Search Documents

By Snehanshu Pal

"Concrete understanding of fluid dynamics properties inside basic oxygen furnace (LD converter) and hot-metal surface deformation due to impinging oxygen jet is important for optimization of reaction kinetics and maximization of productivity and refractory lining life. In this study various k-å turbulence models and volume of fluid (VOF) method have been used to model fluid flow and interaction of impinging oxygen jet with hot metal for an industrial scale top blown LD converter.RNG, standard and realizable k-å turbulence models are used to study velocity magnitude, stream function, turbulence intensity profiles. Turbulence kinetic energy, turbulence eddy dissipation, velocity magnitude and probable mixing time have been calculated in three locations inside the converter.The average rate of oxygen jet penetration, location of vortex formation, centre line and superficial velocity of impinging oxygen jet, probability of emulsifícation are studied by VOF method.These simulation studies provide better understanding of phenomena inside LD converterIntroductionComputational fluid dynamics (CFD) modeling in the field of basic oxygen steelmaking can improve substantially the understanding of existing processes where investigation of liquid steel flow measurement is hardly possible due to the rough ambient circumstances. In order to reasonably predict gas stirring operations and emulsifícation, mass, momentum, energy transfer and dynamic interaction among ions, atoms, molecules in the bath, detailed information on flow patterns, fluid velocities, and turbulent properties is essential. Concrete understanding of bath fluid dynamics inside basic oxygen furnace is also important for optimization of reaction kinetics inside the bath and maximization of LD converter lining life."

Jan 1, 2012

By Eun Duck Park

The gold catalyst supported on iron oxide was prepared from gold dissolved in aqua regia by a deposition-precipitation method and applied to CO oxidation in the absence and presence of hydrogen. Some characterization methods such as X-ray diffraction (XRD), nitrogen adsorption, transmission electron microscopy (TEM), temperature programmed reduction (TPR), temperature programmed oxidation (TPO), and the pulsed CO chemisorption with temperature programmed desorption (TPD) were conducted to explain different catalytic activities of Au/Fe2O3 catalyst pretreated at different conditions. The particle size of gold was about 10 nm for Au/Fe2O3 calcined in air at 373 and 573 K. For complete CO oxidation, the decreasing CO conversion with a reaction time was observed at low temperatures but its initial catalytic activity can be restored by a heat treatment at high temperatures. This catalyst was quite active for the selective CO oxidation in the presence of hydrogen especially at low temperatures. In the presence of hydrogen, the deactivation was significantly diminished.

Jan 1, 2006

By G. S. Rao

Levitated drops of Fe-18%Cr-2%C were reacted with oxygen-argon mixtures to study the reactions that occur in the AOD process, where the gases are injected into the melt and form bubbles. In the laboratory an argon-oxygen pulse, followed by pure argon, was flowed past the levitated drop to simulate the transient conditions in the gas phase as the bubbles rise in the melt. Oxide layers formed on the drops immediately when they came into contact with gas pulses containing 75% or more oxygen. Once the oxygen flow had ceased, the oxides reacted with the carbon in the drops to form CO gas and eventually disappeared. The de-carburization reaction occurred without oxide formation when the gas contained 50% oxygen or less. Melts that were sampled after EAF tapping, ready to be charged into the AOD, showed a higher tendency to oxide formation and consequent carbon boil than pure ternary Fe-18%Cr-2%C alloys made in the laboratory. The actual steel samples contained significant impurities, such as 0.25% Si and 0.56% Mn. A similar effect of oxide-forming impurities had been observed previously with binary Fe-C alloys. Movies were taken of the oxide formation and decomposition, and the results will be presented, along with data on the experimental conditions, including temperature and oxide compositions. The results are important because they give an insight into the reaction mechanisms in the AOD, which must be understood in order to improve and model the process.

