Search Documents

By D. W. Lawler

Prior to the manufacture of sulphuric acid in metallurgical plants, the SO2 rich gas from the smelter, roaster, or furnace must be cleaned to removed particulates, volatile contaminants, SO3, and water. Cleaning is accomplished by contacting the. gas with cooled weak acid. The system is designed so that all the contaminants, originally in the gas are captured in the weak acid, which then becomes an effluent from the plant. Historically, the entire weak acid effluent stream has been treated for disposal, with no attempt to recycle or recover any part if it. This is becoming increasingly environmentally unacceptable, and operators must consider better methods of treatment and recovery. In this paper, Kvaerner Chemetics discuss a number of options that allow the contaminants to 'be separated from the acid' value. This will result in an acid byproduct that can be sold or used elsewhere, and will minimize the volume of hazardous byproducts that must be discharged.

Jan 1, 1998

By Hui Zhang

The leaching behavior of palladium powder in aqueous solutions containing NaCI or N'H4Cl was investigated. Cupric ion was used as an oxidant for the dissolution reaction. The effect of a number of leaching parameters such as temperature, concentration, stirring speed and surface area on the leaching rate was studied. The leaching system containing chloride and cupric ion was found to be very effective for the dissolution of metallic palladium. Based on the experimental results the overall leaching rate was believed to be controlled by a chemical reaction step. The dissolution rate of palladium was found to be first order with respect to the concentration of cupric ion and second order with respect to the concentration of chloride.

Jan 1, 1996

By S. B. Bortnikova

This paper presents the results of an investigation of the gold-silver oxidized ores at the Salair mine. West Siberia. High losses of precious metals during primary ore processing are the result of outdated technology that is not suited to treat the present ore compositions. The main mineralogical forms of gold and silver and their confinement to different grain size fractions have been determined. About 50% of gold in the slime fraction and 60% of the silver in the form of acanthite that are scattered from the secondary minerals are lost to the waste. The results of these investigations have provided the basis for the recommendation of a new technological process to upgrade the current practice of the gold extraction plant and for methods to reprocess the concentrates.

Jan 1, 1995

By Osamu Takai, Yoshiki Sato, Nobuhiro Tajima, Hiroyuki Sugimura

"Amorphous carbon thin films doped with nitrogen ( a-C:N) have been synthesized by means of shielded arc ion plating (SAIP). Their electron field emission properties, that is, threshold field strengths for electron emission and maximum emission current densities, were evaluated and compared with those of pure amorphous carbon (a-C) films prepared by the same SAIP apparatus. Among all of the fabricated a-C:N films, the a-C:N films with a N concentration of 23 %, which prepared using Nz arc plasm at a pressure of 1 Pa with applying a sample bias voltage of -100 V, showed the lowest threshold filed of 13.4 V/µm and the highest emission current density of 1.87 µAfcm2 at a field of20 V/µm. These field emission properties of the a-C:N film were much better than those of the a-C films. The best results obtained on the a-C film in this study were the lowest threshold filed of 15.5 V/µm and the highest emission current density of 0.052 µA/cm2 at a field of 20 V /µm. Nitrogen doping to aC was found to be effective for lowering threshold voltage for field emission and for increasing emission current density. The electron field emission characteristics of the a-C:N films depended not only on N concentration but also on chemical bonding state of nitrogen in the a-C:N films. The presence of the ~-C3N4-like phase, which contributes to improve wear resistance of a-C:N as well, distinguished by the NlsXPS peak at 400.5 eV is proved to be crucial in order to enhance field emission properties of a-C:N.IntroductionThere has been much interest in electron field emission from a cold cathode due to its potential applications in vacuum microelectronic devices including field emission displays which are expected as flat panel displays in next generation [l]. It is well known that efficient emission can be rather readily realized using tip-like shape cathodes, e.g., microfabricated three-dimensional electrodes [2], carbon nanotubes [3-5], etc. However, electron emission from planar surfaces is of particular importance since such a type of cathode is· simply fabricated and assembled into microelectronic circuits. Currently, amorphous carbon thin films doped with nitrogen (a-C:N) prepared by plasma processes have attracted attention because their threshold voltages of field emission are relatively low [6]. Among various methods for preparing a-C:N films, the process using arc plasma is of special interest since, in arc plasma, nitrogen is highly activated and new types of carbon nitride phase are expected to be synthesized. However, field emission properties of a-C:N prepared by arc plasma have been studied in less detail compared with that prepared by the other methods such as sputtering."

