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"EAF dust is categorized as a hazardous solid waste. EPA approves only two treatment methods: either sending the dust to zinc recycling facility, or stabilizing it first and then disposing it to a specially-lined landfill. Both treatment methods are costly to EAF steelmakers. In order to reduce the cost and even better to make profit from the dust, EAF steelmakers need to find a costeffective technology to separate zinc from EAF dust. This paper is dedicated to discussion of a novel recycling strategy: in-process separation of zinc from EAF dust. The concept of in-process separation of zinc from EAF dust is first defined, and then a simple Zn concentration model is developed. From this model, two approaches of in-process separation of zinc from EAF dust are derived: (1) prematurely capturing dust at very high temperature when zinc is still in vapor status, (2) prematurely collecting dust immediately after quickly cooling EAF off-gas from high temperature to low temperature. Next, thermodynamic analysis is conducted to understand zinc behavior in EAF off-gas. It is demonstrated in theory that zinc is in vapor status while it exits from electric arc furnaces. At last, recycling routes and economics of in-process separation of zinc from EAF dust are discussed.IntroductionElectric arc furnace (EAF) plays an increasingly important role in steel production. According to USGS, steel production from electric arc furnaces has long exceeded that from basic oxygen furnaces [JJ. In 2009, electric arc furnaces produced 64% of total steel in the United States.Along with the fast growth of EAF steel production, generation of EAF dust is also rapidly increasing. A survey by AIM Market Research showed that 10 - 20 kg EAF dust was generated for every ton of EAF steel produced [2] In 1999, the United States alone produced 770,000 metric tons of EAF dust [3] In Europe, annual generation rate of EAF dust is more than one million tons [4-5]. In Japan, about 450,000 tons of EAF dust is produced each year [6] Globally, total generation of EAF dust was estimated to be more than 5 million tons per year [5] EAF dust is categorized as a hazardous solid waste since it often contains heavy metals, such as lead, chromium and cadmium. US Environmental Protection Agency (EPA) approves only two methods for treating EAF dust: (1) recycling the dust by EAF-dust recyclers, and (2) specially landfilling the dust for disposal after it is chemically stabilized. These two methods of treating EAF dust are both very costly to EAF steelmakers. It was estimated that a fee of $150 to $200 per ton of EAF dust was paid for various treatment options, which added approximately $2 - 3 cost for every ton of liquid steel produced by electric arc furnaces [?J."

Jan 1, 2011

By C. J. Beyke

In recent years recycling of household batteries has received increasing attention, primarily for environmental reasons. This article reviews the major battery types and some of the technologies available to recycle them. It also discusses issues such as collection and sorting which are related to battery recycling in the United States. Finally, results from research being conducted by the U.S. Bureau of Mines on the reclamation of nickel-metal hydride, alkaline, and zinc-carbon batteries are presented.

Jan 1, 1995

By Zemin Ma

A novel chromate [Cr(VI)] reducing bacterium was isolated from chromite ore processing residue disposal site of China and identified as a Leucobacter sp. by 16S rRNA gene sequence homology. The minimum inhibitory concentration of strain CRB1 was 820 mg l-1 of Cr(VI). The reduction of Cr(VI) occurred only under aerobic conditions. With an initial concentration of 2.5×108 cells ml-1, 1800 mg l-1 of Cr(VI) was reduced entirely within 38 h under the optimum conditions, at 30 °C and pH 9.0. Increasing Cr(VI) concentrations prolonged reduction process and higher cell densities meant quicker reduction. A blue precipitate was produced during chromate reduction of strain CRB1, which was binding to the surface of bacterial cells and determined as trivalent chromium with electron paramagnetic resonance (EPR) spectrometry. The conspicuous chromate reduction ability of Leucobacter sp. CRB1 suggested a potential for bioremediation of Cr(VI) containing wastes.

