Search Documents

By Eva B. Kisvarsanyi

An Early Proterozoic orogenic terrane of metasedimentary and metaigneous rocks underlies Nebraska, Kansas, and Missouri. Middle Proterozoic epizonal terranes of anorogenic granite and rhyolite, a known metallogenic province partly exposed in southeastern Missouri, overlap the orogenic terrane on the south. These Proterozoic terranes, covered by less than 1,000 meters of Phanerozoic strata, contain a virtually untapped source of mineral wealth and are one of the last frontiers for geologic exploration in the continen-tal United States. Petrographic study of subsurface samples is a powerful tool in the identification of favorable host rocks for a variety of ore deposits.

Jan 1, 1987

By K. Osseo-Asare

It is possible to form a two-phase system in certain polymerlinorganic salt/water mixtures, such as those containing the polymer polyethylene glycol (PEG). Such aqueous biphase systems have many of the separation characteristics of conventional solvent? extraction systems, but are environmentally friendlier. Just like the well-known organic solvent/water two-phase system, the top polymer-rich phase is more hydrophobic. and the bottom salt-rich phase more hydrophilic. The partition of dispersed? particles is dependent on the interfacial interaction between the particles and the conjugate aqueous biphase solutions. In particular, the hydrophilic/hydrophobic properties of the surface determine the transfer of the dispersed particles into either the top (more hydrophilic) phase or the bottom (more hydrophobic) phase. Accordingly, differences in the surface chemistry of particles can be exploited to achieve selective separations. In this work, several approaches to separation control will be discussed. using pyrite (FeS2), alumina (AI203). hematite (Fe203), silica (Si02), and titania (Ti02) as model particulate materials. For metal sulfides, pH and redox potential can be used to alter the hydrophobicity/hydrophilicity of the particles. In ?the case of oxides. polymer adsorption and collector adsorption may be exploited to facilitate particle transfer.

Jan 1, 1999

By E. Gutierrez-Miravete

A computational method for the simulation of mold filling processes is described. The method is based on the representation of the flowing or deforming medium as a collection of mutually interacting parcels of material. Instantaneous positions of individual material parcels are calculated by numerical integration of the dynamic equations, subject to appropriate initial and boundary conditions. So far, the method has been used to produce qualitative simulations of some flowing and deforming systems encountered in mold filling technology, and our findings are summarized herein. In all cases, individual material particle motions can be followed in detail, allowing critical examination of potentially problematic mold design features.

Jan 1, 1992

By Run-sheng xu, Hai-yang WANG, Di ZHAO, Teng-fei SONG, Jian-Liang Zhang

This paper was mainly focused on the different semi-cokes and charcoal which could be new fuels for blast furnace injection. Through the comparative study with bituminous coal and anthracite coal, the properties of semi-cokes and charcoal were presented in this research. 10 indexes of different fuels were obtained by different standard experiment, including proximate analysis, ultimate analysis, igniting point, explosivity, transportation characteristic, ash properties, grindability, calorific value, combustibility and reactivity with CO2. According to the data analysis, it provided a theoretical basis for rational utilization of various blast furnace fuels, and helped to broaden the scope of the blast furnace injection fuels. This research could contribute to energy conservation, emissions reduction, and sustainable development of iron and steel enterprises.

Jan 1, 2015

By Y. H. Wang, S. Kou

"Three-dimensional weld pool convection was computer simulated using dimensionless variables. The electromagnetic force, the buoyancy force and the surface tension gradient on the pool surface were treated through the use of the dimensionless electromagnetic force, the Grashof number and the Marangoni number. Other typical dimensionless numbers such as the Prandtl number and the Peclet number were also used. The calculated and experimentally observed fusion boundaries were compared. The convection patterns were shown and the effect of the Marangoni number was demonstrated. IntroductionSeveral weld pool convection models have been developed by Oreper et al. (1,2), Chan et al. (3) and Kou et al. (4). These models describe two dimensional convection in stationary weld pools in a semi-infinite workpiece. Since the vast majority of arc welding practices involve a moving heat source and weld pool, and the workpieces are finite in thickness rather than semi -infinite, a 3-D convection model for a moving heat source and a workpiece of finite thickness is expected to be much more useful.Weld pool convection can strongly affect the structure and properties of the resultant welds. Variations in weld characteristics which are likely to occur from changes in weld pool convection are: weld penetration, macrosegregation, gas porosity, solidification structure, undercutting and surface smoothness. Apparently, the quantitative understanding of convection and heat flow in weld pools is of considerable practical interest. Mathematical models describing convection and heat flow in weld pools are essential, not only because of the quantitative understanding they provide, but also because of the difficulties associated with the experimental measurements of weld pool convection. These difficulties are mainly due to the fact that only surface flow, rather than the overall convection pattern in the weld pool, can be observed. In fact, due to arc glow even the observation of surface flow can be rather inconvenient."

