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By William E. Frazier

The presence of minute amounts of sulfur (10ppm) in nickel-base superalloys has been associated with reduced oxidation resistance and the premature spallation of protective coatings. Removal of sulfur by annealing these alloys in a hydrogen atmosphere has been successfully attempted by several researchers. This paper examines the fundamental thermodynamics and kinetics governing hydrogen desulfurization of elemental nickel. Limiting conditions for successful desulfurization are delineated. Assuming that the diffusion of sulfur is the rate limiting process of desulfurization, the effectiveness as well as time associated with hydrogen desulfurization is explored.

Jan 1, 1994

By C. J. Malek

The CONTOP® smelting cyclone technology is a large-scale and time-proven method which in combination with other technologies (grinding, drying, pyrolysis, etc.) provides for a cost- efficient and ecological disposal of a wide range of waste materials from industry and households. In this report the basic principle of smelting cyclone technology will be explained first. Subsequently, the paper will discuss substantial concepts for the recovery of various remainders.

Jan 1, 1996

By Hsing Kuang Lin

Ferric chloride leaching w.as applied to a complex sulfide ore from Tok, Alaska to dissolve zinc, lead, silver and copper. Gold in the leaching residue, as well as in the ore, is found to be refractory to the conventional cyanidation process. Roasting, pressure oxidation and elemental sulfur removal followed by cyanidation were tested to improve gold dissolution. Also tested were thiourea leaching and high-pressure cyanidation. The readsorption of dissolved gold by carbonaceous matter in the chloride leaching residue was analyzed. Based on the experimental results, factors causing difficulty of gold dissolution from the leaching residue are discussed.

Jan 1, 1989

By R. Leiby

Prior to March 1992, the only component of the lead acid battery that was not recycled by East Penn Manufacturing Company was the sulfuric acid electrolyte. This acid was unusable in new batteries because the iron level was found to exceed new product specifications. The development of a liquid ion exchange process to remove the iron from the acid allows East Penn to currently recover over three million gallons of sulfuric acid annually. The process is based upon the use of an iron selective liquid ion exchange material or solvent to extract iron from the sulfuric acid electrolyte followed by regeneration of the solvent. Equilibrium and kinetic data for the extraction and regeneration steps were collected in order to scale up the process to commercial scale. An electrochemical process for the treatment of the acid used in the regeneration step was, also developed which significantly reduces the volume of strip acid required in the process.

Jan 1, 1995

By José Carlos Abreu

This work presents a kinetics study covering the effects of temperature over the reduction rates of a carbon composite briquette, aiming its use as burden in some of the new alternate ironmaking technologies, such as the Tecnored process. It is reported that increases in the temperature increases the reaction rate. Additionally, the morphology of the iron phase generated during the reduction of these briquettes is presented. It was possible to verify that three types of iron morphology occurred during the process: an external, dense and continuous iron layer, the presence of iron globules at the center of the briquettes and whiskers at the briquette's core. The measurement of the carbon content on the globules and the external iron layer is also presented.

Jan 1, 2003

By B. Farouk, D. Apelian

"A numerical model has been developed to predict the temperature history of particles injected in a low pressure d.c. plasma jet. The temperature and velocity fields of the plasma jet are predicted as a free jet by solving the parabolized compressible Navier-Stokes equations using a spatial marching scheme. Particle trojectories and heat transfer characteristics are calculated using the predicted plasma jet temperature and velocity fields. Correction factors have been introduced to take into account non-continuum effects encountered in the low pressure environment. The plasma jet profiles as well as the particle/plasma interactions under different jet pressure ratios (from underexpanded to overexpanded) have been investigated.I. IntroductionIn the plasma spraying process a d.c. plasma jet is used as a heat source to melt and accelerate powder particles which subsequently impinge and solidify on a given substrate. During low pressure plasma deposition (LPPD) prooess, the plasma jet is expanded into a low pressure environment (40-80 Corr) which results in high plasma jet velocities with Mach numbers ranging from 2 to 3. Previous efforts to predict heat transfer and fluid flow in plasmas have made use of incompressible flow formulation employing turbulence models [1-3] for atmospheric plasma spraying. However, these theoretical calculations have been limited to the subsonic flow regime; hence, the compressibility effects and viscous heat dissipation were neglected. In the LPPD process, the plasma jet is operated at the supersonic flow regime, therefore, the compressibility effects and viscous heat dissipation are no longer negligible. This is the main motivation of this work.In addition, production of high quality dense deposits requires that a large fraction of the injected particles be in a molten state when they impact the substrate. An additional motivation for this work is that it is important to understand the plasma/particle heat and momentum transfer since these phenomena dictate both the particle thermal history and particle trajectory.Early computational works in supersonic nozzle field flow [4,5,6] consisted of patching methods that divided the flow field into an invisoid free stream and a viscous boundary and. mixing layers. Each was analyzed independently and coupled through appropriate boundary conditions. Later schemes [7,8] involved solving time-dependent, compressible Navier-Stokes equations over the entire computational domain. These schemes show a great promise in predicting flows with complex structure, and where the viscous effects became prevalent."

