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By Aïda Espinola

This work is part of a research program concerning the study of heavy metal removal and selective recovery from electroplating waste waters in the Guanabara Bay ecosystem, preventing the potential noxious retarded effect of landfill, specially in a country of heavy rainfall. A flow-throw cell was employed to adapt to the limits established by the local legislation for disposal in rivers and seas. The cell design is presented and preliminary results show that this cell may be applicable for the decontamination from copper.

Jan 1, 1994

By Klaus Bauckhage

Phase-Doppler-anemometry (PDA)-measurements have to be taken from representative measuring positions from inside the spray cone, helping - with the support of simulated data of improved process models - to describe the multiphase flow situations within the spray cone - and accordingly to that - the heat transfer conditions for the rapid cooling and (partly) solidifying melt droplets before their impact onto the substratddeposit. Simulations and PDA-measurements thus give the base to confirm the hypothesis of the existence of a semisolid mixed-layer and it's influence on the resulting material structure during compaction. The dispersed particles in the spray cone exhibit a cooling and solidification process within a split of a second, which leads - as far as the particles solidify - to a dendritic structure with very short dendritic arm spacings. This causes within the particles extremely short distances for the following equalizing diffision processes taking place on a high temperature level (between liquidus and solidus) in the semisolid mixed-layer of the deposit and explaining the short residence times within this zone of only seconds up to a few minutes. This and the fact that the globular structure of the mushy zone (in the semisolid mixed-layer) leads to an unidirectional crystallization process over very short distances also explains the chemical and morphological ,homogeneity of the sprayed material. The dynamics of these process steps, the very special buffer function of the mixing layer during parameter variations as well as the controlled cooling process of the preform in order to avoid hot cracks influence the quality of the material. Due to the necessity of measuring and controlling the particle bound mass-, momentum- and enthalpy- fluxes to the deposit the PDA-technique has been adapted and modified in order to receive in-line and (in the future) also on-line data from the dynamics of the multiphase flow conditions within the spray chamber.

Jan 1, 1999

By Brian G. Thomas

Quality problems in continuous casting of steel can be identified as they occur by monitoring mold signals (level sensor, thermocouples in the mold walls, friction etc.) and taking appropriate action (such as slowing casting speed, changing taper, changing a clogged nozzle, or later visual inspection of the surface for possible downgrading. Surface depressions and groups of deep oscillation marks form at meniscus and reduce local heat transfer as they move down the mold at the casting speed. This slows shell growth, increases shell surface temperature, and causes characteristic dips in mold thermocouple signals. More importantly, they are also associated with longitudinal cracks. Characteristic thermocouple signatures have been identified for many defects, including sticker breakouts, transverse depressions and deep oscillation marks, narrow-face bleeds, transverse comer cracks, longitudinal cracks, mold level fluctuation defects, and other problems. With the help of computational models, these mold signals should be used to troubleshoot defects, and to take appropriate corrective action. Keywords: Continuous casting, defect detection, thermocouple signals, on-line control

Jan 1, 2003

By Huang Kai

Uniform needle-like and spherical nickel oxalate particles were prepared by the chelating precipitation process, which was based on the reaction of oxalate acid and the solution of ammonia nickel chloride. The molar ratio of ammonia to nickel ion in the mixed solution is essential to determine whether the spherical or needle-like particles are formed, which means actually the concentration of ammonia is the key to determine the growth mechanism. When oxalate acid is added in the form of solid, it may act as the nucleation interface for the eariy-precipitated substance and so induce the formation of spherical particles. The PVP agent can improve the dispersing degree of the needle-like particles and higher reacting temperature leads to larger particles. The composition of the needle-like particle consists of ammonium and nickel oxalate instead of the pure nickel oxalate.

Jan 1, 2003

By Gaifeng Xue, Xiaohong Xu, Meng Liu, Yijie Song, Guotao Xu, Jixiong Liu

BN (Boron Nitride) based composites were prepared with hot-pressing by using h-BN as main material in ceramic preparation process. The relative density, bending strength, vickers’ hardness, thermal shock resistance, thermal expansion coefficient, thermal conductivity, phase composition and microstructure were tested and analyzed by using modern testing technology. The results indicate that the best formula is B, the relative density is 97%, the bending strength is 260 MPa, the hardness is HV5 343kg/mm2, the thermal expansion coefficient is 2.8×10-6℃-1, the thermal conductivity is 22 W/(m.K) and have no crack after thermal shock for 20 times by water cool. XRD analysis indicates that the main phase compositions are h-BN, β-Si3N4 and sialon. SEM studies show that the grains wrapped up by solid solution.

