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By Felipe Daroch, Maria C. Ruiz, Rafael Padilla

Copper concentrates with high arsenic contents must be pretreated before conventional smelting to prevent environmental pollution with arsenic compounds. In this work, experimental results concerning the selective removal of arsenic and antimony from copper concentrates are presented. The process consists of an alkaline digestion using concentrated NaHS-NaOH solutions to transform the arsenic and antimony sulfides into soluble compounds. A water leaching follows the digestion to dissolve the arsenic and antimony, leaving clean copper sulfide solid residues. The laboratory scale tests were carried out using a copper–arsenic concentrate with 15.05% As and 1.42% Sb. The results showed that the most important digestion variables were temperature and concentrations of NaHS and NaOH. Over 97% of arsenic and 92% of antimony could be removed in 10 min of digestion using 8.9 M NaOH and 100% excess of NaHS at 80 °C. The subsequent water leaching was performed at 80°C for 20 min.

Jan 1, 2015

By Run-boWang, Fan-yi Meng, Jian-Liang Zhang, ZheWang

To elucidate the influence of high Al2O3 content on sinter softening and melting behavior, heating-up reduction test under load was carried out. In addition, microstructure study of sinter bed structure change at a different temperature was also made and the mechanism that the effect of Al2O3 content on sinter softening and melting property was discovered. SEM results showed that the increase of Al2O3 content favored the formation of Al2O3-rich slag phase, such as the eutectic (2CaO·SiO2-2CaO·Al2O3·SiO2-FeO) and gehlenite (2CaO·Al2O3·SiO2), resulting in the decrease of sinter Ts temperature. Further, high Al2O3 content improved the concentration of metallic iron and lowered the dripping temperature due to the decrease of slag liquidus temperature and viscosity. At a fixed basicity, it was indicated that there was a relationship between Al2O3 content and sinter softening-melting property. Based on the results, counter strategies to cope with the adverse effect of high Al2O3 content on the cohesive zone property were also proposed. It could provide guidance for the blast furnace operation of sinter with high Al2O3 content.

Jan 1, 2015

By Caisa Samuelsson, Taishi Matsushita, Hannes Holmgren, Sina Mostaghel

"Rönnskär Smelter of Boliden Mineral AB, Sweden, is a large end-processor of secondary raw materials and waste, including electronic scrap. Electronic scrap may introduce various impurities to the smelter's flow-sheet, among which alumina is a common and significant one. This article summarizes the results of an ongoing research at Luleä University of Technology, Sweden, to study the influences of alumina on different properties of slag from the zinc fuming process at Rönnskär smelter. A combination of different experimental techniques and thermodynamic calculations have been used to investigate properties such as density, surface tension, effective thermal diffusivity, viscosity, and melting/leaching behaviors. Results show that the addition of alumina to this slag increases the degree of polymerization of the melt, and physical properties vary correspondingly. Mineralogy of the semi-rapidly solidified samples is also changed due to alumina addition. A correlation between mineralogy and leaching behavior can be observed.IntroductionBoliden's Rönnskär Smelter is a base- and precious-metals producer located in north of Sweden. Its main products are copper, zinc clinker, lead, gold, and silver. Sulphuric acid, liquid sulphuric dioxide and iron sand (granulated slag) are some of its main by-products. In order to optimize the overall outcome of the process, different refining units are integrated in the smelter's flow-sheet (Figure 1). Copper concentrates and fluxing materials (mainly silica sand) are charged to the process. The produced matte is sent to the converter and the generated slag is charged to the fuming furnace, where it is treated by reducing gases to produce zinc clinker. The converter's slag is charged to the electric furnace, while the fumed slag is tapped into the settling furnace for further cleaning, where matte, slag and speiss (residual metals) are separated. The matte from the settling furnace is also sent to the converters; its speiss is sold to external customers; and its slag is water granulated and sold as construction material, which is known as iron sand."

