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By R. E. Fanning

"IntroductionThe Aluminum industry is one of many materials industries which strive to make their material the preferred choice for large volume products. In some applications one material has a natural advantage over others, but more frequently several materials compete with one another, each providing one or more advantages and some trade-offs. Customers may design their product with several objectives such as minimum system cost, maximum customer appeal or maximum manufacturing flexibility, choosing materials which best combine cost and performance. In such markets it may become necessary for a material supplier to enhance the attractive features of the particular material to outweigh its disadvantages.It is difficult, if not impossible, to predict how various materials will evolve. Technological breakthrough, government regulations, material availability or sociological issues may redefine the balance between competing materials. In spite of some uncertainty regarding the competitive position of competing materials, there is little doubt that unrelenting pursuit of product quality improvement and cost reduction are essential to future viability of the aluminum industry. It is the intent of this paper to identify some areas where technological improvement would be beneficial. Thus this paper is a collection of briefly described problems that will hopefully stimulate the thoughts and research required for knowledge based solutions. Rolling ProcessA particular example is the beverage can industry where aluminum, steel, glass and plastics vie for a share of the m.arket. The high cost of aluminum relative to steel or glass requires minimizing the amount of metal per can. The high intrinsic value of aluminum has led to extensive recycling of cans although net metal cost is still higher than that of the competing materials. Intensive engineering of the beverage can led to improved design and better understanding of material requirements. These improvements permitted substantial reduction in sheet thickness over the past decade. The downward trend in metal thickness for beverage can sheet is shown in Figure 1."

Jan 1, 1988

By Dai Xi

In the present work, the viscosities of molten FenO-MgO-SiO2 and FenO-MgO-CaO-SiO2 semi-synthetic slags for nickel flash smelting were measured in the temperature range from 1473 to 1723K by a rotational viscometer. The ratio of Fe to Si02 was fixed at 1.2, calcium and magnesium oxide contents varied in the range from 2 to 8 mass% and 9 to 12 mass%, respectively. The results showed that silicate anions became smaller by increasing CaO content, which results in a decrease of the viscosity of the slag. In the case of MgO addition the viscosity behavior was complicated. At MgO content below II mass%, the viscosity increased with the increase of MgO at all temperatures tested. However, when the MgO content was above II mass%, the viscosity decreased slightly for FenO-MgO-CaO-SiO2 system. At higher MgO contents, low-viscosity slags can be obtained by adding CaO. At a given composition, .the viscosity decreased with increasing temperature. The higher the temperature, the more MgO can be added before saturation. The effect of Fe3O4 on the viscosity was quite significant. The viscosity of slag increased by 300mPa-s at 1573K when Fe3O4 content varied from 3 to 9 mass%. The viscosity values are presented as the functions of temperature and composition. A comparison between FenO-MgO-SiO2 and FenO-MgO-CaO-SiO2 systems is given in this study.

Jan 1, 2003

By Deventer Johanna van

Ore bodies around the world are declining in grade, whilst increasing in complexity. The level of impurities relative to the valuable metal is steadily increasing, posing new challenges to existing operations. Ion exchange is widely used in the hydrometallurgical industry for both primary recovery of metals and the removal of impurities. The superior selectivity of ion exchange resins makes them exceptionally suitable for the removal of target impurities to very low levels, thereby saving operating costs, increasing the value of the final product and significantly improving revenue. The ion exchange process in these applications is very simple, using standard ion exchange equipment and acid regeneration. The process can be fully automated, requiring minimal operator interference and supervision Examples of impurities that are successfully removed via ion exchange include iron, antimony and bismuth from copper electrolyte. In the copper electrolysis process, antimony, bismuth and arsenic tend to form slimes which are dispersed in the electrolyte. These slimes contaminate the cathode and/or decrease the quality of the copper deposition. A special chelating resin was developed to remove antimony and bismuth, while at the same time ensuring minimal chloride leakage to the sulphate matrix. The work is described in more detail in this paper. Ion exchange is also used to remove copper, zinc and nickel from cobalt electrolyte. This paper addresses a few of these examples in more detail.

