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By Andrey Tarasov, Erki Unn, Valery Paretsky

"The stability of the markets of energy resources and labor in countries of the Baltic Sea Region including Estonia is determined to a significant degree by the use of combustible shales as fuel and their distillation resulting in generation of up to 70% of non-recyclable waste. The objective of this business plan is to substantiate the investments for establishment of a new facility in Estonia for waste-less and environmentally safe processing of fossil minerals and man-made products generated in the shale industry, as well as other hazardous wastes. The proposed facility will use a basically new waste processing technology developed in Russia - i.e., processing in sparged molten slag This technology eliminates any release of harmful pollutants to the environment and a facility using this technology does not require, therefore, any sanitary protection zone.IntroductionIn the Baltic region, and first of all in Estonia and some other European territories, there are large natural deposits of combustible shale, which due to the lack of other own resources of energy and hydrocarbons for the chemical industry is burned and distilled with low technical and economic efficiency generating large amounts of toxic and highly toxic wastes and intermediate products. Currently, the penalties for disposal of such wastes have grown to such an extent that shale burning and distillation might become unprofitable. This might result in suspension of the given operations, which in turn will affect in an adverse way the markets of energy resources and labor market in those countries. Furthermore, in addition to the “shale problem”, Estonia, similarly to most member countries of the European Union, faces the challange of environmentally safe processing of highly toxic wastes, such as municipal solid wastes, oilpolluted materials, medical wastes and infected materials, spent rubber tires, etc. These wastes are at present stored or processed with release of a significant quantities of extremely toxic cancerogenic substances (dioxins, furans) or collected and exported for treatment at an extremely high cost and with a loss of valuable components contained in these types of waste and often with return of supper toxic processing products."

Jan 1, 2008

By G. Haesebroek

In L969 Metallurgie Hoboken-Overpelt started an industrial plant for the separation of iron and zinc from a concentrated CoCL2 solution. Iron and zinc are extracted in column contactors by a solvent containing 12 vol % of tertiary amines in xylene. The extracted metals are stripped from the pregnant organic phase by precipitation with a NaOH solution at pH LL. In this paper an overview is given of the industrial process. In order to overcome some drawbacks of this process (low flash point of the diluent, reagent consumption, batchwise stripping) an alternative solvent extraction process has been examined. In this alternative process, iron and zinc are extracted with an or¬ganic phase containing 50 vol % of TBP in Escaid 110. The pregnant solvent is stripped with water in conventional mixer settlers. Despite the ability of this process to overcome most of the inconveniences due to the use of tertiary amines, it suffers from the poor stability of TBP in concentrated chloride solutions, resulting in unavoidable and inacceptable precipitation phenomena in the stripping section.

Jan 1, 1988

By Eoghan T. M Doyle

Oxide mixtures of nickel (NiO), cobalt (COO) and chromium (Cr203) were prepared with graphite in stoichiometric amounts and the powder mixtures were compacted to produce cylindrical pellets. The composition of chromium oxide in these mixtures were varied. Pressed pellets were reduced in a flowing stream of argon-4% hydrogen gas (500 ml/min). Both slow and rapid heating methods were adopted to raise the temperature of a pellet during reduction of oxides to form superalloy powder. The reduction temperature was varied between. 1523 and 1623K. The effect of heating rate and niobium oxide addition on the microstructure of the superalloy produced was studied by using ordinary light and scanning electron microscopes. New phases formed as a result of reduction were identified by X-ray powder diffraction technique. The mechanism of reduction of oxides together with the microstructure of NiCrCo alloy are discussed. The thermodynamics of formation of ternary alloy phase is elucidated on the basis of binary phase equilibria and Gibbs free energy of mixing data for the constituent alloy compositions.

