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By Shu Yamaguchi

The behavior of halide impurities in pyrometallurgical processes such as Wealtz kiln and MF process has been discussed based on the thermochemical data and the reported data of PbO activity in PbCl2-PbO melts. The role of PbCl(g) has been estimated to be significant in the chloridization evaporation reaction. From reported data on the PbO activity in PbC12-PbO melts, activity of PbCl2 has been calculated by the numerical integration of Gibbs-Duhem equation, and the stability domains and the composition of the liquid phase as well as the vapor pressure of PbCl2 have been estimated as functions of log P2HCI/PH2O and temperature. From the discussion of the path during cooling process on the log P2 HCI . PH2O vs. temperature diagram, the authors proposed a possible dechioridization process that utilize water vapor as a dechloridizer for the direct precipitation of PbO from gas phase.

Jan 1, 2003

By Vladimir Mindin

This paper presents results of thermodynamic investigations and experimental' studies of some essential for pyrometallurgy of sulfide concentrates topics. Among them: 1. Thermodynamic simulation and experimental investigations of roasting process, 2. Thermodynamic investigations of sulfur dioxide off-gases treatment technologies. 3. Investigations on "Mind in -Kiknadze" effect of suppression of sulfur dioxide formation during sulfide concentrates roasting in the vapor containing atmosphere. 4. Thermodynamic simulation and experimental investigations of sulfide concentrates and manganese containing materials co-roasting processes. Some essential aspects of thermodynamic simulation techniques are also discussed.

Jan 1, 1998

By Selvin Yesilay, Munevver Caki, Canbora Bayraktar, Bekir Karasu, Rahmi Imrak

"In this study, the utilization capability of the solid wastes taken from a commercial roof tile and brick factory in Eskisehir of Turkiye has been investigated in the production of stoneware bodies which can be formed by slip casting. At the first stage, X-ray fluorescent (XRF) and X-ray difractometer (XRD) analyses of the wastes were performed. Depending upon the results, a body recipe with an optimum casting concentration was adjusted. The bodies obtained from prepared slips were fired at 1160 oC as glazed and unglazed forms. Then, they were undergone certain tests in order to determine their firing shrinkage values, water absorption levels and optical parameters. To establish what kind of phase formations occurred after firing as a result of waste incorporations into bodies XRD analysis was conducted. Additionally, effects of such a compositional modification on the microstructure of the bodies were examined by a scanning electron microscope (SEM). Consequently, it was concluded that fired roof tile and brick wastes could be evaluated in both glazed and unglazed stoneware bodies. Introduction Stoneware is the general name applied to many wares fired between 1150 and 1300 °C. It has a different and denser structure than those of ceramics produced at lower temperatures. Fired stoneware possesses a lower water absorption value. When matured at a high temperature, it gives a possibility for the use of feldspar as a main ingredient [1-2]. Colors of stoneware can be brown, red, white and most of the times beige. Firing usually takes place in oxidation atmosphere but also reduction can be rarely used. This naturally has an effect on the body colors [3]. Earth, which contains clay minerals, becomes plastic mud when mixed with water, has a capability to be easily shaped and can be hardened without cracking if fired at 900-1000 °C, is referred as one of the brick and tile raw materials [4]. Natural and aesthetic appearances of buildings obtained with brick and tile products, which make them preferable especially for construction sector, are of importance. Because clays being main raw material of that type of productions generally do not exist as pure materials in nature, their usability depends on their mineralogy and impurities they contain [5]."

Jan 1, 2008

By Michel G. Drouet

Dross, a major by-product of all processes involving molten aluminum, forms at the surface of the molten metal as the latter reacts with the furnace atmosphere. It generally represents 1 to 5 wt% of the melt, depending on the process, and contains on average about 50% free aluminum dispersed in an oxide layer. Since aluminum production is highly energy-intensive, dross recycling is very attractive from both the energy and the economic standpoints. The conventional recycling process using salt rotary furnaces is thermally inefficient and environmentally non-acceptable because of the production of salt slags. Hydro-Quebec has developed and patented a new salt-free technology using a rotary furnace heated by an electric arc between two graphite electrodes, called DROSCAR®. A 600-kW pilot plant in operation at LTEE is in use to demonstrate the process. This process provides aluminum recovery rates over 90%, using a highly energy efficient, environmentally sound production method. In 1994, 400 tonnes of aluminum dross were treated in this facility and several tests on various types of dross have also been conducted in early 1995. A report on the results will be presented.

