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By Line Hallgren

The fluid flow in the mold during up-hill teeming is of great importance for the quality of the cast ingot and therefore the quality of the final steel products. At the early stage of the filling of an up-hill teeming mold, steel enters, with high velocity, through the nozzle into the mold and the turbulence on the meniscus could lead to entrainment of mold flux. The entrained mold flux might subsequently end up as defects in the final product. It is therefore very important to get a mild and stable inlet flow in the entrance region of the mold. It has been acknowledged recently that swirling motion induced using a twist tape swirl blade, in the submerged entry nozzle is remarkably effective to control the fluid flow pattern in both the slab and billet type continuous casting molds, resulting in increased productivity and quality of the produced steel. From the above result, we propose, swirling flow generated through a swirl blade inserted into the entry nozzle, as a new method of reducing the deformation of the rising surface and the unevenness of the flow during filling of the up-hill teeming mold. The swirling blade has two features: (1) to generate a swirling flow in the entrance nozzle and (2) to suppress the uneven flow, generated/developed after flowing through the elbow. The effect of the use of a twist tape swirl blade was studied using both numerical calculations and physical modeling. Water modeling was used to assert the effect of the swirling blade on rectifying of tangential and axial velocities in the filling tube for the up-hill teeming and also to verify the results from the numerical calculations.

Jan 1, 2006

By David K. Melgaard

Electroslag Remelting (ESR) is a complex process used to produce high quality specialty alloy materials. The quality can be directly correlated to variances in melt rate and immersion depth. Conventional ESR furnaces control these quantities using two independent control loops using proportional changes in current for melt rate and driving the electrode up and down to match a voltage set point for immersion depth. However it is well known that the control loops are highly coupled, i.e. changing the current to account for melt rate deviations changes the voltage depth relationship and vice verse. In addition the noise in measurements of the ESR process can be considerable, forcing conventional controllers to use highly damped responses. A new model-based controller has been developed to embody the coupling and improve responsiveness by using estimates from a reduced-order linear ESR model and the typical process measurements to control melt rate and immersion depth simultaneously. Kalman filtering is used to optimally combine the model estimates of eight process states and the measurements of voltage, current, position and mass to estimate the instantaneous melt rate and immersion depth. Several ESR melts under steady state and transient conditions were conducted to evaluate the performance of the new controller. This paper will discuss the design of the new ESR model and controller and will present experimental results demonstrating its much improved control and responsiveness. While this controller was developed for the ESR process, the effectiveness of model-based control in managing such a complex process with relatively simple equations suggests the approach could be employed for many other processes as well.

Jan 1, 2006

By A. Raraz

The optimization of the plutonium electrorefining process has been studied on the basis of modeling and model materials. The plutonium electrorefining process has been reviewed and the basics of the electrorefining process with molten salts as electrolytes and under forced convection has been presented. The definition of the problem in plutonium electrorefining has been related to three factors and this research has addressed these three factors to provide an insight to this process. The hydrodynamic factor gives information on the behavior of the mechanically stirred system. The chemical stability and solidification factor shows the interactions among the components of the electrorefining cell. The electrochemical factor is oriented to study the efficiency of the electrorefining process on the basis of limiting current density, stirring rate and configuration cell. As a result of this study the optimization of plutonium electrorefining implies mainly a re-design of the cell.

