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By W. F. Drinkard

Many in the environmental movement have focused on this element. But, nothing they or anyone does will change the amount of arsenic in the world. This report is on actual commercial plants that we developed and operated to recover or stabilize arsenic values from metallurgical dusts from gold and copper pyro operations and arsenical gold bearing ores. When they were available gold and copper values were recovered. Our experience in arsenic extends over thirty years. My first corporation, Mineral Research & Development Corporation was the first in North America to manufacture the then new CCA (copper-chrome-arsenic) wood preservatives. This class of wood preservatives proved to be so effective that it made wood into an entirely new material of construction. It is not uncommon for wood properly treated with arsenical CCA preservatives to last for thirty; forty, and sixty years. Over a hundred years have been projected in some field tests. Hundreds of thousands of trees have been saved. Millions more trees would have been saved had environmentalists not decided that their arsenic phobia was more important than trees. There are several variations of CCA. The most popular is CCA-C. Its formula is: CrO3 . . . . . . . . . . . . . . . . . . . 47.5% CuO . . . . . . . . . . . . . . . . . . . 18.5% As2O5 . . . . . . . . . . . . . . . . . 34.0% Until recent restrictions were placed on the consumption of arsenical wood preservatives, annual consumption in North America was about 150,000,000 lbs./yr. About 64,500,000 of arsenic as the pentoxide was safely consumed this way. World CCA consumption has been about double the above figures or 300,000,000 lbs. as 100% CCA and 129,000,000 lbs/yr as As2O5. Close to 100% of all the arsenic used in wood preservatives is derived from gold or copper processing. The valence of arsenic required for CCA wood preservatives and many other markets is the same valence that is required for stabilization. The economic challenge is how to get there. We have built and operated eleven plants to oxidize arsenic trioxide to its pentavalent form. Most of these have been classic in that they used a common oxidants such as hydrogen peroxide or nitric acid to achieve this.

Jan 1, 2005

By Beatriz Ribeiro Nogueira, Vijaya Kumar Rangari, Esperidiana A. B. Moura, Anne Chinellat, Arifa Parveen, Angel Visentim Ortiz

"Composite consisting of ethylene vinyl alcohol (EVOH) with short piassava fibers were prepared by extrusion process and their thermal and morphological behavior were investigated. The EVOH reinforced with 5 and 10 % of pi as sa va (Attaleafunifera Mart) fiber particle, based on the percentage weight ratio (wt %), untreated and treated with a commercial silane coupling agent, were prepared and the influence of fiber loading and the effect of chemical treatment on their thermal and morphological behavior were evaluated by SEM, DSC and TG analyses. Melt flow index (MFI) of the composites have been determined to evaluate the effects of fiber reinforcement on dynamic viscoelastic melt of the EVOH. In addition, piassava fibers characterization by SEM, FTIR, and organic and inorganic composition have also been carried out. The SEM results of the composites showed surface micrographs without microvoids and a good distribution, dispersion and compatibility between the fillers and the EVOH matrix. Concerning the piassava fibers characterization, the results showed that piassava has higher lignin content than cellulose and hemicelluloses, and around 0.7 % of ash with 52 % of silica (Si02). This high concentration of silica is consistent with the SEM analysis of the fiber that showed a large amount of ""silica rings"" encrusted on their surface.IntroductionLately, great worldwide interest has arisen in developing new technologies that enable the use of products with less environmental impact. Effort has been put into seeking natural modifier applications, particularly regarding the use of natural fibers. Special attention has been given to the use of natural vegetable fibers, because of the huge variety of species available. Such vegetable fibers are usually referred to as lignocellulosic materials [1]. This work evaluated the effects of piassava (Attalea funifera Mart.) fiber incorporation in an ethylene and vinyl alcohol copolymer (EVOH). The EVOH belongs to a family of copolymers with excellent gas barrier properties and resistance to organic compounds, which allow its application in different segments, from food packaging to gas tanks. However, EVOH is very sensitive to moisture, and in conditions of high humidity its gas barrier properties, thermal and mechanical properties are affected."

Jan 1, 2012

By M. Fafard, R. Ahmed, O. Dion-Martin

"The optimization of aluminum sheet and tube forming needs the use of large strain finite elements software. The precision of the predicted results from those simulations depends mainly on the quality of constitutive law of the material used. In order to improve quality of these simulations, Barlat has suggested a new yield function named YLD2000-2d. This criterion describes the anisotropic behavior of the rolled aluminum plates. This work consists of characterizing the AA5754 alloy and estimating the material parameters needed for the YLD2000-2d criterion in LS-DYNA. In order to get these parameters, various mechanical testing were performed such as bulge and tensile tests. Moreover, the bulge test was also used to obtain an estimation of work hardening curve in large strain condition, up to 50%. The objective of this paper is to share the experimental results of the characterization of AA5754 aluminum alloy.IntroductionResearchers from National Research Council Canada's Aluminium Technology Center (NRCATC) and Aluminium Research Centre - REGAL, are working on aluminium tube hydroforming processes of AA-5754-0 alloy, used in automotive industries. Hydroforming process presents several difficulties such as wall thinning and section changes. In order to control them, some parameters can be set during the process like pressure rate and end feed level [1]. Given the complexity of the parts and the variability of the control parameters, the use of finite element method (FEA), like LS-DYNA, based on large strain theory is thus necessary. The accuracy of predicted results depends mainly on the quality of the constitutive law used to model the behavior of material. FEA results seem to be valid with the von Mises yield criterion used in some cases. But, given the anisotropic properties of the AA-5754 alloy, a more appropriate criterion could be used. The *MAT_ BARLAT YLD2000 shell material criterion, developed by Barlat [2], who's taking into account the anisotropic behaviour, was chosen due to its large flexibility and its good adaptation to particular elastoplastic behavior of aluminum. However, the use of this criterion needs to determine some material parameters by experimental way."

