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By S. S. B Wang

Zirconia-based ceramic materials have potential applications in high temperature furnace insulation, hot extrusion and casting dies, pressure nozzles, cutting tools, engine parts and electronic materials. High purity and superfine powders of zirconium oxide (baddelyte) were synthesized from a solution containing zirconium oxychloride and urea under hydrothermal conditions. crystallization of the metastable tetragonal zirconia using magnesium oxide or yttrium oxide as stabilizing agents was successfully achieved. The mechanism of hydrothermal reaction to produce these powders are discussed.

Jan 1, 1989

By Fuming Wang, Lifu Hu, Changrong Li, Ruipeng Pang

The solidification structure of 430 ferritic stainless steel has been calculated in the solidification process by using 3D-CAFE model under the condition of water cooling. The calculated results consistent with those obtained from experiment. Under watercooling condition, the solidification structure consists of chilled layer, columnar grain zone, transition zone and equiaxed grain zone

Jan 1, 2015

By Charles I. Richman

Aquispirillum magnetotacticum (AM) is gram-negative hetrotrophic bacteria that belongs to a class ,of magnetotactic bacteria that have an ecological niche in marine marches and fresh water swamp sediments. Thiobacillus Ferrooxidans (TF) is a Gram-negative, acidophillic chemoliths that may have similar chemical conditions within the cytoplasmic membrane as Aquaspirillum M. to support growth of Magnetosomes. Magnetosomes are cellular bodies that accumulate under slightly aerobic conditions. Magnetotactic motion occurs in an external magnetic field and depends on the medium viscosity. The Atomic Force Microscope equipped with a magnetic tip shows the presence of Magnetosomes in these bacteria strains. The size, shape of magnetosomes in AM and TF strains are characterized.

Jan 1, 1998

By Fabio J. Esper, Wildor T. Hennies, Guillermo R. Martín-Cortés, Francisco R. Valenzuela-Díaz, Antonio J. Santana de Araujo, Maria G. Silva Valenzuela

Seeking to replace carbon-black as filler of rubber in the production of vulcanized goods, researchers from University of São Paulo have studied different materials types as minerals, vegetal or wastes agricultural and industry. Results of rubber composites filled with MA1 a waste of mineral treatment provided by Esper Industries are presented. MA1 was characterized through X-ray diffraction; Thermal analysis; Scanning Electronic Microscopy; and others laboratory methods. The composite and shaped masses were evaluated by these methods plus their mechanical properties such as tensile strength, elongation at break and hardness. Exceptional results were obtained in the mechanical properties evaluated, better than those obtained with the traditional carbon-black. Seeing the kind of material used as filler, it can conclude that the environmental benefit is present, as well as economic development, giving credibility to the use of these alternative material in replacement carbon black.

Jan 1, 2015

By F. J. Tavera

Recently Jameson cell technology has gained acceptance in both mineral and non-mineral applications, mainly because of the high degree of contact between the involved phases in the downcomer, fact that leads to an efficient collection performance. The key for an acceptable performance of the downcomer operation depends on the stability of the jet zone, the mixing zone, and the plug flow zone. in this work the behaviour of the downcomer of a laboratory Jameson cell is reported, as a function of gas hold-up, superficial gas velocity, superficial liquid (or slurry) velocity, and length of the operating zones. The presence of carbon is evaluated in terms of its effect on the gas hold-up and bubble surface area flux. The influence of the downcomer operating conditions on the gas-liquid disengaging cell is presented. Keywords: Jameson cell, downcomer, gas hold-up, mixing, plug flow, conductivity.

Jan 1, 2003

By Hongfa Hu, Stavros A. Argyropoulos

"This paper describes a mathematical model which simulates numerically reaction driven fluid flow phenomena. The driving force of this reaction is an exothermic heat of mixing. In addition, the model predicts the heat and mass transfer phenomena where both heat source and heat sink co-exist in close proximity. The heat source is generated by an exothermic reaction. The heat sink is formed by a moving boundary such as the melting of a solid. This type of phenomena occur quite often in various metal processing operations in which exothermic additions are immersed in liquid metals. The model is based on the SIMPLER algorithm and uses an enthalpy method to predict the fluid flow, temperature, and concentration fields. The results indicate that the exothermic mixing reaction was responsible for an abrupt rise in temperature around the moving boundary. The intensity of this reaction was also found to be responsible for the enhanced convection of fluid and the acceleration of the moving boundary. The modelling results were also verified by experimental work which included velocity and temperature measurements in a low temperature physical model. IntroductionAlloying additions are used extensively in the treatment of liquid metals during metallurgical processes. The alloying additions introduced into liquid metals can be classified into various classes, each of which follows its own route[l]. As a major group, the exothermic additions follow two different steps during their assimilation into liquid metals. In the first step, upon immersion, a metal shell solidifies around such additions, and then melts back. At this point, the second step commences. During this second step, due to the mixing of the addition with a liquid metal, an exothermic reaction occurs, which liberates large amounts of heat, resulting in an enhanced convection in the liquid metal surrounding the addition."

