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By Guo Xueyi

The dissolution behaviors of valuable metals, lead and zinc, from secondary fly ash generated in municipal incineration plants were investigated using some lixiviants: sulfuric and hydrochloric acids, acetic acid and some chelating reagents including L-asparaginic-N,N-diacetic acid (ASDA), a biodegradable, and therefore, environmentally benign novel chelating reagent. It was found that zinc exists mainly as ZnO, whereas Pb probably as PbOHCI and PbO, and the easily soluble components in SFA are KCI and NaCl. Suitable amount of HCI can dissolve all of lead and zinc from SFA. Sulfuric acid can selectively extract zinc leaving lead in the residue. Ethylenediaminetetraacetic acid (EDTA) is an effective chelating reagent to extract both zinc and lead. Although ASDA and diethylene¬triaminepentaacetic acid (DTPA) can selectively extract more than half of lead from SFA, it would by no means be regarded as highly effective reagents for the extraction of these metal values. Keywords: Lead, Zinc, Secondary fly ash, Leaching, Dissolution

Jan 1, 2002

By M. K. Mohan

During the processing of metals like Cu, Ni, Co, large quantities of solutions, which contain co- products such as Sb, Cd, Pb etc. are generated. These solutions if processed to recover the metals help in conservation of metals as well as environment preservation. The present study was taken up to recover antimony from process solutions using zeolites. The effect of pH of the solution, time and type of zeolite viz., chabazite, mordenite, erionite and clinoptilolite on the sorption of antimony was investigated. Rate of sorption increases with pH and about 77-pct. antimony sorption was observed with chabazite at a pH of 6. Optimal conditions were established for the maximum recovery of antimony fiom process solutions. The mechanism of sorption for Sb was proposed in terms of adsorption and intraparticle diffusion. The calculated adsorption constants from Langmuir and Freundlich equations indicated that the adsorption of antimony on chabazite was strong.

Jan 1, 1999

By Cheryl S. Lim

New technologies such as direct reduction and smelting reduction processes are increasingly being used in iron-making and steel-making in addition to conventional blast furnace technology. Critical parameters for control of these processes include the degree of metallization, degree of pre-reduction, and carbon and silica levels. On-line monitoring of these parameters is difficult because measurements often need to be made on hot ores (at or higher than -1000'C) in circumstances where representative sample streams are not readily accessible. A nuclear analyser has been developed which provides continuous, non¬intrusive, real-time measurements of iron, oxygen, carbon and silicon levels in hot ores undergoing reduction. The analyser has been tested in a plant using a direct smelting process on pre-reduced feed to the smelting vessel-, accuracies of 1% relative, 0.5 w'.96 (25% relative) and 1.0 wt.% (9% relative) were obtained for the degree of pre-reduction, carbon and silica respectively. The underlying method, capabilities and potential applications of the analyser will be discussed.

Jan 1, 2001

By Nils Eivind Kamfjord, Mari K. Næss, Halvard Tveit, Edin H. Myrhaug

"As a part of the FUME research programme being done by the Norwegian Ferroalloy Research Association (FFF), the SINTEF Group and NTNU, several measurements towards quantifying the gaseous and solid emissions from the draining of the silicon furnaces for metal have been carried out.Based on the measured size distribution of the formed fume particles and known particle growth theory, an estimate of the growth time for the given particles has been calculated. The formation time for the measured NO amount has also been calculated based on the fume measurements and a thermodynamic model of the furnace gases combusting with air. The two “formation” times are in the same order of magnitude and they are therefore used as parameters in a CFD model, modelling that the formed fume particles are heating up the surrounding air and thereby forming NO according to the Zeldovich mechanism. The measurements show an approximately equal constant NO formation per fume particle. The CFD model shows results in the same order of magnitude, supporting that the particle growth and NO formation happen under near stoichiometric conditions and are controlled by the formation of SiO2 fume.IntroductionNOx is the common notion for the two gases nitric oxide (NO) and nitrogen dioxide (NO2) formed during combustion of fuels. The main sources for human made NOx emissions is on-/offshore transportation industry, power generations based on fossil fuels, agriculture and other industries [1]."

