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By E. F. Vegman, Ndabezinhle Dube

"In the practice of conventional sintering, production is always afflicted with the problem of being unable to get a uniform quality of produced sinter in the bed. Invariably the top layer of the sinter cake is composed of weak but highly sinter, while the bottom layer is over-fused, forming a sinter that is very strong but less reducible. These symptoms point to a variable distribution of the heat balance in the process of sintering which results in a deficit of heat in the top layers of the sinter bed and an excess of heat in the bottom layers, due to an increasing input of regenerated heat in the heat balance down the bed. This causes losses in the productivities of the sinter machine and the blast furnace.The current work was designed to improve on the solution to the above problem through the establishment of a more accurate combustion zone heat balance of the sintering process. This development is mostly on the method of determining the regenerated heat input in the overall heat balance. Previous methods were based on the assumption that the width and the velocity of the combustion zone remain constant through out its whole life, which is not the case since tests have shown that both its width and velocity increase as the combustion zone moves down the bed. In this work, these factors have been taken into account. Tests and calculations using the model were carried out for haematite and limonitic ores. The high sensitivity of the model to changes in the sinter mix composition and sintering conditions was demonstrated.The results present the following prospects:• The minimum theoretically possible coke breeze consumption during the sintering of any type of iron ore fines, under any sintering conditions, can be established.• The model can be used to control the metallurgical quality of the sinter in any point in the sinter bed since calculation data includes desired basicity, combustion zone temperature and FeO content in the sinter produced."

Jan 1, 2001

By Pratheesh George

Solid state galvanic cell with CaF2 as the electrolyte was employed for determining the thermodynamic properties of Nb-Al binary alloys in the temperature range of 973-1073 K. The activities and activity coefficients of Al in NbAl3 were determined. The experimental procedure and the design and construction of the experimental setup have been also explained in detail. Aluminum activity in NbAl3 increased with increase in temperature and shows a strong negative deviation from ideality. The activities of aluminum in NbAl3 were determined to be 0.0165 and 0.0289 at 973 and 1073 K respectively. The stability of NbAl3 has been compared with other available intermetallic systems.

Jan 1, 2006

By Melinda Channel, Alan W. Weimer, Jonathan R. Scheffe

"There is a need to develop cost effective renewable energy processes for the production of clean fuels that can simultaneously mitigate the U.S. energy/global environmental security issue. If H2 can be obtained cost effectively via the splitting of water using concentrated sunlight, then it’s possible to operate a fuel cell using renewable H2 or to synthesize other fuels based on renewable H2 for generating electricity or for running internal combustion engines. For example, H2 can be reacted with sequestered carbon dioxide (CO2) to produce syngas (H2/CO) via reverse water gas shift (RWGS), i.e. H2 + CO2 ? CO + H2O. The syngas can be catalytically methanated to form synthetic natural gas (SNG) or it can be catalytically reformed to produce liquid fuels such as “green” gasoline via the MTG process (syngas? methanol ? gasoline). The desert SW United States is home to world class sunlight. Fundamental ferrite thermodynamics will be reviewed, an example of the beneficial effect of ferrite surface area on reaction kinetics will shown, and process economics will be investigated for a 100,000 kg/day facility to produce H2.Introduction and Background ThermodynamicsSpinel ferrites of the form MxFe3-xO4, where M generally represents Ni, Zn, Co, Mn, or other transition metals, have been shown to be capable of splitting water according to the two step cycle shown below:MxFe3-xO4 + solar thermal energy ? xMO + (3-x)FeO + 0.5 O2 (1)xMO + (3-x)FeO + H2O ? MxFe3-xO4 + 2H2 (2)This is an inherently clean and sustainable process, as the only net inputs are solar energy and water, and the net outputs are hydrogen and oxygen. Ferrite water splitting cycles are advantages compared to other high temperature water splitting cycles, such as the ZnO/Zn and Mn2O3/MnO cycles, because thermal reduction has been demonstrated at significantly lower temperatures[1, 2]. As a result, overall efficiency may be increased due to the fact that radiation losses increase as the fourth power of temperature, and material considerations for reactor design should be more flexible. Additionally, cycle repeatability has been demonstrated with relative ease as compared to other thermochemical cycles [3-6]. However, the amount of hydrogen per mole that is generated is significantly less than for other high temperature thermochemical cycles due to the fact that only Fe3+ is capable of being reduced at the temperatures of interest[6]. In addition, water oxidation kinetics appear to be very slow, likely due to diffusion or surface area limitations created by near surface oxidation [6, 7]."

