissions into benign materials for storage or disposal; flowsheet redesign to limit or eliminate emission production; and improved recycling technologies. A number of examples are discussed to illustrate how the sustainability driver is already influencing the technological development of pyrometallurgical processes, and how these will develop further as the sustainability driver strengthens.

Jan 1, 2003

By Suguru Kohno, Yoshihiro Momose, Masakazu Honma, Tokirou Kamosawa

Copper metal surfaces have been examined by an extremely sensitive surface analysis technique called temperature programmed photoelectron emission (TPPE). The surfaces were ultrasonically cleaned and subsequently abraded by a screw in organic solvents and water. The TPPE apparatus is composed of a Geiger counter with Q gas (He+ iso-C4H10). The curve of photoelectron emission (PE) intensity vs. wavelength from 300 to 170 nm, termed PE spectrum, was repeatedly measured at different temperatures in the temperature- increase process from 25 to 350°C. The number of emitted electrons in a PE spectrum (PE total count) increased, reached a maximum at-250°C, and decreased with increasing temperature. With the surfaces cleaned alone in the liquids the maximum PE total count decreased in the order C3H70H > (CH3) 2CHOH > C2HpH > CHPH > H2O. With the mechanically abraded surfaces in the liquids the maximum PE total count changed as a function of the abrasion period and the maximum tended to appear at higher temperature with increasing abrasion period; the maximum value at 10-min abrasion decreased in the order H2O > CHpH > C2HPH > (CH3) 2CHOH > n-C3HpH. It was suggested that the TPPE behavior can be related to the acid-base interaction between the alcohols and the abraded metal surfaces and the presence of a contaminant over layer on the surface. From the XPS analysis of the 01 s spectra it was suggested that the chemical change of the adsorbed oxygen to oxide oxygen with temperature plays a substantial role in the appearance of the maximum PE total count.

Jan 1, 2000

By K. Walanabe

Kosaka Smelter & Refinery has a history of more than a century as a metallurgical department belonging to Kosaka mine. It has treated for a long time the "Black Ore" or the complicated concentrates dressed from it. The "Black Ore" is composed of black sulfides. It contains not only valuable metals such as gold, silver, copper, lead and zinc but also some impurities like arsenic, antimony and bismuth. With the development of Kosaka's floatation technology, five kinds of concentrates (copper, zinc, lead, pyrite and barite) have been separated from the "Black Ore" but the separation was not complete and each concentrate contained some unfavorable impurities. In 1980s the highly appreciated yen and the drop of the metals prices forced many domestic mines to close their operations. Since then Kosaka Smelter has changed its way of operation to a custom smelter. Now more than 95% of copper concentrates are imported to take advantage of this technology of "Black Ore" treatment. It mainly treats the raw materials that contain high gold and silver like the "Black Ore". Recently, Kosaka has been working on the recycling of the metals from the printed circuit board scraps and sludge which contain some precious metals. The volume of the recycled metal is continuously increasing.

Jan 1, 2003

By Bing Ji Yan, Cui Wang, Ya Peng Zhang, Chuan Hui Li, Hong Wei Guo, Jian Liang Zhang

There are a lot of research of the chlorine element’s influence on blast furnace, and mainly pay close attention to the harm to gas pipes and equipment. There are three kinds of chloride in the blast furnace gas, including HCl, NH4Cl, and NaCl (or KCl, ZnCl, etc.). This paper mainly analyzes all kinds of phenomenon of the chlorine element overflowing blast furnaces in Jinan Steel, and puts forward some different viewpoints, which are that the chloride overflowing out of blast furnace in the types of HCl, NH4Cl, or NaCl (KCl) not only has much to do with raw materials of chlorine load level, at the same time with the blast furnace burden distribution. On this basis, comes up with countermeasures for the different situation, such as adjusting the burden distribution matrix to guarantee the central gas flow smooth and changing the kind of raw materials to reduce the chlorine quantity, which will be helpful to prevent the harmful influence of chlorine element.

Mar 1, 2017

By C. Alexandru Sonoc

Donnan Dialysis uses ion exchange membranes to extract and separate cations. The driving force is provided by differences in chemical potential, rather than by electric fields or pressure. A Donnan Dialysis based process to recover lithium, nickel, cobalt, manganese, and organic acid lixiviant from recycled lithium ion battery cathodes is under development. In this paper we present a model of Donnan Dialysis and results of simulations of the aforementioned process. The simulations show that 170 m2 of membranes can process 1000 L of leachate ([Li+] = 0.285 M, [Co2+] = [Ni2+] = [Mn2+] = 0.095 M, pH 2) in two days and recover 94.1% of the lithium (as lithium carbonate), 99.4% of the transition metals (as mixed sulphates ready for solvent extraction), and all of the organic acid using 423 mol of H2SO4 and 268 mol of KHCO3.