Jan 1, 2006

By Guo-hua Bai, Hong-jing Yuan, Qian Li, Yong-bin Yang, Tao Jiang, Yan Zhang

"The effect of different additives on the bio-oxidation of arsenic-bearing gold ores has been carried out to solve the problems such as long period of leaching, low oxidation rate. The oxidants strengthen the cathodic reaction and thus improve the leaching rate by the increase of electron transfer. Meanwhile, silver catalysis is also effective for the decomposition of arsenicbearing gold ores due to the strengthening of anode reaction. Co-intensification by oxidants and Ag (I) is more efficient to the bio-leaching and the conversion of As (III) because the anode and cathodic reaction of biological oxidation of sulphide ores were both strengthened. The leaching rate reached to 63.94% after bio-leaching 13days by co-intensification of Ag (I) and Fe(III).IntroductionWith the worsening global ecological problems and the gradual exhaustion of available gold resources, metallurgical technology of refractory gold ore has received more and more attention and become possible due to its good advantage of the economic effects and negative effects to the environment. Refractory gold ore, the direct cyanide leaching rate of that is defined as less than 70%, has become an important raw material in gold extraction industry, in which sulfide bearing gold ore represents a large proportion, pyrite and arsenopyrite (FeAsS) is a common gold-bearing mineral. Since the gold is often encapsulated in the crystal lattice of these minerals, destruction or alteration of the ore to liberate the submicron and/or structurally bond gold is necessary[l]. Even if the ultrafine grinding approach also is generally not sufficient for these refractory ores and additional techniques like roasting, pressure oxidation and bacterial oxidation are used to liberate the gold [2]. In the three pretreatment processes, bacterial oxidation is characterized by its new ideas, low cost, no pollution, simple equipment and operation, high leaching index and become the most promising process which has received much attention over time [3-5]. But its further application is limited by some of its own shortcomings, such as long pretreatment time and the toxic effects of arsenic to bacteria on bio-leaching limit."

Jan 1, 2013

By Srinath Viswanathan, Zhijing Zhang, Ramana G. Reddy

"The viscosity measurements were carried out on melts of 380 aluminum alloy containing 20 volume % SiC particulates under various shear rates at different temperatures using a Brookfield viscometer. Results showed that viscosities of the melts increased with decreasing temperature and decreased with increasing shear rate. These results were compared with those of 356 alloy and it was found that the temperature had a more significant effect on viscosity of 356 alloy than that of 380 alloy containing SiC particulates. Based on the present experimental data an empirical viscosity model, which considers the effects of both solid fractions in the melt and shear rate, is proposed.IntroductionDiscontinuously reinforced metal matrix composites materials (MMCs) such as aluminum alloy containing SiC particulates have considerable potential for applications in the automotive industry because of their superior stiffness, higher specific mechanical properties, better dimensional stability and strength retention at elevated temperatures when compared to their monolithic counterparts. They have a great advantage in the specificity of their properties, meaning that specific materials can be engineered for specific applications. With such freedom of design, materials engineers have to accumulate a very large database of mechanical properties. Among these properties, the viscosity of alloy slurries is very important for producing, casting and forming process of metal matrix composites materials because viscosity has a decisive influence on fluid flow. The understanding of the rheological behavior of alloy slurries is necessary for these materials to become economic reality. Therefore, a study was carried out to measure the viscosities of 380 aluminum alloy containing 20 volume % SiC particulates under various shear rates and temperatures. In addition, a viscosity model representing the primary features of the alloy slurries was developed."

Jan 1, 1999

By Tim B. Vanderwood

The mineralogy of dusts from several locations in a lead smelting plant, remotely collected dusts and soils near the lead smelter, and dusts from a secondary copper smelter were examined by reflected light microscopy (RLM) to determine their m1neralogy, texture, and origins. Individual grams were further analyzed by microbeam techniques. Detailed petrographic analysis of the dust has been supplemented by automated scanning electron microscopy combined with energy dispersive x-ray spectroscopy (ASEM-EDS). This technique allows the rapid sizing and chemical analysis of thousands of individual particles in a dust sample, producing particle size distributions as well as statistically meaningful breakdown of a sample into chemical types (e.g., proportion of galena vs chalcopyrite).

Jan 1, 1992

By Marco Olper

Zinc bearing materials containing chlorides and fluorides of alkali metals, such as EAF dust, Waelz oxides, galvanizing ashes, zinc & brass foundry fumes and converter fumes are little attractive, both technically and economically for processing in ISF plant or in a conventional zinc sulphate electrolysis works. The Ezinexm Process allows for the recovery of high purity zinc in cathode form, from these materials, regenerating the leaching liquor. The process is based on a new electrochemical system which depolarizes the anode reaction with reduction of the cell voltage, compared with the traditional sulphate electrolysis method. The electrolyte, based on a chloroamrnino complex, allows for the recovery of other valued metals present in the zinc bearing materials such as lead, copper and silver, these being recovered as a metallic cement consequently improving the economics of the process.

