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By Fuming Wang, Xi Chen, Shuai Liu, Changrong Li, Dan Wu, Yaxu Zheng

The effects of B content and austenitizing temperature on hardenability and toughness of Cr–Mo alloy steel have been studied. The results show that the hardenability is deteriorated with increasing B content and austenitizing temperature. With increasing temperature, more and more B containing particles were dissolved in austenite and increase the amount of B atoms segregating at grain boundaries. Moreover, the coarsening grains reduce area of grain boundaries and also increase the amount of B atoms at unit grain boundary, excessive B atoms segregating at grain boundaries promotes precipitation of M2B, which accelerates ferrite nucleation and reduces hardenability. The main elements in M2B phase are Fe, Cr, Mo and B. The B atoms segregating at grain boundaries during austenitizing promote precipitation of M2B during tempering which deteriorate toughness significantly.

Mar 1, 2018

By C. Palacios

The Plant, which was started up in April 1970, was originally designed for a capacity of 40.000 ton of cathodes per annum, using 12 sections, containing 408 cells. Since then the addition of another 8 sections containing 280 cells and using the Reverse Current System has made possible the increased output of 109.000 ton. The quality of the cathodes produced is excellent. The extension of the Electrolytic Refinery, by the introduction of the Reverse Current System, has been a great success and no problem has arisen in the new equipment or in the modifications carried out in the plant. The operation of the plant has improved due to better control procedures.

Jan 1, 1976

By Isadora Dias Perez, Denise C. Romano Espinosa, Flávia P. Cianga Silvas, Jorge A. Soares Tenório, Mónica M. Jiménez Correa

In view of the rising generation of wastewater containing metals, sustainable and clean techniques to recover them are being researched. This study investigated the adsorption of aluminum, cobalt, chromium, copper, iron (III), magnesium, manganese, nickel and zinc presents in a synthetic ef fluent by chelating ion exchange resin Dowex XUS43605. The resin was tested in columns experiments and was analyzed the flow rate (0.45, 0.66 and 1.11 BV/h), at pH 1.5 and 20 °C. After loading the column, the elution experiments occurred with 1 M of H2SO4 and 4 M of NH4O. The concentration of the metals in solution was obtained by X-ray fluorescence spectrometry energy dispersive (EDX). The results showed that the breakthrough experimental curves demonstrated that the main metals (aluminum, cobalt, manganese and zinc) were immediately broken through just after the initiation of the feeding, while the breakthrough of copper began later. Therefore, the study showed that the chelating resin could be used to treat contaminated effluents with metals.

Mar 1, 2017

By Dong Hoon Han

The sulfation rates of magnesium oxide and calcium oxide (molar ratio 7:3) contained in calcined CMA ( calcium magnesium acetate) by SO2 were measured. The experiments were carried out in the temperature range 700 to 1100 °C and under the SO2 concentrations of 0.3 to I mol % (5 % 02). In the low-temperature range below 830 °C the reaction produced CaSO4.3MgSO4 and unreacted MgO, but no MgSO4 phase. The formation of CaSO4.3MgSO4 phase has a significant implication in that it allows the utilization of MgO for SO2 removal whereas the sulfation of MgO from conventional sources is so slow that it is of no practical interest. Thus, the calcined CMA can remove SO2 at lower temperatures than conventional SO2 absorbents and at a greater capacity. Above 950 °C only CaO reacts with SO2, but at a much greater rate than the calcined Ca(OH)2, which is one of the most reactive SO2 absorbents.

