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By Joel K. Witt

San Manuel Oxide operations of BHP Copper, located in Southeastern Arizona, operates a leach-solvent extraction/electrowinning (SXEW) facility that produces high quality cathode copper from low-grade oxide ores. Permanent heap leaching and in-situ leaching methods accomplish the dissolution of copper from the oxide ores. Open pit mining and heap leach construction took place from 1985 to 1995. Run-of-mine oxide ore from the pit was hauled to the heap dumps and leached by the soaking cure and continuous irrigation method. Solution application to the heaps still continues and acid soluble copper recovery has reached 86%. This paper presents and discusses the current operating practices and innovations applied to the leach facilities to maximize copper recovery from the heap leached residue. Factors such as irrigation methods, solution chemistry, sideslope treatment, post curing, lixiviant acid strength, and "rice paddies" irrigation, will be discussed. Heap leach solution control and sampling methodologies will be also presented.

Jan 1, 1999

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 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 B. Yawney

A copper-nickel sulfide concentrate was leached in water at about 2000C under oxygen pressures of about 0.35 MPa. Oxidation of sulfide to sulfate was virtually complete in about 30 minutes, resulting in greater than 95% copper and 98% nickel extractions. Leaching temperature was shown to be the most important factor affecting metal extractions. Measured rates of oxygen consumption were used to develop batch kinetic data. Mini-plant continuous pressure leaching tests agreed with batch leach results. A proposed overall flowsheet is briefly examined.

Jan 1, 1976

By Uday B. Pal

In the electrochemical vapor deposition (EVD) process, gaseous cation precursors are passed over one side of a porous substrate, and oxygen is passed on the other side of the substrate. The gases diffuse and react within the porous substrate, and the pores get filled with the desired solid oxide. Subsequent solid state electrochemical transport through the solid oxide in the pores continues the reaction, and the film grows over the porous substrate. The EVD process has been used to deposit lanthanum chromite interconnection films and yttria stabilized zirconia electrolyte films over porous air electrodes. The EVD growth of these solid oxide films is found to be parabolic in nature, which indicates that the solid state transport (diffusion) of ions through the film controls the growth. This solid state transport can be analyzed using Wagner's treatment of the electrochemical transport. Conductivity measurements and the information on the defect structure of the oxide can be combined with the EVD growth rate measurements to calculate the solid state transport properties (transport numbers and partial conductivities) of the rate-controlling minority species in the oxide. Using this approach, the EVD growth of other electronic, mixed conducting and ionic solid oxide films can also be analyzed.

Jan 1, 1992

By Kimio Itagaki

Thermodynamics and rate process fundamentals are two of the important principles involved in nonferrous production processes. The process configuration establishes whether thermodynamics or rate process behavior is most relevant in a particular application. In this paper, thermodynamic theory and rate process fundamentals are used to analyze the main characteristics of smelting and converting processes. The effect of increased oxygen potential .is examined with emphasis in view of the increased use of highly oxygen-enriched gas in modem smelting processes. Phase equilibrium and the distribution of minor elements between copper or nickel matte and FeOx-SO2- or FeOx-CaO-based slag are reviewed. The use of oxygen-rich gas has no serious effects on 'the recovery of valuable copper and silver in the matte phase, while the recovery of nickel and cobalt is adversely affected. The oxygen content in the gas also strongly affects the distribution behavior of arsenic, antimony and bismuth. Analysis of the rate processes occurring in the shaft of flash smelting, and converting furnaces by a 3-D computational fluid-dynamics model is also discussed. After being validated with experimental data collected in a large laboratory furnace, the computer model has been used to simulate the main features of an industrial flash converting operation. The results present quantitative features of the improved mixing of the particle-gas suspension and increased oxygen efficiency obtained with a distributor-cone burner compared with those with a single axial entry burner. The role of basic principles in the engineering analysis of high-intensity matte smelting processes is also discussed.

Jan 1, 2002

By Mônica Suede Santos Silva

This work describes characterization of the performance of the tundish of a six strand continuous casting unit of the Companhia Siderúrgica Belgo Mineira, João Monlevade, Brazil using physical modeling. Permanent and transient conditions, due to ladle metal composition changes are considered. Pulse and step tracer addition techniques are employed to assess the control variables. For transient conditions the degree of inter-mixing and the minimum residence time are determined with a view to optimize the process especially during the grade changes of steel.

Jan 1, 2003

By A. Korbel

The progress in understanding the nature of strain localization in metallic materials and in particular the understanding of the role of external (deformation conditions) and internal (material substructure) factors in the development of the tendency toward concentration of plastic flow within transgranular shear bands was the background of the concept given in the title. Following this idea, the practical possibility of replacing the homogeneous in a micro scale mode of deformation by transgrasnular shear bands gives a chance to change the arrangement of the dislocation substructure in the material from that typical for homogeneous deformation into long wavelength (transgranular), pseudo-periodic dislocation walls. The presence or formation of such a substructure in a thermodynamically unstable matrix may result in the formation of the products of phase transformation along shear bands, giving rise to a composite-like structure. This work is aimed to provide a coherent justification to the concept of Natural-Metal-Matrix Composite and summarizes the results of experimental works in this area.

