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By Baozhong Zhao

Experimental results have shown that fluxing with soda ash (Na:zC03) can remove As and Sb from molten copper at the rate of As>Sb, but is relatively ineffective in removing Hi. The rate of impurity removal is controlled by impurity mass transfer in the metal phase. In this paper, a mathematical model was developed to describe the impurity removal phenomena. The model incorporates the effects of molten bath mixing intensity, soda ash feeding rate, oxygen content in the molten copper and soda ash fluxing by surface addition and injection. The model predictions are in good agreement with experimental results and may be used in designing large scale tests.

Jan 1, 1996

By Sanaz Mosadeghsedghi

The feasibility of the application of electrodialysis in separation of light and heavy rare earth elements (REE) in synthetic solutions was investigated. The experiments were carried out using single and binary solutions of a light (cerium) and heavy (ytterbium) REE. The effects of electrical voltage, electrical current, and the addition of complexing agent (EDTA) to increase the separation selectivity were investigated. Separation of Ce and Yb was achieved in binary solutions with and without the addition of EDTA. Higher degrees of separation were seen at higher voltages. Ce–Yb separation was more significant in the presence of EDTA. The separation factor of Ce–Yb and Ce–Yb-EDTA were 1.44 and 2.60, respectively.

By K. C. Mills, P. N. Quested, A. P. Day, R. F. Brooks

"Methods have been developed to measure the physical properties of molten materials relevant to the fluid flow in high temperature processes. Data for the densities, viscosities and surface tensions of Al-, Ni- and Fe-based alloys are compared with (i) values for the pure metals and (ii) estimated values obtained from models making use of chemical composition of the alloy. Experimental values for metallurgical slags are also given and compared with estimated values.1 IntroductionPhysical property data has proved very useful in improving process control and product quality. For instance, in the continuous casting of steel the viscosity (TJ) of the mould flux is important since it determines (i) the optimum casting conditions, nVc = 2.5±1 dPas (m min-1) where V c is the casting speed and (ii) the level of slag entrapment (which leads to inclusions) in the metal. Thus data for properties like viscosity are exceedingly useful in understanding the process and the problems encountered and the causes of defects and problems.Another interesting development which has helped to increase our knowledge of processes and improve process control and product quality is the development of mathematical models of the fluid and heat flow in the process. These models have been developed to the stage where one of the prime requirements is for good physical property data for the industrial materials involved. Recently, Oxley [1] has shown that the use of reliable, experimental, property values for the commercial alloy in a commercial software package produced a significant improvement in the prediction of casting defects. Thus reliable property data are required for liquid metals but also for (i) liquid slags since many processes involve the use of a slag to refine and protect the metal or to lubricate the mould and (ii) refractories, sand and investment moulds."

Jan 1, 1999

By Pandey H. D.

The paper describes a fluidised bed ion exchange method for simultaneous removal of phenols and cyanide from the effluent. Use of an eluant enables regeneration of the resin in the continuous operation mode. The breakthrough experiments conducted both on the laboratory scale and on a pilot plant scale have shown that while the level of phenol can be brought down from 462 ppm to about 6 ppm, the free cyanide is almost totally removed. An examination of data indicates that the method can serve the twin objectives of pollution control and phenolic compounds recovery.

