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By G. G. Krishna Murthy

Interactions of wustite and hematite pellets with Fe-C melts were investigated experimentally by examining the effect of pellet size and bath temperature on the reduction rates of the pellets. Experiments were carried out in the temperature range 1473-1923 K. A flash X-ray equipment was used to obtain images of the melt surface during its reaction with an oxide pellet. The reduction rates were calculated using experimentally estimated time for complete reaction of a pellet, tR. The value of tR was determined employing gas mass flow rate, or pressure rise in the sealed furnace, versus time traces. The value of tR was the same for both wustite and hematite pellets of equal weight at or above 1723 K and it decreased with increasing melt temperature. But the reduction rate was substantially lower at temperatures below 1651 K, the melting point of wustite. The rates were defined as the rate of moles of oxygen removed from the pellet per unit area of bath free surface and it was found that the bath surface area affects the reduction rates. It was established that the overall reaction followed nth-order rate kinetics with the values of n falling between 0.3 and 0.4 for temperatures above the melting point of wustite. The apparent activation energy determined using the apparent rate constants obtained from the experimental data was 76.2 + 27.7 kJ/mol-O.

Jan 1, 1992

By P. Wieser, D. Feke

"Priming of filters with small pores is influenced by the surface tension of the liquid metal and may be complicated by freezing • Freezing followed by melting has been observed experimentally. This process has been modeled on the basis of one dimensional heat flow by radiation to the filter and by conduction in the metal. Also considered are super-heat of the metal and the initial filter temperature. The results of the model provide useful guidelines for the application of filters. IntroductionFiltration has been recognized as a valuable method of refining by removing suspended phases from liquid metals or alloys. Woven fiberglass type fabrics and wire screens were used initially in the aluminum industry. With the introduction of the ceramic filters that exhibit improved inertness and refractoryness, filtration has been introduced to higher melting alloys including cast irons, superalloys, stainless steels, as well as low and medium carbon low alloy steels. A considerable literature is delveloping rapidly on the progress in applications and the advances in understanding the mechanisms and effectiveness of filtration processes (1-8).With the use of filtration for different alloy systems for the production of cast to shape parts a bewildering variety of gating system modifications has been developed (Figure 1) to accommodate the installation of filters in the mold. The modifications have two principal purposes: 1) the runner expansion is intended to compensate for the resistance to flow due to the filter and that of the captured inclusions, and 2) the metal reservoir upstream of the filter, provides a temporary by-pass which permits metal to flow across the filter and heat it until priming can be accomplished. priming of.filters by low and medium carbon steel is readily accomplished but, compared to such alloys as cast iron or 19 Cr-9Ni stainless steel, requires greater precautions to avoid failure to prime by excessive freezing on or inside the filter pores. This problem is further examined below:"

Jan 1, 1986

By Bruno Lebon, Koulis Pericleous, Georgi Djambazov, Mayur Patel

"High speed compressible jets are used in a number of steel-making applications. In the case of the BOF, a compressible oxygen jet reacts with a carbon-rich iron bath to reduce carbon levels and produce steel. The intensity of the process is governed by the speed of the jet and by the size and shape of the depression created in the metal and slag by the force of the jet, i.e. by the corresponding free surface. This is a difficult CFD problem, since there are compressible and incompressible regions in the flow domain, which need to be handled differently in a finite-volume (FV) pressure-correction scheme. Also, standard turbulence models do not account for compressibility, or the large difference in density between the cold oxygen jet and the hot reacting surroundings. Corrections are introduced to the k-E model to remedy this deficiency and the results are validated against experimental data. The compressible/incompressible boundary is handled through a transition region, based on Mach number.IntroductionThe deformation of a free surface by a compressible high speed jet is of paramount engineering interest, particularly for understanding the physical processes within a Basic Oxygen Furnace (BOF). In a BOF, a supersonic oxygen jet impinges on a molten iron surface, thereby creating a cavity. Oxygen penetrates the bath and removes carbon, resulting in low carbon steel [1].The challenges in modelling such a process lie in coupling a solution domain with distinct compressible and incompressible regions and in dealing with large density differences between the modelled gas and liquid. The modelling of compressibility within the jet is crucial, since the correct velocity profile in the jet is required to determine the cavity depth with accuracy."

