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By John Anawati

Bauxite residue is an environmentally unfriendly byproduct of alumina manufacturing, produced worldwide in large quantities. This material contains 50– 100 ppm of scandium, a critical material for the production of stronger, weldable, corrosion resistant, and heat tolerant aluminum products. Aircraft manufacturers are particularly interested in Al–Sc alloys because of its ability to form weldable alloys that could potentially reduce aircraft weight by 15–20%. Because of its abundance and low cost, bauxite residue has the potential to be used as an efficient feedstock for valorization processes to recover its scandium content, while in turn degrading this problematic waste. In this project, we developed an efficient process to recover scandium and rare earth elements from a Canadian bauxite residue with high extraction yields, using industrially scalable and economical techniques. The process employs a modified version of sulfuric acid leaching and subsequent impurity removal by selective precipitation. This article outlines the current progress and design rationale in the development and optimization of this innovative and sustainable recovery process.

By Akira Yazawa, Kazuo Koike, Mitsuhisa Hino

"The vapor pressures of MS (PbS, SnS and Sb2S3) in the molten Cu2S-MS, FeS-MS pseudo-binary and Cu2S-FeS-MS ternary systems were measured by means of a transportation method in the temperature range of 1323 and 1423K to calculate MS activities in the sulfide melts. The activities of MS in these systems show negative deviation from ideal behavior except the FeS binary systems which exhibit nearly ideal behavior in the homogeneous melts. The activities of the Cu2S-FeS pseudobinary system, which is fundamentals of the copper matte, were estimated from the activity values in the ternary systems and exhibit negative deviation from ideality.The distribution behavior of tin between the ·matte and silica saturated fayalite slag was investigated under the controlled partial pressures of S02 at l 523K. It was found that, in general, tin is distributed in the both phase, while tin is concentrated to the slag phase with increasing copper content in the matte. The activity coefficient of SnO in the slag was calculated based on the distribution ratio combined with the activity coefficient in the Cu2S-FeS system.IntroductionThe thermodynamic properties related to the Cu2S-FeS system and the Cu2S-FeS-MS systems (where MS can be PbS, SnS, Sb2S3, As2S3, Bi2S3, etc.) is required to be better understanding of the copper smelting process. However, thermodynamic analysis such as the distribution of impurities among the gas, slag and matte phases is difficult due to lack of thermodynamic data. In this study, the vapor pressures of MS (PbS, SnS and Sb2S3) in the Cu2S-MS, FeS-MS. and Cu2S-FeS-MS systems were measured by a transportation method. The distribution behavior of tin between the matte and silica saturated fayalite slag was also investigated. The results in the present experiments are useful to analyze thermodynamically the behavior of component in the copper matte smelting."

Jan 1, 2000

By F. Field, R. Kirchain, J. Gregory

Utilizing alternative materials is an important tactic to improve the environmental performanceof products. Currently a growing array of materials candidates confronts today’s product designer. While life-cycle assessment (LCA) methods provide quantitative input into this selection decision, their implementations are evolving and disparate. The goal of this paper is to explore several major analytical variations of LCA implementations and the implications of these variants across a range of application contexts. Specifically, this paper examines analytical variations in valuation method and treatment of recycling by exploring allocation methods that affect product end-of-life. Case studies across a range of materials are presented, including materials that exhibit a spectrum in variation of environmental performance and material degradation between primary and secondary applications. Preliminary results indicate that the choice of analytical method can have real impacts on individual metrics and there are sets of analytical variation over which strategic results are strongly affected.

Jan 1, 2008

By J. E. Sallee

An experimental study has been conducted on the level of arsenic contamination in samples of zinc oxide when the zinc oxide is contacted with gas mixtures containing As4O6(g). This contamination has been determined as a function of A4O6 saturation pressure, temperature, zinc oxide sample surface area, impurities, and oxygen level in the gas mixture. The results indicated a rather clean separation can be achieved between condensed zinc oxide and gaseous arsenic oxide as long as attention is given to temperature control, and the final zinc oxide surface area. For a 300°C operation temperature and an AqOg saturation pressure of 0.38 TORR (or 0.05% As406 by volume), the contamination level is expected to be approximately 100 ppm. This suggests that arsenical dusts can be treated in the HRD flame reactor process and a reasonable purity zinc oxideproduct produced. The results also show no evidence of zinc arsenite or zinc arsenate formation.