Jan 1, 1992

By H. Kamiya, H. Hasegawa, M. Nojiri, S. Matsui, Y. Fukuda, M. Tsukada

"The present paper focuses on the action mechanism of anionic polymer dispersants in dense Si3N4 and SiC suspension. An atomic force microscope (AFM) was used to determine the relationship between the macroscopic suspension viscosity and the microscopic adsorbed structure of a polymer dispersant at the solid / liquid interface. The surface interactions within the suspensions were analyzed in various dispersant pH and additive conditions. The addition of an anionic polymer dispersant decreased Si3N4 and SiC suspension viscosity and increased electro-steric repulsion force on the non-oxide surface in solution at pH> 6 which was the isoelectric point of the materials. It was assumed that the increase of repulsive force was promoted by a hydrophobic adsorption of polymer dispersant on the non-oxide particles.IntroductionThe surface of silicon nitride and silicon carbide powders in a water suspension system has quite a complex molecular structure. In the case of Si3N4, hydroxyl and ammonium groups form on the surface and the pH of the suspension is increased from neutral to about 10 due to surface oxidation. The particle surface is negatively charged in alkaline solutions (pH=10), because the isoelectric point of silicon nitride exists in the pH range from 5 to 6. However, in spite of charging the negative surface charge, an anionic polymeric dispersant is generally used for the reduction in slurry viscosity.In dense SiC suspensions, an anionic polymer dispersant is generally used in order to disperse aggregates and reduce the suspension viscosity, too. Since an anionic dispersant is used in alkaline solutions higher than the isoelectric point of silicon carbide, the dispersant adsorbed on the negative charged surfaces of SiC.Few researchers have discussed and estimated the adsorption mechanism and structure of anionic polymeric dispersants on silicon nitride and silicon carbide surfaces. This is because it is difficult to observe the structure and measure the interaction at the solid/liquid interfuce directly. However, new developments in surface-force measurement technology have enabled the determination of non-DLVO type interaction for analyzing aggregation behavior2. The use of the AFM for analyzing the effects of various surfactants and co-polymers on colloidal dispersions and solid surfaces has also begun to rapidly expand to characterize the interaction between solid surfaces."

Jan 1, 2000

By Norihiro Murayama

The hydrothermal syntheses of zeolites from coal fly ash were carried out using NaOH and KOH as an alkali source. The cation exchange capacity (CEC) and the ion exchange selectivity were investigated for the zeolites synthesized by a hydrothermal treatment. The effective usage of the zeolite as a cation exchanger was considered from the viewpoint of engineering. Zeolite P, HS (hydroxysodalite) and K-CHA (potassium-chabazite) are mainly formed as zeolite species in NaOH or KOH solution at 393K. The zeolite P and K-CHA have a large exchange capacity as a cation exchanger. The cation exchange isotherms of various monovalent and divalent cations with various zeolites are investigated. The order of selectivity of the zeolites is as follows, NH4+> K+> Li+.For the divalent cation, the largest removal amount is obtained for Pb2+ in the low equilibrium concentrations below 0.2mmol/dm3, and almost perfect removal can be achieved for Pd2+. The order of selectivity of zeolites in low concentration is expressed in the following order; Pb2+> Co2+> Cd2+> Ca2+> Mg2+> Ni2+. Ii is considered the zeolites obtained from coal fly ash can be used as an excellent cation exchanger.

Jan 1, 2006

By Selvin Yesilay, Guray Kaya, Bekir Karasu, Asli Cakir

"In this investigation, the wastes of Eti Maden Kirka Boron Company of Turkiye were evaluated in the production of diopside and anorthite-based glass-ceramic glazes suitable for porcelain tiles fast and single-fired under industrial conditions. First of all, high wear resistant frits were produced with the use of concentrator and derivative borax wastes. Second of all, pre-engobed porcelain tile bodies were coated with the standard and newly produced frit-based glazes and industrial fast single-firing was employed. Final products were undergone to the certain standard tests to determine their Vickers hardness, wear resistance, thermal expansion coefficient values, gloss and coloring parameters. The micro-structures and phase formations of the fired glazes were also studied. Consequently, it was confirmed that the utilization of borax solid wastes in fast single-fired porcelain tile glass-ceramic glazes is possible. Introduction Porcelain tiles were introduced at the end of 1980s by Friandre, one of the leading Italian porcelain manufacturers. The American National Standard Specifications for Ceramic Tile defines porcelain tiles as: dense, smooth, impervious (with water absorption value less than 0.5 %) and stain resistant [1]. The excellent technical performances for ceramic tiles, such as mechanical, wear, frost and chemical resistance that make their use possible in indoor and outdoor building applications [2-3]. In the last decade, the growth rate of the global production of porcelain tiles increased more than those of other ceramic products; in fact, the technical properties of porcelain tile, coupled with even more improved aesthetic appearance, gave it a prominent role on the tile market [2]. Glass-ceramics are composed materials of one or more crystalline phases immersed in a residual glassy phase [4-5]. Glass-ceramic technology is based on controlled nucleation and crystallization of bulk glass [6]. The concepts of controlled crystallization of glass designate the separation of a crystalline phase from the parent glass in the form of tiny crystals. Their growth rate and final size are controlled by a suitable heat treatment [7]."