Jan 1, 2012

By Volker Uhlenwinkel

The design of a free fall atomizer as well as the process parameters affect the particle mass flux distribution in the spray cone. The mass flux distribution is important in spray forming because of its influence on the deposit shape and enthalpy input into the deposit. In this article the effect of different process parameters on the mass flux distribution is shown. Furthermore, different melts were atomized with the same atomizer. An empirical correlation will be introduced to predict the mass flux in the spray cone. This correlation will be compared with experimental results.

Jan 1, 1999

By Z. Zhang, Zongshu Zou, Nan Wang

"Thermodynamic calculation is applied to make an investigation on the equilibrium phase relations and liquids of CaO-SiO2-Al2O3-FeOx system for different temperatures. The calculated results with FactSage6.1 show that the effect of temperature on the the equilibrium phase relations and liquidus of CaO-SiO2-Al2O3-FeOx system and its sub-systems is appreciable. The liquid phase regions enlarge with increasing temperature from 1573K to 1873K, while the primary phase fields reduce distinctly.IntroductionThe main oxide components of vitrified bottom ash slag are CaO, Al2O3, SiO2, Fe2O3, MgO, and Na2O, accounting for more than 90% of the bottom ash by weight[1]. During slag processing, the knowledge of thermodynamic properties and liquidus temperature in the related slag systems is highly required [2, 3], which is not yet available. Through literature survey [4-6], it is clear that the systematic information on the concerned complex slag system is scarce. So far the engineers in the field have to make assumptions of the thermodynamic properties of the simplified oxide system, without taking into consideration the interactions of the different oxide components, which hinders the development of the slag valorization and utilization. In order to provide thermodynamic properties for the application of the vitrified bottom ash, the six-component oxide system (CaO-MgO-Al2O3-SiO2-FeOx-Na2O) is highly required. A preliminary phase diagram of the CaO-MgO-Al2O3-SiO2-FeOx-Na2O system can be obtained from extrapolation of the thermodynamic functions of constituent subsystems such as CaO-SiO2-FeOx-MgO, CaO-SiO2-FeOx-Al2O3, CaO-SiO2-Na2O-MgO and CaO-SiO2-Na2O-Al2O3. In this work, the equilibrium phase relation and liquidus of CaO-SiO2-FeOx-Al2O3 system, one subsystem of the concerned complex slag system, are calculated and the effect of temperature is also discussed."

Jan 1, 2012

By N. A. Vatolin, L. I. Leontjev, S. V. Shavrin

The ever growing interest to the complex iron ores may be attributed to possible production of the naturally alloyed metals and the efficient recovery of the associated elements. However, the conventional technique for complex ore processing is complicated and in some cases even impossible. A pyrometallurgical benefiation of such ores without melted slag formation has been advanced. A version of the technique assumes pellet production with metal coagulated within a slag shell on grinding the pellets, the metal phase is mechanically separated from the slag shell. The technique has been run up with ferro chromo nickel, high-titanium, high-magnesia, alumina phosphorus ores and concentrates. Another version of the pyrometallurgical benefication without melted slag formation in a rotary kiln has been developed from the schemes for processing red mud of alumina manufacture and high-titanium concentrates. Means have been put up to improve schemes available for lex iron ore processing with primary emphasis on material pretreatment before blast furnace and steelmaking processes. Vanadium-bearing titanomagnetite conentrate oxidized pellets possess low strength at reduction. The technique suggested for pelletizing in the controlled atmosphere improves the afore said pellet metallurgical properties. Prodution of metallized pellets in a conveyor roasting machine holds considerable promise for blast furnace and steelmaking processes. In processing the high-sulphur iron ores still another technique is proposed to roast the fluxed pellets with 95% and more desulphuration.

