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By Yuri Gelfgat

"This paper presents some results of the investigation of the steady magnetic field influence on hydrodynamics and heat/mass transfer in processes of semiconductor single crystal growth (Si, Ge, InSn). The investigation employed mathematical and physical simulation techniques of relevant processes and full-scale experiments on growth facilities. A number of additional MHD phenomena have been found generated in the melt due to the rearrangement of flow pattern, the formation of specific convective cells, and the origin of MHD boundary and shift layer.IntroductionMagnetohydrodynamic (MHD) means of creating forces by contact-free methods in liquid conducting media have been widely used in the production of volume semiconducting single crystals. The goal of this method is to control convective transfer processes in the melt volume and on the crystallization front [1-3]. This is due to the sufficiently high conductivity of semiconductor melts (s = 104 /106 O1m-1 ) and an obvious relationship between the hydrodynamics in the melt and at interfaces and the conditions of formation of single crystals and their quality [ 1].All types of MHD effects rest upon the generation of volume electromagnetic forces in the melt by various means as well as on the possibility to direct them arbitrary in space and to adjust easily their absolute values. Fig. l presents different means how to implement MHD phenomena during single crystal growth. It should be emphasized that in all the modifications given in Fig. l additional energy introduced into the melt cannot influence directly the crystallization process since it is incomparable to the energy of molecular forces. Both the influence and efficiency of MHD means are determined solely by the change of motion, heat and mass transfer characteristics."

Jan 1, 1998

By Taner Kavas

In the present study the utilization of coal ashes that appear at the end of firing process of brick production in cement pastes was examined. Ashes with three different particle sizes of 75 µm, 106 µm and 150 µm were used to replace ordinary Portland cement (PC) as 5 % and 15 % by weight. Seven samples were prepared and physical, mechanical, chemical and microstructural analyses were carried out. The compressive and bending strength values of samples were determined at the ages of 2, 7 and 28 days. It was found that cementitious pastes with finer particle sizes possessed the highest compressive and bending strength values at all curing ages. Both values after 2 and 7 days cure increased with an increase in ash content, no matter what the particle sizes of ashes were. However, strength decreased after 28 days cure as a result of ash addition of 15 %, although it was still above that of the PC.

Jan 1, 2006

By Hideyuki Itou

Municipal wastes are mainly incinerated in Japan. Both bottom ash and fly ash from the incineration treatment are smelted recently to decrease the volume. Direct smelting of municipal wastes is also becoming popular. The smelting treatment generates fly ash which contains concentrated heavy metals such as Zn, Pb and Cu, and the harmfulness is causing concern. The smelter fly ash is mainly landfilled after stabilization. An effective treatment process of the smelter fly ash is required to recover the metals. For the treatment process, an application of chloridizing volatilization technique is considered. Chloridizing volatilization experiments were carried out to determine the effects of various factors on the volatilization behaviors in this study. A pretreated ash was mixed with a main raw material which mainly consists of hematite. Calcium chloride water solution was added into the mixture. The mixture was pelletized, dried and used as samples for the volatilization experiments. The sample was placed in the reaction tube heated in an electric resistance furnace. 5%02-95%N2 gas with controlled humidity was introduced into the reaction tube. Effects of humidity in the carrier gas, addition of calcium chloride and mixed ratio of the ash to the main raw material were investigated on the volatilization of Zn, Cu and Pb. To determine the volatilization behavior, samples were taken from the furnace at specified temperatures on the heating stage. In addition, experiments at specified holding temperatures for 15 minutes with shortened heating time were conducted. The two series of experiments revealed the effect of heating temperature on the volatilization behavior of Zn, Cu, Pb and Cl.