Jan 1, 1992

By N. El-Kaddah, V. L. Acoff, M. Arenas

"Control of the weld penetration, weld pool shape and temperature field in arc welding is critical to achieve the desired microstructure and mechanical properties in the resultant welds. This is particularly important in welding gamma titanium aluminides (y-TiAl) where the weld pool is relatively shallow and the temperature gradient in the heat-affected zone is quite steep. This paper investigates theoretically and experimentally the evolution of the shape of the weld pool for stationary gas tungsten arc welds in y-TiAl alloys. A mathematical model has been developed for predicting the electric current flow, the resultant electromagnetic forces in the metal, and the transient development of the temperature and velocity fields in the molten pool generated by a spatially variable heat flux at the arc-striking zone. The governing equations were solved numerically using the control volume technique. Welding experiments were carried out to determine the shape of the weld pool and the extent of the heat affected zone at different welding times for model validation. The numerical predictions were found to be in reasonable agreement with measurements. It is suggested that the model presented in this paper is likely to provide the information needed for predicting the microstructure and mechanical properties of y-TiAl welds. IntroductionIn recent years, there has been considerable interest in the welding of gamma titanium aluminides as a means of manufacturing high-temperature, high-performance components for turbine and automobile engines. These alloys are highly reactive, and must be welded in vacuum or inert gas atmosphere, rendering electron beam, and inert gas tungsten arc welding (GTA) to be the only suitable welding techniques for joining these materials [1-3]. The GTA welding is especially attractive because of its flexibility and relative cost-effectiveness. However, previous studies on the weldability and weld properties of these alloys using this process revealed a decrease in the mechanical properties in the fusion zone [4]. This is generally attributed to the change of the original duplex structure to a dendritic structure amplified by the shallowness of weld spot. Quantifying the effect of arc operating parameters on the geometry and temperature profile of the welding pool prior cooling is the first step for controlling the fusion zone microstructure and mechanical properties."

Jan 1, 1999

By Jorge Alberto Soares Tenório, Romano Espinosa, Felipe Fardin Grillo, José Roberto de Oliveira, Denise Crocce

"The aim of this work was evaluation of the recovery of Zn and Fe of the EAFD added to the hot metal in the form of briquette at temperature of 1500°C. The EAFD was agglomerated by cold briquetting and introduced in the hot metal. This study utilized a bench-scale equipment to melt, during this process to kept a flow rate of inert gas above the bath. Were collected periodically metal samples and the samples were analyzed for determination of the content of total silicon and carbon by chemical analysis. Zinc oxide, zinc ferrite and other oxides were reduced and were volatized and collected by a cleaning system of dust (baghouse) located on top of the oven. More than 98% of iron were recovered from EAFD during the test. It was possible to produce a dust containing about 68% zinc by means of adding of EAFD.IntroductionIn the first semester of 2010, steel production was about 706 million tons, 27.9 % more than in the first half of 2009. Not a significantly increase if 2010 data is compared with the first semester of 2007 (only 7.2 % higher), before the world’s economic crises. Steel production is divided into two main routes. The first one, and most used, is the Basic Oxygen Furnace Process (BOF process), which in 2008 accounted for approximately 67.1 % of steel production. The second route is carried out in the Electric Arc Furnace (EAF) that in 2008 represented 30.6 % [1 ].Electric arc furnace dust (EAFD) is a solid waste generated during the steel making process. It is classi?ed according to NBR 10004 as dangerous solid waste-class I, because the elements Pb e Cd leach in water exceeding the maximum limits permitted by the NBR 10004 [2 ]."

Jan 1, 2012

By Baokuan Li, Qiang Wang, Zhu He

"A mathematical model has been developed to investigate the magnetohydrodynamic (MHD), thermal, and solidified behavior in electroslag remelting process. Based on the finite volume method, a multiphase coupling MHD approach is employed to investigate the droplet formation as well as movement in molten slag under the action of an alternating current. The VOF formulation is adopted for interface tracking. The electrical potential method is adopted for the electric current and magnetic field. The Electromagnetic force and Joule heating are recalculated at each time step and then is implemented in the momentum and energy equations as a source term, respectively. Moreover, solidification of the metal is described by an enthalpy-based formulation, while the mushy zone is treated as a porous medium with porosity equal to the liquid fraction. The model is used to investigate the effect of electrode tip shape on MHD, thermal, and solidified behavior and provide valuable information.IntroductionElectroslag remelting (ESR) process has been used widely to produce high-performance alloys dedicated to critical application, such as hot work tool steels, nickel base alloys, the manufacture of components in aerospace and landbased turbines, etc. Figure 1 shows a schematic diagram of ESR process including a consumable electrode, a molten slag pool, a liquid metal pool, a solidified ingot, and a water-cooled mold. Alternating or direct current flows from the electrode to the water-cooled baseplate through the high resistivity calcium-fluoride-based molten slag which result in Joule heating and Electromagnetic force (EMF). Part of the Joule heating melts the electrode and the droplets travel through the slag and accumulate the liquid metal pool. The electrode is continuously advanced into the slag as it melts to build up an ingot of improved structure and composition by controlled solidification and chemical refinement. The metallurgical properties of the remelted ingot are really related to the solidification structure, which strongly depends on magnetohydrodynamic, thermal, and solidified behavior in the molten slag, liquid metal pool, and mushy zone."