Jan 1, 2012

By J. S. Pitsillos

A new furnace tapping technique involving the simulation of a control valve at the exit to a furnace is being investigated. The purpose of this new tapping technique is to regulate the flowrate of liquid furnace products( slags, metals and mattes). Numerical modelling and experimental work has been carried out on tapping of slags leaving a SIROSMELT reactor and the results found to be in good agreement. Numerical modelling has also enabled prediction of the important industrial conditions for the onset of blockage from the shape of the pressure versus flowrate curves. Slag launder experiments have been carried out and a one-dimensional heat transfer model was used to evaluate the effectiveness of launder covers and different coolants. From the experimental results and mathematical model some launder design guidelines such as inclination angle, covers and coolants have been developed.

Jan 1, 1991

By Hsi-keng Hu

"This paper deals with the flotability of stibnite and summarizes the major experiences and technological innovations of some typical practices of antimony sulfide ores in China. Experiences of cyanide-free and -less flotation of complex antimony sulfide ores and the application of the heavy media process to the preconcentration are described.Performance improvements obtained by innovations in operating techniques are also outlined and discussed. Technical innovations involve: (1) ramification roughing and differential-rate cleaning of stibnite-arsanopyrite ore; (2) the application of the new flotation reagent system; (3) process of separation flotation of Sb-Hg bulk concentrate; (4) extraction of gold from Au-Sb bulk concentrate; (5) flotation recovery of coarse stibnite particles.IntroductionChina is rich in natural resources of antimony and is one of the major antimony producers in the world. During the past several decades, a lot of research works have been done and many experiences in milling practices were gained, some of which are summarized briefly as follows.I. Heavy Media separation of Antimony sulfide Ore at Xikuangshan Hill, Hunan province (1)HMS as a technique of preconcentration of antimony ore has been performed more than ten years in China with good results.1. Ore characteristics The antimony ore of Xikuangshan belongs to the epithermal- metasomatic-filled doposit of antimony sulfide. Major minerals are stibnite (92.1%), antimony oxides (7.9%) and a small amount of pyrite and pyrrhotite; the gangue minerals are quartz, silicic limestone, calcite, hydrous kaolin, sericite, barite and others. The specific gravity of the ore is 2.8 and the specific gravity of stibnite and gangue are 4.6 and 2.654, respectively."

Jan 1, 1988

By V. J. Ramirez, A. M. E. Noguez, M. J. Navarrete, B. G. Salas, N. T. Robert

"The close die forging stress in truncated conical cavities is evaluated with dimensional analysis. Five dimensionless groups are proposed from the process variables in order to simplify the forging stress determination. These groups are experimentally related and graphically expressed. This methodology can be used to predict the actual forging stress in industrial close die forgingThe use of the dimensionless groups allow to comprise more cases than the presented here, provided similar geometries and operational conditions.Introduction.Closed die forging is essentially a plastic deformation inside a two piece mold (forging die) with the inverted shape of the actual forging geometry. This plastic deformation will always be the result of a compressive stress. There are theoretical models which include complex calculations for the analytical determination of stresses (1, 2, 3, 4). Results of these calculations are approximate, requiring generally ulterior tests to obtain the true operational conditions(5).In this paper, it is presented a simplified approach to the actual compression stress needed in the forging. A well known tool in engineering: the Buckingham's Pi theorem in conjunction with dimensionless groups and a working piece scale model is used. Dimensional analysis will give the dimensionless terms needed to experiment with a selected scale model geometry to make the stress determination. The results presented demonstrate the reliability of this methodology."