Jan 1, 2012

By B. R. Westphal

The Integral Fast Reactor (IFR) concept being developed by Argonne National Laboratory is based on the pyrometallurgical processing of spent nuclear metallic fuel with subsequent fabrication into new reactor fuel by an injection casting process. During fabrication, a dilute scrap stream containing uranium alloy fines and broken quartz (Vycor) molds is produced. Waste characterization of this stream, developed by using present operating data and chemical analysis, was used to evaluate different uranium recovery methods and possible process variations for the return of the recovered metal. Two methods, comminution with size separation and electrostatic separation, have been tested and can successfully recover over 94% of the metal. Recycling the recovered metal to the injection casting process was evaluated for the different economic and process impacts. The physical waste parameters and the important separation process variables are discussed relative to their effects on the viability of recycling the material. A discussion of the criteria that is being used to establish the acceptable operating limits is also presented.

Jan 1, 1992

By Andres Vikdahl

The Rönnsktär smelter has recently undergone a series of technical and operational changes. This changes are caused by our own will to remain and gain in competivety and to adapt to the ever changing surroundings. To be able to remain competitive in surrounding with high wage costs, high inflation and high environmental standards thorough cost management is needed. The Swedish economic policy in the beginning of the 80'ies consisted amongst other things of two devaluations. The exchange rate of the Swedish Krona was reduced with approximatively 25 %. This boosted the profits of our export industry, some even believed we entered the land of milk and honey ... And working in this promised land where everything turns into profit it is very difficult to be careful and restrictive with your spendings. Apart from some healthy and fruitful investments we allowed ourselves yearly steady increases in salary for ever reduced number of worked hours and we of course employed more people. Inflation rates went up and so did property prices. In 1986 finally reality catched up on us. Reality in the form of too high costs started to hit Swedish export industry 5-6 years after the big devaluations. Furthermore the high inflation rate also hit the domestic industry a couple of years later. Together with other important factors Sweden faced a severe home-made recession in the beginning of the 90'ies. With this background we now report and analyse our smelter's performance and operating results, shown in fig 1 The main constrictions on smelting and refining at Rönnsktär are today: * Income restrictions by governmental production level Limit * Throughput resmctions by governmental emission limit * High capital costs in the aftermath of Swedish high inflation in the recent decade * Low work force turnover Below we will illustrate how we tackled with these issues along the following lines: * People * Quality * Technology

Jan 1, 1993

By J. R. Bhamidipati, Nagy EI-Kaddah

"Over the years, mathematical modeling has been established as a viable tool for design and analysis of melting and solidification processes. Modeling of electromagnetic casting and melting systems involves three coupled problems -- determination of the containment field, the shape of the meniscus, and the temperature field -- which have to be solved simultaneously. One of the difficulties in numerical simulation of these systems is in defining and gridding the solution domain as the meniscus shape of the liquid region is not known a priori. This paper describes a methodology for solving these coupled problems in a two-dimensional electromagnetic containment field. This method is based on the solution of the electromagnetic, free surface dynamic, and heat transfer equations in a fixed domain in computational space by mapping the physical space into an invariant computational space during the search for the equilibrium shape using a variable non-orthogonal coordinate transformation. This approach, also, eliminates the need for regridding the liquid and solid regions during phase change. This methodology is demonstrated for two electromagnetic confinement systems -- the Magnetic Suspension Melting process and the electromagnetic casting of aluminum. The model predictions are in good agreement with available data for these systems. It is suggested that the methodology presented here is likely to provide a useful tool in the design, analysis, and optimization of electromagnetic confinement systems. IntroductionDuring the past decade, mathematical modeling has emerged as a viable tool for the design, analysis, and optimization of casting and melting processes /1-2/. It is generally recognized that the usefulness of modeling to study the interplay between the various process parameters without resorting to extensive experimentation relies heavily on accurate representation of the physical phenomena in these systems. In modeling electromagnetic confinement casting and melting systems, it is important that the model address all aspects of electromagnetic field interaction with the metal, if accurate predictions are to be obtained /3/. The electromagnetic field affects the heat transfer phenomena primarily through joule heating. In addition, the electromagnetic forces play a key role in heat redistribution in the molten pool via melt stirring, and, in confinement systems, support the molten metal pool."

