Search Documents

By Animesh Jha, Catherine Davey

"Carbothermic reduction and nitridation reactions using synthetic kaolinite mineral were investigated for the formation of silicon based nitrogen ceramics. The temperature dependence of the reaction rate and its effect on phases formed are reported. The effect of the reactivity of carbon on the kinetics of formation of AIN and ShN4 is discussed. Using the standard Gibbs free energy values for the formation of nitrides and oxides of aluminium and silicon, a log po2 verses I/T diagram is constructed. The experimental data results are discussed and compared with the predicted phase equilibria. We also report the influence of sub-oxide gaseous species on the microstructure of the ceramic phases produced.IntroductionSynthetic kaolinite is a clay containing alumina, silica and water of crystallisation, and has a chemical formula 3(Al2O 3.2SiO2.2H2O). This mineral is relatively inexpensive and, is therefore an ideal candidate for use in the production of ceramic powder mixtures for example silicon nitride and aluminium nitride for composite material formation, When the mineral is heated, the water of crystallisation from the crystal lattice is lost via the 3(Al2O 3.2SiO2.2H2O) = 3(Al2O3.2SiO2) + 6H2O reaction. It has been shown [1·2j that on further heating to 1673K, the anhydrous kaolinite decomposes to a mixture of mulllte and silica, 3(Al2O3.2SiO2) = 3Al2O 3.2SiO2 + 4SiO2 which is consistent with the alumina-silica phase diagram, shown in figure 1.The binary alumina-silica phase diagram has a well-defined sub-eutectic immiscibility dome and this characteristic dernixing behaviour is reflected in the thermal decomposition of anhydrous kaolinite consequently the microstructural features resemble the spinodal decomposition process. It is well established that the spinodal decomposition process raises the nucleation frequency due to their low free energy barrier, (?G). The small magnitude of this barrier consequently promotes the evolution of a very fine microstructure. The process of spinodal decomposition is therefore expected to be influential during the reduction-nitridation of kaolinite minerals."

Jan 1, 1996

By Carlos Antonio da Silva

Steel refining reactors based on chemical heating are being used as an alternative to ladle furnaces, They show a high degree of flexibility in respect to heating rate in addition to carrying out refining reactions such as de-S, inclusion removal, alloying etc. IR-UT and CAS-OB are examples of such reactors. Their performance is dependent upon geometrical characteristics as well as operational conditions which determine the flow field inside the vessel. A physical model of the IR-UT process of the Companhia Siderúrgica de Tubarão, steel plant located in Serra, Espirito Santo, Brazil, was developed to assess the features of the flow field and its influence on the metallurgical behavior. Results of the physical model were used to optimize the process parameters in the industrial unit.

Jan 1, 2003

By S. Z. El-Tawil, K. A. El-Barawy, M. B. Morsi, M. M. Nasr, Z. I. Zaki

"Tue sulphatization of zinc concentrate produced from heated zinc concentrate of Um Ghieg area, eastern desert by ammonium sulphate as sulphatizing agent is carried out at different conditions to achieve the appreciable formation of soluble sulphates. The maximum zinc recovery as soluble sulphate equfils to 95% upon using 1.5 stoichiometry ammonium sulphate at 600 °C for one hour. Tue obtained leached zinc sulphate solution is subjected· to purification process to prepare high pure zinc metal and zmc compounds such as pure zinc sulphate, zinc caibonate and zinc oxide. The products obtained are analyzed chemically and identified by X-ray analysisTue mechanism and kinetics of the sulphatization process of zinc concentrate are considered where the activation energy is calculated and equals to 33.3 K.J.mol""1 A process flowsheet for the overall sulphatization process of zinc concentrate by ammonium sulphate is proposed.IntroductionConsiderable reserves of zinc ores are present in Um Ghieg area eastern desert, Egypt. The possibility of extraction zinc from these ores and preparing its valuable compounds by choosing a more feasible technology become of vital importance. An attention is focused on the sulphatizing roasting processes (1-9) to achieve the appreciable formation of soluble sulphates. Previous publications are reported in our division by El. Tawil and others (10-16) using ammonium sulphate as sulphatizing agent for the successful treatment of nonferrous bearing materials.Therefore, the present work aims to study the different factors affecting the sulphatizing roasting process of local zinc coocentrate by anunonium sulphate to extract completely zinc and preparing its main compounds. Tue mechanism and kinetics of the different chemical reactloos that 1ake place in the process are considered."

