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By Krishna Kumar

"Growth of electronics waste (e-waste) and lack of appropriate disposal mechanism are the great concern for developing countries like India. The domestic generation of e-waste in India is rapidly growing with the development. The imported substance is also substantially contributing to the e-waste inventory. Recycling of e-waste is mainly carried out in unorganized units in India. The primitive recycling technique used by the unorganized sector is a great threat to the environment and the health of the operators involved in these profession. Therefore, improvement of technology used by these units towards a cost effective, environmental friendly alternative could be the solution to the present crisis. Few initiatives of recycling have, however, come up in recent years in organized units. The precious metals are still recycled in the developed countries. This report discusses the inventory, technology status, legal legislative and existing practices of e-waste management in India.1. INTRODUCTIONInnovation, research and development in the field of electronics and information and communication technology (ICT) lead to convenient, independent human life. Consumption of electronics and hardware products has enhanced by manifold. Electronics and hardware sectors have, thus, become the fastest growing sector in the world. Faster obsolescence of these products is forcing users to replace products with an advanced technology. Life cycles of these products are few years. Discarded electronics products are, therefore, accumulating alarmingly in our society. Electronics waste (e-waste) is a crisis not only due to its volume but also for presence of its toxic ingredients, like heavy metals (e.g. lead, mercury, cadmium, hexavalent chromium) and flame retardants such as poly brominated biphenyles and poly brominated diphenyles ether. These substances create potential occupational and environmental health hazardous."

Jan 1, 2011

By Paulo von Krüger

This paper deals with the cell design and operation of a tin electrorefining 1:5 pilot plant. The purpose of the work was the fitting of the basic parameters to be used in a full-scale tankhouse from a major Brazilian tin producer. The main specific difference was the use of permanent stainless steel cathodes instead of conventional tin starting sheets. The results of both product quality and operating parameters are discussed.

Jan 1, 2003

By K. Pagalthivarthi, P. V. Desai

"During solidification of alloys, many inter-related physical processes, such as melt convection, mass diffusion, heat transport, macrosegregation and melt-undercooling occur. Several research workers have studied one or more of these effects separately. To answer important questions on solidification behavior, an overall approach interrelating the processes is necessaryAs a first step toward accomplishing the overall modeling, the freezing of a binary liquid metal is examined. The various stages during freezing of the alloy are critically described to build a continuum model for the entire process. Diffusive mixture theory is used to write the conservation equations for the liquid and the mushy zones. The concept of local thermodynamic equilibrium in the presence of curvature effects is used to restrict the number of degrees of freedom within the mushy zone. Constitutive equations relating flux quantities and affinities, the governing differential equations and boundary conditions are discussed briefly for the freezing process.IntroductionA solidification study encompasses such facets as solifidication time, microstructure, macrosegregation of the solute, shrinkage effects and soundness of the casting. Influence of one or more of the coupled heat and mass transfer phenomena such as local solute redistribution, thermosolutal convection, melt undercooling at dendrite tips and heat dissipation to the ambient have all been previously examined [1-3J. Several studies have examined the individual facets of alloy solidification as isolated processses. In fact, the transport processes occur simultaneously and a comprehensive model should include their inter-relationships. In particular, some of the existing studies of the mushy zone [4-6J do not emphasize thermodynamic completeness. This work represents an attempt to develop a thermodynamically consistent model of the entire solidification process on physical grounds."