Jan 1, 2008

By F. F. Aplan, G. Simkovich

"A review is given of the effects of solid state point imperfections upon a number of mineral benefication processes and a metal extraction process. It has been found in numerous flotation studies that small amounts of aliovalent impurities (dopants) in binary compounds may show major effects upon flotation behavior. Both semiconducting and ionic conducting compounds are affected. These effects are also seen in hydrometallurgical studies as well as in electrostatic operations. Additionally, de-copperization of lead melts appears to be strongly influenced by similar defects. It is hypothesized that the effects observed in these studies are present in actual operations and should be considered in designing processes. A few speculations concerning future efforts are advanced. IntroductionImperfections [point (e.g., vacancies, interstials, quasi-free electrons, electron holes, impurity ions), line (e.g., dislocations), two dimensional (e.g., grain boundaries) and three dimensional (e.g., 2nd phases) defects] are generally present in solid materials and these imperfections may, and often do, have important effects upon a variety of properties and processes. In general, one may, in most cases, attain elimination of three dimensional defects by a separation process of one type or another (e.g., gravity, electrostatic, magnetic, flotation, hydrometallurgical etc.,). Thus, this type of defect has rarely been investigated in a systematic fashion. Two dimensional defects are always present in non-single crystal materials but have also escaped systematic studies in processes primarily because the control of such defects is not easily attained. Line defects are non-equilibrium entities which are present in ill-defined quantities so that they present a variable that cannot be easily controlled although through careful systematic experiments one can attain some reproducible relations pertaining to this type of defect.Contrary to the lack of studies concerned with the effects of 1, 2 and 3 dimensional types of defects there has been some activity concerned with point defects and their effects upon a number of mineral/metallurgical processes, especially flotation processes. Thus, this article will present a review primarily of point defects in relation to their effects upon flotation although other processes and defects will also be mentioned."

Jan 1, 1988

By C. Burton Clark

The important role of the petrographic microscope in the petrology of refractories is discussed, based on 45 years of industrial experience by the author. Highlights of his career are used to illustrate improvements in equipment and techniques during the period. Two specific investigations are described which emphasize the interrelated use of the petrographic microscope with other instruments such as the x-ray diffractometer and scanning electron microscope. Emphasis is placed on the use of phase equilibrium diagrams for guidance in predicting and interpreting reactions that occur under non-equilibrium conditions in the manufacture and use of refractories.

Jan 1, 1982

By Patrick R. Taylor

Ilmenite concentrate and methane are fed to a non-transferred arc thermal plasma reactor to produce a powder that is primarily TiC and Fe. This material has promising characteristics for powder metallurgy applications. Free energy minimization plots were used to predict the feasibility of the reaction. An estimate of the optimum molar ratio between the ilmenite concentrate and methane was made based on the mineral composition. Argon-helium mixtures were used as plasma gases. The effects of power input level, carrier gas flow rate, powder feeding rate, and methane-ilmenite molar ratio were studied and the behavior of the system characterized. Two different powder injection angles were tried. A mathematical model to describe the temperature profiles in the reactor was formulated and solved. The product has been characterized by x-ray diffraction and atomic absorption. A conversion of 97 % of Ti to TiC was achieved. It was found that minor amounts of titanium oxides, iron carbide and free carbon are also present. TEM and SEM were used to study the morphology.

Jan 1, 1996

By Robert Mensah-Biney

The loading characteristics of gold-tetrabromide species onto a weak-base resin, PAZ-4, were evaluated using a completely mixed batch reaction system. The time. to attain equilibrium loading was substantial, on the order of several days. However, abnormally high loading capacity values of 15 to 20 meq Au/g dry resin (1000 to 1300 kgAu/tonne) were attainable in 24 hours. The loading of gold-bromo species by P AZ-4 was visualized as consisting of two processes: (i) the rapid adsorption of [AuBr4r species by simple ion exchange mechanisms and (ii) reduction of [AuBr4r to metallic gold by an electron exchange mechanism. Elution of gold from loaded resin was feasible provided the resin had not been loaded to high capacity values. If loading is carried to high levels, complete elution becomes impractical and the gold may be recovered by ashing the loaded resin. For the high loading capacities observed this option would appear to be cost effective.

Jan 1, 1991

By Bora Derin

The partial pressure ratios of sulfur and oxygen for several copper flash smelting plants were derived using the Reddy-Blander (RB) model and predicted dissolved sulfur contents available in the literature. The sulfide capacities (Cs) of six different flash smelting plants (FeO-CuOo.5- CaO-MgO-FeOu-AlO15-SiO2) slags were calculated. The log (PO2/PS2) versus matte grades of various industrial processes was determined. The PO2/PS2 ratio increased with an increase of copper grade. The calculated partial pressure ratios for the copper flash smelting are in good agreement with those of the experimental data.