Jan 1, 2013

By Viktor Mukhin

"Among the methods proposed for spent activated carbon regeneration, the most acceptable is, thermal reactivation, because in this case the existing equipment for manufacture of activated carbon can be adapted for this purpose.In order to conduct the process of thermal re-activation of spent activated carbon directly at gold mills, a fullscale drum-type furnace with external electric heating has been developed, i.e. EPV-300 model with a throughput rate of 50 to 120 kg/hour. Its use ensures restoration of the adsorption properties of carbon up to the level of fresh activated carbon with an insignificant (by 0.7%) decrease in strength and with a high (95% to 97%) yield of reactivated carbon.During the recent years, activated powder carbon has been extensively used in flotation processes for treating polymetallic ores at ore treating plants to improve recoveries of main metals (copper, lead, nickel, etc.).Especially large volumes of activated powder carbon are used at the Talnakh concentrator of the Norilsk Mining and Metallurgical Complex in Russia for absorption of residual flotation reagents from recycled water in order to ensure efficient selective separation of minerals with similar physical and chemical properties.IntroductionSorption technology based on active carbons use starts being applied in such an important in the widest sense of the word strategical branch of economics as non-ferrous metallurgy. Thus since the middle ninetieth Russian gold extraction industry began to apply widely the processes of sorption from pulps and solutions by means of high-resistant granulated active carbons. That provided the start of gold ore minefield exploration, increasing of gold extraction from the ore and reducing its loss with the ""tails"" of process. At present more than 40% of Russian gold is extracted with the help of sorption technologies [1].Another field of active carbons application in non-ferrous metallurgy is the processes of non-ferrous ores floatation at ore-mining and processing enterprise. For that purpose powdered (less than l00µm) active carbons are used for providing the effective selection of minerals with similar physicochemical properties. This method not only increases the metal extraction level but provides deeper division of them."

Jan 1, 2008

"Mineral flotation processes are often characterized by long dead times and slow process dynamics. The process dynamics change due to different ore types, feed grades and circulating loads. These are some of the factors that can make control of flotation processes difficult. Implementation of adaptive control algorithms at Brunswick Mining has made controlling these processes feasible. The role of adaptive controllers in plant optimization and the overall control philosophy is discussed.IntroductionBrunswick Mining is located just outside of Bathurst, New Brunswick, Canada. The concentrator processes approximately 10,250 tonnes per day of ore that assays at approximately 8.9 %Zn, 3.6 %Pb, 0.3 %Cu and 100 gram/tonne of Ag. The four products produced are zinc concentrate assaying 51 %Zn, lead concentrate assaying 36 %Pb, copper concentrate assaying 21 %Cu, and a bulk concentrate assaying 32 %Zn and 18 %Pb.The original flotation process control system, supplied by Outokompu Oy of Finland, was replaced in the summer of 1988 by a Provox system supplied by Fisher Controls Inc. The Provox system consists of two redundant integrated function controllers (IFC's), two operator console stations with two screens each and a Digital Equipment Co. microVax II computer running Fisher's Computer Highway Interface Package (CHIP).In January 1989 a boiler management package, which includes the boiler control hardware and another operator's console, will be added to the Provox system. In late spring of 1989, a Vax 3200 computer running G2 artificial intelligence software from Gensym Corporation will be installed. These devices are all connected using a redundant data highway that runs around the plant.The primary measurement devices in the flotation circuit are two Courier on-stream X-ray analyzers. The Courier systems each have 14 sample cells with two streams multiplexed into each cell. Each pass of the on-stream head takes approximately 6 minutes yielding a nominal sampling interval of 12 minutes. The Courier passes its assays to its respective IFC. The IFC handles the digital and analog I/O, DDC and cascade loop control, some low level calculations and sequencing. The CHIP microVax has 9MB of memory and 220MB of mass storage running under the VMS operating system. The CHIP microVax is a central database for the Provox system. It is used for data trending, metallurgical modelling and balancing, instrumentation database, long term storage, and on-line adaptive assay control."