Jan 1, 2008

By Isabela Leao Amaral da Silva, Alice Barreto Bevitori, Frederico Muylaert Margem, Victor Bastos da Silva, Sergio Neves Monteiro, Artur Camposo Pereira

"The jute fiber is one of the most rigid natural lignocellulosic fibers, which has since the last decade been investigated as possible reinforcement for polymeric composites. In the present work, the tensile properties of DGEBA/TETA epoxy composites reinforced with jute fibers with different diameters were investigated. Composites with volume fractions up to 30% of continuous and aligned jute fibers were tensile tested at room temperature to evaluate the ultimate strength, elastic modulus and total strain. For each volume fraction, separated fibers with smaller larger diameters were tested. The results indicated that the tensile properties tend to improve with increasing volume fraction of the thinnest jute fibers. The role played by the fiber/matrix interaction was analyzed by scanning electron microscopy.IntroductionThe interest of this research is to develop composites with epoxy resin matrix reinforced with continuous and aligned jute fibers, for applications in various industries, including construction and automotive industry. Conflicts related to the use of non-renewable forms of energy are increasing the interest to enter the market to replace natural materials, synthetic materials synthetics have a higher power consumption in its manufacture [ 1-4].Therefore, applications of natural lignocellulosic fibers obtained from cellulose-based plants are receiving increased attention as an alternative to replace more environmentally correct nonrecyclable materials, energy intensive and glass fiber composites in [5-6]. The use of composites reinforced with natural fibers is a reflection of the concerns with environmental issues such as pollution caused by waste that is not biodegradable or cannot be incinerated and climate change due to C02 emissions associated with the processes of intensive energy and also motivates this work to develop self-sustaining, since natural fibers generate a source of income, especially in developing countries, where most originate, encouraging the cultivation of non-food agriculture [7-9]. Additionally, it is worth also remembering that these fibers come from renewable sources, in addition to being abundant, inexpensive and have a relevant set of mechanical properties [10]."

Jan 1, 2013

By Jian Wang, Hongyang Cao, Binxiu Wu, Junhong Li, Jimin Wang

"The enrichment and separation of scattered metal indium component in the pressure leaching solution with sulfuric acid from vacuum furnace germanium slag were studied by iron substitute and P204 extraction, which is supplied by shaoguan smelter. The experimental results show that the extracting power of P204 for indium from pressure leach solution is powerful. The optimal technological condition were the ratio of P204 and sulphonating serosene 3:7, phase ratio 1:3, solution pH 1.2, and extracting 5 minute. The enrichment indium solution of 21.7 g/L In at 95.2% recovery ratio was obtained by three-stage counter flow extraction and four- stage counter flow stripping.IntroductionScattered metals, such as Indium and germanium, were inriched as intermediate product or by-product during the metallurgy process of other non-ferrous metals, such as lead, zinc, copper and tin. For example, the indium and germanium were inriched in vacuum furnace germanium slag, which is the by-product of zinc vacuum distillation operation from hard zinc. It is difficult to recovery the indium from the vacuum furnace germanium slag, because the indium content is low, and the chemical composition and phase compositon were complex.Recovery indium from bearing indium zinc slag was researched extensively, such as pressure acid leaching, high temperature evaporation, solvent extraction method[l-7], acid leaching method has the advantages of high leaching rate, which can be separated hydrochloric acid, sulfuric acid and silicon fluoride acid systems. Solvent extraction method has the advantages of low production cost, fast reaction speed, high enrichment ratio, and simple operation."

Jan 1, 2013

By Katie Schumacher, Greg Roset, Dayle Flynn

The Columbus Processing Complex of the Stillwater Mining Company began operations at Columbus, Montana in 1990 based on electric furnace smelting treating a precious metals concentrate from the nearby Stillwater mine and mill. Since that time, the smelter plant has been expanded in stages in order to treat recycled materials in addition to the concentrate. This paper describes a number of changes made at the plant to effectively handle recycled materials.

