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By J. P. Gu, C. Beckermann

"Melt convection and macrosegregation in casting of a large steel ingot is numerically simulated. The simulation is based on a previously developed model for multicomponent steel solidification with melt convection, and involves the solution of fully coupled conservation equations for the transport phenomena in the liquid, mush, and solid. Heat transfer in the mold and insulation materials, as well as the formation of a shrinkage cavity at the top are taken into account. The numerical results show the evolution of the temperature, melt velocity, and species concentration fields during solidification. The predicted variation of the macrosegregation of carbon and sulfur along the vertical centerline is compared with measurements from an industrial steel ingot that was sectioned and analyzed. Although generally good agreement is obtained, the neglect of sedimentation of free equiaxed grains prevents the prediction of the zone of negative macrosegregation observed in the lower part of the ingot. It is also shown that the inclusion of the shrinkage cavity at the top is important in obtaining good agreement between the predictions and measurements.IntroductionMacrosegregation in large steel ingots is one of the most well-known and now classical problems in the field of solidification and casting [1]. Commonly found macrosegregation patterns in steel ingots are a positively segregated zone at the top, negative segregation near the bottom in the equiaxed zone, inverse segregation near the ingot surface, V-segregates along the centerline, and A-segregates in the columnar zone [2, 3]. It is well established that the macroscopic transport of species leading to macrosegregation can occur by a variety of mechanisms, including thermally and solutally driven natural convection of the melt in the mushy zone, flow due to solidification contraction, and the sedimentation of free equiaxed crystals. Fredriksson and coworkers [ 4,5] provide recent overviews of the solidification transport phenomena and macrosegregation in ingot casting."

Jan 1, 1999

By Michael I. Morris

The U.S. Department of Energy's (DOE's) Transuranic and Mixed Waste Focus Area (TMFA), funded from fiscal year (FY) 1996 though FY 2002, was tasked with finding solutions for the mixed waste treatment problems of the DOE complex. During TMFA's initial technical baseline development process, three of the top four technology deficiencies identified were the need for amalgamation, stabilization, and separation/removal technologies for the treatment of mercury-contaminated mixed waste. The Mercury Working Group (HgWG), a selected group of representatives from DOE sites with significant mercury waste inventories, assisted TMFA in soliciting, identifying, initiating, and managing efforts to address these areas. Solicitations and contract awards were made to the private sector to demonstrate both the amalgamation and stabilization processes using actual mixed wastes. The goal was to develop separation and removal processes that will address DOE's needs. This paper discusses the technology selection process, development activities, and the accomplishments of TMF A through these various activities.

Jan 1, 2003

By Lijun Lu, Honghui Fang

This article carried out the experimental study on using desulfurization ash in steel slag composite material. This was done by investigating the desulfurization ash content in formula one and formula two samples on the influence of setting time and strength of mortar. Through this study the following conclusions were reached for formula one: (1) a setting time of more than 10 hours is required, (2) a dosage of desulfurization ash of 1 ~ 2% is optimal, where flexural strength is reduced by 10% ~ 23% and compressive strength reduced by 5.7% ~ 16.4%. The conclusions of formula two were: (1) when the dosage of desulfurization ash is within 5%, the setting time is within 10 hours; (2) when the dosage of desulfurization ash is 1 ~ 2%, the flexural strength is increased by 5 ~ 7% and the compressive strength is reduced by 1 ~ 2%. The results show that the formula two is better.

