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By Tadafumi Adschiri

"Supercritical water can provide an unique reaction atmosphere for synthesizing metal oxide nanoparticles. Due to the drastic change of properties of water around the critical point, including density, dielectric constant and ionic product, the reaction phase with O 2 or H2 gas and the reaction rate and equilibrium can be varied to synthesize new materials or define particle morphologies. In this work, hydrothermal crystallization experiments are performed with several types of flow apparatus that allow convenient manipulation of variables such as temperature, pressure, and residence time. Key features in the flow modes and material preparation are discussed. The proposed supercritical hydrothermal synthesis method has the following desirable features: i) nanoparticles can be produced, ii) morphology of the produced particles can be controlled with small changes in pressure or temperature, and iii) a reducing or oxidizing atmosphere can be applied by introducing oxygen or hydrogen or other gases. An overview of this method is given for functional material synthesis of significant industrial interest including barium hexaferrite magnetic particles, YAO/Tb phosphor fine particles and lithium cobalt fine crystals.IntroductionHydrothermal crystallization, a method of metal oxide formation from metal salt solutions, is typically used at temperatures ranging from 373 K to 473 K. We are developing a new process for hydrothermal crystallizations that uses temperatures in the range of 673 K to 723 K, which is just above the critical temperature of water1 • 8 • In this work, we refer to this process as supercritical hydrothermal synthesis. The supercritical state of water allows one to vary reaction rate and reaction equilibrium by shifting the dielectric constant and solvent density with pressure and temperature. From of our research on material production in supercritical water, we have identified the following specific features of the supercritical hydrothermal synthesis method: (i) ultrafine particles can be produced, (ii) morphology of the produced particles can be controlled to some extent with pressure and/or temperature, and (iii) a homogeneous reducing or oxidizing atmospheres can be provided by introducing gases, such as O 2, H2, H2O 2• and so on.1"

Jan 1, 2000

By M. Rosales

By a physical and mathematical modeling, the behavior of the tri-dimensional waving, and the movement of the gases at the Teniente Converter was studied. The mathematical model considers the condensed phases of white metal and slag, along the gas phase, and includes the k-e model for the turbulence description. Both the physical model and the mathematical model allow to conclude that from a fluidynamic stand point the Teniente Converter clearly can melt 3000 tpd of concentrates. Also, both models are suitable to predict the slag fluidynamics and its spacial distribution inside the Teniente Converter, and the splashing in the tuyere zone as well.

Jan 1, 2006

By R. Gampala

The consolidation of mom matrix composite monotapes occurs by the plastic (time independant) and creep deformation of monotape asperities. Past models of the process used seperate micromechanical analyses of the contact deformation by (rate independent) plasticity and power law creep (i.e steady state creep). These models are now used to simulate consolidation and to optimize/control consolidation process cycles so that the composite's microstructure is "steered" to, a user defined goal state. However, the models do not incorporate the sometimes dominant transient creep process and the instantaneous response of the plasticity mechanism causes finite discontinuities in the microstructure state vector field and therefore eliminates the possibility of using the powerful array of trajectory optimization schemes that all require continuous vector field for optimization and control. To overcome this problem, a inified creep/plasticity constitutive model that results in a continuous state vector field is used to rederive the contact deformation response during monotape consolidation. The contact blunting of a laterally constrained hemispherical asperity is first analyzed and its response represented by two coefficients; one relating the contact area to the blunting strain (C), the second, the mean contact pressure to the blunting rate (F).The C and F coefficients for this unified blunting problem are then obtained by finite element analysis, and detailed results presented for two composite matri-ces of topical interest (Ti-24A1-11Nb and Ti-6Al-4V).

Jan 1, 1996

By B. Holleis, M. Potesser, D. Spoljaric, H. Antrekowitsch, A. Hengelmolen

"During the past only an optimization of metallurgical furnaces were done without attention on the burners. Nevertheless, furnaces without burners are impossible to use in the primary and secondary nonferrous metallurgy in an economic way. Since the energy cost is increasing and the environmental protection is becoming a global issue, the burners are in the focus of several investigations and optimizations. One possible way is the combustion by oxygen. By using oxygen, the flame temperature increases and therefore, fuel accordingly money could be saved by having a low amount of harmful substances like NOx in the off gas. This paper describes a new burner system which combusts fuel with oxygen or air by diluted combustion, hence low pollutants in the off gas. Furthermore the effectiveness of the burner characterized by off gas analyses and simulation in the new development chamber, but also practical tests at an aluminum smelter are described.IntroductionIn 2005, Messer Group established a technology competence centre for metallurgy in Gumpoldskirchen (Austria), with the aim to develop oxygen burners which satisfy today’s and upcoming standards of legislation as well as customer requirements. With the assistance of the Development Sponsorship Fund (FFF) of Austria, cooperation with the University of Leoben was agreed on. With the long term experience of the Gas-Wärme-Institut “GWI” in Essen (Germany) and the University of Leoben, different new burners have been developed."