Jan 1, 2010

By Patricio Ruz, Gabriel Riveros, Carolina Ramirez, Andrzej Warczok, Rober Treimer

"Continuous converting of copper matte produces slag with high cuprous oxide content. The corrosion of chrome-magnesite refractories with slag of high cuprous oxide content is a major problem. Properties of olivine type of slag make the slag very attractive for matte smelting and converting.Analysis of phenomena determining the slag infiltration into the porosity of a refractory and dissolution of refractory components in the slag allowed for better understanding of the mechanisms of refractory destruction.The results of laboratory scale tests of the olivine slag infiltration into open porosity and corrosion showed dominating effects of slag temperature and cuprous oxide content. The optical and X-ray examination of slag samples permitted the definition of the mechanism of formation of new phases and refractory deterioration. 71"

Jan 1, 2009

By C. W. Whitten

Solis from an abandoned Pb battery processing facility were characterized prior to the selection of the extraction technique. Reflected light microscopy and electron beam methods were used to locate Pb-bearing phases and to quantify the compositions of the phases. It was found that the soils are composed primarily of quartz and feldspars with minor amounts of iron and titanium oxides. Lead is primarily present as an oxide or sulfate that is associated with the silicate minerals. Specific phases identified were PbO; Pb02; cerrusite, PbCO3; angleslte, PbSO4; galena, PbS; and magnetoplumbite, 2PbO3Fe2O3; or plumboferrite PbO2Fe2O3?

Jan 1, 1989

By H. V. R. von Rhaden

Systematic quantitative X-ray diffraction analyses performed on diamond-drill cores originating from the Aandenk formation at the Loraine Gold Mine, located in the Welkom goldfield, Orange Free State, South Africa, have revealed the presence of a number of phyllosilicate mineral assemblages which have not hitherto been reported from this region. Rectorite, a regularly interstratified 1:1 mica-montmorillonite "swelling clay", is found to occur together with paragonite, muscovite, pyrophyllite, kaolinite, and chlorite in highly-altered friable rocks. The presence of rectorite in mill feeds may have potentially serious implications with respect to gold recovery. Quantitative X-ray diffraction analysis for phyllosilicates can be used as an aid to correlation, and also to guide the widths of stopes in underground mining. Rectorite has a unique mode of origin, which is discussed.

Jan 1, 1991

By Shane Andrews, Gustavo Vasquez, S. K. Varma

"The effect of solutionizing time on the corrosive wear behavior of 2014 aluminum alloy has been studied using the impact and continuous mode of scratching techniques. The transient currents (TC) evolved during the scratching of the alloy shows a linear dependence between the TC and the solutionizing time. Higher TC values at longer solutionizing time may be associated with the changes in the concentration of quenched-in vacancies, grain sizes and dislocations generated during scratching. These factors can either create (a) anodic sites or (b) pitting corrosion resulting in the generation of transient currents. The results have been compared with the similar study carried out for 6061 aluminum alloys. This 6061 aluminum alloy shows similar behavior but the rate of TC generation per unit solutionizing time is much lower than 2014 aluminum alloy. The morphological changes in the impact scratches and the TEM investigation in the scratch have been presented in this paper.IntroductionThe technique of studying corrosive wear of composites of 6061 aluminum in the monolithic and reinforced forms has been reported in the literature [1]. Two modes of scratching, consisting of impact and continuous, in a corrosive environment indicate that the composites, containing 0.10 and 0.20 volume fractions of alumina particles (VFAP), have higher corrosive wear rates than the monolith. A graph between the transient current (TC) generated during the impact scratching as a function of solutionizing time at 540°C indicates linear relationship between them. A similar slopes for the composites were observed and the TC values were less for the composite containing lesser VFAP."

