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By W. C. Hellyer

The papers in this section provide several examples of the application of Process Mineralogy to metallurgical problems. Any experienced metallurgist could cite numerous other examples when process mineralogy has, or could have, provided data of value in his understanding of metallurgical processes. The data developed by mineralogic techniques may supplement conventional chemical analyses, but cannot be replaced by assays. Mineralogic and chemical analyses each provide different types of information. In order for the process mineralogist to interpret his results in the most useful manner, it is desirable that he should have some knowledge of metallurgical processes. Conversely, the metallurgist should have some knowledge of mineralogic techniques to understand the scope and limitations. Mineralogic examinations are time-consuming and expensive. To ensure the effort is not wasted, and indeed does not generate misleading information, the utmost care must be taken at every stage of sampling and sample preparation. The mineralogist may examine microscopically or by x-ray diffraction a one-gram sample representing a flow of possibly thousands of tons per day through a concentrator. Conditions in a concentrator change continually in response to changes in feed rate, feed characteristics, grind, reagent additions, temperature, circulating loads, etc. Lengthy sampling periods are required to ensure the samples examined are representative of average conditions. The sampling program should be drawn up jointly by the metallurgist and mineralogist. Sampling points should be selected with a view to ease of sample cutting. The sampler should be instructed in the method of cutting the samples, the weight or volume of sample to be taken at each cut, the sampling frequency, and sampling period. The sampling period required depends on the scope of the investigation. For example, if a complete survey is to be made of all final and intermediate products of a flotation concentrator, samples should be cut at not more than two-hour intervals, twenty-four hours per day, for not less than one week. For a more limited investigation of one circuit or one section of a concentrator, 'the sampling frequency could be increased to every hour and the sampling period reduced to one or two days.

Jan 1, 1981

By E. M. Alcântara

This paper describes some aspects about the relationship between copper electrorefining addition reagents and the hydrogen in the cathode. The conditions of electrorefining were studied by factorial design methods. The advantages of this technique are reduction in the number of tests, well organized experiments; improvement in productivity and reliability of results. The dosage of the two main addition agents, glue and thiourea, were varied simultaneously and compared with the hydrogen content in the cathode. The influence of these factors, as well their interactions were analyzed by statistical methods denominated ANOVA (Analysis of Variance). The increase of thiourea quantities, within of levels studied, influenced significantly at 95% confidence in the hydrogen content in copper cathode.

Jan 1, 1999

By Antonio de Ita, Isaias Hilerio, Miguel Barron

"The influence of an unconventional lance with a central nozzle on the multiphase fluid flow in a steelmaking converter is studied in this work by means of computer simulations. The lance has four peripheral supersonic nozzles and a vertical central nozzle. Besides, the oxygen flow in the central nozzle is considered independent from the main oxygen supply. Transient two-dimensional numerical simulations were carried out considering just molten steel and gaseous oxygen as the existing phases. Numerical results show that bath agitation and droplet generation are enhanced as a result of the central nozzle. However, the performance of this lance strongly depends on the distance of the lance tip to the molten steel surface and the velocity of the oxygen jet.IntroductionCurrently, two thirds of the world crude steel is produced through the steelmaking oxygen converter [1]. Given the unquestionable economic importance of this technology, any improvement or optimization proposal is welcome. In the majority of current oxygen converters a top oxygen supersonic jet is blown onto the molten steel through a water-cooled lance to eliminate by oxidation some impurities such as carbon and phosphorus. Conventional lances have inclined peripheral nozzles whose number depends on the converter capacity. During the process, a large amount of gases evolves, forming metal droplets and a metal-slag-gas emulsion [2]. The droplets and the resultant emulsion increase the reaction interfacial area, promoting in this way carbon removal and dephosphorization of the molten steel bath [3]. However, during the blowing stage, the emulsion rises towards the lance and converter mouth and frequently forms layers which accumulate in the lance, reducing the life of the lance tip [4, 5]. It is possible that some freezing of the molten metal occurs due to the low oxygen injection temperature, however there are no reports on this. Besides, frequently undesirable operating phenomena such as spitting and slopping may arise as a result of inappropriate blowing practices or bad lance design. In the oxygen steelmaking industry, novel lances design are needed in order to enhance the decaburization rate and the slag formation and, at the same time, preventing operating practices that decrease productivity and move away the shop from safety standards."