Jan 1, 1988

By John E. Dutrizac, Tzong T. Chen

"Laboratory experiments were undertaken to ascertain the behaviour of various ""impurity"" species during the precipitation of hematite directly from ferric sulphate solutions at 225°C and in the presence of 40 or 50 g/L of hematite seed. Copper, nickel and zinc are not significantly incorporated in hematite precipitates. Although the nickel contents increase to 0.22% as the Ni concentration increases to 60 g/L, the solid solution Ni contents are low relative to the bulk Ni contents. Thus, part of the Ni may be present as tiny particles of poorly soluble NiS04.H20. Increasing germanium concentrations to 2,000 mg/L result in products containing up to 0.59% Ge. The Ge occurs either in solid solution in the hematite or is adsorbed on the nanometer-size hematite crystallites. Increasing As(V) concentrations to 10 g/L increase the AsO4 contents of the products up to 16%. However, the products consist of hematite together with As04-containing Fe(SO4)(OH) and an unknown Fe-AsO4 species. All the hematite products contain - 1% SO4 which appears to be adsorbed on the nanometer-size hematite crystallites.IntroductionDissolved iron is a common impurity in most hydrometallurgical processing circuits and, generally, the iron must be eliminated prior to the subsequent recovery of the sought after metals. Simple neutralization of iron-rich solutions yields slurries which are difficult to thicken and filter. To address these concerns, the jarosite, goethite and hematite processes have been developed, and these technologies are able to reject the dissolved iron in a readily filterable form [1]. Despite its higher cost, the hematite process offers several potential advantages. Because hematite is an iron-rich, high-density compound, its formation would reduce the mass of residue and the size of a residue storage pond. Hematite is the thermodynamically stable form of iron under ambient conditions, and this stability would facilitate the impoundment of hematite precipitates. Furthermore, hematite has some market potential for cement manufacture and even for iron making [2]. In all the commercial hematite processes, the dissolved ferric ions are first reduced to the ferrous state. Subsequently, the pH of the solution is adjusted and the solution is then oxidized. The ferric ions gradually generated during solution oxidation hydrolyze and precipitate mostly as hematite, although commercial hematite products also contain trace or minor amounts of jarosite-type compounds. However, there are potential advantages in precipitating hematite directly from ferric ion solutions, as the reduction and subsequent oxidation of the iron are not required. Although the precipitation of hematite directly from relatively concentrated ferric sulphate solutions (up to 0.5 M Fe(SO4)is) was recently demonstrated [3], the behaviour of impurity species during hematite precipitation is largely unknown. To address this issue, systematic laboratory experiments were undertaken to ascertain the behaviour of a number of ""impurity"" species during the precipitation of hematite directly from ferric sulphate solutions at 225°C, and the results are presented in this paper."

Jan 1, 2012

By Christina V. White

An experimental study was undertaken to investigate the feasibility of utilizing vapor transport for the treatment of heavy metal contaminated smelter soils. The focus of this project was to develop process chemistries that would make incineration a viable process for the treatment these soils. The experimentation concentrated on the elimination of arsenic, cadmium, and lead, and was performed in a laboramry scale rotary kiln setup. Three soil samples from non¬ferrous smelter sites, which contained various concentrations of contaminants, were utilized in the experimentation. Three chemistries were investigated for the volatilization of the heavy metals: Chloridizing volatilization, ferric chloride vapor complex formation, and the use of oxygen potential control. The samples were analyzed for residual heavy metals so that the extractions could be determined. However, the ultimate test was the leachability of the residual arsenic, cadmium, and lead, as determined by the TCLP test. The results firmly establish that incineration is a feasible process for the treatment of metal contaminated soils. It was found that no one process chemistry is suitable for all different soil samples. A two-step process consisting of a reducing step followed by a hydro-chlorination step was required to make Soil Sample-B pass the TCLP tests for all three heavy metals. Soil Sample-A passed the TCLP tests for arsenic, cadmium, and lead using a hydro-chlorination process at a minimum temperature of 700°C. In addition to passing the TCLP mm for Soil Sample-A and Soil Sample-B, 70 to 80 percent removal of the impurities was accomplished. This demonstrates that the leachability of the impurities was decreased primarily due to the removal of a large fraction of the contaminants, Soil Sample-C possessed very high levels of cadmium and lead and only moderate extractions of the impurities were generated from this soil. The arsenic TCLP test was passed at 500'C using a process gas containing ferric chloride and at temperatures of 700°C and above using chlorination of hydro-chlorination.