Jan 1, 1986

By Luísa Maria Abrantes

Environmental control is becoming more and more stringent. As conventional processes for zinc production are pollutant routes, alternative methods have become an important subject of research. In this regard, the leaching processes have aroused a considerable interest, namely the electrochemically induced approach. The behaviour of zinc concentrate ore in the leaching processesses is influenced by several parameters. Chloride concentration and leaching solution pH, time and temperature of reaction were studied in order to evaluate their influence on the zinc recovery. The efficiency of the leaching process for zinc extraction is performed by factorial design. The experiments were carried out by 23 and 22 factorial designs of the factors. Results show that all factors, except for the time of reaction have a significant influence on the optimisation process, within each experimental region.

Jan 1, 2001

By B. Farouk, Y. G. Kim, D. Apelian

"Continuous strip casting has received considerable attention in recent years due to its economic advantages with increased energy savings and the elimination of intermediate processing steps. A promising concept in strip casting is the twin-belt (Hazelett) process which incorporates two cooled continuously moving thin metal belts wrapped around pulleys which tension and drive the belts at a predetermined speed. Molten metal is introduced at the entry end of the caster through a tundish and feeding nozzle into the mold. The twin-belt process has been successfully used with non-ferrous metals such as aluminum, copper and brass, and is a prime candidate for strip casting of ferrous materials. A numerical model has been developed which predicts the interface locations, the temperature fields in the solid and liquid regions of the cast and the velocity fields of the liquid metal at the entrance region of the twin-belt caster. The process variables considered are the velocity and cooling conditions of the belt and the nozzle shape. A body fitted coordinate system is used to track the front locations and to solve .the Navier-Stokes equations in the liquid region. Results obtained can help design efficient casters for thin strip steel castings. The development of the numerical model is presented, and sample results are discussed. I. IntroductionContinuous strip casting of steel has attracted world-wide concerns in recent years due to its economic advantages with increased energy savings and the elimination of intermediate processing steps. New methods of thin strip casting of steel are developing. One of the promising concepts is the Hazelett process, which is being used in nonferrous applications. The process incorporates two continuously moving, intensely cooled, thin metal belts. Metal blocks linked together are sandwiched between the moving belts and form moving side mold walls.In this work, the freezing front position, the temperature field and the liquid region flow field will be analyzed for the strip casting of metal using the twin belt caster (the Hazelett process). Up to now almost all theoretical analyses undertaken of the continuous casting of metal [1-3] have used a heat conduction equation, assuming slug flow in the liquid region. The effect of convection in the liquid pool during continuous casting were first investigated by Szekely and Stanek [4]. They considered potential flow between the feed metal orifice and the liquidus front, and slug flow in the mushy and solid regions of a vertical static continuous casting process for steel. Viscous effects and natural convection affects were not included Kroeger and Ostrach [5] studied the effect of natural convection flow in the liquid pool during solidification for a pure metal."

Jan 1, 1986

By W. G. Davenport

Smelting oxidizes Cu-Fe-S concentrate to matte. Converting oxidizes this matte to metallic copper. Smelting and converting are, therefore, part of the same oxidation process. It would seem natural, then, that smelting and converting should be combined to produce metallic copper in one step. This would: (a) maximize S02 capture by restricting S02 emission to a single, continuous source (b) minimize industrial oxygen and fuel requirements (c) minimize cost. This chapter discusses one step, direct-to-copper flash smelting as it is practiced in 2000. It then uses. the matrices of this book to determine: (a) the industrial oxygen and oil requirements of direct-to copper flash smelting (b) the distribution of Cu between metal and slag during direct-to-copper flash smelting. It concludes that direct-to-copper flash smelting: (a) captures?S02 efficiently from its single continuous stream of SO2 off gas (b) minimizes oxygen/oil consumption but: (c) sends -114 of its Cu-in-feed to slag.

Jan 1, 2001

By Claudia Gasparrini

Uranium occurs in a variety of minerals, the more common primary ones of which are uraninite-pitchblende, coffinite and a group known as the complex multiple oxides. Identification and description of the uranium-bearing and associated minerals in ore samples may give a preliminary indication of the potential economic importance of the deposit and may also suggest initial approaches to metal extraction. The present paper reviews the common uranium minerals, describes their manner of occurrence and compares the types of deposits with which they are associated. Methods and techniques for their identification are described and their leaching characteristics discussed.