Jan 1, 2008

By Fan Xiao-Hui, Jiang Li-Juan, Chen Xu-Ling

"In order to solve air leakage of sintering testing cumbersome, inaccurate results, and other issues, the sinter machine air leakage characteristics were studied, and combining the mathematical modeling and the field detection. The temperature before air leakage was calculated by mathematical model, energy balance equation was established according to sintering process, using Adams prediction correction method which has stronge stability and high precision, to solve hyperbolic partial differential equation with astringency problem. The temperature after air leakage is detected by instruments, according to energy conservation calculation the sintering air leakage rate. According to the sintering continuity and periodicity, sintering air leakage location diagnosis expert system was established to judge specific air leakage locations.IntroductionStrengthening of modern blast furnace production depends on the quality of the raw material preparation to a large extent [1]. Technical and economic index of modern blast furnace production is advanced; the most important reason is the use of concentrated feed. Sintering plant is the ""kitchen"" of blast furnace’s concentrate. As we all know, sintering plant is major energy consumption of steel plant, in sinter process energy consumption, the solid fuel consumption of total energy consumption is 75%~80%, power is 13%~20%, ignition and combustion is 5%~10%. To reduce the air leakage of sintering plant is an effective measurement to save energy consumption. At present, our air leakage of sintering compared to the other developed countries is still a long way to go. Japan’s air leakage rate is about 30%, and 35%~60% air leakage of sintering machine at home, a big gap exists between the plants. At present the determination of air leakage is all for manual operation, long measuring period, considerable manpower and resources, and the results are significantly affected by operation. For air leakage of sintering control lag issues, research and development of diagnosis expert system for on-line monitoring model for air leakage and, through this research can reduce the use of detection equipment, detect sintering air leakage, improve the yield and quality of sintering production, reduce energy consumption, and extend equipment life span."

Jan 1, 2012

By X. Jay Gao

A fast high-temperature carburizing process integrated with materials design and optimization via a systems design approach was developed to significantly reduce process cycle time. Process experiments were focused on boost cycles to obtain a robust boost process and investigate surface reaction kinetics, primary carbide formation and dissolution. Weight gain and microhardness were measured, all showing evidence of non-monotonic time evolution for longer boost times at higher temperatures. Optical and electron microscopy and other techniques have been used to identify possible carbides, their location and types. These results assist the picking of first boost time with least variation rate in terms of content of case carbon and carbides, dissolvable in subsequent diffuse if any. The results also provide critical information to properly formulate surface reaction kinetics and diffusion and formation kinetics of carbides modeled using DICTRA. Keywords: high temperature vacuum carburizing, partial pressure carburizing, heat treatment, process development, carbide, case hardening, microstructural analysis, over carburizing

Jan 1, 2003

By Yuhua Pan

Generic mathematical models have been developed for simulating heat transfer in two types of slag resistance heating electric furnaces for sulphide smelting: i) six-electrode-in-line rectangular furnaces and ii) three-electrode circular furnaces. The models are based on three-dimensional steady-state heat transfer of conduction, convection and radiation. Solidification of liquid slag into solid slag by water-cooling units, for use as freeze lining of furnace walls, is also considered in the models. The developed models are capable of providing predictions with reasonable accuracy for electric furnaces on 1) temperatures in slag, matte, cooling water, freeze lining and other solid regions as well as temperatures at various fluid/solid interfaces, 2) freeze lining thickness, 3) furnace smelting rate and 4) furnace heat loss rate. These computer models are built into executable application programs that are very efficient, with execution time less than one second, and can be easily portable to most computing platforms. This paper describes, as an example, the modelling results on heat transfer in six-electrode furnaces. The major modelling results show that in six-electrode furnaces uniform electric power inputs to the electrodes likely lead to low temperature regions close to slag and matte tapping ends of the furnaces, and the power input and the formation of air gaps between freeze lining and cooling units have significant influences on the thickness of freeze lining maintained by the cooling units.

