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By Y. Huang, P. B. Prangnell

"An Al-0.1Mg alloy was firstly deformed at room temperature by ECAE to a true strain of 10, where a steady state deformation was established and further processing had little effect on grain refinement. The ECAE samples, with an average grain size of ~0.55µm, were then compressed in a channel die at 77K- 473K to various reductions. Microstructures were characterized by electron backscatter imaging and EBSD in a FEGSEM. Grain refinement to the ECAE submicron structure occurred during deformation at cryogenic temperatures of 77 – 213K, whereas coarsening took place during deformation at elevated temperatures. A steady state deformation was observed at all temperatures where a constant grain structure was developed and maintained upon further straining due to dynamic recovery. The mechanisms of dynamic recovery during steady state deformation at cryogenic temperatures are discussed.IntroductionSevere deformation processing (SDP) has been successfully used to produce submicron grain structures, and in some cases nano-scale crystallite sizes, in a wide range of alloys. However, the rate of grain refinement becomes increasingly inefficient at high strains as a steady state grain structure is approached [1-3]. Steady-state grain sizes have also been reported in other ultra-high strain deformation processes, like cryogenic ball-milling [4]. There is thus a minimum grain size achievable in a material by a given SPD process under constant deformation conditions.It is well documented that a steady state subgrain size is observed in warm deformation of metals due to dynamic recovery (e.g. [5]). In severely deformed alloys a constant grain size at ultra-high strains has similarly been attributed to dynamic recovery [1-3]. Mechanisms have been proposed, for rapid deformation induced grain growth including stress driven boundary migration and breakaway from solute pinning [2]. However, as pointed out by Humphreys et al. [2] the restoration processes are currently poorly understood, particularly at low temperatures, where the boundary migration rates required to maintain a constant grain size are orders of magnitude higher than can be satisfactory explained from diffusion controlled migration. Similar to the subgrain size, the steady state grain size obtained during SDP is generally related to the temperature compensated strain rate [2, 6]. Thermally activated restoration processes are thus expected to be suppressed by lowering the deformation temperature and a smaller steady state grain size can be achieved."

Jan 1, 2012

By Joon H. Jang

At a selected pH, hydrothermal oxidation of chalcopyrite was carried out under controlled F+,, at elevated pressures and temperatures (172-200°C) by balancing the rate of oxygen injection against the rate of consumption. Chalcopyrite was converted to covellite (CuS) and digenite (CU1.8S) with rejection of iron and sulfur to the solution. Covellite forms in the first stage, followed by nucleation and growth of digenite in the second stage. The effects of rapid and slow injection of stoichiometric quantities of oxygen are compared. Both the covellite and digenite form a porous layer occupying the same volume as the original chalcopyrite grain. An electrochemical kinetic model is presented to correlate the observed results.

Jan 1, 1993

By D. J. Droppert

This paper describes the precipitation-production of crystalline scorodite (FeAs04.2H20) from arsenic-rich sulphate-based metallurgical solutions at ambient pressure (95°C). Arsenic is precipitated by means of a controlled precipitation technique in which the supersaturation of the solution is carefully controlled. By controlling the supersaturation in the presence of seed material. the formation of amorphous ferric arsenate is prevented. Scorodite is known to be the most stable As(V) compound and is therefore preferred as host mineral for arsenic immobilization. The effect of the following parameters on the preCipitation behaviour and kinetics of scorodite are discussed: Type of base seed concentration initial [As]. sulphate concentration. neutralization rate. seed recycling and method of Fe(ll!) addition to Fe-deficient arsenic solutions.

Jan 1, 1996

By Pengcheng Li, Wei-Tong Du, Yu Wang, Gang Wen

Carbon dioxide could be utilized as a weak oxidant and a kind of coolant to oxidize elements, meanwhile, helping control the temperature during the converter vanadium extraction process. However, the optimum content of CO2 and the cooling effect of CO2 at low content have not been reported. In this study, experimental research based on the influence of different CO2 contents from 0% to 25% injected to the vanadium-containing hot metal was carried out, as well as contrast experiments of O2-N2 mixed blowing. The results indicated that the optimum content of CO2 was 15%. Under the optimum condition, the oxidation of [C] was the lowest and the oxidation rate of [V] was 96.9%, while the temperature was also lower than the O2-N2 mixed blowing. This paper provide a potential property for utilizing CO2 during the converter vanadium extraction process.