Jan 1, 1994

By Fathi Habashi

Solid gas reactions of metallurgical importance can be classified into three groups: Physical processes, e.g., drying and sublimation Chemical processes which may be an addition or a thermal decomposition reaction Electrochemical processes which may be addition, oxidation-reduction, or displacement reactions. Examples are given and the role of the boundary layer is emphasized.

Jan 1, 1996

By Derek J. Fray

The need for on-line sensors is outlined and it is demonstrated that the control of many processes is prevented by the availability of these devices. The use of solid electrolytes is described for the sensing of elements in molten pyrometallurgical phases. In the cases where there is no suitable electrolyte, the addition of a second phase of a compound containing both the element to be measured and the element whose ion is mobile in the electrolyte can be used. For the measurement of high concentrations of an element a method based on current measurement is proposed.

Jan 1, 1994

BHP Hartley Platinum operates an electric smelting furnace to treat Cu-Ni-PGM concentrate at its plant in Selous, Zimbabwe. The furnace, originally built by others, has experienced problems including severe refractory erosion of the sidewall. Hatch Associates has designed several important improvements to the furnace, including: ? water-cooled copper cooling elements in the slag zone ?air-cooled copper cooling fins at the metal level ?water-cooled copper tapholes ?binding system providing vertical refractory compression ?electrode seals ?new feed pipes Novel construction techniques employed on this project to reduce shutdown duration are discussed.

Jan 1, 1999

By Jean-François Domgin

This paper aims at presenting numerical results showing the impact of different parameters on the limitation of entrained slag from ladle to tundish during the ladle drainage. These parameters are process parameters, slag properties or external actuator acting directly on ladle slag behaviour. Numerical simulations based on the use of the CFD Fluent software illustrate the vortexing and non-vortexing phenomena appearing during the ladle drainage. This numerical tool validated by experimental data acquired on water model has been applied to industrial configurations. It shows that the slag properties (viscosity, surface tension?) or some modifications of parameters (slide gate opening, geometry of the ladle bottom?) have a positive effect on the slag entrainment and also on the decrease of the ladle heel. Finally, the modelling of the behaviour of an external actuator injecting some gas in the region of the nozzle reveals interesting possibility for reducing slag entrainment from ladle to tundish during the final steps of the drainage.

Jan 1, 2006

By Kwang-suk You

This paper describes the characteristics of electric arc furnace slag (EAF slag) as an aggregate of concrete along with the chemical composition, leaching concentration of heavy metals, the soundness of EAF slag and compressive strength of mortar with 20% and 50% replacements of sand. The results showed that leaching of heavy metals and soundness of EAF slag satisfied Korean environmental limit and Korean Industrial Standard for aggregates. The compressive strength of mortar increased as the replacement ratio of EAF slag for sand increased.

Jan 1, 2006

The Port Kembla Copper (PKC) copper smelting facilities were commissioned during 2000. Numerous difficulties were encountered during the commissioning such as multiple reactor tuyere line failures, absorbing acid tower refractory collapse, and Noranda Reactor and Mitsubishi Converter process control problems. These problems are described along with the actions taken to overcome them. Process development is described particularly for the Mitsubishi Converter and Acid Plant.

Jan 1, 2002

By M. D. Bishop

Loss of organic solvent extraction circuits occurs through several accepted methods. Losses are commonly attributed to entrainment of the plant organic and evaporative loss of diluent. Evaporative losses of diluent have been estimated using various models or by considering all losses over and above entrainment to be due to evaporation. Other possible loss mechanisms are discussed and data on losses during weather conditions are presented. Accurate estimation of evaporative loss is vitally important to the industry due to both cost factors and environmental concerns. Data for and description of the Diffusive Flux Model are presented as an improved-method of estimating evaporative losses:

Jan 1, 1999

Most of the world's zinc metal is produced via the roast- leach-electrowinning (RLE) process. The process is well established, but most of the sulphur in the sphalerite concentrates reports in the acid, which has to be stored and/or sold. There are significant incentives to develop a simpler process with much reduced acid generation. Ferric ion is a well known oxidant for most sulphides, in particular sphalerite, and it converts the sulphide to elemental sulphur. Based on stoichiometry, however, the amount of ferric ion needed to achieve acceptable zinc extractions is prohibitive for downstream zinc recovery from the leach solutions. The process suggested here makes use of less-than-stoichiometric ferric sulphate additions because the ferric ion is regenerated by sparging SO2/O2 mixtures. This regeneration can be effected in-situ in the leach vessel or outside the leach vessel. An example of the application of this new process is presented for a Canadian sphalerite concentrate assaying 60% Zn. The effects of temperature, ferric concentration and ferric ion regeneration are presented. Options to recover zinc from the leach solution are also briefly discussed.