Jan 1, 1986

By Metehan Erdogan, Ishak Karakaya, Fuat Erden, Emre Ergül

"The FFC Cambridge process was suggested as a promising Si production technique for the expanding solar energy industry. Direct electrochemical reduction of bulk SiO2 plates and porous SiO2 pellets in molten CaCl2-NaCl salt mixture were investigated at 750°C by applying 2.8 V potential difference. The produced Si powder was brown and found to be contaminated by the Ni and stainless steel plates used as the cathode contacting materials. The reduction rates of the bulk SiO2 plates and porous SiO2 pellets were compared from variations of current and accumulative electrical charge that passed through the cell during the electrochemical reduction. The amorphous bulk SiO2 plates were reduced slightly faster than porous pellets of crystalline SiO2. The overall reduction potential of SiO2 pellets against the graphite anode at 750°C in molten CaCl2-NaCl salt mixture was determined as 2.3 V by cyclic voltammetry. This potential was supported by calculations.IntroductionMetallurgical grade Si cannot be directly used in electronic industry and some intermediate steps are required to produce industrial solar grade silicon (SOG-Si). A promising alternative solar grade silicon production technique is the FFC Cambridge Process [1]. Production of Si by electrochemical reduction of SiO2 at 850oC in molten CaCl2 electrolyte was first studied by Nohira et.al. [2]. In their study; Si formation was observed on bulk SiO2 cathodes after 1 hour of electrolysis. Complete electrochemical reduction of porous SiO2 pellets was first reported by Jin and his coworkers [3]. The mechanism of electrochemical reduction of SiO2 to Si in molten CaCl2 was explained in another study [4]. Reduction rates of bulk SiO2 and porous SiO2 pellets were also compared previously and it was found that reduction rates for bulk plates were higher [5]. Furthermore, it was reported that mixing Si into porous SiO2 pellet increased the reduction rate [5]. Mo [2, 4-7], Ni [3, 8, 9] or Si [6] were used as cathode contacting materials in various studies. Yasuda et. al. [6] produced Si with 99.80 % purity using Si plates as cathode contacting material to reduce metal contamination."

Jan 1, 2012

By Ibrahim Yusufoglu, Cem Kahruman, Sedat Ilhan, Ahmet Orkun Kalpakhi

"Scheelite is the main raw material in tungsten production. In hydrometallurgical processes, extraction of tungstate ions into solution is very important. During the leaching of scheelite in oxalic acid solutions, tungsten dissolves as a chelate complex. Scheelite includes impurities along with calcium tungstate. Determination of the dissolution of these impurities is important in the subsequent tungsten production stages. In this study, scheelite was dissolved in oxalic acid solutions and the dissolution of impurities was investigated. The quantities of dissolved impurities were determined by ICP - OES and characterization of the undissolved impurities in the leach residues was carried out by SEM - EDS analysisIntroductionScheelite and wolframite ores are used for the industrial production of tungsten. Both ores are dissolved in acidic or basic solutions, and ammonium paratungstate is obtained as an intermediate product. Prior to crystallisation of ammonium paratungstate, all the impurities must be removed. Among these, Fe, Si, P, Mn, Mg and Mo are classified as ""harmful"" elements and different methods are used for their removal [1]. During purification, solvent extraction, ion exchange, etc. methods are used.Potashnikov et al. [2] studied the dissolution of scheelite in acidic solutions and the effects of stirring speed, temperature and oxalic acid concentration on the dissolution kinetics.There are no works in the literature about the removal of impurities from scheelite ores in oxalic acid solutions. Therefore, the aim of this work was to investigate the dissolution mechanisms of impurities during the leaching of scheelite in oxalic acid solutions. The effects of temperature and oxalic acid concentration on the dissolution were also investigated. In addition, the characterization of the impurities which were not dissolved was studied."

Jan 1, 2012

By Minge Zhao, Yuandong Pei, Zhixing Zhao, Zejun Ma, Lili Ban

"Confocal scanning laser microscope (CSLM) has been applied to carry out the in-situ observation of melting and solidifying characteristics during iron ore sintering process, accompanied with TG-DSC test. It can be found that apparent Liquid phase forming temperature(LFT) and ending solidifying temperature(EST) is about 1190? and 1160?, respectively. Forming liquid phase during sintering process goes through four courses, these are shrinking, expanding, shrinking and expanding coexisting and expanding totally. For Yandi fine, the corresponding temperature of these four courses is about 1120-1160?, 1190-1196?, 1218-1220? and 1233-1270?, respectively. Although CAJ fine has more difficulty in forming initial liquid phase, but when liquid phase expands, it may have better fluidity and easier for liquid phase formation. Adding enough CaO, CAJ fine takes on high fluidity like Yandi fine, because liquid phase during sintering process is formed mainly by reaction between CaO and Fe2O3.IntroductionConfocal scanning laser microscope (CSLM for short) has been applied to carry out the in-situ observation of metallurgical phenomena, especially in steelmaking process. Recently, many researches on ironmaking process were conducted with CLSM. While for high temperature properties during sintering process, there are limited reports on in situ observation1-2). In this paper, melting and solidifying characteristics of iron ore were observed with CLSM under simulated sintering temperature, and high temperature properties of iron ore during sintering process was clarified based on the in situ observation results and TG-DSC research."

