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By H. Yin, T. Emi

"Advantages of gas/flux injection technology as materialized in the main stay unit processes for steelmaking are depicted covering hot metal pretreatment through secondary refining. Current status of micro-kinetic issues involved in the injection technology are reviewed including gas-in- metal, gas-in-slag, flux-in-metal, metal-in-flux and three-phase dispersion systems with reference to macro-kinetics. Key problems are briefly addressed to further develop injection technology for steelmaking processes.1. FROM PAST TO PRESENTApplication of gas injection to steel industry started in early 1950's when inert gas bubbling via stopper rod, lance, or porous refractory plug was practiced to make the temperature of steel melt in ladle uniform The gas bubbling in ladle was then extended to slightly removing hydrogen ti'om the steel melt tapped from Electric Arc Furnace (EAF) and Basic Open Hearth Furnace (BOH) when vacuum processing facilities were not popular. Later, oxygen gas injection via calorized steel pipe into molten steel bath in BOH Furnace was also put into operation to promote the decarburization to increase the productivity of the process. This line of development has been made in parallel with more profound processes, i.e, top blowing Basic Oxygen Furnace (BOF) for primary steelmaking and side blowing Argon Oxygen Oecarburization (AOD) vessel for decarburizing stainless steels.On the other hand, injection of fluxes into steel bath was first industrialized in Germany in 1960's, Primary objective was to desulfurize steel melt in ladle by injecting CaC2 or CaCrCaO mixture via lance under neutral slag cover with good success. Difficulties in injecting fluxes without clogging and rippling at a desired flux/gas ratio, and durability of injection lance were resolved in due time to bring forth many injection facilities to flourish for versatile refining operation. Top injection of fluxes from main oxygen lance to BOF was also industrialized as LDAC to promote early slag formation. A new process then emerged which injects oxygen gas and fluxes together through concentric annular tuyere, installed at the bottom of the BOE into steel melt. This process, developed in Germany [Oxygen Bottom Maxhutte (OBM)] and brought into maturity in USA (Q-BOP) and Japan in a large scale operation, became the predecessor of the combined blowing (top and bottom blown) BOF which dominates modern steelmaking."

Jan 1, 1996

By Jack Thibodeau

During the past six years, most states have promulgated water quality regulations which contain numerical aquatic life standards for heavy metals. In addition, the Environmental Protection Agency (EPA) promulgated national water quality standards in 1992 which also include numerical aquatic life criteria for heavy metals. Numerous wastewater discharge permits have been issued by the states and EPA to industrial facilities which include low microgram per liter heavy metal limitations. In many instances, the limitations are below detection limits or treatability limits using state-of-the-art analytical methods or treatment technologies. This paper will discuss options for conducting studies, including the use of water-effect ratios, metal partitioning coefficients, and recalculation procedures to develop site-specific metals criteria and higher permit limitations. The installation of expensive metal treatment systems to remove trace metals may be avoided if higher permit limits are indicated by the site-specific studies.

Jan 1, 1996

By Ian Baker, Xavier Pierron

"Iron aluminides hold great promise for intermediate temperature applications (to ~ 600°C) because of their excellent oxidation and sulphidation resistance and good strength. However, they have poor low temperature ductility, a feature which is exacerbated by water-containing environments. This paper presents an overview of the effects of environment on the ductility of iron aluminides, including the effects of iron aluminum ratio; ternary alloying additions, particularly boron; strain rate; and temperature. The mechanisms involved in water-induced embrittlement are discussed.IntroductionOver the last few years, it has became increasingly evident that the ductility and fracture toughness of many intermetallic compounds, particularly aluminides, are reduced dramatically if they are mechanically tested in either air or in hydrogen-containing atmospheres (1-5). For FeAI and Fe3AI, it has been shown that water vapor, for example in air at room temperature, can form atomic hydrogen by reacting with the Al atoms (1, 2). As a result in iron aluminides, the environmental embrittlement process is quite similar to traditional hydrogen embrittlement. This can be easily demonstrated by either testing an iron aluminide in an environment free of the deleterious species or by testing at high strain rates, both of which result in greater ductility. The purpose of this paper is to review recent progress in understanding environmental embrittlement in FeAI and Fe3AI, and to consider possible environmental embrittlement mechanisms. Greater understanding of this phenomenon will lead ultimately to remedies to this problem which is a major reason for preventing the practical application of these materials. First, some background on the iron-rich aluminides."