Jan 1, 2000

By Ken Baxter

The Sepon Copper Project is located in Laos and has a mineable reserve of approximately 16Mt of ore grading 5% copper with minor gold and silver values. The deposit is a clay-hosted secondary copper mineral suite, predominantly chalcocitic in nature with associated pyrite. The current project design is based on the production of 60,000t/a of LME Grade A cathode by an acid leaching process followed by solvent extraction and electrowinning. Significant metallurgical testwork was conducted as part of the Definitive Feasibility Study (DFS) with process challenges identified and overcome at each phase of testing. Flowsheet configuration is geared to autogenously generating sufficient acid and ferric iron to meet gangue acid consumption and to leach the copper. The ability to maintain acid and ferric levels in the process liquors is strongly influenced by the proportion of pyrite in the ore presented to the autoclave. This paper will outline flowsheet development from preliminary variability testing to pilot plant and DFS design. The Sepon process solution seeks a balance between operability and capital/operating costs, and provides insights into the basic mechanisms influencing flowsheet selection for these ore types.

Jan 1, 2003

By Kaixi Jiang, Lei Zhang, Sanping Liu, Yufang Wang, Xiaoping Zou

"Molybdenite concentrates are usually treated by roasting, but low concentration SO2 pollution is a problem. Extraction of molybdenum and rhenium from molybdenite concentrates with a pressure oxidative leaching (POX) and solvent extraction (SX) process was studied. A series of POX-SX laboratory and pilot tests were carried out on the molybdenite concentrate. In the POX stage, more than 95% rhenium and 15-20% molybdenum were leached into solution. Solvent extraction recovered the rhenium and molybdenum from the POX solution. The extraction rates of Re and Mo were above 98%. The loaded organic reagent is stripped with ammonia. The stripping ratio of Mo is more than 98%. Compared to the roasting process, the total recovery of Mo increased from 93% to 97%, and Re from 60% to 90%. In the coming five years, POX-SX technology will be competitive in China.IntroductionMolybdenite is the main resource for the production of molybdenum, and about 99% of the total molybdenum was extracted from molybdenite. Rhenium is one of the important new materials in national defense, space flights, nuclear energy and electronics, because of its high melting point, high strength, plastic properties and significant creep resistance. There are no single rhenium ores in the world; rhenium mainly co-exists with molybdenum. Consequently, molybdenite is also the main resource for the extraction of rhenium."

Jan 1, 2012

By V. Madhusudhan Rao

Fly ash is a finely divide non ? combustible material obtained as a by ? product of coal combustion. It is a major by ? product of coal based thermal power stations. Until recent past it was considered as a waste and highly polluting material. However its formation can only be minimized by using suitable technology in the boilers. In recent past it is found that Fly ash has many end uses and it has proven itself to be a potential construction material. But the suitability of fly ash for various applications largely depends on the amount of unburned carbon, which is turn depends on the firing method. Fly ash samples from various power plants existing in India using a fluidized bed method and pulverized bed were analyzed and a comparison of these two firing methods was carried. This paper deals with the compositional requirements for fly ash used for the fabrication of insulating doors using AAC (Aerated Autoclave Concrete) and the methods employed to make fly ash suitable for this purpose. It also includes the latest ?U? beam technology for effective fly ash recycle. If the by products of coal combustion from power plants like fly ash as the paper stresses are utilized properly, it is not an exaggeration to say that power generation is possible with absolutely zero cost.

Jan 1, 2006

By Bruce W. Downing

MagPower has developed methods to control the detrimental formation of hydrogen that occurs in electrochemical reactions in numerous commercial applications such as the Magnesium-Air Fuel Cell, electrowinning, zinc alkaline batteries, hydrogen embrittlement, waste water/ metal recycling and coolants. The company?s approach to an alternative energy source is the development of an environmentally friendly non-toxic alternative power source that generates electricity through a combination of magnesium, oxygen and a saltwater electrolyte with MagPower?s patent pending hydrogen inhibitors. The magnesium-air technology has never reached the commercial stage due to its limiting power output caused by hydrogen generation. MagPowerhas solved this problem and has patents pending on its intellectual property; the Hydrogen Inhibitors and has developed several consumer power units for a variety of applications through licensing agreements. The company has also shown that the inhibitors have an impact on zinc electrowinning through laboratory test work where current efficiency was improved. This will significantly reduce power consumption and increase the efficiency of the electrowinning process, as well as reduce the potential acid mist hazards associated with electrowinning.