Jan 1, 1994

By Ivan Imris

The iron production has generated many tonnes of very fine residues with high concentration of iron. In addition, during the recycling of galvanised steel scrap in the steel making processes the zinc and lead are largely concentrated in the dust. These kinds of dusts are usually dumped beside the metallurgical plants and cause environmental problems. Therefore the metal recovery from the metallurgical residues has become a major interest not only from the viewpoint of metals recycling but mainly from the viewpoint of environmental land protection. The thermodynamic analyses and laboratory experiments suggested that the metals could be recovered from metallurgical wastes by reduction roasting and by plasma smelting processes. The iron rich pellets with very high metallization may be obtained from metallurgical wastes by the reduction roasting and the inert slag and pig iron could be produced by plasma smelting processes. In both cases the iron rich products are suitable for the steel production. During the reduction roasting or plasma smelting the high volatile zinc and lead metals were removed and enriched as a secondary dust, Zn-Pb concentrate, which is suitable for processing in zinc and lead smelters. Suggested processes are commercially feasible and environmentally friendly without any solid or liquid waste.

Jan 1, 2003

By Young-Sool Jin, Heung Nam Han, Hong Joon Kim, Jae Kon Lee

A mathematical model was developed considering non-symmetric cooling' and stress distribution in both thickness and width direction of strip on a run-out table of hot strip mill. In order to solve a transient heat transfer equation including the heat evolved from phase transformation, a finite element method coupled with thermodynamic and kinetic analyses was applied. The heat capacity of each phase and heat evolution due to phase transformation were obtained from the thermodynamic analysis of the Fe-C-Mn-Si system based on a sub lattice model. The phase transformation kinetics of the steels was derived by using an inverse additivity technique with continuous cooling experiments. Heat transfer coefficients of strips on the run-out table were, by applying an inverse method, determined from the actual mill data under various cooling conditions. As for the stress analysis, the density change of strip due to cooling and phase transformation, and the transformation superplasticity were considered. A 90nstitutive equation for the transformation superplasticity, which is related to the phase transformation kinetics and the internal stress due to the density change of strip, was applied. A finite element method was adopted to calculate the deformation behaviour of strip on a run-out table of hot strip mill. Using the models, the temperature-phase-deformation history and distribution of a strip on the run-outtable was calculated.

Jan 1, 2001

By S. Niyomwas, R. G. Reddy

"A mathematical model was developed to describe the plasma gas and particle dynamics and conversion yields. The velocity and temperature fields in the plasma were calculated by solving 1 the Navier-Stokes equations and the thermal energy balance equations. Conservation equations for the system species consider the multi-component diffusion and chemical reactions. Through the application of this model, temperature distribution, flow fields, and production rates were computed. The model was used to study the thermal decomposition of ilmenite in the non-transferred arc plasma reactor. The computed production rates of TiN from ilmenite using nitrogen and methane gas mixtures, are in the range of 5 to 100 x 104 kg/m3/s at 2500 KIntroductionThe widespread interest in thermal plasma processing has stimulated a great deal of research effort into the various aspects of this process, including plasma' spraying, thermal plasma chemical vapor deposition, plasma synthesis of fine powders, thermal plasma decomposition, plasma melting, and plasma extractive metallurgy.In the plasma synthesis of fine powders, the earlier experimental and theoretical studies aimed at predicting the final products1-5. Then it was followed by more recent investigation concerning the profile of plasma gas velocity, plasma temperature and concentration. In this regard, useful plasma processing models have been reported by numerous investigation6 -11 which were increased by both theoretical analysis and measurement.As a result of this work a reasonable plasma-processing model is proposed. It is to be noted that all the thermal analysis that has been made neglected the fluid -flow effects. Also, in the analysis aimed at the quantitative description of the fluid-flow field, the effect of heat transfer was not taken into account."

Jan 1, 2000

By Mathilde Guilpain

A wide variety of plants are able to extract nickel (Ni) from soils and accumulate this metal in their foliage. Hydrometallurgical processes have been developed to recover Ni in the form of metal or salts, starting from the plant A. murale. They include: (1) a combustion step, to obtain ash containing 15–20% Ni; (2) a leaching step; and (3) purification. That whole flowsheet has been thoroughly investigated, and the processes scaled up to the pilot scale. Another strategy is presented here, consisting of recovering Ni without burning the plant. Ni can be extracted from the dry plant by water leaching, but the leachate is a multi-element solution from which Ni has to be separated. Selective precipitation of Ni hydroxide is not possible since Ni is bound to organic ligands. In this work, the plant leachate is processed by adsorption on the chelating resin DOWEXTM M4195. The results showed that Ni was selectively retained whereas the other main cations were not. Nickel could be recovered at the elution step. This methodology needs to be further investigated but these initial results are very encouraging and open the possibility of Ni recovery by agromining.