Jan 1, 2000

By Carlos Antonio da Silva

Steel refining reactors based on chemical heating are being used as an alternative to ladle furnaces. They show a high degree of flexibility in respect to heating rate in addition to carrying out refining reactions such as de-S, inclusion removal, alloying etc. IR-UT and CAS-DB are examples of such reactors. Their performance is dependent upon geometrical characteristics as well as operational conditions which determine the flow field inside the vessel. A physical model of the IR-UT process of the Companhia Siderurgica de Tubarao, steel plant located in Serra, Espirito Santo, Brazil, was developed to assess the features of the flow field and its influence on the metallurgical behavior. Results of the physical model were used to optimize the process parameters in the industrial unit.

Jan 1, 2003

By L. Katgerman, R. Van Toi, H. E. A. Van den Akker

"Mould filling simulations are powerful tools for optimizing the characteristics of castings. The robustness of calculational methods for mould filling simulations is generally tested in simple geometries. While a vertical plate has been used often for validation studies, this paper aims at mould filling simulations of a horizontal thin wall casting. Such castings exhibit a strong interaction between heat transfer (solidification), surface tension and gravitational force.The results are presented of a study to validate numerical simulations of mould filling phenomena in a thin wall horizontal casting. Solidification during mould filling is studied computationally. Velocities are measured using Particle Image Velocimetry.INTRODUCTIONIn foundry practice Computational Fluid Dynamics (CFD) is being considered a promising tool to arrive at a better understanding of casting defects introduced during the mould filling period of a casting. The use of CFD is believed to be advantageous in predicting possible defect locations, pouring times, and the lowest possible casting temperature without the risk of cold shuts. In addition, CFD may be used to optimize pouring system geometries [1,2]. As opposed to experimental studies in, e.g., cold water models, CFD allows for the flexible modification of the casting geometry and the pouring system, and for the inclusion of physical effects such as solidification and heat transfer. Thus, a proper use of CFD may lead to a reduction of the casting rejection rate without expensive trial-and-error procedures, and to a decrease of production costs in foundries. Mould filling simulations take a special place in CFD, because a free surface tracking algorithm is required. Over the past decade methods, MAC [3] and SOLAVOF [4], have been extended to 3-D. The robustness of computational methods for mould filling simulations is generally tested in simple geometries [5,6]. While a vertical plate has been used often for validation studies, this paper concentrates at mould filling simulations of a horizontal thin wall casting. Thin wall horizontal castings exhibit a strong interaction between heat transfer (solidification), surfaces tension and gravitational force. The gravitational force in this setting is orthogonal to the plane of flow and has therefore no influence on the shape of the free surface in the plane of flow. Mould filling numerical methods and algorithms have been recently reviewed by Chen et al.[7]."

Jan 1, 1999

By Youze Xu

The effect of oxalic acid, acetic acid, citric acid and EDTA on extraction of Cr (?) in soils contaminated by chromium- containing slag was investigated using a batch of incubation experiment. The results show that the pH value decreases more obvious with the increase of the amount of organic acid. The amount of Cr (?) extracted increases with increasing the amount of organic acid. When the ratio of organic acids to total Cr was 5:1, citric acid revealed the highest extraction effectiveness, followed by EDTA, oxalic acid and acetic acid, respectively. The amounts of Cr(?) extracted by citric acid, EDTA, oxalic acid and acetic acid increased by 439%, 244%, 215% and 162%.

Jan 1, 2009

By Ping Long, Bin Yang, Jian Wu, Xiumin Chen, Wenli Zhang

In this study, the analysis method of trace element in pure indium using glow discharge mass spectrometry (GD-MS) has been established by correcting the analysis result, which was obtained from non-standard quantitative method of GD-MS. The effect of instrument operating parameters, the resolution and isotopes and the pre-sputtering time on the determination results were investigated respectively. The optimized operating parameters of the instrument were obtained as follows: the discharge current was 37.5mA and discharge airflow was 475ml/min. Mass spectral interferences have been eliminated using selected resolution and isotope. The pre-sputtering time was 30 min. 4 trace elements in two pure samples were determined for 6 times. The RSD were less than 20%. The content of trace elements in indium samples was determined by GD-MS and Chemical Analysis Method of Indium which is tested by inductively coupled plasma atomic emission spectrometry, respectively. The results were consistent with each other.