Jan 1, 1998

By M. Wu, A. Kharicha, A. Ludwig

"The droplet formation during melting of a 400 mm diameter electrode is simulated with a multiphase-MHD approach. The computational model includes a layer of slag and a layer of liquid steel. A VOF approach is used for the interface tracking and a potential formulation is used for the electric and the magnetic field. The Lorentz force and the Joule heating are recalculated at each time step in function of the phase distribution. The first results provided by this model are presented.IntroductionThe Electro-Slag-Remelting (ESR) process is an advanced technology for the production of components of e.g. high quality steels [ 1-9]. An alternating current (Figure 1) is passed from a conventionally melted and cast solid electrode through a layer of molten slag to the baseplate. Because of the electrical resistivity of the slag, Joule heating is generated and the slag transfers this energy to ingot and mould surfaces and to the melting electrode tip. The molten metal produced in the form of droplets passes through the slag and feeds a liquid pool from where directional solidification takes place. The slag and the ingot are contained in a water cooled copper mould. As also the baseplate is water cooled, a heat flow regime is imposed that gives controlled solidification, and this results in improved structure characteristics of ESR ingots.This process involves two liquids, a liquid metal and a liquid slag. Each liquid is subject to a phase change due to melting and/or solidification. From a fluid dynamic point of view, the ESR process is clearly a multiphase process, with free interfaces (slag/pool, gas/slag), and with a mixed area (slag and falling steel droplets) [ 10-15].Physically, the development of the heat and mass transfer at the slag/droplet interface is important for the final ingot quality, composition and cleanliness. Visual observations of the droplet formation just under the electrode being melted is almost impossible. Due to the presence of high temperatures, opacity of the materials, and the presence of the mould it is not possible to directly observe the behaviour the slag/pool interface. Although usually assumed flat [1-9], a previous work [10] using a Volume of fluid (VOF) model has shown that the interface shape between a layer of slag and steel layer in a cylindrical cavity is highly coupled with the distribution of the electric current. A full scale simulation of the ESR process using a VOF model has shown that the shape of the pool interface is likely to be non flat."

Jan 1, 2011

By M. Olper, M. Maccagni

"The crude zinc oxides (CZO) produced in any thennal process dealing with EAF dust also contain lead, cadmium, and a considerable amount of halides (chlorides and fluorides). The high halide contents make these crude zinc oxides less and less attractive, both technically and economically, and a further refining procedure is nece'ssary to meet the zinc and zinc oxide market requirements.Hydrometallurgical techniques commercially used to dehalogenate the crude zinc oxides are not effective enough to upgrade the crude zinc oxides to the required specification for their direct use in the traditional sulphuric electrolysis by primary zinc producers.The EZINEX® PROCESS has solved the problem of the halides contained in the crude zinc oxides. This process is the only proven technology electrowinning zinc from a chloridebased electrolyte in a conventional cell house. This paper discusses the process economics taking the data from feasibility studies of different size commercial plants."

Jan 1, 2000

By M. Wenzel, Dang Thanh Tung, Nguyen Anh Duc, Nguyen Huu Luong, Dang Van Sy, N. Kelly, K. Gloe, K. Kretschmer, Phuc Nguyen Le, K. Schnaars, S. Robles M, L. Götzke, J. J. Weigand

The recovery of rare earth metals from secondary sources has attracted much attention due to their ever expanding demand in the high-tech industry. The studies reported here focus on the hydrometallurgical recovery of lanthanum and cerium from spent fluid catalytic cracking (FCC) catalysts in a two-step process: leaching with nitric acid and solvent extraction by tri-n-butyl phosphate (TBP) and di(2-ethylhexyl)phosphoric acid (D2EHPA). The experiments show a high dissolution yield of about 93% lanthanum and 42% cerium in a single leaching step with 2 M (126 g/L) HNO3 at 80 °C; only 11% aluminum has been dissolved simultaneously. In the subsequent solvent extraction step the best results for this leach liquor could be achieved using a 1:1 mixture of 25% (v/v) TBP (0.92 M) and 25% (v/v) D2EHPA (0.76 M) in n-decane without the need for any pH adjustment. In that case La(III) and Ce(III) can be extracted with 60% and 74% yield respectively in one stage from the majority of accompanying matrix elements. In particular no extraction of Al(III) could be observed under these conditions.