Jan 1, 1998

By W. -S. Hwang, R. A. Stoehr, P. Ingerslev

"The flow of molten metal entering complex two-dimensional foundry molds has been modeled using the Simplified Marker and Cell (SMAC) and Solution Algorithm (SOLA) techniques. The molds were for a series of four and three-spoke wheel designs. The computer calculations were compared to physical experiments in which molten cast iron was poured into C02-bonded sand molds. The metal was photographed with a high speed motion picture camera focused through a Pyrex glass window on one face of the mold. To get good agreement between the calculations and the experiments, it was necessary to accurately represent the velocity through the ingate. This was calculated by application of the Bernoulli equation to flow through the feed system. Some difficulties were experienced with mathematical instability, expecially in the three-spoke design with a narrow ingate. This was overcome by using 100% upwind differencing, and over relaxation parameter near 1.0 (i.e. no over relaxation), and variable mesh spacing.IntroductionModeling the flow of molten metal entering molds has the potential for making significant contributions to the design of feed systems. It will supply information to the computer-aided-design systems of the future that will enable the designer to optimize the placement of gates, dimensioning of passages, and designation of casting speeds. Such design criteria have generally been based on application of energy balance (Bernoulli equation) principles to flow in the sprues, runners, and gates. Indeed, this is the easiest way to determine the proper dimensions to give a suitable filling time for a casting of a given size. A number of computer programs, including one by some of the present authors, have integrated such calculations into CAD systems. l Modeling the flow of metal inside the mold cavity requires other techniques that will handle free-surface transient flow. Stoehr and Hwang reported on the application of the Marker-and-Cell (MAC) technique to mold filling problems at the previous conference in this series at Hennicker, N.H. in 1983. 2 Although considerable progress has been made since that time in improving the accuracy, stability, and convenience of these techniques, the shapes to which they were applied remained limited. Also, physical verification of the results of the calculations was limited to water models.The work to be reported in this paper was undertaken with two objectives: (1) to apply these techniques to more complex and realistic shapes, and (2) to verify the results by comparison with flow patterns observed in molten metal poured into actual sand molds."

Jan 1, 1986

By Orlando C. Gaspar

The textures of the ores, the fine mineral intergrowths, the complex distribution of the deleterious minor elements, and the low base metal contents in some ore types, pose many technological problems to the beneficiation of the volcanogenic massive sulphides occurring in the Iberian Pyrite Belt. In particular fine intergrowths of the base metal sulphides with pyrite impose extremely fine liberation sizes (Kao=15 to 25um). The mineralogical, textural and metallogenic studies have provided an understanding of the distribution of vertical and lateral metal zoning in the ore bodies. Mapping of the ore types, carried out by mine geologists, and the metal zoning patterns computed from data base have shown that ore types are distributed as ore lenses, and that vertical and lateral base metal zoning exists in several orebodies. Since ore processing efficiency is affected by ore textures, and because the same mineral often shows different textural features, a relationship between the textures of the feed ores and those of the middlings must be established for all ore types defined at the deposit scale. For supplying, on time, the information needed for the optimization of the concentration processes, empirical methods of determining the mineralogical and textural characteristics of the several ore types have been developed.

Jan 1, 1995

By C. M. Antony

The galvanizing process involves the use of accessory equipment in a series of aggressive environments including zinc ammonium chloride flux, molten zinc at 45S°C (850°F), and acid for stripping of adherent zinc. An Fe-Ni-Cr-Co alloy has been identified which combines excellent strength and resistance to molten zinc and acid attack making it suitable for accessory equipment. The alloy was field tested by a commercial galvanizer as basket material and was found to provide improved life compared to original low-alloy steel baskets while cross-section thickness was reduced 44%. Additionally, other associated processing cost savings were realized.

Jan 1, 1992

By A. Onozaki

The Iijima Refinery was put into operation in 1972 and today has an annual production capacity of 156,000 tons of SHG electrolytic zinc. At the Iijima Refinery, the recoveries of gold and silver are 98.0% and 98.2%, respectively. Gold contained originally in the zinc concentrates reports in the Cu-Pb-Ag residue produced in the residue treatment process. Silver contained in the concentrates is distributed between the Cu-Pb~Ag residue and the copper cake produced in the purification process. The Cu-Pb-Ag residue, which contains gold and silver, is sent to the Oyachi flotatfon plant of the Kosaka Smelter; about 82% of the gold and about 85% of the silver are recovered in the copper flotation concentrate.. In this paper, the distribution of gold and silver in the Iijima. Refinery is discussed and operational results of the Oyachi flotation plant are presented.

Jan 1, 1990

By B. B. Agrawal

Iron ore fines is an area of concern in India. A possible avenue is to use these fines for sponge ironmaking. Work has been carried out to pelletize these fines with coal and a suitable binder, and cure them in ambient atmosphere to retain in-situ reductant. Pellets were characterized for physical strength and metallisation. Critical factors were granulometry was percentage of coal & binder. In laboratory tests, pellets got metallized faster compared to lump ore. Large-scale trials were conducted in a 12-meter long rotary kiln plant. For 90% metallization, required residence time was only 60 minutes against 240 minutes for lump ore. Coal requirement also decreased. Investigations established the fast reduction nature of pellets. This is due to reduction-reactions occurring simultaneously at many sited within the composite pellets, in addition to the diffusion of reducing gases from the surface of the pellets to its core. The developed process is a value addition in the conventional pelletmaking and is environment-friendly also.