Jan 1, 2006

By KAGAN BENZESIK, Onuralp Yücel, Mehmet Bugdaycı, Ahmet Turan

ZrB2 and B4C are one of the most significant advanced ceramics. They are being used in various industrial areas from space technology to nuclear industry owing to their physical properties such as high melting point, high thermal/electrical conductivity and low density. Present study was conducted in two main stages: Self-propagating high-temperature synthesis (SHS) reactions and leaching. ZrO2, Carbon black, B2O3 were used as starting material to produce ZrB2-B4C powders by SHS. Also Mg powder was used as the reductant. The reaction mixtures (approximately 100 g) were mixed thoroughly 15 minutes in a turbula mixer and charged into Cu crucible and compacted. W (tungsten) wire was placed at the top of copper crucible and the reaction realized by passing current through the wire. After initiation, a highly exothermic reaction became in a self-sustaining mode and propagated throughout the SHS mixture. The samples were characterized by using AAS and X-Ray Diffraction.

Jan 1, 2016

By R. Tunold, Y. J. Zhang

"The cathodic kinetics of aluminum deposition from aluminum chloridealkali chloride melts was studied by use of electro-cnemical transient techniques at 700 °C. Aluminum deposited as an insoluble product on a glassy carbon electrode and as a partly soluble product on a tungsten electrode. The deposition was found to be a simple diffusion controlled process involving the exchange of three electrons. The diffusion coefficient of aluminum chloride was calculated - 4.sx10-s cm2 ·S-I in AlCl3 -NaCl-LiCl melts and 2.6x10-s cm2 ·S-' in AlCl3 -NaCl-KCl melts. For AlCl3 -NaCl-CsCl system the diffusion coefficient exhibited some uncertainty due to nucleation. The determined rate constant of aluminum deposition reaction was on the order of 10-' -10-2 cm'S:' Constant potential electrolysis was carried out. TiB2 was well wetted by aluminum. The species of melts penetrated into graphite and glassy carbon but not into tungsten. The diffusion coefficient of species in glassy carbon was evaluated.IntroductionAluminum chloride electrolysis is attractive for its power saving of 30%. Different process to circumvent the conventional chlorization to obtain aluminum chloride economically, such as directly chlorizating mixture of Al~03 and C in a cell with A-shaped laminated bipolar electrodes by rising chlorine (1), or by use of a composite anode (2), will promote the electrolysis technology to be realized industrially. With the appearance of the Alcoa process periodically there are studies on the kinetics of aluminum deposition. Some discrepancies seem to exist on the mechanism of aluminum deposition. Borne studies (3,4,5) showed that the deposition of aluminum was hindered by diffusion process in the melts. M.Gabco et a1. (6) claimed a preceding dissociation of a complex being the rate controlled step. This paper presents our results on the mechanism of aluminum deposition from the study by use of transient techniques and some results from constant potential electrolysis."

Jan 1, 1988

By Sungdon Kim, Chuljoo Kim, Joonsoo Kim, Hosung Yoon

"This study was performed to establish the optimum leaching condition through the experiments for the oxidized roasting followed by leaching of fluorocarbonate rare earth mineral (bastnasite) using sulfuric acid, and to establish the optimum condition for the recovery of cerium by ion- sieve method from the leached solution of bastnasite. The optimum conditions for the sulfuric acid leaching by the oxidizing roasting of bastnasite concentrates are that the roasting temperature is 550 -600 °C, the roasting time is 2 hrs, the concentration of sulfuric acid is 6N, the leaching temperature is S0°C and the leaching time is 3 hrs. At this time, the leaching yield of total rare earth oxides in the leaching of bastnasite concentrates is about 91%. When cerium is recovered by ion-sieve method from the solution obtained by the sulfuric acid leaching of the roasted bastnasite, the optimum conditions are that the TREO(total rare earth oxide) of leached solution is below 70 g/l, the flow rate of leached solution is 9.6 ml/min and the ratio of height to diameter of resin packed in column is above 9. In these conditions, the recovery of cerium of yield 85% and purity 96% is possible.IntroductionThe rare earths are generally called to Lanthanides, which are totally 17 elements including Scandium of atomic number 21 and Yttrium of atomic number 39 in addition to 1 S elements from Lanthanum of atomic number 57 to Lutetium of atomic number 71. Since the separation to each element is very difficult because of their similar chemical properties, the rare earths were used as the mixed rare earths and the mischmetal without separating to each element. However, the high purity rare earths are recently produced commercially to each element so that they are used as the materials for high tech. industry such as electric and electronic materials, catalysts, optical materials, special alloy and 8Uperconductive materials, and their consumption is rapidly increasing. Therefore, the purpose of this study is firstly to prepare leached solution by using the series of process of the oxidation-roasting and leaching by sulfuric acid. Next, second purpose is the separation and recovery of cerium by ion-sieve method."

