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By Daniel Kim, Justin McAllister, Shijie Wang

"At the Kennecott Utah Copper Refinery, impurities in the electrolyte are being precipitated in the circulation system and form a hard scale in the piping. This scale must be removed periodically for proper electrolyte flow. Distinct layers of differing composition form as the operating conditions of the tank house change. Scale samples from the inlet and outlet pipes were analyzed to discover the nature of the precipitates. Each sample was sectioned and examined under optical microscopy and SEM. The composition of the scale was analyzed using ICP, XRD, and SEM/EDX mapping. The rate of deposition was determined by measuring the amount deposited on new pipes after elapsed time intervals. In order to determine how to minimize the formation of the scale, the mechanism was studied and the results are presented in this paper.IntroductionIn copper electrorefining, impure copper anodes are refined into pure copper cathodes. The impurities from the anodes are either insoluble and report to the slimes or soluble and dissolve concentrating in the electrolyte. These impurities are controlled by bleeding electrolyte from the system. Over time, the impurities combine to precipitate a hard scale on the surfaces contacted by the electrolyte. The scale causes problems with tank house circulation systems. In order for the refinery to operate properly, the scale must be removed periodically from the walls of the pipes. The first step to control the buildup of scale on the pipes is to understand the composition and the phases that are present in the scale."

Jan 1, 2012

By R. K. Hill

The Hidalgo Smelter successfully reduced operating costs by 25% compared to the previous two years through a focused holistic approach to development of its entire workforce. The first phase involved basic team training skills for natural work teams. The second phase provided leadership training via breakthrough education to 40 of the smelter leader-both hourly and salaried. The third phase stretched out the teams training to include rewards for performance that resulted in hourly teams converting to salaried status-part of a company wide initiative. The fourth phase saw 1998 become the "Year of Safe Cost Reduction" where 7 breakthrough projects focused on different areas of expenditure. Implementation of lean manufacturing as a tool for teams to truly get their arms around what they controlled, introduced accountability and responsibility for operating results at the team level. This will allow the release of experienced supervisors from this role, to a pool of technical expertise, where our future breakthroughs will be designed and implemented.

Jan 1, 1999

By Fatbardha Osmani, Skender Osmani

"A system analysis of the resource and environment management (water, energy etc) starts from its definition. Unfortunately, there is not a unique semantics of the mentioned concept. On these circumstances, in this paper the following issues are presented: 1.A short view on the existing concepts of management. 2.A new definition on the concept of management. It is considered as a complex and rational activity on human and natural resources ,environment etc, which starts from a analysis of infrastructure ,technology , etc, mission , alternatives , project etc. and ends to an optimal output. Basing on this definition, the management has two principal components: strategy and policy. The strategy is referred as a blue print program (the same definition as in Game Theory), which contains all the contingency alternatives. , while the policy is referred as a strategy applied into practice. The strategy is the first , while the policy is the second one. The best alternative of a policy is the project, Each strategy has one and only one project. The mentioned definition erases the differences between concept of policy and politics. Each strategy has its alternatives ,the next has its sub strategy and so on, i.e. whatever are going to be the strategy, there are a hierarchy composed by sub strategies up to the simplest strategies applied by a single individual (human beings or robots). The strategy objectives are necessary and sufficient conditions for its realization i.e . the strategy is an optimal activity, in which all resources are integrated and processed . Several strategies could be joined into one( for example the surface water strategies of the Balkan countries) . In this view, the strategy could be globalized into optimal way basing on different criteria’s as social, economic, environmental, their risks and effectiveness etc. etc An example from the water management illustrates the mentioned concepts."

