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By David R. Jessey

An ore microscopic and geochemical study of the nickel-cobalt occurrence in the Southeast Missouri Mining District has revealed several significant relationships. Siegenite [(Ni,Co)3S4] is the dominant nickel-cobalt sulfide in the ores, however, several other members of the thiospi¬nel group (AB2S4) occur: carrollite (CuCo2S4), nickelean carrollite [(Co,Ni,Cu)3S4], fletcherite [Cu(Ni,Co)2S4] and polydymite (Ni 3S4). In addition, bravoite [(Ni,Fe)S2], vaesite (NiS2), millerite (NiS) and gersdorffite (NiAsS) are present. Thiospinel composition varies dramatically within the district. Paragenetic studies have shown that the stratigraphically lowest thiospinels are the most cobalt-copper-rich. A detailed ore microscopic study of the AMAX Lead Company Buick mine has also shown significant changes in mineralogical association, texture and grain size of the siegenite along the north-south strike of the major ore bodies. Siegenite commonly replaces and veins chalcopyrite and is subsequently replaced by sphalerite. Less commonly, siegenite and chalcopyrite are observed to form linear replacements along sphalerite grain boundaries. The grain size of the siegenite varies markedly, but in a predictable north-south pattern that is consistent with a genetic model formulated from geo-chemical data. The compositional as well as textural trends displayed by the thiospinel mineralization could be exploited to optimize recovery of any or all thiospinels of economic interest.

Jan 1, 1981

By Dan Michaelsen, Warwick Stewart

"PT Kaltim Prima Coal (KPC) is a large-scale truck and shovel operation mining thermal-coal in East Kalimantan, Indonesia. The operation produces 15 million tonnes of coal and mines over 120 million bank cubic metres of overburden annually. Approximately 35 percent of the waste rock is classified as potentially acid forming. Acid drainage must therefore be managed to prevent acid formation from spoil dumps and mined-out areas.KPC aims to prevent acid production in dumps by covering potentially acid forming spoils with materials identified as non acid-forming. The covers, built to engineering standards, minimise the flux of oxygen and water to pyritic spoils, thereby controlling the oxidation reaction, and reducing ARD discharge to negligible rates. Cover designs and cover materials vary according to stability, materials availability, equipment availability, and cost effectiveness. A modified field net acid generation (NAG) test procedure has been developed at KPC to identify and segregate overburden geochemical types. This paper discusses the ARD management strategies and operational procedures adopted by KPC to manage potentially acid forming waste rock. The development and field application of the NAG procedure at KPC is presented in a companion paper. Analytical"

Jan 1, 1999

By Lanre Oshinowo

Computational Fluid Dynamics (CFD) is used in conjunction with process modelling at HATCH to achieve a superior level of confidence in the process design of hydrometallurgical process plants. The use of these tools to evaluate designs through virtual prototyping reduces the risks associated with making design decisions. This paper highlights the development of a co-simulation strategy at Hatch for the seamless integration of process modeling software addressing different scales (process time and space): flowsheet level models and .equipment level models. With co-simulation, the process design engineers can improve design accuracy, troubleshoot and optimize performance and influence decisions impacting equipment operation by representing specific unit operations in the flowsheet model software with detailed CFD models. Specifically, this paper will focus on the co-simulation of a Ni/Co high-pressure acid leach (HPAL) process including heaters/heat exchangers and flash system, autoclave and quench/scrubber system. The knowledge developed can be transferable to other processes.

