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By S. Yokoya

With increasing requirement of steel productivity and quality in continuous casting in the conventional casting system using an immersion nozzle, it is very difficult to establish a reasonable molten flow pattern. In order to overcome this difficulty, we propose a new method of imparting swirling motion onto the flow in the immersion nozzle and to control the flow pattern in the mold. Following results have been obtained during the studies. For the case of slab continuous casting mold: High amplitudes of oscillation with a period of 10 to 15 seconds are observed in the outlet flow of the immersion nozzle and meniscus flow in the conventional casting system, while these phenomena are remarkably suppressed using swirling motion in the immersion nozzle, which leads to very calm and uniform flow pattern at the outlets of the immersion nozzle, in the mold and on the meniscus in the mold; For the case of billet continuous casting mold: (1) heat and mass transfer near the meniscus can be remarkably activated compared with a conventional straight type immersion nozzle without swirl, and (2) Quite different mold flow patterns are observed between the divergent and straight immersion nozzles. Heat and mass transport in the mold using the divergent nozzle is much more reasonable compared to that of straight nozzle. The findings, mentioned above, are very useful to control the flow pattern in the slab, and billet continuous casters. Such effectiveness of swirling flow in the SEN on the mold flow has been put into practical use. As a result, remarkable progress on the quality and production of continuous casting products has been observed in practical application.

Jan 1, 2006

By Jose Carlos D’Abreu, Edelink Efrain Tinoco Falero, Mauricio Marcos Otaviano, Helio Marques Kohler

Nowadays the most important Direct Reduction - DR processes in shaft furnaces has to deal with carbon fines precipitation and DRI carburization issues. Based in a cooperative research program joining Catholic University (PUC-Rio) and SAMARCO Mining Co, a project dealing with pellets reduction and those two phenomena was established. This work analyzes kinetically the three reactions mentioned before, considering typical values for the operational variables temperature, flowrate, pressure and gas composition, parameters commonly used to control the DRI formation in the Reduction Zone - RZ of the shaft furnaces. From laboratories experimental results, the kinetic equations for those reactions were established and, using the superposition principle, generated a specific global kinetic model for the iron oxide reduction and the soot formation. Finally, using those experimental results and applying a planned statistical factorial analysis for the experiments, the numerical coefficients for each equation were calculated and the correlation factor determined for the proposed global kinetic equation.

Jan 1, 2015

By Jaroslav Horskoý, Miroslav Raudenský, Bogdan Filipic, Božidar Sader

This paper describes main elements and practical use of the computational system for automated setting of optimized casting conditions in the continuous casting of steel. The system consists of the heat transfer model of the process, empirical metallurgical criteria, and optimization algorithm. The physical model of the, strand temperature distribution relies on the classical Bennon-Incropera mixture continuum formulation for the convective-diffusive heat transport. Fluid flow effects are considered through enhanced thermal conductivity of the liquid phase. The model is solved by the operator-splitting Crank-Nicolson finite volume version of the Voller-Swaminathan scheme. The solution procedure is coupled with the IDS solidification analysis package. Boundary conditions for the strand cooling rely on combination of the generic and plant-specific mold, spray, and roll heat transfer coefficients ' by coping the effects of the casting speed, casting temperature, casting powder, mold oscillation mode, steel grade, water or air-mist spray type, running water, trapped water on the rolls, and radiation. The caster safety and productivity and the quality of the strand are related to nine empirical metallurgical criteria. The criteria ensure the caster safety and economy as well limit the internal, longitudinal, and transversal surface cracking possibility. The problem of finding optimum casting parameter values is stated as a minimization problem based on the analytical form of the cooling criteria evaluated from the steady-state temperature distribution of the strand. To solve the optimization problem, a genetic algorithm is employed. The algorithm explores process parameters settings heuristically by applying the principles of biological evolution. It starts with a random set of solutions and iteratively improves them through selection and variation. Solutions are evaluated by running the heat transfer model of the process and extracting the values of the empirical metallurgical criteria.