Jan 1, 1997

By P. Myllykoski, J. Nylander

"A commercial program package called Crownoff for the simulation of temper rolling in four high mills has been verified against measured data. The agreement between measured and calculated transversal strain distributions of the strip was found to be good. Effects of the strip crown and work roll bending force on the strain distribution were simulated. The results showed that when a single ground camber of work rolls is used for all strip widths; the strip crown should be parabolic, excluding the edge drop. An increase or decrease of the strip crown by 30 % during a coil can be compensated by a 2 to 5 t change in the work roll bending force. The ability to control the strip crown by work roll bending was insensitive to strip width. IntroductionCold rolled steel strips are usually temper rolled after recrystallization annealing, which follows cold rolling. The purpose of temper rolling is to suppress the yield point, finish the strip surface and correct possible flatness errors. The presence of a yield point might otherwise cause problems during subsequent forming processes. The in homogenous yielding in non-temper rolled steels leads to the formation of Lüders bands in the strip surface.The rolling force is influenced by the rolling speed and changes in frictional conditions in the roll bite. Therefore it is very important to plan carefully the mill settings and control algorithms during rolling. The purpose of mill control algorithms is to ensure constant reduction and the best possible strip flatness during the entire coil.Correctly predicting the rolling force is important for determining the mill presettings. Torque, forward slip and power requirements are not usually critical, if the reductions are small. However, the large elastic deformations occurring in the roll bite make the physical description of the process difficult. Physical rolling models developed for cold rolling contain assumptions that lose their validity as the reductions decrease to the level of one per cent."

Jan 1, 1994

By Miguel Barron

Recently, a new lance design for BOF steelmaking has been proposed in the literature. This lance, in addition to six peripheral inclined supersonic nozzles, contains a vertical centered nozzle whose oxygen flow is independent from the main oxygen supply. The above authors affirm that their lance maximizes the droplet generation without causing spitting. In this work, the performance of a lance with four peripheral nozzles and one vertical centered nozzle is numerically modeled by means of Computational Fluid Dynamics software. Transient two dimensional computer simulations were carried out considering two phases, namely molten steel and gaseous oxygen. Numerical results confirm that bath agitation and droplet generation are enhanced as a result of the vertical centered nozzle, however a proper performance of this lance, related to a conventional one, strongly depends on the Mach number of the oxygen jets and the lance height.

Jan 1, 2008

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 V. Jiricny

There is a growing need to process galvanized steel scrap from automobiles, etc., in order to remove the zinc coating that otherwise causes problems in remelting of the scrap in electric arc furnaces. One approach that has moved to the pilot plant stage is that of Metal Recovery Technologies, Inc., of East Chicago (MRI). That company leaches the zinc fiom the scrap with a sodium hydroxide solution. The leached and washed scrap can then be returned to the steel industry. What is left is a sodium hydroxidelzincate solution which must be processed to recover the zinc and the NaOH. Presently, this is done by MRI using electrodeposition on planar electrodes at moderate current density and the resulting zinc is in the form of fine powder which is hard to process into, say, zinc for galvanizing. MRI has supported an investigation of a novel electrode, the spouted bed electrode (SBE), for zinc electrodeposition. In laboratory cells, zinc particles with low porosity have been grown up to 3mm in size. Microanalysis of the deposited zinc showed low level of impurities. DC energy consumption values were usually in the range of 2-2.5 kWg which is well below the energy consumption of the existing cells (and of present-day cells for electrowinning from acid sulfate electrolytes). These results were achieved at current densities (few thousand A/m2) that are much higher than possible with conventional electrodes. Discussion is provided of the scale-up of the cell to a commercial scale.

Jan 1, 1998

By K. M. Parida

The kinetics of dissolution of manganese dioxide in dilute sulphuric acid solution have been investigated using iron pyrites as a reductant. The dissolution rate of manganese is independent of the speed stirring but depends upon temperature, particle size, specific surface area of manganese ore, acid concentration, Fe(II) concentration and amount of pyrite. The activation energy is 43.6 KJ/mol and the linear relationship between the rate of dissolution and lido indicates that the reaction is chemically-controlled. The redox reactions of MnO2 with iron pyrites and Fe(II) are the rate-controlling reactions.