Jan 1, 1989

By Kenji Morinaga, Shigeru Fujino

"Preparation and vacuum ultraviolet (VUV) transmission spectra of aluminum fluoroberyllate glasses, MgF2-CaF2-SrF2-A1Fr BeF2 (MCSA-Be) and MgF2-CaF2-SrF2-AlFrYFrBeF2 (MCSAY-Be), were studied. The influence of YF3 and BeF2 on the thermal stabilization against crystallization and VUV transmittance was investigated. With increasing the BeF2 content, the crystallization tendency decreased and the absorption edge shifted to shorter wavelength in the MCSA-Be and MCSAY-Be glasses. The MCSA-20Be glass composition exhibited the shortest wavelength UV absorption edge (-147 nm) and the highest transmittance at 157 nm (60% for 2 mm sample thickness). The transmission values at 157 nm and the slope (steepness) of the absorption edge were found to be significantly influenced by the trace amount of Fe2+ derived from the BeF2 raw materials.IntroductionPure beryllium fluoride is known to be an only fluoride that forms one component glass on cooling from the molten state and is structurally similar to silica with [SiO4]4- tetrahedra. Molten BeF2 is highly viscous with a viscosity of about 106 poise near its liquidus temperature at 550""C[l]. The addition of modifying fluorides such as LiF, NaF or KF to BeF2 substantially decreases the viscosity[2]. Glass forming region of binary fluoroberyllate glasses has been mainly reported by several authors [3]. LiFBeF2 binary system is structually analogy for Mg0-Si02 system from their phase diagram and ratio of ionic radius for each cation and anion, respectively. LiF-BeF2 binary glasses seems to be promising candidates for the extreme deep vacuum ultraviolet (VUV) transmitting optical materials owing to their larger band gap. However, it is chemically unstable, and so, have no practical application for lens systems in micro lithography equipments and substrate materials for F2 (157nm) excimer laser[4]. There are also few reports on the VUV transparency of multicomponent aluminium fluoroberyllate glasses from the view point of their compositional dependencies. The purpose of this paper is to prepare deep VUV transmitting optical materials and determine the optimum glass compositions for aluminium fluoroberyllate glasses investigating their thermal stabilization against crystallization."

Jan 1, 2000

By C. B. Solnordal, R. N. Taylor

"The heat transfer conditions on the outer side of a Sirosmelt lance have been determined using experimental measurements in combination with a mathematical model. By measuring the temperature distribution along the wall of an operating Sirosmelt lance, as well as the thickness of the slag layer on it, it was possible to use the model to determine both the heat transfer coefficient between the vessel contents and the lance, as well as the effective thermal conductivity of the slag layer. The effective thermal conductivity of the slag layer was found to be within the range 0.7-1.3 W.m-1. ºCl, which was in good agreement with measured values for magnetite. The outside heat transfer coefficient varied from 80 to ISO W.m-2. ºC1, which was smaller than quoted in the literature for metal/slag systems. The discrepancy was attributed to the high thermal resistance experienced between the lance wall and the slag layer, as well as the large quantities of combustion gases that envelop the lance tip and reduce convection and conduction from the melt to the lance. INTRODUCTIONThe Sirosmelt submerged combustion smelting process [1] utilizes top injection lances to deliver fuel and air into a metallurgical melt. To help prevent lance failure from attack by liquid slag, helical vane swirlers are used within the annular lance to impart swirl to the flowing air and enhance the heat transfer from the lance wall to the air. The swirlers thus cool the wall, and enable a frozen layer of slag to form on its outer surface. This solid layer ensures liquid slag cannot reach the lance surface, and the lance is protected.A mathematical model of the heat transfer processes associated with the lance has been developed, which combines heat balance equations with engineering correlations to predict the wall and cooling air temperature of the lance, as well as the air pressure distribution. An account of the model was given by Rankin et al. [2]. To further enhance the model and enable it to predict the thickness of slag accumulating on the lance, a detailed analysis of the heat flow through the slag layer commenced in 1992. By far the most complex aspect of the model, the flow of heat from the vessel contents to the outside of the lance was dependent on many factors, including:-"

Jan 1, 1996

By Qixing Yang, Björn Haase, Fredrik Engström, Anita Wedholm

"MiMeR, the Minerals and Metals Recycling Research Centre at Luleå University of Technology, Sweden, started industry-related research work to stabilize an EAF slag from Höganäs AB with of CaO/SiO2 values near to 3.2. The intention was to determine the suitability of the EAF slag as construction material after stabilization. Some of the stabilizers effective for preventing disintegration of AOD slag were examined in laboratory tests for stabilization of the EAF slag. The EAF slag samples were mixed together with stabilizers for melting at 1600ºC and then cooling in a crucible system. With a laboratory granulation system, the liquid EAF slag was cooled rapidly using air. Samples from the tests were characterized by different techniques, including XRD and SEM. Some of the results from the work may be useful for preventing slag disintegration and, thus, enhancing utilization of the EAF slag as construction material, thereby saving valuable natural resources.IntroductionAt steel plants of some MiMeR member companies, steel grades with low carbon contents were produced in Electric Arc Furnaces (EAF). EAF slag was tapped out of the furnace to slag pots for transport to slag yards, where the slag was poured on the ground. Very often, the EAF slag disintegrated during cooling on the ground. Fines from the slag disintegration were often difficult to handle and use as material for road construction [1, 2]. The EAF slag disintegration was rather similar to the disintegration occurring in the slag tapped from some AOD (Argon Oxygen Decarburization) converter heats.Literature studies show that formation of dicalcium silicate (C2S) is the main reason for the disintegration or dusting of AOD slag from production of stainless steel [1-4]. The C2S can form while the content ratio of CaO to SiO2 of the slag, CaO/SiO2, exceeds 1.4 [1]. Values of CaO/SiO2 for the AOD slag are often near to 2.0, making the C2S a predominant slag component. The ß phase of C2S, ß-C2S, transforms into its low temperature ? form in the temperature range of 400-500°C, inducing a volume expansion of nearly 12% [1-4]. The volume expansion disintegrates the AOD slag."