Jan 1, 2000

By P. M. Tait, N. A. Warner

"The refining of thermally produced zinc is currently performed using a highly energy intensive and arguably outmoded process, distilling zinc under atmospheric pressure at temperatures of 900°C to 1000°C. In order to produce refined zinc more profitably and with less environmental impact a new process has been proposed. This process is generic to all thermal zinc smelters and aims to match the purity of zinc from current technology (99.99%-99.999%). The objective is to perform all separation processes using only the heat contained in the smelter product stream. Vacuum conditions are extensively used lowering operating temperatures and enhancing separations. As part of this process zinc is distilled under vacuum from high concentration obtaining a refined product with respect to lead content. A mathematical model has been developed from fundamental principles to describe this stage, the distillation of zinc across a temperature difference between two circulating zinc streams in open channels under vacuum. Heat for the distillation is supplied by the liquid phase, necessitating a large recycle to maintain high operating temperatures, and keep zinc concentrations high. In determining this model and the operating conditions required, relationships between temperature, pressure and composition are considered.IntroductionCurrent technology (the Refluxer) used to refine thermally produced zinc is both expensive and highly inefficient. At present 80% of the worlds zinc is produced via the electrolytic process reflecting the poorer performance of the thermal route, the zinc-lead blast furnace and Refluxer. A new process is proposed to overcome the drawbacks of current processes. These drawbacks are both economic and environmental. The Refluxer requires 6.6 GJ of energy to refine one tonne of SHG zinc 1, other disadvantages of the Refluxer stem from high operating temperature, around 900°C, and liquid zinc being highly corrosive towards ferrous metals. The Refluxer is constructed from silicon carbide sections which join together by means of flat machined faces making liquid metal leaks inevitable. The Refluxer columns are very sensitive to thermal cycling, thermal shock and mechanical vibration, which easily lead to structural failure. To avoid thermal stress on the columns the feed rate and feed temperature need to be kept constant which means the feed baths to the columns must be able to accept solid and liquid feed as the Refluxer has to operate when the smelter is shut down."

Jan 1, 1998

By V. Gornitz

The Orphan mine uranium deposit, Grand Canyon, Arizona, is a cylindrical collapse-breccia pipe, 70 to 150 m in diameter and 500 m deep. Pipe fill was derived from the Supai Group, Hermit Shale, and the Coconino Sandstone. Uraninite, with Cu, Fe, Pb, Zn and Ni-Co sulfides is concentrated along the pipe boundary ring fracture (annular ring) and within the central porous sandstone matrix. There is some suggestion of vertical and lateral zonation of U with respect to Cu. Reduction of ferric oxide cement from red beds and recrystallization of carbonate, with formation of kaolinite preceded major ore deposition. Early Ni sulfides, arsenides and disseminated pyrite were followed by massive pyrite, and botryoidal uraninite, which in turn was suc-ceeded by Cu, Zn and Pb sulfides. A second, later generation of uraninite was closely intergrown with hematite and base metal sulfides. Oxidation of primary minerals may have been associated with Tertiary regional uplift. The paragenetic sequence closely resembles that of other Grand Canyon breccia pipes, except for the extensive development of the distinctive uraninite-hematite association. Mineral assemblages at the Orphan suggest possible mixing of the metal-bearing solution(s) with a more oxidized fluid, containing soluble uranyl complexes. Homogenization temperatures of fluid inclusions in calcite (GO-lIO?C) at the Orphan fall within the lower end of the range observed at other breccia pipes.

Jan 1, 1987

By B. Mishra

Calcium and lithium gallides have been synthesized by powder metallurgy techniques in the stoichiometries that can be used as reduction alloys for the Rocky Flats Plant Salt-Scrub (SS) process. The SS process is performed to recover valuable metals from salts generated in the electrorefining and the molten salt extraction processes. Combustion synthesis has been optimized for variable heating rates up to the reaction ignition temperature and for green densities of the powder compacts in terms of the ignition temperature and the exothermic heating of the product in an effort to develop LiGa and CaGaz alloys. The problems arising from the melting point and density differences of calcium, lithium and gallium have also been studied. The SS alloy compositions were produced by mixing, pressing and sintering the metal-powders. The efficiency of the intermetallic alloy, Ca-17 wt. pct. Ga, as a reductant and the effect of gallium on salt clean- up has been discussed. Measurement of actinide recovery has been studied with cerium as the surrogate for the actinide metal. The development of an alloy for SS reduces a major contaminated waste disposal problem besides recovering the valuable reactive metal.

Jan 1, 1993

By D. McConchie

Management of caustic red mud wastes at the QAL bauxite refinery uses an innovative approach . involving neutralising the red mud with seawater; solids settle in a Red Mud Dam and residual water (pH = 8.6) is discharged to a tidal inlet. A survey of 18 trace elements in sediment, water, mangroves and molluscs, and an ecological survey of benthic fauna in the inlet, and at near-pristine control sites, revealed no significant trends that were linked to the discharge, except for the concentration of Al which was slightly elevated within 100m of the outfall. Trace element concentrations in water samples were close to, or below, world average seawater values and oysters collected near the outfall were acceptable for human consumption. The impact of discharges is minimised by a high tidal range, >60% flushing of the inlet in each tidal cycle, and the very high trace element binding capacity of sediment in the dam (> 100meq/ 100g dry mud).