Jan 1, 2014

By Qin Hua, Xiangru Chen, Qijie Zhai, Yongsheng Yan, Liang Chang

"In this paper, pure bainite ductile iron and their alloying form of 0.2wt% niobium were prepared by a controlled cooling heat-treatment. The effect of niobium alloying on the microstructure, hardness and impact toughness of bainite ductile iron was studied. The results show that adding niobium effectively improves the hardness and toughness of bainite ductile iron. The hardness and the impact toughness of niobium-alloyed bainite ductile iron were investigated by varying the temperature at which samples were fed to the incubator.IntroductionThere are two essential methods to prepare the bainite ductile iron: isothermal quenching [I-31, and alloying [4• 51• Isothermal quenching process is very time and energy consumable, concerned as a high cost technique for mass production. Besides, there are certain limitations on the size and shape of castings in this process. In addition, it potentially harms the environment. As for the alloying, Ni, Mo, and Cu have to be utilized to obtain bainite. However, the large demand and high cost of Ni makes it not feasible in practice.It is well known that niobium can promote the formation of carbon compound, and improves the stability ofundercooled austenite, which is preferred to the increase of the hardenability. Previous studies showed that niobium could refine the grain and improve the mechanical properties of gray cast iron [6-81 • Therefore, in the present work, the effects of niobium and the temperature at which samples were fed to the incubator on the microstructures and properties of niobium alloyed bainite ductile iron were investigated."

Jan 1, 2014

By M. Rosales

By a physical and mathematical modeling, the behavior of the tri-dimensional waving, and the movement of the gases at the Teniente Converter was studied. The mathematical model considers the condensed phases of white metal and slag, along the gas phase, and includes the k-e model for the turbulence description. Both the physical model and the mathematical model allow to conclude that from a fluidynamic stand point the Teniente Converter clearly can melt 3000 tpd of concentrates. Also, both models are suitable to predict the slag fluidynamics and its spacial distribution inside the Teniente Converter, and the splashing in the tuyere zone as well.

Jan 1, 2006

By Hye-Sung Kim, Dong-Wha Kum, Gyeungho Kim

"Mechanical alloying is an effective way to finely distribute inert dispersoids in AI-TM (TM is a transition metal element) systems. It is considered that high melting point aluminides are formed by precipitation from the supersaturated aluminum matrix. The analysis is based on the fact that much higher content of TM than the solubility limit can be dissolved in alpha aluminum during the high energy ball milling. Nonetheless, the role of undissolved TM particles affecting the formation of aluminides is not suitably considered. In this paper, authors present experimental observation on the formation of Ab3Ti particles from mechanically alloyed AI-Ti alloys in the hyper-peritectic region. This study showed that, in the mechanically alloyed AI-20wt%Ti specimen, intermediate phase of cubic Ab3Ti and tetragonal AIz4Tis formed at 300 - 400°C and 400 - 500°C, respectively, before the MA-state reaches to the global equilibrium at higher temperatures. The formation behavior of Lh- Ab3Ti is interpreted by interdiffusion of Al and Ti in solid state based on the fact that large amount of nano-sized Ti particles exist in the milled powder. Present analysis indicated undissolved Ti particles of nanosize should have played an important role initiating the formation of Ab3Ti phase during annealing.IntroductionInterest in the hyper-peritectic AI-Ti alloys is based on industrial demand for high-modulus and high-temperature aluminum alloys. Earlier works on hyper-peritectic AI-Ti alloys with 4 to 12wt%Ti show that these alloys are strong at ambient temperature and maintain high strength above 300°C when titanium-trialuminide (e.g., Ab3Ti) is finely distributed in the aluminum matrix [1,2]. High melting point and high stiffness with low density of AbTi make the AI-Ti alloys strong with greater thermal stability while keeping weight savings as much as possible. Titanium in aluminum shares other merits of transition metal additions because Ti solubility in Al is low (i.e., 1.l5wt%Ti at 665°C and virtually zero below 400°C), and fine dispersion of Ab3Ti particles is readily accomplished and resists grain coarsening effectively."

