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By Carlos Eduardo Gomes de Souza, Luis G. S. Sobral, Paulo A. Medeiros da Silva, Selma G. F. Leite, Renata de B. Lima

"The use of mixed cultures of acidophilus microorganisms that act in different temperature ranges, aims at speeding up the digestion of chalcopyrite, highly refractory sulphide mineral, the major mineral in the flotation concentrate of Caraíba Mining Co., with an attractive processing cost. The concentrate under consideration contains mainly chalcopyrite (CuFeS2) and bornite (Cu5FeS4) with contents of, approximately, 70 and 30%, respectively. It was observed in this study, the performance of consortium of mesophiles, moderate and extreme thermophile microorganisms, in the oxidation of the aforementioned sulphides minerals, evaluating operational parameters such as pH of the leaching solution, the reaction temperature and redox potential, with consequent extraction of 80% of the concentrate copper content within 60 days of bioleaching. Such high copper extraction was achieved in column bioleaching tests.INTRODUCTIONThe solubilization of metals by the application of microorganisms from the mineral ores and the subsequent recovery of metals from solution are referred to as bioleaching (Rohwerder, T et al, 2003). This is an economical method for the recovery of metals from minerals; especially lowgrade ores, overburden, and waste from current mining operations which requires moderate capital investment with operating cost (Watling, 2006).Furthermore, bioleaching is generally more environmentally friendly than conventional metal recovery processes such as concentration and smelting. Those physicochemical metal extraction processes generate sulphur dioxide, a toxic emission that is increasingly the target of regulatory legislation (Stott et al., 2000; Olson et al., 2003). Bioleaching of chalcopyrite is the key industry target. The main problem hindering commercial application of chalcopyrite bioleaching is the slow dissolution rate (Fu et al, 2008).Dissolution of acid-soluble sulphide minerals such as sphalerite, and to a lesser extent chalcopyrite, occurs by a combination of ferric iron and proton attack via the polysulphide pathway (Rohwerder et al., 2003)."

Jan 1, 2008

By Di Yang

The influence of high density (104 -105 A/cm2) electric current pulses (70 us duration) and continuous DC (~103 A/cm2) on the flow stress and ductility in tension of a high carbon steel wire were determined at 204°, 427° and 649°C. Electropulsing (100 pulses per second) with an effective current density of 100-200 A/cm2 gave a 10% enhancement in the uniform elongation of the wire at 204°C, but had no effect at 427°C and 649°C. In contrast, continuous DC either had no significant effect on the ductility or gave a decrease. The electropulsing per se decreased the flow stress only slightly at 204° and 427°C, but gave a significant decrease at 649°C. Continuous DC increased the flow stress at all three temperatures. The present results along with those by others suggest that the enhanced ductility by electropulsing and the reduction in flow stress may be further increased by raising the effective current density through increases in either the pulsing frequency, maximum current density of each pulse or pulse duration. This could conceivably increase the reduction per pass during wire drawing or the number of passes between anneals.

Jan 1, 2001

TiO2 and Ti/TiO2 thin films were deposited on a quartz substrate by laser ablation of Ti02 and Ti targets using Nd:YAG pulsed laser. After sulfurization of the Ti02 film in H2S or CS2 gas at 1273 K for 1 hour, the surface atomic structure was changed. Furthermore, the Ti/TiO2 film was successfully prepared by the subsequent ablation of Ti and TiO2 targets. The morphology and structure of the films were characterized by XRD, XPS and AFM analyses.

Jan 1, 2003

By Susanne Pignolet-Brandom

Reflected light microscopy scanning electron microscope energy dispersive spectroscopic analysis and backscatter electron image and electron microprobe chemical analysis have been used to study lead sinter and lead blast furnace slag. These studies provide invaluable information on the phases present their intergrowths, and their chemical composition. Such information increases the understanding of the nature of pyrometallurgical processes and the behavior of minor elements during these metallurgical processes.