Jan 1, 1996

By Norimasa Yamasaki, Masao Kurosaki

"The effects of plating conditions on the crystal orientation of electrodeposited zinc were investigated by varying elecyrolyte flow rate and current density. Precipitation of the Zn (00 • 2) basal plane is promoted at lower current density and higher flow velocity. Effect of the flow velocity on the mass transport was evaluated based on the polarization measurement in which Cu was used as the tracer. As a result, it has been clarified that the crystal orientation of electrodeposited zinc can be uniquely arranged by the overvoltage (iU0.5) that can be simply calculated by considering -the current density and boundary layer thickness. At the same time, the electrode potential during electrodeposition that can be calculated by using a model based on the competitive reactions of hydrogen reduction 'and zinc reduction exhibits an extremely good correlation with the crystal orientation of electrodeposited zinc.Introduction Electrogalvanized steel sheet has better surface properties than hot-dip galvanized steel sheet, and is used in home electric appliance and automobile applications. Factors such as crystal morphology, crystal orientation and surface roughness have a large influence on its appliance, formability and corrosion resistance [1-3].Electrolysis, condition, bath composition and alloying elements are reported as factors that affect the crystal orientation of the electrogalvanized coating. Factors that can be controlled on time in the production site are electrolysis condition that-is current density and plating solution flow velocity.Some studies[4-6] report that the crystal- orientation of the Zn(00 • 2) plane is increased by promoting, the mass transfer of zinc ions in the plating solution or decreasing the concentration overvoltage, but did not investigate in detail the plating solution flow conditions in the plating cell nor quantitatively determine the effects of both current density and plating solution flow conditions on the crystal orientation of ' electrodeposited zinc."

Jan 1, 2000

By Yongfeng Jia

Lime neutralization and co-precipitation of As(V) with iron(III) is the most widely used and most economical method for the removal of arsenic from mineral processing solutions and effluents. However, the arsenate fixation mechanism in the coprecipitated solids is not fully understood. It was suggested by various researchers to be a ferrihydrite precipitation process during which arsenate is removed by adsorption on ferrihydrite. In this study, XRD, EXAFS and microprobe were employed for the speciation of arsenic and the effect of various factors on arsenic solubility was also investigated. The results indicate that coprecipitation is a more complicated process than simple adsorption resulting in lower arsenic solubilities. Poorly crystalline ferric arsenate was observed for the first time to be present in the coprecipitated solids. In case of lime as base, there exists some type of Ca-Fe-arsenate association. A general term ?coprecipitate? is suggested to describe the precipitated arsenic-bearing solids instead of those widely used specific terms ?arsenical ferrihydrite? or ?arsenic-bearing ferrihydrite?.

Jan 1, 2005

By J. R. Goode

There are at least a dozen methods of selectively removing cerium from a mixture of the rare earth elements (REE) including separation techniques based on the oxidation of cerium to the quadrivalent state. Several of the oxidation processes have been operated on a commercial scale, others have been tested and in some cases are part of proposed flowsheets. In this paper, we describe and compare the various methods. We also present preliminary estimates of the costs of early Ce removal and discuss recovery and purity aspects of the options.

By Wilson Pascheto

This paper presents results of investigations performed as part of a Root-Cause-Failure-Analysis (RCFA) of a DC smelting furnace that was brick lined with MgO-based refractories. An unusual continuous contraction of the furnace hearth was identified during operation. Cracks in the refractories were envisaged after a major shutdown of the furnace. To determine the mechanism and causes of the unusual contraction behaviour of the furnace hearth, refractory samples were taken from the furnace at different locations and subjected to different analysis including Scanning Electron Microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDX), QEMSCAN and Electron Probe Micro Analysis (EPMA). Creep testing of refractories under different loads (ASTM C832) was also employed to evaluate the mechanical integrity of the used bricks in comparison with the new ones. Results of the various characterisation analyses revealed that there was an interaction between refractory bricks and molten material during furnace operation, which resulted in reduced creep resistance of the MgO-based refractories. This was verified by comparing creep performance of the used brick samples and new brick samples at different temperatures and applied stresses.