Jan 1, 2008

By Moo Eob Choi

A new process for converting sulfur dioxide to elemental sulfur by a cyclic process involving calcium sulfide and calcium sulfate without generating secondary pollutants was developed at the University of Utah. In this process, sulfur dioxide is reacted with calcium sulfide to produce elemental sulfur and calcium sulfate. The latter is reduced by hydrogen to regenerate calcium sulfide. In the present work, the effects of different pelletization conditions for the initial reactant calcium sulfate on the strength and reactivity of the pellets were determined. These conditions include the type, amount, and impregnation method of catalyst, binder amount, and sintering. Experiments were also performed to determine the effects of temperature in the range of 973-1173 K, pellet size, cycle repetition, and water vapor or carbon dioxide content in sulfur dioxide stream on the reaction rates of the cyclic process. Nickel-catalyzed fired pellets produced by the use of molasses or cement as a binder showed good reactivity as well as high compressive strength during the cyclic tests. The binder amount did not significantly affect the reaction rate.

Jan 1, 2006

By E. Salinas-Rodriguez, J. Hernández-Ávila, E. O. Ávila-Dávila, A. Romero-Serrano, M. Perez-Labra, G. Juárez-López

"Single phase rubidium jarosite was synthesized by precipitation from aqueous solution. X-ray diffraction and SEM-EDS analyses showed that the synthetic rubidium jarosite formed in subspherical particles with an average particle size of about 35 µm. The chemical analysis showed an approximate composition of Rbo9432Fe3(SO4)2 1245(OH)6. The decomposition behaviour of the jarosite in terms of solution pH was thermodynamically modeled using FACTSage by constructing the potential-pH diagram at 298.15 K. The E-pH diagram showed that the decomposition of jarosite leads to goethite (FeOOH) together with Rb+ and SO42- ions. The experimental decomposition of the Rb-jarosite was carried out in alkaline solutions with five different Ca(OH)2 concentrations. The decomposition process showed an ""induction period"" followed y a progressive conversion period where the Rb+ and SO42- ions formed in the aqueous solution. In contrast, calcium was incorporated in the solid residue and iron was transformed into amorphous ferrihydrite. The kinetic analysis showed that this process can be represented by the unreacted-core chemically controlled model. The reaction order with respect to Ca(OH)2 is 0.4342 and the calculated activation energy is 98.70 kJ mol-1. IntroductionJarosite type compounds are hydrous sulfate minerals containing alkalis and ferric ions, MFe3(SO4)2(OH)6, where M can be H3O+· Na+, K+, Rb+, Ag+, NH4 +, Tl+, ½ Pb2+ or ½ Hg2+. Jarosite-type compounds were formed by the natural ""in situ"" oxidation of pyritic ores leading to the replacement of the original iron sulfides and iron oxides (Dutrizac and Kaiman) [1]. The great interest in jarosites is due to its ability to eliminate or diminish the iron concentration of the acid leach solutions produced in the hydrometallurgical zinc process, with relatively low losses of divalent metals such as Zn2+, Cd2+, Cu2+ or Co . However, the losses of the metal values demand a careful study of the conditions under which the jarosite compounds are formed together with their chemical properties."

Jan 1, 2012

By Tomas Astorga

APEC, the Asia Pacific Economic Cooperation is the forum of 18 economies, having a combined GDP of approximately 56% of the total world income, and over 45% of global trade. Its mining sector produces a large portion of the main minerals and metals in the world. In 1997, APEC economies produced 67% of world copper output, 55% of gold, and over 45% of other base metals. Mining in APEC captures more than 60% of the total mining investment in the world. Against this background, the Expert Group on Minerals and Energy Exploration and Development, in short GEMEED, was created in 1996, under the auspices of the APEC Energy Working Group. The sustainable development of mining activities is a main concern in APEC and GEMEED. Several programs related to the subject are actively being pursued by the Expert Group. Among them, it should be noticed the creation of an Environmental Cooperation Sub Group coordinated by Japan, whose main aim is to encourage proposals related to the environmental soundness of mining projects in the region. Also, it should be noted the existence of a Database Steering Committee whose focus is the development of an information network related to mining opportunities in the region GEMEED is a gathering of experts from all the APEC economies. As such, it represents a privileged forum to discuss policy issues related to mining. On this regard, the paper focuses on concrete actions taken by GEMEED to enhance the sustainability of the copper activity in the region.