Jan 1, 2015

By Z. Zhang, Cuihuan Huang, Zongshu Zou, Nan Wang, Xueqian Xin

"Vitrification is considered as an attractive procedure for municipal solid waste incineration ash, which can realize the volume reduction and innocent treatment of incineration ash, as well as reuse of bottom ash. The main oxide components of molten ash slag are CaO, Al2O3, SiO2, Fe2O3, MgO, and Na2O, accounting for more than 90% of the total mass. The phase relations and thermodynamic properties of the CaO-Al2O3-SiO2-FeOx-MgO-Na2O oxide system is highly required, and is of great scientific significance for optimization of vitrification processing and sustainable resource utilization of melting slag. A study on the equilibria phase relations of CaO-SiO2-MgO-FeOx system was done by using CALPHAD method based on FactSage in this paper. The modeling parameters for the thermodynamic properties of liquid phase in CaO-SiO2-MgO-FeOx system were established and the equilibrium phase relations of MgO-SiO2-FeOx and CaO-SiO2-FeOx-MgO systems were calculated for different temperatures and oxygen partial pressures.IntroductionThe main oxide components of vitrified bottom ash slag are CaO, Al2O3, SiO2, Fe2O3, MgO, and Na2O, accounting for more than 90% of the bottom ash by weight [1]. During slag processing and modification, the knowledge of thermodynamic properties and liquidus temperature in the related slag system is highly required [2-5], which is not yet available. Through literature survey [6-9], it is clear that the systematic information on the concerned complex slag system is scarce. Most binary subsystems except FeOx-Na2O have been investigated well. Among ternary subsystems, few phase relations of the Na2O-MgO-SiO2 ternary system are available. For the phase relations of the system Na2O-MgO-Al2O3, all the studies are focused on the Al2O3-rich region. Investigation on the CaO-Al2O3-FeOx system is limited to Fe2O3-containing system with relatively higher oxygen potential. Most quaternary systems are not studied well except the CaO-MgO-Al2O3-SiO2 system, mainly due to their metallurgical importance. Figure 1 demonstrates the research status of the vitrified bottom ash slag with almost zero effort [10]. The effort here is defined based on the published literature by considering the number of publications, the investigated composition ranges, and the research details. So far the engineers in the field have to make assumptions of the thermodynamic properties of the simplified oxide system, without taking into consideration the interactions of the different oxide components, which hinders the development of the slag valorization and utilization. In order to provide thermodynamic properties for the application of the vitrified bottom ash, the six-component oxide system (CaO-MgO-Al2O3-SiO2-FeOx-Na2O) will be investigated through both experimental approach and computer modeling."

Jan 1, 2011

By D. P. Cook, M. I. Bloch, J. A. Dantzig

"In this article, we describe a combined experimental and computational program to study the filling of automotive wheels during low pressure die casting. Experiments are performed by placing thermocouples into the mold walls of a production caster for the Ford F 113 wheel to measure the temperature profiles in the die during processing, and to infer the filling pattern. Computational models are also developed using a 36° section of the wheel pattern, taken directly from CAD data files. We use these models to simulate the filling and heat transfer processes. Comparison between experimental and computational results are presented, demonstrating the viability of this procedure.IntroductionAutomotive companies are using increasing amounts of aluminum in production vehicles: While the main driving force is improved fuel economy through weight reduction, replacing steel wheels by aluminum also offers the potential for improved vehicle performance by reducing unsprung mass. For these reasons, many new vehicles are now supplied with cast aluminum alloy wheels, and the aftermarket for these wheels continues to grow.The most common production process for these wheels is low pressure die casting. The process is subject to numerous defects, including microporosity, cold shuts, cold folds, misruns and inclusions. Scrap rates at the caster of the order of 10% are not uncommon. Many wheels also have large production runs, into the hundreds of thousands of wheels per year. Thus, the cost savings from even small reductions in scrap rate have the potential to be quite significant.Most of the defects are associated with the filling and solidification processes in the mold. The molds are air cooled, and the placement and sizing of cooling passages is currently as much art as science. The ultimate goal of this project is to improve that situation, by implementing simulation procedures that enable engineering design methods to be used in die and process specification."