Jan 1, 1998

By R. G. Reddy

The effect of solid particles on viscosity behavior of Na2O-O-B2O3-SiO2 melts of composition XSio2/XNa2o =0.5 and in the temperature range of 900- 1150 K was studied. Samples were analyzed by X-ray diffraction and optical microscopy. The results showed that a crystalline phase (NaBO2) was formed and its amount increases with decrease in X,, from 0.50 to 0.25. The experimental viscosity values were compared with the predicted values using our viscosity model developed earlier. At low temperatures, for low content of B2O3 , the experimental values exhibits a large deviation from the predicted values. It was concluded that the deviation was due to the formation of solid particles in the molten slags. The existence of these solid particles increased the viscosity values significantly. A new viscosity model was developed to include the effect of solid particles.

Jan 1, 1993

By Qin Li

An highly active absorbent with oxidization based on fly ash, lime and additives was prepared. Experiments of simultaneous desulphurization and denitrification were carried out using fixture bed and duct injection. The influential factors for the absorptive capacity of the absorbent were studied. The absorptive capacities of 120.7mg for SO2 and 43.7 mg for NOx were achieved at a Ca/(S + N) molar ratio 1.2, respectively, corresponding removal efficiencies of 87% and 76%, while spent absorbent appeared in the form of dry powder. The optimal temperature and humidity of flue gas treated with this process were shown to be approximately 50\\176 and 5% respectively. The mechanism of removal for SO2 and NOx was investigated. In comparison with traditional dry FGD, this process appears to have lower cost, less complicated configuration and simpler disposal of used absorbent. The valuable references can be provided for industrial application by this process. The foreground of application will be vast in China and in the world.

Jan 1, 2006

By Monteirom Sergio N., Romulo L. Loiola, Giulio R. Altoe, Noan Simonassi, Frederico M. Margem

"The environmental concern is creating pressure for the substitution of high energy consumption materials for natural and sustainable ones. Compared to synthetic fibers, natural fibers have shown advantages in technical aspects such as flexibility and toughness. So there is a growing worldwide interest in the use of these fibers. Buriti fiber extracted from buriti palm tree (Mauritia flexuosa), presents some significant characteristic, but until now only few studies on buriti fiber were performed. This work aims to make the analysis of the tensile strength of epoxy composites reinforced with buriti fibers. This analysis was performed in fibers with diameters between 0.1 and 0.4 mm. Those fibers were incorporated into the epoxy matrix with volume fraction from 0 to 30%. The fiber diameters were measured by a profile projector. After fracture the specimens were analyzed by a SEM (scanning electron microscope).IntroductionNatural fibers with high amount of cellulose, also known as lignocellulosic fibers, have been used from primeval times of our civilization. In the last century, synthetic fibers such as nylon, carbon, aramid and glass fibers gained interest owing to superior strength and precise dimensional control. Natural fibers were then replaced by synthetics in many fields such as textiles, sports goods and appliances. In the past decades, however, environmental issues drawn, once again, the attention to lignocellulosic fibers as possible substitute for intensive energy-consuming and long term polluting synthetics, specially the glass fiber(1). In particular, research works have disclosed the potential advantages associated with the use of lignocellulosic fibers as the reinforcing phase in polymer composites(2-3). Among the advantages it is worth mentioning the renewability, recyclability, biodegradability and the fact that natural fibers are neutral with respect to CO2 emissions responsible for global warming. In addition to environmental benefits(l,10) the lignocellulosic fibers present economical advantages, such as worldwide abundance and comparatively low costs as well as some technical properties associated with flexibility and toughness( 4), which contribute to the performance of automobile components fabricated with natural fibers composites(l 1-13)."