Jan 1, 2004

By Lin Yang, Minjun Tang, Shuishi Liu, Jianfeng Zhou, Linjiang Qing, Xiaolei Song, Yufeng Guo, Tao Jiang

"The dynamics of oolitic hematite magnetic roasting was studied. The results show that oolitic hematite magnetic roasting was controlled by the internal diffusion, and the diffusion coefficient was 9.018x10-7 m2·s-1when the oolitic hematite was roasted at 650°C. Magnetic susceptibility improves when temperature increases and roasted time prolonges under the condition of roasting at 650°Cfor 50min, with the magnetic susceptibility is 39.88%. CaF2 and Na2C03 can significantly improve the magnetic susceptibility at the same roasting condition, and the magnetic susceptibility was 63.35% and 57.99% respectively, thus the reduction of oolimic hematite was promoted.IntroductionWith the continual depletion of free-milling iron ores and its rising price, developing the abundant resources of oolitic hematite has become one of the main research areas. The oolitic hematite accounts for 10% of China's iron ore reserve, and it also accounts for 30% of red ore reserve in China [1]. In order to exploit the oolitic hematite, there are many beneficiation research methods, including fine grinding/selective flocculation/high intensity magnetic separation or flotation, high-gradient magnetic separation, low intensity magnetic separation/high intensity magnetic separation/reverse flotation, chloridizing roasting/acid pickling, magnetic roasting/leaching process etc [2]. However, the oolitic hematite is easy to slim and the valuable mineral is covered by the slim, because of the tiny granule of value mineral, then the ooides are formed due to the state of layer morphology formed by iron ore and ganaue minerals [3, 4]. Fairly good separation indexes were hard to be obtained by traditional separation due to its structural features, so the magnetic property of the iron minerals will be changed with the use of the magnetic roasting [5, 6], which result in hematite variably altered to magnetite and simplified technological process so that a good separation indexes will be obtained by using the low intensity magnetic separation. Therefore, in order to provide theoretical direction of how to use the oolitic hematite effectively through the magnetic roasting, the oolitic hematite of GuiZhou province was studied, which emphasized on researching the dynamics of oolitic hematite magnetic roasting."

Jan 1, 2013

By Sergio N. Monteiro

The interface between the matrix and the reinforcing fiber plays an important role in the efficiency by which an applied load is transmitted through the composite structure. The shear stress at the fiber/matrix interface can be associated with this load transference and,consequently,affects the composite strength. In the present work, pullout tests were used to evaluate the interfacial shear stress of curaua fiber in epoxy matrix composites. A small critical length was found for the curaua fiber embedded in epoxy, which corresponds to a relatively weak fiber/matrix bond and lower interfacial strength.

Jan 1, 2009

By J. W. A. Morris

To investigate the use of centrifugal fields in fused salt electrowinning cells, a high temperature rig has been designed, constructed and commissioned. Initially, the cell has been applied to the fused salt electrowinning of zinc. Current efficiencies of 93% have been obtained for inter electrode gaps as small as 8mm for 70mm diameter electrodes rotating at 100rpm. The construction of a semi-rigorous physical model has shown the potential exists to extend the use of centrifugal fields to the electrowinning of light metals.

Jan 1, 1994

By Noritaka Horii, Katsuyoshi Kakinuma, Hiroshi Yamamura

"ZrO2 and Y2O 3-doped ZrO2 gel film were obtained by spin coating of sol from Zr-n-propoxide, n-propanol, acetylacetone, nitric acid, and water on a silica glass as a substrate. ·Dried gel films crystallized to monoclinic, tetragonal, cubic and their mixed phases, depending on the chemical composition of sol, .firing temperature, and coating cycles. ZrO2 films with highly preferential orientation were successfully obtained from a solution containing a large amount of n-propanol. The highly oriented ZrO2 film was found to have high transparency compared with non-oriented 'films. Electrical conductivity of 8 mol% Y2O 3 doped ZrO2 film was also measured.Introduction3 mol% Y2O 3 doped ZrO2, which has a tetragonal symmetry is ·well known to have a strong mechanical property and a high toughness. (1) On the other hand, 8 mol % Y 2O 3-doped ZrO2 is high oxide-ion conducting material and is applied to oxygen sensor, oxygen pump, and solid oxide fuel cell (SOFC). (2) Sol-gel methods using metallic alkoxide are widely applied for synthesizing ceramics such as high-purity fine particles, thin film, and fiber. (3) For ceramics films, many reports have been made on SiO2, (4) TiO2, (5) and PZT. (6) Several case studies have been done on zirconia film based on the sol-gel method, (7) - (11) but very few on preferentially oriented film and on systematic Y zO3 doping. Almost zirconia ceramic· films reported were prepared by means of dip-coating. Kamiya et al. (12) and Ganguli et al (13) converted zirconia into fiber. Sol from Zr alkoxide is usually very unstable, and a stabilizing agent such as glycol or ß-keton is used beforehand (7) (14)."