Jan 1, 1999

By Laurentiu Nastac

"An advanced casting simulation-based optimization approach was applied in this study to assist in the improvement of the mold design of aerospace components made of A3 56 alloy. By using this approach, mold filling and solidification related defects (including macro-shrinkage and shrinkage porosity) were significantly minimized and hence it helped in cost reduction, performance enhancement and quality assurance of complex A3 56 cast parts.An experimental validation and detailed calibration procedures of the models for prediction of macro-shrinkage and shrinkage porosities were performed using A3 5 6 plates cast in fiiran-silica sand molds using the Prometal's Rapid Casting Technology (RCT) - mold printing technology. Correlations between Niyama values and the pore percentage were also developed. Thus, the severity level of shrinkage porosity can be determined via the Niyama criterion. Predictions were then compared with the macro-shrinkage and porosity measurements in plates of various plate thicknesses and in other commercial A3 56 casting components.IntroductionThis paper describes the process modeling approach used in the development of the mold design technology used to produce assist in the improvement of the mold design of aerospace components made of A356 alloy. Nova Flow&Solid™ software [3] was applied in this study. This casting simulation software was previously validated for several alloys including Ti, steel and superalloys [1-4]. The objective of this paper is to calibrate and validate the simulation software for A356 alloy sand mold castings. For this purpose, an experimental validation and detailed calibration procedures of the models for prediction of macro-shrinkage and microshrinkage (e.g., shrinkage porosities) were performed using A356 plates cast in fiiran-silica sand molds using the Prometal Rapid Casting Technology (RCT) mold printing technology. The details of the RCT technology are shown in Fig. 1 [5]. Prometal's RCT technology is used for rapid production of sand molds and cores directly from CAD files. The RCT technology relies upon ink jet printer technology to selectively bind the grains of sand to create three-dimensional sand molds and cores. Mold filling and solidification modeling as well as stress analysis are typically performed to properly design the casting and the rig system of each prototype component."

Jan 1, 2012

By Lucas L. Costa, Luiz F. Lopes, Ludy C. Motta, Felipe P. D. Lopes, Sergio N. Monteiro, Lara S. Vasconcellos

"Environmentally correct materials like the lignocellulosic natural fibers, which are renewable and biodegradable, are being extensively investigated as possible substitutes for synthetic fiber in polymeric composites. Several natural fibers have never been thoroughly investigated as possible composite reinforcement. The fiber obtained from the leaves of the buriti (Mauritia flexuosa) palm tree is one example. Therefore, the objective of this work was to study the properties of buriti waste fibers, in amounts of up to 30%, reinforcing polyester composites.IntroductionIn the past century, the technological development gave priority to new synthetic materials with energy intensive methods of production. Today, there is a concern that conventional energy source such as petroleum, natural gas and coal are the main responsible for global warming. Therefore, the use of natural materials is gaining attention not only for the saving in process energy but also the renewable and biodegradable characteristics that make them environmentally correct. The lignocellulosic natural fibers extracted from cultivated vegetables like jute, sisal, hemp, coconut, flax, ramie and many others are typical examples. This type of fiber is being extensively investigated as a possible substitute for synthetic ones, especially the glass fiber, as composite reinforcement [1].A relevant example of lignocellulosic fiber substitution is nowadays occurring in vehicles. The automobile industry is applying composites reinforced with natural fibers to replace parts such as panels and seat cushions made of fiberglass or polymeric foams [4], as illustrated in Fig. 1. The practical reasons for this preference are that natural fiber composites present less damage to tools and molding equipments as well as relatively better finishing and less abrasive surface than corresponding parts made, for instance, of glass fibers. On top of these advantages, low cost is probably the main motivation for the industrial interest for natural fiber composites, especially in the case of residual fibers [5] or post-used fabrics such as jute sackcloth [6]. Natural fibers, however, are hydrophilic and will not form strong bonding with a hydrophobic polymer, normally used as composite matrix [1-3]. Another disadvantage is the heterogeneous characteristics of a natural fiber, which is typical of biomaterials. This results in a relatively great dispersion of dimensions and properties values such as the mechanical strength [1-3]."