Jan 1, 2003

By D. K. Panda

The behavior of single drops with gas evolution at the interface is of interest because this is one of the important reactions that occur in oxygen steelmaking vessels, where a large amount of iron-carbon drops are dispersed in an oxidizing slag. The carbon dissolved in these drops, reacts with the slag to form CO, which is evolved as a gaseous phase. A room- temperature model was used to study the nature of this type of reaction including the effect of various factors such as viscosity and the presence of surface active impurities. Experiments were done for reacting drops over a wide size range to observe various regimes of behavior. Large single drops were levitated in a counter current flow to produce a sufficiently long residence time to allow the study of the various stages in the reaction. The emphasis of this work was to obtain photographic evidence of a high quality to describe all possible modes of behavior, and so a lot of effort was given to developing and perfecting experimental techniques.

Jan 1, 1994

By L. A. Harris

In the present study the open gradient magnetic separation' (OGMS) method has been used to beneficiate the -30 + 100 mesh fraction of two high volatile bituminous coals. The evaluation of the effectiveness of the magnetic separation for cleaning these coals is the subject of this paper. Coal petrography in combination with scanning electron microscopy (SEM) and x-ray diffractometry (XRD) were used to characterize the magnetically separated coal fractions. These analyses revealed that the majority of the pyrite and non-pyrite minerals were concentrated in the positive magnetic susceptibility fractions. The bulk of the starting samples (-80 weight percent) were located in the negative magnetic susceptibility fractions and showed significant reductions in pyrite and non-pyritic minerals. The magnetic separation appears to effectively split the samples into relatively clean coal and refuse.

Jan 1, 1981

By Jong-Ren Tarng, Gin-Hwa Chen, Wen-ku Chang, Ke-Ming Lin, Yuan-Haun Lee

"The majority of early studies used X-ray diffraction, but this requires a model to interpret the diffraction processes. A turbostratic model has been applied by Warren, Franklin and Bacon to a wide range of materials including both soft and hard carbons. Maire and Mering applied the same methods to the interpretation of the (001) lines of a series of graphitic carbons. In our case, graphitic carbons undergone high temperature and high pressure graphitization processes have been evaluated by the same methods. It were found that most technological XRD data were obtained by a Rietveld method with the least-squares refinements could be in the simplest way since the full correction technique is very laborious. The behavior of carbon materials as it proceeds through the graphitization process is characterized by changes in the measured interlayer spacings (d) a~ a function of temperature. A series of graphitic carbons including the transformation of diamond to graphite through the process under high temperature and high pressure have been evaluated. A simple calibration equation has been established. IntroductionRecently, in battery industry, carbon materials are used as cathode in lithium ion batteries. However, graphitization of those carbon materials is concerned as if lithium ion intercalated into those carbon cathode. Both high-graphitization and low-graphitization carbon materials are suitable for this kind of application.As for graphitization, the starling materials from which carbons may be prepared vary extensively from pure chemical compounds, to mixtures containing II wide range of molecular weights, such as pitches. So its graphitizing, perhaps the most notable feature of the process, is the very wide range of temperature over which the perfection increase, unlike the more common transformations of solid state materials which occur in a narrow temperature range. The variables involved in the conversion of the initial hydrocarbon to a carbon residue, which may vary widely in final perfection, are time, temperature, stress and impurity content"

Jan 1, 1996

By Andrew Case

The Port Nickel facility in Braithwaite, Louisiana, is known for pioneering hydrometallurgical processes for the 'separation and recovery of nickel, cobalt and copper. Ten years ago, in 1985, a new CRI-MET process for the recovery of molybdenum, vanadium, nickel, cobalt and alumina from spent catalysts was developed and implemented. Spent- catalysts from the petroleum industry consietute the majority of feed. These are not only a valuable-source of metals, but due to EPA regulations are frequently classified as hazardous under RCRA. Molybdenum and vanadium are selectively leached in an oxidative hydrothermal step. Alumina is then extracted in a caustic digestive leach. The unique technology produces four primary commercial products l molybdenum trioxide, vanadium oxide, aluminum trihydrate and nickel-cobalt concentrate. This paper discusses the process, modifications. during ten years of operation, and the relationship of these modifications to the future of the catalyst recycling business.