Jan 1, 2014

By Xie Zhang, Jiang Diao, Xin Qiu, Lu Jiang, Bing Xie, Hong-Yi Li

"Duplex converter process, in which the first converter is used for removing phosphorus from hot metal (De-P), is an important way to produce low P-content and ultra-low P-content steels. In order to improve phosphorization removal and formation of slag with high basicity at relatively low temperature during dephosphorization converter process, effects of temperature, silicon content in hot metal and varied compositions of the De-P converter slag on phosphorus distribution between the slag and hot metal were investigated with thermodynamic calculations and by laboratory scale experiments in present work. Results showed that phosphorus distribution ratio between slag and metal was varied in 10.6~26.6 when basicity of the slag was in the range of 1.5~2.1 at 1370, and the distribution ratio was increased with increasing basicity and Fe10 content in the slag.IntroductionIt is known that phosphorus exists in steel in the form of solid solution, which can significantly improve strength and hardness of steel at room temperature. However, the plasticity and toughness of steel, especially the low temperature plasticity is sharply reduced and leads to high ductile-brittle transition temperature. This phenomenon is commonly known as cold brittleness of steel [1~3]. Hence, phosphorus should be removed as much as possible in the steelmaking process, because it is generally harmful to the iron and steel products."

Jan 1, 2013

By J. B. Cocanour

Pioneering work at the U.S. Bureau of Mines (USBM) has produced a personal computer (PC)-based, software-driven video photometric color sensor for real time process control of metallurgical streams. The video photometer is an inexpensive optical sensor which operates in the visual area of the electromagnetic spectrum and collects color information through plastic optical fiber. The red, green, and blue (R/G/B) voltage components of the color video signal are digitized and characterized through software and then presented as the control variable for software-based proportional-integral-differential (PID) control. This sensor has been successfully employed in the control of a laboratory copper electrolytic circuit. With this sensor, copper solutions were analyzed on-line without the need for sample removal, dilution, mixing or reagent addition, thereby allowing for the real time control of the circuit.

Jan 1, 1994

By Susanne Pignolet-Brandom

Fourteen samples of crushed Duluth Complex rock were characterized by the QEM?SEM automated scanning electron microscope image analysis system to evaluate the application of the system to mining waste rock characterization. The system can reliably distinguish the iron sulfides, the copper-iron sulfides and the nickel-iron sulfides. Calcite was distinguished from all other minerals except fluorite. The volumetric abundances were verified by comparing elemental abundances calculated using the QEM"SEM volumetric percentages and appropriate mineral compositions with elemental abundances determined by standard laboratory procedure. The pH and sulfate concentrations of rinse water from laboratory leach experiments correlated well with the mineralogical data.

