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By V. Gornitz

The Orphan mine uranium deposit, Grand Canyon, Arizona, is a cylindrical collapse-breccia pipe, 70 to 150 m in diameter and 500 m deep. Pipe fill was derived from the Supai Group, Hermit Shale, and the Coconino Sandstone. Uraninite, with Cu, Fe, Pb, Zn and Ni-Co sulfides is concentrated along the pipe boundary ring fracture (annular ring) and within the central porous sandstone matrix. There is some suggestion of vertical and lateral zonation of U with respect to Cu. Reduction of ferric oxide cement from red beds and recrystallization of carbonate, with formation of kaolinite preceded major ore deposition. Early Ni sulfides, arsenides and disseminated pyrite were followed by massive pyrite, and botryoidal uraninite, which in turn was suc-ceeded by Cu, Zn and Pb sulfides. A second, later generation of uraninite was closely intergrown with hematite and base metal sulfides. Oxidation of primary minerals may have been associated with Tertiary regional uplift. The paragenetic sequence closely resembles that of other Grand Canyon breccia pipes, except for the extensive development of the distinctive uraninite-hematite association. Mineral assemblages at the Orphan suggest possible mixing of the metal-bearing solution(s) with a more oxidized fluid, containing soluble uranyl complexes. Homogenization temperatures of fluid inclusions in calcite (GO-lIO?C) at the Orphan fall within the lower end of the range observed at other breccia pipes.

Jan 1, 1987

By A. Jakobsson

Studies of the rate of interdissolution in oxide systems in the solid state are of importance in materials processing through the powder-metallurgical route. As there is a need for following the rate of the such reactions continuously, a new method based on high temperature X-ray diffraction was developed. Mechanical mixtures of the oxides were placed in a high-temperature X-ray diffraction unit and the changes in the intensity and position of the peaks with highest intensity for both the components were followed as functions of time. A suitable theoretical model has been developed in order to interpret the experimental data and evaluate the diffusion coefficients. The method was applied in the case of the system MgO-NiO. The results obtained are compared with those obtained by another new method, based on solid-state galvanic cell technique with calcia stabilized zirconia electrolyte, developed in the Department of Theoretical Metallurgy. The advantage of the present techniques to monitor the progress of the reaction continuously make them suitable for computer control of such processes.

Jan 1, 1995

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 Pengcheng Li, Wei-Tong Du, Yu Wang, Gang Wen

Carbon dioxide could be utilized as a weak oxidant and a kind of coolant to oxidize elements, meanwhile, helping control the temperature during the converter vanadium extraction process. However, the optimum content of CO2 and the cooling effect of CO2 at low content have not been reported. In this study, experimental research based on the influence of different CO2 contents from 0% to 25% injected to the vanadium-containing hot metal was carried out, as well as contrast experiments of O2-N2 mixed blowing. The results indicated that the optimum content of CO2 was 15%. Under the optimum condition, the oxidation of [C] was the lowest and the oxidation rate of [V] was 96.9%, while the temperature was also lower than the O2-N2 mixed blowing. This paper provide a potential property for utilizing CO2 during the converter vanadium extraction process.

Jan 1, 2016

By C. J. N. Buisman

THIOPAQ technology developed and marketed by PAQUES Bio Systems in Balk, Netherlands, has been successfully used at commercial scale at the Budelco zinc refinery in the Netherlands for the treatment of contaminated groundwater since 1992. In essence, THIOPAQ technology consists of two biological process steps in series: sulfate reduction to hydrogen sulfide (anaerobic) and sulfide oxidation to elemental sulfur (aerobic). The biogenic sulfide produced can be employed for the chemical precipitation of metals in solution either inside the anaerobic reactor or in a separate vessel. Since the solubilities of most metal sulfides are much lower than of their respective hydroxides, considerably lower effluent metal concentrations can be achieved with THIOPAQ systems than in neutralization processes which immobilize metals predominantly by hydrolytic precipitation. In recent years, PAQUES has made significant advances in the design and operation of aerobic and anaerobic bioreactors for metal-sulfur systems. Moreover, the company has increased its technology portfolio to allow the development of more process oriented applications of THIOPAQ technology. A new PAQUES designed plant at Budelco treating sulfatecontaining proceswaters will be started up in 1999. The sulfate reduction is accomplished in a 500 m3 reactor in which hydrogen is used as electron donor. The endproduct, ZnS, is used for Zn and H2S04 production.