Jan 1, 1995

By Alhondra de los Santos, Jesús L. Valenzuela, Jose R. Parga

"The present study evaluated the feasibility of using iron species generated by electrocoagulation (EC) as an adsorbent for removal As(III/As(V) from aqueous media. The full potential of EC was evident in that more than 99 percent of arsenic was removed without addition of chemical reagents. The adsorbent iron-species generated by EC was characterized by Chemical Analyses, X-Ray Diffraction and Scanning Electron Microscopy. The experimental data were correlated by employing a Langmuir adsorption isotherm. Thermodynamic parameters such as ?H o , ?S o and ?Go were calculated. The adsorption process was found to be exothermic and spontaneous.1. IntroductionArsenic contamination in potable water supplies is a serious health problem in many countries around the world. Groundwater arsenic contamination in La Comarca Lagunera Mexico was first reported 30 years ago [1]. Arsenic concentration has been found in well water from several communities ranging from 0.25 to 1.0 ppm. The elevated concentration of arsenic in water, above that originating from natural sources, has been attributed to the use of organoarsenical pesticides in the cotton fields and also to the millions of tons of waste slag generated at a local lead smelter [1]. The main arsenic species present in natural waters are arsenate ions 3- 4 AsO (oxidation state V) and arsenic ions H3AsO3, - 2 3 H AsO and 2- 3 HAsO oxidation state III). However, As(V) ions are most prevalent in oxygenated water while As(III) is found for anaerobic conditions, such as in well water or in groundwater. Conventional methods of arsenic removal rely on chemical-based treatment with lime, alum coagulation, iron coagulation and chemical oxidation. Other processes used with varying degrees of success include adsorption onto activated carbon, reverse osmosis, nanofiltration, manganese dioxide, magnetite and ionexchange resins [1-3]. These conventional processes generate a considerable quantity of secondary hazardous waste such as solid sludge, which also pose serious environmental problems. These drawbacks have forced various industries to search for effective, alternative treatment technologies for arsenic with a preference for electrochemical methods."

Jan 1, 2008

By Christine P. Viecelli

As Phelps Dodge Corporation addresses the environmental challenges of the 1990's, water management has become a key element in an overall waste minimization strategy. The Phelps Dodge Hidalgo copper smelter has implemented a comprehensive water management program that includes management of both fresh and process water utilized by its pyrometallurgical operation. Two major technological strategies are being implemented. They are the design, construction and operation of a raw water pre-treatment facility to allow increased evaporation within cooling towers thereby minimizing blow down, and the use of a brine concentrator to treat and recycle significant quantities of process water. The end result of this program is a significant reduction in raw water pumped from the underlying aquifer into the facility as well as a decrease in process water which must be impounded or otherwise treated.

Jan 1, 1992

By N. Verbaan, E. Bourricaudy, M. Dry

"Starfield Resources is developing a novel circuit for the recovery of nickel, copper, cobalt, iron oxide, sulphuric acid and precious metals from the Ferguson Lake deposit in Nunavut, Canada. In this deposit, pentlandite is too finely disseminated in pyrrhotite for the production of a smelter-grade nickel concentrate at an acceptable nickel recovery, so established technology is not applicable and a novel chloride-based circuit is under development. The enabling aspect of this circuit is the hydrolysis of ferric chloride to hematite, releasing gaseous hydrochloric acid that is recycled. Conventional steps are used for separating and recovering the valuable metals from the chloride solution generated. This paper briefly outlines the circuit and presents the results of experimental work on the enabling steps, viz. the oxidation and hydrolysis of iron chloride to hematite and gaseous hydrochloric acid.IntroductionThe Ferguson Lake bulk sulphide ore body in Nunavut, Canada, owned by Starfield Resources Inc., contains significant amounts of base and precious metals but its mineralogy is such that it is not amenable to conventional processing. Pentlandite, for example, is too finely disseminated in pyrhhotite for even modem techniques such as fine grinding and improved flotation reagents to be effective [ 1] and extracting the value requires processing the entire bulk sulphide, including the pyrrhotite. To give the project a total green footprint, in terms of both carbon emissions and acid rock drainage, Starfield imposed the following requirements:• No reactive tailings to generate acid rock drainage.• No gaseous emissions other than normal atmospheric constituents.• No liquid effluents.• No regular consumption of fossil fuel.• High recoveries of all the valuable metals."

Jan 1, 2011

By D. W. Collins

Several organic and inorganic substances are widely used to control deposit structure and morphology during the electroprocessing of copper. Methods for monitoring the levels of thiourea, glue and guar gum during electrorefining and electrowinning have been successfully developed under the trade names of Reatrol and CollaMat. Other instrumental methods have been developed for additives and decomposition products associated with the electroplating of copper and other metals. Generally, these methods have been found to be either insufficiently sensitive or lacking in the desired selectivity for some or all of the additives. These procedures have mostly employed DC techniques; i.e., cyclic voltammetry, Tafel analysis, etc. In this work, chronopotentiometry (CP) and AC voltammetry were used to examine the interaction of glue, guar gum, thiourea and chloride during the electroplating of copper onto a platinum electrode. In addition, the interactions between the additives have been explored. It was found that glue in pure electrolyte (H2S04 and CuS04 only) had no effect on the chronopotentiogram. Glue was only active if chloride ions were present. The addition of thiourea resulted in several different chronopotentiograms depending on the presence of either chloride or chloride and glue. Thiourea used in conjunction with glue and chloride showed a significant increase in the polarization during copper deposition when compared to the electrolyte containing only glue and chloride. The use of a modified channel electrode further increased the sensitivity of CP. The use of AC voltammetry was explored as a technique to monitor some of the additives. AC voltammograms have more spectral detail then their DC counterparts and it is possible to monitor some of the additives at very low concentrations with AC techniques.