Jan 1, 1981

By G. S. Gupta

To predict the iron oxide concentration a mass transfer model has been developed for an Induction Smelting Process (ISP) in which self-fluxed composite pellets (made of iron ore, brown coal and lime) are melted in a single phase induction furnace in conjunction with top blown oxygen. Transient mass balance equation with complex boundary conditions has been worked out by adopting a relatively new approach known as the cell model approach. These equations have been solved numerically using finite difference technique to obtain the iron oxide concentration profile in the ISP. Numerical and experimental results obtained for iron oxide concentration show a reasonable agreement with each other.

Jan 1, 1991

By Kumar M. Lyer

The channel reactor for ferrous and nonferrous processing has been modeled as a combination of ideal reactors. Cold model studies simulated the counter-current flow of slag and matte (or metal) with high-strength submerged gas injection. A composite model has been developed which describes the mass transfer between the two liquid phases, including the transfer of minor elements. The residence time for the matte droplets in the matte/slag emulsion is compared with the settling rates for the matte droplets in the slag to determine their relative importance in the mass transfer between matte and slag. The governing equations for mass transfer have been developed using correlations for the mass-transfer coefficients in the continuous and dispersed phases. An application of this scheme to a typical copper smelting system is presented.

Jan 1, 1993

By Artur R. P. Junior Sergio, Pedro A. Netto, N. Monteiro, Foluke S. de Assis, Frederico M. Margem

Synthetic fibers are being replaced gradually by natural materials such as lignocellulosic fibers. Compared to synthetic fibers, natural fibers have shown advantages in technical aspects such as environmental and economic. So there is a growing international interest in the use of those fibers. The banana fiber presents significant properties to be studied, but until now few thermal properties on banana fiber as reinforcement of polyester matrix were performed. The present work had as its objective to investigate, by photoacoustic spectroscopy and photothermal techniques the thermal properties of diffusivity, specific heat capacity and conductivity for polyester composites reinforced with banana fibers. In the polyester matrix will be added up to 30% in volume of continuous and aligned banana fibers. These values show that the incorporation of banana fibers in the polyester matrix changes its thermal properties.

Jan 1, 2015

By E. Allain

Extraction of basic metals from sulfides by conventional pyrometallurgical processing leads to the emission of SO2. To avoid this inconvenient, low temperature selective chlorination of sulfide concentrates could be an alternative. However, such process generates hazardous chlorides SxCly. A part of sulfur chlorides such as SCI2 can be recycled as a chlorinating agent of metal sulfides. Hydrolysis of sulfur chlorides, using a solution containing Na2S.9H2O, led to the recovery of more than 90 pct of elemental sulfur. Reduction of SxCly by hydrogen was investigated between 300 °C and 800 °C. About 70 and 90 pct of elemental sulfur were recovered from SC12 and S2C12, respectively. A flow sheet for the chlorination of metal sulfides and the treatment of sulfur chlorides was suggested.

Jan 1, 1998

By G. H. Khoe

Although some hydrometallurgical process liquors contain significant amounts of ferrous and arsenate ions, no reliable thermochemical data for the aqueous complexes and the solubility of the ferrous arsenate precipitate are available. The complexation of iron(11) with arsenate has been investigated using the potentiomemc titration method. The results indicated that virtually no complexation of iron(@ with arsenate has been observed. This is in contrast to the significant complexing reported for iron(1n) with arsenate. The solubility product of the precipitate was calculated using the concentrations of appropriate arsenate species pertaining to the observed precipitation pH's. The fit of the observed precipitation points on the solubility curve of the computed stability diagram was used to assess the appropriateness of the equilibrium model.

Jan 1, 1991

By Toshiaki Akahoshi

Keywords: Wasted catalyst, Hydrodesulfurization, Ammonium vanadate, Ammonium molyb-date, Hydrometallurgical process. The fundamental reactions have been investigated in order to develop a hydrometallurgical process for recovery of molybdenum and vanadium from wasted catalysts generated in the hy-drotreating desulfurization of heavy oil. The principal steps of the process are a mild oxidation roasting of the waste catalysts at temperature around 500°C, leaching of the target metal components with dilute ammoniacal aqueous leachates, selective precipitation of vanadic acid, and ammonium molybdate precipitation. The selective recovery of vanadium as vanadic acid is successfully performed using ammonium sulfate as a salting-out agent. Recovery of ammonium molybdate is based on large dependence of solubility of ammonium molybdate in ammoniacal solutions upon temperature and ammonium salt concentration. In this process, the solution after recovery of vanadium and molybdenum is recycled to the leaching stage of the roasted materials, and the ammonium salts in the process liquor is in the repeated use. Employment of am-moniacal system makes it possible to operate the roasting at much lower temperature than that for the currently operating process.