Jan 1, 1986

By Nicolas Reynier

The separation of radionuclide during rare earth element (REE) production is an important requirement for developing the Canadian REE mining industry. Separation of actinides from REE is often a large concern in the rare earth industry because of the need to manage the radioactive nuclides. A patented process developed for actinides extraction from radioactive wastes was applied to REE ore. Objectives were to optimize the process for REE leaching from ore, and separate radioactive impurities from sulphuric and nitric liquor by ion exchange (IX). Ore leaching was optimized using a surface response plan to ensure statistical significance. In optimized conditions, solubilization yields ranged from 90–95% for Th, 60–75% for U, 48–55% for LREE, and 59–75% for HREE in sulphuric and nitric media. Both media were compared for radionuclide removal from rich REE-bearing mineral liquor by IX. Actinides separation ranged from 92–97% for Th and 69–96% for U in sulphuric and nitric media.

By Anupam Madhukar

The essence of an atomistic unified kinetic model of strained thin film growth and defect initiation is presented along with a comparison of its consequences obtained from computer simulations with experiments. Within the competing kinetics of a strain dependent activated incorporation of atoms and an asymmetry between upwards and downwards inter-layer migration, the model provides a consistent description of 2D versus 3D morphology evolution accompanied by the appearance of surface vacancies and steps at no energy cost. The correlated migration of these precursor defects offers an atomistic mechanism for the emergence of surface half-loops from the growth front (thus accounting for configurational and thermal entropy) governed by activation energies closer to their correlated motion under the evolving strain fields and thus substantially less than those calculated with respect to the perfect crystal as the reference state. The essential mechano-chemical nature of the problem is compared and contrasted with the historical literature of such phenomenon as precipitation hardening and sintering in metallic and ceramic composites.

Jan 1, 1994

By Muammer Kaya, Sait Kursunoglu

"The aim of this study was to investigate the effectiveness of ascorbic (C6H8O6) / oxalic (C2H2O4) acid as a reductant for the simultaneous recovery of zinc and manganese from a spent and mixed zinc-carbon and alkaline battery powder in sulphuric acid leaching. The effects of sulfuric acid concentration, ascorbic/oxalic acid dosages, reaction temperature and leaching time on the zinc and manganese dissolutions were investigated according to 2k full factorial experimental design; then, a simple optimization study was carried out for the best reductant. The optimum reductive acid leaching conditions were determined at 3 hours leaching time, 70°C leaching temperature, 0.5M sulfuric acid concentration, 13 g/L ascorbic acid dosage, 1/20 g/mL solid/liquid ratio and 200 rpm stirring speed. Under these conditions, the dissolution efficiencies were 99.9% for Zn and 99.3% for Mn. When our results were compared with the previous results, our findings were better than previous studies.In addition, the manganese dissolution kinetics was undertaken, and the activation energy was found to be 7.04 kJ/mol. Selective precipitations of Zn and Mn from acid solutions were carried out using NaOH and KOH. Using 3M NaOH as precipitating agent at room temperature and at pH 8; 95.4% of Zn and at pH 10; 93.7% of Mn were precipitated from the leaching solution. Under the same conditions, using 3 M KOH at pH 8; 91.6% of Zn and at pH 10, 96.4% of Mn were precipitated. Based on the experimental results obtained, an appropriate flow sheet was proposed to recover zinc and manganese."

