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By Alexandre Monteiro

Alumina precursor powders can be precipitated from aqueous solutions, using hydrothermal decomposition of urea to deliver base homogeneously to the system. Primary particles agglomerate early in the process, generating a wide size distribution. The presence of a polymeric surfactant such as polyacrylate can suppress or delay agglomeration, reducing particle size and narrowing the size distribution. The stabilization of commercially available a-Alp03 powder with polyacrylate was studied, investigating the effects of polyacrylate molecular weight, ionic strength and temperature. The effect of aluminum concentration, polyacrylate molecular weight and urea concentration on the precipitation of alumina precursors in a sulfate- urea system in the presence of polyacrylate/polyacrylic acid was then studied. The hydrolysis kinetics were followed, and particle sizes were determined. Precipitates were further characterized using energy dispersive spectroscopy. The particle characteristics are discussed in terms of the process conditions.

Jan 1, 1994

By A. De, J. S. Zuback, T. Mukherjee, T. DebRoy

For successful commercial applications of additive manufacturing, metallic parts need to be defect free, structurally sound and reliable. However, additively manufactured metallic parts are susceptible to distortion, lack of fusion defects and compositional changes. Methods to measure susceptibilities of various alloys to these defects are needed but not currently available. Here we show that the necessary theories can be developed based on a well-tested numerical heat transfer and fluid flow model and decades of research in the field of welding. The proposed theories are validated with experimental results reported in the literature.

Jan 1, 2016

By F. M. Nakla

Various methods of Applied Mineralogy were used for determining the nature and composition of products yielded by flotation tests for Maghara coal beneficiation. Coal samples obtained from the Sa fa mine in Northern Sinai, Egypt, were crushed, sieved, &apos;and <32 mesh size fraction was cleaned by froth flotation. Experiments were conducted to determine the effect of certain parameters on beneficiation of Maghara coal by flotation. The investigated factors included nature of frothing and/or collecting reagents, pH value of the medium, particle size distribution in the head sample, and pulp density of the coal slurry. The quality of head samples, coal concentrates, and tailing products were determined by chemical analysis, microscopic study, x-ray diffraction analysis, and occasionally by infrared (IR) absorption spectroscopy.

Jan 1, 1989

By Donna M. Noel

Bacterial strains have been cultivated from solids previously exposed to cyanide that will tolerate 300 ppm sodium cyanide under anaerobic conditions. In selected solid samples, these bacteria have been shown to reduce the level of cyanide from approximately 300 ppm to essentially zero in about 50 days under anaerobic conditions. Various media were investigated, and the nutrients providing maximal growth were ?established .. Degradation of cyanide in sterilized solids was determined for comparison with degradation obtained in bioactive solids. All experiments were conducted at ambient temperature and initial pH of approximately 10.5.

Jan 1, 1991

By Geza Kisvarsanyi

Ore deposits composed of enargite, tennantite, gold, and pyrite have been mined in volcanic rocks of Oligocene age (35 m.y.) at Recsk, Hungary. Vertical and horizontal zoning of the alunitic-argillic alteration and of the ore minerals led to the concept of an intrusive heat source at depth. Subse-quent drilling disclosed a series of ore deposits in a zoned pattern in and around a stock, separated by a barren gap of 1000 meters from the shallow ore. The ore system is in a intracaldera horst-graben structure, formed by collapse and intrusion in a microplate subduction. volcanic-arc tectonic environment.

Jan 1, 1987

By A. P. Paiva

Although the advantages of Solvent Extraction for separation/purification of relatively concentrated solutions are well known in Extractive Metallurgy, its use for the recovery of elements present in low levels only recently has been discussed, with particular attention devoted to precious metals. In this work, the extraction behaviour of Cyanex 471X towards silver, from an acidic chloride medium is reported, the extraction and stripping isotherms and related kinetic features analysed. Results on the selectivity of silver extraction against high contents of iron, copper and lead are discussed. Phosphine sulphide extractants are generally associated with solvation mechanisms: analysis of the extraction pathways along with the possibility of reaching a suitable loading in the organic phase are also presented.

Jan 1, 1993

By R. K. Mehta

Microorganisms have been increasingly used in applications such as-metal solubillzation, precipitation and recently being used as flocculants. Optimal control and on-line monitoring of these processes occurring in microbial reactors are of extensive interest but often difficult because of the unavailability of a mechanistic model of the process and on-line direct sensors. In this paper a dynamic populatlon balance model of microbial desulfurization will be presented. The influence of certain physical and biological parameters on the leaching rate will be illustrated via computer simulations and an extended continuous-discrete Kalman filter will be Implemented for estimation of unknown states.