Jan 1, 1995

By P. N. Anyalebechi

The effects of a cross-hatched grooved mold surface topography, casting speed, and superheat on the morphology of solidifying shells of aluminum alloy 3003 have been characterized by a series of immersion tests. The cross-hatched grooves were 0.232 mm deep with wavelength or spacing between 1 mm and 15 mm. The shells solidified at casting speed of less than 10 mm/s on the 1 mm spaced cross-hatched grooved mold surface were fairly uniform with little or no localized variations in thickness. However, the propensity for non-uniform shell growth morphology was exacerbated by an increase in casting speed, melt superheat, and the wavelength of the cross-hatched grooves. This is provisionally attributed to their effects on interfacial heat transfer and wetting of the mold surface by the molten metal.

Jan 1, 2008

By Kenneth S. Coley, Michael Pomeroy, Elaine Chen

Recent work on modeling of BOF steelmaking is reviewed, highlighting the critical aspects of each approach. It is concluded that the most successful models should be based on a deep understanding of the mechanisms and kinetics of the critical reactions. The importance of the decarburization mechanism is discussed with particular reference to its role in droplet swelling or bloating which has a profound influence on the droplet residence time in the slag. Conditions which cause bloating are discussed and the rate determining step is proposed to be primarily nucleation of CO bubbles inside the metal droplet with some influence from growth by reaction at the bubble/metal interface. The discrepancy in the super-saturation ratio required for classical nucleation is discussed and an approach using a surface tension modifying parameter is illustrated. Finally, the role of CO nucleation in controlling the driving force for dephosphorization is discussed.

Jan 1, 2014

By SIMON TIMBILLAH

The chalcopyrite-molybdenite (Cu-Mo) flotation industry is increasingly turning to organic depressants as suitable replacements for inorganic reagents, such as NaHS, due to environmental and safety concerns as well as high consumption rates of the inorganic reagents. This presents an opportunity for improvements or design and synthesis of alternative reagents. Disodium carboxymethyl trithiocarbonate (Orfom® D8) depressant is an organic depressant with a carboxylate group on one end and a trithiocarbonate group at the other end. Fundamental results are shown regarding the interaction of the Orfom® D8 depressant in the bulk flotation of a Cu-Mo concentrate from an operating North American mine. Cyclic Voltammetry on pure copper and Fourier Transform Infrared Spectroscopy (FT-IR) and X-ray Photoelectron Spectroscopy (XPS) measurements on pure chalcopyrite with Orfom® D8 depressant treatment are also reported. Through such characterization techniques a potential adsorption mechanism of Orfom® D8 on the mineral surface was identified and its depressant characteristics in the Cu-Mo flotation systems explained.