Jan 1, 2015

By Sen-xiang Yang, Xin-teng Liang, Gui-jun Li, Jian-hua Zeng, Yong Chen

"This research is based on PANSTEEL 120t steelmaking converter technology to have the quantitative description of the time needed in uniform mixing of molten steel in the converter with the computer. In present work, the numerical simulation approach is used to analyze oxygen lance nozzle, the flow condition of oxygen and flow status of molten steel in the converter. The various oxygen jet flows that come out from different angles and the flow status of all kinds of jet flows in the converter have also been simulated. All of the simulation parameters are based on the specifically practical conditions according to the physical conditions of PANSTEEL 120 t steelmaking converter. Through numerical simulation, the angle parameter of the oxygen lance nozzle is 16 °. The optimized oxygen lance 536-16 has a good performance in industrial application. This kind of phenomenon shows that the ways and processes of numerical simulation in this research are right.IntroductionThe oxygen lance system is the significant process in semi-steel making converter. It's related to whether the converter or even the whole system can function well. While in actual production, many problems emerge in the process of using the former oxygen lance, such as re-drying, slopping, high lance position, dead burning and even blowing out. In continuous fast-paced process, the unstableness of oxygen lance will lead to speed droop or even stop pouring. Analysis shows that all these problems are not only related to the raw materials but also the design of oxygen lance. Bad oxygen lance's scorification kinetics condition and low content of FeOn in early slag are the direct factors that we cannot easily control in steelmaking at present [l]. Therefore, the good scorification kinetics condition which is related to nozzle has good influence on BOF steel making."

Jan 1, 2013

By Qingguo Xue, Jingsong Wang, Guang Wang, Yuanyuan Zhang

Due to complicated structure and composition of high-phosphorus iron ore, pure substances were used to simulate the chemical composition of high-phosphorus iron ore to study the reaction of fluorapatite at different temperatures and effect of additives. The gasification process of P during carbothermic reduction process was investigated using a quadrupole mass spectrometer gas analysis. It is found fluorapatite was reduced to phosphorus which diffused into iron and gas phase. From the gas analysis, it was observed that PO and P gas species were vaporized around 800 °C. As the reduction temperature increased, the diffusion of phosphorus into iron was enhanced. The presence of Ca(OH)2 as additives not only promoted the reduction of iron oxide, but also decreased the degree of fluorapatite reaction to inhibit P into iron.

Mar 1, 2018

By C. D. Mishra

The recycling potential for any gainful utilisation of the waste products is dictated by their quality, especially the chemical characterisation. The methods commonly used for the analysis of fly ash e.g. wet chemical, AAS, ICP-AES etc are time consuming. The paper describes a rapid XRF-based method for routine analysis of fly ash which involves preparation of local standards, optimisation of sample preparation technique and use of a simple PC-based software to account for interelement effects. The matrix corrected values are found to agree well with the wet chemical data.

Jan 1, 1992

By James E. Simpson, Suresh V. Garimella, III de Groh

"An experimental and numerical study of the horizontal Bridgman growth of pure succinonitrile (SCN) and of a succinonitrile-1.0 mol. % acetone alloy (SCN-1.0 mol. % ACE) has been performed. Experiments at growth rates of 0, 2 and 40 µmis were investigated. The solid/liquid interface was stable (non-dendritic and non-cellular); however, it was not flat. Rather, it was significantly distorted by the influence of convection in the melt and, for the growth cases, by the moving temperature boundary conditions along the ampoule. For the alloy, the interface was determined to be unstable at growth rates greater than 2.8 µmis, but stable for the no-growth and 2 µmis growth cases. When compared to the pure SCN interface, the alloy interface forms closer to the cold zone,· indicating that the melting temperature has been suppressed by the addition of the alloying element. Two-dimensional computer simulations were performed for the no-growth case for both the pure and alloy materials. These simulations indicate that a primary longitudinal convective cell is formed in the melt. The maximum magnitude of velocity was calculated to be 1.515 mmls for pure SCN and 1. 724 mm/s for the alloy. The interface shape predicted by the computer simulation agrees well with the experimentally determined shape for the pure SCN case. In ongoing work, numerical simulations of the process during growth conditions are being performed.IntroductionIncreasingly, advanced materials used in the aerospace, automotive, optics and electronics fields require low levels of defects and high levels of solute uniformity. Directional solidification by the Bridgman process is widely used for synthesis of these high-quality materials. During Bridgman crystal growth, heat and mass transfer by both thermal and solutal gradient-driven convection and diffusion influence the shape of the solid/liquid interface and dopant segregation levels, and hence, directly determine the final crystal quality. Key process parameters include the applied furnace temperature distribution and rate of translation, ampoule properties and furnace orientation."