Jan 1, 1996

By Alicia E. Ares, Carlos E. Schvezov

In the present work it was observed the nucleation and growth of grains in the equiaxed zone of metal matrix composites (MMCs) samples directionally solidified wit the presence of columnarto- equiaxed transition (CET) in the samples. In order to do so, first, it was defined the difference between the real temperature at a given instant, which it is used in the analysis, its variation and furthermore, the variation in the solid fraction with time between the beginning and the end of solidification. It was determined a growth law assuming a lineal variation of equiaxed grain radius as a function of time, and also, it was expressed a law of grain density as a function of time, considering the presence of SiC and Al2O3 particles in the matrix. Finally, the results obtained were validated with measured values of grain density at each position of the thermocouples in the equiaxed zone of the solidified samples.

Jan 1, 2015

By Jeong-Hwan Kim

The liquid-liquid reactive process (solution process) is often adopted as a synthetic method for precipitated calcium carbonate (PCC) in laboratory studies for its simplicity in operation or ease in controlling process variables. Still, PCC are produced commercially by passing carbon dioxide through a milk of lime, i.e., by a gas-liquid reacting method (carbonation process). Few studies on the carbonation process have been conducted, since the process variables are interrelated and difficult to control compared to the solution process. In this study, both carbonation and solution processes were employed to study the polymorphs of calcium carbonate and growth rate of PCC crystals. The effects of the characteristics of limestone ores as a raw material in the synthetic system of PCC on the synthetic characteristics of PCC were also investigated. To control the nucleation rate in the synthetic systems, the shape factor was considered most important. Single-phase aragonite PCC could be synthesized under a variety of controlled experimental conditions such as ionic strength, solution composition, concentrations of additive ions, and temperature.

Jan 1, 2006

By R. Rajiv Srivastava

Brine leaching of a TSL processed zinc-plant residue (ZPR), containing 83.3% anglesite, has been investigated for lead recovery. A prior treatment of ZPR in acid solution did not show any significant effect of acid concentration in zinc dissolution. The study reveals that the solubility limits of PbCl2 is as an important factor with respect to the brine concentration and pulp density in lixiviant. The dissociated sulfate ions hinder the formation of PbCl2 on prolong leaching (above 60 min), while exhibiting the reverse solubility of lead as PbSO4. A 3-step leaching process could yield >92% leaching efficiency when the parameters were maintained as: 10% pulp density in a 250 g/L NaCl solution, 80 °C temperature, and 60 min time. This leaves the insoluble ferrite, sulfides and oxy-sulfates of zinc and lead in the final residue as revealed by the XRD characterization.