Jan 1, 2008

By Philip L. Sibrell

A new process utilizing pulsed fluidized limestone beds was tested for the remediation of acid mine drainage at the Friendship Hill National Historic Site, in southwestern Pennsylvania. A 230 liter-per-minute treatment system was constructed and operated over a fourteen-month period from June 2000 through September 2001. Over this period of time, 50,000 metric tons of limestone were used to treat 50 million liters of water. The influent water pH was 2.5 and acidity was 1000 mg/L as CaCO3. Despite the high potential for armoring at the site, effluent pH during normal plant operation ranged from 5.7 to 7.8 and averaged 6.8. As a result of the high influent acidity, sufficient CO2 was generated and recycled to provide a net alkaline discharge with about 50 mg/L as CaCO3 alkalinity. Additions of commercial CO2 increased effluent alkalinity to as high as 300 mg/L, and could be a useful process management tool for transient high flows or acidities. Metal removal rates were 95% for aluminum (60 mg/L in influent), 50 to 90% for iron (Fe), depending on the ratio of ferrous to ferric iron, which varied seasonally (200 mg/L in influent), and <10% of manganese (Mn) (10 mg/L in influent). Ferrous iron and Mn removal was incomplete because of the high pH required for precipitation of these species. Iron removal could be improved by increased aeration following neutralization, and Mn removal could be effected by a post treatment passive settling/oxidation pond. Metal hydroxide sludges were settled in settling tanks, and then hauled from the site for aesthetic purposes. Over 450 metric tons of sludge were removed from the water over the life of the project. The dried sludge was tested by the Toxicity Characteristics Leaching Protocol (TCLP) and was found to be non-hazardous. Treatment costs were $43,000 per year and $1.08 per m3, but could be decreased to $22,000 and $0.51 per m3 by decreasing labor use and by on-site sludge handling. These results confirm the utility of the new process in treatment of acid impaired waters that were previously not amenable to low cost limestone treatment.

Jan 1, 2003

By P. S. Dunn, A. D. Rollett, H. D. Lewis

"The results of preliminary work on the modeling and measurement of the heat transfer coefficients of metal/mold interfaces is reported. The system investigated is the casting of uranium in graphite molds. The motivation for the work is primarily to improve the accuracy of process modeling of prototype mold designs at the Los Alamos Foundry. The evolution in design of a suitable mold for unidirectional solidification is described, illustrating the value of simulating mold designs prior to use. Experiment indicated a heat transfer coefficient of 2 kW/m /K both with and without superheat. It was possible to distinguish between solidification due to the mold and that due to radiative heat loss. This permitted an experimental estimate of the emissivity, ~ = 0.2, of the solidified metal.IntroductionA feature that distinguishes casting processes from welding processes is the presence of an interface with a low heat transfer coefficient between the mold and the casting. Especially when chill casting, the interface delays the start of solidification and increases freezing times significantly. By comparison welds can be assumed to have a very high heat transfer coefficient. The heat transfer coefficient controls such phenomena as folds and laps on the surface of castings which can be crucial to the acceptability of a casting. The time delay for the start of solidification influences the occurrence of cold shut defects. The standard mold material for uranium casting is high quality graphite which is an excellent refractory when used in vacuum and coated with a refractory wash. Graphite is an effective chill material and has a thermal diffusivity approximately twice that of uranium. Experience has shown that practicable superheat without mold pre-heat is not sufficient for avoiding cold shut defects when casting in graphite molds.TheoryIt is possible to calculate the position of the freeze front s, as a function of time, t, the superheat and interface heat transfer coefficient, h, [1]. However, the value of h cannot be obtained explicitly. The Virtual Adjunct Method (VAM) [2] offers a method for extending the standard equation for an insulating mold where s is proportional to the square root of time. By considering the effect of the interface to be equivalent to finite thicknesses of mold and metal, the following quadratic equation is obtained,"