Jan 1, 2016

By Milton Manrique

The thermal decomposition of zircon concentrates in a non-transferred arc thermal plasma flow reactor was investigated. The plasma torch was operated using argon-helium and argon-nitrogen mixtures as plasma gases. The effect of power, feed rate and zircon particle size was studied. Products were characterized by XRD, SEM, TEM and chemical analytical techniques. The average size of the product was in the submicron range. Free energy minimization plots were used to predict the behavior of the system under different operating conditions. A kinetic model to describe the different stages of the thermal decomposition process is proposed. The results of this investigation showed a significant segregation process where the zirconia-rich product is collected in the reactor while the silica-rich product is collected in the filter. TEM analysis indicated that silica vapor is condensed on the surface of the zirconia particles.

Jan 1, 1996

By Sharon K. Young

What might an ideal leach-to-cathode/product system look like in the next century? The paper looks at the synergies of the 60's and 70's that led to the highly effective copper leach SX-EW system of the 90's. Standing in the year 2020 focuses on what breakthrough technologies might make possible a next generation leach/extraction/metal recovery system. Many of the pieces of such a technology have been developed, even piloted: in situ leaching, enhanced bioleaching, heap leaching of fine particles, resin in pulp, ion exchange, alternate anode reaction electrowinning, novel anode coatings. With nearly non-existent research on the part of individual large companies, the greatest challenge may not be inventing the technologies but rather inventing an industry "will to create."

Jan 1, 1999

By A. J. Davidson

A novel sensor is described for the measurement of the copper content of copper matte. Due to the high copper concentrations found in matte, potentiometric sensors are not sufficiently sensitive. A highly sensitive sensor has been developed based on a modification of the amperometric technique using a copper ion conductor, Cusicon. The results correlate closely with the theoretical predictions.

Jan 1, 1998

By Z. Sun

Magnetic fields have been used for inclusions removal from melt and preparation of materials with gradient compositions. Fundamental in these applications is that the induced magnetic forces on the particles/melt can enhance migration and change the interaction behavior. In the present paper, migration and interaction behavior of electrical-insulating particles in a conductive melt under strong magnetic field are theoretically analyzed. It is found that the migration can be considerably enhanced for micrometer sized particles by applying a strong magnetic field. In addition, two forces are involved in the interaction between two particles: the interparticle magnetic dipole-dipole attractive force due to magnetization and the repulsive force induced by flow of the melt. This theoretical analysis renders a better understanding of recent experimental results. Additionally, a new method by using strong magnetic field can be proposed to control the particle size distribution for the preparation of metal-matrix composites.

Jan 1, 2009

By Lifeng Zhang

Printed circuited boards contain considerable quantities of valuable metal, while also containing many environmental pollutants making them unsuitable for landfill. In this study the decomposition of common plastics used in printed circuit boards were studied. Polytetrafluoroethylene (PTFE), polyvinyl chloride (PVC) and polyethylene (PE) were heated in both C02 and argon atmospheres using a thermo-gravimetric furnace (TG) coupled to a mass spectrometer (MS). Soda ash Na2C03 and baking soda NaHC03 were used as reactants. The degradation temperatures and evolved gases are presented for single plastics and mixtures. Mixed plastics are shown to behave as a sum of the individual plastics. The mass loss temperature is the same in CO2 and argon. However, less residue is formed when heated in CO2.

Jan 1, 2008

By Z. Smieszek, W. D?browicz, J. Pawlowski, G. Krawiec, J. Czernecki, J. Por?mbski, S. Gizicki

Rapid development of the automotive industry and motorization has been observed in Poland over the last decade. This phenomenon has increased the amount of used car batteries requiring recycling and has thus posed new challenges for their processing. Orzel Bialy" S.A, is the major secondary lead smelter in Poland. Ibis paper describes the program for smelting technology modernisation and productivity increase through the application of oxy-fuel burners, which has been implemented at "Orzel Bialy'' S.A. The main objective of smelter modernisation, which was to increase the furnace productivity by 20%, has been achieved. This paper outlines the previous and present state of the lead acid battery scrap smelting technology at the "Orzel Bialy" S.A. Specifications of the burners and of oxygen installation are given. Industrial tests with the modernised smelting technology and optimisation of the process parameters are described, and the results obtained are discussed.