Jan 1, 2006

By Kampe. S. L., Baker. Andrew H., Tony Zahrah

"Experimental heats of reaction for the formation of several Al3Ti + TiB2 intermetallic composite formulations have been determined utilizing bomb calorimetry. To overcome the kinetic constraints and achieve ignition in these formulations, a boron (B)/potassium nitrate (KNO3) initiation aid was incorporated within the blended reactant compact. The heat contribution from the initiation aid was regressed to provide estimates of the heat of reaction of the nominal formulations. Powder x-ray diffraction was utilized to identify the products of the reaction and discern any differences between the predicted equilibrium products of the formulation and the actual products.IntroductionReaction synthesis is a technique for the creation of ceramics, intermetallics, and in-situ composite materials [1]. Reaction synthesis is defined by its self, propagating mechanism, where the energy liberated from a localized reaction within a green powder compact is enough to carry the bulk reaction to completion. Achieving a self, propagating state can be achieved in variations of two primary methods of initiation: uniform volumetric heating and directional propagation [2].Uniform volumetric heating involves subjecting a green compact of the unreacted formulation to uniform heating in a furnace to encourage diffusion to initiate the reaction (Figure 1a) throughout the bulk material. Directional propagation utilizes a point heat source at one section of a green compact of unreacted formulation (Figure 1b). The localized exothermic reaction at one point in the compact then initiates the reaction in the section of the compact adjacent to it and fully propagates throughout the entire compact until completion. Initiation of the localized reaction is generally associated with the melting of the constituent with the lowest melting point, with instantaneous initiation of the reaction usually occurring close to that melting point [1]. This melting point can be high in some systems of interest, such as the titanium (Ti) and boron (B) system in equation 1:"

Jan 1, 2011

By Gunnar Eriksson

Computer simulation has become an everyday practice in thennodynamic and materials research. Advanced thennochemical algorithms take into account heat transfer effects and salient reaction kinetics when applied for process models. In particular, the combination of mass transfer or overall reaction rates with multi-component Gibbs energy minimisation provides an effective tool for simulation of industrial thennochemical processes and processing of materials. In this work the combination of rate factors with the Gibbs energy technique was studied by using the novel program ChemSheet, which operates through Microsoft's Excel® spreadsheets. Such processes as, for example, CVD of pure silicon production, titania pigment manufacturing, vapour pressure of Mercury in amalgams (in Hg-Iamp manufacturing) and melting behaviour of low-temperature alloys have been modelled. Provided that the thennochemical data is available simulations can be performed with any thennodynamic system. The calculation can be performed as an affinity study without a particular reactor model or with a specific reactor scheme.

Jan 1, 2001

By Carl W. Dalrymple

A wide variety of contaminants (heavy metals, suspended solids, colloids, oils, organics) have been successfully removed from wastewater using an electrocoagulation process. An innovative electrocoagulation system is described. This process involves a procedure which subjects dissolved and suspended wastewater contaminants to the simultaneous addition of metal ions in the presence of direct current. During the treatment process Ionic and other charged particles in the wastewater are neutralized with oppositely charged ions generating the coagulation of contaminants: The process Is called CURE, and' presented here with application to wastewaters containing mainly heavy metals.

Jan 1, 1995

By C. E. Dodson

Conventionally hydrometallurgical recovery processes from sulphide concentrates include roasting, leaching, precipitation, impurity removal and zinc electrowinning. The use of the novel (yet commercially proven in other mineral and metallurgical industries) TORBED process reactor for the flash roasting of sulphides will be proposed. The potential advantages in its application will be discussed including very fine particle processing capability, lower cost smaller roasters, waste minimization, improved leaching efficiency and overall process simplification.

Jan 1, 1999

By A. Niedbalska

A technique was developed for low pressure diamond synthesis using a specially prepared glassy carbon. The glassy carbon is produced in the form of solid plates by slow carbonization process of phenol formaldehyde resin interrupted at temperatures of 1273° K, 1073° K, and 923° K. The diamond synthesis is performed using cobalt plates as a catalyst-solvent. Synthesis was carried out at applied pressures of 6.0 and 3.8 GPa and a temperature of 1970° K and 2170° K. The products were analyzed by the x-ray powder dyffraction method and by microprobe to identify the diamond crystallites. The samples were taken from the place of contact between the glassy carbon and the cobalt catalyst. They were separated from the charge by a chemical method. Diamonds of the best form and the largest size were obtained at pressures that were much lower than those used in the traditional graphite method of diamond synthesis.