Jan 1, 1996

By Richard J. Abitz

Thennodynamic geochemical models have been applied to assess the relative effectiveness of a variety of reagents added to aqueous waste streams for the removal of radioactive elements. Two aqueous waste streams were examined: effluent derived from the processing of uranium ore and irradiated uranium fuel rods. Simulations of the treatment train were performed to estimate the mass of reagents needed per kilogram of solution, identify pH regions corresponding to solubility minimums, and predict the identity and quantity of precipitated solids. Results generated by the simulations include figures that chart the chemical evolution of the waste stream as reagents are added and summary tables that list mass balances for all reagents and radioactive elements of concern. Model results were used to set initial reagent levels for the treatment trains, minimizing the number of bench-scale tests required to bring the treatment train up to full-scale operation. Additionally, presentation of modeling results at public meetings helps to establish good faith between the federal government, industry, concerned citizens, and media groups.

Jan 1, 1996

By P. R. Khangaonkar

The industry of tin ore mining, beneficiation and smelting gives rise to a number of waste products like the beneficiation plant wastes (called amang), tin smelting slags, refinery dross etc. Some of the wastes deserve treatment to obtain economically useful products or to recover the metal values. The paper describes studies conducted on two materials, viz., struverite-middling (struverite-magnetic tin), which is an intermediate product of beneficiation circuits of tin tailings, and tin-smelting slags. The struverite middling was studied for treatment by chlorination using carbon tetrachloride, so as to yield vapour products separable by convenient condensation. The treatment was also found to lead to a tin-rich product amenable for treatment by known hydrometallurgical routes. The tin smelting slag was studied by alkali-leaching so as to avoid any dissolution of iron and it was possible to obtain an iron-free product solution suitable for high purity tin recovery.

Jan 1, 1996

By D. E. Karvelas

Argonne National Laboratory is conducting research to develop a cost-effective and environmentally acceptable process for the separation of high-value plastics from discarded household appliances. The process under development has separated individual high purity (greater than 99.5%) acrylonitrile-butadiene-styrene (ABS) and high-impact polystyrene (HIPS) from corruningled plastics generated by appliance-shredding and metal-recovery operations. The process consists of size-reduction steps for the commingled plastics, followed by a series of gravity- separation techniques to separate plastic materials of different densities. Individual plastics of similar densities, such as ABS and HIPS, are further separated by using a chemical solution. By controlling the surface tension, the density, and the temperature of the chemical solution, we are able to selectively float/separate plastics that have different surface energies. This separation technique has proven to be highly effective in recovering high-purity plastics materials from discarded household appliances. A conceptual design of a continuous process to recover high-value plastics from discarded appliances is also discussed. In addition to plastics separation research, Argonne National Laboratory is conducting research to develop cost-effective techniques for improving the mechanical properties of plastics recovered from appliances.