Jan 1, 1994

By Jafar Safarian

A new kinetic modelling technique has been applied to study the rate of MnO reduction from slags by dissolved carbon in liquid iron. Based on a consideration of the fundamental reaction kinetics, a general differential equation for the slag reduction process has been formulated, which then is solved analytically for certain special cases. By re-writing the solutions in a dimensionless form the poorly known kinetic constants are eliminated, which makes the model both flexible and applicable to a wide range of experimental conditions. For example, changes in process parameters such as temperature, metal composition, slag composition, gas composition can readily be captured along with variations in the crucible geometry. Based on a comparison with a series of experimental reduction curves being reported in the literature, it is concluded that the predictive power of the model is surprisingly good, yielding outputs that are both reliable and physically reasonable. An attractive feature of the model is that it provides an alternative way of calculating the activation energies from experimental reductions curves. For example, it suggests that the activation energy for the reduction of MnO by dissolved carbon in liquid iron is about 90 kJ/mol, which is different from the previously reported activation energies. The model also suggests that the crucible geometry, which affects both slag the volume and the resulting slag/metal interfacial area, has a significant influence on the overall reduction kinetics. This design parameter is a key to further optimisation of the process on an industrial scale.

Jan 1, 2006

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 Brian R. Green

Resin-in-pulp (RIP) technology has been developed for recovery of gold. It is now time to look forward to the potential for application of the technology to other situations. Some cases have been identified and have merited preliminary testwork. Four examples, which illustrate the potential of RIP, are dealt with in this paper. These include removal of metal-cyanides from pulps, recovery of manganese that is difficult to wash from filter cakes, recovery of nickel from low grade pulps, and recovery of zinc from process residues. The discussion includes descriptions of the problems, factors that affect the choice of resin, and factors that will affect the economics of the process.

Jan 1, 1998

By Nozomu Hasegawa

The phase diagrams and microstructures of the slags in the Mitsubishi Continuous Copper Smelting and Converting Process were studied for the prevention of the magnetite troubles such as accretion build-up on furnace hearths and launders, blockages at the melt outlet, slag viscosity increases and so on. According to the results of those studies, the silica and lime contents in the silicate slag at the smelting furnace, and the lime content in the lime-ferrite slag at the converting furnace were changed, resulting in lower and more consistent copper levels in the discard slag, with much less need for operators to clean melt outlets and launders. However, these changes may decrease the desirable amount of accretion-coating inside the furnaces and thereby reduce furnace campaign lives. Therefore, a method of estimating the magnetite level in the melts was developed, and slag compositions and temperatures have been controlled within the appropriate ranges to prolong furnace lives and also prevent magnetite troubles.

Jan 1, 2003

By J. Garvey

The new Cyprus Miami electrolytic copper refinery was commissioned in October 1994. The refinery has been operating at its design capacity of 190,000 short tons per year, and in recent months to 110% of design capacity, producing high-grade electrolytic copper cathodes. Basic and detailed engineering, performed by Fluor Daniel Mining and Minerals, incorporated state-of-the-art technology, including stainless steel cathodes, automated electrode handling, fine-filtering of the commercial electrolyte, autoclave leaching of the anode slimes and other techniques. The major design goals have been safety of operation and quality of the product. Relatively high cathode current densities of 30 amperes per square foot and greater have been applied since start-up. Cathode current efficiencies of over 94% have been achieved since the latter part of 1997. The cathodes were certified on the Comex and LME markets during 1996. ISO- 9002 certification is in progress and should be completed during the first quarter of next year. This report discusses some of the studies that were performed to obtain an optimum layout for efficient materials handling and to create optimum conditions for producing high quality cathodes. A description of the design and operation of the anode slimes facility, including decopperizing with autoclave leaching, is provided. Finally, a description of the start-up experiences and present operation of the electrorefinery are presented.