Jan 1, 1997

By Mamoru Kuwabara

A high-power sound which can transmit through any continuous elastic medium with less attenuation, particularly in liquid allows us to externally control the system of concern by using the acoustic radiation force or the cavitation phenomena. These functions may eliminate gravitational and/or atmospheric constraints which are often encountered in conventional operations for producing clean and advanced materials. This paper outlines the recent development in the field of sonoprocessing of materials. Cold model experiments in some vessels have been performed to simulate ultrasonic operations such as inclusion removal from liquid, degassing of melt, emulsification of two liquid phases, solidification processing, and decomposition of chemical species in waste water. High speed visual imaging is carried out for better understanding of the cavitation phenomena as well as the followed microjets during the processing. The radiation force acting on fine suspending objects in a fluid can be utilized for eliminating or rearranging/orienting the objects in the fluid. Acoustically induced cavitation phenomena in liquid can be utilized as an effective dynamic means to control interfacial phenomena as well as micro- and macro-mixing of liquid. Sonochemical and thermal effects in cavitation multi-bubble can be also useful in a waste water treatment.

Jan 1, 2006

By William Petruk

An investigation was conducted to determine types of particles that tend to be recovered in concentrates by mineral beneficiation. It was found that, in concentrates of the same grade the proportion of desired mineral occurring as apparently liberated grains varies widely. In contrast the proportion is nearly constant when the grains considered are apparently liberated grains plus unliberated grains in particles composed largely of the desired mineral. It was also found that the types of particles which tend to be recovered in concentrates are dependent upon the concentrate grade. Hence it is much more important to determine the characteristics of recoverable particles and to measure the percentage of mineral that occurs in recoverable particles. than to measure the percentage of totally liberated mineral. A relationship between concentrate grade and type of particle that tends to be recovered in concentrates was established.

Jan 1, 1989

By Guo-Sen Zhu

Research on the formation mechanism and control of corner transverse cracks was carried out. The optical microscope and SEM were applied to analyze the characteristics of cracks. It is found that the cracks occur at the relatively lower temperature due to unbending strain and have almost nothing to do with the mold cooling and powder. The keys to prevent corner transverse cracks are to optimize the corner temperature of slab and maintain the good state of casting machine. Increasing casting speed and decreasing the cooling water flux at the corner in the unbending segments, resulting in mild cooling, were applied during investigation to control corner temperature above the upper limit temperature of the No.3 brittle zone of Nb-contained steel tested by Gleeble-1500 system. As a result, corner transverse cracks were minimized, but centerline segregation got worse. And then increasing the cooling water flux at the corner (intensive cooling) was applied to make corner temperature below the lower limit temperature of the No.3 brittle zone. Great diminution of both corner transverse cracks and centerline segregation was achieved finally.

Jan 1, 2006

By E. L. Frueh

AMAX Base Metals Research & Development, Inc. has developed a process for treating copper-nickel mattes to produce copper cathodes and a pure nickel sulfate solution. In this process, the input matte is preleached in a copper sulfate electrolyte bleed solution so as to dissolve nickel from the matte and cement copper from solution. The preleach leaves a substantially pure nickel sulfate solution. The residue from the preleach is roasted to less than about one percent sulfur. A portion of the calcine is leached with sulfuric acid to make a copper sulfate solution for input to the tank house. The residue from this leach and the remaining calcine are smelted to form a bimetallic (copper/nickel.) anode. The anodes are electrolytically refined and copper is preferentially deposited on the cathode while the nickel reports to the electrolyte, A bleed stream is taken from the electrolyte and used in the preleaching of the input matte. This process produces high purity metal streams while consuming less energy and smaller amounts of reagents as compared with other matte processes.

Jan 1, 1983

By Charles I. Richman

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

Jan 1, 1998

By N. Moelans

A method using an ex-situ electrochemical measurement device was developed to determine the oxygen potential of non-ferrous metallurgical slags. The electrochemical cell consists of the molten slag sample, an inert Ir electrode, a stabilized Zr02 solid electrolyte and a NiINiO reference electrode. Different slags from non-ferrous pyrometallurgical processes were analysed at 1100 and 1200°C and pO2 values between 10-3 and 10.12 bar were obtained. The measurements were evaluated with? thermodynamic calculations and using processing considerations. It was found that the reproducibility and stability of the measurement was significantly improved by shielding the molten slag from the atmosphere by a thin layer of carbon, especially for slags with a low oxygen potential.

Jan 1, 2003

By M. Misra

The prediction and assessment of the reactivity of acid mine tailings has been a subject of numerous studies. The conventional approaches such as sulfur content, pH, net acid generating capacity and conductivity are used for assessing reactivity of the tailings. In this paper a new non-invasive Impedance Spectroscopy (IS) technique is used for the determination of reactivity and acid mine potential of tailings. This technique is also used to establish the long term stability and leaching propensity of the tailings agglomerated with alkaline binders.