Jan 1, 2006

By B. S. -J. Kang, M. A. Alvin, J. M. Tannenbaum

"A load-based micro-indentation technique has been developed for damage assessment and non-destructive spallation detection of TBCs at room temperature. This micro-indentation technology has been further extended to the development of a high temperature (HT) test methodology. Elastic modulus calibration tests performed on Hl 3 Tool Steel to 500°C and Haynes 230 at 1000°C displayed excellent agreement with reported values. Moreover, indentation creep tests of Haynes 230 at 1200°C were found to be in agreement with known creep exponents as well. Finally, a HT thermal flux indentation apparatus was assembled for conducting TBC turbine component testing under high temperature moisture-containing environments (= 50% steam with controlled gas content temperatures up to 1250°C). Description and design considerations of this test apparatus are discussed. Preliminary tests of ReneN5/MCrAlY/APS TBC coupons in steam/air environments with in-situ HT micro-indentation testing are conducted. Furthermore, the coupon is removed and examined for damage assessment at periodical intervals.IntroductionLoad and depth relationships acquired throughout the indentation process provide insight to material mechanical properties such as elastic modulus and hardness. Unloading segment analysis of these load displacement curves are utilized in the acquisition of a material's elastic properties. Yet, indentation tests are complex processes involving contact mechanics, material nonlinearity and even fracture mechanics. Thus exact analytical solutions for these processes are difficult to obtain. As a result, much of the current knowledge regarding the indentation process has been acquired through experimental methods and finite element simulations. Initial efforts by Tabor resulted in the application of spherical indentation to obtain post-yielding stress/strain relationships [1]. Soon thereafter, analytical load-depth relations for elastic indentation were developed [2], yet it was Lure who further derived the explicit relationships for both spherical and conical indenters [3]. Improving upon this, these interactions were later extended to indenters with various geometries by various researchers [ 4]. Additionally, by establishing the linearity of the initial unloading slope within the load-depth curve, a relationship between elastic indentation depth, maximum load, unloading slope and indenter geometry was established [5]. From this a theoretical method by which elastic modulus could be determined was established."

Jan 1, 2011

By E. J. Peuraniemi

Oxidation of chalcopyrite concentrate and two low-iron copper mattes were studied using a laboratory scale laminar-flow furnace simulating the phenomena taking place in different zones of the reaction shaft of a flash smelting furnace. In the experiments, screened fractions were fed into the furnace and sampled after short reaction time intervals by quenching them into a water film. Experimental conditions included temperatures of 1100 and 1300°C with reaction gas oxygen contents from 21 to 75 vol.%. Samples were analysed chemically for Cu, Fe and S to define removal rate of sulphur. Optical and scanning electron microscopy with EDS-analyser were used to examine the samples. In this paper, oxidation kinetics as well as ignition of particles are discussed. Changes in particle morphology, size, and composition are viewed to closely define the proceeding of the oxidation, and, consequently, to compose a detailed model of dust formation and reaction mechanisms. Data obtained in the experiments broadens the knowledge of physical and chemical phenomena in flash reactions and serves as reference for computer simulations.

Jan 1, 2000

By W. Kasprzak

Modern light metals processing technologies are very complex and involve a diverse set of variables that must be quantitatively evaluated. The most effective way to design new casting processes that deliver specified metallurgical and mechanical properties is to develop a method of simulating the "real-time" process within a test sample of sufficient size. The results can then be analyzed and the required optimizations can be performed. This paper presents a novel method of simulating the industrial casting processes in a laboratory environment using an experimental apparatus based on the principle of high frequency induction heating. The applicability and accuracy of the proposed analytical method is demonstrated, for example, by simulation of the solidification and heat treatment of a test sample composed of two dissimilar materials. The simulation can be used to develop a stress model for an engine block made from an aluminum based alloy with iron cylinder liner inserts.

Jan 1, 2002

By Matthew Jeffrey

Due to the increasing environmental and public concerns over cyanidation, there has been a large amount of research into viable alternative lixiviants. Despite these studies, there is little published data directly comparing the kinetics of gold leaching for each of these alternatives: most of the literature is concerned with gold extraction from ores. This paper presents a detailed kinetic study of gold leaching in cyanide, armmonia/thiosulfate and chloride/hypochlorite solutions. The gold leach rates were measured using a rotating electrochemical quartz crystal microbalance (REQCM). This instrument allows the mass of a gold sample to measured in?situ, with a sensitivity of less than 10 ng. From the results of these studies, it is possible to select experimental conditions where the leach rates of the alternative lixiviants are similar to that for the traditional cyanide system.