Jan 1, 1989

By Xinghua He, Shujing Zhu

"Cycled fluidized bed ash (CFBA), a significant portion of fly ash produced from coal-fired power plants and rejected from the ash classifying process, has remained unused due to its high free CaO and S03 content. It is necessary to extend research on the method to reduce the expansion and improve the compressive strength by some effective chemical activator. This paper presents experimental results on the expansion by Le chaterlier tester and the compressive strength. Hydraulic ash-zeolite (HAZ) cementitious material was blended as the chemical activator to study the effects of the activator on the expansion and the compressive strength. The results show that HAZ can not only reduce the expansion, but also increase the prisms compressive strength. Scanning electron microscope observation and X-ray diffraction analysis indicate that the main hydrated products of the sample are calcium hydroxide, ettringite, zeolite and calcite, which can explain the results of the expansion and the strength tests.IntroductionNearly 80% of the electricity in China is produced by coal-fired plants, which results in the production of a large quantity of coal combustion residues, among which coal fly ash is the major component. Because of that the air-pollution becomes heavier as time going on. Cycle-fluidized-bed-combustion systems are retrofitted to meet air-emission standards mandated by China Clean Air Act. Cycle fluidized bed ash (CFBA) will present new challenges for coal-combustion byproduct management. The use of cycle-fluidized-bed ash as a cement replacement in concrete is the most attractive one because of its high volume utilization and widespread construction. However, the replacement of cement with cycle fluidized bed ash in Portland cement concrete usually increases the expansion and decreases the early strength of concrete. In many research of this field, most of them were focus on the activation of pozzolanic activity of CFBA and to make all kinds of blend cement. A number of studies had been carried out on the activation of CFBA using chemical activators. These studies involved using different activating methods including alkali activation and sulfate activation 11, 2]. The former involved the breaking down of the glass phases in an elevated alkaline environment to accelerate the reaction [3, 4]. The later is based on the ability of sulfates to react with aluminum oxide in the glass phase of CFBA to produce ettringite that contributes to the strength at early ages [5-7]. With respect to sulfate activation, the use of gypsum and sodium sulfate had been well studied [5-8]. HAZ is one of HAS sub-products which is a patentd chemical activator made by Wuhan University (ZL98113594.3). It had been used to activate CFBA to produce blend cement in many Chinese engineering projects and time has told us that it is a good activator."

Jan 1, 2012

By Kenneth G. Thomas

This paper reviews the alkaline and acid gold autoclaving experiences gained at Barrick Gold Corporation. Alkaline autoclaving was operational at Barrick Mercur, Utah, U.S.A., on carbonaceous/sulphide refractory ore for eight years commencing in 1988. Acid autoclaves have been operational at Barrick Goldstrike, Nevada, U.S.A., on sulphide refractory ore since 1990 and now process 17,500 stpd of ore through six large autoclaves. Information is presented on operating costs, materials of construction, reagent requirements and flow sheet developments that reduced capital and operating costs.

Jan 1, 2000

By James P. Bennett

The successful reuse/recycling of refractory materials after removal from industrial service is limited because of contamination, the low value of spent materials, the low cost of virgin raw materials, the lack of driving forces such as regulations or taxes, and low disposal costs. Most spent refractory is disposed in landfills. Concerns over future liability for waste materials, corporate images, and IS0 14000 have helped to encourage recycling at some companies. The recycling practices and application for spent refractory materials at facilities successfully recycling used refractory materials will be discussed, with emphasis on similarities.

Jan 1, 2002

By William Bourcier

Geothermal Brines are a significant potential source of valuable minerals and metals. These brines are water that is heated by the natural heat flow from the depths of the earth. Hotter brines, typically with temperatures greater than 120°C, are used to generate electricity. Lower temperature brines are directly used to supply thermal energy to applications such as agriculture, aquaculture and process/domestic heat. The geothermal waters have had intimate and lengthy contact with the layers of the earth?s crust that they flow through, resulting in dissolution of minerals and metals from the rocks, and solution into the hot water. These aqueous solutions can be processed to recover minerals and metals. Some potential products include silica, zinc and lithium, along with other materials. Recovery of minerals and metals from geothermal brines can be viewed as ?solution mining by nature?, followed by application of known or new hydrometallurgical techniques for isolation and purification. This paper discusses the opportunities, the processes, the challenges, the current status, the economics and the potential for recovery of minerals and metals from geothermal brines.

Jan 1, 2006

By Richard D. Hagni

The mineralogy of dusts from the lead sinter and lead blast furnace at the Doe Run Smelter at Herculaneum, Missouri is being studied by reflected light microscopy and scanning electron microscope-energy dispersive spectroscopic analysis (SEM-EDS). Oust from the sinter plant consi5ts of abundant slag and galena particles, and lesser amounts of coke, sinter, and chalcopyrite particles. In contrast, dust from the blast furnace consist of abundant coke and sinter particles, and lesser amounts of slag, galena, chalcopyrite, metallic lead and lead-copper particles. The particles in dusts from remote sampling sites !-l mile from the sinter plant and blast furnace are fine-grained and composed principally of calcium-aluminum silicates that are locally derived, but some of the larger particles consist of sinter, slag, galena, and other minerals. Additional dust samples from the plant and remote sites are currently being studied.