Jan 1, 1996

By Steven R. Pittman, Colin McCullough, Peter Galuska

"Traditionally Continuous Fiber Aluminum Matrix Composites have been fabricated using high strength fibers and high strength matrices, often commercial alloys, with the goal of producing high strength composites. However the specific role of the choice of matrix alloy on composite properties has not been well established. One way to control composite tensile strength is to use coatings to introduce a low strength interface between fiber and matrix which tends to reduce the importance of the matrix selection, but unfortunately renders the transverse strength unacceptably low. Thus using a system with strong bonding between fiber and matrix is desirable, such as an alumina fiber / aluminum alloy matrix system. In this case the transverse strength is a strong function of the matrix strength. However the longitudinal strength then depends largely on the characteristics of the matrix. The important role of the matrix is discussed using examples of alumina fibers in various aluminum alloy matrices. The key attributes are matrix constituent phases, alloy chemistry, alloy reactivity with the fiber, and matrix strength. From the understanding developed in these systems a set of design rules may be established for selecting an optimum matrix. IntroductionAluminum matrix composites (AMC's) reinforced with continuous fibers offer very attractive property gains over AI alloys, such as strength, stiffness, and fatigue resistance. These gains are magnified when specific mechanical properties are compared which make them attractive candidates for replacing steel, nickel, titanium and aluminum alloy parts in weight critical applications (1). Many systems have been tried in the past; B/AI, C/AI, SiC/AI, Si-Ti-C-O/AI and AI203/AI. Technically B/AI was a very good system but was expensive in regard to both fiber cost and fabrication and SiC/AI and C/AI systems are still plagued with reactivity problems. The Si-Ti-C-O/AI appears to be a good strength system but with lower stiffness. Until recently, the AI203/AI was a low strength system, in part due to a lack of a high strength fiber. Recently 3M introduced a high strength AI203 fiber - Nextel™ 610, which leads to high strength composites (1,2) and may also be both low cost and also compatible with less expensive casting approaches for fabrication."

Jan 1, 1996

By Suswnu Makino

Sumitomo Metal Mining developed a new nickel refining process ( Matte Chlorine Leach Electrowinning process) based on chlorine leach and electrowinning technologies. After the pilot plant study, the commercial plant with design capacity of 24,000 tonnes per year was constructed and has been successfully operated since August, 1992. During the practice of the past three years, great deals of improvement have been achieved. Through these operations the MCLE process has been demonstrated to be one of the most superior processes in the world with nickel recovery, productivity, cathode quality and working environment. Today the refinery product capacity is increased to 30,000 tonnes per year. This paper describes the equipments and operation of the Sumitomo MCLE process.

Jan 1, 1996

By A. Elizabet Serna

The weak acid is a by product obtained in a pre-treatment of gases from a copper smelter prior to sulfuric acid manufacture and the main components of this weak acid are: sulfuric acid. copper, arsenic. antimony, bismuth and iron. Usually, this effluent is neutralized with lime and the solid residues are stored in a landfill as a hazardous waste. This work was directed at determining the optimal conditions to recover copper from weak acid using a cementation process before the neutralization of the effluent. The variables investigated are: Effluent temperature, iron scrap amount and acid concentration versus reaction time. The results of these experiments show that the cementation process of copper and the co-cementation of impurities such as arsenic, antimony and bismuth were in accord with the theory of the electrode potentials.

Jan 1, 1996

By Keuncheol Choi, Yonghack Lee

"The new lead smelter based on the QSL technology was started operation from May 1992 at Onsan Refinery of Korea Zinc Co., Ltd. The smelter is designed to treat not only various types of lead concentrate but also secondary materials coming from the zinc plant without special pretreatment.Shortly after the start-up of the operation, it has demonstrated that the smelter have a capability to treat wide range of raw materials. Continuous modifications and improvements of the plant are still under way to increase the feed rate and also the ratio of secondary materials to the feed.In this paper, the operating experience and results of QSL smelter, especially the injection of gases and coal to the melt, will be presented with major operation parameters and data.INTRODUCTIONThe QSL lead smelter based on new injection technology was commissioned at the Korea Zinc's Onsan plant from May of 1992. After starting the operation, the QSL lead smelter faced various kinds of mechanical and metallurgical troubles. However, these were gradually worked out by the continuous improvements and efforts.At present, the QSL lead smelter is operated stably at the total feed rate of 57 tonnes per hour with an increased amount of secondary materials."