Jan 1, 1999

By N. E. Ablesimov

Electron probe X-ray microanalyser of a coating deposited with "Elitron¬22A" electrospark alloying (ESA) set (anode - Cr, base-catode - chrome vanadium steel) has shown that the zone of phase forming can be divided into three parts: the coating itself, diffusion zone and a thermal affection zone in the base material. Waves of iron and chrome concentrations have been found in the diffusion zone. The authors interprete them as a phenomenon of substance self-organizing in the 30 pill deep diffusion zone, characterized by a change of compositions during the transfer of material from the coating to the base: coating - 20 µm (FeCr2), diffusion zone - 30 µm (Fe3Cr, FeCr, Fe4Cr, Fe2Cr), base - steel (Fe - 87 %, Cr - 12 %, V - I %). This ESA phenomen has been noted for the first time. It may be relative to the phenomenon of periodic formation of secondary products during the mutual diffusion of reacting substances in the case of a one-way reaction. Similar regular structures may appear in the diffusion zone during ESA of vanadium steels with vanadium, manganese steels with manganese and so on.

Jan 1, 1999

By Abhishek Lahiri

Titanium dioxide is extracted from titaniferous ores by chloride and sulfate processes. These two processes produce wastes in the forms of iron chloride, iron sulfate and rare earth oxides gangue, each of which has to go through a further treatment before it can be disposed safely, which may be expensive. The shortage of high-grade ores is also making the two conventional processes less efficient. In view of the above mentioned problems, an alternate beneficiation process of roasting titaniferous ores with soda ash is discussed. The advantage of this process is that, there is no production of wastes. The impurities present in the ore can be selectively separated after the roasting process. The roasting of titaniferous ores with soda ash was carried out between temperatures of 873K and1173K for several hours. The roasting process resulted in the formation of complex alkali compounds and various sodium titanate compounds, depending on the Na2CO3to ore ratio. The phases formed after roasting were characterized using the X-ray powder diffraction (XRD), X-ray florescence (XRF) and scanning electron microscopy (SEM) techniques. The phase equilibria in the Na-Ti-O system are evaluated and compared with the phases obtained after the roasting process. The effects of temperature and the proportion of sodium carbonate on titaniferous ores are also discussed. From the experimental data, the overall reaction kinetics and phases formed were analyzed to ascertain the mechanism of overall reaction and the rate-limiting steps.

Jan 1, 2006

By Pekka Taskinen, Hannu Johto

"Copper sulfide concentrates often contain impurities such as lead and iron. The phase stabilities of the sulfide impurity systems in metallurgical process conditions are in many cases unsatisfactorily known. Thermodynamic information of a system gives better understanding of its behavior of metal making processes, but also has effects on the economic and environmental factors of the production process. In this study, isothermal equilibrium and quenching experiments of the stable phases of the system Cu2S-FeS-PbS at 700 and 900 °C were carried out and based on the experimental results, Gibbs triangle of equilibrium phases of the system was outlined.IntroductionThe knowledge of stabilities of phases and the thermodynamic properties of many sulfide systems in the temperature range of 500-1200 °C are quite limited. Especially, the knowledge of liquidus surfaces of multicomponent sulfide systems is essential for making many metallurgical processes more environmental friendly and allowing the utilization of complex concentrates. In this work, the aim was to investigate the phase stabilities of the quasiternary system CU2SFeS- PbS using evacuated silica ampoules. Of greatest interest were the properties of the liquidus surface in the system, in order to be able to predict better the formation of a liquid phase in metallurgical processes."