Jan 1, 1994

By Lztok Peruš, Goran Kugler, Matevz Fazarinc, Milan Tercel

"Hot deformability of M42 tool steel additionally alloyed with cobalt and molybdenum was investigated. Hot-compression tests were carried out in the temperature range 850 °C -1200 °C, at strain rates range 0.001--6s-l up to strain of0.9. Field-emission scanning electron microscope and optical microscopy were used for characterization of microstructure of deformed samples, which revealed a very complex precipitation of carbides that strongly depends on the soaking temperature, the soaking time, the stress state, the deformation temperature as well as on the strain rate. Gathered data was used to calculate the processing parameters such as process maps, apparent activation energies and strain hardening exponents. For better understanding of thermodynamical properties of the studied steel a simultaneous thermal analysis was conducted. Furthermore the analysis of phase equilibrium was calculated using Thermo-Cale software. On the basis of these studies the optimal soaking temperature and process windows were determined.IntroductionHot workability ofledeburitic tool steels is important economic factor. This means that for each tool steel individuallysafe range of hot working parameters should be revealed. Publications in the literature with regard to the hot workability of tool steels are rare and therefore more information from this research area is desired.The relatively low hot workability of ledeburitic tool steels, i.e. steels in which the solidification is completed by a eutectic transformation of the residual interdendritic liquid to austenite and various alloy carbides (ledeburitic carbides), is usually characterized by the production of surface and internal cracks during the hot deformation."

Jan 1, 2013

By Samuel Senanu, Benjamin Agyei-Tuffour, Lifeng Zhang, Eivind Øvrelid, Adegboyega Nathaniel Femi

"The solar grade silicon ingot produced from directional solidification process usually pushes the impurities to the top and finally cut off and discarded, which leads to material loss. The hard inclusions lead to wire breakages during the cutting of the ingot in wafers. The main kinds of inclusions found in solar grade silicon have been investigated using vacuum filtration: needle-like Si3N4 and lumpy SiC inclusions. Clusters of SiC inclusions and Si3N4 are also found. Surface observations of the scraps before polishing reveals that Si3N4 inclusions are usually bigger and in some cases can be about a few millimeters. SiC inclusions are usually smaller, ~200µm but can be ~500µm in some cases. Inclusions observed after filtration are mainly SiC with diameters ~10µm. Through the vacuum filtration, 99% inclusions can be removed 99%. The possible mechanisms of filtration are cake filtration for the larger sized Si3N4 and SiC inclusions and deep-bed filtration the SiC inclusions. For the directional solidified silicon ingot, an approximate distance of ~10mm gave an encouraging cutoff thickness. The inclusions sizes were below 10µm. Introduction The search for an alternative source of energy to fossil fuel has led to a dramatic increase in the demand for solar energy due to its high dependability (abundant in nature) and environmental friendliness 1). During the last 5 to 10 years, the annual worldwide production of solar cell by the photovoltaic industry has increased to an annual rate of 30 to 40 percent 2). A necessary condition for the maintenance and even an increase of this growth rate is a decrease in the cost of feedstock for the solar cell production 1). The total international production in 1997 was 130 MW worth more than $500 million. In 2004 the consolidated world total production of PV cells increased to 1146 MW or around. $7 billion (Figure 1) 3). Silicon is currently the most dominant semiconductor material used in the PV industry. As shown in Figure 2 3), solar cells consist of two types of material, often the p-type and n-type silicon. Light of certain wavelengths are able to ionize the atoms in the silicon (causing atoms to either gain or lose electrons) and the internal field produced by the junction separates some of the positive charges (“holes”) from the negative charges (electrons) within the photovoltaic device. The holes are swept into the positive or p-layer and the electrons are swept into the negative or n-layer. Although these opposite charges are attracted to each other, most of them can only recombine by passing through an external circuit outside the material because of the internal potential energy barrier. Therefore if a circuit is made, power can be produced from the cells under light because the free electrons pass through the load to recombine with the positive holes."