Jan 1, 2000

By Seshadri Seetharaman, Nurni N. Viswanathan, Haijuan Wang

"In order to make the stainless steel making process efficient and environment friendly, it is essential to minimize the loss of chromium to the slag phase. With a view to investigate the advantages of using CO2 to attain moderate oxygen partial pressures in the oxidant gas during the decarburizations of stainless steel, the present experiments were carried out to understand the oxidation kinetics of Fe-Cr alloys and Fe-V alloy with gas mixtures containing CO2. In the present work, the oxidation behavior of Fe-Cr and Fe-V was examined by thermogravimetric analysis (TGA). Various mixtures of O2 and CO2 were used as the oxidant gas and the oxidation rate was followed by the weight changes as a function of time.The experiments demonstrated that the oxidation rate is independent of temperature at present experimental situation, but has strongly related to the Cr-content of the alloy as well as the oxygen partial pressure in the oxidant gas mixture. The wetting of alumina by the iron drop and the change of the drop shape during the course of the oxidation were investigated by X-ray radiography."

Jan 1, 2010

By Ralph P. Hackl

Bacterial leaching of the Doe Run Company?s cobalt/nickel-containing copper concentrate at low pH (pH 1.0-1.2) and high redox potential (>750 mV vs. SHE) enabled the cobalt and nickel to be preferentially dissolved over copper and iron due to the rapid passivation of the chalcopyrite component. Selective leaching of the cobalt and nickel was achieved with a mesophilic culture comprised mainly of Leptospirillum-like bacteria and Acidithiobacillus thiooxidans. This finding led to the conception of a novel hydrometallurgical process for passivating chalcopyrite and recovering the cobalt and nickel. The bacterial leaching process was tested extensively at the bench and pilot plant scales during 1997-1998. A pilot plant containing four leaching stages processed 30-40 kg/day of chalcopyrite concentrate continuously for 87 days. The cobalt extraction ranged from 75% to 86% during 6- and 8-day retention times respectively, whereas the copper extraction was limited to about 9%

Jan 1, 2003

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 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 B. Willit, J. Martin

"Continued emphasis on water and energy conservation with less operator attention has created a need for more sophisticated cooling tower controls. A joint Betz/ASARCO project has produced a computerized water parameter controller and automated pumpless feed unit. Interfacing the unit via radio modem to the operator control room computer allows real time system status monitoring. Incorporating SPC principles to monitor and regulate all pertinent parameters yielded enhanced water control. This paper described the system design and present the results of a six month trial.BackgroundReducing operating costs and better manpower utilization are two of the largest concerns confronting maintenance managers today. At the ASARCO plant in Amarillo, a trial has been initiated to prove that it is possible to accomplish both of these objectives by using automated cooling tower control. The system is being adapted from a unit that was designed for continuously operating cooling towers in refineries and power plants by Betz Equipment Systems Division, a subsidiary of Betz Laboratories, Inc. The System l3000™ is designed to continually monitor conditions in the cooling system and to provide adjustments to the chemical balance for corrosion and deposition control. At Asarco, the unit was installed on the Rodline cooling system which operates on an intermittent basis.The primary justification for this project is to reduce costs of the five cooling systems in the plant. Current procedures require an operator to make visual checks every two hours on the five cooling towers as well as run lab tests on the water to insure proper treatment levels. This manpower can be better utilized by controlling the towers and collecting all the data available at one central location, in this case, the boiler house."