Jan 1, 2012

By V. P. Keran

The lead and copper smelting processes employed by Mount Isa Mines Limited, Mount Isa, Australia, are used to illustrate an operating viewpoint of some problems and solutions encountered in existing commercial sulphide smelters. The smelting processes discussed; include updraught sintering, blast furnace and reverberatory smelting, and converting. Selected examples are given of methods implemented, and options available, to improve the productivity and efficiency of conventional smelting processes.

Jan 1, 1983

By J. Gartelmann, B. Zaslavsky, Y. Vojta, D. J. Chaiko, W. Mego, A. N. Rollins

"Aqueous biphasic extraction (ABE) processes offer the potential for low-cost, highly selective separations. This countercurrent extraction technique involves selective partitioning of either dissolved solutes or ultrafine particulates between two immiscible aqueous phases. The extraction systems that we have studied are generated by combining an aqueous salt solution with an aqueous polymer solution.We have examined a wide range of applications for ABE, including the treatment of solid and liquid nuclear wastes, decontamination of soils, and processing of mineral ores. We have also conducted fundamental studies of solution microstructure using small angle neutron scattering (SANS). In this chapter we review the physicochemical fundamentals of aqueous biphase formation and discuss the development and scaleup of ABE processes for environmental remediation.IntroductionAqueous biphasic extraction (ABE) is a highly adaptable separation technique that can be used in a wide range of applications. We have been evaluating various types of ABE systems for possible applications in the treatment of solid radioactive wastes (1,2), liquid nuclear wastes (3,4), and contaminated soils (5-7), and in the removal of organics from aqueous salt solutions (8). We have also conducted fundamental studies of the solution microstructure of ABE systems using small angle neutron scattering (SANS) (9).The extraction systems are generated by combining an aqueous salt solution and an aqueous polymer solution. This produces two distinct liquid layers that are as immiscible as oil and water, yet each liquid layer contains at least 70 to 80 wt % water. The biphasic systems that we have been working with consist of immiscible polyethylene glycol (PEG) and salt solutions. Some inorganic salts that promote biphase formation with PEG solutions include the sodium/potassium salts of sulfate, carbonate, phosphate, and hydroxide (10)."

Jan 1, 1996

By José Carlos Abreu

This work presents a kinetics study covering the effects of temperature over the reduction rates of a carbon composite briquette, aiming its use as burden in some of the new alternate ironmaking technologies, such as the Tecnored process. It is reported that increases in the temperature increases the reaction rate. Additionally, the morphology of the iron phase generated during the reduction of these briquettes is presented. It was possible to verify that three types of iron morphology occurred during the process: an external, dense and continuous iron layer, the presence of iron globules at the center of the briquettes and whiskers at the briquette's core. The measurement of the carbon content on the globules and the external iron layer is also presented

Jan 1, 2003

By Makoto Ohtsuka

The ternary Ni2MnGa intermetallic compound is an intelligent material which has both a ferromagnetic property and a shape memory effect (SMB), The use of the shape memory alloy films for an actuator of micro-machines is very attractive because of its large recovery force, The purpose of the present study is to investigate the effects of fabrication conditions and to clarify the relationships between these properties and fabrication conditions of the Ni-Mn-Ga films, The Ni-Mn-Ga films with a thickness of nearly 5 um were deposited with a radio-frequency magnetron sputtering apparatus using a NisoMn2sGa25 or Nis2Mn24Ga24 target. They were heat-treated at various temperatures between 873 and 1273 K for homogenization and ordering and then cooled in a furnace, The composition of the films depended on the sputtering power. The as-deposited films were crystalline and had columnar grains, After the heat treatment the grains widened and the grain boundary became indistinct with the increasing heat treatment temperature, The martcnsitie transformation temperature of the heat-treated films increased with increasing nickel content. Furthermore the effect of plastic deformation and constraint aging on SME is also investigated, After plastic deformation, the two-way SME was shown through the martensitie transformation and its reversion, The intensity of X-ray diffraction peaks from stress-induced martensitie phase was found, The constraint-aged films also showed the two-way 5MB by thermal cycling,

Jan 1, 2003

By J. K. Brimacombe

Plant trials have been conducted at the Tacoma Smelter of ASARCO to assess the effect on tuyere blockage and refractory erosion at the tuyere line, of increasing the injection pressure of air into a Peirce-Smith con¬verter. Four tuyeres each having an ID of 19.1 mm (3/4 in) were installed toward one end of the tuyere line of the No. 4 Converter. Air and oxygen-enriched air were injected at 414 kPag (60 psig) through these tuyeres and at the usual 83 kPag (12 psig) through the remainder of the tuyeres in an otherwise normal converter campaign. The test campaign consisted of 88 charges and lasted for 89 days. During this period, punching of the high-pressure tuyeres was found to-be unnecessary; and when, as a precaution, the tuyeres were cleaned by hand at the end of a charge, they were always open. Also it was observed that the flow of high-pressure air remained constant. Accretion formation around the tip of the high-pressure tuyeres varied from charge to charge and was influenced by the matte grade and the level of oxygen enrichment.