Jan 1, 2008

By Robert W. Bartlett

"Bioheap pretreatment of sulfidic refractory gold ore prior to cyanide leaching is a promising new technology, especially for low-grade ores that cannot afford to be oxidized by pressure leaching or roasting. When an ore contains both refractory and non-refractory (oxidized) gold, an economic decision must be made whether, or not, to pretreat before cyanide leaching. This choice is more complex than the familiar ore/waste cut-off grade decision. Pretreatment usually increases recovery but delays receiving revenue. Based on choosing the processing route that maximizes the present value of the ore, an equation is developed that computes a ""critical cyanide leachable gold grade"" for determining whether pretreating will be profitable. If the ore's actual cyanide leachable grade, without pretreatment, is above this ""critical grade,"" it will not pay to pretreat. The waste/ore cut-off grade, pretreatment yield (leachable grade after pretreatment), total gold grade, pretreatment operating cost and the project's financial discount rate are parameters in the equation. Results of example calculations are provided. This equation can be used for mine development planning and, when bioheap pretreatment is an available option, for daily operating decisions on individual ore blocks.IntroductionOres that are refractory because of sulfide mineral encapsulation of microscopic gold are becoming important. These ores must be pretreated to oxidize the sulfides to liberate the gold prior to cyanide leaching. The conventional pretreatment process technologies are pressure leaching with oxygen and two-stage fluid bed roasting. However, low-grade refractory ores cannot afford the high operating costs of these processes. And, small mines with limited reserves cannot justify the high capital costs of these processes."

Jan 1, 1997

By Edouard Asselin, Guikuan Yue

"In the present study, electrochemical measurements, especially cathodic potentiodynamic polarization (CPC) and cyclic potentiodynamic polarization (CPP), have been employed to study the kinetics of ferric reduction on chalcopyrite in aqueous Fe( II )-Fe(III)-H2S04 solution at 25°C and 70 °C. Results from the calculation ofspeciation in the above solution reveal that, at both 25 °C and 70 °C, the real Fe3+/Fe2+ ratio is much lower than the nominal ratio, which leads to smaller values for the reversible potential of the ferric/ferrous couple based on the Nemst equation. Exchange current densities of the ferric/ferrous couple were obtained by extrapolating the cathodic linear Tafel line to the reversible potential and are on the order of 10-7·10-6 A/cm2 at 25°C and 10·6-10-5 A/cm2 at 70 °C, respectively. The transfer coefficients were about 0.35-0.38 at 25°C and 0.35-0.45 at 70 °C. Polarization plots of CPC and CPP under different nominal Fe3+/Fe2+ ratios are in good agreement at 25 ·c and at 70 °C. Based on the obtained exchange current densities, the rate constant k, was calculated and is on the order of 10-1 cm/s at 25 °C and 10 1 cm/s at 70 °C.IntroductionChalcopyrite is the most abundant copper mineral in nature, accounting for about 70% of copper reserves in the world [I]. In recent years, the metallurgical industry has been searching for a hydrometallurgical process as an alternative to pyrometallurgical treatment due to high emissions of S02 and capital costs associated with smelting. Activity in this area has increased recently due to some inherent advantages associated with hydrometallurgical processing, such as the possibility of treating low-grade ores (increasingly more abundant in the case of copper) and easier control of waste, with the attendant benefits to the environment [I]. Chalcopyrite is highly refractory under most hydrometallurgical conditions, owing to the formation of an anodic passivation layer on the chalcopyrite surface which renders the process kinetics very slow. Most of the currently proposed processes are based on sulfuric acid with ferric ions and/or dissolved oxygen as oxidants. Sulfuric acid is preferred over all other leaching reagents in terms of cost, environmental friendliness, and ease of its regeneration during electro-winning. Some of these processes have been piloted in attempts to implement these technologies on an industrial scale,"