Jan 1, 2013

New method for processing of copper and nickel production feed has been developed and tested at pilot unit having 10 t/hr capacity. The process allows single-stage treatment of ore feed including that with high magnesium oxide content and resulting in the production of rich matte, high-grade matte, or moralised alloy for further leaching, as well as dump slag and off-gasses suitable for production of elemental sulphur, liquid sulphur dioxide, or sulphuric acid. Tests results and principal technical and economical parameters are presented.

Jan 1, 2006

By Per Anders Eidem, Merete Tangstad, Jens Davidsen

"During excavations of submerged arc furnaces producing silicomanganese, silicon carbide (SiC) has been found. Contributing to the size of the inactive area of the furnace, the active area of the furnace where reactions occur will decrease, thus reducing the potential for pre-reduction in the furnace.This work studied the formation of SiC from the liquid-solid reaction between slag, metal, and metallurgical coke. Slags and metals with different levels of silica (S1O2) and silicon (Si) have been studied. The slag and metal has been heated together with coke, and the samples investigated by microprobe. The results show that SiC was formed on the coke particle through reactions with both slag and metal. For the metal, the carbon most likely diffused through the SiC to react with Si in the alloy. SiC formation with slag is likely to go through the reduction of Si02 to Si.IntroductionToday, Silicomanganese (SiMn) is produced in submerged arc furnaces (SAF) by reduction of S1O2 and manganese oxides, mainly with metallurgical cokes. Typically, the tapped metal has a silicon content of 17 - 20 wt.%. To achieve higher levels of Si, the metal can be refined by adding off-grade silicon metal, yielding low carbon SiMn. [1]. What is believed to be SiC that has been found during dig-outs of SiMn furnaces producing high silicon alloy. It is possible that excess amounts of SiC in the furnace cause operational problems, since SiC will occupy furnace volume. As SiC accumulates, the active volume of the furnace will decrease, increasing the flow of material and gas in the active areas of the furnace. Formation of SiC is inevitable, so it is desired to keep the formation as low as possible. To be able to control the formation of SiC, one has to understand the basic mechanisms."

Jan 1, 2012

By P. D. Navarro

The behavior and operability of LIX 1104SM extraction was studied at laboratory scale on the Solvent Extraction at Sb3+, from high concentration sulfuric acid. In order to evaluate the reactant batch tests were made at laboratory scale as well for extraction as for re-extraction of Sb3+. Experiences achieved were: extraction kinetics, temperature effects, selectivity tests and re-extraction selectivity. A extraction kinetics was found, reaching equilibrium in 2 min, high selectivity of Sb3+ extraction in front of Cue , existing As5+ co-extraction and Fe3+ At the re-extraction stage, equilibrium was reached in 3 min, getting high Sb3+ re-extraction efficiency with HCl concentrations within 6 and 8 M. A high selectivity was achieved on Sb3+ re-extraction in front of As+5, existing Fe+5 re-extraction.

Jan 1, 1999

By Finn Olesen, Melina Garcia, Mark William Kennedy

"Furnace resistance is a function of the complex interrelationship between many factors including: operating practice, slag conductivity, temperature, power intensity, and geometry (electrode shape, diameter, spacing, immersion, slag depth, etc.).Accurate prediction of resistance is critical for success of the overall furnace design. The sizing of electrodes, columns, bus-bars, and transformers are all impacted. Estimation of minimum and maximum resistance or maximum operational current, as well as the maximum operating voltage are of fundamental importance.Various mathematical tools have been developed to assist designers with the selection of furnace dimensions and the prediction of resistance. Elkem found the methods of Downing and Urban 1965 and Westly 1975, to be particularly useful.In the current paper, comparisons are drawn between data from spent aluminum pot lining (SPL) demonstration testing at Elkem Bjolvefossen and predictions based on these classical tools and 3D finite element modeling (FEM) with COMSOL.®"