Jan 1, 2016

By Mingming Zhang, Mallikharjuna R. Bogala, Ramana G. Reddy

Steelmaking desulfurization slag samples were characterized using chemical, X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS) methods. The objective of this work is to investigate the occurrence of sulfur and phosphorus components in the slag samples and to identify their origin and associations with the iron phases. Thermodynamic calculations results confirm the presence of phosphorus and sulfur components in the slag sample at high temperatures (1400 to 1800oC). The main constituents of slag include Ca3SiO5 (28.1%), MgO (9.31%), Ca3(PO4)2 (9.18%), CaS (8.39%) and CaO (5.68%). The major phosphorus and sulfur components of the slag are Ca3PO4 (99.2%) and CaS (79.3%) respectively. Characterization studies indicate the presence of microparticles of different sizes and shapes in the slag sample. Elemental analysis of these particles confirm the presence of major elements (O, Mg, Al, Si, S, Ca and Fe) in the slag sample.

Jan 1, 2015

Segregation roasting tests were carried out on Zaire cobalt oxide ores assaying about 2% Co and 3.5 to 6.5% Cu. The major parameters tested during the laboratory investigations were temperature, dosage and type of reducing agent, dosage and type of chloridizing agent, and particle size. Results showed that standard conditions suited to the segregation of copper ores, i.e. low temperature and low dosages of reducing and chloridizing agents, resulted in the segregation of copper only, while conditions suited to the segregation of lateritic nickel, i.e. higher temperature and increased dosages of reducing and chloridizing agents, led to a successful segregation of both copper and cobalt. Under the best conditions, 88% of the cobalt and 98% of the copper could be recovered in a concentrate assaying 32.5% Cu and 8.5% Co. Alternatives to process such a concentrate are briefly reviewed.

Jan 1, 1993

By Chunyang Guan, Jilai Xue, Zengjie Wang, Qiaochu Liu

Molten salts electrolysis method to prepare Al-RE alloys has attracted increasing attention recently. CaCl2 and Na3AlF6 were the most often used melts for this purpose. In this work, Al-Sc alloys prepared by electrolytic deposition process in both CaCl2 and Na3AlF6 melts were investigated, respectively. It was found that Sc distributes almost uniformly and Sc contents increase with increasing current intensity in both melts. Current efficiency was measured for comparison among various current densities applied. The alloy products were analyzed using XRD and SEM, where the formation behaviors of Al-Sc intermetallics were investigated in details. The experimental and theoretical results demonstrate that Al3Sc and Al0.968Sc0.032 are the major precipitates in the Al-Sc alloys prepared by molten electrolysis. The results are useful for selection and optimization of the molten salts compositions and the parameters of electrolysis operation.

Jan 1, 2015

By R. H. Crist

Reactive components of algal cell walls include uronic and alginic acids: In addition, many marine species have half ester sulfate groups which function as fixed anions. Associated metals vary with the media, eg., Ca and Mg in fresh water (FV) and Na, Ca, Mg in seawater. . These metals readily exchange with aqueous phase protons or metal cations. A plot of the total amount of metal cations displaced by protons vs .. pH shows one inflection at pH 4 for FV algae and' in addition a second inflection at pH 2, 3 for marine algae. The first inflection is interpreted as. Indicating the cations associated with carboxyl groups ,and the ,second with half ester ?Sulfate groups. The exchange capacities of various aigal ,species vary widely. When FV algae is placed in a Pb2+ solution,- the amount of Pb2"' deposited on the algae is. Equivalent to the. Total Ca2?, Mg2, and H+ displaced? thereby confirming the ion exchange mechanism. Ion exchange equilibrium constants are reported for the displacement of ca2+ from Vaucheria. With Mg2+, sr2+, Cd2+, Pb2+_ and Na+ as well as the reverse reactions. Cd2+ can .be removed partially from algae by precipitating it as CdS or Cd(OH) 2 Pb2+ and Cu2+ are also partially removed as the hydroxides. Rates of reaction for various alkali hydroxides decrease with increasing .unhydrated cation radius. It is concluded that theory is useful in predicting viable applications for algae in pollution abatement.

Jan 1, 1991

By Shengli Wu, Juan Zhu, Wei Huang, Xinliang Liu, Kaiping Du, Kaifa Zhang

Based on the furnace burden of high content of Al2O3, the process of softening and melting and the characteristic of primary slag were studied with the increase of MgO content in the sinter and adding some MgO into the pellet. The results showed that the content of MgO in the primary slag increased with the increase of MgO in the sinter and pellet. Meanwhile, the permeability of the furnace burden was improved because of low viscosity of high MgO primary slag. Compared with the increase of MgO content in the sinter, the increase of MgO content in the pellet can improved the softening and melting characteristic of the comprehensive furnace burden more effectively. More Mg-bearing pellet should be chosen in the comprehensive furnace burden for the purpose of improvement the fluidity of primary slag and the permeability of the furnace burden in the burden of high Al2O3 content.