Jan 1, 2000

By Kampe. S. L., Baker. Andrew H., Tony Zahrah

"Experimental heats of reaction for the formation of several Al3Ti + TiB2 intermetallic composite formulations have been determined utilizing bomb calorimetry. To overcome the kinetic constraints and achieve ignition in these formulations, a boron (B)/potassium nitrate (KNO3) initiation aid was incorporated within the blended reactant compact. The heat contribution from the initiation aid was regressed to provide estimates of the heat of reaction of the nominal formulations. Powder x-ray diffraction was utilized to identify the products of the reaction and discern any differences between the predicted equilibrium products of the formulation and the actual products.IntroductionReaction synthesis is a technique for the creation of ceramics, intermetallics, and in-situ composite materials [1]. Reaction synthesis is defined by its self, propagating mechanism, where the energy liberated from a localized reaction within a green powder compact is enough to carry the bulk reaction to completion. Achieving a self, propagating state can be achieved in variations of two primary methods of initiation: uniform volumetric heating and directional propagation [2].Uniform volumetric heating involves subjecting a green compact of the unreacted formulation to uniform heating in a furnace to encourage diffusion to initiate the reaction (Figure 1a) throughout the bulk material. Directional propagation utilizes a point heat source at one section of a green compact of unreacted formulation (Figure 1b). The localized exothermic reaction at one point in the compact then initiates the reaction in the section of the compact adjacent to it and fully propagates throughout the entire compact until completion. Initiation of the localized reaction is generally associated with the melting of the constituent with the lowest melting point, with instantaneous initiation of the reaction usually occurring close to that melting point [1]. This melting point can be high in some systems of interest, such as the titanium (Ti) and boron (B) system in equation 1:"

Jan 1, 2011

By Eiichi Kuzuno, Atsushi Shibayama, Toyohisa Fujita, Kazuo Koike, Toshio Miyazaki, Hitoshi Masuda

"A solid sulfur is more useful to recover and store than a sulfuric acid as a by-product in the zinc hydrometallurgy. In this experiment a zin concentrate (sphalerite) was leached with ferric sulfate at about 373 K for 3 to 6 hours. Zinc was leached more than 95%. After a solid-liquid separation, the leached residue contained solid sulfur was obtained. The particles in the residue were dispersed by lignin and the solid sulfur of approximately 85% was recovered as float product by a flotation with frother in the pH 4. The dried float product was heated at 413K for 2 hours. The pure solid sulfur was recovered. On the other hand in the leached liquid a zinc oxide was ·added and ferrous .iron was oxidized to ferric iron by blowing oxygen. This ferric iron was returned to the zinc leached process after solid-liquid separation.IntroductionZinc concentrate is usually roasted as pretreatment in zinc hydrometallurgy and the produced S02 is changed to sulfuric acid. However, recently in Japan the utilization of sulfuric acid has been limited and it is more costly to store. Instead of producing sulfutic acid the solid sulfur recovery has been examined by direct leaching of zinc_ concentrate in this experiment.In the direct leaching, several kinds of effects have been studied for leaching of sphalerite in ferric sulfate solution. The addition of lignine siilfonate1 • 2) and fine· grinding3) increases the · speed arid leaching fraction of sphalerite. The leaching ratio depends on impurities in sphalerite ores4 • 5). Here, the zinc concentrate is leached ferric sulfate solution under atmospheric pressure at 373K. The solid sulfur in leached residue is separated as float products from other solids by sink-float separation and flotation. The sulfur in float products is purified by evaporation at 413K and recovered."

Jan 1, 2000

By Lv Guozhi, Niu Liping, Liu Yan, Zhang Zhiqi, He Jicheng, Zhang Ting’an, Dou Zhihe

"CuCr alloy can be extensively used as contact materials in integrated circuit, electrodes, electric contact and high strength conductor. We proposed thermit reduction-electroslag remelting method of preparing the large scale CuCr alloy. But there are pores and oxide inclusions in CuCr alloy prepared by thermit reduction process. This paper studied mainly the effects of ratio of reactant and additive on the inclusion type and their occurrences in CuCr alloy. The slags and CuCr alloy were characterized respectively by XRD and SEM. The results show that when the additive is Na3AlF6, the slag consist of Al2O3 and Cr. When the additive is CaF2, the slag consist of Al2O3, Cr, CaF2 and CaAl4O7. The inclusions in CuCr alloy are mainly Al2O3 and pores which disperse in Cu-rich zone and Cu-Cr phase interface. When 5% CaF2 and 5% KClO3 are added, there are fewer pores and inclusions, and the more better microstructure.1 IntroduceCuCr alloy is the contact terminal material with an eximious properties[1,2], which gradually replaces CuBi alloy becoming the first choice for contact terminal material in the medium and high power vacuum switch after the 1970s. The traditional preparation methods of CuCr alloy mainly contain powder metallurgy, infiltration process and vacuum electric arc melting methods. But the above methods exist some shortcomings, such as poor product quality, high cost of production, processes complex ect[3-9]. CuCr alloy is made by the thermit reduction self-propagating method, which uses CuO, Cr2O3 and Al as raw material to get the high-temperature melt, and then casts to manufacture CuCr alloy ingot, which response equation follows as:"