Jan 1, 2000

By R. Singh, C. Gong, J. Chaudhry

"Metalorganic chemical vapor deposition (MOCVD) is an ideal technique for the deposition of conducting and non-conducting oxide based thin film materials. In this paper we have presented a study of photo assisted MOCVD for the low temperature deposition of a number of oxide based advanced materials. We have used incoherent light sources as the source of optical and thermal energy in our MOCVD system. The vacuum ultraviolet (VUV) and ultraviolet (UV) photons can enhance the surface reaction of the absorbed molecules through the perturbation of the electronic state of binding between the absorbed molecules and the solid surface. Unlike plasma process, no surface damage is expected and high quality materials have been deposited. At a given substrate temperature, the performance of deposited film depends on the lamp configuration.INTRODUCTIONMetalorganic chemical vapor deposition (MOCVD) has become the standard manufacturing technique for the deposition of large area thin films of compound semiconductors. l.(.w-cost, high crystalline quality, atomically clean and sharp interfaces, atomic layer epitaxy, high throughput rates and potential for direct writing are some attractive features of MOCVD. Due to a number of potential advantages mentioned above, MOCVD is considered as an ideal technique for the deposition of various electronic and optical materials for a wide variety of applications. Rapid isothermal processing based on incoherent radiation as the source of optical and thermal energy is emerging as the key low thermal budget (integral of processing time and temperature) processing technique for the fabrication of current and next generation of microelectronic and optoelectronic devices and circuits [1]. In this paper we have demonstrated that the design of the lamp assembly plays an important role in determining the properties of the materials deposited by RIP assisted MOCVD. We have studied the growth rates, structural properties and electrical properties of Y2O3/Si structure. At a given substrate temperature, best results are obtained for the lamp assembly that provides maximum number of VUV and UV photons."

Jan 1, 1994

By C. M. Antony

The galvanizing process involves the use of accessory equipment in a series of aggressive environments including zinc ammonium chloride flux, molten zinc at 45S°C (850°F), and acid for stripping of adherent zinc. An Fe-Ni-Cr-Co alloy has been identified which combines excellent strength and resistance to molten zinc and acid attack making it suitable for accessory equipment. The alloy was field tested by a commercial galvanizer as basket material and was found to provide improved life compared to original low-alloy steel baskets while cross-section thickness was reduced 44%. Additionally, other associated processing cost savings were realized.

Jan 1, 1992

By J. J. Talja

An investigation of oxidation of various nickel concentrates was carried out using differential scanning calorimetry (DSC). The aim of this study was to determine the ignition temperature and investigate other oxidation behavior of various sulfide-based nickel concentrates. Variables in the experiments were mineralogy, particle size and partial pressure of oxygen with temperature increasing linearly at 25 K/min from 323 to 1023 K (50-750 °C). The igni¬tion temperature was determined to represent the starting point of rapid oxidation. The reac¬tion enthalpies of the concentrates were determined and the amount of heat generated up to various time were used to calculate the extent of reaction. Mineralogical changes at various stages of oxidation were also investigated. For this purpose a second set of DSC-experiments were carried out in which each experiment was interrupted at a desired temperature between 673-873 K. From these tests the weight loss of samples were determined and changes in the individual constituent of sulfide minerals were analyzed. For pentlandite-based Ni-concentrates the ignition temperature was 705-710 K (approximately 435 °C). Pyrite was the first sulfide to oxidize. Reactivity of the violarite-based concentrate was greater than those of the pentlandite-based concentrates. The stoi-chiometry of pentlandite changed before ignition because of preferential oxidation of iron. Rapid oxidation of the pentlandite mineral occurred at about 823 K (550 °C). By 900 K about 90 % of the iron in pentlandite was converted to hematite, and NiS containing some iron was formed.