Jan 1, 2008

By Rauno Peippo

Horizontal Waste Heat Boiler (WHB), today's proven and dominating technology for copper smelter gas cooling, has been utilized by the industry for over half a century. During this time development has taken place in geometry, flow characteristics, cleaning technology and design details. This development has been driven by improved understanding of the specific process requirements, gained both by wide experience and by utilizing new emerging design tools, like computer flow modeling. It had to wait till mid 90's to unite effective and proven Spring Hammer cleaning technology and the process benefits gained by gas guiding vanes or baffle wall in the copper smelter WHB design. The new design has demonstrated improvement in gas cooling efficiency and the process conditions down stream in form of less dust sticking problems in the boiler and precipitators. Reduced weak acid production has also been reported as a result of the design. The theoretical aspects, computer flow modeling results and actual benefits measured in old smelting line modernization are discussed. Experience £tom modernization projects such as Phelps Dodge, Atlantic Copper, Mexicana de Cobre, and Nippon Mining, Saganoseki, are discussed. In mechanical design there has been development resulting improved gas tightness with less corrosion and better control of dust sulfation. An essential improvement is the integration of the boiler hopper and dust removing conveyor. Having no steel plate casings in the hopper and conveyor section but using of boiler tube membrane instead eliminates thermal expansion differences. The dust conveyor will be effectively cooled against hot dust lumps falling down while the acid dew point corrosion is prevented in the cooler sections of the hopper. Conceptual features are presented of a new generation Copper Flash Smelter WHB presently under construction at Boliden Mineral, Skelleftehamn, Sweden, where the latest development and innovations are adopted.

Jan 1, 1999

By Shadia J. Ikhmayies

"Nanocrystalline fluorine-doped tin oxide, SnO2:F, thin films were prepared by the spray pyrolysis (SP) technique on glass substrates. The films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray dispersive spectroscopy EDAX and transmittance measurements. X-ray diffraction patterns revealed the nanocrystalline nature of the films where the grain size was estimated based on the Sherrer formula. SEM micrographs showed that the films are uniform and totally covered with the material and they confirmed the nanocrystalline nature of the films. The absorbance was deduced from the transmittance measurements, and its first derivative was used to estimate the optical bandgap energy. Bandgaps larger than the bandgap of the bulk SnO2iF were obtained, indicating the presence of quantum dots. The hyperbolic band model was used to estimate the radii of the nanocrystallites. A comparison between the results of the different methods was performed.IntroductionTin oxide, SnO2, thin films are n-type semiconducting, transparent materials, which have numerous important applications in optical-electronic device technology. The optical transparency of SnO2, together with its chemical and mechanical stability, makes SnO2 films suitable for many other applications, such as transparent conductive coatings, gas sensors and heteroj unction solar cells [1]. In particular, SnO2 thin films have drawn much interest because of their potential application and integration with microsensor devices. Considerable attention has recently been focused on the development of solid state gas sensors based on thin films with a crystallite size smaller than the Debye length of the material, which show increased gas sensitivity and short response times [2]. In many of these applications, a doped SnO2 film is used as an active layer. Among the various dopants, fluorine is often preferred, because fluorine doping results in films with high transparency and good conductivity [1]."