Jan 1, 1989

By A. Schönecker, P. Y. Pichon, B. Kraaijveld, Y. Meteleva-Fischer

"Ribbon-growth-on-substrate is a casting method, which offers a possibility to control heat flow, nucleation and subsequent crystal growth at the liquid-substrate interface. This technology allows for low-cost and high throughput shaping of silicon sheets with controlled crystal grain size and orientation for use in solar cells. In this work, sheets of silicon- metal silicide composite materials were produced and their microstructure was studied. It was shown that depending on the relevant phase diagram and casting conditions, a micro/nano-sized eutectic structure of the casted sheet can be formed. Such composite materials possess properties promising for various applications in energy generation, storage and conservation. The advantages, potential and challenges of the ribbon-growth-on-substrate technique for production of composite sheet materials as well as novel areas of application for such materials are discussed.IntroductionThe Ribbon Growth on Substrates (RGS) process is well known in the solar industry as a process to produce multicrystalline silicon wafers. An industrial size pilot production line for continuous casting of silicon wafer was developed by RGS Development B.V. in the Netherlands (Figure 1). A comprehensive review of this technology and properties of the produced silicon wafers were reported by Schönecker et al [1]. The principle of the RGS process is explained in Figure 2. The relatively cold substrate extracts the crystallization heat from the liquid silicon in the casting frame. This results in the growth of a silicon ribbon (Vc) in contact with the substrate. When the substrate (Vp) is transported from the casting zone into the cooling section, the crystal growth stops, the wafer can be removed and the substrate can be re-used. Last few years large work was done on the industrialization and market development of RGS wafers for the solar industry. Part of this work was discussed by Schönecker et al [2]. Although there is still a good perspective on the middle and long term solar market for the RGS wafers, the current market situation was found to be unfavorable for new entrants."

Jan 1, 2014

By R. H. Hanewald

INMETCO, a subsidiary of Inco Limited, is the only facility in North America that provides High Temperature Metals Recovery for nickel-, chromium-, and iron-bearing wastes. Since 1978, this process has prevented more than 775,000 tons of materials from becoming part of the nation's waste stream. The paper describes Inco's experience in metals recovery, traces the development and explains the operation of the High Temperature Metals Recovery Process, and examines the procedures and criteria used to determine whether spent catalysts meet process feed specifications. An overview of the current requirements for transporting spent catalysts is provided. The paper concludes with brief case histories of catalysts users employing High Temperature Recovery to manage spent catalyst.

Jan 1, 1995

By Hongmin Zhu, Kai Huang, Shuqiang Jiao

"Garlic peel was used as the raw material to synthesize the biosorbent for the selective recovery of precious metals from the acid chloride solution. Garlic peel is rich in carboxyl-, amino- and thiol-groups, has the potential of exhibiting high affinity to Au(III) when appropriate chemical modification process was employed. Here in the present study, the biosorbent was prepared by cross-linking garlic peel particles with concentrated sulfuric acid. Adsorption tests for mixing different metal ions such as Au(III), Fe(III), Cu(II), Ni(II) and Zn(II) from various concentrations of hydrochloric acid media indicated that Au(III) was selectively adsorbed on the cross-linked garlic peel gel over the other coexisting base metal ions investigated. The crosslinking mechanism and selective adsorption of Au(III) were also investigated briefly.IntroductionPrecious metals are quite popularly applied in the modern industries such as jewelry, electronics and electrical devices, catalysts in chemical industry, etc. While their high values, limited deposit and quite large demand in industry makes its recovery from the industrial wastes, typically e-wastes, quite necessary. Actually, many techniques have been developed to recycle and recover the precious metals from various industrial wastes effectively in last decades, but the cleaning and ecofriendly processes are still seriously scarce [1]. Taking into account of the typical recovery processes using cyanide lixiviant in the alkaline media, or aqua regia, followed by the further recovery process using activated carbon adsorption or cementation with zinc, iron or aluminum plate or powder, though they both are quite effective recovery processes, if considering the special requirements on safety and ecofriendliness for the modern hydrometallurgical processes, various improved or novel extraction processes are greatly demanded [2]. Recently, the biosorption technology applied to the recover precious metals in the hydrometallurgical process has become a concern [3,4]. Inoue’s research group made great progress in the recovery of precious metals such as gold, palladium and platinum from the e-wastes such as spent mobile phone by using biosorption from the hydrochloric acid media [5,6]. This new hydrometallurgical process exhibits the prominent advantages of being cost-effective for its short process, easy operation and near-zero emission. In the above recycling process for e-wastes treatment, the preparation of biosorbents is the key and backbone of the whole recovery process. For this purpose, they developed a series of suitable sorbents for precious metals recovery by using the tanning-based or cellulose-based biomass such as persimmon peel, grape peel, orange juicing residue, waste cotton, waste paper through the crosslinking process with concentrated sulfuric acid and relative chemical modification processes [7-10]. In the present study, we also applied this technique to prepare the biosorbent of precious metal uptaking by using garlic peels as the raw materials, and investigated the adsorption properties of such-obtained gel in the hydrochloric acid media."