Jan 1, 1996

By Du Sichen, S. Seetharaman, J. A. Bustnes

"The present study deals with the kinetic studies of reduction of some selected transition metal tungstates with hydrogen. The measurements were carried out by the isothermal thermogravimetric method. Shallow powder beds were employed in order to avoid the effects due to transport phenomena affecting the reaction rate. In this way, the chemical reaction rates could be selectively studied. The experiments were carried out in the temperature range 873 - 1173 K. From the experimental data, the activation energies were evaluated and were found to be around 88 kJ / mol in the case of both iron as well as cobalt tungstates indicating the similarities in W-O bonds in both cases. The activation energies obtained are discussed in the light of the position of the transition metal in the periodic table as well as the thermodynamic stabilities of the various tungstates.IntroductionThe tungsten containing hard metals, characterized by high density, belong to a class of two-phase metal matrix composites. While these types of materials have traditionally found their applications within the defence industry as armour-piercing projectiles, counterbalance in helicopters and military aircrafts, outer casings of hand-grenades, etc., commercial applications for this class of alloys also exist, including radiation shields, penetrators for the oil industry, turbines for turbo-jet engines and a wide range of sports related parts. A possible route to the production of these alloys is to reduce the tungstates such as FeW04, Co W04 and NiW04 using a reductant like hydrogen or carbon monoxide. In order to have a better understanding of the processes involved in the production, it is important to have a knowledge of the reduction kinetics for these tungstates. According to the knowledge of the present authors, while the reduction ofNiW04 by hydrogen gas has been investigated earlier in the present laboratorypl no systematic reduction study has been carried out previously for the tungstates of iron, cobalt."

Jan 1, 1996

By Milton Manrique

The thermal decomposition of zircon concentrates in a non-transferred arc thermal plasma flow reactor was investigated. The plasma torch was operated using argon-helium and argon-nitrogen mixtures as plasma gases. The effect of power, feed rate and zircon particle size was studied. Products were characterized by XRD, SEM, TEM and chemical analytical techniques. The average size of the product was in the submicron range. Free energy minimization plots were used to predict the behavior of the system under different operating conditions. A kinetic model to describe the different stages of the thermal decomposition process is proposed. The results of this investigation showed a significant segregation process where the zirconia-rich product is collected in the reactor while the silica-rich product is collected in the filter. TEM analysis indicated that silica vapor is condensed on the surface of the zirconia particles.

Jan 1, 1996

By Luis W. Pommier

The wastes of the plating industry are generated in the process of rinsing the plated objects and during the cleaning of the plating shops. High volumes of hazardous waters are neutralized on site producing recyclable water, generating a metal rich, hazardous, filter cake. Occasionally, a complete plating bath has to be discarded which increases the metal content of the filter cakes. These filter cakes are discarded as hazardous at a cost of over $ 250 per ton. The metals found in the cakes are generally copper, nickel and chromium or zinc, lead and cadmium, assaying from 2% to 15% or even higher content of each metal The metals and their contents are highly variable. Some plating shops discard their products directly to hazardous waste sites, others, have them collected by companies which consolidate wastes from several producers prior to discarding. These wastes, richer in metal content than mine ores, need neither mining nor crushing and grinding for concentration. The commonly found impurities in the mine ores, i.e.: pyrites, arsenic, and valuable metals which are present in minute quantities, are absent in the filter cakes. The processes available to selectively recover the metals from the filter cakes, are discussed based on their technical and economic merits. The flow-sheets include leaching, solvent extraction when required, and electrolytic refining. Examples, showing the separation of copper, nickel and chromium and also of zinc and lead in pilot plants, show the technical and economic viability of the processes.

Jan 1, 1996

A modified Cuprex Metal Extraction Process (CMEP) leach process was used to extract Cu. Ni and Co from a complex sulphide concentrate. The standard leach was modified to a two-stage countercurrent leach which provided emf control of the copper SX feed and minimized iron dissolution. A flowsheet was developed to recover the base metals and silver from the leach solution and gold and platinum group metals from the leach residue which was predominantly elemental sulphur. Techniques required to maintain an iron balance in the system including pressure oxidation and solvent extraction are described.

