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By S. K. Kawatra

A growing concern for pyrometallurgical operations is the generation of airborne particulates. These particulates can be generated by combustion processes, or by materials handling. Regulation of these particles by the EPA has become progressively more stringent, first for particulates finer than 10 micrometers (PM10), which are particles fine enough to be inhaled into the lungs. Then, restrictions were introduced on emissions of particles finer than 2.5 micrometers (PM2.5), which are fine enough to become embedded in lung tissues. The next stage of regulations is likely to be ?nanoparticulates,? particles finer than 100 nanometers, which are in a size range where their very high surface area leads to enhanced reactivity. While all of the health effects due to nanoparticulates have not yet been determined, there have been enough studies to indicate that there is a problem, and restrictions on nanoparticulate emissions are only a matter of time. In this paper, it will be demonstrated that dry handling, comminution, and combustion sources represent a significant concern for both PM and nanoparticulate emissions. In regards to dry handling, the effects of utilizing effective dust suppressants on PM and nanoparticulate emissions will be explored.

Jan 1, 2006

By V. A. Bryukvin

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

Jan 1, 2006

By Hideki Yamamoto, Junji Shibata

"The chemical reactions of fluoride and chloride gases with metal chloride or metal oxide are utilized as an effective treatment for harmless disposal. These chemical reactions can be adopted in the temperature range of 80°C~400°C, which is lower than that in the combustion treatment (800°C). Reaction products are metal fluoride or metal chloride which are a harmless and a valuable chemical material as one of new resources. This paper, concerns with a new harmless disposal treatment of toxic global warming gases.IntroductionNew technology to make fluoride and chloride gases such as NF3, CF4, SF6 BF3, Cl2 and BCl3 harmless has been developed and a new concept on the removing toxic gas to be used in the advanced process of materials has been established. The fluoride gases ~re toxic and special type of gases to be used in the process of manufacturing semiconductors and their specific applications include the dry etching of semiconductors, cleaning of CVD systems, an oxidation agent for rocket fuel etc. Especially, NF3 is also attracting an attention as a high-energy source for chemical laser systems. As a fluoride gas like NF3 is, however; toxic and highly stable chemically, if discharged into the atmosphere, it is liable to cause far-reaching adverse influences on global warming in the same manner as carbon dioxide gas and feron gas.Up till now, the combustion treatment method has been adopted for the disposal of the gas, and when treating the gas by high-temperature combustion (800""C), the generation of nitrogen oxides (NOx), sulfur oxides (SOx) and hydrogen fluoride (HF) have been confirmed: These chemical substances are not only linked with an intense c0rrosion of the combustion systems but also create the generation of atmospheric pollution and acid rains, and therefore, constitute a serious social issue."

Jan 1, 2000

By Adam Powell, Soobhankar Pati

"Solid Oxide Membrane (SOM) Electrolysis is a new energy-efficient zero-emissions process for producing high-purity magnesium and high-purity oxygen directly from industrial-grade MgO. SOM Recycling combines SOM electrolysis with electrorefining, continuously and efficiently producing high-purity magnesium from low-purity partially oxidized scrap. In both processes, electrolysis and/or electrorefining take place in the crucible, where raw material is continuously fed into the molten salt electrolyte, producing magnesium vapor at the cathode and oxygen at the inert anode inside the SOM. This paper describes a three-dimensional multi-physics finite-element model of ionic current, fluid flow driven by argon bubbling and thermal buoyancy, and heat and mass transport in the crucible. The model predicts the effects of stirring on the anode boundary layer and its time scale of formation, and the effect of natural convection at the outer wall. MOxST has developed this model as a tool for scale-up design of these closely-related processes.IntroductionSolid Oxide Membrane (SOM) Electrolysis is a variation on the Hall-Héroult process for molten salt electrolysis of oxides which promises to solve many of the problems of its predecessors. Magnesium in particular is both soluble in molten salts and highly reactive, such that it migrates to the anode and reacts with the oxygen or C02 anode product, reducing current efficiency to as low as 10-20%. But a zirconia solid electrolyte between the molten salt and anode blocks this reaction, boosting current efficiency to at least 90%. Separating the anode from the molten salt also opens up anode material selection to liquid metals and SOFC cathode materials such as Lai.xSrxMn03 (LSM) and YCr03. And zirconia's selectivity makes the oxygen by-product very pure."