Jan 1, 1987

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 F. Mucciardi

While flash smelting and converting are capturing a greater share of the market, injection through circular injectors will remain with us for the foreseeable future. The use of top lances for injection is a key feature in several processes (e.g. Mitsubishi, Ausmelt). Tuyeres, on the other hand, are incorporated into a number of processes (e.g. Noranda, Peirce-Smith). To date no lances or tuyeres are cooled by an external source. The reagent provides the bulk of the cooling. With limited cooling, it is normal to have substantial wear on the nozzles - especially in the case of lances. To overcome the issue of wear, a new patented injector (lance or tuyere) has been developed by Noranda and McGill University. This novel unit is based on heat pipe technology. It can operate for an extended period of time without wearing. Enhanced lance/tuyere life is achieved by operating the injector at a low enough temperature that promotes the formation of a thin frozen layer on the outer body of the unit. The vaporizing and condensing substance within the unit acts to cool' the high heat flux portions and dissipate the heat to areas of low heat flux outside the vessel. A fairly large number of tests have been conducted with a prototype unit. The tests have shown that the heat pipe lance is a viable unit. In this paper is detailed a test which illustrates how the lance functions when pure oxygen is injected into copper matte. In addition, the findings from a basic study of a heat pipe in high heat flux environments are also presented.

Jan 1, 1999

By T. Asahina, M. Nakamura, M. Mabuchi, I. Shigematsu, M. Nakanishi, G. Yamauchi

"Commercial stainless steels (SUS304L and SUS430) were subjected to equal channel angular extrusion (ECAE) at room temperature to a total strain of 2.3 to 9.2. For each type of stainless steel, it was shown that the sample processed by ECAE showed higher room temperature strength than the as-quenched sample. This is probably due to the heavily worked structure. On the other hand, both strength and elongation of the ECAE processed SUS430 were increased by annealing at 773K. It is likely that higher strength is attributed to both the heavily worked structure and fine substructures. It is also likely that higher elongation is attributed to the fine substructures. It is concluded that ECAE is available for improving the room temperature strength of commercial stainless steels.INTRODUCTIONEqual channel angular extrusion ( ECAE ) is a technique that provides the repetitive deformation and allows to high intensity of deformation. With this procedure, a sample is pressed through a channel that has an equal cross section but bent at an angle of ?> [1-2]. Shear strain is introduced when a sample passes through the bending point of the channel. Repetitive processing is feasible because the cross-sectional dimension of a sample has no change during processing. To date, many reports have described that ECAE is available for the fabrication of fine-grained materials [3-14]. On the other hand, an ECAE processed sample can achieve high intensity of deformation through repetitive deformation. According to the equation given by Segal [ 2 ], a strain of about 1 is introduced in each pass through die if the angle ? is 90 deg.It is well known that high tensile strength can be achieved in metallic materials through work hardening [15]. It is also known that metallic materials with fine grain size show high strength [16]. Hence, it is expected that ECAE is available for strengthening method in metallic materials. In the present paper, we will report the mechanical properties of stainless steels processed by ECAE. As samples, SUS304L austenite stainless steel and SUS430 ferritic stainless steel were chosen. Each alloy has a single-phase structure (fee or bee) and shows no phase transformation, so that transformation strengthening cannot be applied. Hence, a heavy cold work such as ECAE may be effective for strengthening of this stainless steel. Annealing was conducted for the ECAE processed SUS430 to vary its microstructure. Then, the effect of annealing on the strength of the ECAE processed SUS430 was also investigated."

Jan 1, 2000

By I. Ohnaka

Although many works have been reported on the semisolid casting, the mold filling behavior of semi-solid alloys has not been so well understood. This paper compares the physical and numerical simulation results on the mold filling behavior. Physical simulation was performed by using solid-water mixture. The numerical simulation was made under the assumption of one phase flow with an effective viscosity. It was found that the solid particles stabilize the flow greatly if the kaction solid exceeds about 0.4, because viscosity increases greatly. The overall flow behavior can be estimated by the numerical simulation. Interesting flow behavior was also found which can not be observed in the case of one phase flow and which is difficult to simulate by the one phase flow assumption.

Jan 1, 1997

By Takahiko Okura

Sulphur, with its multiple oxidation states, play critical roles in many processes, ranging from regulating enzymes in plants, to acidifying aquatic systems, and to affecting the global climate. Most of non-ferrous smelters have been contributing to reduce atmospheric emissions of sulfur dioxide to acceptable levels, converting it to sulphuric acid and/or gypsum. However, some amount of SO2 gas is still emitted from isolated smelters. Furthermore, sulphuric acid is competing with involuntary elemental sulphur in the market. This situation puts the non-ferrous metallurgical industries to develop a new sulphur fixation process. This paper briefly describes the new technologies for fixation, followed by the novel proposal to convert SO2 gas to elemental sulphur using organic materials. Finally, the feasibility will be presented technologically and economically.