Jan 1, 2012

By W. G. Davenport

The paper "Copper Smelting to the Year 2000" was presented at the CIM Conference of Metallurgists in Sudbury, August 1979. That paper predicted, in part, that high matte grade, high oxygen smelting - particularly in flash furnaces - would dominate copper smelting until the beginning of the next millennium. The present paper re-evaluates that prediction and examines the changes that have occurred and will occur in copper extraction in the 1990's. Of particular interest is the question as to whether major competitors are on the horizon for flash smelting and Peirce-Smith converting. Recent results with direct-to-blister smelting, lance smelting and submerged-tuyere smelting are reviewed and their roles in future copper smelting are predicted. Requirements for H2SO4 plants which handle the off-gases from modern smelting/converting processes are also examined.

Jan 1, 1993

By Shichao Zhao, Ke Xie, Qijie Zhai, Wenbin Xia, Yuanyi Guo, Changjiang Song

"This paper investigated the structure evolution and phase formation ofFe-(11,13,15wt.%)Mn alloy under near-rapid solidification conditions. It is found that the area ratio of equiaxed zone in the Fe-13Mn alloy is the largest. And the primary dendrite arm spacing of Fe-(11,13,15wt.%)Mn alloy increased clearly with increasing distance from the surface. The volume percentage of HCP phase increased with increasing manganese content in the range from 11 pct to 15pct.IntroductionThe developing trend of automobile is the energy conservation, enviromnent protection, light weight, and high security. So the material would be required to the higher strength, higher plasticity and more likely to processing of automotive steel. Fe-Mn based alloys is considered as a potential material to the third generation automobile steel for its high damping performance [1], good mechanical properties [2-3], and high young's modulus [4]. And it is important that metastable HCP phases of Fe-Mn based alloys, which attracts technological interest for theoretical and experimental research [5-6].Metastable materials have been extensively used in the area of iron steels. Among various fabrication methods for high performance materials, rapid solidification is one of most popular ways to produce advanced materials by obtaining metastable phases. The solidification of metals in metastable phases provides access to an extended range of materials properties with novel properties [7]. Thus, in this work, Fe-Mn alloy metastable materials prepared by near rapid solidification is studied."

Jan 1, 2013

By Ehsan Vahidi, Fereshteh Rashchi, Amirhossein Shahnazi

"The pig iron from steel manufacturing plants contains a high concentration of vanadium-bearing materials smelted with iron ore. During the oxidation process of the molten pig iron with oxygen lances, vanadium transfers to the slag. In this research, recovery of vanadium from LD (Linz-Donawitz) converter slag of steelmaking plant was investigated. The leaching residue was characterized by XRD and XRF techniques. The maximum vanadium recovery was achieved at optimum leaching conditions of 70 °C, S/L: 1/15, sodium hydroxide concentration: 3 M and leaching time: 150 minutes. The dissolution rate increased with rising sodium hydroxide concentration and temperature and decreasing particle size. The experimental data are treated graphically to explain the kinetics of the vanadium recovery process using shrinking core model (SCM). As a result, the controlling regimes in the SCM were analyzed separately using liquid film diffusion control, solid product diffusion control, and reaction control mechanisms.IntroductionVanadium is commercially important as a constituent of several alloys and catalysts. Nowadays, vanadium is mostly recovered as a by-product from secondary sources or from industrial waste streams such as titaniferrous magnetite, fly ash, spent catalysts, and petroleum coke. Steelmaking operations are specifically concerned by this problem due to the production of a huge quantity of by-products [1]. These by-products, including LD converter slag, sludge, fly ash, spent catalyst, ash, and alloyed scrap, contain a notable amount of heavy metals which may cause environmental problems. Solvent extraction is one of the techniques being increasingly used for the recovery of vanadium [2]. Apart from vanadium ore, secondary resources such as titanmagnetite, ilmenite and slag from the ferrous industry are a major source of supply. The pig iron from steel manufacturing contains a majority of vanadium-bearing materials smelted with iron ore. In a heat resistant shaking ladle the molten pig iron is oxidized with oxygen lances, causing the vanadium to be transferred to the slag. Normally, the vanadium in LD converter steel slag (coming from Linz-Donawitz steelmaking process) is ca. 5% as vanadium pentoxide (V2O5). This slag is the world's principal raw material for vanadium production [3, 4]. Moskalyk and Alfantazi [4] reported that a roast-leach process is used in South Africa for the production of vanadium oxides from magnetite ores while some of the slag was converted to ferrovanadium. A portion of the slag was exported to Europe for the production of vanadium oxide. The researchers mentioned that alkaline roasting was the main process at that time employed to extract vanadium pentoxide from vanadium slags."