Jan 1, 1999

By Fathi Habashi

During the recovery of copper, nickel, zinc, and lead from their sulfide ores, large amounts of sulfur dioxide are generated. A fraction of this gas is captured and transformed into sulfuric acid and liquid SOl and the remainder is emitted to the atmosphere. Numerous proposals were made to solve this problem. Hydrometallurgy offers the only valid solution by which elemental sulfur instead of sulfur dioxide can be produced. Sulfur can be easily stored, transported long distances, or transformed into S02 and H2S04 when desired.

Jan 1, 1996

By R. B. Nourse

The depressed market for Ferrochrome worldwide has forced most producers in this industry to scale down production. Inevitably, many furnaces have been mothballed for prolonged periods, awaiting an upturn in the Ferrochrome market. In contrast, the Platinum industry is experiencing relative stability combined with good prices and they have been looking for cash cows to take advantage of these market conditions. It is, therefore, rather convenient that Platinum and Ferrochrome producers are virtually neighbours in the Bushveld complex of South Afiica, since there is an abundance of spare furnace capacity around (albeit for Ferrochrome). Against this backdrop, Pyromet Technologies (Pty) Ltd, who are currently designing a slag cleaning furnace for Anglo Platinum, was requested to perform pilot scale testwork on a 200kW furnace, in order to establish the suitability to process platinum concentrate and converter slag in a furnace designed for Ferrochrome. This paper provides an overview of the configuration, test conditions, operation and results achieved during the testwork. It also discusses the critical issues, such as refractory consumption, copper cooling and electrical parameters that need to be addressed when converting a Ferrochrome Smelter into a Sulphide Smelter.

Jan 1, 2002

By B. Mishra

Calcium and lithium gallides have been synthesized by powder metallurgy techniques in the stoichiometries that can be used as reduction alloys for the Rocky Flats Plant Salt-Scrub (SS) process. The SS process is performed to recover valuable metals from salts generated in the electrorefining and the molten salt extraction processes. Combustion synthesis has been optimized for variable heating rates up to the reaction ignition temperature and for green densities of the powder compacts in terms of the ignition temperature and the exothermic heating of the product in an effort to develop LiGa and CaGaz alloys. The problems arising from the melting point and density differences of calcium, lithium and gallium have also been studied. The SS alloy compositions were produced by mixing, pressing and sintering the metal-powders. The efficiency of the intermetallic alloy, Ca-17 wt. pct. Ga, as a reductant and the effect of gallium on salt clean- up has been discussed. Measurement of actinide recovery has been studied with cerium as the surrogate for the actinide metal. The development of an alloy for SS reduces a major contaminated waste disposal problem besides recovering the valuable reactive metal.

Jan 1, 1993

By R. I. Rodriguez

Since the 1973 energy crisis, high fuel oil costs have been eroding the economics of the Nicaro and Punta Gorda Plants that employ the Caron Process for laterites processing. Since 1995, Cuban crude oil production has growth dramatically, with progressive utilization in power generation, cement and nickel plants. This paper shows how Nicaro and Punta Gorda plants have been able to shift from expensive Bunker C Fuel Oil to heavy but cheaper Cuban Crude Oil of high Sulfur content and achieve a significant reduction in operating cost. Problems related to the high sulfur content of the Cuban crude oil have demanded extensive investigations of the process chemistry and novelty solutions are proposed, with corresponding changes in process conditions. Innovative options are shown that will allow further cost reductions in the future. Keywords: Cuban Crude Oil, Sulfur, Ammonia.

Jan 1, 2004

By Wang Chen

COREX process is briefly introduced. A static model combining a set of mass and heat balance equations has been developed. Taking the specified inputs from the graphical user interfaces, the model is capable of calculating the consumption of raw materials and fluxes, the volume and composition of the slag and the volume and composition of the generator gas. The model enables the examination of the changes of materials and energy flows induced by the variations of operational parameters and raw materials chemical analysis. The model allows a detailed process analysis and adjustment of the plant operation and can thus be used to improve plant operation.

Jan 1, 2008

By Dale W. Collins

The disposal of arsenic from copper operations possess various health, environmental and processing problems. There are basically two areas of concern. The first being the disposal or treatment of smelter flue dusts and the second the removal of arsenic from refinery electrolytes. A number of treatment options have been proposed including the addition of soluble arsenic wastes to copper heap and dump leaching solutions. This approach will allow arsenic to be reintroduced to the ore via Solvent Extraction (SX) raffinate associated with hydrometallurgical operations. Knowledge of the attenuation behavior and mechanism during leaching is important in determining the long term stability of arsenic and the success of this approach. Parameters, such as uptake capacity, pH, particle size and solution chemistry have been investigated. Arsenic attenuation has been examined using column leaching with experiments employing both continuous flow and pulsed additions of As(V). In the initial stages of leaching, the attenuation of arsenic appears to depend on the pH and iron concentration in the effluent. Arsenic stability in the copper oxide ore has been examined with rinses of progressively lower pH.