Jan 1, 1999

By Stanko Nikolic

Ferrous calcium silicate slags are potentially important for future practice in copper converting operations and processes and can be described by the ?Cu2O?-FeO-Fe2O3-CaO-SiO2 system. Despite its industrial importance the phase equilibria in this system have not been fully investigated. Characterization of this slag system is necessary to improve the design and optimization parameters of new processes, including fluxing and operating temperatures. Experimental methods have been developed to investigate the phase equilibria of these slags at copper saturation and without copper. This technique involved equilibration of samples at a fixed oxygen partial pressure, rapid quenching, and analysis of the compositions of phases using electron probe x-ray microanalysis (EPMA). Liquidus and solidus data are reported for the primary phase fields of spinel, wollastonite and tridymite at 1250oC and an oxygen partial pressure of 10-6atm. The resulting data has been used to construct liquidus isotherms in the ?FeO?-CaO-SiO2 system both in equilibrium with and without molten copper. The experimental results were compared with the predictions of a thermodynamic computer package utilizing a self consistent thermodynamic database. The predictions of the model were in good agreement with the experimental isotherms when projected onto the FeO-CaO-SiO2 section, however the copper concentrations in the liquid phase at copper saturation were lower than predicted using the current database of the model.

Jan 1, 2006

By Shin-ya Kitamura

Kinetic modeling is very important to understand steelmaking reactions. The coupled reaction model proposed by Prof. D.G.C Robertson is the best suited program, and therefore, the author has applied it to the various steelmaking reactions, a few examples of which are discussed. Hot metal dephosphorization occurs under non-equilibrium conditions as it takes place between the slag, which has a high oxygen potential, and the hot metal, which has a low oxygen potential. A process simulation model based on the coupled reaction model was constructed. This model considers the solid and liquid slag, liquid metal phases, and the reaction between the solid and liquid slag, besides the reaction between the liquid slag and liquid metal. Using this model, the ruling factor to increase the reaction efficiency of dephosphorization has been verified. In the secondary refining process, the values of inclusion composition calculated by the thermodynamic model, under the assumption of equilibrium with the metal composition, were found to be different from those observed in practice. A kinetic model, incorporating the reactions between slag, metal, inclusion, and refractory has been postulated, and the composition change of inclusion during treatment has been analyzed.

Jan 1, 2014

By Jens Decker

"In consideration of energy savings the ideal refractory furnace lining should possess the following features:??Lowest thermal conductivity possible in order to avoid heat loss.??Single component lining in order to allow freeze plane changes caused by wear, infiltration and temperature changes of the furnace.??Resistance against mechanical wear from cleaning tools and stirring in order to allow maximum output without equipment downtime due to maintenance.??Resistance against thermo-chemical attack from aluminum and alloying elements.However, refractory materials with a low thermal conductivity typically possess a higher porosity and this leads to lower strengths and resistance against chemical attack and wear. Hence, as a compromise, multi layer linings are required in order to meet energy saving standards.In this paper we present the features of chemically phosphate bonded dense and light weight refractories and how such refractories can contribute to energy savings.IntroductionIn several reports, the U.S Department of Energy published theoretical energy requirement limits for aluminum production as a future target, with recommendations on how to reduce energy losses. The reports provide a basic description of the processes and equipment involved, their interrelationship, and their effects on energy consumed. The report uses onsite process measurements as benchmarks that industry uses to compare performance between facilities and companies [1]. The energy consumptions used in this paper are primarily based on numbers published by the Department of Energy. However, their reports do not consider the potentially significant energy losses from process interruptions due to a lack of preventive maintenance and material deterioration over time. Further, the Department of Energy reports do not consider equipment costs and availability. Energy input to metal output depends on factors beyond energy losses through the furnace wall. For instance, a focus on energy savings should consider fixed output costs due to depreciation of the equipment and the plant."

Jan 1, 2009

By C. Dresen

This paper discussed the reaction kinetics of the reduction of industrial phosphate pellets for P4 production. In the reduction process of various phosphate ores, the following parameters were investigated: Diffusion of the phosphorus oxide and other gaseous products from the reaction mixture after having been reduced on the reductant (coke) surface. Influence of silica on reaction kinetics. Temperature influence. Influence of mineralogy and morphology (different ores). Particle size influence of silica and coke. Experiments were carried out in a vertical tube furnace with 2 ores, 2 types of silica and one type of coke. Selected experimental conditions simulated furnace conditions. The following conclusions could be made: Reaction rate increases with the addition of SiO2 into the pellet. The reaction rate increases above 1350°C (melting temperature of the slag). Mixing different ore types in the pellets leads to differences in reduction kinetics. Particle size of the coke particles influence reduction kinetics. The amount of slag formation is influenced by silica addition, coke size and temperature.