By P. Henry

A novel electrochemical cell has been developed for the recovery of MnO2 from residue of pyrolusite ore leading loaded with Fe, Al Ni, Co and Si impurities, This new process can be considered as an alternative to the traditional methods : S02, H2O2 or bioleaching. It has been observed to proceed fairly rapidly and could prove to be a more economically viable process, as well as being more environmentally acceptable. Electrochemical characterization and kinetic studies have shown that MnO2 is effectively leached by electrogenerated ferrous ions at high current density from a pulp containing less than 5 g8 Fe. The chemical reactions are : Cathode (inox) : 2F23+ + 2e ? 2 Fe2+ Bulk: MnO2 + 2 fe2+ 4H+ ? Mn2+ + 2 Fe3+ + 2 H2O Anode (Pb-Ag) : H2O ? ½ O2 + 2H+ + 2e Global: MnO2 +2H+ Fe2+ = Mn2+ + H2O + 1/2 O2 The catholyte (MnO2 pulp) circulates upward in the expanded mesh cathode separated from the sulfuric acid solution anolyte by a separator which shows high mechanical resistance, low porosity, low potential drop, and reasonable cost. Laboratory and mini-pilot tests have led to the construction of an OT crating pilot plant (100 kg/hr) able to leach more than 95% of Mn, Ni, Co at 1000-1200 A/m2, 50°C with high faradic yield (> 95 %) and low power consumption (3.2 kWh/kg kWh/kg &4D). New applications like the treatment of spent Zn-Mn batteries, polluted soils, spent catalysts and oxide ore (cobalt, nickel) with electrogenerated redox species are now investigated at a laboratory and mini-pilot scale.

Jan 1, 2000

By P. R. Taylor

Laboratory experiments have been performed to evaluate the kinetics of roasting pyrite and arsenopyrite in air at elevated temperatures, in the presence of lime. The effects of temperature, time, air flow rate, particle size, lime type, and mineral/lime weight ratio on the rates of oxidation, lime sulfation, and lime arsenation were studied. The reaction products were identified using chemical analysis, x-ray diffraction, SEM analysis, and optical microscopy. The results are discussed in terms of the utilization of lime to capture sulfur and arsenic during the roasting of refractory precious metal concentrates. More than 99.9% of the arsenic and 98% of the sulfur are contained when roasting pyrite and arsenopyrite with hydrated lime under typical roasting conditions.

Jan 1, 1991

By Laura Angeles, Martin Reyes, Ivan Reyes, Miguel Perez, Francisco Patiño, Mizraim Flores, Elia Palacios

Chemical and mineralogical characterization of a sulphide ore from the mining district of Zimapan, Hidalgo, Mexico, was performed in order to obtain accurate information on the composition of the ore to optimize the subsequent flotation process. A combination of techniques was used: Scanning Electron Microscopy (SEM) with Energy Dispersive Spectrometer (EDS), X-ray diffractometry (XRD), Inductively Coupled Plasma (ICP) and Fourier transform infrared spectroscopy (FTIR). The SEM mapping confirmed the presence of the elements: Ca, Si, Fe, K, S, Al, Zn, Mg and Mn. The XRD analysis suggests that the ore matrix is calcite; additional species found were wollastonite, johannsenite, and pyrite, among other impurities. The FTIR analysis performed for the aqua regia insoluble showed the presence of calcium oxide, copper oxide and silicon oxide. The results for the ICP analysis were:13.31% S, 2.55% Fe, 0.46% Zn, 0.03% Cu, 0.06% Pb, 0.07% Mn, 0.09% As, 0.01% Sb and 0.08 grton-1 Ag.

Mar 1, 2017

By José Carlos Abreu

This work presents a kinetics study covering the effects of temperature over the reduction rates of a carbon composite briquette, aiming its use as burden in some of the new alternate ironmaking technologies, such as the Tecnored process. It is reported that increases in the temperature increases the reaction rate. Additionally, the morphology of the iron phase generated during the reduction of these briquettes is presented. It was possible to verify that three types of iron morphology occurred during the process: an external, dense and continuous iron layer, the presence of iron globules at the center of the briquettes and whiskers at the briquette's core. The measurement of the carbon content on the globules and the external iron layer is also presented

Jan 1, 2003

The cleaning of copper containing fayalite slag using a CuFe alloy was studied under an oxygen pressure ranging from 10-7 to 5 X 10-11 atm at 1200º c. The reduction of copper from fayalite slags by Cu-Fe alloys was found to be very effective. For example, at a P 02 of 10-7 atm, the copper content in the slag was reduced from 4.1 to 0.402 wt. percent after 90 min. of reaction time using a Cu- 5.27 wt. percent Fe alloy. The copper reduction rates were found to be independent of P02 in the gas phase when using Cu-Fe alloys which exhibit an iron activity of greater than 0.4. A mechanism for slag c1eaning is proposed based on the concept that the Cu-Fe alloy lowers the oxygen potential of the slag according to Eq.1 1, fol1owed by the reduction of cuprous oxide by wustite as shown in Eq.2. Here X represents element X in the alloy phase while (X) represents the element in the slag phase. The copper and iron transfer behaviour obtained in this study are explained by a ?Stepwise equilibrium model.