Jan 1, 2006

By Kenji Morinaga, Shigeru Fujino

"Preparation and vacuum ultraviolet (VUV) transmission spectra of aluminum fluoroberyllate glasses, MgF2-CaF2-SrF2-A1Fr BeF2 (MCSA-Be) and MgF2-CaF2-SrF2-AlFrYFrBeF2 (MCSAY-Be), were studied. The influence of YF3 and BeF2 on the thermal stabilization against crystallization and VUV transmittance was investigated. With increasing the BeF2 content, the crystallization tendency decreased and the absorption edge shifted to shorter wavelength in the MCSA-Be and MCSAY-Be glasses. The MCSA-20Be glass composition exhibited the shortest wavelength UV absorption edge (-147 nm) and the highest transmittance at 157 nm (60% for 2 mm sample thickness). The transmission values at 157 nm and the slope (steepness) of the absorption edge were found to be significantly influenced by the trace amount of Fe2+ derived from the BeF2 raw materials.IntroductionPure beryllium fluoride is known to be an only fluoride that forms one component glass on cooling from the molten state and is structurally similar to silica with [SiO4]4- tetrahedra. Molten BeF2 is highly viscous with a viscosity of about 106 poise near its liquidus temperature at 550""C[l]. The addition of modifying fluorides such as LiF, NaF or KF to BeF2 substantially decreases the viscosity[2]. Glass forming region of binary fluoroberyllate glasses has been mainly reported by several authors [3]. LiFBeF2 binary system is structually analogy for Mg0-Si02 system from their phase diagram and ratio of ionic radius for each cation and anion, respectively. LiF-BeF2 binary glasses seems to be promising candidates for the extreme deep vacuum ultraviolet (VUV) transmitting optical materials owing to their larger band gap. However, it is chemically unstable, and so, have no practical application for lens systems in micro lithography equipments and substrate materials for F2 (157nm) excimer laser[4]. There are also few reports on the VUV transparency of multicomponent aluminium fluoroberyllate glasses from the view point of their compositional dependencies. The purpose of this paper is to prepare deep VUV transmitting optical materials and determine the optimum glass compositions for aluminium fluoroberyllate glasses investigating their thermal stabilization against crystallization."

Jan 1, 2000

By Chikabumi Yamauchi, Masami Tashiro, Toshiharu Fujisawa, Hiroyuki Snano

"Rare earth metals usually contain large amount of oxygen because of their reactiveness, and therefore oxygen removal is one of the major problems on the purification of rare earth metals. In the present research work, halide flux treatment at high temperature under inert gas atmosphere was applied to the oxygen removal from neodymium. NdF3 was used as a halide flux. Deoxidation reaction and its mechanism were discussed based on the experimental results. Halide flux treatment is very effective for oxygen removal from rare earth metals.IntroductionSolid Sate Electrotransport (SSE) process has been successfully applied for the elimination of interstitial gaseous impurities from chemically active metals[l]-[5]. However, to achieve a higher effectiveness of the SSE process, it is required a very low initial impurity content in the metal. In case of rare earth metals, it is known that they usually contain large amount of oxygen that should be lowered as much as possible before applying the SSE process. In addition, if effective oxygen removal is achieved by simple process, it is significant also from the industrial viewpoint. In the present work, the application of a halide flux treatment is investigated to remove oxygen from neodymium by using NdF3 as a flux. At first, deoxidation reaction and its mechanism were discussed based on the phase diagram of the Nd-NdF3-Ndp3 quasi-ternary system. Based on the results, oxygen content in deoxidized neodymium was calculated theoretically and it was verified by deoxidation experiments."

Jan 1, 1998

By Patrick R. Taylor

Iron phosphate glasses are promising host matrices for vitrifying actinide rich nuclear wastes materials because of their high solubility of actinide oxides, high chemical durability, and relatively low melting temperatures. An iron phosphate waste form was developed at the University of Missouri-Rolla. The structure and property of the waste form were well characterized by materials techniques. However, to scale the process and advance it to commercial viability, it is necessary to understand the processing parameters, such as the partitioning of waste elements and the viscosity as a function of temperature. Viscosity of 40 Fe203 - 60 P205 mole % iron phosphate melts (prepared with phosphorous pentoxide and ferric oxide) at 1000-1200 C was measured by the rotating-spindle method. It was discovered that this fluid has non-Newtonian behavior. Experiments were performed to study flow properties following the Standard Test methods for Rheological Properties of Non-Newtonian Materials by Rotational (Brookfield) Viscometer (ASTM D 2196-86). Samples prepared using ammonium phosphate and ferric oxide showed Newtonian behavior and the temperature dependence of the viscosity was studied over the range of 1000 to 1200 degrees C. The difference in flow behavior between the two fluids was analyzed in terms of preparation conditions and variation in the final composition and phases. The partitioning behavior of waste elements in the iron phosphate glass was studied by melting in a high temperature furnace and JCP analysis. The experimental results show that the solubility of Ce and Sr in phosphate glasses is significantly higher than the solubility associated with borosilicate glasses. This strengthens the conclusion that iron phosphate may be a viable alternative to borosilicate glass for immobilization of high heavy-metal-content wastes and actinide rich wastes.