Jan 1, 2012

By Hubert Bril, Priscilla Pareuil, François Bordas, Emmanuel Joussein, Jean-Claude Bollinger

"According to the legislation, valorization type, origin and characteristics of waste material, various standard procedures are available to evaluate environmental impacts. A Mn-rich slag was sampled from a metallurgical plant. After its characterization (elementary analysis and mineralogy), five standard procedures were carried out (i.e. TCLP, EN 12457-1). Each fixed parameter of the standards was systematically studied in a large range: pH, Liquid/Solid ratio, contact time. For example, EN 12457-1 led to a low ME mobilization, increasing with the L/S ratio, the contact time and an acidic pH. As a conclusion, the representativeness of the considered parameters and their potential variations are predominant to assess of the real environmental impact during slag reuse. Introduction Recent studies have been carried out about environmental impacts of waste containing metallic elements (ME) because of their potential mobility [1-7]. Indeed, slags are either dumped or valorized in various activities such as building materials. In order to assess environmental risk, various standard procedures are used depending on country legislation, origin of waste and valorization way. Results of leaching tests are linked either to special legislation (e.g. Dumping: EC, Council Decision 2003/33/EC, Construction products: EC, Council Directive 89/106/EEC) or to legal levels used in drinking water (Directive 98/83/CE) when leachates could migrate to groundwater. If ME in leachates are lower than drinking water authorized levels, the waste will be considered as non-hazardous. On the contrary, if the leachable amounts exceed them, the question about the risk has to be posed. Beyond the abundance of leaching tests available, variety of operational conditions induced by these regulatory tests does not make the choice easier. According to operational conditions induced, ME release could vary from one test to another one. ME concentrations in leachates depend on pH, Liquid/Solid ratio, contact time and particle size [3]. To highlight the importance of these operational parameters, potential risk for valorization of a manganese-rich slag was assessed by comparing several standard leaching protocols [8-12] with a global study dealing with the influence of operational conditions. For each regulatory protocol, the most influential parameters (L/S ratio, pH, particle size and contact time) have been studied in a large range."

Jan 1, 2008

By Gustavo Díaz, Miguel A. García, Carlos Frías

"Under the auspices of the Commission of the European Union, a consortium composed of six European organi~ations has conducted a project to scale up the PLACID electrowinning cell to industrial size within the Placid process development. This paper is concerning the results and achievement of the industrial cell prototype after more than 1,000 hours operating time and about 10,000 Kg electrolytic lead production. In general, results have been very satisfactory, demonstrating the ability ofthe PLACID electrowinning cell to produce top quality electrolytic lead (> 99.99 %) with high current efficiency and low energy consumption.IntroductionThis paper is concerning the development of an industrial size PLACID electrowinning cell within the PLACID process development. This project began on January 1993 and was finished on April 1996.Lead metal production and manufacturing industries produce large amounts of dusts and also lead bearing slags. Spent lead-acid battery recycling also produces lead oxides from the battery pastes rather similar to those mentioned above. Those lead secondary materials are hazardous and difficult to handle by usual procedures.Existing processes to treat-lead oxides may inflict considerable damage on the environment, incur high operating costs and have limitations to produce top quality lead.The main aim of this project has been to develop a novel hydrometallurgical process able to deal with different lead bearing materials, mainly lead oxide secondaries: lead-acid battery pastes, lead fumes, furnace slags, oxide residues, etc., producing ""four nines"" pure lead in an efficient manner with a benign influence on the environment; it is called the PLACID process."