Jan 1, 1989

By J. Rajek

The novel multi-component, multi-particle, multi-phase precipitation model developed recently is used to predict the precipitation kinetics in complex 9-12% Cr steels investigated within the European COST 522 project. These steels are used for tubes, pipes, casings and rotors in USC (ultra super critical) steam power plants for the 21st century. In the computer simulations, the evolution of the precipitate microstructure is monitored over the entire production heat treatment starting with the casting process, including austenizing, several annealing treatments and in-service conditions. The main interest lies on the concurrent growth and coarsening interaction of different types of precipitates. Keywords: Precipitation kinetics, heat treatment, power plant steels, simulation

Jan 1, 2003

By Patrick R. Taylor

Coatings of TiCIFe have been produced by Reactive Plasma Spraying using ilmenite ore concentrate as the feedstock powder and methane as the reactive gas. A free energy minimization analysis of the ilmenite-methane system is presented. The coatings have been characterized by x-ray diffraction and SEM. The microstructure of the coatings indicates good interparticle cohesion. The composition of the coating is deficient in iron compared to the initial Fe to Ti ratio found in ilmenite.

Jan 1, 1998

By B. C. Jena

Activities of carbon, cobalt and nickel were evaluated in the ternary systems iron-carbon-cobalt and iron-carbon-nickel for the temperature range 1300-1600°C for cobalt and 1300-1700°C for nickel. The carbon activities were determined from the knowledge of activities (1) in the binary system iron-carbon, (2) in the dilute ternary systems and (3) from the knowledge of carbon saturation data. The activities were mathematically expressed with the Taylor series expansion of Wagner's interaction parameter formalism modified to suit concentrated solutions. The cobalt and nickel activities were determined from the knowledge of carbon activities by applying the Gibbs-Schuhmann integration and from cobalt and nickel activities in the binary systems iron-cobalt and iron-nickel. Partial molar enthalpies of mixing were determined based on the temperature behaviour of the activity coefficients.

Jan 1, 1992

By M. M. Kim

As-electrogalvanized coatings of pure Zn, Zn-11% Fe, and Zn-18% Fe coatings were characterized in terms of initial crystal structure and surface morphology. Samples were then subjected to heat treatments simulating the paint bake cycle of automobile manufacturers. Surface morphology changes were correlated with the process variables, and crystallo.graphic changes were interpreted by mapping heat treatment routes on the Fe-Zn phase diagram. The morphology of pure zinc electrogalvanized coatings with heat treatment from platelets to smeared platelets. The zn-11% Fe coating changes with heat treatment from tetrahedral nodules to a mixture of round and tetrahedral nodules, with the Zn-:18% Fe coating always having round nodules. Regarding crystal structure, a critical transformation time can be defined at any selected temperature, below which the crystal structure does not change. This temperature is related to iron content.

Jan 1, 1990

By Muhlis Nezihi Saridede, Burak Birol

"Plastic wastes become a huge problem day after day due to the growth of plastic industry. Hence, plastic wastes are used as a raw material for other industries to eliminate this problem. Polyethylene Terephthalate (PET), which is a commonly used for plastic bottles, may be used as a reductant for iron production because of its C and H content. In this study, composite pellets containing iron ore concentrate, flux and reductant were prepared. Crystallized PET bottles and coke were used as reductant after ground. The prepared pellets were reduced at 1400°C for 30 min. and iron nuggets were produced successfully. Usage of waste PET purely as reductant in composite pellets gives a higher metallization degree and proper carbon content than coke or PET and coke mixture.IntroductionPlastics can be seen everywhere, especially at packaging industry in our common life. The increase of plastic usage ends up with an important problem, the increase of plastic wastes. Many studies have been carried out about usage of plastics as reductant in blast furnace such as Ogaki et al.[1], Heo and Baek [2], Saridede [3], Minoru et al.[4], etc. Besides, Kato et al. [5], Nomura and Kato [ 6] and Rongfang et al. [7] have pointed out the use of plastics in coke ovens regarding to its calorific content. In EAF steelmaking, a mixture of coal/coke and plastics can be used as an energy resource instead of only coal or coke. [8] Also, the usage of PET and PC in self-reducing composite pellets increased the reduction rate. [12]PET (Polyethylene terephthalate ), which is commonly used for soft drink plastic bottles, is an important municipal waste due to its C and H content. Its molecular formula is (C10H8O 4)n. Demir and Dincer showed that PET can be crystallized at 250°C to have the ability to be ground to a size of -100 µm. [11]"