Jan 1, 1986

By Robert Fritzsch, Ragnhild E. Aune, Mark William Kennedy, Behzad Mirzaei

"The quantitative particle concentration can give important information about the cleanliness of melts for quality control in primary and secondary production of aluminum. Manual quantification of the particle concentration is normally a time consuming process and human control can bias the acquired images and particle count.The present paper explains the automated image-processing steps for the quantification of SiC-particles, with equivalent diameters from 2 to 25 µm, in solidified A356. A total of 700 micrographs, acquired with a standard white light microscope with 10 x magnification, were analyzed. The applied software (Image Pro-Plus 7.0 from MediaCybemetics®) allows for programming of macros which in tum provides the user with a higher degree of control. The automated results are compared with the results obtained by manually counting the particles in the same micrographs. The impact of the automated results on the estimated filtration efficiency was established to be only -3%.IntroductionInclusions are both indigenous and exogenous particulates that are present in commercial metals such as aluminum. If large individual or large numbers of inclusions are present, they can have a significant negative impact on the appearance, mechanical and chemical behavior of products produced from the metal. Aluminum is known to contain large numbers of inclusions: =50 µm in size, e.g. typically <l ppm by volume or <100,000 inclusions of>20 µm per kg of metal as detectable using a Liquid Metal Cleanliness Analyzer, LiMCA [1]. Depending on the final application of the aluminum, inclusions can render the metal 'not fit for purpose', and result in serious economic consequences to metal producers.It is not surprising that the aluminum industry has developed a number of treatment processes to improve metal cleanliness, given the large number of high value products whose quality can be adversely affected by inclusions. CFFs are the most commonly applied filtration process and have been used to filter >50% of the world production of aluminum since the 1990's [2].Inclusions in aluminum may be particles, bifilms [3] or clusters of: oxides (Al2O3 , SiO2), spinels (MgO· Al2O3), carbides (SiC, Al4C3), nitrides (AlN), borides (TiB2), sulfides, phosphides and intermetallics [ 4]."

Jan 1, 2013

By Tugba Basargan Çagatay Morall, Gülhayat Nasun-Saygili

"The aim of this study is to prepare the apatitic material using colemanite mineral (2CaO.3B2O3.5H2O) which was obtained from Eastern Anatolia, Turkey. For this purpose, colemanite mineral was reacted with different phosphate sources, namely, dipotassiumhydrogen phosphate, ammoniumhydrogen phosphate and ortophosphoric acid at various temperatures and time periods. Experiments were run in batch system. The apatitic material was prepared by a wet method and followed by heat treatment at various temperatures. Structure of the samples was analyzed by XRD, FTIR, XRF and SEM. The particle size analysis was also made for the result product. The experiments showed that reaction temperature, contact time and heating temperature are important parameters to transform the colemanite into apatitic structure. Reaction of colemanite with dipotassiumhydrogen phosphate and ammoniumhydrogen phosphate results in amorphous, non-stoichiometric hydroxyapatite type structure, while acid based phosphate source gives brushite and monetite type product before and after heat treatment, respectively.IntroductionBoron which has properties intermediate between metals and non-metals is a member of semiconductor group of elements. Its atom is very small and has three valence electrons. Boron exists in Earth's crust (from 5 mg/kg in basalts to 100 mg/kg in shale) and in the oceans (4.5 mg/l) [1]. Turkey has 60% of world's boron reserves which is mostly in the form of colemanite (2Ca0.3B203.5H20). Colemanite is the most important calcium containing commercial borate mineral with 5 mol of crystal water [2].Calcium phosphate cements are very useful for bone repair applications because of its chemical structure. They are injectable, easy to shape and can be maintained locally. Because of those reasons calcium phosphate cements are very effective to fill bone defects with an irregular shape [3]. Hydroxyapatite (Ca10(PO)6(OHh) is the major component of the bone (70 wt%). However, hydroxyapatite stoichiometry, composition and crystallinity differ in human skeleton system [4, 5].The main objective of the present work was to study the transformation of colemanite to apatitic material using different phosphate solutions at several time spans and temperatures. The experiments were run in a batch system, change in pH and also weight loss were measured after the experiments. Several analysis methods were used to investigate the chemical and structural changes."

Jan 1, 2012

By Cheng Gong-jin, Chu Man-sheng, Liu Zheng-gen, Zhang Yong, Liu Jian-xing, Xue Xiang-xin

"High chromium vanadium-titanium magnetite is one kind of Fe-V-Ti-Cr composite ore resources, which owes high utilization value. Owing to lacking systematic study on the sintering of this ore home and abroad, effects of carbon addition and basicity on sintering process and sinter metallurgical properties, such as sinter yield, vertical sintering speed, tumbler strength, sinter machine utilization coefficient, and low temperature reduction degradation were investigated systematically under laboratory conditions in the paper. The results shows that, when high chromium vanadium-titanium magnetite proportion is kept unchanged as 13% in sintering feeds, sintering process index and metallurgical properties are the optimum under carbon addition 5.0% and basicity 2.70, which meets the requirements of blast furnace burdens. This research provides technical parameters for practical sintering production of high chromium vanadium-titanium magnetite.IntroductionHigh chromium vanadium-titanium magnetite (hereinafter abbreviated as hi§h-Cr V-Ti magnetite), in which Fe is closely symbiotic with Ti and isomorphous with V and Cr1'- l, is one kind of typical vanadium-titanium magnetite resources with high comprehensive utilization value but the difficulties are extremely high due to complex chemical composition and mineral structure. At present, the feasible and mainstream utilization process of high-Cr V-Ti magnetite should be the route of agglomeration-blast furnace smelting. Thus, sintering production is the foundation for high-Cr V-Ti magnetite utilization. However, till now there are few research documentations on high-Cr V-Ti magnetite sintering home and abroad. Under the above background, this study focused on detailed researches of high-Cr V-Ti magnetite sintering. Sintering process uses the powders or fine iron ores to produce artificial rich ore with good metallurgical properties 4l Solid fuel provides 90% heat requirement during sintering15J. The appropriate amount of fuel and flux should be added during sintering in order to provide necessary heat and maintain the desired basicity16l. That is to say, carbon addition and basicity are two key factors affecting metallurgical properties of sintering products17J. Therefore, the effects of carbon addition and basicity on sintering process and metallurgical properties, including sinter yield, vertical sintering speed, tumbler strength, sinter machine utilization coefficient, and low temperature reduction degradation, are systemically investigated under laboratory conditions in the study, on purpose to achieve the optimization of sintering process for high-Cr V-Ti magnetite."