Jan 1, 1997

By Y. Y. Liu, H. M. Domanus, W. T. Sha

"Casting is fundamental to manufacturing of many types of equipment and products. Although casting is a very old technology that has been in existence for hundreds of years, it remains a highly empirical technology, and production of new castings requires an expensive and time-consuming trial-and-error approach.In recent years, mathematical modeling of casting has received increasing attention; however, a majority of the modeling work has been in the area of heat transfer and solidification. Very little work has been done in modeling fluid flow of the liquid melt. This paper presents a model of fluid flow coupled with heat transfer of a liquid melt for casting processes. The model to be described in this paper is an extension of the COMMIX code and is capable of handling castings with any shape, size, and material. A feature of this model is the ability to track the liquid/gas interface and liquid/solid interface. The flow of liquid melt through the sprue and runners and into the mold cavity is calculated as well as three-dimensional temperature and velocity distributions of the liquid melt throughout the casting process.IntroductionBower et al. (1), in their 1969 review of the evolution of some of the casting techniques, stated that:""The evolution of technology requires alternatives to be available so that choices can be made that lead to changes. The role of solidification science and other disciplines related to casting technology is to develop a better understanding of process and product, so that a wider range of alternatives is possible.Alternatives, whether from science or from invention, must lead to improvements in casting ""utility."" Utility, or economic advantage, must include consideration of total system costs, and final product value. The cost of materials, melt processing and finishing should be optimized with casting costs, since all are part of the production system. It is the favorable relationship between total processing costs and product value that makes a change in casting technology viable, but the best change is not possible unless technology has provided an understanding."""

Jan 1, 1986

By Baicheng Liu, Houfa Shen, Wensheng Li

"In order to understand the formation of macrosegregation in steel ingots, a mixture model has been developed which accounts for coupled mass, momentum, species, and energy transport to describe the sedimentation of free equiaxed grains during solidification. In this model, the mushy zone is divided into the slurry and porous regimes according to a solid packing fraction. Settling velocity of equiaxed grains in the slurry regime is given by an explicit expression. The solidification of a binary steel ingot (Fe-0.36wt.%C) with a two-dimensional geometry is numerically simulated. It is demonstrated that the predicted macrosegregation patterns agree to some extent with classical experimental results. Further refinement of this model is still necessary for realistically simulating steel ingot solidification.IntroductionModeling macrosegregation in steel ingots is still a challenging study, mainly due to the length scale of the products and the complexity of global multiphase transport phenomena coupled with microscopic solidification kinetics [l]. The thermal-solutal convection and the motion of equiaxed grains are the two main mechanisms responsible for macrosegregation. But there are few models that deal with the motion of equiaxed grains, which is confirmed as the main phenomenon that explains the negative macrosegregation along the centerline of large steel ingots [2]. A model which takes into account melt convection and grain sedimentation was first proposed by Beckermann and co-workers ([3], and references therein). More recently, similar multiphase solidification models with advanced nature have been presented by Wu and Ludwig [1,4] and Combeau and co-workers [5,6]. It is known that the application of these sophisticated models to steel ingot casting is at its beginning.In this paper, a solidification model based on continuum mixture approach, using much less sophisticated relations to obtain the settling velocity of free equiaxed grains, has been proposed in order to predict the macrosegregation in steel ingots. The model is applied to simulate the solidification of a binary steel ingot with a two-dimensional geometry, and preliminary modeling results are presented."

Jan 1, 2011

"Silver is traditionally recovered in base metal smelters (lead and copper), or as a by-product of other precious metals (gold and/or PGM's). This paper presents the results of non-conventional techniques to recover silver from complex materials. The PLATSOL® process has been developed to recover, in one step and without the use of cyanide, base metals (copper, cobalt, nickel) and precious metals (gold, PGM's) from sulphide concentrates too low in grade to enter the mainstream extraction processes. Silver is only partially recovered in solution with gold and the PGM's during the PLATSOL® process. However, the silver minerals are transformed into silver chloride, which can then be recovered from the PLATSOL® residue using conventional techniques. Some South American silver concentrates contain levels of impurity (mostly arsenic) so elevated that the penalties incurred significantly affect the process economics. The present results have shown that a low temperature calcination process transforms the concentrate into a product well suited for traditional recovery treatments. Metallurgical details will be provided, as well as the results of mineralogical studies that helped clarify the process mechanisms.IntroductionSilver occurrences in nature are very diversified, and, therefore, primary silver is produced as a by-product of many base metal and precious metal operations [1], as well as a co-product of most gold ores. However, difficulties can arise when high temperature processes are used for refractory gold ores or copper concentrates, or when the silver concentrate contains impurity elements such as arsenic that trigger high penalties."