Jan 1, 2012

By Daniel Kim, Michael Free, Justin McAllister, Urian Marshall, Shijie Wang

"Cathode impurity levels of electrorefined copper were evaluated based on 1/10* scale laboratory electrorefining tests. Cathodes were evaluated near the top, mid-section, and bottom sections of cathodes on both the set and mold sides and strip and scrap cycles. Slime weights were measured, and slime and electrolyte samples were also evaluated for impurities. Results from these tests have been compiled and compared to evaluate the effects of changes in operating conditions and electrode location on cathode impurities.IntroductionMany types of impurities are commonly found in commercial copper electrorefining anodes. The smelter operations that produce the anodes process concentrates that contain a wide variety of impurities that vary based on the mineralogy of the ore. Most anode impurities are removed during electrorefining. However, a portion of the anode impurities is incorporated into the copper cathode product. The mechanisms by which impurities are transported from the anode to the cathode are not well understood. Some impurities can be transported as anode slime particles to the cathode where they are incorporated into the cathode. Other impurities can be transported as dissolved species that are electrochemically reduced with the copper to become part of the cathode. Although research has been performed on anode slimes and impurities [1-4], there is a need for additional information regarding the relationships associated with electrorefining cycles, electrode faces, local electrode positions, anode impurities and specific cathode impurities. The objective of this study was to evaluate lead, arsenic, and antimony cathode impurity trends associated with electrorefining cycles, electrode faces, local electrode positions, and anode impurities. A variety of techniques including electrolyte filtering, anode heat treatment, high electrolyte arsenic concentration, high arsenic and/or lead in anodes, flocculation of slime particles, and appropriate current density control were used to vary cathode impurity levels. Each test was performed only once for a strip cycle and once for a scrap cycle. Consequently, the results for the individual conditions are preliminary and are not the focus of this study. However, the collective set of data with varying impurity modifying techniques provides a broad range of impurity levels, and the associated trends with respect to lead, arsenic, and antimony are discussed in this paper. Approximately 180 analyses of copper cathode were used to track the antimony, arsenic, and lead impurities. Eighteen anode slime samples were also analyzed for antimony, arsenic, and lead."

Jan 1, 2012

By C. P. Broadbent

Due to growing .public awareness of environmental issues and greater sensitivity towards waste management, many countries around the world are implementing more stringent legislation governing the storage and disposal of hazardous wastes containing heavy metals such as As, Sb, Pb, Cd or Hg. These wastes can no longer be dumped without providing clear guarantees that the material concerned is environmentally safe and will not leach toxic elements to the surroundings. In the Netherlands the current dumping charge for chemical waste (i.e. worst category) is $280/t, and for industrial waste this cost reduces to $75/t. If the material can be reused there may be a small positive credit for selling it, for example discard slag as an aggregate to the construction industry. A number of (pyre)-metallurgical operations, mostly associated with the extraction of metals from sulphidic ores, produce arsenic residues in the form of As2O3 containing flue dusts and speises. If the flue dust is of high purity it can be sold, though many traditional uses are being substituted by other materials. In many cases upgrading the quality of the arsenical dusts is not possible for either technical or economic reasons. Traditional practice is to dissolve these dusts in acid prior to precipitation as ferric arsenate, which is at present classified by many countries as industrial waste and can be dumped. Recent work, however, has cast doubt on the stability of arsenates for disposal and alternative disposal routes have been investigated. Tests have shown that up to 10% (dm) As can be incorporated into "glassy" silicate slags with very low levels of arsenic leaching in the cooled product. Calcium arsenate was added to a range of synthetic and industrial slags from the system SiO2-FexOy-CaO-A12O3-AsmOn, under mildly oxidising conditions and quenched subsequently in water. It would appear that this represents an environmentally acceptable method for the disposal of many arsenical residues and there is some optimism that this method will be equally applicable to the disposal of other toxic metal residues.