Jan 1, 1994

By A. Rojo, N. J. Ramirez, J. E. Salgado

"This work aims to characterize the plastics used in a handgrip located in the car interior body in order to improve its design process and be able to predict its behavior when the part is subjected to impact test involving human casualties.Through stress analyses at high speeds and a video camera set up (front and side view), the reduction of area of specimen was obtained from image analysis, allowing to get the stress-strain real curve of the material.Continuing the characterization process a set of impact test was developed, where standard lzod configurations were used in unnotched specimens. From these tests were gotten displacement curves and absorption energy estimations.The proposed testing procedure allowed the acquisition of force and displacement data through time at various strain rates which are indispensable for the characterization of dynamic events. Using a specimen with a special configuration has shown a more detailed dynamic behavior resulting into more accurate numerical analyses within the design process.IntroductionIn the design process, one of the many analyses which take place is the impact test of the designed part. Nowadays there are many software capable to do these kind of analysis and each industry use the one they think it is convenient for them, but also the selected software has mathematic models that help to find the solution and the simulation of the case of analysis. These are not the only considerations that a company has to take into account, other one is the type of information and data necessary to feed the software. For this study we are going to focus on the acquisition of these data.The mail reason of this work is that generally the supplier gives the card of the material with all the characteristics and information requested by the buyer, but all of that information is acquired by standard methods, but it is inconvenient when the materials are polymers."

Jan 1, 2011

By K. G. Wang, M. E. Glicksman, P. Crawford

"We formulate the mathematical solution to late-stage multi particle diffusion in finite systems. The transition from finite system behavior to that for an infinite system is established. Large-scale simulations are reported regarding the dynamics of phase coarsening. Even in the case of a small volume fraction (Vv = 10-4), the particle size distribution is broader than that for the well-known Lifshitz-Slyozov limit at zero volume fraction. We also report the first simulation studies of extremely low volume fraction, for which corresponding experiments, as well as other simulations, do not exist at present for comparison. However, in the case of moderate volume fractions (Vv = 0.1), the fiucutations in the volumetric growth rate of particles are extracted from our simulations. These simulations provide additional insight into the statistical nature of diffusion interactions, including multiparticle stochastics during microstructural evolution.IntroductionPredicting microstructure evolution in alloys remains one of the cornerstones of materials science. Phase coarsening is a common process in microstrucural evolution that leads to a decrease in the excess total interfacial energy of the system. The system typically consists of separate and identifiable units, or domains, such as second-phase particles distributed in a matrix. During phase coarsening, larger particles grow at the expense of small particles. Over time, this ""competition"" results in an increase in the average size of the particle population, and in a concomitant decrease in the number of particles.Particle size and microstructure of many cast alloys depend on similar coarsening processes. Indeed, properties of these materials, such as strength, toughness, ductility, and electrical conductivity, depend on the material's average particle size and particle size distribution (PSD). Understanding and controlling microstructures in two-phase systems are clearly of widespread technological importance."

Jan 1, 2001

By Sheikh Abdul Rezan, M. N. Ahmad Fauzi, Yong Jing Hui, NORLIA BAHARUN, Noor Izah Shoparwe, Srimala Sreekantan

In this paper, the effect of carbon reductant on carbothermal reduction and nitridation of copper-doped titanium oxide (Cu–TiO ) was investigated.

Mar 1, 2017

By Brian Balmforth

Solvent extraction has been applied successfully to the recovery of a range of metals from a variety of process streams. Particular benefits are derived from the use of new highly selective extractants. These will be exemplified by case studies including the recovery of zinc from sulfate and chloride media using ZENECA's new extractants which show a very high selectivity over iron and the recovery of antimony and bismuth from copper refinery electrolytes using ZENECA's strong and selective extractant DS5834. The conclusions are drawn that solvent extraction is a cost effective technology for metal recovery and recycling, even when used to treat relatively small volume/low concentration process streams, and that it can provide the essential enabling components of a larger system for waste minimisation programmes.