Jan 1, 2012

By Min Chen

A numerical simulation of the stress field of the solidified shell in the mold during continuous casting of peritectic steel slab was calculated with commercial software. The results showed that the maximal stress on wide face of the solidified shell was located at the corner and near middle of the slab, and it increased with increasing the width of slab. In addition, the stress was also influenced by operating parameters such as superheat degree, drawing speed and cooling intensity of the mold, and the maximal stress value and its position changed with these parameters. For the slab with section size of 3200mm×150mm, the proper drawing speed was around 1.2m/min, with cooling intensity of 5500L/min while the superheat degree was 15°C to 25°C in order to prevent longitudinal crack occurring during peritectic steel continuous casting.

Jan 1, 2009

By Cem Colakoglu

In this study, nickel containing iron alloys were produced by carbothermal reduction of lateritic nickel ores obtained from Manisa - Caldag region of Turkiye in order to investigate the reaction mechanism of nickel and cobalt. In the experiments, the lateritic ore containing 1.58 wt.% Ni and 0.12 wt.% Co was calcined in a semi-pilot scale rotary furnace at 1100°C for 1 hour. Then, a mixture of calcined ore and metallurgical coke was reacted in sintered alumina crucibles using a graphite resistance tube furnace at different time (0- 60 min) and temperature (1500-1600°C).

Jan 1, 2009

By Chao Lian, Hongxu Li, Hao Bai, Wei Wei

"Application of high-emissivity coating on inner walls in industrial furnaces increases the furnace thermal efficiency. The coating with high emissivity strengthens radiation heat transfer in the furnace, however, according to Wien's displacement law and Planck's radiation law, under heating temperature, the wavelengths of the radiation transfer are mostly between 1-5 µm, implying that increasing emissivity of the coating in near infrared band is more effective for higher thermal efficiency. In this paper, a new CuO-ZnO-based coating material sintered at 1600K was developed. The emissivity of the samples were measured and the result shows that, in near-infrared band, the emissivity of the sample reaches 0.98 at 773K with 13at.% of CuO doped in ZnO. In addition, the effects of CuO doping and use temperature on emissivity were also discussed. Furthermore, crystallization behaviors of ZnO-CuO sintering were investigated by DTA,XRD and SEM-EDS etc., which offered information for possible optimal design of the material.1. IntroductionIndustrial furnaces are widely used in various industrial heating. For example, the metal smelting furnace, ore sintering furnace in metallurgical industry; the distillation furnace, cracking furnace in petroleum industry etc,. The research on efficient energy saving technology has important significance. High emissivity coatings are widely used in many high temperature applications to effectively transfer the heat by radiation [ 1]. The theoretical calculation and experimental studies have shown that, coated high emissivity coating in the heating surface is an effective method to enlarge the infrared radiation power [2].At present, the infrared high emissivity coating has been widely used in China, and have been achieved remarkable energy saving effect. According to Wien' s displacement law and Planck' slaw, most energy of the black body at high temperature is radiated in the wavelength range of l-5µm; however it happens that many materials have the low emissivity within this range. Thus, it is important to improve the near-infrared band emissivity of materials [3]."

Jan 1, 2013

By Jefferson Caponero

The tire is an expressive component of Municipal Solid Waste, manly when its occupied volume is considered. Its treatment by pyrolysis stands for a list of advantages, such as: landfill releasing and a production of a high quality fuel. The exploitation of new natural resources is becoming more difficult each day, basically due to the environmental damages caused by this type of activity. This work presents a study on the thermal behaviour of Brazilian tires using thermogravimetric analysis and differential thermal analysis, in order to optimise the pyrolysis process of tires. Samples of I to 2 mm were investigated at atmospheres of nitrogen, argon, oxygen and mixtures of these gases at temperatures up to 1273K, under heating rates between 1 to 50 Klmin . The results showed that the behaviour of each sample is related to both the atmosphere composition and the heating rate.

Jan 1, 2001