By Markus Aspiala, Fiseha Tesfaye, Pekka Taskinen

In this paper, the standard thermodynamic properties of Ag3Sb and Ag6Sb intermetallic compounds have been studied by the solid state EMF-method, using Ag+ ion conducting β- alumina and AgI. The intermetallic compounds were synthesized from pure substances in evacuated silica ampoules and their formation were confirmed by the SEM-EDS analyses. The EMF measurements were made on electrochemical cells of the type [Ag | β-alumina | Ag-Sb] and [Ag | AgI | Ag-Sb]. The usage of β-alumina electrolyte, in this study, enabled thermodynamic measurements of the Ag-Sb-intermetallic compounds above 710 K, hitherto unreported. Based on the new experimental data, thermodynamic properties of the Ag-Sb-intermetallic compounds have been determined. The obtained experimental values have been compared with the available literature data.

Jan 1, 2015

By Xinlei Jia, Wenming Guo, Yanling Zhang

A large amount of stainless steel dust rich in Fe, Cr, and Ni has been being generated in China. Smelting treatment is accepted as a practical method for the recovery/reutilization of these second resources, during which Fe, Cr, and Ni is reduced into one metal phase and then separated from the residue slag. Based on the typical compositions of stainless steel dust, the residual slag can be termed as CaO-SiO2-MgO-Al2O3 system. In this paper, the activity coefficients of Cr in Fe-Cr-Ni-C (-Si/Al) melt and the properties of CaO-SiO2-MgO-Al2O3- 1%CrO system thermodynamically approached. Then, in laboratory experiments, the recovery ratios of Cr and its distribution behaviors between Fe-Cr-Ni-C melt and CaO-SiO2-MgO-Al2O3 slag system were examined.

Jan 1, 2015

By K. G. Wang, M. E. Glicksman, P. Crawford

"We formulate the mathematical solution to late-stage multi particle diffusion in finite systems. The transition from finite system behavior to that for an infinite system is established. Large-scale simulations are reported regarding the dynamics of phase coarsening. Even in the case of a small volume fraction (Vv = 10-4), the particle size distribution is broader than that for the well-known Lifshitz-Slyozov limit at zero volume fraction. We also report the first simulation studies of extremely low volume fraction, for which corresponding experiments, as well as other simulations, do not exist at present for comparison. However, in the case of moderate volume fractions (Vv = 0.1), the fiucutations in the volumetric growth rate of particles are extracted from our simulations. These simulations provide additional insight into the statistical nature of diffusion interactions, including multiparticle stochastics during microstructural evolution.IntroductionPredicting microstructure evolution in alloys remains one of the cornerstones of materials science. Phase coarsening is a common process in microstrucural evolution that leads to a decrease in the excess total interfacial energy of the system. The system typically consists of separate and identifiable units, or domains, such as second-phase particles distributed in a matrix. During phase coarsening, larger particles grow at the expense of small particles. Over time, this ""competition"" results in an increase in the average size of the particle population, and in a concomitant decrease in the number of particles.Particle size and microstructure of many cast alloys depend on similar coarsening processes. Indeed, properties of these materials, such as strength, toughness, ductility, and electrical conductivity, depend on the material's average particle size and particle size distribution (PSD). Understanding and controlling microstructures in two-phase systems are clearly of widespread technological importance."