Jan 1, 2012

By llya Perederiy, Vladimiros G. Papangelakis, Indje Mihaylov

"Nickel slags obtained from various smelting furnaces and converters differ in terms of their chemical composition and microstructure. The microstructure of the slag is largely affected by how fast the slag is cooled after being discharged from the furnace. Slow cooling is known to promote crystallization and growth of phases such as crystalline fayalite (Fe2Si04), magnetite (Fe3Ü4) and vitreous silica (S1O2). Slag granulation causes rapid solidification of the melt in the form of either an amorphous solid or highly intergrown crystalline silicate and oxide phases. Smelter slags contain entrapped Ni, Co and Cu in the form of dissolved oxides and matte inclusions. Extraction of the entrapped metals by high pressure oxidative acid leaching (250°C, 70 g/L initial H2SO4, up to 90 psi O2, 45 min) relies on the dissolution of the metal bearing minerals. The impact of the slag microstructure on the accessibility of these minerals to leaching, as well as the morphology of the produced residues is discussed in this paper.IntroductionIt was shown previously that entrapped base metals can be efficiently extracted from naturally cooled (as opposed to granulated) crystalline nickel smelter and converter slags using high pressure oxidative acid leaching operating at 250°C, ~40 g/L terminal acid and 60 to 90 psig oxygen overpressure [1, 2,3,4, 5, 6].Mineral characterization work performed on a naturally cooled crystalline nickel furnace slag from Vale's operations in Sudbury (ON, Canada) was previously reported [4]. Fayalite (Fe2Si04) and magnetite (Fe3U4) were detected using powder X-ray diffraction. These two minerals as well as silica (S1O2) and matte ([Fe,Ni,Cu]Sx) were also identified with the help of energy dispersive X-ray spectroscopy (EDX) on cross-sectional images obtained with a scanning electron microscope (SEM) operating in the backscattered mode. Nickel converter slags obtained from Vale's operations in Sudbury were found to be mineralogically similar to the furnace slag, but with higher contents of matte entrainment and magnetite based on the SEM-EDX observations [6]."

Jan 1, 2012

By T. C. Tseng

Austenitization is a critical stage in heat treatment of steels. The available kinetic data in reference to various initial microstructures are very limited, particularly at high heating rates. In this study, integrated experimental and computational approaches have been conducted to quantify the progress of austenitization and the attained microstructure. In particular, the study is concentrated on cementite and carbide dissolution in two steel grades. Various computational methods are developed to facilitate the study: (l) an algorithm for direct determination of kinetics data as well as progress of transformation from high-rate dilatometer tests; and (2) a suite of mesoscale computational models for particle dissolution, elements diffusion, mechanics, thermodynamic and the resulting kinetics of transfonnation. Critical exprimentation is carried out using advanced techniques in microstructure characterization, chemical analysis, and Gleeble thermal-mechanical simulator on specimens of well-controlled initial microstructures. Keynotes: Cementite, Carbite, Dissolution, Steels, Austenitization

Jan 1, 2003

By J. Michael Canty

Over 25 years of US research in Mineral Recovery from Geothermal Solutions have lead to few commercial applications. With the World Bank program in Kamchatka, Russia in September 2005 a step was taken to vitalize and coordinate the many efforts to advance economic mineral recovery systems worldwide. The US Department of Energy is helping to spur on the interest and research needed to realize the many benefits of extracting minerals from geothermal solutions. The excitement of recovery of minerals from geothermal brines has many positive angles. The economics of certain geothermal site is improved if a revenue is arrived from a sellable commodity with the geothermal power. The use of cleaner geothermal brines also improves the capable use of the brine before reinjection. We will review the history of Geothermal in the USA and the opportunities for recovery of different minerals and the markets for them.