Jan 1, 1995

By J. Brent Hiskey

Recently basic concepts of semiconductor electrochemistry and solid-state electronic structure theory have been applied to the dissolution of mineral electrodes. In this paper, fundamental aspects of semiconductor electro- chemistry and interfacial charge-transfer processes are reviewed. Information regarding the electronic and semiconductor properties of chalcopyrite is summarized. The electrochemical response of chalcopyrite in acidic solution is analyzed in terms of initial dissolution processes. The initial charge- transfer reaction involves the consumption of holes. It has been shorn that Fermi level pinning is consistent with observed electrochemical and dissolution behavior. Semiconductor electrochemistry has proved helpful in explaining the formation of intermediate surface films produced during the initial stages of chalcopyrite dissolution

Jan 1, 1993

By J. L. Jambor, H. W. Nesbitt

Oxidative dissolution of pyrrhotite and pyrite is largely responsible for the sulfate-rich waters of the vadose zone in the Waite Amulet tailings. Although the shallowest of the sulfate-rich waters are of the Fe-SO4 type, they change to Mg-SO4-type, near-neutral waters within 1-2 m of the tailings surface. Phyllosilicates and amphiboles are the only minerals present in sufficient quantity to ameliorate the amount of acidity produced. X-ray diffraction and microscopic studies of bulk sample indicate that quartz, chlorite, talc, amphiboles, magnetite, albite, and micas are the major and minor non-sulfide minerals, but their variations with depth do not give clear indications of depletion in the vadose zone. Mineralogical and bulk chemical compositions of the tailings confirm that Fe2O 3 has accumulated in large quantity in the vadose zone, with the Fe having been derived from Fe sulfides. When the effect of Fe2O3 is accounted for, the bulk compositions suggest that SiO2 is slightly more abundant in the vadose zone than in the saturated zone. This may be the result of residual enrichment of siliceous minerals such as quartz and albite in the vadose zone. Weathering of the tailings since the cessation of deposition in 1962 has resulted in a well-defined zone of sulfide depletion and secondary sulfate-mineral development. Although some silicate dissolution is indicated by pore-water compositions, the role of silicates in providing neutralization seems to have been minimal. The contribution by silicate minerals in laboratory tests of neutralization potential may be excessive relative to that in natural settings.

Jan 1, 1999

By Michaela Dina Stanescu, Emilia Visileanu, Eftalea Carpus

"The recovery and reintroduction into the economic circuit of the textile material resources must be considered as component parts of the strategies of harmonizing the relationships between the economic growth, consumption of natural resources and environmental protection of the existing socio-economic system.The waste recovery for ensuring a sustainable development is a major concern of all industrial researches. In the textile domain, the concern in this matter is becoming more evident. An important role in manufacturing textile products it has the notion of eco-design, which has grown considerably over the last twenty years with increasing awareness of environmental and social problems in the industry.Introduction“Humanity must learn from the global financial and economic crisis experience""- is the conclusion of the policy makers who should develop a strategy designed to reinvigorate the economy and make possible an"" intelligent, sustainable and favourable to inclusion” growth, by a better coordination of national and European policies.The new vision for social market economy is based on three priority areas: smart economic growth, the development of an economy based on knowledge and innovation; sustainable economic growth, the promotion of a competitive economy with low carbon emissions and an efficient use of resources, as well as an inclusive economic growth, the promotion of an economy with high degree labour employment, which would generate social cohesion. The recovery and reintroduction into the economic circuit of the textile material resources must be considered as component parts of the strategies of harmonizing the relationships between the economic growth, consumption of natural resources and environmental protection of the existing socio-economic system.The waste recovery for ensuring a sustainable development is a major concern of all industrial researches. In the textile domain, the concern in this matter is becoming more evident. It is obvious that at the origin of pollution there are the technological processes of textile processing with impact on air, water, soil, as well as the storage processes. In all phases of obtaining a product, a series of secondary products and textile wastes with impact on the environment occur. The product used becomes also a factor of environmental pollution, which in most cases fails to assimilate."