Jan 1, 1991

By G. Coryell, E. Brack

"Remaining competitive in today's metal markets requires that copper smelters utilize the latest technology offered in process control, data acquisition, and process optimization. State-of-the-art tools like minicomputers, personal computers, and microprocessor based controllers provide real time process information that assist in making proper adjustments to the overall control strategy of an operating plant. The database accumulated by such systems broaden process knowledge, thereby reducing costly errors and plant downtime.IntroductionThe ASARCO Hayden Plant is located approximately 80 miles southeast of Phoenix, Arizona. The plant was commissioned in 1912 for the purpose of smelting copper concentrates from the surrounding mining district. Copper was produced for many years using calcining, reverberatory smelting and copper converting techniques. With the stricter environmental controls of the 1970's, the smelter experienced substantial declines in efficiency and productivity. It became necessary to identify and install a new smelting technology to maintain the viability of the Hayden plant.In 1980, after evaluating several smelting techniques, ASARCO management selected flash smelting as developed by International Nickel Company (INCO). One hundred and thirty-two million dollars was allocated for the project and construction began in 1982. Construction was completed and the new plant came on line in November of 1983."

Jan 1, 1989

By Paykan Safe

Computational Fluid Dynamic (CFD) modeling provides a powerful tool to assist with the design of ventilation and fume control systems in smelters and other high temperature metallurgical facilities. For this paper, this tool has been used to analyze the off-gas flow patterns exiting the mouth of a Peirce-Smith converter into a water-cooled hood and drop out box. The effects of various process and physical plant design parameters on process gas and fume capture and potential build up on the converter hoods was examined, and the optimum design and operating parameters were determined.

Jan 1, 2000

By A. Van den Steen

In the early fifties Professor Breckpot of the Louvain University in Belgium in collaboration with the Research Laboratory of Metallurgie Hoboken, discovered the possibility to separate nickel from cobalt sulfate solutions by a nickel sulfide depolarized cementation. This reaction, completed later with a zinc precipitation, was developed into purification processes for the Shituru and Luilu Gécamines cobalt plants in Zaíre. Due to increasing demand for higher quality products and the necessity of lowering the production costs, more laboratory and pilot plant investigations concerning the key parameters for the nickel and zinc sulfides precipitation were under- taken. Especially the relative stabilities of cobalt, nickel and zinc sulfides, precipitated with elemental sulfur or sodium hydrosulfide, were examined in relatlon with the pH and with the redox potential. These investigations have led to better plant practice and new development possibilities. The valorisation of the precipitated sulfides has also been considered.

Jan 1, 1988

By Yutaka Yasuda

The particle dispersion phenomena in a turbulent gas jet of the flash smelting process has been investigated. The particle number density in a non- reacting jet was measured experimentally by taking photographs of the particles in flight and counting them using the image analysis. Numerical computations were also performed using a mathematical model for a turbulent particle laden gas jet The experimental particle number density data were then compared with the predicted results of the model. Good agreement was obtained between the experimental and predicted data. The effects of the parameters such as the injector design, particle loading and air flow rate are discussed. Optimization of the concentrate burner design can be achieved with the help of experimental and theoretical simulation as performed in this work.

Jan 1, 1994

By Jun Li

Several metal sulfides were examined in-situ by Raman spectroscopy before and after anodic oxidation. Results obtained for chalcocite, chalcopyrite, covellite, galena, pyrrhotite and pyrite electrodes are presented. Under appropriate conditions, sulfur was detected after a potential was applied to the mineral electrodes for a threshold period of time. For all the minerals, application of a negative potential on the oxidized mineral reduced the surface product and the sulfur peaks disappeared from the observed spectra. For those minerals containing sulfur as S< in the crystal lattice, polysulfides were identified as oxidation intennediates.

Jan 1, 1993

By Robert M. Leary

The Kennecott Utah Copper smelter operates two Outokumpu flash furnaces: a smelting furnace for production of high-grade matte and a converting furnace for production of blister copper. Flash furnaces typically possess several characteristic features that must be considered in process control development such as long lag times associated with settler volume, non-linear input and output responses, large process gains, and unmeasured disturbances. Additionally, the Kennecott smelter possesses certain unique characteristics which must be considered such as single mine concentrate source, limited concentrate blending capacity, and feed preparation facilities that inevitably cause significant lags between furnace control parameters and manipulated set points. In order to improve furnace control and on-line time, a process control system was developed to address these issues. The feed forward control module provides predictive control and operates in response to furnace feed input changes. The feed back control module provides responsive control and is based on furnace output deviations. To provide regular feed back information to the control room supervisors, new sampling methods were developed which provide the operators with molten metal and bulk material samples at regular intervals to provide information for control. The control system was implemented on the Flash Converting Furnace in May 1999 and on the Flash Smelting Furnace in August 1999.