Jan 1, 2012

By M. Drozd

Multi-use pad operators require an efficient and economic method to destroy cyanide in their process residues so new material can be stored on the pad and leached. Operators of the dedicated or single-use pads require an effective cyanide destruction method for pad closure. Cyanide destruction can be accomplished by utilizing oxidants such as hydrogen peroxide or calcium hypochlorite, or by utilizing ferrous sulfate which sequesters the cyanide in strong acid dissociable complex. Ferrous sulfate can be the preferred method of cyanide destruction because it is a less costly chemical, reaction rates are almost immediate and unlike oxidants, it can penetrate the total depth of a pile without being destroyed by side reactions. Literature indicates that the (Fe(CN)6)-4 com~lex is produced slowly but it appears that complexes such as Fe(CN)4(H20)2-or Fe(CN)4(OH)2)-4, are formed quickly and should have no U.V. sensitifity, unlike (Fe(CN)6)-4. Stoichiometry of the testwork indicates that Fe«CN)4(OH)2)-4 complex may be the species formed. The usage of ferrous sulfate has the advantage of being able to bring ~ level down that divalent metal ions such as Cu++, Cd++, Hg++, Pb++ and Zn will form insoluble complexes and precipitate from solutions does not destroy weak acid dissolvable complexes and can leave a heavy metal problem behind after cyanide destruction.

Jan 1, 1990

By Xiancong Zhao, Hao Bai, Qi Shi, Zhancheng Guo

Reducing electricity cost is important for energy intensive industries such as the iron and steel industry. With the implementation of time-of-use (TOU) electricity price, plenty of attention has been paid to the optimal management of byproduct gases. The time-of-use (TOU) electricity price is the practice of implementing different prices for different times of use. It is possible to reduce electricity cost by adjusting the amount of product gases stored or used for power generation throughout the day. In this paper, a novel mixed integer linear programming (MILP) model concerning the TOU electricity price is proposed to optimize byproduct gas use. Compared with previous models, this model considers the optimal load shift between gasholders and boilers under TOU electricity price. The case study of a steel plant demonstrates that the electricity purchase cost can be reduced by more than 30% after optimization.

Jan 1, 2016

By Muhlis Nezihi Saridede, Burak Birol

"Plastic wastes become a huge problem day after day due to the growth of plastic industry. Hence, plastic wastes are used as a raw material for other industries to eliminate this problem. Polyethylene Terephthalate (PET), which is a commonly used for plastic bottles, may be used as a reductant for iron production because of its C and H content. In this study, composite pellets containing iron ore concentrate, flux and reductant were prepared. Crystallized PET bottles and coke were used as reductant after ground. The prepared pellets were reduced at 1400°C for 30 min. and iron nuggets were produced successfully. Usage of waste PET purely as reductant in composite pellets gives a higher metallization degree and proper carbon content than coke or PET and coke mixture.IntroductionPlastics can be seen everywhere, especially at packaging industry in our common life. The increase of plastic usage ends up with an important problem, the increase of plastic wastes. Many studies have been carried out about usage of plastics as reductant in blast furnace such as Ogaki et al.[1], Heo and Baek [2], Saridede [3], Minoru et al.[4], etc. Besides, Kato et al. [5], Nomura and Kato [ 6] and Rongfang et al. [7] have pointed out the use of plastics in coke ovens regarding to its calorific content. In EAF steelmaking, a mixture of coal/coke and plastics can be used as an energy resource instead of only coal or coke. [8] Also, the usage of PET and PC in self-reducing composite pellets increased the reduction rate. [12]PET (Polyethylene terephthalate ), which is commonly used for soft drink plastic bottles, is an important municipal waste due to its C and H content. Its molecular formula is (C10H8O 4)n. Demir and Dincer showed that PET can be crystallized at 250°C to have the ability to be ground to a size of -100 µm. [11]"