By Pertti Pekkala

Outokumpu has 25 years of experience in the SX area. The development of the solvent extraction plants responds to an ever increasing demand for lower operational costs wd for adaptability to process disturbances with minimized risks. In this paper the features of the VSF ("Vertical Smooth Flow") SX technology are described, such as the separated pumping and mixing, the homogenous gentle mixing, the droplet coalescence and the ultra pure settling. A major advantage of the mixing technology is the high stage efficiency of above 99 per cent. The connection between this and some features of the settler front section is clarified. The present design of VSF plants is based on experience of existing operations at, for example, Zaldivar, Radomiro, Morenci, Kokkola and Harjavalta. These production plants cover a unit capacity range of 60 to 3,600 m3/h expressed as a total flow. It is evident that there are no restrictive factors to increase the total flow up to 5,000-6,000 m3/h by introducing the VSF technology. The copper SX technology has a long history reflecting many individual features of the separate copper SX plants. Still it is necessary to verify all actual running parameters by pilot tests taking into account impurities, chemicals used etc. The design of SX plants is not only about the delivery of equipment but also a process concept, and it is best tailor-made and adapted to specific local requirements.

Jan 1, 1999

By Steven E. Follin

In-situ leaching is commonly used to recover uranium from low-grade deposits in sandstone formations. Acceptable recovery rates can only be obtained if the formation retains its permeability during leaching. Field experiences indicate that microbial growth, stimulated by the leaching pro- cess, can cause plugging problems. To investigate this hypothesis, leach solution and solid samples from well casings and submersible pumps were obtained from four in-situ mining sites. Chemical and microbiological analyses were performed. Bacillus species, Micrococcus species, pseudomonads, and xanthomonads were isolated from these samples. A mixed culture of these organisms was inoculated into a uranium core that was being leached in the laboratory. The permeability of this ore sample decreased to one-third its original value after 16 days. The addition of hydrogen peroxide (0.2 g L-1) to the leach solution killed the microbes and restored the permeability to its original value. This suggests that periodic injection of hydrogen peroxide into production wells may reduce microbial plugging in these wells and the immediate surrounding formation.

Jan 1, 1985

By Philip E. J. Green

Two of the cornerstones of total quality management, the use of statistical and problem solving tools, and the involvement of employees, are directly applicable to environmental protection. The reduction in variation decreases the chances of violations and mishaps. Involving employees in minimizing environmental impacts is critical. One mistake, even with the best technology, and your plant can be shut down, customers lost and fines and penalties imposed - your reputation and the environment damaged. Proven strategies for involving employees in environmental protection, and over-coming the frequently strong differences of opinions about what constitutes environmental protection, will be discussed.

Jan 1, 1992

By Xiaodi Huang, Matthew Andriese, Zheng Zhang, Jiann-Yang Hwang, Zhiwei Peng

"The thermal decomposition and regeneration behaviors of wüstite were investigated by in situ high temperature X-ray diffraction (HT-XRD) under non-isothermal condition at heating rate of 4 K min-1 in vacuum ranging from 294 K to 973 K. Wüstite on heating decomposes to magnetite and iron up to 823 K, above which it exhibits marked tendency to regenerate. Investigation of thermal stability of the reaction system shows that the decomposition proceeds under kinetic reaction control while the regeneration is under thermodynamic control. Kinetics study based on the Coats-Redfern integral approximation method indicates that the decomposition reaction follows a Komatsu-Uemura model-based diffusion-controlled kinetics with activation energy of 32.860 kJ mol-1. The thermodynamics analysis of regeneration reaction demonstrates that wüstite regenerates at lower temperature than stoichiometric ferrous oxide.IntroductionOwing to its importance in preparing various magnetic ceramic/metal nanocompostites or nanocrystals with high values of coercivity for the application as recording media, wüstite (non-stoichiometric ferrous oxide) has been attracting the attention of scientists over a long period [1-6]. The thermal behavior of wüstite was investigated by several researchers and phase transformations due to thermal decomposition and regeneration of wüstite during the heating in a specific temperature range was observed [7-9]. In spite of wüstite being found to dissociate to magnetite and iron at temperatures lower than 848 K and then regenerates at higher temperature, a clear understanding of the reaction mechanisms is clearly lacking [9]."

Jan 1, 2012

By Ikuhiro Sumi

A new steelmaking process, in which manganese ore was intentionally reduced, was developed to achieve a higher manganese Yield using a combined blowing converter. In this study, manganese behavior was discussed through the introduction of a model. Apparent reduction rates of manganese were calculated by the two terms that were determined experimentally, with SOkg and 2S0ton combined blowing converters. The model calculated manganese changes during the operation. We applied the model to the actual operation and found that manganese behavior was predicted fairly well by this model.