By Guozhu Ye, Mikael Larsson, Eric Burström, Sten Ångström

"Increased use of scrap in steelmaking including scrap use in BOF has a high economic and environmental potential in terms of increased productivity, energy saving and reduced emission of CO2. Preheating and surface cleaning of steel scrap is a concept developed by MEFOS in a four year research program funded by MISTRA, Swedish Foundation of Strategic Environmental Research. The process concept consists of four major steps: 1) Combustion of ASR or other waste fuel and composing of the gas composition. 2) Scrap heating and cleaning in a shaft where the coated zinc is removed as ZnCl2 and scrap is heated to about 600 ºC. 3) Dust separation for recovery of metal zinc. 4) Gas cleaning. This paper will describe the process concept and highlight the major results from preliminary trials around the scrap heating and cleaning shaft.IntroductionSteel is often coated to increase the corrosion resistance. Share of coated and galvanized steel in the world marked is steadily increasing. This results in increased amounts of scrap with different types of coatings. Use of galvanized scrap in EAF plant results in an EAF dust with high content of zinc ferrite and many other impurities like Pb, Hg, Cd and halide. EAF dust is classified as hazardous waste in most of the developed countries and the steel plant has to pay for external treatment for zinc recovery. For use in BOF plant this will result in a BOF dust containing typically 1-5%Zn making it impossible for recycling to the blast furnace.Different approaches for surface cleaning have been investigated in past. Dapper et al. [1] examined the possibility to evaporate Zn, Ni, Cr, Sn from coated materials using chlorine. Chlorinated rinsing of non iron oxides and metals using HCl from combustion of PVC was discussed by Fray [2]. Further studies by Tee and Fray [3-5] have been concentrated on the possibility to vaporize coatings with an air and chlorine gas mixture. The O2:Cl2 ratio in the gas mixture was found to have great importance for control of the process. To avoid the chlorination of iron, this ratio should be kept at a level of 10:1.Scrap pre-heating up to about 600 ºC is a well known method and this alone could save up to 100 kWh per ton steel. The technology has been established since many years and efficient processes were developed in the 90’s. However, no process has fully gained the expected energy savings as the large quantity of the exhaust gas has to be reheated to over 1000 ºC again to destroy the hazardous components like dioxins."

Jan 1, 2008

By T. A. George, David J. Sellmyer

"The concept of achieving a useful high-energy-product magnet through appropriate nanostructuring of known hard and soft phases has been tantalizing researchers since the idea was first proposed. The fabrication of exchange-coupled nanocomposite magnets faces several challenges including aligning the easy anisotropy axes of the hard-phase grains. Here we investigate experimentally two-phase nanostructures of hard Lio-ordered FePt and soft iron-rich/cc Fe(Pt). The Fe-Pt thin films were produced by epitaxial cosputtering onto MgO (001) single-crystal substrates which lead to strong (001) texturing. The measured hysteresis loops indicate nearly ideal exchange coupling. Excellent magnetic properties are obtained, with largest values of coercivity (51 kOe), saturation magnetization (1287 emu/ cm3, J, = 16.2 kG), and nominal maximum energy product (58 MGOe).1. IntroductionA key figure of merit for permanent magnets is the maximum energy product (BH)rrw.x. The achievable maximum energy product is determined by a magnet's saturation magnetization M, and its magnetic anisotropy. For example, it is well known that (BH)rrw.x :S 4n2M,2• In the past, record energy products have been the result of discovering new compounds with high values of magnetization and anisotropy. However, finding new compounds with better magnetic properties than the current record-holding magnet Nd2Fe14B has proven to be difficult. A different approach is to exploit the exchange coupling mechanism between known hard and soft magnetic phases to enhance the maximum energy product [1-5]. In such a composite system, high coercivity is achieved due to the anisotropy of the hard phase as well as a nanostructure which prohibits large-scale domain wall reversal mechanisms. Magnetization is enhanced by the soft phase and loop squareness results from texturing of the hard phase easy-axis as well as complete exchange coupling between the coexisting hard and soft grains."