Jan 1, 1985

By E. T. White

The population balance is one of the basic relations for a:n:aIysing particulate minera1 processing operations. It is an exact relation. The principles of the population balance are reviewed and applications in the minerals industry discussed.

Jan 1, 1996

By Rodney Hundermark, July Ndlovu, Lloyd Nelson, Phillimon Mukumbe, Paul van Manen, Whitey Seyanund, Bart Pieterse, Bertus de Villiers, Diale Mokwena

The 2003 redoubling in power to 68MW on the Polokwane Smelter furnace represented a significant intensification in platinum group metal (PGM) smelting. Combined with onerous ‘green’ PGM concentrate smelting requirements, this yielded conditions unusually corrosive to copper coolers and refractories. This presented unexpected operational and design challenges to reliable crucible operation and maintenance. Combined with specific operational control intervention, development of protective coatings has led to the life of water-cooled copper components improving from 9 to 40 months. The furnace matte endwall was extended in 2010 to address accelerated wear of refractories and the potential risk for contact of copper components by superheated matte. An 18 month planned endwall rebuild cycle has been demonstrated (versus catastrophic failure within 9 months). Finally, benefits including lower energy consumption, improved metal recoveries and higher productivity resulting from operational and in-house design developments will be described, that justify “Celebrating the Mega-scale” in PGM smelting.

Jan 1, 2014

By Keith Rozenburg, Ivar Reimanis, Jesus Chapa

"Experiments in conjunction with finite element analysis (FEA) are used to better predict crack propagation in ductile/brittle graded composites. Cu/W graded composites were fabricated by stacking discrete layers of powders and hot pressing. Crack propagation was studied by loading a notched beam in four point bending and examining the subsequent crack deflection. The notch was placed within a particular composition of material, oriented in a direction perpendicular to the gradient direction. Elastic and plastic mismatch between different constituents in the graded composite induce shifts in the phase angle of loading, thereby causing the crack to deflect. FEA indicates that thermal residual stress has a negligible ""influence on the crack path. The combined FEA and experimental results suggest that elastic mismatch is the single most important material property-related factor in controlling crack deflection.IntroductionMany 'applications would benefit or may even require materials whose performance or functionality must vary spatially. While the concept of functionally graded materials has existed for nearly one hundred years, it is only within the last fifteen years, that research efforts have focused on generic issues in processing, properties and performance of functionally graded materials. This generic research effort has brought together scientists and engineers from traditionally different disciplines to address common issues with graded composites. The current work focuses on issues in structural joining. A wide variety of applications require some type of joining between dissimilar materials. Examples include thermal barrier coatings for turbine engines, wear resistant coatings for tools, ceramic engine parts, and microeiectronic devices, as well as many traditional applications involving metallic welding. The joints may either be discrete, involving a single interface, or they may· be spatially graded in composition. Extensive theoretical and experimental information exists on discrete bimaterial and trimaterial joints, but relatively little exists for graded joints or composites"

Jan 1, 2000

By Nickolas J. Themelis

Nearly thirty two million tons of municipal solid wastes (MSW) are combusted annually in over one hundred U.S. Waste-to-Energy (WTE) power plants, thus reducing the use of fuel oil by about 1.6 billion gallons of fuel oil One of the advanced WTE processes is the 0.9-million ton/y SEMASS facility at Rochester, Mass. Most of the combustion in the three giant combustion chambers occurs while the injected shredded wastes are in suspension, i.e., in flash combustion mode. The velocity, temperature, and concentration profiles in the SEMASS combustion chamber were simulated by representing the combustible fraction of MSW by the simplified formula C6HIO04 and using the CFD program Fluent to solve the turbulent energy and mass transport equations. After validation against plant data, this model will be used to examine options for increasing the productivity of WTE combustion chambers, such as optimum distribution of primary and secondary air and oxygen enrichment.