Jan 1, 2006

By Magdalena Regel-Rosocka

Extraction of zinc(II) from hydrochloric acid solutions is discussed. The literature on the extraction of zinc(II) in the presence of iron(III) and iron(II) with various basic and solvating reagents has been reviewed. It was found that tributyl phosphate (TBP) is the best compromise, and permits both effective extraction of zinc(II) and its stripping with water. The process was confirmed in a continuous laboratory mixer-settler circuit.

Jan 1, 2003

By Yu Yamashita

There have been increasing in melting recycled scraps in copper smelting processes, and thus growing interests in the chlorine behavior. In this study, chloride dissolution in FeO-Fe2O3-SiO2slag (SiO2sat.) at 1523 K has been measured with varying in PCl2 from 1.13x10-8 to 1.30x10-7atm. and the oxygen partial pressures encountered in typical copper smelting furnace, i.e. PO2=10-8 to 10-10 atm. Discussion is made on the chloride capacity of FeO-Fe2O3-SiO2 slag in terms of its characteristics and the dissolved chlorine species. It has been shown that the mostreasonable dissolution reaction and chloride capacity can be expressed by the following reactions, where chlorine dissolves in the form of Cl-; here, aO2-, oxygen ion activity, is shown a function of oxygen partial pressure in the atmosphere. [ ]

Jan 1, 2006

By V. A. Bryukvin

A characteristic feature of the macrokinetics of the interaction process is the presence of two specifically defined areas of oxidation which had a linear time dependence. The effect of variables, such as residual sulphur content of the melt, temperature and the oxidation potential of the gas phase, on the macrokinetics of oxidation are investigated. Phase composition and structure of products of solidification of partially oxidised melts and thermodynamic properties pentaining to Cu-S-O melts are used to analyze the macrokinetic behaviour and mechanisms of the interaction. The process of interaction of sulfide copper melts with oxygen may be considered as a disproportional absorption process and its mechanism is based on localized interaction on the surface and inside the melt volume. Superficial processes include also the process of primary chemisorption of oxygen by melts at place of metal-metal donor bonds proceeding with formation of oxysulfide liquid solutions and volumetric decomposition of the latter accompanied by evolution of sulfur dioxide and metallization of sulfide melts. It is the degree of dynamic balance of such interaction processes that determines specific individual features of the macro-kinetics and mechanism of oxidation of sulfide copper solutions with oxygen in the gas phase.

Jan 1, 2006

By Rzyman Michal, Nakamura Takashi, Shibata Etsuro, Grabda Mariusz, Oleszek-Kudlak Sylwia

"Tetrabromobisphenol A (TBBPA) and many systems based on the synergistic effect of brominated organic compounds with Sb2O3 are extensively used as effective brominated flame retardants (BFRs) in many materials such as plastics and textiles. Thermal degradation of BFR containing plastics leads to the formation of hydrocarbons and gaseous compounds such as HBr and SbBr3. Our thermodynamic considerations indicate that these gases can act as bromination agents for metallic oxides such as ZnO, Cu2O, CuO, PbO and FeO. Moreover, these metallic oxides have the thermodynamic tendency to brominate easier than does Sb2O3. The aim of this study was to investigate experimentally the reactivity of ZnO with 1) HBr originating from the thermal decomposition of TBBPA and 2) SbBr3, which is formed during thermal degradation of brominated flame retardant plastics. The thermal treatments of the mixture of compounds of interest were investigated by thermogravimetry coupled with mass spectrometry.IntroductionTetrabromobisphenol A (TBBPA) and many systems based on the synergistic effect of brominated organic compounds with Sb2O3 are extensively used as effective brominated flame retardants (BFRs) in materials such as plastics and textiles. For instance, 4.5 million tons of flame retardant plastics containing BFRs are produced in Japan each year. Thus, in thermal treatments such as the incineration and melting of solid wastes, BFR containing plastics are intentionally or unintentionally included in the wastes. Thermal degradation of BFR-containing plastics leads to the formation of hydrocarbons and gaseous compounds such as HBr and SbBr3 [1-5]. Our thermodynamic considerations [6] indicate that heavy metal oxides such as ZnO, Cu2O, CuO, PbO and FeO should easily react with HBr prior to Sb2O3 and also with SbBr3, the main gaseous product in the thermal decomposition of TBBPA, forming low boiling point metallic bromides suitable for the volatile separation of heavy metals. The metal oxides are also expected to qualitatively and quantitatively affect debromination and decomposition of the flame retardant."