Jan 1, 1996

By Howard K. Worner

"In a rewarding career spanning nearly two thirds of a century, the author has worked at the frontier of such diverse fields as the creep of metals, structure properties and production of novel dental and surgical materials, molten salt electrolysis for titanium production, greatly improving the productivity of large iron blast furnaces and of oxygen steelmaking. While each of these has given great satisfaction, special thrills have derived from the development of new methods for the continuous production or refining of both ferrous and non ferrous metals. A rewarding segment was the evolution of various aspects of WORCRA technology. Unfortunately, several of these inventions have been ""ahead of their time"". Introduction""I am greatly honoured by the convening of this meeting to recognise my contributions to pyrometallurgy. My appreciation is the greater because this is the third Howard Worner Symposium; the first took place in the University of Newcastle in 1988, close to my 75th birthday. It was arranged by the local branch of The Australasian Institute of Mining and Metallurgy with the theme, ""Frontiers in Pyrometallurgy"". The second was organised by the University of Wollongong in conjunction with the Australian Academy of Science and the Australian Academy of Technological Sciences and Engineering; it celebrated my 80th birthday and, at my request, covered a broad range of topics under the heading of ""Recent Advances in Science and Technology"". Now, this very international meeting on ""Injection in Pyrometallurgy"" has been convened by the G K Williams Co-operative Research Centre for Extractive Metallurgy in my alma mater. I am both delighted and honoured that the cosponsors are the TMS (USA) and ISIJ (Japan).Dr Madhu Nilmani consulted me about the field to be covered and I readily concurred because ""injection"" has been of keen interest to me since the beginning of the 1960s when I began my pioneering work on sequential oxygen (or air) injection into flowing streams for both refining of blast furnace hot metal to steel and for the continuous smelting-converting of copper and nickel."

Jan 1, 1996

By F. W. Warnaars

Chanarcillo is a historically well-known silver deposit which produced over 100 million ounces. High grade vein-type mineralization is confined to a prominent set of nearly vertical, NNW to NE fractures that intersected limestones, andesites and tuffs of Early Cretaceous age. A significant amount of disseminated silver mineralization extends laterally outward from the fractures for considerable distances in pyritic carbonaceous limestones, whereas more competent volcanic beds rarely contain lateral mineralization. Local exposures of skarns are mostly barren. Silver and minor base metal mineralization was probably formed peripheral to a granodioritic intrusion inferred to exist at shallow depth. Part of this intrusion is exposed nearby where it contains significant hydrothermal mineralization and alteration. This intrusion was dated at 83.8 m.y.

Jan 1, 1987

By Zhang Hengzhong

Based on thermodynamics of surfaces and a proposed two-dimensional state equation for surfaces, the relationship between the surface tension (Y) of a solution and the activity (a1) of its component (i) was derived: (1/Y)r2-.¬E (ai/Yl) The derived equation was verified with reported experimental data of water-alcohol systems and water-acetone system, the calculated results showed astonishing coincidence with experimental. Applications of the equation to the five matte systems Cu2S-FeS, Ni3S2-FeS, FeS-PbS, Cu2S-PbS and FeS-Cu22S-PbS also demonstrated that at given matte compositions the calculated surface tensions agreed with experimental fairy well.

Jan 1, 1993

By Kumar Ganesan

Elevated mercury levels are expected in aged gold mine tailings due to residual mercury from the amalgamation process, The fate of mercury in tailings is not well understood, Its potential health risk depends mainly on the degree to which mercury is mobile in soil. Mercury is re-moved from soil by evaporation, plant uptake, microbial activities, leaching, and other physico-chemical processes. In this research the amount of mercury lost by evaporation was evaluated. Several aged gold mine tailings in Montana were sampled for total mercury and its flux into the atmosphere. Mercury levels in tailings were higher than the general background levels in most sites. The mercury levels in some cases were as high as 10,000 ug/g. The field measurements using flux chambers indicated a wide range of mercury flux from aged gold mine tailings. The mercury flux ranged from 0-11,000 ng/m2/hr. The mercury loss by evaporation helps rid the soil of mercury but the mercury vapor then will participate in the atmospheric mercury cycle, The low solubility of elemental mercury in water helps to minimize mercury leaching from tailings, however, conversion of elemental mercury to more soluble forms by bio-geo-chemical processes can enhance its mobility posing increased health risk.

Jan 1, 2003