Jan 1, 2000

By Thenepalli Thriveni, Ch. Ramakrishna, Yujin Jegal, Ji Whan Ahn, Jyothi Rajesh Kumar

In alumina production or alumina refining, bauxite is converted to alumina (aluminium oxide) The rare-earth elements (REEs) are a group of 17 chemically similar metallic elements (15 lanthanides, including scandium and yttrium). Rare earth elements play a key role in many industrial applications, petroleum refining, clean energy, automobile, electronics, and defense applications. These rare earths are essential to the success of green technologies. China today controls more than 95 percent of the rare-earth supplies and nearly all rare-earth refining and after 2009 year rare earths crisis raises due to China’s export restrictions and growing internal demand for rare earth elements. The extraction of gallium and yttrium from Korean red mud (KC red mud) by selective acid leaching was explored. The recovery of gallium and yttrium from a leach solution of the Korean red mud using solvent extraction was studied. A number of extractants were investigated for the extraction of those mentioned two rare earth elements and also we proposed a flow sheet of rare earth elements respectively. The toxic heavy metals presented in KC red mud were removed by CO2 stabilization.

Jan 1, 2015

By Muhammad Abid, Kh. .. S. Karimov

"In this study, design and investigation of biogas digester consisting of methane tank with built-in solar collector to utilize solar energy for the heating of the slurry prepared from the dung and heat exchanger is designed, developed and tested. The digester was laboratory type and consists of cylindrical metallic tank of size of 0.5 m in diameter; 1 m in height and 200 liters in volume. The surface of the digester from outside was covered by thermo insulated material a glass wool, except of south side (in northern hemisphere). This side played the role of built-in collector and was blackened to increase absorption of solar irradiation and covered under 45o by glass. In the blackened side of the digester on the different heights it was installed metallic pipes for the inlet and outlet of the air, connected with heat exchanger installed inside of the digester. The heat exchanger was fixed in the level above of the inlet pipe. The horizontal plane reflector concentrates solar beams to blackened side of the digester. In the winter period, it was found that the retention time of this digester is shorter on 15% and produced biogas volume is larger on 20% with respect of ordinary biogas digester. This digester is used for the demonstrative purposes and as a teaching aid presently and base on the results it may be used for the construction of large volume digesters for use in the farms, especially located in the remote and mountain areas where the climate in the winter period is cold. Introduction At present many experts around the world have focused their efforts to energy crises because energy is one of the most important factors for the development of the society. It is known that consuming energy is proportional to quality or standard of life. There is a close relationship between energy consumption and the Gross National Product (GNP). It is obvious that for further development of the country additional sources of energy is required, which are cheap, safe and environmentally compatible with respect to the action on possible wastes. Utilization of renewable energy is one route to help in solving the above mentioned problems. In particular, biogas as a source of renewable energy is produced by biotechnology and used wide on residential scale [1]. The biogas was produced for the very first time in 1814 by Deivy from organic wastes. In 1900 production of biogas was started in Bombay (India) [2, 3]. Biogas consists of 55-70% methane (CH4) and around of 27-44% carbon dioxide (CO2) and less than 1% H2 and H2S. At present biogas is used widely in some countries for lighting, machines, and vehicles, generators, cooking and heating. Biogas generation is suitable for small to large scale operation and at present is realized in a number of developed and developing countries as USA, Hungary, China, India etc. Since 1990s biogas projects construction in China has developed steadily by the end of 1998, there were altogether 6.88 million household biogas digesters [4]. In Russia biogas digesters are used for processing of hard dung into biogas [5]. Over the last few years the very first biogas digesters were constructed in Tajikistan as well [6,7] and it was found that the digesters can work with sufficiently high efficiency in mountain areas as well ."

Jan 1, 2008

By Zhongliang Tian, Yun Cheng, Yexiang Liu, Ming Jia, Yanqing Lai

"A fundamental electrochemical study of Si ions in Na3AlF6-LiF melts and electrolysis using liquid cathodes was conducted. Cyclic voltammograms (CVs) clearly showed the depolarization of silicon deposition on liquid cathode by forming chemical complexes with the liquid solvent metals. Besides, co-deposition of Al and Si is possible when Si ions are insufficient in the molten salt. Based on the electrochemical results, silicon diffusion into liquid cathode is modelled and evolution of Si activity with concentration is deduced by a mathematic approach. Electrochemical study using liquid metals as working electrodes, can be used as an alternative approach for the acquisition of basic data on alloy behavior. Galvanostatic electrolysis showed that liquid cathodes are appropriate to collect the deposited solid silicon and the highest collection efficiency is almost 85%.IntroductionRecent years have witnessed an increasing demand for solar-grade silicon (Si) by the photovoltaic industry [1-4]. The preparation of high-purity metals through electrolysis and electrorefining offer many advantages such as low cost, low-energy consumption, and environment-friendly process, and thus has been widely used worldwide. From the perspective of electrochemistry [5-7], by utilizing the electronegativity difference between the impurities and Si and controlling the relevant process parameters, it is possible in principle to electrodeposit monatomic Si from a Si4+-containing compound melt. Moreover, because the carbon content of the high-purity Si obtained through electrolysis can be effectively controlled and used as a very ideal raw material in the preparation of electronic-grade and solar-grade Si, the preparation of high-purity Si through electrolysis has received widespread attention [8,9]. Monnier et al. [9] used a graphite electrode to obtain high-purity Si (99.9 %-99.99 %) from Si02/Na3AlF6 system through electrolysis; however, because the Si was precipitated in a solid form and showed poor conductivity, the deposition rate was too slow. Olsen et al. [10] obtained high-purity Si films via electrodeposition in K2SiF6/KF-LiF system by selecting electrode materials with high surface quality (such as Ag and graphite). However, in order to ensure the film quality, the deposition current density must be relatively low (10-50 mA/cm2), resulting in a low current efficiency and low deposition rate, which are not conducive to reducing energy consumption and applying to practical use"