Jan 1, 2012

By Mikio Kobayashi

Extraction of valuable metals from sulfide ores continues to be a very important, process and so the strict control of discharge of harmful metals in effluents from refineries becomes more important in the future. The recovery methods for heavy metals have been developed. Some metals such as Se and As are still difficult to be removed to very low concentration, although the techniques for recovery and removal for many kinds of heavy metals have already been developed. Especially, in case of Se the recovery system from water with low concentration has not be developed yet, although the WHO decided Se to be harmful for human beings and then the discharge control is under obligation now. In general Se exists as selenite ion and/or selenate ion in aqueous phase and selenite ion is able to be recovered by coprecipitation with ferric hydroxide or by reduction to solid selenium by general reductants. Selenate ion, however, has a strong resistance to conventional treatments. Therefore the new technique for the recovery of Se from water including selenate ion has to be developed. In this presentation the new approach for removal of selenate ion using the reaction in which ferrous ion is oxidized to ferric ion is presented. Selenate ion is reduced to selenite ion during the reaction and then to solid selenium, while ferrous ion is oxidized to ferric ion. The coexistence of activated carbon is very useful to increase the reaction rate. The use of iron powder is also effective and very useful for reducing gel-like precipitates mainly consisted of ferric hydroxide. The concentration of the residual selenate ion is probably under 0.1 ppm after recovering Se by the mentioned-above approach. In addition to the mechanisms of these reactions, the effects of pH, coexistent positive and negative ions, and reaction temperature are also presented. Furthermore the investigation of the behavior of selenosulfate is presented.

Jan 1, 1998

By Boris Arlyuk

The system of short term forecast of metal prices at LME is based on correlation between prices within the quarter forward and at the first place by economic parameters at the West, determining the consumption of metals. Such economic parameters are presented by data of indexes of Western World industrial production (WW IP), official data of IP and Dow Jones indexes at USA. For price forecast within the quarter forward (one day ahead, 3 day -65 days MA forward prices) are significant the changes of actual prices (official and close) at the past and the parameters of daily trade at LME at the past (futures turnover, open interest, LME stocks). It is developed subsystem of price forecast within the quarter forward based on analytical approach determining the relations between the participants of the market. It gives the opportunity to reduce the number of empirical coefficients at the model and receive good accuracy of forecast the MA prices and its direction at the future. Very important part of short term forecast is subsystem determining analytically the probability that the price forecasted for the next trading day will be the maximum or minimum daily price within the quarter forward. The thresholds probabilities are defined by identification the model at the past by maximal commercial efficiency. Such system was tested at the past at period since 2000 till 2005 and gives very high commercial results at operations on 1M forwards and hedging the sales of nonferrous metals traded at LME (primary aluminium, light alloys, nickel, copper, zinc, lead and tin).

Jan 1, 2006

By V. Bojarevics, K. Pericleous

"A number of different methods have been developed for noncontact electromagnetic treatment of liquid metal and to investigate the melting/solidification processes. Applying AC magnetic field in terrestrial conditions, along with the buoyancy and thermo-capillary forces, results in turbulent flow. The use of a homogenous DC magnetic field allows damping both of the turbulence and the large scale flow at different rates leading to surprising results at some stages. The dynamic interaction of the turbulent flow with the oscillating interface needs to be accounted if it is required to levitate liquid metal of up to few kilograms without the contact to container walls. At the high values of magnetic field some oscillation modes are damped quickly, while others are modified with a considerable shift of the oscillating droplet frequencies and the damping constants from the non-magnetic case. Numerical models are used to investigate behavior of liquid metal suspended in high DC magnetic fields providing microgravity-like conditions with laminar viscosity and heat transfer to the surroundings.IntroductionSince the early Electro Magnetic (EM) levitation experiments [1] in AC magnetic field it became apparent that the levitated liquid metal is prone to oscillation and instability. The EM and electrostatic levitation experiments with liquid metal droplets show difficulties related to confinement stability and a need for complex correction functions to establish a correlation between the measurements and the droplet material properties [2,3]. Intense internal fluid flow is visually observed, apparently being in the turbulent regime for earthbound conditions."