Jan 1, 2013

By Maria Kuttig, Christian Ruback, Gerhard Tober, Petra Maier

"It has been demonstrated that there is a strong relationship between work hardening with various post heat treatment and cyclic deformation behavior of structural steel S275. This study contributes to a project developing a process for the complex forming of steel, which combines rolling and bending. Due to the complex geometry of the final work piece, the deformation degree varies greatly. The forming temperature, as well as post heat treatruent, influences recrystallization processes in dependence of the local deformation degree, resulting in inhomogeneous microstructure of the work piece, which affects the quasi-static and dynamic properties. Cyclic creep and hardening or softening has been monitored during constant amplitude loading at stresses near fatigue strength in normalized condition. Work hardening, stress relief or recrystallization influence the cyclic deformation behavior and produces cyclic creep effects. Cyclic softening or hardening and creep were observed to occur in parallel. To what extent these properties are noted depends on the deformation degree.IntroductionThis work is part of a research project developing a new process for the three dimensional forming of steel. For the final product the fatigue strength influenced by the forming parameters is very important. Due to its complex geometry, the formed final plate has different deformation degrees. This leads to different recrystallization behavior and heat treatruent will have different effects on the microstructure. The peak deformation degree cp of the plate will be around -0.5 what leads to the analysis using rolling from 22 mm to 13 mm of thickness. The quasi-static material properties are very important for calculating the preliminary design. However, work pieces which are cyclic loaded need fatigue tests to describe the in-service material behavior. [l] For the prediction and to guarantee the wanted life-time of the part cyclic deformation tests are important. [2, p.23-32] When it is assumed that the work piece will only loaded in cyclic tension, fatigue testing will be done from zero to a maximum force value. In preliminary tests this value is the tensile fatigue strength from a Smith diagram. During processing, here forming, work hardening takes place resulting in strengthening. Therefore, in further tests maximum load can be increased to monitor cyclic deformation mechanism in more detail. However, to study cyclic creep and hardening and softening data should be evaluate over sufficient life time and should not fracture too soon."

Jan 1, 2013

By Reuben John Mathew

"Oxygen evolution is the main anode reaction in industrial copper electrowinning. The oxygen bubbles do not conduct electricity, thus increasing the electrolyte resistance. The oxygen bubbles formed at the anode rise to the surface, occupying a larger volume of the electrolyte at the top of the cell than at the bottom. This oxygen bubble concentration gradient contributes to a gradient in electrolyte resistance and consequently a tendency toward uneven current distribution. This phenomenon increases the chance for uneven growth on the cathode and/or short-circuits, particularly on the lower portions of the cathode. This issue may be ameliorated by increasing the charge transfer resistance for oxygen evolution down the height of the anode. This concept was studied by solving the current distribution for a 2-D model of a copper electrowinning cell using COMSOL.IntroductionA copper electrowinning tankhouse aims to operate at the highest current density that will deposit on the cathode a layer of copper metal possessing the desired physical and chemical characteristics. The operating current density is directly related to the physical nature of the copper deposit on the cathode (Figure 1), limiting a copper electrowinning tankhouse to some operating current density that produces acceptable copper deposits.[!] The ratio of the operating current density to the limiting current density is typically around 0.3.[2] If the limiting current density for a cell could be raised, the operating current density could also be raised and thus result in savings in capital cost for a tankhouse. [3]The average operating current density in a copper electrowinning plant is 270A·m- 2 .[4] The value for average current density, however, obscures the fact that the face of a cathode does not experience this value equally. Indeed, the current density varies along the height of an electrode and is independent of the height of the electrode.[5] This phenomenon partly explains why the lower portions of a cathode tend to display a rougher copper deposit.In order to utilize a higher operating current density but still remain at 30% of the limiting current density, the limiting current density must be raised, but it is affected by the mass transfer regime at the electrodes. The mass transfer regime is currently poorest at the lower portions of the cathode and this is part of the reason for the tendency for poor cathode deposits to occur at the lower portion of the cathode.[6]"