Jan 1, 2012

By C. P. Manning

This paper reports recent progress in the development of a unique metal extraction technology utilizing zirconia-based inert anodes for the electrolytic reduction of metals from their oxides. In this process, the target metal oxide is dissolved in an ionically conducting liquid solvent phase. An extended anode consisting of an oxygen-ion-conducting stabilized zirconia membrane in intimate contact with a catalytically active electronic phase and an inert electronically conducting cathode are inserted into the molten flux containing the oxide. When the appropriate electric potential is applied between the electrodes the target metal is reduced at the cathode and oxygen ions are selectively transported across the stabilized zirconia membrane and oxidized at the anode. When the process is conducted at temperatures between 1200-1400°C, the ohmic resistance drop across the stabilized zirconia membrane is low, and high current densities on the order of I A/cm2 or greater can be obtained. In addition, the process efficiency can be increased further by directly reforming hydrocarbon fuel over the anode. Laboratory experiments at Boston University have demonstrated the technical viability of employing zirconia-based inert anodes for environmentally sound production of metals such as magnesium, tantalum, aluminum, etc., directly from their oxides. Significant progress has been made in the application of this concept to the electrolytic reduction of magnesium at 1300°C. The research topics covered include stability of the zirconia membrane in the selected molten solvent (flux), volatility of the flux, electrochemical characterization of the electrolytic cell, and analysis of the metals produced.

Jan 1, 2003

By Jun Deng, Daohong Wu, Zhicheng Cao, Jingkun Tang, Luxing Feng, Xun Xue

The effect of reducing temperature, H2/CO mole ratio, and reduction gas flow rate on the metallization rate of oxide pellets were investigated at laboratory scale, with ludwigite iron concentrate used as raw materials. The reducing temperature varied from 850 to 950 °C, the H2/CO mole ratio changed from 1.5 to 4.5, the range of reduction gas flow rate was from 2 to 5 L/min. The results indicate that the metallization degree of pellets increase with increase of the temperature, H2/CO mole ratio, and gas flow rate. However, after temperature rises to 850 °C, metallization degree increases slowly. The effect of H2/CO on the metallization degree is not very obviously with the ratio of H2/CO increasing from 1.5 to 4.5. When the gas flow rate was increased from 2 to 3 L/min, the metallization degree increased greatly from 72.2 to 92.1%. In the flow range from 3 to 5 L/min, the metallization degree was increased slowly. The results obtained could be useful for comprehensive utilization of ludwigite iron concentrate by gas-based direct reduction method.

Mar 1, 2017

By L. Escudero-Castejon, S. Sanchez-Segado, A. Jha, Y. Hara, S. Parirenyatwa

Oxidative alkali roasting of chromite is the state-of-the-art process for manufacturing chromium-containing chemicals, which involves dealing with serious environmental problems arising from handling Cr6+-containing wastes generated in this process. In this article a new method for the extraction of Cr2O3 from chromite ores is explained, based on the carbothermic reduction of concentrates in the presence of alkali investigated in the temperature range of 950–1050 °C. Under these conditions, the iron oxides present in the ore body are reduced to metallic iron and the resulting separation of chromium occurs by forming sodium chromite (NaCrO2). The reduced samples are magnetically separated for the recovery of an iron-rich fraction, and a non-magnetic fraction containing NaCrO2, MgO and other impurities. The further treatment of the non-magnetic fraction by leaching yields a Cr2O3-rich product of approximately 85% purity, with remaining alumina, alkali and magnesia. The main advantage of the process is that, under reducing atmosphere and subsequent leaching conditions, the oxidation of Cr3+ to Cr6+ is completely avoided; thereby decreasing the risk of land, air and water pollution.

Mar 1, 2017

By Patrick M. Eduafo, Brajendra Mishra, Mark L. Strauss

Direct acid leaching of rare earth metals (REMs) from waste lamp phosphors is non-selective, leading to co-dissolution of impurities mainly calcium, phosphorus, silicon, iron and zinc. Calcining the phosphor powder at different temperatures followed by leaching with HCl isn’t efficient for the extraction of all the chief rare earths especially cerium (Ce), lanthanum (La) and terbium (Tb). Therefore, multi-stage leaching operations are required for the separation of the REMs in phosphor dust. This paper will outline a new process for extracting Ce, La, Tb, Eu and Y from waste fluorescent lamps using a three-stage leaching and separation process. A flowsheet has been developed which shows this process is selective and efficient.