Jan 1, 1990

By Luis M. Chia

The direct dissolution of zinc in an organic solution of di-(2-ethylhexyl) phosphoric acid (D2EHPA) and kerosene was studied. The objective was to gain a better understanding of the fundamentals involved in the anodic step of the galvanic stripping process. Results showed that metallic zinc does dissolve spontaneously at ambient temperature by an electrochemical mechanism and the presence of additional oxygen activated the process. When oxygen was removed by prior nitrogen sparging, dissolution did not occur indicating a depolarizing cathodic reaction is necessary. The concentration of water in the organic also affected the rate of dissolution. A factorially designed experiment was made using four variables at two levels selected by evaluating results from previous screening tests. D2EHPA concentration, surface area and agitation were all found to be significant for the values chosen. Temperature was less significant and it was found that zinc dissolution is probably a diffusion or mixed controlled process, as indicated by the calculated activation energy of 6 kcal/mole.

Jan 1, 1995

By W. K. Collins

Engineered Scavenger Compounds (ESCs), developed by the U.S. Bureau of Mines, are a novel class of compounds that can selectively recover a desired element from a solid or molten alloy. Lithium titanate (Li2Ti3O7 or L'20-3T'02) is being used as an ESC to recover lithium (Li) from Aluminum-Lithium (Al-Li) alloys. X-ray diffraction measurements have shown that lithium titanate undergoes a phase change from an orthorhombic structure to a hexagonal structure. This change is due to the incorporation of Li in the matrix of the material and the effect of temperature. Although both are metastable, the hexagonal phase that forms during the scavenging of Li from Al-Li alloys appears to be the more stable phase. Recovering Li from the ESC by electrodeposition does not cause the structure to revert to the orthorhombic phase. Both the orthorhombic and the hexagonal structures of Li2Ti3O7 have similar scavenging capacities for Li. This paper proposes a new mechanism for the phase transformation.

Jan 1, 1993

By Richard D. Hagni

Process mineralogy has not been given adequate attention in years past, because geologists have not been sufficiently interested in applying mineralogical techniques to industrial processes, and most process engineers are not adequately trained to use them. Although some individuals and institutions have made efforts to improve the situation, it is only in the last few years that the significance of applying the methods of mineralogy to a wide variety of industrial processes has been fully appreciated. Presently, the formation and organization of several groups devoted to applied mineralogy have created a more amenable climate for the development of process mineralogy. As a result, the presentation, discussion, and publication of the results and case histories of process mineralogy have become fairly common. Short courses affording hands-on experience with applied techniques are now available to the many geologists and process engineers engaged in industrial mineralogical processes. The future role of the process mineralogist is viewed as an expanded one, which will increase in value.

Jan 1, 1982

By Timothy W. Ellis

This paper presents the basic theory of operation, physical chemistry and phase equilibria which allow the development of liquid-liquid extraction circuits based on metallic solvents. The incorporation of reduction and reduction/diffusion processes into the process 'scheme is discussed and a detailed description of ,several liquid-liquid extraction schemes are developed. A synopsis of experimental results obtained using this: method to separate rare earth and other metal based materials will be given.

Jan 1, 1996

By Jiayan Li, Yi Tan, Yao Liu, Yaqiong Li, Shenrui Wu

"A metallurgical grade silicon (MG-Si) refining concept process was presented. Under vacuum conditions, silicon was selectively oxidized by high purity silicon dioxide to form gaseous silicon monoxide while impurities with low vapor pressure in MG-Si were rejected in residue; Then high purity silicon was obtained from the disproportionation of condensed silicon monoxide; and by-produced silicon dioxide was recycled for the oxidation step. Thermodynamics on boron rejection during the oxidation were studied in this work. In the temperature range of 1200-1800K, the saturated vapor pressure of boron, and the Gibbs free energy changes, the equilibrium partial pressures of silicon monoxide and boron oxides of potential reactions were calculated. And the effect of boron activity in MG-Si was also discussed. The results indicated that boron in MG-Si can be rejected during the oxidation and it showed the potential for the further development of the new refining process.IntroductionAs global energy consumption growing dramatically, higher prices of energy and global warming problem have attracted more and more attention [1]. As a clean and renewable energy industry, the photovoltaic (PV) industry converts solar energy to electricity using solar cell device and has a growth rate of about 30% in recent years. It has caused a shortage of silicon feedstock due to that about 90% of solar cells are made of crystalline silicon. And high energy consumption during the production of silicon material, i.e. solar grade silicon (SoG-Si), is main obstacle for its mass production."