Jan 1, 1994

By Andriy Burbelko, Daniel Gurgul, Wojciech Kapturkiewicz, Marcin Gómy

"The mathematical model of the globular eutectic solidification in 2D was designed. The proposed model is based on the Cellular Automaton Finite Differences (CA-FD) calculation method. The model has been used for studies of the primary austenite and of globular eutectic grains growth during the ductile iron solidification in the thin wall casting. The model mentioned above takes into account, among other things, non-uniform temperature distribution in the casting wall cross-section, kinetics of the austenite and graphite grains nucleation, solute diffusion and non-equilibrium nature of the interphase boundary migration.Some aspects of stochastic nature of the solidification processes are taken into account. The results of the CA solidification modeling have been shown, that differences between cooling curves obtained in the same conditions of the casting solidification may be a result of the stochastic nature of the grain nucleation.The results of modeling were compared with the experimental microstructure. The model is well worked for thin walled ductile iron casting, for fast solidification process.IntroductionNodular graphite cast iron, also known as ductile iron (DI), has major applications in critical engineering parts due to its mechanical properties and castability. The mechanical and physical properties of this material depend on the shape and number of the graphite grains andmicrostructure of the metallic matrix.Solidification of DI was a subject of many computer modeling programs described in literature [ 1-5], in which the stationary conditions of carbon diffusion in austenite is pre-assumed. Recently, a tendency for production of thin-walled castings has been observed [ 6-8]. In this technology, the process of the fast solidification may be very far from equilibrium and steadystate conditions [9].The purpose of the present work is a two-dimension model development for simulation of the DI structure formation during the solidification in the condition of non steady-state temperature and diffusion fields in the thin-wall casting.Model of process The CA-FD is one of the known methods of the simulation ofmicrostructure formation during the solidification [ 10, 11]. In the CA microstructure modeling the outer grain shape is the result of the simulation and does not superimposed beforehand. The model development for a onephase microstructure evolution is a subject of the numerous researches [12 -23]. Model of the eutectic solidification of DI in the uniform temperature field and superimposed cooling rate is known [24]."

Jan 1, 2013

By Bingyi Bai, Lifeng Yang, Yanling Guo, Jieyu Zhang, Guoding Gao

In terms of special resources with iron, niobium and rare earth coexisting in Baiyuneboite, the new smelting technology of ferrocolumbite was studied. Reduction experients for the Baiyuneboite and explores ore phase change of Baiyuneboite in the process of reduction was conducted with graphitic carbon as the main reducer and a temperature below 1000 ℃. Moreover, it studies the influence of reducer, roasting temperature and grind fineness on the reduction as well as focuses on the evolution course of iron phase. Through the analysis on in-situ XRD of the raw ore and carbon addition ore, it also develops microstructure change rules of Fe ore phase and ore phase of paragenetic elements for composite ore(Ca, Si, Nb, F) in the process of reduction roasting. In addition, the impacts of temperature on the reduction process are also discussed. With regard to minerals of different particle sizes, the thesis will explore their ore phase changes and microstructures after 10 hours’ reduction under 900 ℃.

Jan 1, 2015

By Steven R. Izatt

IBC Advanced Technologies, Inc. (IBC) has developed a mercury selective product, which can be used by sulfuric acid producers as either a polisher, or as the primary technology for mercury removal from sulfuric acid. The Molecular Recognition Technology (MRT) separations material selectively binds Hg2+, and to a lesser extent Hg+, out of concentrated sulfuric acid. Mercury output levels of less than 0.1 ppm can be attained by the MRT system. Pilot plant tests have been successfully conducted at base metal smelting operations. A large-scale commercial plant is due for commissioning in 2003. Results from these projects will be discussed.

Jan 1, 2003

By E. N. Mounsey

The paper addresses the design of the Zhong Tiao Shan Company (ZTS) Houma Ausmelt Technology copper smelter in People's Republic of China. The smelter represents the third copper smelter development using Ausmelt Technology, the first large scale (35,000 tpy blister copper) and the first smelter to use the Ausmelt Technology smelting and converting process steps in separate TSL vessels in a continuously operated process. The project will be realised through the combined efforts of ZTS, Ausmelt and ENFI, the Beijing Non-Ferrous Engineering Institute who provided partial detail engineering services in China. Ausmelt will provide the technology licence, basic and detailed furnace engineering packages and additional technical services including cold commissioning support and hot commissioning supervision.