Jan 1, 2016

By Eun Duck Park

The gold catalyst supported on iron oxide was prepared from gold dissolved in aqua regia by a deposition-precipitation method and applied to CO oxidation in the absence and presence of hydrogen. Some characterization methods such as X-ray diffraction (XRD), nitrogen adsorption, transmission electron microscopy (TEM), temperature programmed reduction (TPR), temperature programmed oxidation (TPO), and the pulsed CO chemisorption with temperature programmed desorption (TPD) were conducted to explain different catalytic activities of Au/Fe2O3 catalyst pretreated at different conditions. The particle size of gold was about 10 nm for Au/Fe2O3 calcined in air at 373 and 573 K. For complete CO oxidation, the decreasing CO conversion with a reaction time was observed at low temperatures but its initial catalytic activity can be restored by a heat treatment at high temperatures. This catalyst was quite active for the selective CO oxidation in the presence of hydrogen especially at low temperatures. In the presence of hydrogen, the deactivation was significantly diminished.

Jan 1, 2006

By J. T. I. Poijärvi

The smelter off-gas cleaning and the weak acid treatment at Outokumpu Harjavalta Metals Oy are presented and described in this paper. The smelter consists of the copper and nickel smelters and the acid plant of three separate acid plants two of which are double contact and one single plant and of one liquid sulphur dioxide plant. The preliminary cooling and flue dust separation of the smelter off....,gases from the copper ?and nickel flash smelting furnaces and converters? in the waste heat boilers and in the hot electrostatic precipitators are described. The final cooling and cleaning of the gases in the scrubbers at the sulphuric acid plant and the treatment of the weak acid in the vacuum and in the submerged combustion evaporators for the removal of impurities are presented as well as the treatment of the condensates from the evaporators. The attention is paid to the generation of sulphur trioxide in the smelter off-gas.and to the treatment of that in the weak acid bleed-off and to the utilization of the treated acid.

Jan 1, 1992

Primary sulphidic gold ores in the Archean provinces of Western Australia can be broadly sub-divided into pyritic, pyrite-telluride, arsenical and antimonial types. Pyritic ores contain only native gold, and are essentially not refractory. Arsenical ores almost always carry some invisible gold, and may vary from mildly to highly refractory. Pyrite-telluride ores contain gold-bearing tellurides, and are refractory to varying degrees. Antimonial ores usually contain aurostibite, and may be very difficult to process. A classification scheme for metallurgical processing, based on mineralogy, is proposed for the ores, and implications for processing are discussed.

Jan 1, 1995

By V. I. Lakshmanan

Wastes when produced can be reused or recycled prior to disposal. Industries that cause environmental concerns during manufacturing include primary materials and primary metals. Pollution prevention mechanisms to achieve waste reduction require new separation, reclamation, control and process simulation technologies. Substituting recyclables for virgin resources will reduce energy use, water pollution, air pollution, water use and mining wastes. Shrinking landfill space will spur new technologies for waste treatment and recycling. These situations hence offer opportunities for innovative flowsheets with appropriate separation technologies. Development of innovative flowsheets to treat recyclables offer unique opportunities for process/product development, obtain green products and hence market advantage. The paper will illustrate with selected innovative flowsheets to treat recyclables.

Jan 1, 1996

By Junbiao Liu

Rutile is mostly produced from placer sands. Its beneficiation from primary deposits has rarely been investigated. However, there is interest in primary deposit because of the depletion of sand deposits. The Zaoyang deposit in China is the only rutile primary deposit currently mined. The plant employs a Tabling-Magnetic process which recovers only 20% Ti02 at a grade of 87%. This study shows that significant improvement on the recovery (52% at the same grade) can be achieved. This study includes a detailed mineralogical examination and the development of a processing flowsheet of the ore. The gangues are primarily amphiboles, garnets, zoisites, and chlorites. The liberation of rutile occurs at about 200 mesh. Gravitational, flotation, and magnetic separations are all employed in the process developed, depending on the mineral characteristics and experimental results. The flotations circuit utilizes benzyl arsonic acid to float rutile and sodium fluosilicate to depress the gangues. This is a new reagent scheme for rutile flotation.