Jan 1, 1996

By Katsuyasu Sugawara, Takuo Sugawara, Shin-ji Abe, Tadakazu Kagami

"In order to clarify the mechanism and to obtain the fundamental data for heavy metal recovery from an incinerator ash by chlorination, pure chemical reagents, zinc oxide and lead oxide or the fly ash blended with calcium chloride and silicon dioxide were heated up to 1000°C in a nitrogen stream. Thermogravimetric curves of the samples with the chlorinating reagents indicated that solid-liquid reactions accelerated the chlorination and release of metals from the solid phase. The formation of liquid phase of calcium chloride played an important role on effective recovery of zinc and lead at lower temperatures below 800 °C. Although zinc and lead could be decreased in the incinerator ash without chlorinating reagents, addition of chlorinating· reagents enables the removal of metals in high extent· at lower temperature.IntroductionFly ash is discharged about 3,000 tons/day (about 110 million tons/year) from incinerators of municipal solid waste in Japan and mostly fly ash is disposed in landfills. Fly ash includes heavy metals e.g. zinc and lead. Since untreated fly ash caused hazardous leaching problems, Waste Disposal and Public Cleaning Law was revised in 1992, fly ash being designated 'specially controlled' general waste. Fly ash must be disposed by the following suitable, intermediate four methods: [I] Cement- Solidified Method, [2] Immobilized Chemicals Method, [3] Melting Solidified Method, [4] Acid Leaching Method, permitted by the Ministry of Health and Welfare, Japan."

Jan 1, 2000

By Andrzej Warczok

Liquid slags produced in smelting of copper concentrates contain copper in a dissolved form as well as mechanically entrained inclusions of copper matte. Coalescence and sedimentation of inclusions during slag cleaning plays a key role in copper recovery. Liquid matte inclusion in a molten slag presents a system of metallic conductor in an ionic solution. Constant electric field induces migration of the matte droplet along the current lines. Additional phenomena occur in a system under crossed electric and magnetic fields. Electromagnetic buoyancy force acting on the inclusion affects its settling rate. Electromagnetic buoyancy force of insulating and metal spheres has been measured in a liquid synthetic slag. It was found that depolarisation of the metal sphere, related to the electrode reactions occurring in the surface, plays an important role in the determination of the direction and magnitude of the electromagnetic force. On the basis of the existing theories and results of measurements a mathematical model describing the behaviour of metallic inclusions in the liquid slag under the influence of crossed electric and magnetic fields was developed. Simulation of behaviour of copper matte inclusions under crossed fields showed trajectory of motion in a liquid slag as a function of the slag properties and the inclusion size.

Jan 1, 2003

By A. A. Hejja

"Liquidus temperature and electrical conductivity data measured on synthetic slags were modelled by the use of neural nets (NN). In this work the applied multilayer feedforward NNs were trained by a conjugate-gradient optimisation for which a three layer formulation was used. Very good fits were obtained for both the liquidus temperature and the conductivity data. The synthetic slags were prepared from pure oxides to represent a wide range of compositions likely to be encountered in ferromanganese and silicomanganese smelting. The slag constituents were in the following range: Mn0;5-30%, Ca0;20-35%, Mg0;5-15%, Si02;27-58%, Al20 3;5%. Liquidus temperatures varied from 1300° to 1380° and increased with increasing basicity ratio. The electrical resistivity of slags decreased with the increase of basicity ratio from 0.55 to 1.1 but above 1.1 basicity ratio the resistivity tended to increase depending upon the MnO content.Neural NetsVarious neural net (NN) topologies such as Hopfied nets, Hamming nets, Carpenter/Grossberg classifiers have been discussed in some detail by Lipmann (1). In this work, the applied multilayer feedforward NNs are not trained by backpropagation (BP) using the generalized delta rule (2) (GDR), but by a conjugate-gradient optimisation [3,4] - a procedure similar to that proposed by Barnard and Cole [5]. A neural net is capable ·of learning the non-linear functional relationship existing between a set of inputs and outputs [ 6]. In this capacity a neural net is used to determine the functional relationship that exists . between N dependent and independent variables, which characterize the system under consideration For a three layer neural net [1] the following function may be formulated, which relates X; inputs to the output Y 0 from node o:"

Jan 1, 1997

By John A. Clark, Danylo Oryshchyn, Casey Carney, Stephen Gerdemann, Cathy Summers, Thomas Ochs