Jan 1, 1999

By R. S. Celmer

The distributions of cobalt, molybdenum, copper, and selenium between nickel matte and silica-saturated iron silicate slag have been determined in the region of the metallic saturation boundary, at 1523 K. Results are given as a function of the composition of the coexisting Fe-Ni alloy and the activity of iron in the system. Under strongly reducing conditions, these minor elements display a marked preferential accumulation in the sulphide phase. It is shown that the dissolution of cobalt and molybdenum in slag follows an oxidative mechanism, and distribution equilibria are correlated with the oxygen potential. From these data, the thermodynamic properties of cobalt in nickel matte are computed. Further, comparisons of minor element partitions are made between the nickel and copper matte smelting cases under metal saturation conditions.

Jan 1, 1988

By Kan Song, Lin Liu, Hengzhi Fu, Jun Zhang, Haijun Su, Xiaojiao Jia

"Al2O3/YAG/ZrO2 eutectic in situ composite has been regarded as new generation of high temperature structural material due to its excellent performance even close to its melting point. The directionally solidified Al2O3/YAG/ZrO2 eutectic ceramics are prepared by recently developed Laser Floating Zone Melting (LFZM) apparatus in which a splitter mirror is used to obtain two beams with the same quality from one CO2 laser. With the two laser beams irradiate the sample from opposite directions, the sample is zone melted. The apparatus configuration and the solidification processing are described in detail. The solid/liquid interface morphology is studied and the mechanism of microstructure formation especially the characteristic of eutectic cellular is discussed. It is shown that YAG and ZrO2 phases play a leading role during the ternary eutectic growth. Meanwhile, the relationship between the solidification microstructure and the processing parameters are investigated.IntroductionAl2O3/YAG/ZrO2 ternary eutectic in situ composite, due to its excellent high temperature mechanical properties, is now considered to be a promising candidate material as a replacement of nickel based super alloy for new generation aero space engine turbine blade [1]. They exhibit flexural strength of 360-500 MPa from room temperature to 2073K in air atmosphere [2]. The compression creep strength at 1873K is 433MPa with the strain rate of 104/s [3]. However, because of the high melting point and complex physical properties, there remain still many difficulties for its application. One of the bottlenecks is the poor understanding of the relationship between microstructure and solidification conditions."

Jan 1, 2012

By J. B. See

Emeritus Professor David Robertson of the Missouri University of Science and Technology was born in Dublin Ireland on 29 December 1941. His father was a merchant navy Captain who served during WWII and during David’s early years his family lived in Dublin and Donegal where David went to the local elementary school. In 1954 he moved to London with his parents and attended Highgate School before commencing metallurgy at the Royal School of Mines, Imperial College, London in 1960.

Jan 1, 2014

By Masayoshi Matswnoto

The Kosaka Smelter and Refinery produces copper and lead, and has a history of more than 100 years as a metallurgical department of Dowa?s Kosaka Mine. The Smelter treats complex sulfide concentrates which are difficult to smelt. Valuable metals are recovered using various processes developed by Kosaka Smelter and Refinery. Effluent waters from the smelter contain large quantities of heavy metals. This paper describes how Kosaka Smelter and Refinery recovers valuable metals from various effluent waters and handles overall waste waters in order to meet strict environmental standards.

Jan 1, 1993

By Soumendra Basu, Uday Pal, Yang Yu, Srikanth Gopalan, Karl Ludwig, Deniz Cetin, Jacob Davis