Jan 1, 2012

By Markus A. Reuter, Antoinette van Schaik

"Product design engineers select from a wide range of materials and combine them into multimaterial product designs. These include various materials (metals and non-metals) which are complexly integrated (e.g. welded, glued, alloyed, layered). The recycling/recovery rate of consumer products are determined by the different materials and alloys used, but also by the particle size and multi-material particle composition after shredding (combination of materials due to design). Eco-design (for recycling) and Design for Recycling (DfR) can only be conducted if the interconnectivity of material/metal in various unliberated materials is accounted for and its effect on material and energy recovery can be linked back to design. This paper will discuss the basic principles of these DfR models and it is shown how these tools (i) are linked Computer Aided Design (CAD) and Life Cycle Assessment (LCA) software, (ii) affect conceptual design specifications of products, (iii) integrate the complex detail of the recycling system and recyclate quality and hence (iv) make recycling an integrated part of the product system. Furthermore, it is shown how these assessment tools and models can be applied for benchmarking of the recyclability and environmental damage created by the recycling of end-oflife consumer goods in order to e.g. (i) provide the (original) equipment manufacturer with knowledge and solutions to support product stewardship and Extended Producer Responsibility; (ii) create awareness of the consequences/benefits of design, products and recycling systems to manufacturer, designer, legislator, recycler etc.; and (iii) assist the consumer in their choice of consumer goods from an end-of-life point of view.IntroductionA first-principles basis is required in order to be able to simulate and predict the recycling/recovery behaviour of products facilitating Design for Recycling (DfR) and Eco- Design. This links recycling technology and the environmental consequences of recycling directly to product design."

Jan 1, 2008

By J. M. Tourre

1995 have seen a continuation of a positive trend in the Rare Earth industry The availability of a greater diversity of Raw Material has brought additional flexibility to the Producers permitting better economics China remains the major raw material source; Chinese concentrate producers have increased capacity in 1995 (Baotou, Sichuan, etc) China's role in the Rare Earth industry will continue to evolve; the acquisition of a majority equity position by San Huan/CNNC will have a significant impact on both the Rare Earth and Magnet markets Chinese producers are increasing the quality of their products and realize their true values Chinese market, itself, is also changing as the internal needs for separated rare earth's grow Already already producer of Lamps, Loudspeakers, Magnets, and TV tubes, China is in an unique position where the potential of its internal market might be more promising than the prospects outside China 1995 has also seen the application market become more diverse and complex. There are new applications growing at a very strong pace (such as battery alloy), applications that are now penetrating their target markets with significantly increased growth rates (such as bonded NdFeB), and some applications that became more complex requiring much more sophisticated products (such as catalysis). Rare Earth producers have to spend significant ressources in order to monitor the market trends in order to predict the demand and then adjust their raw material mix. Even though there is a greater diversity of raw material available, there is still some Rare Earth elements that are in excess, while other are just in balance. As a consequence rare earth producers invest heavily in R&D in order to develop new applications for these excess elements.

Jan 1, 1997

By O. Tiitu

Drying is a unit process that has numerous applications in metallurgical process industry. Kumera Technology Center is a worldwide equipment and process supplier, who has expertise on both direct and indirect drying. In a conventional direct heated dryer, the required energy is obtained from combustion of fossil fuels emitting a considerable amount of off-gases. However, thermal energy can be already available in some metallurgical plants such as modem copper smelters where steam is produced by waste heat boilers of flash smelting furnaces. The total volume of off-gases, and especially the amount of harmful gases, released into atmosphere can be remarkably reduced when using steam as an indirect energy source for drying. Kumera Technology Center has developed a new type of steam dryer for drying of, for example, abrasive copper concentrate with silica sand. In the development of the new dryer, Kumera's approach has been to combine the best properties of both the existing steam dryers and the rotating drum dryers. In the design, special attention has been paid to overcoming the reported problems of excessive wear and clogging of steam tubes and to reducing the required maintenance operations. The Kumera Steam Dryer, having a patented flexible steam tube arrangement inside the rotating shell, has a high effective heating area - drum volume ratio without leading to problems with build-up and clogging. It can also be easily scaled up so that a single dryer can dry all of the feed for a large flash furnace. In this paper, we will present the operational and maintenance experiences from two years operation of the first full-scale Kumera Steam Dryer at Norddeutsche Affinerie Aktiengesellschaft in Hamburg, Germany. We will also provide an overview of the future developments with respect to construction and scale up as a response to market demands.