By Ullrich Kammer

Metaleurop's secondary lead smelter at Oker produces 60.000 mtpy of lead and lead alloys. More than 8O2 % of the raw materials are spent lead acid batteries. The other 2O2 % consists of drosses, ashes, scrap lead, type metal, sludges, etc., and is processed in a short rotary furnace (SRF). Also, industrial batteries not fitting in the battery scrap treatment plant are processed in the SRF provided with gas/oxygen-burner. Till Sept. 199O2, a soda ash slag was used in the SRF-smelting similar to the rotary kiln-smelting at Oker. Facing the future problems of handling and dumping soda ash slag, Harz-Metall GmbH has improved SRF-smelting with a non¬hazardous slag, insoluble in water, easy to dump and cheap in fluxes. This slag is based on a CaO-SiO2 -Fe0-type. Aim of the slag smelting is to be within the temperature range of 2 1100° and 1200°C - the eutectic line of Olivine in the corresponding ternary system. Since Sept. 199O2 Harz-Metall GmbH has operated the SRF with an "Olivine-type slag" with good results. Although the material is a "leady" slag. HMG is optimistic of using it as a filling material for construction purposes.

Jan 1, 1993

By G. Brooks, J. Naser, M. A. Sattar

CFD models have been developed and numerical simulations have been carried out to predict the formation of foam in oxygen steelmaking. Foam was considered as a separate phase comprising a mixture of gas and liquid. Bubble break up and coalescence models have also been incorporated in a CFD model to predict the number density of individual bubble classes. A population balance equation was used to track the number density of each bubble class. Decarburization with heat generation from chemical reactions was integrated in the process. User subroutines were written in FORTRAN to incorporate the foam formation, the bubble break up and coalescence rate and decarburisation in the main program. The model predicted the foam height, bubble number density, velocity of phases, decarburization, and turbulence. The result from the model has been compared with available data from literature and found to be in reasonable agreement with the experimental and plant data.

Jan 1, 2014

By Jun Li

Rate processes of silver cyanidation were studied with the objective of understanding the reaction mechanism. The research was divided into three sections: anodic dissolution of silver in cyanide solutions, cathodic reduction of oxygen on silver surfaces and the direct leaching of silver in oxygenated cyanide solutions. The charge transfer steps plus the diffusion of reactants from bulk solutions to the silver surface were identified as rate-limiting and the rates of both anodic and cathodic reactions can be calculated using the Butler-Volmer equation and Fick's first law. Based on mixed potential theory and the results of electrochemical studies, a comparison of the rate obtained from direct leaching with that predicted from the calculation is made. Calculated results agree well with the experimental data.

Jan 1, 1992

By Garry W. Warren

The brass foundry industry produces a significant amount of waste sand containing Cu, Zn and Pb which is often classified as a hazardous waste due to Pb content. The potential application of a hydrometallurgical process to treat the sand by extracting metal values and thus detoxifying the material has been investigated. The process involves leaching of metal values followed by cementation. The emphasis of this investigation was on the leaching step, although some preliminary cementation experiments have been performed. In order for any alternative treatment scheme to be successful, the smaller size fractions of the sand must be addressed. Experiments have been performed on five individual size fractions using various lixiviants HCI, acetic acid and HCI/NaCI. Cu extraction was found to be slower than either Zn or Pb. Results obtained in this investigation indicate that copper is present in two forms, an oxide form which dissolves rapidly and is insensitive to the level of oxygen, and a less soluble form, probably metallic which dissolves more slowly and requires an oxidizing agent. The presence or absence of oxygen had no influence on the rate of Zn dissolution indicating that zinc is present mostly in oxide form. Toxicity Characteristic Leaching Procedure (TCLP) tests showed that residues could be produced which meet the toxicity limit for lead. Preliminary cementation experiments have also demonstrated the feasibility of Cu and Pb recovery.

Jan 1, 1991

By Jacqueline JAlexander

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

Jan 1, 2009

By V. Bredykhin

The efficiency of scrap processing depends firstly on reliability of information about its chemical composition. The paper presents the results of the investigation and development regarding solid copper alloy scrap in the range of lump size 40÷300 mm. Nowadays the sorting of lump scrap is done by two methods: 1. Sorting according to metals and alloys is done at places of scrap generation, and further till metallurgical processing each lot has its "certificate"; 2. Hand sorting of scrap is done according to the marks on solid items in special shops using proximate analyzers or manually by experienced workers. This sorting process is labor - consuming low efficient and involves mistakes. The informational method is a promising trend in the copper scrap sorting. The method is direct, i.e. as a result of sorting the chemical composition of each scrap lump or main elements is determined, and assured data of qualitative and quantitative composition are received.