Jan 1, 2008

By Tzu-Chien Lin, Jack Tsai, Ming-Yu Lin, Der-Ray Huang, Jiin-Sen Chen, Jing-Xuan Lin

"In this paper, some DVD-R discs have been selected for long time light exposure test and high temperature and humidity test. Generally, recordable media under long time light exposure maybe be defected seriously. If we use Jitter value 8% as a reference to determine the life time of DVD-R samples, some discs defect after 5 hours of light exposure while some discs can endure over 25 hours. Also if we use reflectivity 45% to determine the life time, some discs defect after 30 hours light exposure while some discs can endure over 40 hours. From our results, the good samples show good characteristics of PI error. The absorption spectrum of recordable media is a good reference to justify the quality of dye media. These results can be used to estimate the life time of recordable discs.IntroductionIn general, the life time of DVD-R with a layer of organic dye recording layer is required for preservation in decades. In addition to optical characteristics and thermal properties, we still need to consider the stability of the dye in recording media. The presentation of the color on organic dye is not only related to the material's property but also related to the light exposure. In this study, we focus on the absorption characteristics and reflectivity of organic dye in optical recording layer after light exposure. The optical properties of discs depend on the functional groups and molecular structure [1]. According to ""DVD Specifications for Recordable Disc (DVD- R)"", the reflectivity should higher than 40%. From measured reflectivity, we can confirm that the important issue is whether dye be affected by light exposure or not. Because each specific functional group absorbs the specific spectrum, we can check the characteristics of functional groups from their UV/Visible Spectra. We also use High-performance liquid chromatography (HPLC) to detect the different components of dye on the recording layer [2]. The jitter value test is to test the error cause by digital signal of recording media. If we use jitter value 8% as a reference to determine the life time of DVD-R samples, the purpose of this study is to investigate the jitter values of recording media after high light exposure and high temperature/humidity test. The results of these test will be helpful for the development of long-life optical storage media."

Jan 1, 2012

By D. F. Liub, Z. Y. Liu, W. Y. Xue, Y. F. Shenb, Y. D. Wang

"The microstructure characteristics and deformation behavior of ultrafme grained (UFO) 304SS fabricated by accumulative rolling and armealing have been investigated by means of tensile tests, electron-backscatter-diffraction (EBSD) and transmission electron microscopy (TEM) techniques. The volume fraction of martensite phase decreases with increasing armealing temperature. In the grain sizes ranging from 300 nm to 10 µm, the strength held Hall-Petch relationship. The sample with an average grain size of 300 nm exhibited extra high yield strength of 1700 MPa and a tensile strength of 1780 MPa, while the elongation retains 12%. The limited uniform elongation in the UFO materials could be explained in terms of plastic instability. Very interestingly, for the bulk material with an average grain size of 1.200 µm, the high yield strength and uniform elongation were simultaneously achieved to be as 1000 MPa and 18%, respectively.IntroductionUltra-high strengths have been achieved in elemental metals by employing heavy plastic deformation, or by creating ultra-fine-grained (UFO) structure. Here UFO materials are defined as polycrystalline solids with property-controlling microstructural features below the 1 µm level. Typical processing routes include severe plastic deformation (SPD) [1, 2], which decomposes the grains through dislocation accumulation and reorganization (polygonization). Several different kinds of SPD process for bulk materials are typically as equal-charmel angular pressing (ECAP) [3], high-pressure torsion (HPT) [4] and accumulative roll-bonding (ARB) [5]. One of the main motivations for such a push for the very small grain sizes stems from the expectation of unprecedented mechanical strength, as predicted by the well-known Hall-Petch relationship that projects a continuous rise of strength with decreasing grain size [6]. However, these ultra-high strength metals no longer have the high ductility typical of their conventional coarse-grained counterparts, because the undesirable inhomogeneous deformation on the microstructure level can lead to the early onset of failure, severely limiting the useful ductility [2]. Recently, the interesting strategies have been performed to increasing simultaneously the ductility and strength ofUFG pure copper and nanostructured alloys by Zhao et al [7, 8]. In a pure copper, a high ductility has been achieved without sacrificing strength by introducing a high density of pre-existing twins and a large fraction of high-angle grain boundaries. Their encouraging results trigger our motivation to obtain high strength and ductility from the commercially bulk material."