Jan 1, 2001

By Upali Siriwardane, Tushar V. Kudale, Naidu V. Seetala

"Cellulose acetate (CA) membranes with 25% triethyl citrate (TEC) as plasticizer were prepared with varying thickness for CO2 gas separation from water-gas-shift (WGS) reaction products. The AFM analysis of the CA membrane showed that the uniform coating had fewer and smaller pores as the film thickness increased, and corroborated by gas permeability studies. The CO2 permeability has decreased faster than CO permeability with the CA/TEC membrane thickness, and findings support that the CA membrane could be used to entrap CO2. Several CA/TEC membranes were also staked to increase the separation efficiency. Positron Annihilation Lifetime Spectroscopy (PALS) was used to estimate the nano-porosity (pore size and concentration) changes of CA/TEC films. PALS results show a decrease in pore size with increasing CA-TEC concentration in acetone, while the pore concentration increases. The PALS results are correlated with the CO2/CO permeability variations as the CA-TEC concentration change.IntroductionHydrogen is one of the main energy sources available for the future advancement of clean fuel technologies especially for fuel cells. Generation of hydrogen and CO2 from Water Gas Shift (WGS) reaction mixtures of CO and H2O is of interest to many researchers since it allows a large scale production of hydrogen [1, 2]. Once hydrogen is produced using the WGS reaction, the output products contain mixture of CO, CO2, H2, and water vapor. Metallic membranes have been used as hydrogen separation membranes [3-6]. As H2 is separated from the mixture using the metal membranes, we need to separate CO2, and find ways of sequestration of CO2 to avoid environmental problems by greenhouse gasses. Polymeric Membranes have been used for CO2 separation [7]. Plasticizer can control the micro-structural properties such as pore size and concentration of polymer membranes [8], which influence the size/molecular weight dependent diffusion rates of the gas molecules. We have used cellulose acetate with triethyl citrate as plasticizer to separate CO2 from the WGS reaction products. Positron annihilation lifetime spectroscopy (PALS) is very sensitive and able to identify different kinds of defects and their agglomerates such as vacancies, vacancy loops, and voids [9, 10]. PALS has been successful in determining the free volume in polymers that influence the properties of the polymers [11, 12]. Microscopic properties of the free volume obtained from PALS have been correlated to macroscopic properties [13, 14]. We used PALS to study the nanoporosity (pore size and concentration) and fractional free volume changes of CA/TEC films, and used to understand the variations observed in the CO2/CO permeability as the CA-TEC concentration in the membranes change."

Jan 1, 2014

By Luis W. Pommier

The developed processes, the subject of this paper, extract the hydrocarbons, halogenated organic compounds and metal contaminants from hazardous soils, rendering them non-hazardous and ready to be placed back on the ground. The processes first segregate a non-contaminated fraction from the contaminated soil. This initial task is performed using available minerals processing technology: sizing, gravity separation, magnetic separation, froth flotation, etc. The remaining contaminated fraction, is submitted to two leaching operations for the removal of organic and metal contaminants, whenever both are present or to a single leaching operation if only one type of contaminant is present. The decontaminated soil fraction is mixed with the non-contaminated fraction and is placed back on the ground. The leaching liquors, used at neutral pH, are non- hazardous. After decontamination the liquids are processed to extract the contaminants, now valuable materials, for commercialization. Organic contaminants are removed by distillation of the solvents. The metal contaminants are precipitated in their oxide form. In both cases the regenerated solvents are recycled. The decontamination processes are economically competitive with transportation and disposal of the soils to permitted facilities for hazardous materials, and most importantly the developed processes remove the liabilities from the Responsible Parties. The law establishes that these liabilities do not disappear with either fixation nor with transportation and disposal since the environmental liabilities are of the ? cradle to grave? type.

Jan 1, 1994

By Xiangwen Wang

Electrodeposition of lead metal from high purity brine electrolytes containing lead chloride (PbCI,) was conducted so as to assess the feasibility of electrowinning lead-metal directly from aqueous chloride electrolytes. Tests were performed at 65 and 80°C (338 and 353°K). Characteristic features of the deposits, on both lead and graphite substrates, were correlated to operating parameters associated with: electrolyte temperature, current density and total lead- concentration. Photomicrographs of these morphological features were obtained by use of Scanning Electron Microscopy (SEM).