Jan 1, 1999

By Oscar J. Restrepo

Through reactions in solid form at high temperatures, using iron oxide (Fe3O4) and chromium oxide (Cr2O3) in fixed proportions as precursors, the compound was synthesized with spinel structure type FeCr2O4. For different temperatures synthesis was conducted the characterization of the material obtained through X-ray diffraction (XRD), spectroscopy UV-VIS-NIR, scanning electron microscopy (SEM), energy dispersion analysis of X-ray (EDX) thermal analysis (DTA / TGA) and magnetic susceptibility of alternating current. The changes in the spectra of reflectance changes are related to the phase identified, the degree of crystalline structure, the spatial order of cations and the magnetic behavior obtained.

Jan 1, 2009

By Kiyoshi Shibata

A new assessment model has been proposed for metal production and its recycling system. The model consists of three processes, smelting of ore, cascading and upgrading of metal scrap. The present approach is to assess the total energy consumption of the system, by introducing two equations for describing the relationships between critical impurity content and the mass of production or scrap recycling. The total energy consumption in the system can be described as a function of recycling rate and performance of the upgrading process. The present model suggests that the impurity removal efficiency and yield in the upgrading process are essential to reduce the energy consumption in the systems. Especially, such points should be explicitly controlled in recycling of aluminum. The potential capability of this model was also discussed by obtaining several quantitative information required for the process design and the operational control of beneficial recycling of metals.

Jan 1, 1998

By Fathi Habashi

During the recovery of copper, nickel, zinc, and lead from their sulfide ores, large amounts of sulfur dioxide are generated. A fraction of this gas is captured and transformed into sulfuric acid and liquid SOl and the remainder is emitted to the atmosphere. Numerous proposals were made to solve this problem. Hydrometallurgy offers the only valid solution by which elemental sulfur instead of sulfur dioxide can be produced. Sulfur can be easily stored, transported long distances, or transformed into S02 and H2S04 when desired.

Jan 1, 1996

By S. q. Honingh, G. Van Weert

Currently produced zinc-enriched blast furnace dust is stored on site at CORUS IJmuiden. To end this practise, a research program was started in 1996. Four technologies were studied: oxidative autoclave leaching in a chloride medium, fluid bed pyrohydrochloridisation (pyrohydrolysis) to yield lead-zinc-free (hematite) calcine, EAF (plasma) smelting/zinc fuming, and incorporation of the dust in 'iron foundry cupola charges. All aim to remove zinc and lead, recycle the iron residue internally, and produce a saleable zinc-lead product.

Jan 1, 2000

By V. I. Lakshmanan, R. Roy

Base metals and PGMs are currently recovered from sulfide concentrates using pyrometallurgical processes. These processes suffer from several limitations such as being capital intensive, scaling problems, S02 emissions and long delay in value recognition. Alternative hydrometallurgical technologies have so far not been successful and currently total pressure oxidation and partial pressure oxidation hydrometallurgical technologies are being evaluated. Process Research ORTECH has developed a unique hydrometallurgical process to recover base metals and precious metals using mixed chloride technology. In a first stage leach, base metals are recovered and elemental sulfur is liberated from hydrogen sulfide formed during this leaching stage. During second stage leach, precious metals are recovered using proven separation technologies. Some of the advantages of the process are the recovery of elemental sulfur from sulfide sulfur, recycle of the chloride lixiviant thereby eliminating effluent treatment steps and use of excess energy from the Claus reactor for the pyrohydrolysis step.

Jan 1, 2011

By Yungang Li, Hui Li, Ramana G. Reddy, Jinglong Liang

High solid corrosion protective coatings were prepared by the dust of the converter with an average particle size of 59.33 μm. The effect of different amount of benzyl alcohol diluent on the performance of high solid anti-corrosion coatings was studied. With the increase of the amount of diluent, the viscosity of high solid anti-corrosion coatings reducing, the film apparent bubble content decreasing, and film resistant to salt water corrosion ability decreased, while acid corrosion capacity enhancement. When the dosage of diluents is 15%, the coating film is more resistant to acid corrosion.