Jan 1, 2013

By Riyad N. Ahmad-Bita, Shadia J. Ikhmayies

"SnO2:F/CdS:In structures were prepared by the spray pyrolysis technique on glass substrates at a substrate temperature Ts = 450°C. NH4F and HF were both tried as the sources of fluorine in the precursor solution of SnO2:F. A comparison between the properties of structures obtained by using the two doping compounds was performed. X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmittance measurements were used to characterize the films. The structures prepared by using HF as a fluorine source were found to have more ordered crystal growth, larger grain size and sharper absorption edge. From the inspection of the first derivative of the absorbance it is expected that more interdiffusion on the SnO2:F/CdS:In interface takes place in the structures made by using HF. These results confirm that these films are better as forecontacts for CdS/CdTe solar cells.IntroductionThin film CdS/CdTe solar cells built in the superstrate geometry rely on transparent conducting oxides (TCOs) to make the front contact The investigation of combined CdS-TCO films has recently been developed owing to the great interest of better understanding the effect of these bilayers on the absorbers [1]. Usually SnO2 is utilized as a front contact for these solar cells. Optimizing the properties of the SnO2/CdS structures is an important step on the way to get high performance CdS/CdTe solar cells.There are different methods to prepare SnOz thin films, such as reactive sputtering [2], evaporation [3], chemical vapour deposition [3, 4], dip coating [5] and spray pyrolysis [6-9]. At the same time CdS thin films can be prepared by different techniques such as chemical bath deposition [10], thermal evaporation [11], screen printing [12] and spray pyrolysis [7, 13]. However, the spray pyrolysis technique is a very low cost and simple technique that enables intentional doping and getting large area and uniform thin films [14]. For these reasons it is choused to prepare SnOz and CdS thin films in this work. To improve the properties of these compound semiconductors, SnOz was doped with fluorine and CdS was doped with indium where such doping is well known for these compounds."

Jan 1, 2012

By Shadia J. Ikhmayies

"Nanocrystalline fluorine doped tin oxide (Sn02:F) thin films were produced by the spray pyrolysis technique (SP) on glass substrates at a substrate temperature T, = 450 ° C. The hydrated stannous chloride (SnClz.2H20) was used as a precursor and ammonium fluoride (NH4F) and hydrofluoric acid (HF) were used as the doping compounds. A comparison between the compositional, morphological and optical properties of the films obtained by using the two doping compounds was performed by using scanning electron microscope (SEM) observations, energy dispersive spectroscopy by X-rays (EDAX) and transmittance measurements. It is found that the films prepared by using HF have larger grain size, and higher fluorine content than the films prepared by using ~- In addition these films have higher transmittance and higher direct optical bandgap energy. These results are interesting for the use of Sn02:F as a forecontact in CdS/CdTe solar cells.IntroductionTin dioxide is an n-type, wide bandgap semiconductor (about 3.5 eV) and in the form of thin films, it is a transparent conducting material, characterized by high optical transmission (80- 90%) [l]. Sn02:F is the most widely used transparent-conducting oxide material. The transparent-conducting thin films of this oxide are used as electrodes in a variety of optoelectronic devices, as heat mirror coatings in 'smart windows' for buildings, in automobile and airplane windshields, in incandescent light bulbs, in flat-plate and concentrating solar collectors. Tin oxide and zinc oxide, in thin film configuration are technologically important materials because of their applications in photovoltaic cells [2].Among various dopants for Sn02, fluorine is often preferred, because fluorine doping results in films with high transparency and good conductivity [3]. By exploring the literatures, it was found that different sources of fluorine were used to produce Sn02:F thin fihns, among which are ammonium fluoride (NH4F) and hydrofluoric acid (HF) are the most used. Some researchers used~ [2, 4-7] and others used HF [3, 6-8] for doping Sn02 films. Gordillo et al.[7] used both of NH4F and HF and showed that the resistivity of thin films obtained by using HF was lower than that of similar films obtained by using NH4F by a factor of 2.2. They also found that the films obtained by using HF have more random orientations."