Jan 1, 2012

By Mark Kruzynski, Srinivas Garimella, James T. Wiswall

"A flue gas recirculation (FGR) system for a combustion fired aluminum melting furnace is experimentally investigated. The FGR system flows combustion air in a turbulent jet within the flue gas stream, and the turbulent jet flow is collected in a tube at a distance from the jet exit. Entrainment of the flue gases as well as heat transfer between the flue gases and the jet occurs over the length of the exposed jet. Heat transfer between the flue gases and the jet, and the amount of flue gas entrained into the jet (derived from temperature, flow rate and oxygen fraction measurements) were measured as a function of nozzle exit velocity and the distance between the nozzle exit and collection tube. In addition to flue gas entrainment, a fuel savings of up to 7%, due to heat transfer over the length of the jet, was projected from the measurements obtained.IntroductionFlue gas recirculation can be applied to aluminum melting furnaces to control combustion temperature. When coupled with a device to improve furnace efficiency by recovering heat from the furnace exhaust, flue gas recirculation provides a control technique that is integral to achieving the goals of reducing fuel consumption, increasing product yield, increasing the longevity of infrastructure, and reducing pollutant emissions. In particular, combustion temperature control can help reduce reactivity of the products of combustion with the molten metal surface and furnace refractory materials. Combustion temperature control can also help improve the life of heat exchangers used to recover energy lost to the environment in the flue gases, and reduce NOx formation in the combustion process. Flue gas recirculation can also dilute oxygen used in oxy-fuel combustion to reduce reactivity.Flue gas recirculation has been used since the 1970s to control flame temperatures in the automotive industry [1-3] and has successfully reduced NOx emissions. Many different flue gas recirculation approaches for high temperature melting such as melting aluminum and glass have been patented since the 1980s [4-12]. There has also been academic interest to determine the fundamental performance characteristics of flue gas recirculation in high temperature furnaces and in combustion [13-15]."

Jan 1, 2014

By Jinrong Zhang

Fresh cyanide solution was treated by near UV light with the assistance of photocatalysts. Cyanide was oxidized mainly to cyanate. Photochemical behavior of the anatase and rutile forms of TiO2 was compared. It is found that anatase has a much higher activity than that of rutile. Bubbling of oxygen in the reactor showed no appreciable increase in cyanide oxidation, implying that the reaction is surface controlling. A very interesting finding in this study is that a natural mineral, ilmenite, can replace chemical titanium dioxide as the photocatalyst. Ilmenite without any treatment did not catalyze the oxidation of cyanide. But, after being roasted at high temperature with oxygen, the oxidation was enhanced dramatically. The mechanisms of photooxidation of cyanide and the roasting of ilmenite are proposed.

Jan 1, 1991

By C. M. F. Vieira

The main characteristics and physical and mechanical properties of clays from the county of Campos dos Goytacazes, located at the northern part of the State of Rio de Janeiro, Brazil, are presented. The characterization included mineralogical composition, chemical composition and particle size distribution. The properties related to water absorption, linear shrinkage and flexural rupture strength were obtained in samples that were prepared by 20 MPa uniaxial pressing and fired at 950 and 1100oC. The results showed that the clays are predominantly kaolinitic with high percentage of clay minerals. The kaolinitic structure associated with a small amount of fluxes confers a refractory behavior which makes difficult the sinterization and impairs the ceramic consolidation.