Jan 1, 2012

By Fumito Tanaka

The Converting Furnace (C-furnace) of the Mitsubishi process has solely provided opportunities for producing blister copper continuously from molten matte. Continuous converting originates from the proven technology for controlling the behavior of magnetite in lime-ferrite slag of the CaO-FeOX-Cu2O system. Recent improvements in the C-furnace operation have included the slag controls reflecting the impact of minor oxides on magnetite behavior. Although previous investigations focused on magnetite behavior, sulfur has also affected the C-furnace operation because it is of practical importance to avoid the precipitation of gypsum from lime-ferrite slag and the separation of matte from blister copper. This paper will quantify the behavior of sulfur in C-furnace with respect to the gypsum formation and matte separation, and discuss better controls for C-furnace operation.

Jan 1, 2006

By Alim Ullah

Process, quality and management control are necessary in order to produce DRI of required quality and at minimum cost. Although the characteristics of the two (2) principal inputs, that is, iron oxide feed and natural gas (for gas-based DRI plants) can affect the operation of a DRI plant significantly, they are outside the control of plant operators, at least in the short run. The quantity of reduction gas, its composition and reduction gas temperature are some of the key process variables. Statistical Process Control (SPC) can be used in a DRI plant to minimize the production of off-grade material and costs, as well as to improve the overall operation of the plant. One of the key quality variables to be measured and controlled is percent metallization, defined as FeM/FeT*100 where, FeM and FeT respectively are metallic iron and total iron in DRI. Control charts are used to monitor the quality of DRI produced and, when necessary, corrective actions are taken to bring the product back within the control limits. Management control can consist of essentially following how well the plant performs against some pre-established standards of parameters like daily production, downtime, consumption of material and energy, etc. In this respect, it is suggested that yield, defined as theoretical consumption/actual consumption of iron oxide feed, be used to monitor the consumption of feed material. Similarly, instead of using natural gas per ton of DRI produced, a better criterion would be efficiency, defined as theoretical natural gas consumption/actual natural gas consumption.

Jan 1, 2006

By Zhong g. Shui-ping

A new type Pb-Ag (0.8wt%)-Bi (0~5.0wt %) alloy used as anode in electrowinning of zinc from sulphuric acid electrolytes was prepared. The electrochemical properties of this ternary lead alloys have been tested and compared with those of Pb-Ag (0.8wt %) anodes used in industry. Results show the anodic overpotential decreases with the increasing of Bi content in the alloys. When the content of Bi was 1.0 wt% and 5.0 wt%, the anodic overpotential is about 40?50 mV and 60?80 mV lower than that of Pb-Ag (0.8wt %) alloy, respectively. The formation of oxide layers on the surface of these alloys was traced by LSV methods and the composition of the anodic oxide layers was characterized by XRD and SEM analysis. The surface layer on the two type anodes examined is mainly composed of a?PbO2 and ß?PbO2. But different structure of the surface layer was observed, Pb-Ag (0.8wt%)-Bi (1.0wt %) has a more fine-grained structure as compared to Pb-Ag (0.8wt %). But the film on Pb-Ag (0.8wt%)-Bi (3.0wt %) alloy is rather friable, cracked and not tightly attached to the anode.

Jan 1, 2008

By Damien Wagner

To reduce the emission of greenhouse gases by the steel industry, particularly for ironmaking, the production of DRI (Direct Reduced Iron) using hydrogen as the reducing gas instead of carbon monoxide is being considered. In this context, the reduction of pure hematite by hydrogen was studied at the laboratory scale, varying the experimental conditions and observing the rate and the course of the reaction. All the reduction experiments were performed in a thermobalance and supplementary characterization methods were used like scanning and transmission electron microscopy, X-ray diffraction, and Mössbauer spectrometry. The influence of rising temperature in the range 550-900°C is to accelerate the reaction; no slowing down was observed, contrary to some literature conclusions. A series of experiments consisted in interrupting the runs before complete conversion, thus enabling the characterization of partially reduced samples. Interpretation confirms the occurrence of three successive and rather separate reduction steps, through magnetite and wustite to iron, and illustrates a clear structural evolution of the samples. Finally, the influence of the sample type was revealed comparing a regular powder, a nanopowder and a sintered sample. The regular powder proved to be the most reactive despite its larger grain size, due to a more porous final structure.