By David Van Aken, Arpana S. Murthy, Simon Lekakh, Von L. Richards

"Three heats of 17-4PH stainless steel: with zero, three percent, and seven percent cobalt addition were melted in a 45kg (1 00lb) induction furnace under argon; and cast into no-bake molds and preheated investment shell molds. Specimens were sealed into quartz tubes under vacuum, and homogenized at 1200°C from 2h to 72h. Computational thermodynamics and optical microscopy were used to predict and characterize the microstructures. The lath martensite packet size and the amount of 8-ferrite were observed to be inversely related. A compromise between decrease in segregation and increase in lath martensite packet size was chosen for the optimum homogenization treatment. The specimens were austenitized, quenched, and characterized for retained austenite using x-ray diffraction. Age hardening kinetics were studied at 454°C (850°F), 468°C (875°F), and 482°C (900°F); and, the activation energies for precipitation of copper were calculated. Tensile properties and Charpy V-notch impact energies were measured in the peak aged condition. Fracture surfaces were observed using scanning electron microscopy and Energy Dispersive Spectroscopy. The addition of cobalt was found to be beneficial for the improvement of strength as well as notch toughness.IntroductionSegregation in the as-cast condition is one of the drawbacks of metal casting. This paper presents a study on the homogenization treatment of 17-4 PH cast stainless steel and the effect of cobalt addition on tensile properties and Charpy V-notch toughness. Lattice dilatation studies show that additions of up to 6% Co to iron has a negligible effect on the lattice parameter, whereas both the modulus of elasticity and shear modulus increase with increasing cobalt additions5• An ordering reaction has been reported in cobalt-containing, maraging steels and contributes to the hardening during ageing1-4• Although, cobalt addition in maraging steels has been extensively researched, and has been reported to be beneficial; it has not been explored much in other age-hardening stainless steel systems. In a previous study, the addition of 3% Co in cast 17-4 PH martensitic age-hardenable steel was found to improve the strength and elongation while maintaining the charpy V-notch toughness6."

Jan 1, 2011

By C. Schwandt

Recent research work has led to the development of a new electrochemical hydrogen sensor, which is based on a proton conducting solid electrolyte in conjunction with a self-contained solid hydrogen reference standard and is operated at elevated temperatures. The incorporation of the internal hydrogen reference renders the sensor versatile and user-friendly and makes it attractive for practical exploitation. The present article focuses on the utilisation of the sensor as the integral part of a probe for the quantitative determination of hydrogen in molten aluminium and aluminium alloys. The main features of the sensor and the probe as well as the measuring technique are discussed. Experimental results obtained with the novel analyser in trials under industrial conditions are presented and highlight the good performance of the device.

Jan 1, 2003

By Katsukiyo Marukawa, Manabu Iguchi, Sigeta Hara, Shinichiro Yokoya, Sigeo Takagi

"A numerical analysis and water model study of the mold region of a continuous casting apparatus was performed with a novel injection concept using swirling flow in the pouring tube, to control the heat and mass transfer in the continuous casting mold.As a result, the following results were found:1) By changing swirl strength, it is easy to control the flow pattern as well as the direction of the flow.2) Uniform velocity distribution can be obtained within a very short distance from the outlet of the nozzle.3) Heat and mass transfer near the meniscus can be remarkably activated compared with a conventional straight type immersion nozzle without swirl.4) Swirl helps the superheat in the melt dissipate.S) Penetration depth of nozzle outlet flow is decreased remarkably by the application of swirling.6) For the case without swirl, the peak of the flow moves near the mold-wall with flowing down from the outlet of the nozzle due to the Coanda-effect. On the other hand, peak of the flow moves near the mold axis with flowing down from the nozzle-outlet within considerable short distance, namely axi-symmetric velocity distribution can be obtained within very short distance from the nozzle-outlet.Those findings mentioned above are very useful to control the flow pattern in the billet and bloom continuous casters."

Jan 1, 2001

By Thomas P. Battle

Titanium is the ninth most common element in the Earth's crust, yet only in this century has titanium come into use as an engineering material, particularly in aircraft structures, as the metal, and in pigments, as the dioxide. In this presentation, the metallurgical aspects of processing titanium-containing raw materials will be reviewed. Particular emphasis will be given to the ores and beneficiation techniques which lead to the production of titanium dioxide pigment, which accounts for over 90% of world titanium production.

Jan 1, 1993

By Eddie C. Chou

Phelps Dodge, Inc. (PD) is currently developing a lateritic nicke/Vcobalt deposit in Madagascar. Hazen Research, Inc. provides technical assistance to PD to investigate recovery processes for nickel and cobalt. Various process options were evaluated in laboratory experiments and pilot plant operations. The process selected for the feasibility study consists of feed preparation, high-pressure acid leach, countercurrent decantation wash, sulfide precipitation, sulfide dissolution, solvent extraction, ion exchange, and electrowinning. Among these unit processes, high-pressure acid leach, sulfide precipitation, and sulfide dissolution are applications of pressure technologies. Process development work and design criteria for commercial operations of these unit processes are presented in this paper. Concerns related to scaling in the high-pressure acid leach and the sulfide precipitation processes are discussed. Corrosion of various metal coupons under these environments was examined.