Jan 1, 2014

By Karl-Heinz Daum

Outokumpu Lurgi Metallurgie GmbH, Oberursel, Germany ? give saleable by-products, ? not interfere with smelter performance, ? treat all gas streams simultaneously, and ? comply with environmental regulations. The latest developments in sulphuric acid plant design are presented.

Jan 1, 2002

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

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

Jan 1, 2012

By Florian Kongoli

While calcium ferrite slags have been successfully used in continuous copper converting for the last 30 years, ferrous calcium silicate slag was proposed about 8 years ago as an additional alternative for copper smelting. Although both slags are normal extensions of each other their phase relations have not been completely clarified. In this paper the liquidus relations of both slags have been quantified at various areas that cover both of them. The existing experimental data have been first reviewed and discussed in relation to the solidification procedure. An original physical model is then used to predict various diagrams of the liquidus surface of both slags. It is shown that the ternary liquidus diagrams normally used for FeOx-SiO2-CaO system are not suitable for industrial slags. The new model diagrams of Fe/CaO versus SiO2 and Fe/SiO2 versus CaO as well as Fe/CaO versus Temperature and Fe/SiO2 versus temperature are proven to be much more convenient for ferrite and ferrous calcium silicate slags. Based on these diagrams the effect of SiO2 and CaO on the melting temperature is quantified. The effect of Cu2O is also quantified through the model. Some Fe/CaO versus Cu2O and Fe/SiO2versus CaO at various copper contents are predicted and the results show good agreement with the experimental data. It is also shown that in the presence of liquid copper, Cu2O is dissolved in the slag depending on the oxidation degree of the system and might lower the liquidus temperature. Some discussions are also presented taking into account plant observations and important conclusions are drawn for copper smelting and converting

Jan 1, 2006

By Yutaka Shiraishi

Two methods were developed to measure the viscosity of the slag from the glassy to the liquid states in an ascending temperature process. The first method employs rotating parallel plates within which is placed a solid cylindrical sample in line with a sphere. The second method uses a tube which is pushed into a sample held in a rotating crucible. Both methods were tested using standard glasses, including boron trioxide and NBS standard glass #711. The main difference between these two methods is in sample preparation. Comparative measurements between two methods were performed using a sodium boro-disilicate glass containing 5%mol of alumina. The results showed good agreement in the mid-range of glassy viscosities, 105 to to7 Pa.s. In the liquid state, there were no significant differences between the two methods.

Jan 1, 2003

By S. G. Kumar, R. G. Reddy

"Niobium aluminides offer the advantage of higher high temperature capability compared to other intermetallic aluminides due to the refractory nature of niobium. However, the reaction sequence in Nb-Al system is sluggish and currently there is a great interest in the processing aspects of these materials. In the present study, a systematic investigation was undertaken to compare the effect of different powder metallurgy processing routes on the phase relations and microstructure of 66Nb-22AH2Ti (in atom percent) alloy. The three different process routes adopted were: (i) cold pressing followed by reaction sintering; (ii) cold pressing and hot pressing followed by sintering; and (iii) arc melting, hydride-dehydride process to make the alloy powder followed by cold pressing and then sintering. The samples are analyzed by XRD, Optical Microscopy, SEM-EDS and EPMA. The analysis showed that alloy pellets made from pre-alloyed powders i.e., arc melting followed by hydride-dehydride process, gave good densification and more Nb3Al formation.1. IntroductionTo improve the performance standards of turbine engines, materials scientists are challenged to develop materials that have· high thrust-to-weight ratio with high specific strength, high specific modulus and good environmental properties at elevated temperatures. The conventional high temperature materials like nickel based superalloys are high in density and hence many of the high temperature materials scientists have focussed their attention on intermetallic aluminides like Fe-AI, Nb-AI, Ni-AI and Ti-AI in recent years. The phase relations and properties of alloys based on Fe-AI, Ni-AI and Ti-AI are fairly well known whereas little is known about the alloys based on niobium aluminides."