Jan 1, 2006

By V. V. Geikhman

The paper updates the Plant experience in the development and implementation of an advanced environmentally friendly zinc production technology complying with the technological and economic level of producers in the world and the standards of maximum permissible gas emissions stipulated by the Russian legislation. General water recycling engineering allowed to ensure 95.6% water rotation level. All solid wastes formed during treating zinc concentrate are processed into marketable products or semiproducts and sold. As a result of implementing innovation techniques production at the Chelyabinsk Zinc Plant is non-waste.

Jan 1, 2006

By Min Chen, Lei Xu

Sintering behavior and performance of high alumina refractory based on the ternary subsystem MgAl2O4-CaAl4O7-CaAl12O19 were investigated using ZrO2 as an additive up to 8 wt.% by solid state reaction sintering. It was found that the added ZrO2 could dissolve in the CA6 grains in the form of a solid solution, which enhanced the isotropic growth of CA6 grains and then improved the sintering. As a result, the densification process was improved and areas with enrichment of ZrO2 showed a more compact structure. With further increase of ZrO2 addition, tetragonal ZrO2 were found to locate in the grain boundaries for exceeding the solid solubility limit, which enhanced the thermal shock resistance, indicating that addition of ZrO2 exhibited a positive effect on sintering behavior and performance of this refractory. In addition, it is considered that the optimal amount of ZrO2 addition was about 4% considering the performance together with the cost.

Jan 1, 2015

By Clemens Schmetterer, Patrick J. Masset

"The surface tension represents an important property for the modelling of high temperature processes. In this study the surface tension of two Al2O3 – CaO – SiO2 model slags and the influence of the admixture of 5 up to 30 wt.% FeO were studied. The surface tension measurements were carried out using the sessile drop technique on BN substrates under Ar atmosphere (10-6 atm O2) up to 1500 °C.IntroductionThe aim of VIRTUHCON1 is the virtualization of high temperature conversion processes, a task that requires thorough understanding of these processes. In many of these conversion processes slag plays an important role to control the properties of the product, to protect the reactor lining or simply as waste. Slag surface tension is one of the materials properties that is needed for the description of such processes, since it influences the interactions between the components in the reactor, e.g. at the slag – Fe interface in the blast furnace.Surface and interfacial tensions have thus received considerable attention in research, but the number of investigations in this particular pseudo-quaternary system is surprisingly low. Furthermore, the literature data are subject to different measurement conditions and techniques which complicates the data analysis and comparison.The slag atlas [1] offers a compilation of the available literature until 1986 (shown in Table I), but literature search has not revealed more recent studies of this system until now. For example, Elliott and Mounier [2] determined the surface tension of ACSF slags using the double tube maximum bubble pressure technique at 1200 °C. They kept their slags in contact with Cu-S-F mattes, and the slag therefore contained a certain amount of sulphur which acts as a surfactant and lowers the surface tension. The compositions of their slags were scattered over a wide composition range and they did not use a common ACS base mixture for their tests, either. The surface tension values vary between 417 and 446 mN/m, but due to the reasons just mentioned no trend in the measurements can be observed and the influence of FeO admixture on the surface tension cannot be deduced. Further information including the temperature dependence is available from Pavlov et al. [3], Ishchanov and Shushkov [4] and Murav’eva and Kaplun [5]; the diagram on page 446 in Ref. [1] has been drawn from these sources. Both positive and negative temperature coefficients are reported in these works. SiO2 is the only pure constituent that has a positive temperature coefficient [6], but a correlation of the temperature coefficient with the SiO2 content was not found to be conclusive."

Jan 1, 2011