Jan 1, 2015

By S. W. Ip

Over the years, the importance of surface and interfacial phenomena has been neglected by the copper-nickel industry. As a result, little data on the surface and interfacial tension of the Ni matte and slag system are available in the literature. In view of the scarcity of information in this area, the surface tensions of the Ni-Fe-S system together with the Ni-Fe-S and fayalite type slag system were measured using the sessile drop technique. Drop images were obtained by X-ray radiography. For the Ni-Fe-S system, the results showed that the surface tension of the matte increases with matte grade. The surface tension behavior with changing matte grade showed a slight negative deviation from ideality. This indicated that FeS is slightly surface active in the nickel matte system. Results also indicated that small increase in sulphur content in the matte can decrease the surface tension quite significantly. The measured surface tension of the Ni-Cu-S system showed a linear relationship with the Cu2S content in the matte. The surface tension decreased with Cu2S content. Interfacial tension measurements showed a similar trend. That is, interfacial tension increased with increasing matte grade. The presence of MgO (-1.5%) and A12O3 (-6%) in the slag does not affect the interfacial tension value. Effects of matte surface tension on phenomena such as entrainment of matte in slag and infiltration of matte into refractory pores are discussed. The calculated flotation coefficients indicated that flotation of nickel mattes cannot be avoided by changing the matte grade. Filming of matte on bubbles can occur below a matte grade of about 19% Ni3S2. As for infiltration, refractory bricks containing high Cr2O3 will be easily wetted by matte regardless of matte grade. Therefore, bricks containing high Cr2O3 can easily be infiltrated by liquid matte.

Jan 1, 1993

By Ruirui Wei, Mingrui Yang, Xuewei Lv

Calcium ferrite, as the main bonding phase in the sintering process, greatly influences the property of sintered ore. Ultrasonic vibration has been widely applied to the treatment of metals to improve the properties of metals. In this work, ultrasonic vibration was introduced into the calcium ferrite and numerical simulation was carried out by solving the Rayleigh-Plesset equation to investigate the influence of ultrasonic conditions, including frequency, power and initial radii of cavitation bubbles on the cavitation bubbling behavior in calcium ferrite melt. The results indicated that lower ultrasonic frequency, higher power, and an appropriate initial radius of bubble promotes ultrasonic cavitation.

Mar 1, 2018

By W. Murray Small

Nickel plays an important role in determining the properties of many stainless steels and superalloys. Cobalt also contributes significantly to the performance of certain grades of superalloys. A major technical aspect, in which both of these metallic elements are involved, concerns the solubility of nitrogen in these classes of alloys. Beyond certain content limits, dissolved nitrogen may contribute to the deleterious mechanical behavior by these alloys. It is therefore essential to control the level of this element during alloy processing. In this paper, results from several experimental studies have been assembled and are analyzed to describe phenomena related to the individual effects of nickel and cobalt on the solution of nitrogen in several groups of alloys. Both solid and liquid alloy systems are considered. This information may be used as a guide to limit or control the presence of this interstitial element in alloys.

Jan 1, 1993

By H. K. Lin

Pyrite oxidation in chloride solutions was investigated with cyclic voltammetry, ac impedance and potential step techniques. The pyrite oxidation in quiescent electrolytes is irreversible and controlled by diffusion. Depression of the semi-circle in the complex plane plot has been explained mathematically based on the concept of the equivalent circuit. When the semi-circle is depressed, the mathematical formula indicates that the reaction resistance should be obtained from the intersection of the semi-circle with Z-axis instead of the semi- circle diameter. The peak charging current densities at 1.10 and 0.90 V vs. SHE obtained from the equivalent circuit coupled with the ac impedance measurements match the peak current densities obtained with the potential step measurements.

Jan 1, 1997

By Hebi Yin

A two-dimensional finite element solidification model was developed to simulate the transport phenomena occurring during laser deposition of AISI 410 stainless steel during the Laser Engineered Net Shaping (LENS®) process. The molten pool geometry and the distribution of temperature, solute concentration and velocity were calculated during deposition of a thin wall plate. An analysis of the simulations results revealed the importance of heat transfer by both conduction and convection as well as the roles of the driving forces for convection in the molten pool. The heat transfer and the flow pattern in the molten pool are considerably dependent on the travel speed of the laser beam. For the alloy and process parameters in the simulations, no significant macrosegregation was observed. The temperature-dependent properties and thermodynamic variables involved in solidification modeling were calculated using Thermo-Calc software. The results of this work contribute to the current understanding of transport phenomena in the molten pool of laser deposition processes.

Jan 1, 2008