Jan 1, 2003

By B. Erik Ydstie, Dimitrios I. Gerogiorgis, Sridhar S. Seetharaman

"Carbothermic production of aluminium is an important alternative to electrolytic processes and has in fact been identified several decades ago as a potentially feasible and profitable process. The cornerstone principle is to take advantage of the endothermic reduction reaction between carbon and alumina instead of resorting to extreme amounts of electric energy to ionize and reduce aluminium oxide to aluminium. Electric energy is necessary only for heating purposes.The present study focuses on constructing and solving a steady-state electrothermic model for obtaining the spatial distributions for electric potential, electric field intensity and temperature. The complex issues of reaction kinetics and multiphase flow are handled by an approximation and are not addressed at the present stage, due to the lack of complete validated models. Because of its inherent complexity, the reaction slag is considered a pseudohomogeneous layer.An electrothermic simulation encompasses important research challenges, due to the limited knowledge of thermophysical properties for high-temperature multi component molten slags. Therefore, thermophysical property modeling and a systematic compilation of published data is a necessary and major first step towards enhancing understanding of the process fundamentals. Models are obtained by analyzing measurement data from numerous literature references for the density, viscosity, thermal and electrical conductivity and specific heat capacity of the slag.The electric potential, field intensity and temperature distributions obtained reveal interesting maxima which indicate localized superheating and lead to important engineering conclusions. The temperature profile calculated will serve as the foundation for the flow problem solution. This computational study will form a basis for future research towards combining the scopes of microscale CFD modeling and mesoscale process modeling into a unified modeling approach."

Jan 1, 2001

By Hiroyuki Matsuura

The effects of P20S or Na20 addition on the reaction rate of CO2 dissociation on the surface of FexO-base molten oxides was investigated at 1773K by isotope exchange methodl-6_ The rate constant decreased with increasing P20S content of molten oxides and the residual rate constant was observed at high P20S content On the other hand, the rate constant increased with increasing Na2O content for FexO-SiO2 melts. The rate constant was evaluated by the composition of oxides and the rate controlling step of CO2 dissociation was discussed.

Jan 1, 2003

By Jim A. King

The total pressure oxidation of copper concentrates is a potentially viable option for treating copper concentrates that are either low grade or contain significant impurities. Both concentrate types are heavily penalized in smelter contracts. The total pressure oxidation process involves autoclaving the copper concentrate at temperatures of 200-220 C under oxygen pressure. The autoclave discharge can be separated into a solid (oxidation residue) and a liquid (oxidation solution) product. The oxidation solution can be treated for copper recovery by solvent extraction - electrowinning or by direct electrowinning. The direct electrowinning recovery of copper requires prior removal of selenium and tellurium by cementation on finely divided scrap copper. The oxidation residue is washed thoroughly to remove acid and dissolved copper prior to precious metals recovery by conventional cyanidation in the presence of lime. The results of a benchscale investigation involving a number of copper concentrates are reported. Copper recoveries in autoclave oxidation and gold recoveries by cyanidation of the oxidation residue exceeded 99%. The results of benchscale experiments to demonstrate copper recovery are described. Various flowsheet options are presented.

Jan 1, 1993

By A. Navarra

Peirce-Smith converting (PSC) is applied for roughly 50% of primary nickel and 70% of primary copper production. PSC cycles produce batches of ironfree sulfide matte (or blister copper, in the case of copper smelters), that are subject to further processing. However, the number of cycles that can be performed simultaneously is limited by the offgas handling system. Moreover, PSC suffers from variation in the yield and duration of the cycles. This variation is managed by conventional smelter designs, in which the upstream smelting capacity exceeds the nominal converting capacity; PSC is thus a major bottleneck in conventional nickel and copper smelters. Stabilization and standardization of PSC operations can therefore increase smelter throughput. The current paper presents a discrete event simulation (DES) framework to assist in smelter debottlenecking. It features random number generation to represent cycle variability, and time-adaptive finite differences to represent thermochemical complexity. Preliminary computations are presented.

By Jae-Ho. Lee

For some electronic applications where a dispersed electrically-conductive particulate-phase is employed, the conductivity of the surface (or near-surface region) of the particles provides for the primary mechanism which determines its electrical conductivity. Particles of a less expensive material, which may have desirable thermal-expansion properties, when coated with silver offer a means of also obtaining desirable electrical properties and at low cost. The research conducted was focused primarily on the development of silver-coated tungsten particles for thick-film polymeric conductors. The ammoniacal electrolyte was formulated from silver-nitrate, glycine inhibitor and formaldehyde reductant. The reduction, and subsequent deposition, of silver occurred selectively on the surface of the tungsten particles. Coated particles were assessed by SEM imaging. The thickness of the silver coating was estimated to be approximately 100nm on the basis of a mass account and the coating being uniform. The electrical conductivity of a silver-coated tungsten-powder pellet was found to be similar to that of a silver-powder pellet, of identical geometry.