Jan 1, 1996

By Matthew C. Binsfield

The simultaneous electro winning of zinc and manganese from waste water treatment plant sludge was studied as a part of the overall research program, which was conducted to develop the methods for removal of environmentally hazardous metals from the Bunker Hill Superfund Site. This paper discusses the electrolytic method for recovery of zinc and manganese from the solution produced by leaching of sludge with S02 + H2S04. After three stage purification of the leaching solution, zinc and manganese were electro won simultaneously in an undivided electrolytic cell. Zinc was deposited on an aluminum cathode, while manganese was simultaneously produced (as Mn02) on a lead silver anode. The electrowinning parameters studied were the effects of: temperature, current density, electrode material, spacing of electrodes, composition of electrolyte, and electrolyte additives. Anodic and cathodic efficiencies were 30 and 91%, respectively. In light of the process design parameters discussed in the paper, which are affecting the electrowinning, these efficiencies were found as acceptable with regard to the quality and marketability of the products.

Jan 1, 1996

By Vaughan R. Voller

In many high temperature processes involving liquid melts the common practice is to solidify a fraction of the melt adjacent to the containment wall; a practice that can provide protection of the structural components of the process. The position, shape and transient behavior of these so called "skulls" and/or "ledges" are directly dependent on the thermal process conditions. This paper presents a model of a generic ledge process that can predict the steady shape of a ledge. Two numerical implementations are presented and compared: (1) based on a space grid of continuously deforming finite elements (2) based on a conjugate grid of fixed control volumes and deforming boundary elements.

Jan 1, 1996

By Y. Suzuki, J. Nagao, Y. Ueda, K. Shimokawa

"A Ti- Ni intermetallic compound could be formed rapidly from Ti and Ni powder compact with SHS process. Microgravity experiments using a drop shaft are carried out, This report shows the effect of microgravity or high gravity on formability of an intermetallic compound. It is concluded that the specimen forms a porous and nearly amorphous alloy by rapid cooling under microgravity but with rapid cooling under high gravity after microgravity, the specimen forms a uniform and dense structure with better crystallinity.IntroductionTi - Ni inter1etallic co1pounds have been produced and have beco1e si1ilar to the a1orphous and porous structure as a result of the SHS (Self Propagating High-te1perature Synthesis) process under 1icrogravity. SHS process is being applied to the synthesis of cera1ics and inter1etallic co1pounds (1). The technique is characterized by a large a1ount of heat being emitted within a very short ti1e interval as regards the sistering reaction. One SHS process, acco1panying 1elting by a reaction was observed, and that was due to the quick heating of a Ni-Ti co1pact containing 50 ato1ic percent of Ti under a low pressure (2-4). In this report, we have researched the use a drop shaft which is 1ore effective during a short ti1e under 1icrogravity and high-gravity, so as to obtain high dense speci1ens with the exception of porous specimens (5). Mechanical properties of each specimen were esti1ated from these 1icro-structures with a discussion about the effect of changing gravity regarding 1elting and solidification of the Ti-Ni intermetallic comounds."

Jan 1, 1996

By Jan G. H. du Preez, C. Viviers, B. J. A. M. van Brecht, H. E. Rohwer, Nicole M. Sumter

"At the basis of metal ion separation lies some particularly metal ion specific chemical property which lends itself towards exploitation. This could be in the form of an anionic complex or a neutral chelate complex. In the former a cationic centre with a particularly high affinity for the complex will have to be designed. In the latter case a stereospecific chelate ligand containing the correct symmetry and type of donor atoms will have to be designed. In both above cases the ""active centre"" can be entered in a from that it can function in different media of hydrophobicity, eg a precipitant, a resin or a solvent extractant. Recent results obtained in this laboratory will be used to illustrate how the above variables can be exploited to develop improved processes for the separation of base metal and platinum group metals.IntroductionThe separation of metal ions in hydrometallurgy can be performed broadly speaking with two major aims. Firstly the separation/removal of a certain group of metal ions, either as a means of preconcentration or as a removal from effluent as part of a purification process and, secondly the removal of a specific metal ion from an industrial stream in order to produce a specific metal in a pure form. This latter operation is by far the most difficult of the two and is becoming more so in the light of the fact that the world is moving in the direction of lower grade ores and increasing pollution. Such a process can be divided into three essential parts, firstly the molecular one in which an active centre is required to obtain specificity, secondly a matrix within which this active centre must function, i.e. as part of a resin or solvent extractant and thirdly the design of the total system to optimize the realization of the operation."