Jan 1, 2012

By Richard D. Hangi

Process mineralogy techniques are uniquely applicable to industrial problems related to the extractive metallurgy of nickel, cobalt, and associated metals. Reflected 1ight microscopy, together with selected determinations by scanning electron microscopy-energy dispersive spectrographic analysis and electron probe microanalysis, provides the means to identify the ore minerals cobalt and nickel ores, determine the abundance of each ore mineral, assess the extent of intergrowth between the cobalt and nickel minerals and other ore and gangue minerals in the ores and concentrates, and predict the potential success of cobalt and nickel extraction by grinding, flotation, pyrometallurgical, and hydrometallurgical treatments. In addition, the extent of locking of the cobalt and nickel minerals with each other and with the gangue minerals can be directly observed by reflected light microscopy. Where ores have been treated by hydrometallurgical procedures, reflected light microscopy can serve to determine the causes of excessive leach consumption. Finally, the partitioning of cobalt and nickel between high-temperature synthetic phases produced by pyrometallurgical treatment can be precisely determined by process mineralogy techniques. Case histories from cobalt and nickel deposits illustrate the value of applied mineralogical techniques in the study of cobalt and nickel ores, beneficiation, hydrometallurgial, and pyrometallurgical products.

Jan 1, 1993

By Saad Elias Kaskah

"The Box-Behnken Design (BBD) is used to model the sacrificial Cathodic Protection System (SCPS) to find the factors effectiveness behaviour. For protection potential assessment the BBD receives (resistivity of environment, sacrificial anode alloy, distance between anode and cathode and surface area for the structure to be protected) as input and gives the protection potential as output. By applying BBD with their analysis tools we get many results. The important results which are the factors individual effectiveness on the sacrificial cathodic protection (SCP) process are the resistivity which has the greatest effect on the potential protection (rank=l) followed by sacrificial anode alloy type (rank=2), surface area for structure protected required (rank=3) and distance between anode and cathode (rank=4). The interaction of sacrificial anode alloy and cathode area {X2X4 ) has significant effect on CP process with the limits which are used in this work while the other factors interaction (X1X2, X1X3, X1X4,X2X3, X3X4 ) has insignificant effect on the limits which used in this work.IntroductionFor carbon steel in seawater the normal corrosion potential E '°""_is in the range -550 to -600 mV vs. Ag/AgCI [1]. The most effective method to overcome the corrosion is cathodic protection {CP) which represents a control method in the steel wall corrosion. Cathodic protection has been used in several areas including marine and underground structures, storage tanks, and pipelines [2]. Sacrificial anodes system generates protective current which depends upon the inherent potential difference between the anodes and the structure to be protected. If the structure is made of iron or steel, any metal that is more active in the electromotive force series can theoretically be used as anode material [3]. There are many factors influencing on cathodic protection like resistivity (NaCl content), chemical composition of sacrificial anode alloy, distance between anode and cathode, surface area of cathode, temperature, humidity, velocity of solution, dust, impurities, bacteria and etc .. The present work studied four factors: NaCl content, resistivity), chemical composition of sacrificial anode alloy, distance between anode and cathode, surface area of cathode) with different three levels of values for each one. Then this work will find the optimum value from the factors levels that tacked to investigated there influencing on sacrificial cathodic protection system."

Jan 1, 2013

By J. A. Bakken

Thermal plasmas are interesting for a wide range of metallurgical and chemical processing applications. The 300 kW experimental reactor PRESS, which has been in use since 1987, is operated in the transferred arc mode with three or one plasma torches . Tests include remelting of silicon fines and production of ultrafine silica. Work on a novel three stage process for production of silicon metal is under way. A 1:1 model of the plasma reactor is used to measure the wall heat flux distribution calorimetrically. The cold walls of this model are divided into several water-cooled sections. The same plasma torches as in the real hot-wall reactor are used. In parallel to the experiments and calorimetric measurements theoretical work is done on numerical modelling of one and three transferred arcs. A modified version of the flow simulation program FLUENT from Creare Ltd. is used.

Jan 1, 1991