Jan 1, 2011

By R. David Prengaman

During the past several years a new insoluble lead anode has been developed for copper electrowinning. The new anode consists of a rolled lead-calcium-tin alloy sheet attached to a slotted copper bus bar by a soldering process which produces a complete metallurgical bond between bar and sheet. The metallurgical bond greatly reduces the resistance between the bus bar and the lead sheet and the high conductivity does not deteriorate during the life of the anode. The rolled anode thins uniformly and does not suffer preferential grain boundary or internal corrosion commonly seen in cast anodes. The lead-calcium alloy containing a high tin content corrodes slowly because the rolling process produces a uniform, fine grained structure. The wrought product is very strong and ductile; and contains no internal defects, segregation, cracks, or pores which can reduce the life of the anode. Because the anodes corrode uniformly, a high percentage of the anode thickness can be utilized thus extending the life of the wrought anodes. The anode alloy composition which is stable only in wrought form, produces exceptional resistance to passivation during current interruptions. First introduced into liberator cells, the new electrowinning anodes have been specified as the anodes of choice for every new SX-EW tankhouse constructed in the last two years. This paper describes the new anode, its method of construction, service history, and how it differs from present copper electrowinning anodes.

Jan 1, 1987

By Lijuan Li, Zheng Lu, Xin Xia, Qijie Zhai, Qingchun Li

"Pulsed current and pulsed magnetic field have been applied to the bainite transformation of Cr5 steel. Three groups of experiments were conducted. In the first group, ordinary resistance furnace was used for heat treatment. The Cr5 specimens were rapidly heated up to austenitization temperature 940 °C, held for 20 min, air cooled to bainite transformation temperature 350 °C, held for 10, 20, or 40 min and then air cooled to room temperature. The second and the third group shared the same temperature-time curve with that of the first group, but their heat resources came from the Joule heat produced by pulsed current. 1.5 T pulsed magnetic field was exerted on the third group specimens when they were held at 350 °C, but the second group specimens did not undergo the treatment of magnetic field. It was found that both pulsed current and pulsed magnetic field obviously retarded the bainite transformation. The phenomena were discussed in terms ofliterature results.IntroductionApplying pulsed current and pulsed magnetic field technology are very pronnsmg ways to change the microstructure of materials by affecting the phase transformation process. People had found that pulsed current dramatically influences the behaviors of materials, for example, electromigration effect [l], the solidification of metals and alloys [2, 3], electroplasticity [4, 5], crystallization of amorphous alloys [6], healing of metal materials [7] and so on. As to pulsed magnetic field technology, a lot of effort had been spent on grain refinement in solidification of metals [8, 9], recrystallization of cold-worked metals and alloys [10] and Fe-based alloys solid-state phase transformation [11, 12]. Though application of pulsed current and pulsed magnetic field technology have proliferated in recent years, investigation on their effects on solid/solid phase transformation, especially bainite transformation, is lacking. The aim of this paper is to show the effects of pulsed current treatment (C-T) and the combined treatment of pulsed current and pulsed magnetic field (CM-T) on bainite transformation of commercial Cr5 steel"

Jan 1, 2014

By S. Seetharaman

A mathematical model has been developed to evaluate the viscosities of melts at high temperatures. The viscous flow in liquid is described by the equation, {n = Aexp(AG*/RT)} based on the absolute reaction rate theory. The Gibbs energy of activation,{ AG* } is considered to be a function of the temperature as well as the composition of the melt. The model has been applied successfully to various metallic and slag systems from unary to quaternary. On the basis of this model, a relationship has been suggested to relate the Gibbs activation energy of viscosity to the Gibbs energy of mixing in binary metallic melts. The viscosities predicted from available thermodynamic data in the case of a number of binary metallic systems using this correlation show satisfactory agreement with the reported experimental values.

Jan 1, 1994