Jan 1, 1996

By Adam Powell

A Cahn-Hilliard phase field model is formulated to describe transport-limited electrochemical reactions coupled with fluid flow in a metal reduction cell. When the reaction is limited by mass transfer of metal ions from the electrolyte to the cathode, the metal-electrolyte interface at the cathode exhibits a Mullins-Sekerka instability, leading to the growth of dendrite-like "streamers" of liquid metal into the electrolyte, which in turn significantly enhance the apparent mass transfer coefficient there. Model results for iron reduction from ferrous oxide in slag show formation of these streamers. Although the double-layer is not included in this model, the related phenomenon of electrocapillarity can be represented by a gradient penalty term which includes the electric potential gradient, such that interfacial energy is a function of the electric field normal to the interface.

Jan 1, 2003

By Bao Xiancheng

Jinlong's copper flash smelting process started up in April 1997. In the early days of production, lots of equipment and process problems were encountered. But, through continuous improvements in equipment and operation, the designed productivity was reached two years later and the smelting operation has been greatly upgraded since then. After more than 4 yew of production, we have made great achievements, such as increasing the flash furnace availability, significant improvements in operation control, optimization of concentrate burner's structure and operation, and smooth operation of the whole smelter. This paper outlines Jinlong's operational achievements made after commissioning, and discusses problems that were encountered and their countermeasures. Operational experience is also summarized

Jan 1, 2002

By Run-boWang, Fan-yi Meng, Jian-Liang Zhang, ZheWang

To elucidate the influence of high Al2O3 content on sinter softening and melting behavior, heating-up reduction test under load was carried out. In addition, microstructure study of sinter bed structure change at a different temperature was also made and the mechanism that the effect of Al2O3 content on sinter softening and melting property was discovered. SEM results showed that the increase of Al2O3 content favored the formation of Al2O3-rich slag phase, such as the eutectic (2CaO·SiO2-2CaO·Al2O3·SiO2-FeO) and gehlenite (2CaO·Al2O3·SiO2), resulting in the decrease of sinter Ts temperature. Further, high Al2O3 content improved the concentration of metallic iron and lowered the dripping temperature due to the decrease of slag liquidus temperature and viscosity. At a fixed basicity, it was indicated that there was a relationship between Al2O3 content and sinter softening-melting property. Based on the results, counter strategies to cope with the adverse effect of high Al2O3 content on the cohesive zone property were also proposed. It could provide guidance for the blast furnace operation of sinter with high Al2O3 content.

Jan 1, 2015

By J. M. Rapkoch

In late October 1996, an acid plant at a major U.S. copper smelter was faced with unexpected and rapidly increasing pressure drop across the gas cooling tower in the acid plant, indicating a build-up on the packing. This threatened to halt operations if not resolved. Earlier that month, a smaller vessel in the acid plant was found to be completely plugged with lead sulfate. It was feared that a similar fate awaited the gas cooling tower unless the scale build-up was stopped. Although lead sulfate is present in most copper smelter acid plants, this accumulation was unusually severe. An investigation was launched to find the source of the lead, determine how lead is transported to the gas cooling tower, recommend operating practices to prevent such severe scaling, and seek ways to recycle the lead value in the scale covered polypropylene packing. Late in the investigation it was learned that the lead originated from an improperly executed recycling program.

Jan 1, 2000

By James M. Lockwood

"Eureka Technology has developed and patented a technology for the recycling of EAFD. Through this process all constituents of the material become salable commodities or are returned to the steel making process. In transforming the EAFD ""waste"" stream into a ""process"" stream the Steelmaker eliminates potential liabilities and the uncertain future of current processes while further reinforcing its role as a recycler. This is a cost-effective and energy efficient technology that combines hydrometallurgic and electrolytic processes resulting in the recovery of salable metals. For instance, unlike pyrometallurgic processes, zinc is recovered in metallic form and no elements are volatilized. This on-site operation also eliminates expensive transportation costs. In summary this technology reduces the cost of dealing with EAFD by recycling material currently being landfilled.IntroductionWorld crude steel production reached a new record level in 2007 - 1.34 billion tons of which 31% was produced by EAF steel makers [1]. This resulted in the generation of over 6 million tons of EAFD. This steel byproduct contains significant amounts of lead, cadmium and other hazardous metals. In the United States the Environmental Protection Agency (EPA) has designated EAFD a hazardous waste (EPA waste code K061). With over 50% of steel production in the US coming from EAF steel making this byproduct represents the single largest source of solid hazardous waste generated."

Jan 1, 2008