Jan 1, 2000

By George S. Dulikravich

An advanced semi-stochastic algorithm for constrained multi-objective optimization has been adapted and combined with experimental testing and verification to determine optimum concentrations of alloying elements in heat-resistant and corrosion-resistant H-Series austenitic stainless steel alloys. The objective was to simultaneously maximize a number of alloy's mechanical properties. This research will result in a rigorous tool for the design of high-strength H-Series steels and other types of alloys unattainable by any means existing at the present time. Such a material-by-design tool will also be able to reduce or minimize the need for the addition of expensive elements such as Cr, Ni, Co, Nb, Ti, V, etc. and still obtain the optimum properties of an alloy.

Jan 1, 2003

By Bora Derin

The partial pressure ratios of sulfur and oxygen for several copper flash smelting plants were derived using the Reddy-Blander (RB) model and predicted dissolved sulfur contents available in the literature. The sulfide capacities (Cs) of six different flash smelting plants (FeO-CuOo.5- CaO-MgO-FeOu-AlO15-SiO2) slags were calculated. The log (PO2/PS2) versus matte grades of various industrial processes was determined. The PO2/PS2 ratio increased with an increase of copper grade. The calculated partial pressure ratios for the copper flash smelting are in good agreement with those of the experimental data.

Jan 1, 2003

By I. Gaballah

The chalcopyrite ore's anodic and cathodic electrodissolution are studied using a Porous Pulsed Percolated Electrode (3PE) reactor. Stationary solid electrode experiments are also performed to explore the mechanism of electrochemical dissolution of chalcopyrite. Experiments with a low - grade natural ore have been carried out at 25 "C in solutions containing 1 M NaCl and 1 M HCl. Galvanostatic and potentiostatic conditions are employed. The influences of current and potential on selectivity of the chalcopyrite ore dissolution are assessed. Anodic oxidation of this ore leads to a preferential dissolution of iron bearing minerals, whereas cathodic reduction is more selective with respect to chalcopyrite. However, in both cases the electrochemical dissolution is incomplete and the current efficiency is low. Design of the actual reactor has to be modified to increase the bed conductivity and to allow continuous experimentations.

Jan 1, 1994

By John C. Taylor

With growing emphasis on energy conservation and increased concern over the presence of heavy metals in the environment, it is fortunate that most metals are readily recycled. In this respect, metals have a significant advantage over plastics and similar materials used as metal substitutes. For many years a secondary industry has processed scrap copper, nickel, lead and zinc to produce refined metal which has, to varying degrees, influenced the price and displaced the production of primary metal. This paper reviews some of the challenges the industry will face and the changes in process technology which will be required as pressure mounts to increase the amount of metal recycled. In the case of most base metals, this will have an impact on primary metal production; as the tonnage of metal recycled increases, the requirement for primary production, or new metal, will depend more and more on the growth in consumption.

Jan 1, 1993

By Godwin M. Beene

Large scale mining operations started in Zambia in 1913 and rapidly expanded during the post 1930 period with the opening of several mining and processing plants on the present Zambian Copperbelt. As a consequence of poor tailings dumps design methods at the start of the mines, and in view of stringent Government Legislation pertaining to environment in the recent years, Nkana Mine has developed a unique method of dump construction at its current tailings depository, Tailings Dam 15A. This method has enabled the revegetation of the dump retaining walls while construction is still in progress, a situation which was not possible on the older dumps. Cowdung has proved to be a superior fertilizer for providing plant nutrients on the tailings. The new method of dump walls construction and walls rainwater runoff drainage system has almost eliminated tendency of gully formation which is common on older dumps, as rainfall on the Zambian Copperbelt comes in intense thunderstorms. The decanted water from the dump is discharged to the natural environment in a controlled fashion after ensuring that it meets the Zambian Government Statutory requirements.