Jan 1, 2002

By G. Taylor, S. Bounds, G. Moran, M. Cross, K. Pericleous

"A variety of interacting complex phenomena takes place during the casting of metallic components. Here molten metal is poured into a mould cavity where it flows, cools, solidifies and then deforms in its solid state. As the metal cools, thermal gradients will promote thermal convection which will redistribute the heat around the component (usually from feeders or risers) towards the solidification front and mushy zone. Also, as the evolving solid regions of the cast component deform they will form gap at the cast-mould interface. This gap may change the rate of solidification in certain parts the casting, hence affecting the manner in which the cast component solidifies. Interaction between a cast component and its surrounding mould will also govern stress magnitudes in both the cast and mould - these may lead to defects such as cracks.This paper presents a multiphysics modelling approach to this complex process. Emphasis will be placed on the interacting phenomena taking place during the process and the modelling strategy used. Comparisons with plant data are also be given."

Jan 1, 1999

By Daoxin Wu

Originated from(C4H9O)4Ti, nano--rutile TiO2 was synthesized by low temperature hydrolysis process in this paper. After being prepared by decomposing ammonium tungstate and covering on the surface of TiO2, TiO2/WO3 were characterized by means of X-ray diffraction(XRD), UV--vis difuse reflectance(DRS), fluorescence spectrum (FS). Results showed that with the increase of the supported concentration of WO3, the reflectance of DRS and the fluorescence spectrum intensity of TiO2/WO3 decreased accordingly, which indicated the powder?s increase in light absorbance and the decrease in luminescence respectively; with the increase of calcined temperature, the reflectance of DRS increased.

Jan 1, 2009

By P. C. Guillaume

Global plant modernizations or expansions cannot be considered in the same light as any other industrial investment project. Relationships between the partners, relationships and communications with the client, structure and organisation of the teamwork, schedule of the work, and a lot of other tasks and missions devoted to external contractors have to be defined considering one fundamental input: an operating plant. For an engineering company expert in processing, like UM Engineering, such a context requires a specific approach as well as specific procedures able to efficiently challenge the generated constraints. First of all, even if a detailed audit had been conducted at the beginning of the conceptual engineering phase, new elements will be discovered during the preparation and realization of the project, and must be continuously integrated. Consequently, a close proximity to the site is necessary. This is one reason why UM Engineering, most often, works in partnership with a local engineering company. The second important point for the client is that the operation must not be interrupted during the realization. In order to make that possible, UM Engineering has defined a specific project structure and organisation, integrating on a permanent basis the operators (the "users") in the project teams. This paper presents the way UM Engineering copes with this type of "multi-constraints" context with reference to the recent copper cellhouse modernization under realization for the CCR Refinery of Noranda Inc. in Canada.

Jan 1, 1999

By Zenon R. Llanos

"The disposal of spent hydroprocessing (HDP) catalysts in the petroleum refining industry has been a concern in the past due to their classification as listed hazardous wastes. However, because these catalysts have higher metal concentrations than regular ores, and the recent surge in prices for molybdenum, vanadium, nickel and cobalt what used to be considered as a liability for generators is now viewed as a valuable renewable source of strategic metals. At the same time the generation of spent catalysts has steadily risen due to new environmental regulations for low sulfur fuels and an increased appetite of gasoline consumers. This paper will examine spent catalyst market and the role played by Gulf Chemical & Metallurgical Corporation in the reclamation of metals over the last sixty years. Introduction Hydroprocessing (HDP) catalysts are used in petroleum refineries for two main applications: desulfurization and cracking. The catalyst support is alumina or mixtures of alumina and silica. Active metals include molybdenum, nickel, cobalt and tungsten. The selection of catalysts depends on the application and sometimes the cost. The life cycle of HDP catalysts is represented in Figure 1. The catalyst cycle in a reactor varies from continuous to one-two years. Catalysts used in various refining processes are deactivated by coke, sulfur, vanadium and other impurities in the refinery feedstocks and become spent. Refineries can optionally send the spent catalysts for regeneration, metals reclamation or landfilling. Catalysts used for refining heavy crudes often can not be regenerated. Catalysts used with light oils can be reused twice or three times after regeneration. When the option for regeneration is not viable, spent catalysts are send metal reclamation facilities or landfills."

Jan 1, 2008

By R. W. Bartlett

A two step process for treating platinum group metal flotation concentrates Is described while experimental results. The process was designed to be simple and Inexpensive While yielding a high recovery and fast turnaround. Ii consists of electric furnace smelting of concentrate to remove gangue and produce a homogeneous sulfide matte containing all of the base metals and platinum group metals. Sulfide oxidation Is minimized during smelting to avoid Installing an acid plant In the second step, matte Is pressure-leached with oxygen In an acid sulfate system to dissolve Iron, nickel, ?and copper while leaving a residue highly concentrated In precious metals, and typically about 1% of the flotation concentrate mass, A batch process with oxygen titration against the base metal composition of the feed Is used to control the end point of the leach. Sulfides must be eliminated while minimizing the precipitation of hydrolysis products. The leach residue can be smelled to bullion to facilitate sampling accuracy.

Jan 1, 1989