Jan 1, 1996

By K. Osseo-Asare

"The molecular structural and solution chemical characteristics that underlie the surface activity of solvent extraction reagents are highlighted, with particular emphasis on the tendency towards reverse micelle and microemulsion formation. The physicochemical factors that lead to microemulsion-enhanced solvent extraction with chelating extractants are elucidated. Membrane-based contactor systems are described which are uniquely suited for enhanced solvent extraction with microemulsions. The possibility of combining solvent extraction with microemulsion-mediated materials synthesis is discussed. IntroductionThe discovery of new selective extractants has resulted in major breakthroughs which have helped to establish solvent extraction as a versatile separation technology (1-3). A complementary strategy towards new process development is to seek new ways of using the available reagents. This paper explores this second approach. From a molecular structural standpoint, an extractant may be viewed in terms of two components: a polar functional group and a hydrocarbon radical. In the conventional view of solvent extraction, this molecular structure serves two main purposes: The polar functional group provides the binding sites for complexation of metal ions, while the organic group is needed to render the resulting metal-extractant complex organic-soluble. But are these the only properties of the organic and the polar groups that are relevant to the solvent extraction process?In this paper, attention is directed to the fact that solvent extraction reagents possess the molecular structures of amphiphiIes; that is, they are characterized by the presence of spatially separated hydrophilic and hydrophobic groups on the same molecule. A case is made for the view that this amphiphilicity offers interesting opportunities to develop new separation processes which collectively may be described as enhanced solvent extraction (4-6)."

Jan 1, 1996

By Hye-Sung Kim, Dong-Wha Kum, Gyeungho Kim

"Mechanical alloying is an effective way to finely distribute inert dispersoids in AI-TM (TM is a transition metal element) systems. It is considered that high melting point aluminides are formed by precipitation from the supersaturated aluminum matrix. The analysis is based on the fact that much higher content of TM than the solubility limit can be dissolved in alpha aluminum during the high energy ball milling. Nonetheless, the role of undissolved TM particles affecting the formation of aluminides is not suitably considered. In this paper, authors present experimental observation on the formation of Ab3Ti particles from mechanically alloyed AI-Ti alloys in the hyper-peritectic region. This study showed that, in the mechanically alloyed AI-20wt%Ti specimen, intermediate phase of cubic Ab3Ti and tetragonal AIz4Tis formed at 300 - 400°C and 400 - 500°C, respectively, before the MA-state reaches to the global equilibrium at higher temperatures. The formation behavior of Lh- Ab3Ti is interpreted by interdiffusion of Al and Ti in solid state based on the fact that large amount of nano-sized Ti particles exist in the milled powder. Present analysis indicated undissolved Ti particles of nanosize should have played an important role initiating the formation of Ab3Ti phase during annealing.IntroductionInterest in the hyper-peritectic AI-Ti alloys is based on industrial demand for high-modulus and high-temperature aluminum alloys. Earlier works on hyper-peritectic AI-Ti alloys with 4 to 12wt%Ti show that these alloys are strong at ambient temperature and maintain high strength above 300°C when titanium-trialuminide (e.g., Ab3Ti) is finely distributed in the aluminum matrix [1,2]. High melting point and high stiffness with low density of AbTi make the AI-Ti alloys strong with greater thermal stability while keeping weight savings as much as possible. Titanium in aluminum shares other merits of transition metal additions because Ti solubility in Al is low (i.e., 1.l5wt%Ti at 665°C and virtually zero below 400°C), and fine dispersion of Ab3Ti particles is readily accomplished and resists grain coarsening effectively."

Jan 1, 1996