Jan 1, 1989

By Bhagyadhar Bhoi, Chitta Ranjan Mishra, Hara Prasanna Mishra

"In the Sukinda Valley of Orissa, India, the total quantity of nickel ore reserves comprising of both lateritic and chromite over burden(COB) have been estimated at around 231 million tonnes containing 0.3 to 0.9% Ni. While mining of one tonne of Chromite ore, around 6-7 tonnes of chromite over burden are removed. These overburden materials are disposed as waste materials, which causes lot of environmental hazards and ecological imbalance. India imports a large amount of nickel and ferro-nickel to meet its growing demands in various sectors. For import substitutions, efforts have been made to produced ferro-nickel from the lean deposits of nickel bearing lateritic ores/ chromite over burden materials by reduction roasting followed by magnetic separation and then the nickel rich magnetic fraction is smelted to produce ferro-nickel. It has been possible to produce ferro-nickel of grade varying from 4-25% nickel.IntroductionDuring mining of chromite ore, large quantities of overburden materials are being generated. The materials amount to approximately 10 million tones per year contain around 0.3-0.9% Ni, 0.02-0.06% Co, 20-50% Fe and 4-9% Cr2O3 depending upon the location and the depth of the mine. These materials presently do not find any application for the extraction of nickel due to lack of a suitable technology. The materials are also unsuitable for ferro-nickel making because of their very high iron to nickel ratio. The country is seriously looking for a suitable technology to utilize these resources as its entire domestic requirements of nickel is met though imports. In this connection, a systematic approach has been made at the Institute of Minerals and Materials Technology, Bhubaneswar to develop a process for ferro-nickel making from this indigenous resource."

Jan 1, 2011

By William Petruk

The primary requisite for a successful extractive metallurgy operation is to grind an ore fine enough to liberate the minerals so that they can be concentrated, or to expose mineral surfaces so that the minerals can be leached. The ease or difficulty of liberating or exposing the mineral grains is dependent upon the mineral textures such as grain size, crystallinity and bonding between mineral grains. In particular, mineral grains with straight grain boundaries and a weak bonding to other minerals are easily liberated and readily concentrated into high grade concentrates. In contrast mineral grains that have re-entrant boundaries and are strongly bonded to their neighbours are not easily liberated and will not produce high grade concentrates, even with regrinding. Similarly, inclusions that occur along fractures and grain boundaries can be readily exposed and leached. Whereas minute random inclusions in large grains will not be liberated or exposed unless they occur along planes of weakness.

Jan 1, 1995

Lead blast furnace water-jacket stability was investigated by examining samples from the Port Pirie Lead Smelter. The compositions of the phases formed in the samples were analysed using Scanning Electron Microscopy (SEM) and Electron Probe X-ray Microanalyser (EPMA). Phase equilibria analysis and thermodynamic modelling was undertaken using FactSage with latest thermodynamic database for the slag/matte/metal/speiss/solids multi-component Cu2O–PbO–ZnO– Al2O3–CaO–MgO–FeO–Fe2O3–SiO2–S major and As–Bi–Sb–Sn–Ag–Au minor elements system. Results indicated that the stability of the water-jacket steel wall without freeze-lining is influenced by formation of the complex Fe-rich speiss phase at critical As concentrations. The integrity of the furnace walls with freeze-lining is critically dependent of the stability of the oxide-based freeze-lining which is dependent on various factors including most critical one—the proportion of solids determined by the slag chemistry and fluxing. Thermodynamic modelling of the lead blast furnace operation indicated limiting thermochemical conditions for the water-jacket stability. Factors and controls critical to the water-jackets integrity are discussed.