Jan 1, 1998

By V. Ramachandran

In view of the increasing environmental regulations that have been promulgated in the last 30 years, non-ferrous smelters and refineries have learnt to handle effectively the process waste streams that need to be bled from the system for impurities' control. The cations of concern are copper, lead, zinc, cadmium, mercury, thallium, nickel, silver, sodium and potassium. Anionic species of arsenic and selenium also need to be addressed, Sulfates and chlorides-not a major concern at present-have come under scrutiny in the recent past. The current paper reviews several treatment options with reference to a) types of waste streams processed b)process chemistry c )discharge options and recovery of treated water and d) sludge disposal. The long term goal of any smelter and/or refinery should be to achieve zero liquid discharge from the plant. Methods to obtain zero discharge are discussed.

Jan 1, 2003

By Ravi Vancheeswaran

The consolidation of ceramic fiber reinforced metal matrix composites is a key process step in the synthesis of high performance composite systems. A simulation tool has recently been developed for predicting the evolution of the composites internal state microstructural variables (eg. relative density, fiber microbendinglfracture, and chemical reaction layer thickness at the fiber-matrix interface) during the consolidation processing of spray deposited composite mono-tapes. A Generalized Predictive Control (GPC) scheme is used in conjunction with the simula-tion tool to design near optimal process paths that minimize fiber damage and reaction product thickness while simultaneously maximizing the composites relative density. The microstruc-tural evolution depends nonlinearly on the process conditions and therefore the scheme uses a constantly updated linearization of the model to optimize the input process variable vector. A control simulation is presented to illustrate the performance of the design scheme and to assess the feasibility of its use for the achievement of goal state microstructures at the completion of consolidation cycles.

Jan 1, 1996

By Stober, Frank Allan

The paper describes the development of components in an lntegrated Furnace Control system for shielded-arc smelting focusing on operation and crucible integrity enhancement. The paper reviews the mechanisms of power, feed and energy input and losses into the shielded-arc smelting process and describes the furnace control system module development and integration to tailor the process. The ultimate success of a furnace control system application is transfer of knowledge, training, and operational support during furnace start-up and ramp-up phases and a model for how this has been achieved is discussed. The control modules of a shielded-arc laterite smelting furnace are described in detail including measured results and screen captures from application in a laterite smelting furnace. This paper focuses on developments in Integrated Furnace Controls tailored to shielded-arc laterite smelting but development of common furnace control modules for improved crucible and tapping operation integrity applied to other furnace processes, including immersed-arc smelting, is also covered. Keywords: IFC, Power, Feed, Supervisory, Control

Jan 1, 2004

By Pengfu Tan

In order to understand and control the formation of dioxins and furans in iron ore sinter plants and to possibly avoid expensive end-of-pipe removal stages, thermodynamic calculations on the stability of PCDD/Fs have been combined with sinter process modeling by means of kinetic simulations and computational fluid dynamics. Three thermodynamic databases of PCDD/Fs, derived using the Group Additivity approach and two computational molecular modeling methods, MNDO and PM3, respectively, combined with the SGTE database have been used to model the PCDDIF formation and the PCDD/F isomer distributions in iron ore sintering. The results show very similar conditions for the PCDD/F formation using the different databases. Concerning the isomer distributions of toxic PCDD/Fs, the calculated data derived from the MNDO method showed optimum agreement with measured values from industrial furnaces. The thermodynamic calculations also proved that the isomer distributions found in combustion processes are equilibrium values, while the concentration ratio of PCDDs and PCDFs in the wind boxes does not represent an equilibrium state. A CFD model of iron ore sintering was developed including the kinetics of 15 relevant chemical reactions with the aim of describing the temperature fields and the gas flow patterns in the sintering bed. On the basis of these information and experimental observations reported in the literature possible pathways for the PCDD/F formation in sinter plants have been identified: PCDD/Fs are formed in the critical temperature region of 250 to 450 °C below the combustion zone, are then carried downwards with the gas and condensed close to the bottom of the sinter bed. Transported to the discharge end with the solid mixture, they are again released into the gas phase when the flame front approaches the bottom. PCDD/Fs are also formed in the last wind boxes when the hot off-gases cool down and reach the critical temperature range. Consequently, methods to reduce the dioxin formation reactions are proposed including inhibitor addition to the sinter feed and off-gas quenching.

Jan 1, 2003