Jan 1, 1991

By R. G. Hilton

This paper deals with application of Super Detox? stabilization technology to the treatment of electric arc furnace dust (US-EPA listed hazardous waste KO61 ). The process has been used on approximately 170,000 tons of electric arc furnace dust. In addition to the nearly four years of commercial experience at Sterling, Illinois, the process is now being permitted for application at two other locations. The process was originally developed by the Bethlehem Steel Corporation and then further improved by Conversion Systems, Inc. (Bethlehem Steel's Licensee). The treatment process offers many unique bases for its selection, including: A) Low cost compared to the treatment alternatives; B) Lowest available TCLP leachate levels for any process treating K061. Many other processes leave some residue that represents a disposal requirement, although often not addressed; C) Produces minimized final waste disposed, including the fact that the total volume of dust generated and less than the volume occupied by the residue slag from HTMR; and, D) Opportunities for the beneficial utilization of part or all of the waste stream through the development of chemical and physical characteristics. Each of these aspects will be specifically discussed in the paper, including that status of the operations now under permit.

Jan 1, 1994

By H. -P. Behrendt

Muldenhiütten Recycling und Umwelttechnik GmbH is a lead smelter with a very long tradition. The first reference to the existence of smelters on this site is given by a document of inheritance dated 1318. Originally run as a primary lead smelter, which was supplied with ores from the Freiberg mining district and from overseas, it was required to change it over to secondary raw materials due the abandonment of mining in the Freiberg area in 1968. Today, Muldenhüitten Recycling und Umwelttechnik GmbH has two production lines; lead production from secondary lead and waste incineration, which are closely connected and gain advantage from each other. Installations, improved technologies, and the highly skilled personnel have contributed to satisfy all demands for a production concerning quality and environment.

Jan 1, 2000

By Hong N. Vu, Jitka Jandova

"Gypsum and limestone methods were examined in this study to process zinnwaldite wastes originating from dressing Sn-W ores mined in the Czech Republic. These wastes containing 0.20-0.30% Li and 0.10-0.20% Rb were subjected to magnetic separation to obtain a zinnwaldite concentrate with 1.36% Li and 0.94% Rb. It was observed that processing of the zinnwaldite concentrate with gypsum resulted in almost 96% recovery of Li into aqueous liquors, whilst rubidium extraction was only 25%. At the same time, it is possible to extract almost 92% Li and Rb from the identical zinnwaldite concentrate if the concentrate is processed by limestone method. Lithium carbonate, a final product of both methods was recovered from the refined sulphate solution using K2CO3 as a precipitation agent and/or from unrefined hydroxide solution using gaseous CO2. In the continuation of this study, rubidium will be separated from carbonate solutions after Li2CO3 precipitation as RbAl(SO4)2, an intermediate for Rb2CO3 production. IntroductionLithium is used as an alloying constituent in lightweight alloys, as a heat transfer medium in nuclear reactors and as a component in primary and secondary batteries. With the development of a new generation of electric vehicles, the lithium demand will dramatically grow. Lithium chemicals find extensive application in many industrial branches such as metallurgical, glass, ceramic and pharmaceutical industries. Rubidium compounds are predominantly used in psychiatry and medicine, in magneto-optic modulators, solid-state lasers, phosphors and components of electrolytes for fuel cells. The four most important lithium minerals are amblygonite, spodumene, petalite, and lepidolite. Spodumene LiAlSi2O6 (6.0-7.5% Li2O) and petalite LiAlSi4O10 (3.5-4.5% Li2O) belong to aluminosilcate minerals. Lepidolite (Li.Al)3(Al.Si)4O10(F.OH)2 (3.30-7.74% Li2O), lithium mica, is the most important representative of the mica minerals, a subgroup of the aluminosilicates. It frequently contains 3–5% Rb2O and eventually caesium. Zinnwaldite, which has the general formula K(Li.Al.Fe)3(Al.Si)4O10(F.OH)2 (2-5% Li2O), is regarded as a variety of lepidolite with a high iron content. Commercial amblygonite is a complex phosphate (Li.Na)Al(F.OH)PO4 (up to 9.88% Li2O), however, its deposits have not been commercially exploited because of their small size. Natural brines with a high lithium chloride content are important in the industrial production of lithium [l]"

Jan 1, 2008