Jan 1, 2013

By Ahmadzadegan. Arash, Anil Saigal, Michael A. Zimmerman

"In this study, the rheology of liquid crystalline polymer (LCP) melts through simplified 2-D and 3-D die geometries is simulated using Polyflow™. It is known that rheological properties of LCPs are close to long chain polymers and their directionality is close to those of small molecule liquid crystals (SMLCs). As a result, different rheological models (both viscoelastic and generalized Newtonian) for long chain polymers in Polyflow™ were investigated based on the available capillary rheometer data. By varying the parameters in these models, it is possible to adjust the effect of shear viscosity, normal stress differences and relaxations times on the rheology of the polymer. The free surface of the extrudate coming out of the die is simulated and the amount of die swell for different types of rheological models is compared. This study indicates that the Bird-Carreau model best applies to thermotropic LCP materials as quantified by die swell. Since the rheology of the LCPs affects the orientation of the crystals, the result of this simulation can be further used to predict the orientation of crystallines inside and outside the die.IntroductionAny rod like molecule or crystal tends to orient itself in the direction of shear as it moves within a flow. Since polymers consist of long chains of molecules, they experience the same phenomena when flowing in the melt condition. For most polymers, the molecules change direction and distribute uniformly in space during the solidification. However due to the higher inertia of the crystals in the liquid crystalline polymers, the oriented crystals will keep their order during the solidification and as a result the final product will show anisotropy in material properties."

Jan 1, 2012

By T. J. Weitz, J. E. Micheletti

"Pegasus Gold's Beal Mountain Mine is located near the Continental Divide, SW Montana. Conventional surface mining utilizes crushing, heap-leaching, carbon absorption/desorption, electrowinning and refining to produce approximately 60,000 oz gold annually. A leach pad sits at 2,300 meters (7,500 ft) elevation. Winters are long and cold with average snow accumulations ofl-2 meters; temperatures fall below minus 40'C and wind chill temperatures below 70°C. The Beal Mountain staff has developed special tools and procedures for burying drip emitter lines, and managing the heap and process solutions to allow for uninterrupted gold recovery during the winter season. Management of water balance and spring runoff is critical to the operations' success, due to mountainous terrain, high precipitation and proximity to a fishery and elk herd. The mine has an extensive network of land application disposal (LAD) and stormwater control systems to assure environmental protection and regulatory compliance.ABSTRACT ONLY"

Jan 1, 1997

By Ray D. Peterson, Garry G. Blagg

"Molten aluminum is routinely transported hundreds of miles to customers in large ""over-the-road"" crucibles. This is especially common for aluminum recycling organizations handling scrap and by-products. Receiving the aluminum in a molten form can save the customer time and money since in-house melting costs and capital equipment can be avoided. Additionally, the alloy can be on specification and nearly ready to use for the casting operation.A number of transport crucible designs are currently in use. The specifics of each design are based on the needs of the customer, the equipment used at both the producer and the consumer, and over-the-road transportation constraints. Crucibles are designed to maximize carrying capacity, and refractory life while minimizing heat flow and dead weight. These conflicting demands place difficult design criteria on the design engineer.This paper will review the basic advantages and disadvantages associated with molten metal transport, give examples of the design restrictions and examine several types design of crucibles currently in use."

Jan 1, 2000