"Limited analysis of combustion gas streams where carbon capture is not of interest is done mainly to ascertain operation parameters. Stringent regulations on acid gases and particulates promote careful flue gas analysis. Unregulated components are typically not analyzed. Typically not more than four points (two in the boiler, and one each in the flue and the stack) are sampled. A successful oxy-fuel process with carbon capture and compression is anticipated to require as many as 12 sample points with analysis for water, nitrogen, oxygen, argon, NOx, SOx, and carbon monoxide. Carbon dioxide captured for beverages produces a high value product and the cost associated with analysis is warranted. However, carbon capture for disposal must keep all costs to a minimum. This paper will compare alternative approaches for cost-effective sampling and analysis of the carbon dioxide product streams from oxy-fuel combustion, through all stages of production through compression and pipeline/vessel delivery.IntroductionAnalysis of gases in an oxy-combustion process with carbon capture is essential to the operations of the oxy-fired boiler and the subsequent collection, compression, and purification of carbon dioxide. The process is charged with pure oxygen and not-so-pure carbon in the form of coal at the front end, generating a product of mainly carbon dioxide with traces of argon, nitrogen, sulfur compounds, nitrogen compounds, oxygen, hydrogen, and mercury. It is possible that hydrogen chloride and hydrogen sulfide may also be present in trace amounts [1]. The trace components primarily come from impurities contained in coal such as water, sulfur, nitrogen, and volatile organic compounds. Coal also contains a good deal of mineral matter that is transformed into ash during combustion, becoming particulates that can complicate the analysis regimes utilizing standard analytical equipment."

Jan 1, 2010

By Michael S. Moats, Jan D. Miller, Wlodzimierz W. Zmierczak

"For many, hydrogen in a pure hydrogen economy would be like natural gas in today’s energy economy. Unfortunately, hydrogen’s physical properties are unsuited to the energy market’s requirements in terms of packaging, storage, transfer, and delivery. In this paper, a hybrid energy economy that packages hydrogen chemically on carbon atoms from various sources including recycled carbon dioxide is introduced and discussed. For this new hybrid energy economy to become a sustainable reality, the ability to recycle carbon dioxide and use hydrogen to create an appropriate energy product, such as dimethyl ether (DME), is needed. DME is recognized as a potential next generation, “beyond-petroleum”, environmentally benign commodity for energy storage and distribution. It is expected that to maximize the sustainability of the proposed hybrid energy economy, “green” hydrogen will be utilized. The “green” hydrogen would be created by the electrolysis of water powered by renewable energy sources, such as solar, wind or geothermal heat.IntroductionWith the growing concerns surrounding trends in global warming and increasing concentrations of “greenhouse” gases, such as CO2 and CH4, efforts to mitigate the emission of these gases from industrial sources are growing. With respect to CO2, the demonstrations of various capture and sequestration methods are underway around the world.The sequestration of CO2 is mainly focused on storing the gas underground or deep in the ocean. The Intergovernmental Panel on Climate Change (IPCC) estimates that 2000 Gtonnes of CO2 can be stored underground in depleted oilfields, un-minable coal beds and other geologic features [1]. Additionally CO2 may be stored at the bottom of the ocean. The lure of storing carbon dioxide in depleted oilfields or un-mineable coal seams is that an economic benefit (enhanced oil or methane recovery) can offset the costs of gas capture, transportation and storage. Unfortunately, all of these storage methods have potential for the release of CO2 or CH4 back into atmosphere or creating environmental damage (mobilizing heavy metals, disrupting deep sea ecology)."