Jan 1, 2012

By Lennart Hedlund

There is today a long and well-documented experience of the use of Boliden "Kaldo' technology for treatment of various feed matedals. The process is In commercial' operation in the Boliden Mineral's Rönnskär plant In Sweden for treatment of copper scraps and lead concentrates (In campaigns). This plant was built In 1976 for treatment of lead dusts from the copper plant but later modified to take other raw materials. Boliden's Kaldo techr:lology Is also In operation since 1991 for treatment of low-grade copper scraps In Enlrlsorse's plant In Porto Marghera (Venice), Italy. The plant is producing 25 000 tons of blister copper ,per year. The Kaldo furnace Isa high :Intensity smelting unit, where several successive treatment steps can be done In the same vessel. The furnace can be totally enclosed to protect the working environment, and the small off-gas volume can easily be dedusted. Input materials can vary over a very wide range, the products will be a dump slag with low (0,5%) copper and lead contents and black copper or blister copper. The dust from the process can be used for zinc production. A new development is autogenous smelting of scrap in a Pierce-Smith converter, implemented at Compagnie Générale d' Èlectrolyse du Palais in France.

Jan 1, 1995

By H. Dijkman

The PAQUES Bio Systems' core technology, marketed under the name THIOPAQ®, consists of various high-rate biological processes for metal-sulfur-water systems, complemented with common solid/liquid and gas separation steps. Sulfur species are converted to sulfide, which is a valuable component as it can be used for metals reduction and precipitation. Selective recovery of valuable metals can be employed, leading to revenue from metal values. In this paper, biotechnological systems for the treatment of metal sulfate solutions and dilute SO, gases are described. These installations can be designed to either produce predominantly aqueous (NaHS) or gaseous (H2S) sulfide. The emphasis here is on hydrogen sulfide gas. The main case history discussed is the demonstration plant that ran on hydrogen gas at Kennecott Utah Copper. Three years of operating experience clearly show that sulfate reduction with hydrogen gas is a viable option. Furthermore, the selective recovery of copper from leach water with the hydrogen sulfide produced was shown to be very effective.

Jan 1, 1999

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 K. S. Kumar

FLS miljø, Inc. markets, designs and supplies particulate collection devices for dusts, fumes, and mists; In this paper, the application of both wet and dry electrostatic precipitators (ESPs) in smelting, and roasting plants is discussed.

Jan 1, 1998

By Peter Kettle

This paper describes the performance of the copper industry over a period of some two decades and examines the theme that improvements in operating efficiency have not been matched by improved returns on capital. The financial performance of the copper industry is analysed using CRU's MICA database. Regression analysis indicates a two percentage point increase in operating margins but no increase in returns on capital. The gain in operating efficiency appears to have been mainly achieved in the mid 1980s. The investment boom of recent years has resulted in a rapid increase in the industry's level of debt and gearing ratio (now some 47%). Data on 44 copper mine projects is used to show the linear relationship between scale and capital costs. Typically new capacity costs some US$5,000 /tpy. The relationship between cash costs and capital intensity of projects is also plotted. The greater attention now being focused on efficient use of capital means that capital intensity rankings will become increasingly important in determining which projects go ahead.

Jan 1, 1999

By Tomoji Kawai

"The Pulsed Laser Deposition method using multi-targets is extremely useful for the creation of functional multi-layers and variety of artificial lattices. The topic of the present talk is on the creation of ''Function hannonized artificial lattices by laser ablation"" made of the combined magnetic, ferroelectiric and superconducting layers. The outline of talk is,1. Features of Pulsed Laser Deposition method (Laser Molecular RHEED and S1M/AFM.2. Creation of magnetic, dielectric and superconducting artificial lattices by Pulsed Laser Deposition.3. Novel properties of function harmonized artificial lattices: especially on the magnetic and magnetoresistive artificial The outline of talk is, lattices made of3d transition metal oxides."