Jan 1, 2012

By A. V. Tarasov

In order to improve technical, economic and environmental performance of hydrometallurgical processing of intermediate products containing copper and nickel, the Gintsvetmet Institute and the IMET Institute of the Russian Academy of Sciences have conducted studies into the efficiency of the use of alternating current of industrial frequency on processes applied for hydrochemical leaching of various copper- and nickel-containing materials. It has been found that: 1.Imposition of alternating current over the process of leaching of softly reduced nickel oxide with recycled copper sulfate solutions resulted in an increase by 20 to 30% of the rate of the copper cementation process and reduced by 20% its activation energy. At the same time, the recoveries of nickel, cobalt and iron to the leach solution increased up to 82.2%, 78.5% and 57.1%, respectively, and that of copper to the cement precipitate up to 74%. Optimal process conditions have been identified with respect to the current density, electrode material, copper concentration in solutions and the process temperature. 2.In the process of hydroelectrochemical sulfuric acid leaching of nickel and copper sulfides, the grain size, the phase form of sulfides, the solution composition (H2SO4, Cl?, Cu2+, Fe3+)and the current amperage had an effect on the nickel recovery to the solution, which reached 90%, while the degree of copper transfer to solution did not exceed 20%. The process of hydroelectrochemical sulfuric acid leaching of nickel and copper sulfides with an addition of Cl? made it possible to selectively recover nickel into the leach solution along with concentrating copper in the leach residue. 3.When subjecting samples of commercial-grade magnetic fractions of converter matte to sulfuric acid leaching, the imposition of electric current, the concentrations of sulfuric acid and chloride ion in the solution and the duration of the reaction process had an effect on the process. The nickel recovery was 85% and that of cobalt and iron was 95% and the recoveries reached 97.5%, 98.3% and 99.8% as a result of repeated treatment of the primary residue under similar process conditions. Up to 75% of copper, 75% of sulfur and 99.0-99.5% of palladium was concentrated in the solid reach residues. The experimental data obtained indicates that the use of AC for hydroelectrochemical sulfuric acid leaching for separation of copper- and nickel-containing intermediate products has favorable prospects.

Jan 1, 2003

By Vladimir Lobanov, Vladimir Skorohodov, Boris Radionov, Olga Makovskaya

"The synthetic sorbents and the activated carbons which are used for the metals extraction from weak process liquors are rather expensive. It is propose to use mineral and synthetic high-porous substances which sharply increased sorption properties by special processing. For achievement the desirable properties sorbents are impregnated by specially prepared solutions. Such solutions should contain the substances or its anionic forms which on the one hand are strong enough fixed in a supporter pores, with another are capable to form the insoluble compounds with extracting metals. Selectivity is provided by chemism of the reagent interactions with extracting metal. Due to the high concentration of a reacting ion in a sorbent phase the capacity and rate of sorption increases. Formed insoluble compound remains in a phase of the sorbent and necessity of its filtration disappears. For synthesis the sulfhydryl compounds which chemical properties allow to increase degree of extraction and capacity of the activated carbon were used. At hydrometallurgical processing of precious metals mineral raw materials the commercial solutions with the concentration of gold from 0,1 to 5 mg/dm3 are received. Commonly gold is precipitated from cyanic solutions by the zinc dust. The sorption methods are widely applicable. But the synthetic sorbents and the activated carbon using to these purposes are rather expensive. Expenses for sorbents even at its regeneration can reach 10-15 % from total expenses of gold extraction from ores. When sorbent regeneration, mostly for carbon, is not provided, this share increases to 30-40 %. Thereupon search of the sorbents combining availability, the sufficient capacity, demanded degree of extraction and the low price is actual. For the specified purpose it is offered to use the mineral and synthetic high-porous materials which sorption properties are sharply rose by special treatment. Among such substances are natural zeolites, silica gel, lignine et al. Similar treatment can improve the sorption properties of sorbents used in practice, particularly, the activated carbons. The simplest treatment of potential sorbents consists in its impregnation by specially prepared solutions. Such solutions should contain substances or its anionic forms - impregnating agents. These agents should be on the one hand strong enough fixed in a carrier pores, on the other hand are capable to form with extracting metals insoluble compounds. The more strong compounds are formed the high degree of metals extraction from solutions. The sorbents with similarly changed properties are named the impregnated sorbents."

Jan 1, 2008

By Dirce H. Jacomo, Jaciele G. Teixeira, Anibal Y. Abreu Castillo, EsperidianaA. B. Moura, Yalquiria A. Silva, Rene R. Oliveira, Michelle G. Gomes

"Composites consisting of poly(vinyl alcohol), starch and sugarcane bagasse ashes, using glycerol as plasticizer agent, were prepared by solution casting method. Composites prepared were subjected to electron-beam radiation treatments, at radiation dose of 50 and 80 kGy using a Dynamitron electron beam accelerator, at room temperature in the presence of air. The composite samples obtained were evaluated for their water absorption, mechanical and morphological properties.1. IntroductionThe potential of biodegradable polymers and more specifically of biocomposites obtained from agro-resources have long been well established [1-3]. Starch, derivate from variety of botanical sources (cereals, legumes, and tubers) is widely available raw material and one of the most studied and promising agro-resources for the production of biodegradable polymers as matrices for biocomposite applications. However, starch itself is very brittle, hydrophilic and its mechanical properties are very poor for many applications [3 - 5]. The blending of starch with conventional polymers is a promising approach to improve its drawbacks. Recently, many efforts have been made to blend starch with biodegradable synthetic polymers [5, 6]. Polyvinyl alcohol (PYA) is a particularly well-suited synthetic polymer for the formulation of blends with natural polymers, as it is highly polar and can also be manipulated in water solutions, and depending upon its grade, in functional organic solvents as well [3, 7]. PY A has been reported to be an option to blend with starch. Most of the starch/PY A composites have been prepared by casting. However, it is well known that starch/PY A composites has poor in water resistance and mechanical properties after absorbing water [3,8]. Attempts to improve the mechanical properties and to decrease the water absorption property of the starch/PY A composites are made by adding the cross-linkers and plasticizers. Park et al. prepared starch/PY A/citric acid films by the casting method. They also studied the effect of (spell out) citric acid on the mechanical properties and water resistance of composites [9]. Zhai et al. prepared the starch/PY A hydrogels using electron-beam radiation [10]. Different kinds of lignocellulosic fibers have been investigated in blends for formulation of biocomposites."