Jan 1, 1997

By G. A. Bala

As part of ongoing research to define mechanisms of microbial enhanced oil recovery (MEOR), this work describes the activity of Bacillus l1chen1formis JF-2 (ATCC 39307) Mosurfactant against crude oils with varying compositions. Surfactant based MEOR improves oil recovery by lowering the oil/brine interfactal tension (IFT) therefore permitting oil to be displaced or solub1lized into the aqueous phase.? MEOR is an Enhanced Oil Recovery (EOR) process which allows for the introduction of chemical and miscible fluids, in the form of microbial metabolic end-products, through the injection of microorganisms into the reservoir or stimulation of indigenous reservoir microbial populations. These microorganisms represent a replenishable in situ source of acid, gas, biopolymer, solvent, or surfactant products which can be. supported and manipulated by the addition of simple and inexpensive nutrients to enhance the recovery of oil. Microbially mediated surfactant production represents one mechanism of MEOR. Bacillus licheniformis JF-2. has been used in a mode 1 MEOR system based on Berea sandstone cores (permeabilly .85 to 400 md) to examine surfactant based MEOR of medium to heavy crude oils (API gravity 38.1° to 17.5°). Enhanced oil recovery was achieved with all oils tested using either cell free culture supernatants or microbial suspensions as injectants with no detrimental effect to the oil. Spatial distribution of cells following mf?crobtal flooding was analyzed with scanning electron microscopy. Data indkate complete distribution of cells with a predominance of organisms located distal to the point of injection. There appears to be no sign:if1cant recovery trend with respect to oil composition.. The biosurfactant produced by Bacillus lichen1form1s JF-2 lowers the interfacial tension of all oils tested equally well.

Jan 1, 1991

By Dalene Joalet Steenkamp

Excavation of industrial-scale furnaces allows for the systematic study of reaction sequences by identifying the different reaction zones within the furnace. In 2013, Transalloys excavated a 48 MVA submerged arc furnace that was used for silicomanganese production using the ore-based route. The excavation method was reported elsewhere as was observations made in terms of refractory wear and modes of electrical energy dissipation prior to excavation. The paper presented here, reports on the process reaction zones observed during the excavation and subsequent phase chemical analyses of a number of process samples obtained during the excavation. The zones identified were a loose burden zone, a dry coke-bed zone, a wet coke-bed zone, a hard build-up zone, and an alloy zone. The results are compared to observations made in the excavation of an industrial-scale SAF and a pilot-scale SAF in Norway. The presence of the hard build-up zone below one of the electrodes and absence of a slag zone below all three electrodes are unique features of the SAF excavated at Transalloys.

By K. D. Peaslee, V. L. Richards, C. H. Rawlins, S. N. Lekakh

"Steel-making processes generate carbon dioxide air emissions and a slag co-product. The aim of this project was to develop a functional sequestration system using steelmaking slag to permanently capture carbon dioxide emitted in steelmaking offgas. A possible parallel benefit of this process would be rapid chemical stabilization of the slag minerals with reducing swelling or leaching.This paper summarizes the original results of the project, including mineralogical and structural features of carbon sequestration with steel making slag, mathematical modeling of reaction phenomena using a modified shrinking core model, METSIM modeling of several possible industrial applications, a thermo-gravimetrical study of the reaction between slags and different gases, and design and testing for a lab scale apparatus consisted of two reactors.1. IntroductionThe U.S. produces 9-14 Mt of steelmaking slag annually, which represents approximately 10-15 wt. % of crude steel output.1,2 Primary uses for steelmaking slag include high quality mineral aggregate, Portland cement, unconfined fill, soil conditioning, and pH neutralization of abandoned mine drainage.3,4 The key factor prescribing slag use is the alkaline-earth metal (e.g. Ca and Mg) oxides content, which contribute to overall basicity and cementitious strength. However, as-produced steelmaking slag is chemically unstable. Calcium and magnesium oxides readily form hydroxides and carbonates through reaction with atmospheric gases. Both hydroxide and carbonate formation produce substantial mechanical swelling leading to heave failure in confined construction applications, thus many states dictate stockpile aging for 3-6 months prior to commercial use.5,6 Sequestration of carbon dioxide is a natural corollary to forced carbonation. The conversion of CaO/MgO to carbonates serves both to stabilize the slag, and permanently capture and store the CO2."

Jan 1, 2008