Jan 1, 2015

By R. Hurman Eric

The flow of molten slag and matte and the estimation of the mass of settled matte in electric furnaces is discussed and the action of the electric furnace as a settler is considered. Particle size of the concentrate and its grade are major contributors to settler dimensions. Discussion on the production capacity of the electric furnace with reference to operating current, power input, furnace dimensions such as width and length and electrode diameter are given. These discussions are based on considerations derived mainly from experimentally determined properties of the slag such as its resistivity, viscosity and liquidus temperature. Extension of the design and operating considerations to circular furnace symmetry is also discussed.

Jan 1, 1995

By Rolf R. von Oppenfeld

Onsite hazardous waste processors often find obtaining a Treatment Storage and Disposal (TSD) permit one of their first major challenges. Some processors may spend the time and money required by the permitting process, only to find out later that a permit was not necessary. This paper will present and analyze four strategies that processors may use to avoid obtaining a TSD permit. Some facilities will be able to remove their waste streams from RCRA's oversight by ensuring the material is not "hazardous" waste. Parties that treat waste while it is in process may be able to avoid generating "waste" altogether. Certain treatment facilities have been specifically exempted by EPA. Finally, treatment of waste while it is in generator storage tanks may be allowed without a RCRA TSD permit. Hazardous waste point of generation, an important determination relating to these strategies, will also be discussed. Generators and processors will find this paper useful when evaluating their permit exemption potential

Jan 1, 1996

By Alex Luyima, Honglan Shi, Lifeng Zhang, Yongqing Jiang

"Leaching process has been suggested to recover most metals from waste PWBs. In this study, the leaching behavior of most metals present in waste PWBs is evaluated before and thermal treatment. Different leaching acids: hydrochloric acid (HCl), nitric acid (HNO3) and aqua regia are compared. The effects of acid concentration, particle size of sample, leaching time and temperature are examined. Results revealed that most metals are present in small particle size and sequential leaching of PWBs with a combination of HCl acid and aqua regia is capable of dissolving most of the metals content of PWBs. Leaching of thermally treated PWBs produced the highest leaching percentages for similar leaching conditions.IntroductionApproximately 20–50 million tonnes of electronic waste (e-waste) is produced globally per year. Waste Electrical and Electronic Equipment (WEEE) or E-waste is one of the fastest growing waste streams in the world. In developed countries, it equals 1% of total solid waste on an average [1]. The growing stockpile of used and obsolete consumer electronics has been called the “largest toxic waste problem of the 21st century [2]. Printed wiring boards (PWBs) is an essential part of almost all WEEE, and accounts approximately 3% of all WEEE by weight [3]. PWBs are a platform upon which microelectronic components are mounted. PWBs contain metals (~40 wt. %), ceramics (~30 wt. %) and plastics (~30 wt. %) [4]. The metallic part includes; Cu, Pb, Zn, Fe, Cd, Be, Cr, Au, Pt, Pd, Ag, etc. The plastic part of the PWBs is mostly epoxy resins. These plastic resins also contain very toxic halogenated flame retardants (HFRs) [5]."

Jan 1, 2012

By K. L. Money, R. R. Bleakney, R. H. Hanewald

The processing of EAF baghouse dusts, rolling mill scales, and belt grinding swarfs from the specialty steel industry will be reviewed. In addition, the INMETCO process has been modified so as to recover nickel, chromium and iron from many other waste materials such as pickling solutions, filter cakes, spent nickel and chromium plating baths, super alloy wastes, and nickel-cadmium batteries. INMETCO is the only North American company presently capable of recycling nickel-cadmium batteries by high temperature metals recovery.