Jan 1, 2002

By Jonathan M. Berkoe

Design engineers and metallurgists have long recognized the need for better methods to calculate a wide range of fluid dynamic effects in smelters and hydro- metallurgical facilities. Examples can range from the capture of fume in the secondary hoods of a copper converter, to controlling the thermal effects of heat transfer resulting from metal and slag flows within a furnace. With the advent of relatively low-cost, high- speed computers and user-friendly, commercially available computerized fluid dynamic (CFD) programs, these calculations can now be made. Use of CFD increased the understanding of both hot gas and molten flows in smelter facilities and has already led to design improvements in converter fume control hoods as well as improved management of heat transfer in electric furnaces. This paper will present two representative CFD applications to metals industry facilities. To date, Bechtel has implemented CFD results on four continents.

Jan 1, 1999

By Valentine A. Chanturiya

A model for development of electric discharges between particles of sulfide minerals (pyrite) under the action of high-voltage nanosecond pulses is proposed. It is shown that through discharges in a layer of pyrite particles lead to energy concentration in small contact regions between particles; the concentrated energy is sufficiently high for local disintegration of mineral complexes.

Jan 1, 2009

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

Rotary kiln incinerators are widely used in the incineration of various types of hazardous wastes. However, the complex transport processes within the incinerator are not well understood. Due to large variations in waste types and difficulties in feed characterization, the incineration process meets great challenges in a smooth operation, and expects uncertainties in the process chemistry and emission control. In order to get better understanding of the incineration process, process simulation was made on the kiln behavior by using Computational Fluid-dynamics (CFD) to characterize gas flow, temperature distribution and waste combustion in the incinerator. Temperature measurement was conducted in an operating incinerator to validate the CFD model. This paper addresses the environmental issues related to the hazardous incineration process, and reports the recent simulation results on gas flow and mixing, combustion heat transfer, and potentials to reduce emissions.

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 Hwa-Soo Park, J. K. Yoon, Hoseok Nam

In a thin slab casting process, control of fluid flow in mold is particularly difficult due to the high casting speed and large aspect ratio of the mold and the understanding of the fluid flow motion as well as heat transfer in mold is regarded as the most important information because the melt delivery is directly related to the problems of shell growth nonuniformity, surface turbulence and mold powder entrapment. A mathematical model has been developed for the coupled analysis of fluid flow, heat transfer and solidification in funnel type mold using finite volume method based on a body fitted coordinate and the characteristics of the transport phenomena in the mold of thin slab caster were analyzed by numerical simulation. As a result of simulation, the basic flow pattern is characterized as four large recirculations and two small eddies near the narrow faces of mold, which is somewhat different from that of parallel type mold or other conventional slab caster. The heat transfer model accurately predicted the mold positions susceptible to cracking as a result of thermal stress and the predicted shell thickness shows good agreements with the measured shell thickness on breakout products. We also investigated the influences of some operation parameters such as casting speed, nozzle type, submerging depth and mold material on fluid flow, heat transfer and distribution of solidifying shell and various information for the determination of optimal operating conditions were obtained.

Jan 1, 2000

By Toshihiro Tanaka

The information on viscosity and surface tension of molten slag is indispensable to design new refining procedures in ferrous and non-ferrous processes. For example, the authors have tried to develop "Capillary Refining" to remove impurities in liquid metals by applying capillary absorption of molten slag with those impurities into solid fluxes which have a lot of small capillary tubes. It is necessary to adjust the above physico-chemical properties to adequate conditions on the capillary penetration. In the present paper, we discuss our recent trial to predict surface tension and viscosity of molten slag in multi-component systems. We have derived a thermodynamic model to predict the surface tension of molten slag by using ionic size, molar volume and surface tension of pure components. In addition, we have applied neural network computation to evaluate the viscosity of molten slag. We found good agreement of the calculated results with experimental values of the surface tension as well as the viscosity in various slag systems.

Jan 1, 2006

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