Jan 1, 2009

By Mei-le He, Min Chen, Xiang Shen, Lei Xu, Lei Liu, Nan Wang, Xue-liang Yin

In the current study, Al2O3-MgO-CaO refractories were prepared at 1400-1600 by the addition of MnO micro-powders, and the effect of MnO addition on densification behavior of the refractory was discussed. The results showed that the doped MnO dissolved to MgAl2O4 phase, and promoted the growth of MgAl2O4 grains by the formation of MgAl2O4 solid solution. As a result, the dense microstructure was obtained, with the apparent porosity decreased from 19.2% to 5.4% and the bulk density increased from 2.78g/cm3 to 3.15g/cm3 after firing at 1600 for 2h by the addition of 4% MnO. In addition, a texture microstructure was observed, which is considered to be favorable to improve mechanical properties and the service life of Al2O3-MgO-CaO system refractories.

Jan 1, 2016

By Mingming Zhang, Marshall S. Coe, Marcelo W. Andrade

To supply iron units and flux burden in blast furnaces, sinter basicity is one of the vital parameters for sinter plants. The sinter basicity also plays an important role in sinter quality since it imparts the formation of different mineral phases in sinter. Pot-grate sintering tests were carried out with low and high basicity to investigate the effects of sinter basicity on sinter mineralogy, properties and productivity. It was found that with an increase in sinter basicity, both sinter productivity and reducibility (RI) increased. Tumbler index (TI) and low temperature degradation index (LTD) of high basicity sinter were comparable to low basicity sinter. Softening and melting tests showed that sinter with 3.5 C/S basicity had slightly higher softening temperature comparing to lower basicity sinter with C/S 2.6, acid and fluxed pellets. XRD analyses confirmed the formation of silico-ferrite of calcium and alumina (SFCA) and calcium ferrite (CF) in the tested sinter samples.

Jan 1, 2015

By Yong Hack Lee

Nonferrous smelting processes have been through a rapid transformation since the beginning of 1980. The copper smelting technology has changed from the conventional Blast Furnace process to the Flash Smelting and MIB process. In the field of lead smelting, the technology has changed from the Blast Furnace Smelting to the Direct Smelting such as QSL and KIVCET. In 1992, Onsan Refinery successfully commissioned Direct Smelting QSL technology for lead. The QSL could produce more than 160,000 ton per year of lead bullion from lead concentrate and various residues. Moreover, since the year 2000, the TSL (Top Submerged Lance) Technology utilizing the same Direct Smelting process has been successfully commissioned to treat lead concentrate as well as lead sulfate residue produced from a hydrometallurgical zinc plant. This paper presents and compares the energy flows of lead smelting processes such as a conventional process and the Direct Smelting Processes plotted on the Pb-O-S phase diagram. The oxygen potential diagram suggests how to control the oxygen potential in the furnace. Also, it describes the recent operational experience in the TSL plant of Onsan Refinery with necessary mass balance of key elements.

Jan 1, 2003

By Min Chen, Lei Xu, Liang-yu Jin, Xue-liang Yin

For the purpose to reduce the high cost and heat storage loss of Al2O3-MgO bricks used as ladle linings, Al2O3-MgO-CaO bricks with lower theoretical density were fabricated and the densification behavior as well as mechanical property of this refractory was investigated. With addition of CaO, the initial sintering temperature of Al2O3-MgO refractory was decreased from 1300 to 1100°C associated with the expansive formation of CA2, and the compressive strength was also enhanced owing to the formation of bond linkage between CA6 and spinel. At high temperature, brick with 4% CaO content showed poor sinterability with high porosity because of the formation of platelet structure of CA6 grains, whereas brick with 8% CaO content was well sintered with higher relative density but lower bulk density than Al2O3-MgO brick, indicating that the densification as well as lightweight of Al2O3-MgO refractory was effectively promoted.

Jan 1, 2015