Jan 1, 2000

By Anette Mueller, Thomas Schnellert, Sérgio C. Angulo

"The use of automatically sorting technique, to separate gypsum components from recycled material of processed construction and demolition waste (C&DW), is motivated by environmental and economical aspects. Only if the gypsum can be separated the aggregates can fulfill the environmental requirements and also the structural characteristics according to the standards. Furthermore, the separation of red brick can also improve the quality of the aggregates.This paper aims at analyzing the separation of gypsum components and red brick by using the color sorting technique. The impacts on the composition and the envelope density of recycled aggregates are described. Depending on the gypsum content the application of two processing stages (rougher-cleaner) can be necessary to produce aggregates with sufficiently low gypsum content. Additionally, the separation of red brick and concrete is successful. So, the color sorting may be a promising technique to upgrade the quality of mixed C&DW aggregates.IntroductionConstruction and demolition waste (C&DW) is a mixture of different materials. Such mixtures can be used only in low grade applications. If the material is used as certified material for road construction or as aggregate in concrete the concrete particles must be separated from the other building materials. This paper aims at analyzing the separation of gypsum components and red brick by optical sorting. The needed stages of sorting for getting a product quality according to the German Standards are deduced.Gypsum is a building material that is increasingly used for interior works in Germany like it is shown in figure 1 [1]. At present the content of gypsum in C&DW is estimated at about 1 %. Assessments on the basis of material streams of gypsum and concrete and their life spans show that higher gypsum contents of about 3 % must be expected in future [2]. Also in other countries the use of gypsum has grown considerably in the last decades. From the characterization of C&DW available in some cities in Brazil, 4 to 15 % of total amount of C&DW that may arrive at the recycling plant to be processed is excessively contaminated by gypsum. In one of these cities, the average content of gypsum in the C&DW before processing was as high as 2.1 % [3]."

Jan 1, 2008

By Larry G. Twidwell, Jannette L. Chorney, Bryce D. Ruffier, Katelyn M. Lyons, Daniel W. Gaede, Ryan J. Foy, Jerome P. Downey

The Army Research Laboratory (ARL) has an interest in the recovery and processing of rare earth elements. At Montana Tech, elevated temperature chlorination of rare earth oxides is presently being investigated as a potential methods leading to the selective separation and recovery of rare earth elements from mineral ores and concentrates. After preliminary evaluation, ytterbium oxide was selected as a representative surrogate material for more extensive chlorination studies. Methods used to determine the conversion and recovery include X-ray diffraction (XRD) and inductively coupled plasma (ICP) analysis. These data have been used to establish and confirm process conditions that consistently yield high conversion efficiencies. Based on the promising results, further experimentation is underway to ascertain the metallurgical response of other rare earth oxides and carbonates to the roasting process. The end goal is to create a robust process for industrial application that has greater efficiency and reduced costs as compared to current practice.

Jan 1, 2015

"Depletion of known ore reserves and increased demand for precious metals have caused a revolution in biohydrometallurgical processing technology for gold recovery. Known ore deposits and future discoveries are most likely to be lower grade sulfide ores that can be difficult to recover with current leaching technology. Future metal recovery operations will increasingly use bio-oxidation techniques.Bacteria are an integral part of mineral cycling and mineral transformation in nature. Although biological processes are recognized as part of the mineralization and oxidation reactions in some ore deposits, they have only recently been applied to enhancing metal recovery in hydrometallurgical procedures. This paper explores the traditional metallurgical application of biological leaching and oxidation reactions and reviews the complete range of bacteria available for metal recovery systems. Pre-treatment of ores with bacteria improves metal recoveries in tank leaching systems and shows promise for heap leaching methods.IntroductionThere is no longer any question that bacteria playa natural role in the on-going transformation of some ore deposits (1,2). As applied to sulfide ores, a few strains have been specifically identified that exhibit a natural leaching potential (3). These bacteria can be isolated from waters and soils in old mining districts where they contribute to continuing leaching and pollution problems in acid drainage and heavy metal solubilization. Sulfur and iron bacteria as well as many heterotrophic strains have also been found in ore deposits and sedimentary rocks at depths up to 2000 meters (4). Their presence in both ore deposits and processed ores shows the microbial association with natural leaching and the potential role that bacteria can play in the development of new leaching technology."

Jan 1, 1988

By Gordon D. Jarvinen

Polymer Filtration (PF) Is an innovative, selecthle metal removal technology. Chelating, water-soluble polymers are used to selectively bind the desired metal ions and ultrafiltration is used to concentrate the polymer-metal complex producing a permeate with low levels of the targeted metal ion. When applied to the treatment of, Industrial metal-bearing aqueous process streams, the permeate water can often be reused within the process and the metal ions reclaimed. This technology is applicable to many types of industrial aqueous streams with widely varying chemistries. Application of PF to 'aqueous streams from nuclear materials processing and electroplating operations will be described.