By Toshitaka Ota, Hisao Suzuki, Minoru Takahashi

"Perovskite-type lead zinc niobate (PZN) exhibits excellent electrical properties such as high dielectric constant, high electrostrictive coefficient and superior piezoelectricity. Therefore, PZN ceramics are very promising for high performance electronic devices. However, perovskite phase PZN is not stable under the ambient atmosphere. Accordingly, it is very difficult to prepare single-phase perovskite PZN ceramics. In this study, A-site cation of lead was partially substituted for barium to stabilize the perovskite phase of the PZN (Ba-doped PZN) powder. In addition, molecular design of an alkoxide precursor was controlled for a low-temperature processing. As a result, molecular design to suppress the lead-volatilization during calcination was preferred for a low-temperature processing. Processing temperature for a single-phase perovskite was depended on the amount of barium dopant. Doping of20 mole% of barium resulted in the single phase perovskite at 900 °C. The temperature for the single phase perovskite of Ba-doped PZN powder, which depended upon the amount of Ba-doping, was lower than that of the powder prepared by the atmosphere controlled conventional powder processing at least by 150 °C.IntroductionFerroelectric thin films and powders with perovskite structure are of renewed interest for micro-electronic applications, including ferroelectric random access memory (FRAM), dynamic random access memory (DRAM), and thin-layer capacitors integrated onto a silicon wafer [1-3]. In addition, recent advancement in micro-machine requires a high performance micro-actuator [4]. A perovskite type relaxor of Pb(Zn113 Nb213)03 is one of the promising materials for a high performance capacitor and microactuator because of their high permittivity and electrostrictive coefficient [5]. Therefore, this paper focuses on the low temperature processing of Ba-doped PZN powders.Chemical solution deposition (CSD) from molecular-designed alkoxide precursor solution is one of the most promising techniques for processing high-performance powders and thin films because it offers precise control of compositions on a molecular scale as well as a low processing temperature [6]. However, chemical solution deposition of perovskite type PZN powders and ceramics are very difficult because of the formation of stable pyrochlore phases. Therefore in the past, PZN powders and single crystal have been prepared by the hydrothermal method or flux method as well as the partial substitution method of a A-site cation [7-10]. In this study, a suitable molecular design for a preparation of perovskite type Ba-doped PZN powders with a chemical solution deposition process is investigated as well as the effect of A-site cation substitution. Chemical solution deposition from molecular-designed alkoxide precursor solution is expected to decrease the amount of a A-site substitution and/or a crystallization temperature for a single phase perovskite. This paper describes ""the relation between molecular-design and processing temperatures for a single-phase perovskite of Ba-doped PZN powders in comparison with the conventional oxides mixing method."

Jan 1, 2000

By John L. H. Patterson

Handheld XRF has become the favorite way of measuring the content and identity of alloys in the field. This is because of the very portable nature of the instrumentation and its simple operation. However, these analyzers have been unable to determine the concentration of the light elements like Mg and Si due to the very low energy of the x-rays produced by these elements. In the past accessories such as vacuum and He flush have given some analyzers the ability to determine these light elements with modest detection limits. The introduction of the Silicon Drift Detector (SDD) into this class of instrumentation has added a new level of analysis capability to portable XRF instrumentation. X-ray fluorescence is achieved by exciting a sample with a beam of x-rays, which in recent portable equipment are generated by a small tube. This results in the emission of characteristic x-rays from the sample under test. By measuring the energy of each x-ray it is possible to determine what element generated it. By counting the number of x-rays at each energy it is possible to determine the concentration of each element. The detection limit for each element is dependent upon the number of x-rays which reach the detector. As the number of x-rays increases the detection limit will improve. One of the major factors in an x-ray reaching the detector is the energy of the x-ray. As the energy of an x-ray increases the probability of that x-ray reaching the detector increases. The energy of an x-ray is inversely proportional to the atomic number (AN) of the element generating the x-ray. For example, an iron x-ray (AN=26) is 6.40 keV while an aluminum x-ray (AN=13) is 1.49 keV. As the energy decreases, the detection of the x-ray becomes less and less probable because the x-ray may be absorbed by the windows which are part of the instrument and detector or the air in the path between the sample and detector. In SiPIN based portable XRF analyzers, the lowest element which is detected with acceptable detection limits is normally considered to be Ti (AN=22). The detection limits for 60 second measurements on typical SiPIN XRF analyzer are given in Table I. Thus, portable analyzers have not been useful for measurement of aluminum and titanium alloys as major components of these alloys are Mg (AN=12), Al (AN=13) and Si (AN=14).