Jan 1, 1983

By K. Adham

For use in many existing and emerging applications, the purification of natural graphite is required to achieve +99.9% carbon content with minimum metallic impurities. Currently, the hydrofluoric acid process is used, which carries certain environmental and workplace health and safety impacts. While thermal purification of graphite at temperatures over 2500 °C is a known alternative, such high-temperature furnaces are expensive to build and operate. Using chlorine at lower temperatures to purify graphite is also known and patented, but is currently limited to treating solid synthetic graphite shapes in small-scale batch furnaces. Chlorine treatment of natural flake graphite resources can be used commercially, if certain drawbacks are addressed through process improvements that can be helped with the use of fluidized bed reactor technology.

By Francis C. Furman

Microscopic evidence indicates that the high sinterability of certain commercial dolomites is tied to specific dolomite textural characteristics. This study encompasses detailed characterization of the unprocessed dolomite and sintering doloma results. The chemical and mineralogical compositions, insoluble residue, chemistry homogeneity, crystal size, primary carbonate texture, secondary dolomite texture, deformation structure, porosity type, porosity, and density of the raw dolomite were observed. These characteristics are compared with sintering trials of <74um powder-compacts samples in which holding times were varied. The evolution of the dolomite characteristics are reviewed and related to the final sintered doloma characteristics. The critical characteristics of a single-stage sintering brick dolomite are the following: 1) primary oolitic texture, 2) dolomite purity, 3) dolomite stoichiometry 4) minimal impurities, less than 1 weight {%} Fe2O3 Al2O3 and SiO2, 5) chemical homogeneity, 6) high density, 7) very low porosity, S) very coarse homogeneous crystallinity, 9) nonplanar dolomite texture, 10) abundant strain related slip microdeformation structures, 11) minimal subsequent alteration. Even with grinding to <74um the nonplanar dolomite texture and slip deformation still have a major effect on doloma sintered density. The three newly identified characteristics of single-stage sintered refractory brick dolomite are their primary oolitic texture, secondary nonplanar texture and abundance of stress related microdeformation structures. The primary oolitic texture reflects a homogeneous pure carbonate with respect to chemistry and crystal size secondary nonplanar texture produces crystals with large surface area to volume ratio. Stress related slip deformation moves CO, groups in to the same site of another CO, group but different orientation which is very unstable. All of these characteristics may facilitate the formation of higher density dolorna sinters.

Jan 1, 1995

By L. R. Verney

About 75% of the market economy countries&apos;s supply of cobalt is produced in Central Africa by Zafre and Zambia. Zafre alone accounts for more than 55% and has the resources and capacity to increase output significantly at any time so its dominant position is unlikely to be challenged in the foreseeable future. Other producers from domestic resources are Canada, Australia and South Africa; and Cuba, probably the most important producer outside of the Market Economy countries. Belgium, Norway, France, Japan and Finland produce cobalt from imported materials. While there are "cobalt ores", inMorocco, USA, Canada and the USSR, the mineralisation is complex and cobalt extraction is costly. In ZaPre and Zambia cobalt is a by-product of copper; in Canada, Australia, France, and Cuba it is a by-product of nickel; and in South Africa it is a by-product from the production of Platinum Group Metals. Thus the levels of cobalt production are inevitably related to the production of other primary metals. While some cobalt is produced by predominantly pyrometallurgical methods most of the world&apos;s cobalt is produced hydrometallurgically. The existence of large hydro-electric power plants and the mineralogy of the copper and cobalt concentrates encouraged research and development in Zafre of the recovery of copper and cobalt by electrowinning from sulfate solutions; much pioneering work was carried out, which lead to construction of the two largest copperlcobalt hydrometallurgical plants in the world, at Shituru and Luilu. Similar systems were adopted in Zambia. In Canada high pressure hydrometallurgical processes based on the sulfate system were developed and adopted in Australia, the Philippines, Finland and South Africa. Meanwhile developments in chloride hydrometallurgical extraction of nickel and cobalt lead to its use in the extraction of cobalt in Norway, France and Japan.