Jan 1, 2005

By Rolando Campos

Until 1970, the Caletones Smelter of CODELCO-CHILE, División El Teniente, operated under the conventional pyrometallurgical process used by most of copper smelters. The annual copper production varied around 165.000 tons. The failure in the commissioning of the "oxygen smelting" technology in Peirce- Smith converters (1970-1972), forced further introduction of transcendental changes in the Caletones smelter operating scheme. Implemented technological innovations were based on wide studies and research works performed by División El Teniente. This paper presents a summary of technological modifications introduced, their impact on production and energetic performances, and short and medium terms improvement plans.

Jan 1, 1993

By John J. Dunkley

Recent years have seen the increased use of hydrometallurgy in the smelting and refining of metals. However this is often used as a final refining step, following an initial pyrometallurgical smelting process. Huge amounts of material are produced as melts which have to be cast, comminuted, and taken up into solution or leached. A common method is to granulate the melt and then grind it. In the case of metallic melts this can be difficult or unfeasible due to the ductility of the granulated particles. Water atomisation is capable of replacing the granulation and grinding stages with a single process step that can process in excess of 30tlhour of melt into particles as fine as 50 microns. Applications in operation in Co, Cu, Ni, Ag, Au, Pt and Rh refining are discussed together with potential applications in copper smelting.

Jan 1, 2003

By Ann M. Hagni

Microscopic and sub-microscopic gold commonly occurs in the sulfides pyrite (FeS2) and arsenopyrite (FeAsS). To recover refractory gold from pyrite and arsenopyrite, these sulfides are roasted to create porosity and permeability prior to cyanide leaching. A new technique of adding Ca(OH)2 and roasting. lime roasting. is being tested for retention of contaminant sulfur and arsenic and effectiveness of gold extraction. The lime roasting of pyrite at 500°C contains anhydrite (CaS04). oldhamite (CaS). calcium sulfite (CaS03). hematite (Fe2O:J), magnetite (Fe304). and minor amounts of pyrrhotite (Fe1.xS) and pyrite. At 600°C. 650°C and 700°C. the main constituents are anhydrite. oldhamite. and hematite. At 750°C. 800°C. and 850°C. anhydrite and hematite are the predominant phases with minor oldhamite. The roasted arsenopyrite at 450°C contains arsenic sulfides. calcium sulfite. hematite. and minor oldhamite. magnetite. and pyrrhotite. At 650°C. 700°C, 750°C. and 800°C, anhydrite, oldhamite. arsenic sulfides, and hematite are present. At 850°C. the same minerals are present with only minor oldhamite. The textures indicate excellent porosity and permeability at high temperatures. At lower temperatures, rims of low porosity and permeability surround many of the pyrite and arsenopyrite particles, and the complete oxidation process from pyrite to pyrrhotite to magnetite to hematite can be observed in individual particles. Additional process mineralogy techniques employed in this study are electron spectroscopy for chemical analysis (ESCA) and cathodoluminescence microscopy (CIM) in the determination of the calcium-sulfur-oxygen phases. Automated scanning electron microscopy-energy dispersive spectroscopy was utilized to analyze particles for gold content. Reflected light microscopy (RIM) revealed arsenopyrite and pyrite encapsulated in quartz particles of the gold-bearing concentrate, gold roast calcine, and cyanide leach residue.

Jan 1, 1991

A new technology for the treatment of copper nickel-containing concentrate after high-grade matte flotation to blister copper with the production of liquid silicate slags in a vertical autogenous unit with upper oxygen blow has been considered. The copper and nickel behavior in the process of sulphide copper concentrate interaction with silicate melt containing oxide copper has been studied. The general mechanisms of such interaction are found.

Jan 1, 2003

By M. J. Walker

The lead .smelter at Cominco's operations at Trail, B.C. has been undergoing. a modernization program since 1986. In that year a contract agreement was reached with German-based Lurgi GmbH which allows Cominco to construct and operate a lead smelter using Lurgi's QSL process. Cominco Engineering Services Ltd. (CESL), a subsidiary of Cominco Ltd., was contracted to provide project management, engineering, procurement and construction management? services for the project. The new smelter replaces the existing sinter-blast furnace plant ?and will have a capacity of up to 1601000 tonnes per year of refined lead. This new smelting proc.ess results in significant operating cost reductions and major environmental .improvements. Start-up of the new plant is scheduled for the fall of 1989. The metallurgy and the operating parameters, important to the design of the new smelter, are described together with projected deportments of lead, zinc, silver and minor metals. A plant description, will be given for the following major areas that make up the modernization project: the pressure filter operation for the preparation of ,zinc leach residues feed material, the QSL reactor and boiler itself, together with its feed system and process gas treatment, and the drossing plant with a new continuous drossing furnace and oxygen softening and thallium removal. Slag from the QSL reactor will be treated in existing slag furnaces until a subsequent second phase of the modernization is completed in the 1990s.

Jan 1, 1990