Jan 1, 2009

By Lee Fergusson

"The primary features of ViroMine™ Technology are introduced and applications of ViroMine™ Technology to mine site remediation and the treatment of a variety of intractable waste-streams, including a technical discussion of acid neutralizing capacity, metals binding capacity and longterm stability of results. Outcomes from four applications at high-profile international mine sites are presented: 1) the superfund site at the Gilt Edge Mine, South Dakota, USA (four years of data on the treatment of acidity, TDS and metals such as Al, Co, Fe, Mn and Zn); 2) one of Australia’s most polluted sites at King River Delta in Tasmania (treatment of TAA and TPA, and metal and metalloid contaminants such as As, Cr and Hg); 3) The Aljustrel “Aqua Forte” mine site in Portugal (high acidity, metal and metalloid contaminants such as Al, As, Cu and Zn) and 4) the Ulsan Iron Ore Mine at Ulsan, South Korea (treatment of metal and metalloid contaminants such as As, Cd and Ni).IntroductionThe commercialisation of ViroMine™ Technology has resolved some of the most intractable pollution issues associated with historic mining ventures on a global scale and has facilitated the neutralisation of Acid Rock Drainage (ARD), remediation of acidic and metal contaminated impoundments (including tailings dams) and promoted revegetation on tailings deposits and waste rock dumps. ViroMine™ Technology also enables current mining ventures to manage effluent simply and efficiently to meet increasingly stringent environmental standards and is enabling the mining sector to reconceptualise the management of mine spoil. The abilities of ViroMine™ reagents to neutralise the actual and potential acidity of sulphidic mine spoil coupled with the ability to bind metal and metalloid contaminants into non-bio-available forms are the key features delivering environmental and economic benefits to the mining sector and the broader community. Results from four projects utilising ViroMine™ Technology are presented to highlight the suitability of ViroMine™ Technology to treat all forms sulphidic mining wastes. 37"

Jan 1, 2008

By Filipe de Menezes Torres, Augusto Pereira de Sa, Itavahn Alves da Silva, Eliana Ferreira Rodrigues, Carlos Antonio da Silva, Varadarajan Seshadri

Top slag eye opening which happens as a result of gas injection is a function of the gas flow rate in addition to other factors such as ladle geometry, porous plug location as well as slag properties. Slag eye opening leads to entrapment of atmospheric nitrogen, oxygen by the steel melt affecting adversely the steel quality. In this work aspects of mixing and eye formation in steel making ladles with inert gas injection have been analyzed through physical and mathematical modeling techniques. Influence of ladle, gas flow rate and distribution and slag properties has been assessed. A correlation for estimating eye opening has been developed. Results from PIV measurements and images of eye opening obtained using a camera have been utilized to validate results from CFD simulation.

Jan 1, 2015

By Andreas Siegmund

Cast or rolled lead anodes employed in zinc electrowinning typically contain between 0.5?1.0% silver to decrease the overall corrosion rate. The production of cast lead-silver or lead-silver-calcium anodes often results in the formation of numerous holes, voids or laps in the anode surface that can initiate internal corrosion in localized areas. In rolled anodes the presence of internal porosity is significantly reduced, thus resulting in extended service life. The obtained grain structure of cast or rolled Pb-Ag anodes, however, requires a relatively long period of time to form a stable protective PbO2/MnO2 layer that can evolve oxygen without excessive lead contamination of the cathode. Therefore, these anodes are often mechanically, chemically or electrochemically conditioned prior to being placed in the electrowinning process. RSR Technologies has developed an improved anode for zinc electrowinning. The anode consists of a rolled Pb-Ag-Ca-alloy with controlled surface grain structure. The preferred calcium and silver content of the alloy is 0.05?0.08 % and 0.3?0.4%, respectively. Since May 2001, industrial-scale tests have been carried out at two zinc refineries in North America in industrial electrowinning cells. The controlled grain structure of these anodes allows forming an adherent protective oxide coating within a short period of several days when placed in an electrowinning cell without the necessity of being preconditioned. Anode sludge growth is evenly distributed. The anodes stay dimensionally stable and no short-circuits have been observed. Consequently, low corrosion rates and improved current efficiencies have been achieved.

Jan 1, 2003