Jan 1, 2002

By Douglas M. Matson, Rongbiao Gu, Christopher San Marchi, Anil Saigal

"Hydrogen embrittles most structural metals, although the form and magnitude of embrittlement depends on the source of the hydrogen as well as the stress in the metal. Hydrogen fuel cell systems typically store gaseous hydrogen fuel at high-pressure, which provides both a source of hydrogen and high stresses in the containment materials. Understanding and measuring the effects of hydrogen on the mechanical properties of common structural metals, especially fatigue properties, is important for safe, long-term operation of such systems. This work explores the use of thermography to efficiently and quantitatively evaluate hydrogen-assisted fatigue of type 304 austenitic stainless steel. In particular, thermographic analysis was used with rotating-beam fatigue testing and shown to provide repeatable results which are in general independent of test cycle frequency while reducing test times by several orders of magnitude. The effects of hydrogen were studied by thermally precharging fatigue test specimens in gaseous hydrogen prior to thermography-assisted fatigue testing and then compared to testing of non-charged specimens. Hydrogen-precharging increased the strength of this type 304 austenitic stainless steel and increased the fatigue life by a factor of about 50-100.IntroductionThe world is facing a severe energy and environmental challenge: how to provide competitive and clean energy for its citizens in light of an escalating global energy demand and concerns over energy supply security, climate change and local air pollution. As a carbon-free energy carrier, hydrogen provides a promising vector for storing and distributing renewable energy. Hydrogen is an important industrial gas that is used extensively in many industries. However, with growing demand for clean energy, hydrogen fuel cell systems are being developed for use in consumer products, such as fuel cell vehicles, which changes the landscape for safe design of high-pressure gaseous hydrogen systems."

Jan 1, 2012

By Donghai Li, Cheng Pan, Xuyang Liu, Xuewei Lv, Chenguang Bai

"Fine chromite ore is the common raw material to produce ferrochrome alloy through the submerged electric furnace process. The electric resistivity of fine chromite ore plays an important role in the operation efficiency because it determines the current distribution. The effect of particle size and the contact area of the particles on electric resistivity for several of chromite were investigated at room temperature, and the relationship between the electric resistivity of mixed particles and the volume fraction of lump ore to fine ore was also studied. The results shown that the electric resistivity increases with the increase of particle size, and the electric resistivity of mixture decreases with the increase of volume ratio of fine ore.IntroductionChromium is one of the most important alloying elements in manufacturing of stainless steel that used at high temperature and corrosive environment applications [I, 2]. As the raw materials to be charged into the steel, ferrochromium alloys and charge chromium are produced directly by smelting of chromite ore with the reducing agent in submerged electric arc furnace (SAF). During the process, the oxides of chromium and iron were reduced by carbon and meanwhile the electrical energy were consumed [3,4]. The ideal industrial process is to achieve high recovery level of Cr and Fe with minimal power consumption. In SAF process, the electric resistivity of charge stock has significant effect on the current distribution, which determines the heat distribution, molten bath structure and chemical reactions in the furnace. High resistance of the charge is desired to reduce the current distribution through the charge stock, thus the electrodes may insert into the charge stock with proper depth to form a high temperature arc heat source, and proper smelting can be realized[5]."

Jan 1, 2012

By Animesh Jha

Univariant diagrams are constructed for the reduction of nickel and cobalt oxide and sulphide minerals. The results from the carbothermic and hydrogen reduction of sulphide minerals are compared. The importance role of lime and calcium sulphate in controlling the emission of sulphurous- gases during reduction reaction is also explained. The mechanism of carbothermic reduction of nickel sulphide is explained by examining the sulphur exchange and reduction reactions. The phase equilibrium relationships that determine the formation of multicomponent liquid are characterised. Also the governing equilibria for inert atmosphere calcination- roasting of nickel and cobalt sulphide minerals are also described for the metallization of nickel and cobalt.

Jan 1, 1993

By E. Gutierrez-Miravete

A computational method for the simulation of mold filling processes is described. The method is based on the representation of the flowing or deforming medium as a collection of mutually interacting parcels of material. Instantaneous positions of individual material parcels are calculated by numerical integration of the dynamic equations, subject to appropriate initial and boundary conditions. So far, the method has been used to produce qualitative simulations of some flowing and deforming systems encountered in mold filling technology, and our findings are summarized herein. In all cases, individual material particle motions can be followed in detail, allowing critical examination of potentially problematic mold design features.

Jan 1, 1992

By Roma T. Dec

Many industrial wastes may require preliminary processing to change their particle size, density, surface properties or flowability to become more suitable for treatment and recycle. This can be achieved by pressure agglomeration using roll presses. In the following paper an overview of various roll press processing methods like briquetting, compacting, compacting-granulating or densification is presented together with basics of process and equipment design. The emphasis is focused on major factors influencing compaction process and responsible for pressure build up and final product quality. Finally, two examples of roll press application for briquetting of steel plant wastes and compaction of alumina base catalyst tailings are introduced.

Jan 1, 1996

By Karel Verscheure

Reliable furnace cooling technology is a domain of increasing concern to the pyrometallurgical industry as it can significantly increase process intensities, productivity and campaign times of furnaces. Although there are many advantages in using cooling systems, they also impose a variety of problems mainly related to safety, heat losses and sustainability of the operations. The choice of cooling system is hence a matter of trade-offs and differs for every metallurgical application. This paper gives a review of different cooling designs used in the ferrous, non-ferrous and alloying industries. Additionally, the paper systematically reviews aspects of materials selection, manufacturing, installation, water quality and furnace monitoring when using water cooled refractories.