Jan 1, 2012

By S. J. Buckler

Many chemical and metallurgical processes use submerged gas injection to increase contact area between gas and liquid phases in order to promote faster overall reaction or refining rates. The total interfacial area produced by gas injection through lances, nozzles or tuyeres is both an important design parameter for new vessels and a measurement for estimating the maximum processing capacity of existing equipment. Estimating total interfacial area from submerged injection into industrial pyrometallurgical vessels from existing knowledge is a problem with two aspects. The first difficulty is the difference in behaviour of cold (aqueous) and hot (molten metal) systems, implying that existing models and correlations of gas-liquid behaviour developed in low temperature systems are not necessarily appropriate for estimation of high temperature behaviour. The second difficulty is the issue of scale-up of correlations from laboratory to industrial sized vessels. The work presented in this paper is part of an ongoing experimental investigation, at the GK Williams CRC for Extractive Metallurgy, to quantify the total gas-liquid interfacial area available in pyrometallurgical vessels using chemical measurement methods. The effects of three operating variables, injected gas flow rate, nozzle diameter and nozzle submergence, on total interfacial area are quantified in a IOOL aqueous system - the first stage of a three stage process in examining the implications for scale-up of high temperature, medium-scale results are discussed. The results of work at high, injected gas flow rates (up to 500/min) show that the submerged Froude number is not sufficient for use as the sole variable in a predictive model of total interfacial area. Further work is being undertaken to identify other dimensionless variables that will better represent the gas-liquid characteristics in submerged injection that influence the formation of total interfacial area. The second and third stages of the experimental investigation involve measuring the total interfacial area in a large-scale (1000L) aqueous sodium sulphite and small-medium scale molten metal baths.

Jan 1, 2002

By V. D. Tathavadkar

Chromite ore is of immense importance for the extraction of metallic chromium and chromium chemicals. The mineralogy and crystal structure of chromite phase are therefore important part of our investigation on the extraction chemistry of chromium species. In this investigation, we have studied the effect of the processing parameters, i.e., the temperature and the oxygen potential on the microstructure and composition of mineral phases formed in the Cr2O3 ?Al2O3 -FexOy -MgO system. In particular the importance of the spinodal decomposition reaction is emphasized in the extraction of chromium as sodium chromite and sodium chromate. Experiments were carried out in order to study the differences in the crystallography of different chromite minerals. Phase equilibria in natural chromite minerals were investigated by calcining chromite mineral in air, argon, and 5% hydrogen + argon atmospheres over a temperature range from 200 to 1200 °C. The effect of the oxygen partial pressure and temperature on the phase constituents of the calcined product has been discussed. The microstructural changes were examined using scanning electron microscope (SEM) and the changes in elemental composition in different phases were analysed by electron probe micro analyser (EPMA). The results obtained from EPMA studies were used to calculate lattice parameter of the spinel lattice, and these values were compared with the values obtained from X-Ray powder diffraction data. On the basis of the experimental data, the mechanism of the spinodal decomposition of complex spinel phases is described under the influence of oxygen partial pressure and temperature.

Jan 1, 2000

By L. A. Harris

The formation of coke during coal liquefaction can eventually result in catastrophic failure of the conversion system. Coking typically proceeds by the formation of liquid crystals (mesophase) and the subsequent separation of these crystals from the plastic phase formed during heating of coal. The anisotropy of the mesophase makes it readily detectable in the optical microscope under polarized light. This study examines the solids formed during coal liquefaction processing by optical and electron microscopy. Observations on the relationships between the coke morphology, minerals and inert macerals are presented.

Jan 1, 1982

By Sabine Knott

The thermodynamic properties of four liquid ternary zinc alloys, Au-Sn-Zn, Ag-Sn-Zn, AI-Sn- Zn and Cu-In-Zn were measured with an electromotive force (emf) method at three or four cross-sections with an constant X:Sn or Cu-In ratio. At the Au-Sn-Zn and AI-Sn-Zn system calorimetric measurements were also carried out in order to compare the integral enthalpy of mixing from the direct measurements with the data of the emf measurements, which were derived by Gibbs-Duhem integration.

Jan 1, 2003

By Sabine Knoll

The thermodynamic properties of four liquid ternary zinc alloys, Au-Sn-Zn, Ag-Sn-Zn, AI-Sn Zn and Cu-In-Zn were measured with an electromotive force (emf) method at three or four cross-sections with an constant X:Sn or Cu-In ratio. At the Au-Sn-Zn and AI-Sn-Zn system calorimetric measurements were also carried out in order to compare the integral enthalpy of mixing from the direct measurements with the data of the emf measurements, which were derived by Gibbs-Duhem integration.

Jan 1, 2003