Jan 1, 1999

By Senlin Xie, Wanlin Wang, Lejun Zhou

"The innovative development of multiphase slag in hot-metal treatment has attracted considerable attention due to the reduction of CaO consumption and minimal environmental emission. In order to improve the efficiency of dephosphorization and to reutilize the waste-slag as an alternative source of phosphate ores, it is important to increase the distribution ratio of P2Os between the solid solution (2CaO· SiO2-3CaO· P2O 5) and liquid slag. An investigation was carried out to study the effects ofNa2O and B2O3 on the distribution ratio of P2Os, the results indicated that the increase ofNa2O would enhance the distribution ratio of P2Os with the formation of solid solution (2CaO·SiO2-Na2O·2CaO·P2Os), while B2O3 has the opposite function, and changes the morphology of solid solution. The study would provide an instructive way for the design of multiphase slag and re-utilization of waste-slag.IntroductionIn order to meet the increasing demand for high quality low-phosphorus steel, it requires a high efficient hot metal dephosphorization process. The current slag system for hot metal treatment contains large amount of solid CaO dispersed in liquid slag, which introduced a large amount of CaO consumption due to its low solubility, especially when CaF2 was restricted due to the environmental concerns. Therefore, new refming method to improve the utilization efficiency of CaO by using a solid/liquid coexisting multiphase slag was proposed, and the studies regarding to solid solution formation mechanism, mass transfer behavior of phosphorus and the phase relationship for multi-phase slag have been conducted. [1-6]Normally, hot metal dephosphorization slag consists of CaO--SiOz-FeO--P2O 5, and it has been approved that 2CaO·SiO2 forms a solid solution with 3CaO·P2Os at the hot metal treatment temperature over a wide range of compositions. [7] Kitamura et al [8] pointed out that the (2CaO·SiO2-3CaO·P2O 5) solid solution plays an important role in dephosphorization, and it has been regarded as an absorbents for phosphorus to lower the phosphorus content in liquid phase, which makes it more capable for future dephosphorization. l Besides, the multiphase slag has the potential to be recycled as a source of phosphorus, if the (2CaO· SiO2-3CaO· P2O 5) solid solution could contain high phosphorus content, and it can be separated from FeiO matrix 8hase due to the large difference of their magnetic properties under the strong magnetic field. [10, 11]"

Jan 1, 2014

By David T. Bunney

In .December of 1987, International Mill Service, Inc. signed an exclusive licensing agreement with Tetronics Research & Development Co. Limited of Faringdon, Oxfordshire., England to commercialize plasma technology which had been demonstrated in an EAF dust processing application. The intent of the process is to reduce and volatize the zinc, lead and cadmium oxides inherent in EAF dust and collect these elements as metals in an ISP (Imperial Smelting Process) zinc splash condenser, and to render the resultant slag an inert, non-hazardous material. With these objectives in mind, IMS started commissioning facilities in 1989 at Florida Steel in Jackson, Tennessee and Nucor-Yamato Steel in Armorel, Arkansas. This paper will address the commercial development and progress of the technology at these two installations. Process Description In the EAF steelmaking process typically the off gas stream is cleaned by some form of baghouse. The particulate collected is known as Electric Arc Furnace dust and has been designated by the U.S. EPA as hazardous waste number K061, once it leaves the collection system. This designation was given to the material due to the high toxic concentrations of lead and cadmium (nickel and chromium for stainless EAF dusts) inherent in the dust. IMS' method of operation is to locate the facilities on the client mill's property adjacent to the baghouse. The dust is transported directly to IMS via a closed conveyance system. This method enables the technology to be an additional processing step in the steelmaking process. Once the dust has been transported to the IMS facility, it is fed, metered and mixed mechanically in the feed conveyance system with a carbon reductant (typically coke breeze). The carbon reductant is approximately 10% of the dust feed rate. This mixture passes through the feed system and enters the furnace

Jan 1, 1992

By Yuzhe Zhang, Xiaodi Huang, Xinli Wang, Bowen Li, Matthew Andriese, Jiann-Yang Hwang, Zhiwei Peng, Likun Li

With the development of the world, the waste tires have been a serious environmental problem. There are about 2 billion waste tires produced all over the world every year and about 500 million waste tires are produced in the United States. Most of the waste tires are land filled, which waste a lot of space. It takes hundreds of years to resolve the macromolecules of waste tire into the standard which does not pollute the environment. Microwave irradiation is a thermal processing way for waste tires decomposition. In this study, the relative dielectric loss factor of the tire at various temperatures was determined to understand the behavior of tires under microwave heating.

Jan 1, 2016