Mar 1, 2017

By Priscilla Aki Mori de Hanashiro, Viviane Tavares de Moraes, Denise Crocce Romano Espinosa, Hugo Hashimoto

"The LCDs are used in televisions, calculators, mobile phones, computers (laptops and tablets), video games and other electronic devices. The advancements in technology make obsolete these devices, causing excessive disposal of LCDs and therefore decreasing life span of landfills. In this context, the LCDs from LED LCD TVs arise as an additional source of waste electrical and electronic equipment (WEEE). Thus, it is essential to develop LCDs recycling methods, beginning with the LCD characterization followed by displays processing, aiming the materials separation and using some Ore Treatment Techniques, and finally, the recovery of indium using acid leaching. The analysis methods that will be used in this work are: Fourier Transform Infrared (FT-IR) and Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES).IntroductionLiquid Crystal Display (LCD) technology is applied in modem televisions, calculators, mobile phones, computers and a wide range of electronic devices. It has replaced Cathode Ray Tube (CRT) technology as the most advantageous display product, due to lower electrical power consumption, size and weight reduction, and no radiation emission [ 1]. The constant improving of LCD screen technology reflects on its growing contribution to the amount of waste electrical and electronic equipment (WEEE): an estimated 50 million tons of WEEE are produced every year [2]. Once the most common method of its disposal are landfills, the LCD technology therefore became an environment issue [3].LCD structure is composed by components made by different materials. In order to develop a LCD recycling methodology that gives the right destination to these materials, a previous characterization stage is required. This characterization includes a disassembly process and material identification analysis. One of the LCD components is the screen, which is composed by polymeric and glass layers. The liquid crystal glass was the starting material of this study. It contains indium in the form of indium tin oxide (ITO) film. This ITO film is deposited in the glass by a sputtering process and acts as the electrode material [4,5]. It has in its composition 90% ofln203 and 10% ofSn02 [6]."

Jan 1, 2014

By R. Singh, C. Gong, J. Chaudhry

"Metalorganic chemical vapor deposition (MOCVD) is an ideal technique for the deposition of conducting and non-conducting oxide based thin film materials. In this paper we have presented a study of photo assisted MOCVD for the low temperature deposition of a number of oxide based advanced materials. We have used incoherent light sources as the source of optical and thermal energy in our MOCVD system. The vacuum ultraviolet (VUV) and ultraviolet (UV) photons can enhance the surface reaction of the absorbed molecules through the perturbation of the electronic state of binding between the absorbed molecules and the solid surface. Unlike plasma process, no surface damage is expected and high quality materials have been deposited. At a given substrate temperature, the performance of deposited film depends on the lamp configuration.INTRODUCTIONMetalorganic chemical vapor deposition (MOCVD) has become the standard manufacturing technique for the deposition of large area thin films of compound semiconductors. l.(.w-cost, high crystalline quality, atomically clean and sharp interfaces, atomic layer epitaxy, high throughput rates and potential for direct writing are some attractive features of MOCVD. Due to a number of potential advantages mentioned above, MOCVD is considered as an ideal technique for the deposition of various electronic and optical materials for a wide variety of applications. Rapid isothermal processing based on incoherent radiation as the source of optical and thermal energy is emerging as the key low thermal budget (integral of processing time and temperature) processing technique for the fabrication of current and next generation of microelectronic and optoelectronic devices and circuits [1]. In this paper we have demonstrated that the design of the lamp assembly plays an important role in determining the properties of the materials deposited by RIP assisted MOCVD. We have studied the growth rates, structural properties and electrical properties of Y2O3/Si structure. At a given substrate temperature, best results are obtained for the lamp assembly that provides maximum number of VUV and UV photons."

Jan 1, 1994

Two pilot-plant investigations were conducted in which strong-base resins were compared with activated carbon for the extraction of gold cyanide from leached pulp from the Golden Jubilee Mine. The results show that gold can be recovered with carbon, but that the extraction efficiency is poor, probably because high concentrations of humic and fulvic acids are. present m the pulp. .However the extraction of gold cyamde from this material with strong-base resins JS very effo:1ent, and the overall efficiency of extraction is better with resin than with carbon, even when the concentration of resin is one-third that of carbon, and the flowrate of resin is one-third that of carbon. The results of the pilot-plant campaign reported in this paper led to the conversion of the Golden Jubilee plant from carbon-in-pulp to resin-in-pulp in February 1988.