Jan 1, 1994

By Fernando Guevara

Many smelting and slag-cleaning furnaces operate with cooling systems designed to freeze a slag layer over the refractory to protect it. The fluid flow and heat transfer conditions associated with the freeze layer and mushy zones are poorly understood. These phenomena were simulated with a small-scale room temperature, 2-dimensional model, using an aqueous solution of calcium chloride to simulate the slag. Reasonable similarity with conditions encountered with copper and nickel smelting systems was achieved (Pr 50 and Ra 108, in the laminar-turbulent transition). Measurements of the freeze layer development and velocities were made with the Particle Image Velocimetry (PIV) technique. Direct Numerical Simulations (DNS) were also made of the unsteady fluid flow and heat transfer problem. It was found that the solidification process is well described using an improved model for high molecular viscosity in the mushy zone. Solid front growth, isothermal profiles, velocity profiles and heat transfer through the walls showed good agreement between the PIV and DNS results. Experimental and numerical velocity profiles close to the freeze layer show a parabolic behaviour in the vertical velocity profile which is completely different from the calculation of heat transfer using a sharp interface model. The reason for this is attributed to the effects of the mushy zone with a high viscosity and high shear stresses acting on that area.

Jan 1, 2006

By Sergio Bustos

Covellite resulting from an original 0.5 % Cu(tot) chalcocite ore has been leached in columns at different temperatures, in the lower range of 10 - 20 °C, under acid - ferric bacterial leaching conditions. Dissolution of copper from covellite depends on the rate and extent of sulphide oxidation by ferric ion. While it is recognised that the dissolution of sulphide minerals is electrochemical in nature, an apparent chemically controlled dissolution pattern was measured with activation energy of 78.09 kJ/mol (18.66 kcal/mol). Ferric iron is the main oxidant and its production and availability will depend on the bacterial activity developed in the system. This activity is characterised by the population size and by the specific oxidation rate of the bacteria. Bacterial growth was followed directly by the number of bacteria appearing in the column effluent solutions and indirectly by the generation of ferric iron or by the total oxidation observed in the columns. These results have been interpreted by using the heap oxidative capacity parameter, which indicates an equivalent ferric production of about 0.07 - 0.15 kg Fe +3/t/day at 20°C. Although bacterial activity decreases to about 0.03 kg Fe +3/t/day with decreasing temperature, a significant bacterial oxidation is still observed at 10 °C. However, extended lag times are observed, which delay the start of bacterial growth to times concurring with covellite leaching. Under these conditions, bacterial activity is displayed through a population controlled by the rate at which- ferrous iron is released from the reducing covellite surface. These results suggest the potential benefit of including some kind of inoculation when operating at lower temperatures. Also, heat loss control and/or heat addition to the heaps should be considered during process design and operation of ferric bacterial heap leaching of secondary copper sulphide ores at temperatures lower than 20°C.

Jan 1, 1999

By B. G. Belew

Recent operating improvements at the Phelps Dodge Chino Smelter, coupled with intensive capital expenditures since 1987, have resulted in a safer, higher quality, more productive smelter. This paper briefly reviews the flowsheet of the Chino Smelter with emphasis on recent capital expenditures. The main focus of the paper is to provide case studies of how operating functions have been improved. Case studies presented include: (1) safety, (2) anode quality control, (3) flash furnace cross-over build-up control, and (4) flash furnace temperature control. Most of these accomplishments have been achieved by providing specific measurable goals and subsequent feedback to operating crews.

Jan 1, 1993

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 Christian Redl

"The Lattice Boltzmann Method (LBM) solves fluid dynamics problems based on a discrete mesoscopic approach. It is based on the Lattice Boltzmann equation which is a special discretisation of the continuous Boltzmann equation. Its principle advantage is that it can handle complex physical phenomena (like interaction between different components and surface effects), complicated boundary and initial conditions very well, free from many gridding and stability constraints that plague conventional numerical methods used for fluid flow simulations. Complex structures like porous media can be resolved directly. The LBM algorithm has a simple structure and acts locally, which is favourable for parallel computing. Its potential for metallurgical process simulation is demonstrated in the present study which is concerned with the simulation of the fluid flow in a copper winning electrolysis cell. The electrolyte is modelled as the carrier fluid and the oxygen is considered via a so called active scalar equation. The modelling of buoancy, momentum exchange and the free surface requires special effort. The results of the simulation are validated against experimental data obtained by Laser-Doppler-Anemometry. Despite the simplifications made, good agreement between the simulation and the experiments was found.IntroductionThe hydrodynamics in an electrometallurgical cell is a complex, highly non-linear phenomenon. It includes the simulation of a two component system with high density ratio, gravity driven flow and a free surface. A general solution to this problem is currently unknown.The flow field is a result of the combination of various hydrodynamic effects [18]. Metal deposition at the cathode yields in a decrease in the ion concentration, which reduces the density of the electrolyte. At the anode molecular oxygen is formed as a consequence of the oxidation of water molecules. The oxygen is solved in the electrolyte and again the electrolyte density is decreased. Both effects lead to a free upwards directed convective flow, refered to as natural convection."

Jan 1, 2001