Jan 1, 1988

By Young-Sool Jin, Heung Nam Han, Hong Joon Kim, Jae Kon Lee

A mathematical model was developed considering non-symmetric cooling' and stress distribution in both thickness and width direction of strip on a run-out table of hot strip mill. In order to solve a transient heat transfer equation including the heat evolved from phase transformation, a finite element method coupled with thermodynamic and kinetic analyses was applied. The heat capacity of each phase and heat evolution due to phase transformation were obtained from the thermodynamic analysis of the Fe-C-Mn-Si system based on a sub lattice model. The phase transformation kinetics of the steels was derived by using an inverse additivity technique with continuous cooling experiments. Heat transfer coefficients of strips on the run-out table were, by applying an inverse method, determined from the actual mill data under various cooling conditions. As for the stress analysis, the density change of strip due to cooling and phase transformation, and the transformation superplasticity were considered. A 90nstitutive equation for the transformation superplasticity, which is related to the phase transformation kinetics and the internal stress due to the density change of strip, was applied. A finite element method was adopted to calculate the deformation behaviour of strip on a run-out table of hot strip mill. Using the models, the temperature-phase-deformation history and distribution of a strip on the run-outtable was calculated.

Jan 1, 2001

By Sergey Shabala

Green leaf tissues convert solar energy into the energy of chemical bonds of sugar molecules during the process of photosynthesis. The efficiency of this conversion can be much higher than efficiency of any of the currently known silicon-based solar panels. Importantly, vast amounts of CO2 are assimilated during this process. The efficiency of photosynthesis is critically dependent on the availability of a large number of nutrients, among which metal cations such as K, Ca, Mg, Cu, Zn, Fe, Mn, and Ni play a key role. In this paper I summarize basic requirements and major functions for each of these essential nutrients in plant photosynthesis, both at the whole-plant and molecular level. I will talk about how these requirements may be affected by the global climate trends and discuss the prospects of creating artificial photosynthetic “bioreactors” for efficient energy conversion and CO2 assimilation.

Jan 1, 2009

By M. Pakala, Z. Fan, Ray Y. Lin

Deposition of hard chromium coatings using electrodeposition is accompanied by emission of hexavalent chromium mists which is a carcinogenic. Hence alternative chromium deposition technologies are being investigated. Sputter deposition is a strong candidate to economically deposit hard chromium coatings in an environmentally friendly way. Chromium coatings of 2-3 µ m thickness were deposited on plain carbon steel coupons using RF magnetron sputter deposition. Depositions were carried out with 0 to 22 vol% nitrogen in the plasma. Structure of the coatings was studied using x-ray diffraction analysis With increasing nitrogen contents, formation of the two nitride phases was observed. The pure chromium phase was detected in coatings with up to 7% nitrogen in the sputtering gas. The solid solution of nitrogen in the pure Cr phase coating was identified by shifts of Cr x-ray diffraction peaks to higher d-spacing. The microhardness of the coatings deposited at a substrate temperature of 200°C showed an increase in hardness with increasing nitrogen content from 600 kgf/mm2 (5.9 GPa) at 0% nitrogen to I250 kgf/mm2 (I2.25 GPa) at 9.5 % nitrogen and a subsequent decrease in hardness to I 100 kgf/mm2 (11 GPa) beyond 9.5 % nitrogen in the sputtering gas. This corresponds to the formation of the hard Cr2N phase, at 9.5 % nitrogen, and CrN phase, at I5.7 % nitrogen. The reported bulk hardness values of Cr2N and CrN are I600 kgf/mm2 (I5.7 GPa) and I 100 kgf/mm2 (11 GPa) respectively. For pure Cr phase coatings, there is a slight increase in hardness for coatings deposited at 7. I % nitrogen from that without nitrogen in the sputtering gas. This could possibly result from the solid solution strengthening of the Cr lattice by nitrogen. For films deposited at 200°C, phases of the deposited films seem to be the overwhelming factor in controlling the microhardness.

Jan 1, 1998