Jan 1, 2011

By David G. Dixon, Ahmad Ghahremaninezhad, Edouard Asselin

"In this study pertaining to the electrochemistry of chalcopyrite, the active/passive behavior of a chalcopyrite electrode in 0.5M sulfuric acid solution was investigated. Potentiostatic and potentiodynamic polarization and multi-cyclic voltanunetry were conducted to analyze the electrodissolution parameters of the electrode.The potentiodynamic and potentiostatic polarizations of chalcopyrite revealed the formation of a passive film on the surface of chalcopyrite. From the potentiostatic study in the passive potential region, a decrease in the dissolution current density by increasing the potential was observed. From this, it was concluded that the passive film is an n-type semiconductor and cation interstitial defects or anion vacancies are the charge carriers. From multi-cyclic voltammetry studies, four cathodic peaks at - 0.37, 0.30, -0.10 and-0.20 YsHE were detected on the surface of a passivated chalcopyrite electrode. The cathodic peaks at 0.37 and 0.30 V were connected to ferric to ferrous reduction and copper sulfide formation, respectively. The peaks at -0.10 and - 0.20 were related to chalcopyrite reduction. The products of the chalcopyrite reduction reactions were suggested to be Cu2S, Cu9fesS16 and Cu5feS4 and evolution of hydrogen sulfide gas (H2S).IntroductionChalcopyrite is the most abundant copper bearing mineral in the world and its dissolution behavior represents the most important technological consideration in the hydrometallurgical extraction of copper [I]. Since the current pyrometallurgical methods for copper extraction from chalcopyrite have environmental issues, many studies have considered the leaching and dissolution of CuFeS2 in different aqueous media [2-5]. The main problem associated with leaching processes is the slow dissolution rate of the mineral [6]. During the dissolution process, increasing the potential of the chalcopyrite in the anodic direction will cause the formation of surface layers which hinder the dissolution rate of the mineral [7]. The precise composition of the layers is in dispute. Previous studies have concluded that these layers could be sulfur [8-9], precipitated iron compounds [8], a solid electrolyte interphase (SEI) - which slows the rate of electron transfer- [10], a metal deficient sulfide [ll], or polysulfidic in nature [12-13]. In order to increase the leaching kinetics of chalcopyrite, the characterization of the layers formed during dissolution is essential and electrochemical methods are important to this end. Studies by Biegler [14] show nucleation and growth of a thin two-dimensional sulfide phase on the surface of chalcopyrite during the exposure of a polished sample in HzS04 solution or air. More studies by Biegler and Swift [15] have shown evidence for nucleation and growth of a 3-dimensional phase at low anodic potentials (around 200 mV vs. OCP). The current-time behavior of the dissolution process in this potential area has the characteristics of expansion and overlap of localized dissolution centers."

Jan 1, 2012

By Ozgul Dere Ozdemir, Muge Sari Yilmaz, Sabriye Piskin, Deren Sibel Kasap

"Galvanic sludge is generated at the end of the waste water treatment process of metal plating system. The waste sludge is one of the main hazardous solid wastes produced by metallurgical industries. It is caused the harm of human health and damage of the environment due to containing reasonable amounts of toxic metals (e.g., nickel, zinc, copper, chromium, iron, lead, cadmium, etc). The concentration of those toxic metals in the wastewater might reach 30% (w/w, dry weight) making their removal and recovery an interesting issue.In this study, synthesized titanium dioxide is used as adsorbent to remove nickel in leachate of galvanic sludge. The adsorption experiments were carried out isothermally at four different temperatures. The effects of pH, temperature, and contact time on nickel adsorption efficiency were investigated, and the optimum parameters were determined from the experimental studies. The experimental results indicated that pH, temperature, and contact time played a significant role on the adsorption capacity of nickel.IntroductionRapid industrialization has caused increasing the heavy metal concentration in biosphere with the industrial wastes. These wastes are generated in various industrial processes such as electroplating. Galvanic sludge is a hazardous waste that generates from metal plating industry by chemical precipitation of heavy metals from acidic or alkaline solutions during the waste water treatment process. Heavy metals are tend to bioaccumulate thus they are treated the living organism [1-2].Galvanic sludge is mainly disposed on landfills for these reason it is a big problem for environment. Galvanic sludge containing nickel (II) is common because nickel (II) is used in electroplating process [3]. In drinking water, nickel may cause health problems if found in amounts greater than the health standard set (MCLG: 0.1 mg/L) by the United States Environmental Protection Agency (EPA). The higher concentration of nickel (II) in ingested water may cause severe damage to lungs, kidneys, gastrointestinal distress, e.g., nausea, vomiting, diarrhea, pulmonary fibrosis, renal edema, and skin dermatitis [ 4]. For these reasons, it must be treated before disposed to landfill."