Jan 1, 2006

By Levent Özmen

Colemanite is a mineral containing varying amount of boron that is found in abundance in Turkey. It has a good possibility to be used as a flux in iron and steel industry. In this study a review of the use of colemanite, as a flux agent in steel production has been carried out and various related aspects such as its influence in metal-slag reactions, solubility of lime and magnesia in the slag are discussed along its performance in several points of views including its technical and environmental usage characteristics. Positive and negative factors of using this material as a flux are also underlined.

Jan 1, 2006

By B. S. Boyanov

The hydrometallurgical technology for zinc production in Bulgaria is characterized by the use of considerable quantities of imported zinc concentrates and several kinds of Bulgarian ones which are quite different in chemical, phase and granulometric compositions. In this connection, 7 sulfide zinc concentrates (Bulgarian and imported ones) were investigated by chemical analysis, DTA, TGA, X-ray diffraction analysis, sieve analysis. The accomplishment of optimal mixing of concentrates and providing stabile mix composition for a long period of time of roasting in fluid bed furnace is a task of primary importance in the technological process control in zinc hydrometallurgy. This can be achieved using mathematical optimization methods.

Jan 1, 2006

By Kang-In Rhee

Nonferrous metal recycling not only provides energy saving and environmental benefits but also is a significant factor in the supply of various types of metals used in our society. Recycling plays an important role in establishing the sustainability of materials. The total amount of recycled nonferrous metals by weight accounts for less than 5% but their value is larger than 50% compared to ferrous metal recycling which consists of about half of the total metal recycling in weight. This paper describes trends and typical achievements in nonferrous metal recycling and overviews the present and future of nonferrous metal recycling technology and business in Korea.

Jan 1, 2006

By Milind Deo, Neale R. Neelameggham

The mixture of carbon dioxide and water vapor - called Soda [as in carbonated water] can be converted to easily stored transportation fuels. Earlier papers on Soda- fuel metallurgy noted that this conversion is endothermic requiring energy. Reduced state metallic elements - preferably the alkali, alkaline earth elements, or aluminum can act as oxygen carriers. Availability of such a combination in commonly land fille waste materials is shown. Plant based wastes which are normally composted form a better-controlled reagent. The energy required for the reaction can come from solar energy. This paper describes possible reactor designs, which can accommodate this conversion effectively using carbon dioxide recovered from flue gases.

Jan 1, 2008

By Shadia J. Ikhmayies

"Cadmium sulfide (CdS) in the form of thin films is an interesting material because it has a large variety of applications ranging from photovoltaic to luminescent devices. N-type CdS is usually used as a window layer in the heterojunction CdS/CdTe thin film solar cells. A review of the photoluminescence (PL) spectra ofn-type CdS thin films prepared by different techniques was performed. The effects of different dopants and impurities and the effects of temperature and deposition parameters on the PL spectra were discussed. Annealing in different atmospheres causes the changes in material structure and phase change from cubic to hexagonal phase which can be detected through the variations in the PL spectra. CdCh heat treatment improves the cystallinity of the films and enhances the exciton peaks and the green band in the PL spectra.IntroductionThin CdS films deserve attention because their expected gap emission lies very close to the highest sensitivity of the human eye. Thus, one might assume that thin CdS films are an appealing host for photonic devices [ l]. They have been used in a lot of applications including electronic and optoelectronic devices [2]. Thin films ofn-type CdS are widely used as a window layer in heterojunction solar cells such as CdS/CdTe solar cells. Doped and undoped CdS thin films can be obtained by different techniques such as; spray pyrolysis (SP) [3], chemical bath deposition (CBD) [2, 4], pulsed laser deposition [5, 6, 7], laser ablation [l], thermal evaporation [8].Several experimental techniques have been used in order to study semiconductor defects. In particular, photoluminescence (PL) has been shown as a powerful and sensitive tool in examining the crystal quality of polycrystalline thin films. PL can be used in the detection of defects which are radiative active. These defects can also act as traps in the transport of carriers [9]. The photoluminescence (PL) of thin film CdS is strongly influenced by the unbalanced stoichiometry, which is typical for CdS and is in general evoked by a Cd surplus. With increasing Cd content, the emission spectra move far below the gap to the red spectral range. Besides stoichiometry problems, independent of the material deposited, the PL properties of thin films depend on surface features and the influence of the interface between the film material and the substrate [10]."

Jan 1, 2013

By Shadia J. Ikhmayies

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

Jan 1, 2013

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

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

Jan 1, 2013