Jan 1, 1994

By Fernando Guevara

Many smelting and slag-cleaning furnaces operate with cooling systems designed to freeze a slag layer over the refractory to protect it. The fluid flow and heat transfer conditions associated with the freeze layer and mushy zones are poorly understood. These phenomena were simulated with a small-scale room temperature, 2-dimensional model, using an aqueous solution of calcium chloride to simulate the slag. Reasonable similarity with conditions encountered with copper and nickel smelting systems was achieved (Pr 50 and Ra 108, in the laminar-turbulent transition). Measurements of the freeze layer development and velocities were made with the Particle Image Velocimetry (PIV) technique. Direct Numerical Simulations (DNS) were also made of the unsteady fluid flow and heat transfer problem. It was found that the solidification process is well described using an improved model for high molecular viscosity in the mushy zone. Solid front growth, isothermal profiles, velocity profiles and heat transfer through the walls showed good agreement between the PIV and DNS results. Experimental and numerical velocity profiles close to the freeze layer show a parabolic behaviour in the vertical velocity profile which is completely different from the calculation of heat transfer using a sharp interface model. The reason for this is attributed to the effects of the mushy zone with a high viscosity and high shear stresses acting on that area.

Jan 1, 2006

By Petr Stehlík

"This paper is aimed at showing and demonstrating progress in technologies and improvements in units for the thermal processing of various types of waste. The following areas are covered: units for the thermal treatment of hazardous industrial waste and common MSW, technologies for the thermal treatment of industrial and sewage sludge, utilizing waste in cement production (material and energy recovery), up-to-date off-gas cleaning systems, original and unique units for the thermal processing of polluted gases, low-NOx burners. The paper represents a review based on industrial applications, papers published in reputable international journals and a monograph under preparation.IntroductionThe present contribution is an overview of the activities and achievements of the Institute of process and environmental engineering (UPEI) of the Brno University of Technology (VUT). The Institute belongs to European leading teams in the field of the thermal processing of various types of waste. The research in the institute currently revolves mainly around a strategic project “Waste and Biomass Utilization focused on Environment Protection and Energy Generation” that is supported by the national government. Due to the limited space this paper is conceived as a review of papers published especially in reputable international journals.Main (strategic) target of the research is development of new, efficient processes (eventually modernized processes with novel original elements) for effective and highly efficient treatment of waste and biomass, including their maximum utilization as renewable energy sources while minimizing harmful emissions. To this purpose, highly advanced know-how for the design and construction of the related technology lines is being developed, supported by mathematical modeling (see e.g. [1]), experimental validation and optimization.Municipal and Industrial Solid Waste – Concept of Waste-to-Energy CentersThermal processing of various types of wastes is not only waste disposal and/or treatment at present. It has to be regarded as waste to energy process wherever and whenever possible and feasible. This observation was at the origin of the concept of new regional Waste-to-Energy Centers (WTEC), outlined in the following paragraphs. The proposal of the centers is based on a combination of experience, know-how and sophisticated approach. The main fact influencing the concept of WTEC is the necessity to treat different types of wastes. Typical types of wastes as well as main products of the processes in a WTEC are shown in Figure 1."

Jan 1, 2008

By Larry M. Southwick

The smelting of copper and other non-ferrous metals have made considerable advances over the last 125 years. Many of the ideas and processes currently in use were attempted early in the history of smelting and were unsuccessful. Often the cause was incomplete understanding of the metallurgy involved, inadequate refractories, poor materials of equipment fabrication or trying too many new ideas at once. With time, these problems get solved and the technologies become commercialized .These were processes whose time had not come when originally proposed, but did eventually. On the other hand, there have been some concepts whose time will never come. They were impossible then and they are impossible now. The people that dream these up were either crackpots (they didn't know what they were doing, but thought they did), or charlatans (they knew they didn't know what they were doing, but didn't care). Both rely on bad science to propose metallurgical absurdities. These too have their place in the development of technology, though mostly negative, and several examples will be discussed in this paper. Three from around the turn of the century will be covered, as well as one from this decade. The last demonstrates that the art of creating absurdities has not withered, even after ninety years of scientific sophistication, and some can even be patented. The first three reached field trials due to the gullibility of company management. The last arose from a fortuitous mis-operation of a plant which solved a problem, but the explanation and patent which arose are metallurgically impossible.