Jan 1, 2000

By Juan B. Cabezas

"The favorable characteristics and workability of plastics as a replacement of wood, lead, stainless steel, asphalt and other materials are described. Various types of plastic have proven to be the most favorable choice for handling a variety of acidic, alkaline and organic solutions, as well as pulps, chemical wastes, slurries or tailings for impoundments. The material origin of various plastics, methods of manufacturing and specifications applied to leaching solutions are discussed, including availability and costs. Examples of select plastics are considered for use as alternatives of other materials under severe environmental requirements.IntroductionHydrometallurgical processes applied to gold recovery, as well as other metals, require the use of strong solutions of alkaline, acidic or organic nature, and may also include a variety of materials with extraneous characteristics and complications for handling in storage.The technology of leaching has been in use for more than 100 years, but the applications of leaching processes in metallurgy have become more commonly used in the last 15 years. Suitable materials for the construction of containers, launders, piping, and various accessories, to be used in the handling of leach solutions or slurries, have become a serious problem. Various metals such as brass, lead, stainless steel, etc., and non metallics including wood, clays, glass, rubber, ooncrete, tars or miscellaneous compounds have been tried in the past with serious limitations in workability and resistance to wear and corrosion. For example, the use of metallic, wooden or glass piping systems would require extraordinary shop maintenance to keep such systems in operation"

Jan 1, 1997

By Pranav Deshpande

The wear behavior of metal matrix composites differs from that of the monolithic metallic counterparts because composite materials have multiple constituents in their structures and these constituents wear at different rates. It was observed that under low wear stresses, abrasive wear prevailed. As the wear stress increases, pullout of reinforcement occurs and both abrasive wear and wear due to pullout contribute to the overall composite wear. A model of wear taking into account both types of wear has been developed. A critical pullout wear stress was suggested for each composite. Below the critical wear stress, no pullout of reinforcement occurs. It turns out that the critical wear stress simply equals to the ratio of the interfacial strength between the matrix and the reinforcement to the friction coefficient between the reinforcement and the wear counter surface. The critical wear stress is independent of the particle size of the reinforcement. From data on wear of 53% WC composites, the equation of wear for 32% WC composites was obtained. Experimental results agreed well with the predicted wear rate of this composites. This provides an excellent verification of the wear model developed by Lin and Deshpande. Wear data from Modi et al. in the literature were also perfectly fitted with the model.

Jan 1, 2006

By Suman Das, Justin J. Gambone, Rohan Bansal, Ranadip Acharya

"This paper focuses on modeling of the scanning laser epitaxy (SLE) process that is currently being investigated and developed at the Georgia Institute of Technology. SLE is a laser-based manufacturing process for the creation of equiaxed, directionally solidified and single-crystal deposits of nickel superalloys onto superalloy substrates through melting and resolidifícation of alloy powders using a scanning laser beam. The thermal modeling of the system, done in a commercial CFD software package, simulates a heat source moving over a powder bed and dynamically adjusts the property values for consolidating CMSX-4 nickel superalloy powder. The associated melting and re-solidification process is modeled using an immediate consolidation approach, and the predicted melt depth is compared with the experimental data obtained. For a given position of the beam, geometrical parameters of the melt pool are used to estimate the resulting microstructure. The influence of the processing parameters on the microstructural evolution is also discussed. This work is sponsored by the Office of Naval Research through grants N00173-07-1-G031, N00014-10-1-0526 and N00014-11-1-0670.IntroductionIn order to increase the operating temperature of gas turbine aero engines, investment cast equiaxed turbine airfoils are now often replaced with airfoils that have either directionally solidified columnar or single crystal (SX) microstructure. Wear and damage during operation limits the lifetime of these components and necessitates the replacement of numerous airfoils within the engines. Due to the high cost of producing SX cast turbine blades, the cost of replacing each blade can be several hundred to several thousand dollars. With each engine containing several hundred blades, the cost to replace all blades can reach hundreds of thousands of dollars. Hence, it is of great interest to develop a process that can restore the single crystal microstructure at the locations of material loss and allow for the blades to be repaired and reused rather than be scrapped and replaced."

Jan 1, 2012

By Yunhua Gan, Xiaowen Chen, Yang Tong

Experimental studies of electro-spraying were carried out using ethanol as fuel in a microcombustor under combined electric field. And the effects of different electro-spraying modes on the combustion efficiency were analyzed. Results showed that when ring electrode potential was invariant, there were four different electro-spraying modes with the variations of nozzle potentials, which were varying with the flow of ethanol. The cone-jet mode was the stablest one during the whole experimental process. The atomized ethanol was ignited and combusted stably near the steel mesh, the combustion efficiency increased firstly and then decreased along with the increasing of the equivalent ratios, reached the maximum values when the equivalent ratio equal to 1.0. And the maximum values were the highest at the cone-jet mode, and the lowest at the pulsed-jet mode.

Jan 1, 2016