Jan 1, 2013

By Maria D. Salazar-Villalpando, Anthony Cugini, Bryan Reyes

"The electrochemical reduction of CO2 was performed in a laboratory-made, divided Htype cell. A copper electrode was used as the cathode. An Aldrich Nafion 117-type ion exchange membrane (0.18mm thickness) was used as the diaphragm. NaHCO3 and KHCO3 were studied as the catholytes. Hydrogen evolution from water reduction and products from CO2 electrochemical conversion were recorded. Higher CO2 reduction enhancement was observed by KHCO3 as compared to NaHCO3. The main conclusion of this work is that in fact CO2 can be electrochemically reduced with copper electrodes.1.-INTRODUCTIONThe direct electrochemical reduction of CO2 may allow for a simple process and, by avoiding high temperature reactors, would enable the process production rate to be quickly varied to follow the time of day availability of surplus electricity [1]. Temperature has a major effect on the electrochemical conversion of CO2 since its solubility increases when temperature decreases [2]. The electrical potential applied to the electrochemical reacting system will have an influence on the product distribution, as well. For example, a narrow potential range during cyclo-voltagraphic studies will determine the detection of a lower number of products. A recommended potential range to study the electrochemical reduction of CO2 is -2V to 2V. Moreover, the reaction rate on the electrode is governed by various processes, such as the kinetics of electron transfer, adsorption/desorption at the electrode surface, and diffusion of CO2 to the Cu electrode. The availability of active species, CO2 for electro-reduction, is extremely low at the vicinity of the electrode surface and it seriously interferes with the rate of mass transfer. In batch type electrolytic reactors, depletion of CO2 at the surface takes place first. CO2 from the bulk then has to diffuse to the electrode surface, resulting in mass transfer controlled kinetic phenomena. During the above process, several other competitive side reactions could suppress the primary reaction even though the cathode has good electro catalytic properties for reduction of carbon dioxide. When the dynamic supply of specific active species is ensured to electrode surface, the mass transfer effects are minimized to certain extent. Hence it is envisaged that a continuous flow reactor is more efficient for the electro-reduction of CO2 in CO2 saturated aqueous electrolytes. The primary reactions that occur at the copper electrode during the reduction of CO2 are listed below (with the standard potentials calculated using formation energies [1] :"

Jan 1, 2010

By Milton Manrique, Edgar E. Vidal, Patrick R. Taylor

"Ultrafine zirconium carbide powder has been synthesized using zircon concentrate and methane in a thermal plasma reactor. The effect of several experimental variables, such as power used and zircon particle size, on the conversion has been studied. A thermodynamic analysis of the possible reactions and stable compounds was performed. A mathematical model that describes the in-flight decomposition of zircon particles was developed based on a description of the temperature and velocity profiles calculated in the reactor. It was shown that the formation of zirconium carbide from zircon and methane is thermodynamically possible. Complete 'vaporization of zircon in the reactor is predicted when the particle size is below 45flm and the effective power entering the reactor is 15 kW. The powders were collected and characterized by XRD, SEM, TEM and chemical analysis using ICP. Results of the product analysis indicated the presence of zirconium carbide, zirconium oxide, silicon carbide and silicon oxide.IntroductionIn recent years there has been an increased interest in the production of nanometric sized powders of ceramic materials for use in advanced materials applications. One possible method to produce these powders is with a thermal plasma reactor, which offers high temperatures and fast quenching rates. This technology has been called - Thermal Plasma Synthesis - [1].Zirconium Carbide (ZrCx) has typical properties of transition metal carbides: elevated hardness - between alumina and diamond - a high melting temperature of 3420°C and high chemical stability at room temperature [2]. ZrCx has a Bl crystal structure with deficiencies in the number of carbon atoms in the cell with x between 0.6 and 1 [3]. Different methods have been used to produce ZrC, one method is by direct reaction of zirconium hydride or halide with carbon. Other methods used are direct reduction and carburization of zirconium oxide (Zr02) and reaction of metallic zirconium with a caburizing gas such as acetylene [3]. Recently small films of ZrC have been obtained using a sputtering device [4,5]. ZrC has been used in nuclear plants as a low neutron absorbing and high mechanical resistant refractory material and also as a constituent in cathodes made of UC-ZrC [6]. It is also used in the form of tubes, boats and crucibles to handle molten metals and as part of electronic devices used for thermoionic transducers. Recently ZrC has been used along with zirconium diboride (ZrB2) to produce composite materials [7,8]."

Jan 1, 1996