Jan 1, 1989

By Yuanbo Zhang, Zhixiong You, Li Qin, Guanghui Li, Tao Jiang

Low-grade manganese oxide ore is generally characterized by high iron content. In this work, sulfidation roasting of an iron-rich manganese oxide ore with elemental sulfur was characterized. The experimental results indicated that manganese dioxide can be selectively reduced over iron oxide by using elemental sulfur. The manganese phases in roasted product included low-valence manganese oxide, manganese sulfide and manganese sulfate, while those of iron mainly depended on the sulfur addition. Iron oxide would only be reduced or sulfidized at larger sulfur additions. The effect of roasting temperature and S/Mn mole ratio on the phase transformations was also investigated; extractions of Mn/Fe by sulfuric acid were evaluated. An extraction of Mn greater than 95% was obtained while that of Fe was controlled less than 10% under the optimal conditions.

Jan 1, 2016

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

The Metallurgical and Materials Engineering Department at Montana Tech is investigating various methods of extracting and refining rare earth elements from mineral ores and concentrates. As part of this research, an elevated temperature “roasting” process has been evaluated as a means of converting the rare earth elements contained in various matrices to bromides as a pretreatment step in preparation for downstream rare earth element extraction and recovery operations. Laboratory and bench-scale experiments have been performed to assess the effects of varying temperature (150 to 400° C), time (1 to 4 h), and the ammonium bromide to rare earth oxide molar ratio (6 to 24) in the roaster charge. The results show that nearly complete bromination of the rare earth oxide is achievable when the roast is performed under optimum conditions.

Jan 1, 2015

By Junmo Ahn

This study investigated leaching kinetics by alternative lixiviants for copper leaching from chalcopyrite (CuFeS2), the most abundant copper resource in the world. As a refractory sulfide mineral, chalcopyrite shows low copper extraction due to passivation on chalcopyrite surface. Also, decrease of copper grade with high portion chalcopyrite requires the alternative leaching procedure to increase copper recovery. Therefore, alternative lixiviants such as sulfurous acid and methanesulfonic acid (MSA) were tested for both concentrate and low grade ore to enhance copper extraction. Also, an oxidant, hydrogen peroxide, was compared to ferric to find out the improvement of leaching kinetic. In concentrate leaching tests, 30 g/L MSA showed the highest copper extraction (47%), compared to other lixiviants at 75 °C. Periodical H2O2 addition enhanced copper extraction, and above 90% of copper extraction was observed within 96 h by periodical addition of 0.6% H2O2 at 75 °C. The activation energy of chalcopyrite leaching by MSA and H2O2 achieved 40 kJ/mol, which is chemical reaction control. The results of low grade ore leaching tests indicates that no significant difference among lixiviants (H2SO4, H2SO3 and MSA) with ferric was observed, all of which achieved around 37% within 24 h at room temperature. However, significant increase of copper extraction (>80%) was observed at both 20 g/L MSA and 10 g/L H2SO4 conditions by the addition of 10% H2O2.

By D. Van Dooren

The final goal of the research project is to develop a 3D FEM model that is able to predict the kinetics and micro-structural evolution during the bainitic transformation. The input parameters consist of thermodynamic and atomic mobility data obtained from the ThermoCalc and mCTRA databases combined with structural mechanics data extracted from the stress-strain curves of the fcc and bee phases. In this paper the general principles of the model are outlined and some interesting preliminary results are shown and commented. The full implementation of the model has presently not been achieved yet. In the model the bainitic transformation is considered as a sequence of martensitic (re)nucleation and growth of a ferritic subunit followed by the carbon rejection into the surrounding austenite. The (re)nucleation of the subunits will be described through a non-classical martensitic nucleation criterion. Once a nucleus has been activated at a specific location in the material, a full-sized subunit is instantaneously formed through a displacive mechanism. The stress state in the system that arises due to the transformation strain can be calculated by a 3D FEM programming code. Immediately after the formation of the subunit, another 3D FEM programming code calculates the carbon diffusion from the supersaturated ferrite into the surrounding austenite. The resulting stress state and carbon profiles will be used to determine where and when a new subunit will nucleate based on a renucleation criterion. Keywords: Bainitic Transformation, Modeling, Eshelby, Carbon Diffusion

Jan 1, 2003