Jan 1, 1999

By Pekka Taskinen, Hannu Johto

"Copper sulfide concentrates often contain impurities such as lead and iron. The phase stabilities of the sulfide impurity systems in metallurgical process conditions are in many cases unsatisfactorily known. Thermodynamic information of a system gives better understanding of its behavior of metal making processes, but also has effects on the economic and environmental factors of the production process. In this study, isothermal equilibrium and quenching experiments of the stable phases of the system Cu2S-FeS-PbS at 700 and 900 °C were carried out and based on the experimental results, Gibbs triangle of equilibrium phases of the system was outlined.IntroductionThe knowledge of stabilities of phases and the thermodynamic properties of many sulfide systems in the temperature range of 500-1200 °C are quite limited. Especially, the knowledge of liquidus surfaces of multicomponent sulfide systems is essential for making many metallurgical processes more environmental friendly and allowing the utilization of complex concentrates. In this work, the aim was to investigate the phase stabilities of the quasiternary system CU2SFeS- PbS using evacuated silica ampoules. Of greatest interest were the properties of the liquidus surface in the system, in order to be able to predict better the formation of a liquid phase in metallurgical processes."

Jan 1, 2012

By Dachun Liu, Yifu Li, Baoqiang Xu, Yongnian Dai, Bin Yang

"The removal of impurity arsenic from crude tin is one of the major problems in the process of tin refining. Through a thermodynamic analysis on vacuum refining process of crude tin, the vapor pressure of impurity arsenic under different temperatures can be obtained, which demonstrates that it is possible to separate tin and arsenic by the vacuum refining process. This paper attempts to verify the behaviors of impurity arsenic. The experiment result shows that through vacuum distillation, crude tin with 0.16% arsenic can be refined from crude tin with 0.96% arsenic, and about 50% impurity arsenic can be collected in the form of metallic arsenic.PrefaceThe crude tin obtained by the reduction process is insufficiently pure for most applications, even smelting from tin concentrate. Arsenic is a common impurity in crude tin and also one of the predominant elements to affect tin performance. Arsenic is a poisonous metal that has long been linked to an increased risk of cancers, diabetes, thickening of the skin, diseases of the liver and digestive complications, so there is a mandatory limit on the amount of arsenic (<0.015%) in tinfoil wrapper and tin layers for food packaging. Arsenic causes a poor appearance and plasticity, and increases viscosity. The impurities content of crude tin fluctuate over a wide range; a lot depends on composition of tin ore concentrate, treatment method and technological process before reduction smelting. And the content range of arsenic is usually 0.5~4%, but it is higher in some factories."

Jan 1, 2012

By Abhishek Asthana

The incineration of Municipal Solid Wastes (MSW) is an attractive process for reducing the volume of the wastes and recovering their energetic value, which, however, requires to be strictly controlled in order to limit its impact on the environment. In this context, we have undertaken the mathematical modeling of the different sections of a typical incineration plant. The combustion of the waste bed, usually carried out on a moving grate, is at the core of the process. This paper presents the 2-dimensional, steady-state model that we have developed for simulating the MSW combustion. The model describes gas flow through the porous waste particle bed, the gas-solid reactions, conductive and radiative heat transfers, drying of the feed, its pyrolysis and the emission of volatile species, combustion of the pyrolysis gases, the formation of char and its gasification by water vapor and carbon dioxide, and the consequent reduction of the bed volume. Pyrolysis kinetics distinguish between cellulosic and non-cellulosic materials and are experimentally derived from our laboratory measurements. The calculated results give a deep insight into the various involved phenomena, an example being the complete consumption of oxygen in a large zone of the bed and the related appearance of a char gasification zone. The influence of various operating parameters, like the temperature and flow rate of primary air, is presented and explained. Finally, the effect of stirring the waste bed on the moving grate is also analyzed.