Jan 1, 2012

By Chang Wei, Fan Zhang, Zhigan Deng, Minting Li, Cunxiong Li, Gang Fan, Xingbin Li

Marmatite is an important resource of zinc, which exist in forms of high iron and high indium. In order to recycle the valuable metal from these ores, the testwork of simultaneous leaching on neutral residue mixed with zinc concentrate of high iron and high indium has been conducted. The primary objectives are to leach the zinc and indium remaining in the neutral leach residue as ferrite using acid, and to reduce the ferric iron in solution to the ferrous by zinc concentrate, thereby extracting the zinc and indium in the zinc concentrate. The results indicated that in the following conditions, mass ratio of neutral residue to zinc concentrate of 1:0.25, particle size of 74-58 μm, initial sulfuric acid concentration of 150 g/L, liquid to solid ratio of 8 L/kg, temperature of 90°C, reaction time of 4h, the leaching efficiency of zinc and indium were over 95%, nearly 90% Fe was Ferrous in the leaching solution. This process effectively extracted zinc and indium and converted Fe3+ into Fe2+ in solution, and simplified the traditional process of reduction after leaching.

Jan 1, 2016

By Fashina Olugbenga Emmanuel, Ghazali Akeem, Adegbola Adekunle Amos, Omotoyinbo Joseph Ajibade, Olaniran Oladayo

"Modern engineering materials are required to be light weight and corrosion resistant, coupled with high strength and hardness. In this work, Al formed the parent metal and alloyed with 2.03% of Copper by sand casting process. The cast product 2024 was warm worked at various temperatures ranging from 300 to 5600c at 5%, 10%, 15% and 20% deformation respectively and aged accordingly. The results showed that the mechanical properties vis-à-vis hardness, tensile improved with increasing % deformation at a higher temperature. This was due to the progressive close-up of the voids emanated from casting by increasing deformation which is evident from the micrographs. MATLAB was also adopted to generate a model capable of determining the trend of flow of stress at operating temperatures. This was of immense value due to an increasing impact at higher percentage deformation with temperatures. Hence, Al -alloys will find applications in land vehicles, ships, trains, and aircraft, at elevated temperature.INTRODUCTIONThe problem of safe vehicle design with maximum impact energy absorption is a significant subject in structural crash worthiness design [1]. All engineering designs are expected to ensure the safety of users' life. This informed several studies meant to probe the causes of component failures in equipment, vehicles, and aerospace design and decide on appropriate solutions through materials selection techniques. A common example is in the design of crankcases and heads, piston, and cylinder blocks. As with engine blocks, cylinder heads can be made of Cast Iron or Aluminium Alloy. A head made of Aluminium alloy is lighter in weight than if it were made of Cast iron [2]."

Jan 1, 2013

By Gustavo E. Lagos

Mining is one of the oldest and most important productive activities in Chile. In the latter half of the 80's &d during the 1990's Chilean mining has experienced explosive growth fundamentally due to legislative changes which have encouraged an influx of foreign capital. Fine copper production has grown from 1,4 million tons in 1987 to 3,4 million tons in 1997. Gold production has increased from 17.03 tons in 1987 to 49.46 tons in 1997. In both cases private investment has driven this growth. The direct impact of mining on the Chilean economy has been considered one of the fundamental pillars of the growth of the country in the last years. The indirect impact that has generated on the other sectors of the Chilean economy and in particular the regional economies, has not been analyzed. This paper outlines a methodology for estimating the impact of mining investment and mining operations in different sectors of the Chilean economy at both regional and national levels. It applies this methodology to the case of Minera Escondida, the largest copper mine in the world, analyzing its economic impacts on the regional and national levels.