Jan 1, 1999

By R. E. Moore

The lining systems currently in use in BOF furnaces, certain steel ladles, and the slag line of electric are furnaces were developed during the late seventies through the mid-eighties using a trial and error method of combining aggregate, carbon sources, additives and binders. They are currently based on magnesia, graphite, metal additives and resin binders, the selections of each being tied to the anticipated intensity of the use conditions. The general functions of the respective constituents are well appreciated, however, there is still a great deal that is not known about how the socalled antioxidants protect the graphite nor how impurities from the graphite and the aggregate enter into the wear processes. In a simplified assessment of wear processes, it appears that if the deoxidized layer can be kept very thin, less than 810 mm in depth, and if the viscosity and quantity of the matrix glassy phases can be controlled to resist erosion of the deoxidized layer, lining life can be maximized for the various applications. This paper will discuss the characteristics of the starting materials systems currently being employed for applications requiring a deoxidation function to realize extended wear. It will not attempt to explain all the complex interrelationships between the respective constituents but will point to the potential for improvements through the use of improved constituents.

Jan 1, 1991

By Christoph Beckermann, Kai Liu, Richard A. Hardin

"A two-dimensional heat transfer model for transient simulation and control of a continuous steel slab caster is described. Slab thermal and solidification conditions are computed by the model as a function of time-varying casting speed, secondary spray cooling water flow rates and temperature, slab thickness, steel chemistry, and pouring and ambient temperatures. A solidification model that includes the effects of steel chemistry, cooling rate and mierosegregation on the solidification path is incorporated directly into the caster model. Comparisons between measured and predicted liquidus and solidus temperatures are given for two low alloy steels, and show good agreement. Predicted and measured slab surface temperatures recorded on an operating caster are compared with this transient model and show that the model can predict the temperature response at the slab surface. Results of several simulations are given to demonstrate the effects of changing casting conditions on the slab thermal profile and the solidification end-point. A control methodology suitable for online control of a continuous casting machine is described, and its ability to control the surface temperature profile by dynamically adjusting secondary spray cooling flow rates is demonstrated using the simulator. IntroductionIn order to remain competitive in today's world-wide market for continuously cast steel products, steel producers are finding that it is ever more important to implement process control and to develop a more thorough technological understanding of their casting process. By integrating process control and monitoring into both production and quality control, producers are better able to meet customers' demands for steel of the required quality, quantity, size, grade, and properties at the lowest cost. Computer models used for real-time/on-line prediction and control of continuous steel casters are fundamental tools to accomplish this. Accurate on-line prediction and control of steel solidification and heat transfer allows for more flexibility in caster operation by giving operators the ability to change casting speeds while keeping critical process parameters within required ranges. Such control 'capability also results in more uniform quality throughout an entire casting sequence from startup to shutdown. Furthermore, due to the unreliability of temperature sensors, and the lack of good sensors for important process parameters such as solidification end-point and liquid pool depth, computer-based control models are often the only available option."

Jan 1, 2000

By Versiane Albis Leão

This work aims at the selection of an appropriate eluant for cyanide recycling using ion exchange resins. Based on a literature review as well as on experimental results, the elution of resins loaded with copper and minor amounts of iron and nickel is discussed. The resins Imac HP 555s, Amberlite IRA 900 (Rohm&Hass) and Purolite A860S (Purolite Co) were eluted using either NaCI, zinc and nickel cyanides, hydrochloric acid, sulfuric acid or acid thiourea solutions. The results indicate that saline solutions are effective only with polyacrylic resins (Purolite A860S), failing to desorb the metals, specially the nickel cyanocomplex, loaded on polystyrene-based resins. Cyanide solutions of both zinc and nickel are capable of eluting over 90% of the loaded metals. In contact with pure acid' solutions, iron precipitates onto the resin beads, as Cu(II) ferrous cyanideCu2Fe(CN)6.xH20. Thiourea is able to elute all the three metal cyanocomplexes owing to the increased solubility of copper cyanocomplexes in the presence of this complexing agent. The results demonstrate that a universal eluant is not available and the selection of the most appropriate resin-elution procedure should be based on the specific features of the system under consideration

Jan 1, 1998