Jan 1, 2006

By Norbert Hort, Karl Ulrich Kainer, Carsten Blawert, Daniel Fechner

"With the development of new heat resistant magnesium alloys, the automotive industry has introduced several parts to the drive train. The rising number of large magnesium components will result in a higher quantity of automotive post consumer scrap and the changing legislation will force car manufacturers to take magnesium recycling into consideration. So far post consumer scrap has not been used for magnesium alloy production. Quite a reasonable amount of automotive scrap is likely to end up in a mixed light metal shredder fraction. The separation of mixed magnesium scrap according to several alloys is complex. Therefore secondary magnesium alloys made from blended post consumer scrap would be useful. For this work a matrix of potential recycling alloys was prepared by chill casting and high pressure die casting. The materials were investigated for their microstructure, mechanical properties, heat resistance and corrosion properties. The results will be presented in this paper.IntroductionWithin the last ten to fifteen years several heavy magnesium parts have been assembled in passenger cars, such as gear box housings and crank cases [1, 2]. Reasons are the lately developed new heat resistant alloys and the increasing responsibility of automotive manufacturers to reduce the vehicles weight and thereby CO2 emissions. The latter is pushed by international legislation [3, 4]. The rising quantity of magnesium in automobiles will result in an increasing amount of so called post consumer scrap at the end of the vehicles life.So far magnesium recycling was done only for clean scrap that is free from impurities, contaminations and sorted according to a chemical composition or a single alloy respectively [5- 15]. The latter is also called class 1 scrap and mainly consists of sprues and runners from magnesium die casters [15, 16]. For the upcoming automotive post consumer scrap the materials quality strongly depends on the way end of life vehicles are treated. By proper dismantling of old cars, the bigger magnesium components could be collected and possibly treated similar to class 1 scrap [15]. Up to date automotive manufacturers have no uniform recycling system for end of live vehicles. Most probably a considerable quantity of old cars will be shredded. The resulting light metal shredder fraction will contain aluminium and magnesium scrap, both from several alloys. A separation of mixed magnesium and aluminium scrap is feasible according to [17]. Other authors claimed that the grade of separation of magnesium from aluminium is still not sufficient for a proper industrial recycling process of magnesium post consumer scrap [15, 16]. If an automatic sorting is possible it will probably be very expensive [18]. Therefore, so far the main use of post consumer scrap has been the steel desulphurisation and aluminium production [15]. The use of post consumer scrap for magnesium alloy production has been considered already by [15] and [16] but some problems have to be approached."

Jan 1, 2008

This symposium is dedicated to the lifetime achievements of Professor H.Y. Sohn. It covers the scientific fields, processing routes and investigation techniques in which Prof. Sohn has worked during his career and is based in the equally important three topical areas: Principles, Technologies, and Industrial practice. Professor Sohn was General Chair of the very first TMS Fall Extraction and Processing Symposium in 1983 in San Francisco which led to the Annual such symposia as this International symposium. Furthermore, the theme of that symposium was sulfide smelting, which is also included in this symposium. [ ] Professor Sohn was born in a beautiful dynastic capital Kaesung, Korea on August 21, 1941. He received his B.S. degree in 1962 from Seoul National University, M.Sc. in 1966 from the University of New Brunswick, Fredericton, N.B., Canada, and his Ph.D. degree in 1970 from the University of California at Berkeley all in Chemical Engineering. After working as a Research Associate at the State University of New York at Buffalo and as a Research Engineer at Du Pont?s Engineering Technology Laboratory, Dr. Sohn joined the Department of Metallurgical Engineering at the University of Utah in 1974 and currently holds the ranks of Professor of Metallurgical Engineering and Adjunct Professor of Chemical Engineering.

Jan 1, 2006