Jan 1, 1999

By Zenon R. Llanos

"The disposal of spent hydroprocessing (HDP) catalysts in the petroleum refining industry has been a concern in the past due to their classification as listed hazardous wastes. However, because these catalysts have higher metal concentrations than regular ores, and the recent surge in prices for molybdenum, vanadium, nickel and cobalt what used to be considered as a liability for generators is now viewed as a valuable renewable source of strategic metals. At the same time the generation of spent catalysts has steadily risen due to new environmental regulations for low sulfur fuels and an increased appetite of gasoline consumers. This paper will examine spent catalyst market and the role played by Gulf Chemical & Metallurgical Corporation in the reclamation of metals over the last sixty years. Introduction Hydroprocessing (HDP) catalysts are used in petroleum refineries for two main applications: desulfurization and cracking. The catalyst support is alumina or mixtures of alumina and silica. Active metals include molybdenum, nickel, cobalt and tungsten. The selection of catalysts depends on the application and sometimes the cost. The life cycle of HDP catalysts is represented in Figure 1. The catalyst cycle in a reactor varies from continuous to one-two years. Catalysts used in various refining processes are deactivated by coke, sulfur, vanadium and other impurities in the refinery feedstocks and become spent. Refineries can optionally send the spent catalysts for regeneration, metals reclamation or landfilling. Catalysts used for refining heavy crudes often can not be regenerated. Catalysts used with light oils can be reused twice or three times after regeneration. When the option for regeneration is not viable, spent catalysts are send metal reclamation facilities or landfills."

Jan 1, 2008

By Esa J. Peuraniemi

Copper smelting to form blister in one single step has been possible for a long time even from low grade concentrates. In spite of obvious benefits, it has been economically viable only with few special raw materials having high enough Cu/Fe and Cu/S ratio. Outokumpu Blister Flash Smelting is currently applied at three operations, and three others will be commissioned in the near future. With typical chalcopyrite concentrates two main obstacles have prevented wider adaptation of direct blister processing: slag formation and heat generation. Oxygen potential in the reaction shaft must be high in order to produce blister with targeted sulfur content below 1%. When large amount of iron is oxidized, as well as sulfur, copper is inevitably also oxidized into slag. High copper amount in substantial tonnages of slag lead on to costly down stream recovery operations to obtain discardable slag. Almost complete oxidation of sulfur and iron releases a high amount of heat which traditionally has been solved by lowering oxygen enrichment of the blast leading on to oversized off-gas line and acid plant. One challenge in direct blister smelting relates to the attack of aggressive high-copper containing slag against furnace refractory lining. In continuously operated Outokumpu Direct Blister Flash Smelting this is taken care of by preventing vigorous melt movement in the settler. Stable bath conditions and stationary slag against refractory lining enable the formation of a protective autogenous layer between aggressive slag and vulnerable refractory. These direct blister smelting challenges are addressed from equipment and process development point of view. New solutions to overcome the obstacles are presented and discussed.

Jan 1, 2006

By Esperidiana A. B. Moura, Mariana N. Sartori, Vijaya K. Rangari, Angel Visentim Ortiz, Francisco R. V. Diaz, Rene R. Oliveira

"This work presents the preparation and characterization of a nanocomposite based on Poly(butylene terephthalate) PBT and Brazilian smectitic clay (bentonite chocolate clay). Before being incorporated as clay nanoparticles in PBT resin, the clay was organically modified by the addition of a quaternary salt and sodium carbonate. PBT/Clay nanocomposite (96.3:3.70 wt %) was obtained by using a twin-screw extruder machine. After extrusion process, the nanocomposite was characterized by tensile, flexural and impact tests, SEM, Vicat, HDT, DSC, TGA and XRD tests. The results showed that the properties of the nanocomposite obtained were superior to those of neat PBT. Concerning the temperature of thermal distortion (HDT) an expressive gain of around 45 % was presented to PBT/Clay nanocomposite compared to PBT evidencing the interaction of nanofiller with the polymeric matrix.IntroductionPolymer-clay nanocomposites, also called as polymer layered silicates nanocomposites have attracted much attention from both industry and academia over the past decade because they frequently exhibit unexpected properties. In contrast to the traditional fillers, nanofillers, in particular, nanoclay, is found to be effective. The addition of a small amount (< 5 wt.%) can show significant improvement in mechanical, thermal and barrier properties, flammability resistance, and electrical/electronic properties of the final polymer nanocomposite without requiring special processing techniques. Also, as with other nano-size particles, the overall crystallization rate and the glass transition temperature are also affected. It is generally believed that the improvement of properties of nanoclay composites is directly related to the complete exfoliation of silicate layers in the polymer matrix. However, a processing technique that produces complete exfoliation is still a technical challenge [1,2]."

Jan 1, 2012