Jan 1, 2006

Pyrometallmurgical reactors constitute a key processing component in the total primary and secondary resource cycle, being involved both in primary smelting, converting and extraction, as well as the reprocessing of scrap, from aluminum cans to end-of-life automobiles. To effectively control the overall resource cycle, one needs to take a systems modeling approach of the whole cycle, seeking to also understand the dynamic process behavior of the individual components of the cycle, and then especially the part that contributes most to the chemical conversion, namely the pyrometallurgical reactor. This paper highlights the role of pyrometallurgical thermodynamics, in the whole resource cycle and specifically places equilibrium thermochemistry in the context of process dynamics where large variable inventories are recycled or maintained within the system. This paper will therefore review the semi-empirical dynamic modeling tools, which are used to model complex systems with the specific goal of developing dynamic predictive models, which also include slag-alloy chemistry, towards controlling the recycling in a feed forward manner. To illustrate the primary processing side, high carbon ferrochrome will be presented as a brief case study. It also will show how the distributed nature of the chemistry of melts in the case of primary extraction, and secondary materials such as recycled end-of-life vehicles, have a significant impact on the process outcomes and model predictions. It is therefore argued that the fundamental thermodynamics and kinetics in metallurgical reactors playa final crucial role in modeling the closed material cycle, but only when it is used in conjunction with process systems theory based on reconciled data for parameter estimation and model calibration.

Jan 1, 2003

By Takashi Fujii

In the OG (Osaka Gas) process which includes a fusion process of sewage disposal sludge in coke bed knowledge of molten and fluid properties of the sludge are most important to controll the process in good condition. Thus, the softening and melting temperatures and viscosity were measured by the sessile drop technique and a rotating viscometer. Obtained results are summarized as follows: Melting character of sludge slag is varied according to their composition, but closely related to CaO/SiO2 ratio in ordinary sludge and to CaO/(Cr2O3,+Al2O3+P2O5) ratio in Cr2O3 containing sludge. Fluid property of sludge slag has a correlation with optical basicity or Riboud parameter, However, the correlation is poorer than that of metallurgical slags. Especially, chromium oxide containing sludge shows high viscosity and behaves somewhat different manner from ordinary sludge.

Jan 1, 1992

By Jerome Feinman, Sven O. Santen

"The principles involved in the generation and application of plasma energy are reviewed briefly and the major developments in commercial and semi-commercial primary metal and alloy production are described and discussed in broad outline, with emphasis on present performance and future potential. New concepts in the application of plasma energy in primary operations are described with emphasis on the expected advantages over conventional technology and the problems that have to be solved to enable effective implementation.IntroductionThe use of plasma energy in industrial processes is generally considered to have started in 1905 with the operation of the Birkeland process for nitrogen fixation for fertilizer production. Although it seems logical to apply plasma energy to metallurgical processes, which also usually require considerable energy at high temperature levels, serious development work along these lines did not begin until the early 1970's. The reasons for this hiatus are associated in part with recognized difficulties in applying plasma energy in processes involving tonnage quantities of solids in severe industrial environments and the delicate nature of the earlier plasma generators. Another, and perhaps overriding factor, is the fairly steady improvement in efficiency and economy of most primary metal producing processes by conventional developments and modifications through the 1950's and 60's. Examples of these evolutionary changes include burden preparation and fuel injection in blast furnace applications and prereduction treatments in ferroalloy operations. By the end of the 1970's most primary metal producing processes had been optimized close to the limit, at least in terms of those operations that were able and willing to implement the developed improvements. In this context, plasma energy offered the possibility to achieve further significant improvements in primary operations where conventional means were exhausted."

Jan 1, 1988