Jan 1, 1996

By Hyun Soo Kim, Joon Soo Kim, Myong Jun Kim, Jyothi Rajesh Kumar, Jin-Young Lee

Rare earth materials have an ever growing variety of applications in the modern and hitech technology. They apply to many an industry with crucial materials and they provide numerous a customers with benefits. Rare earth materials utilization increasing day-by-day in the worldwide, at the same time the resources is very limited in many countries like Korea. The present general article divided four sorts such as 1) mineral processing of Korean ore deals the gravity, magnetic separation and froth flotation, 2) decomposition and leaching of concentrates included sodium hydroxide fritting, sodium hydroxide hot digestion, hydrochloric acid leaching, 3) separation and purification of rare earth elements in mixed rare earth chloride solution consists reduction and oxidation method, solvent extraction, 4) preparation of rare earth oxide compound from purified elemental rare earth chloride solution having oxalate salt precipitation by reaction crystallization. The last part consists of a summary of the present study.

Jan 1, 2015

By Takeshita. Takuo

"In this work, the progress of the HDDR process is discussed mainly on the Nd-Fe-B magnet system. There are three technologies being used for the Nd-Fe-B permanent magnet production; the sintering technique, the rapid quenching annealing and the HDDR process. The HDDR process utilizes· the HDDR phenomenon, in which hydrogen absorbing intermetallic compounds go through as they are heated in hydrogen atmosphere, Hydrogenation - Decomposition Desorption - Recombination. In the HDDR process, these four steps in the HDDR phenomenon are processed by choosing suitable reaction conditions regarding to hydrogen gas pressure, temperature, rate ·of desorption and etc., and we can produce permanent magnet powders of good magnetic properties with microstructures consisting with sub-micron size crystalline grains. In the anisotropic magnet powders, the sub-micron size crystals are being mostly aligned in the crystallographic c-axis direction. Possible applications of the HDDR process to other systems are also discussed.Microstructures of the Nd-Fe-B Permanent MagnetsIt is well known that magnet properties of magnetic materials are very sensitive to their microstructures [l]. This is seen in almost all magnet materials from soft magnetic materials and hard magnetic materials to magnetic memory materials. In this regard, the production technology is very important for the control of microstructures of permanent magnets The Nd-Fe-B magnet is the most powerful permanent magnet as a practical permanent magnet, and its coercivity force is much dependant on the microstructure as is the case for other permanent magnets."

Jan 1, 2000

By Yue Tian, Shengqian Wang, Lifeng Zhang

This paper is to discuss the removal of non-metallic inclusions from molten steel using a high frequency magnetic field. In experiments, a certain amount of aluminum was added to the molten steel in a crucible to generate aluminum inclusions. A layer of aluminum clusters were observed close to the wall of the crucible after the electromagnetic (EM) field was imposed. Three dimensional EM field and fluid flow simulation were performed and showed that over 91% inclusions transported to the skin depth (2.31 mm) of the molten steel. The calculation of inclusion removal agreed well with the experimental observation. The separation mechanisms of inclusions from the molten steel by the high frequency EM field were discussed.

Jan 1, 2014

By J. T. Stanley

The identification of crystal phases and crystal chemistry can be critical to understanding the mechanisms of waste material interaction with native soils. Understanding these mechanisms can suggest correct methods for remediation and treatment. A program is outlined and examples are given of the development of effective techniques for rapid phase identification of environmental samples using electron microscopy. The program concentrates on the development of integrated object oriented software to aid rapid searching of online databases and rapid simulation of potential crystal diffraction patterns. Examples come from dried sludge taken from a former hard-chrome plating facility.

Jan 1, 1993

By Michael G. King

The primary non-ferrous metals industry is the principal supplier of the minor metals selenium, tellurium and bismuth. It is also a major supplier of antimony. These minor elements are recovered from by-products of base metals production. To ensure that these elements remain available, the cost of production must be compatible with four other factors - method of production, available supply, technological niches, and product stewardship. This paper first describes the relationship between the copper industry and the production of tellurium and selenium. The more complex relationship between the lead industry and bismuth production is then discussed, followed by comments on antimony availability. Product stewardship programs are essential to the growth or certain specialized markets for these metals. Smelters and refineries of non- ferrous metals will play a major role in the recycling of scraps and wastes from these markets. Examples on how such materials can be recycled are given in the paper.

Jan 1, 1995