Jan 1, 2003

By D. C. Cupertino

Oxime based solvent extraction provides the user with a selective concentration process for copper prior to electrowinning. The selectivity required is largely for copper(II) over iron(III) and this is achieved by the preferential formation of the square planar copper-oxime complex in the organic phase. The copper/iron selectivity of oximes can however, be altered by modifiers or other types of oximes and may be enhanced in the presence of certain esters. Whilst the oxime based SX processes is important for operations leaching copper from laterite ores, the high selectivity will also be significant in processing streams arising from other leaching regimes which are currently under development, for example leaching of sulfide mineral ores. This paper presents some initial results using Molecular Modelling techniques to further our understanding of the nature of the copper/iron-oxime complexation processes together with some plant studies undertaken at a number of different mine sites investigating selectivity, and other properties, for some modified reagents. Some studies of the interfacial properties of the these systems are reported to explain in part the practical observations.

Jan 1, 1999

By Varadarajan Seshadri

The performance of mould fluxes in satisfying its quality requirements can have a significant effect on the efficiency of the continuous casting process and on the surface quality of the products. This performance is affected by various parameters including the characteristics of the mould fluxes, the quality of the steel being cast and the operational conditions of the caster. The extremely complex relationships involving the parameters mentioned above make it very difficult to have simple criteria for selecting mould fluxes for casting a certain grade of steel in a continuous casting machine. These difficulties led steelmakers and mould flux suppliers to select mould fluxes based mainly on plant trials. In the present work, a software to help in the analysis and development of mould fluxes for continuous casting was developed_ This software includes several models for prediction of mould flux viscosity and consumption. A mathematical model was also used to predict the heat flux through the mould flux. The proposed methodology was applied to continuous casting of crack sensitive steels_ Some of the results given by this software are presented, discussed and compared to plant data.

Jan 1, 2003

By Takahiko Okura

"It is said that the energy and resources crisis will come before long because the lifetime of known deposits of crude oil and common metals such as Pb, Zn, Cu is estimated to be less than 50 years. Establishing the sustainable society by means of resources-recycling has become an absolute necessity.The non-ferrous metals industry in Japan has been involved in the resource- recycling business for many years, along with the introduction and enforcement of various legislations to preserve the environment and natural resources. Including process-linkage during various manufacturing activities, the non-ferrous metals industry, the iron-making and cement industries are treating considerable amounts of recycled materials and wastes, in an environmentally-sound and economic manner.The Mining and Materials Processing Institute of Japan has submitted “The present and issues in Japanese non-ferrous metals and recycling industries.”The topic of the paper is to highlight the actual conditions within the resources-recycling structures and the present issues.IntroductionGlobalization has been changing the world, introducing the spike of energy and metals price. In addition, the preservation of the environment has also been strongly facing the crisis and many people have been aggrieved by both shortage and the increment in the price of the meals.In the world of metals, even though their reserves are coming depleted, the production rates are increasing, and then the industry has to enhance their productivity under stricter environmental regulations. The Japanese industry experimented the same scenario some 40 years ago, facing big pollution problems, but concurred them and enhanced the technology to overcome the more severe regulations. It will be fruitful to present the current situation in the Japanese industry for the world. The present issues are also presented."

Jan 1, 2008

By J. M. Demarthe

The recovery of minor metals from zinc concentrates is dependent on the process used for their treatment. The behaviour of gennanium and indium in pyrometallurgical processes such as the Imperial Smelting furnace or the cupola furnace is of practical importance. The .Anaconda process for the treatment of zinc leach residues is not well suited to the recovery of valuable minor metals, and new technologies must be studied. In this regard, a solvent extraction process, using Kelex 100, developed by Minenet Recherche for the recovery of gennanium from dilute sulphate leach solutions is described. Also, new hydranetallurgical techniques in chloride media can be applied to the purification and concentration of minor metals depending on the stability of their chloro-complexes and the valency of associated inpurities. A synthesis of methods is proposed to address the problems related to the recovery of valuable minor metals in the zinc industry.

Jan 1, 1990