Jan 1, 1993

By A. F. Giamei, F. Landis, M. O. Duffy, R. J. Mador

"The directional solidification of complex advanced gas turbine airfoils must be carried out without the nucleation of undesirable grains and with minimal shrinkage. Such problems are typically eliminated by using a number of mold design and process iterations. A more efficient approach is envisioned where a solidification model is generated and utilized to accelerate process development. Towards this end, the directional solidification (DS) of simple geometrical shapes in a crystal grower apparatus has been simulated with MARC finite element nonlinear thermal analyses.The finite element models of cylindrical (2D) and rectangular (3D) cross-section bars in the DS environment are presented. Temperature dependent properties, the impact of latent heat of fusion and a time-dependent radiation boundary condition constitute the more salient features of the MARC models. Solidification zone thermal behavior is predicted during the withdrawal transient for the specific case of nickel based superalloys grown in ceramic shell molds. Comparisons of analytical results with experiments demonstrate notable prediction accuracy. INTRODUCTIONSingle crystal and uni-directional crystal turbine blades require tightly controlled conditions if metallurgically and mechanically acceptable parts are to be produced. Gated blade geometry and process parameters must be precisely determined if incorrect grain structure, orientation and shrinkage are to be avoided. Since purely experimental development programs designed to evaluate these parameters can be excessively costly and time-consuming, an effort combining engineering analysis and verification by experiment has been initiated at Pratt & Whitney. Comparison of analytical predictions and measured data for geometries simpler than a turbine blade, namely cylindrical and rectangular bars, comprised the initial stage of this effort. Subsequent tasks involve modeling geometries of increasing complexity and ultimately the simulation of the directional solidification of the turbine blade, shown schematically in Figure 1. This paper summarizes the results of the initial stage of the effort."

Jan 1, 1986

By Roberto Parra

The classic criteria of the preparation of the charge for the smelting of copper concentrates in a flash furnace considers the mass and energy balance from the chemical and mineralogy composition of the concentrates. The operation parameters fixed with this method don't assure the stability of the operation and the critical problems of the slag quality and dust formation occurs very often. This paper presents the results of a laboratory test that allows the predicition of the behavior of concentrates blends in the view of the minimization of the dust formation and the magnetite control in the slag. The combustion of different copper concentrates and blends were done in a drop tube furnace. The results show that the magnetite and dust formation don't have a linear behavior with the weight proportion of the blend and some optimal blends of 2 or 3 types of concentrates can be identified. From the reasonable hypothesis that the qualitative behavior of blends in the drop tube represents the real behavior in the burner, the preparation of the charge with this approach could help to solve those operational problems.

Jan 1, 2003

By Lawrence D. May, Harry Mudgett

"In the course of developing a new industrial process, information produced at the Research and Development (R&D) stage is critical to determining the technical and economic feasibility of the project. Understanding the fundamental operating parameters for each unit operation in a flowsheet typically comes from historical knowledge of similar systems or by technical development through a robust research program. This approach holds true for processes incorporating fluidized-bed technology. In this paper, the authors will present a practical approach for performing a research study that will allow a process owner to determine if the concept of using a fluidized-bed system can become a reality. Included are discussions of key steps required at each level of the R&D program, and the critical information required for advancing the project to the next stage.IntroductionThe conduct of a research and development program typically starts with a process owner identifying a new industrial need or modification to an existing operation. The owner can pursue this need through multiple routes, including initial in-house development, coordination through an engineering firm, contacting suppliers of key equipment envisioned for the process, or through direct contact with research and development organizations. Where and when the project is conducted is as variable as the number and types of owners who pursue them. Factors that can influence the decision of where to conduct a research program can include the type of process desired, the scale and scope of the project, the location of the project site relative to the R&D options, the experience, capability, and availability of the potential research sources, and the costs to conduct the program. Often, the owner may choose a combination of the available resources to achieve their objectives. In the end, the owner's choice should be based on a thorough understanding of their goals and objectives for the program, and a good understanding of how to measure success while achieving those objectives. Herein, the authors will describe the methods we have typically used to develop the information an owner needs to make an educated decision for investing in a new or modified process."

Jan 1, 2014

By Patricia A. Wells

In the remelting of scrap, the ultimate goal is to produce clean aluminum while minimizing metal losses. Recently, it has become more difficult to make significant recovery improvements in Reynolds' Reclamation Plants since metal recoveries were nearing the theoretical maximum. In an effort to gain a better understanding of the factors impacting Reynolds remelting process, a series of experiments using a Taguchi-type design was performed. Specifically, the critical variables and interactions affecting metal recovery of shredded, delacquered Used Beverage Containers (UBC) melted in a side-well reverbatory furnace were examined. This furnace was equipped with plunger-style puddlers and metal circulation. Both delacquecing and melting processes operated continuously with downtime only for necessary mechanical repairs. The experimental design consisted of an orthogonal array with eight trials, each using nominal 500;000 lb shred charge volumes. Final recovery results included molten output and metal easily recovered from dross generated during the test.

Jan 1, 1995