Jan 1, 2011

By Andrzej Warczok

Liquid slags produced in smelting of copper concentrates contain copper in a dissolved form as well as mechanically entrained inclusions of copper matte. Coalescence and sedimentation of inclusions during slag cleaning plays a key role in copper recovery. Liquid matte inclusion in a molten slag presents a system of metallic conductor in an ionic solution. Constant electric field induces migration of the matte droplet along the current lines. Additional phenomena occur in a system under crossed electric and magnetic fields. Electromagnetic buoyancy force acting on the inclusion affects its settling rate. Electromagnetic buoyancy force of insulating and metal spheres has been measured in a liquid synthetic slag. It was found that depolarisation of the metal sphere, related to the electrode reactions occurring in the surface, plays an important role in the determination of the direction and magnitude of the electromagnetic force. On the basis of the existing theories and results of measurements a mathematical model describing the behaviour of metallic inclusions in the liquid slag under the influence of crossed electric and magnetic fields was developed. Simulation of behaviour of copper matte inclusions under crossed fields showed trajectory of motion in a liquid slag as a function of the slag properties and the inclusion size.

Jan 1, 2003

By Jing Zhan, Gui Li, Wei-feng Li, Li-Hua Jiang, Chuan-fu Zhang, Jian-yang Hwang

Thermodynamics analysis for processing the charge with lead concentrate and lead sulfate-containing materials in bottom blowing smelting furnace was conducted. The results show that the technology of large-scale processing PbSO4- containing materials with PbS concentrate in bottom blowing furnace under the condition of using high-iron slag type, batch heat supplement, high temperature and rich oxygen is thermodynamically feasible. The exploration test and industrial experiment confirm the results. When S content in mixed ore is 16~17% with coke foam content of about 5%, the lead paste amount can be increased up to 40%.

Jan 1, 2015

By T. L. Baum

External oxidation during in-line heat treatment of TRIP steels can cause problems for the subsequent coating process. This research aims to elucidate the kinetic rates of internal oxidation, external oxidation and decarburization and their interdependence under different gas atmospheres and temperatures. A rolled steel sample chemistry of 0.14 wt.% C, 1.8 wt% Mn, 0.6 wt.% Si and 1 wt.% Al is used as a case study. Thermogravimetric techniques are used to examine the net mass change in a sample during heat treatment and the results show an initial mass decrease and later an increase for particular partial pressures of H2O. SEM-EDS, optical microscopy and glancing-angle x-ray are used to quantify the microstructure. The cross-section of the samples have 4 distinct zones: (i) an external scale, rich in fayalite, (ii) an internally oxidized region with Al, Si and Mn oxides in an Fe matrix, (iii) a decarburized steel region, characterized by large ferrite grains and low carbon content, and (iv) a relatively unaffected steel core with a structure similar to the starting material.

Jan 1, 2006

By Jr. Robison

"Aluminothermic (""thermite"") smelting became commercial with the development of tonnage aluminum, and prospered producing metals and alloys with higher cleanliness, consistency and elemental control than competing technologies. We explore the scope of thermite smelting, and metallothermic smelting in general; the thermochemistry of the process; and its advantages and limitations as applied to industrial production. We review currently-produced products of thermite smelting in several forms and a wide range of heat sizes. As these products serve several industries, we relate the demands of those industries to the requirements imposed on the thermite process, leading to process dynamics and mechanisms to control/alter those dynamics. We review ways to lower the process costs by altering process stoichiometry, using other energy sources and utilizing less costly materials while considering effects on product quality and customer requirements. Finally, we examine overall emissions control and waste disposal.IntroductionAluminothermic smelting is the reduction of various oxides by aluminum to produce metals or alloys with varying levels of residual aluminum. One of the earliest uses of the process was the production of liquid iron to weld railroad rails, later modified in ""thermite grenades"" used to ""spike"" artillery pieces in World War II. Then during the 50's, 60's and 70's the growth of jet aircraft created a demand for new superalloys and titanium alloys, both requiring master alloys for efficient production. Aluminothermic smelting grew with the aerospace industry and with the expansion of microalloyed steels. It is very much a niche industry, dependent on the specialized demands of the specialty steel, superalloy and titanium industries. In this paper we introduce the characteristics of aluminothermic smelting, the scope of smelting operations, the markets served, and the environmental aspects of the process, as seen through the eyes of a company using aluminothermic smelting for over fifty years"

Jan 1, 2012