"A limiting factor for Solid Oxide Fuel Cell (SOFC) performance is the oxygen reduction reaction (ORR) at the cathode surface. Changes in the surface composition and structure on annealing at 800°C has been studied, since these can influence the ORR. Idealized single crystals of cathode materials La0.8Sr0.2MnO3 (LSM) and La1-xSrxCoyFe1-yO3 (LSCF) were grown as heteroepitaxial thin films on lattice matched single crystal substrates. Changes upon heating the films to operating temperature and pressures were characterized using various synchrotron x-ray techniques. Total Reflection X-ray Fluorescence (TXRF) measurements, which probe compositional changes, were made at high temperature in real time. The LSM surfaces were found to develop manganese enrichment when heated. Highly strontium doped LSCF were found to develop strontium-rich surfaces. HArd X-ray PhotoElectron Spectroscopy (HAXPES) was used to investigate the electronic structure of the materials. Highly strontium doped LSCF precipitates a surface strontium phase that contains both oxide and carbonate contributions.IntroductionSolid oxide fuel cells (SOFCs) are chemical to electrical energy conversion devices that could potentially reshape how energy demands are fulfilled. SOFCs have a potential efficiency over 70%, fuel flexibility, low emissions, and low degradation over long time scales. Commonly, SOFCs are operated at high temperatures (above 800°C). At these temperatures expensive housing is needed to contain an operating stack as well as coatings to contain the oxidation of the metallic interconnects. Lowering the temperature of an operating device would allow for more conventional materials to be used, thus lowering overall cost. Understanding the reaction kinetics of the oxygen reduction reaction at the surface of the cathode is vital to designing a system that will perform well at lower temperatures. A commercialization goal is to reduce operating temperatures without sacrificing performance.In order to exploit the advantages of SOFCs, an understanding is needed of the surface chemical states of cations on the surface of the cathode and how this relates to the oxygen reduction reaction (ORR):"

Jan 1, 2014

By cheng Peng-fei, TANG Hai-yan, guo Xiao-chen, LI Jing-she, Liang Yong-cang, Zhao Baojun

The origin and evolution of non-metallic inclusions for Al-killed casing steel during EAF-LFVD- CC process were studied by industrial tracer experiments. The formations of Al2O3 and MgO·Al2O3 micro- and macro-inclusions from ladle slag were analyzed by theoretical calculations. The results show that micro-inclusions were formed during deoxidation and temperature decreasing in the process of casting, most of the macro-inclusions come from entrapped ladle and mold slags. In addition, most of the Al2O3 formed were modified into 12CaO·7Al2O3 and 3CaO·Al2O3 inclusions which are liquid at steelmaking temperature. MnS cannot be fully modified to CaS and it was only wrapped outside the alumina or calcium aluminate in the form of (Ca,Mn)S with the amount of Ca-Si wire fed during the test.

Jan 1, 2016

By Carlos Carnurri

A characterization of mechanical properties of fire refined copper has been done in order to link ductility with oxygen content. The results show four different copper mechanical behaviours as temperature increases, where the oxygen con- tent, as Cu20 segregated, has a deleterious effect on ductility. It is concluded that until 500 ppm oxygen content, the fire refined copper could be rolled without remelting for deoxidation. Also a subsequent cold rolling could be done without intermediate annealing.

Jan 1, 1994

By Peter K. Everett

One of the major driving forces behind the development of the Intec Copper Process has been the increasingly stringent regulations governing SO2 emissions and, in some parts of the world, a declining H2SO4 market. Other incentives include operating cost (9.2 US c/lb Cu), capital cost (US $1400/annual tonne Cu compared with smelter cost of US$3-4000/annual tonne Cu) and the ability to treat low grade and contaminated concentrates. With such advantageous features, widespread use of the process is expected over time, leading to the production of large amounts of residues containing around 25% elemental sulfur, together with approximately 50-60 % akaganeite (FeOOH) and the ganggue minerals originally present in the concentrate feed. This paper briefly describes the Intec process chemistry involved in the formation of elemental sulfur, thereby avoiding atmospheric sulfur dioxide pollution, and the investigations to be carried out either to extract it or to turn the residue into a valuable by-product while minimising any adverse environmental effects, The process is being developed jointly by a group of fifteen major international mining companies.

Jan 1, 1996

By David G. Dixon

A mathematical model is derived in dimensionless form which simulates the effluent concentration response of reagents from spent heaps under both fresh and recycled water rinsing. The model is based on dispersion from isochoric pathways distributed in length and cross-section, oriented normal to convection channels in ideal plug flow. The effects of heap height, rinsate flow, and initial reagent concentration are examined. It is shown that the rinsing cycle undergoes a distinct shift between fast and slow rinsing at a certain time depending on the amount of stagnant solution in the heap, and the distribution of dispersion pathways. Results of preliminary column rinsing tests on both agglomerated and unagglomerated ores are presented which partially validate the model.

Jan 1, 1994