Jan 1, 2008

By Samson Adeosun, Sanmbo Balogun, David Esezobor

"Iron and steel making processes give rise to large amounts of usable and unusable materials, the latter generally being termed wastes. It is sometimes difficult to distinguish between re-usable by-products and wastes which cannot be sold or land-filled. Much depends on circumstances such as the local market for the material. This can itself vary from time to time with by-products which cannot be used or sold becoming wastes and vice versa. This paper defines the concept of “waste-free technology”, discusses its development in the steel industry and highlights the benefits of the technology to the manufacturing sector and the environment. The paper also articulates how the “waste-free” technology could be applied in the proposed Ajaokuta integrated steel plant in Nigeria.IntroductionIn the past, nature was considered an inexhaustible store. Its resources were consequently exploited and waste products therefrom were discarded. Today, attitudes have not changed appreciably even as raw materials cost rise by the year to pose a series of socio-economic problems, which, among others, may include the rational and optimum utilization of resources, environmental protection and reduction of waste formation. Consequently, industrialists now face unexpected regulatory pressure in areas of pollution prevention, waste minimization and hazardous waste disposal.Iron and steel making processes give rise to significant amounts of usable and un-usable materials, the latter generally being termed waste. It is sometimes difficult to distinguish between re-usable by-products and wastes which cannot be sold or land-filled. Much depends on circumstances such as the local market for the material. This can itself vary from time to time with by-products which cannot be used or sold becoming wastes and vice versa. In this paper, the term waste refers to those materials that are either irrationally utilized or, land-filled and part of the byproducts that are not utilized. It includes that part of used materials which is not incorporated into the products manufactured during a process stage and which in contrast to reuseable materials, is considered not suitable for any further use, owing to technical or economic factors. In general, these materials are inorganic and parts of them are either utilized or passed to the other processes; the other part should be disposed of using well-established waste disposal practices to avoid any environmental threat.Thus, creative methods must be developed to modify the manufacturing processes to reduce emissions and process wastes by fully utilizing all resources. One method of eliminating the negative effect of waste formation is the use of purification and cleaning structures (pollution control system, PCS). These are, however, quite expensive."

Jan 1, 2008

By Shilai Yuan, Huimin Lu, Zhijiang Gao, Panpan Wang

"Solvent refining of silicon through using Si-Al melts is a valid method to remove the impurities from metallurgical grade silicon (MG-Si) melt. The thermodynamic behavior of impurities Fe, Al, Ca, Ti, Cu, C, B and P in MG-Si during the solidification of MG-Si was studied based on the available thermodynamic parameters and experimental data. The morphology of inclusions was investigated by Scanning Electron Microscope (SEM). The chemical composition of inclusions in MG-Si and Al-Si melt was analyzed by EPMA. It is found that the amount of white inclusion reduces and most impurities are solved into the Al-Si melts. After solidification of Si–Al alloy using induction heating and acid leaching, impurities can be effectively removed. The solidification of silicon from the Si–Al melt is found to be more effective for purification than general silicon solidification.IntroductionPhotovoltaic energy is one of promising energy resources in a sustainable society because of its inexhaustibility and cleanliness. Although the production and installation of solar cells have increased significantly during the last decade, the cost of solar cell installation is still high. Multicrystalline silicon has now become the main material in the photovoltaic market because of its low production cost and because of the relative high conversion efficiency of solar cells made from this material, which has been studied for a long time [1-3].Electronic grade (EG) silicon (99.9999999% Si) is commonly used as the raw material to produce SOG-Si (99.9999% Si). Silicon produced from the chemical routes restricts the development of solar cells due to environment threaten, high energy consumption and low productivity. Purification of metallurgical grade silicon (MG-Si) is a low cost, environment friendly method. Although several metallurgical processes such as directional solidification, vacuum refining and electron beam melting [4], have been developed, the cost reduction and refining efficiencies for manufacturing silicon is still have to be further optimized.In the purification process, it is difficult to remove boron and phosphorus by the conventional metal refining method. The refining efficiency depends on the segregation behavior of different elements in solid silicon and the liquid phase. The segregation ratios of all investigated impurities were found to be much smaller than the segregation coefficients between solid and liquid Al-Si melts [5]. For instance, the segregation coefficient of B in Si is 0.8 at the silicon melting point (1687K), whereas it is around 0.2 when silicon is solidified from Si-Al melt at 1273K. For phosphorus the segregation coefficient is 0.06 when silicon is solidified from Si-Al melt at 973K°C, which is much less than 0.35 for recrystallization from liquid silicon. Since the segregation coefficient of boron in silicon is 0.8, it cannot be removed by directional solidification."

Jan 1, 2014

By Zviad Kovziridze

The problems related to the production and research of SiC-Si3N4 composite are presented. The technology of producing the protective casings for tips and thermocouples is developed. Optimum composition charge and technological parameters are defined. The results of casing testing at production plants are presented.

Jan 1, 2006