Jan 1, 2000

By Yonghua Li, Fanling Meng, Weitao Zheng, Xiaodong Wang

The NiTi thin films were deposited onto copper substrates by magnetron sputtering. Tensile tests were carried out on CSS-44100 electron universal test-machine. X-ray diffraction profile Fourier analysis method has been used to study the mechanical properties of deformation NiTi thin films. The surface micrographs of the NiTi thin film were obtained using scanning electron microscopy (SEM). It has been found that the dislocation density and the deformation storage energy density increased with elongation increased. Microhardness was calculated from the dislocation data. The results showed that the microhardness values were not in a good agreement between calculated values and measured values. The oxide layer on the surface of NiTi thin film affects the measured values of microhardness. The Vickers hardness measured values are larger than the calculated values. The experimental results showed that a series of parallel cracks grew in a concerted fashion across the thin film and the cracks were equally spaced.

Jan 1, 2015

By R. P. King

The central idea presented in this paper is straight forward. Some fairly obscure mathematical techniques are presented from the fields of integral geometry and stereology and these techniques are shown to provide workable quantitative relationships from which the liberation spectrum of an ore after comminution can be determined. The experimental data that is required can be obtained very accurately and conveniently by image analysis of polished sections of the original ore. This quantitative mineralogical analysis provides a bridge that can link the worlds of the mineralogist and the mineral process engineer. This paper has been written to introduce this quantitative approach to a wider audience in the hope that the approach will be used more widely and that the basic linear intercept analysis data will be measured for a wider range of mineralogical textures. This could lead to a more comprehensive characterization of typical mineral ores that will be of considerable use in practical mineral processing.

Jan 1, 1991

By Neeraj Saxena, Madhu Huggahalli, Jerry Bednarski, Ken Grieshaber, David Stoffel

"The use of oxy-fuel burners in secondary aluminum melting applications offers several advantages over air-fuel burners including reduced fuel consumption, faster charge to tap times and lower NOx emissions. Their successful, safe and economical use in a furnace depends on several factors and considerations such as burner and flue placement, metal circulation, charge practices and the type of refractory used in the furnace.These factors required in the successful conversion of furnaces from air-fuel to oxy-fuel based burners are discussed in this paper. Critical parameters are identified and examined using computational fluid dynamics (CFD) simulations. Parameters are estimated via laboratory testing and validated through trials performed at commercial installations. Guidelines and a simplified approach to estimate a priori the economic impact of converting from air-fuel to oxy-fuel are presentedThe final products of this research are simplified and validated tools for modeling aluminum furnaces. These include improved heat and energy balance models and parameterized CFD solutions which provide rapid customization to individual furnace configurations. These tools provide field engineers with immediate and accurate predictions of performance, allowing for repeated precise scenario analyses."

Jan 1, 2001

By Tatsuzo Kitamura

The tank house of Tamano refinery, that started its operation in January, 1972, was constructed incorporating the application of Periodic Reverse Current (P.R.C.) from the outset of design works. In 1973, the production of electrolytic copper came up to 8,000 mtpm, a sharp increase ds compared with the designed capacity of 7,000 mtpm, and successful operation has been achieved up to the present. P.R.C. has been employed for the purpose of raising productivity level and reducing copper inventories. Since there were various problems in P.R.C. application to such a large sized cathode as 1 m x 1 m, special attentions were paid to the following items: -Development of a unique bus bar to make an electrolytic current to each electrode as uniform as possible. -Improvement of circulating method of electrolyte. -Application of high-performance equipment to realize a uniform spacing between anode and cathode. Owing to these creative technical developments mentioned above, technical level for operation up to 350 amp per sq m of cathode current density has been established. The quality of electrolytic copper, which was a matter of interest, has been proved to be as excellent as those of conventional electrolysis products through a long term supply to the field of SCR and Dip forming where high levels in quality are required.

Jan 1, 1976

By Carlos Ortiz

The Huelva Flash Smelting Furnace was commissioned in September 1975. The Smelter and the Acid Plant were expanded in 1995 to their present capacity of 300,000 tpa new copper equivalent and one million tonnes of concentrate per year. During these years of operational experience, most of the initial practices have been reviewed, process control has drastically improved and main process equipment has been modernised. The fourth Flash Furnace campaign lasted 9 years (1995-2004) during which 8 million tonnes of concentrate were smelted. Increasing sulphur content in concentrates and new environmental requirements imply new challenges for smelters to keep production and operation costs down. This paper is an overview of the modifications and improvements carried out in the 2007 general shutdown in Smelter and Acid Plants. Al

Jan 1, 2008

By Fathi Habashi

In the past five years Cuba has been attempting to more than double its nickel production by constructing two new ammonia leaching plants. No metals are yet produced on commercial scale but a variety of oxides and sulfides. This report updates the Cuban nickel industry as a result of two visits : one at the invitation of the Cuban Ministry of Basic Industries in 1987 and the other as a consultant to the United Nations for the Cuban Laterite Project in 1989.

Jan 1, 1993

By Jay. M. Khodadadi, Josef Štetina, František Kavicka

"With the aid of the proper original numerical model of solidification the instruction for preparation of input parameters for numerical simulation of technological processes, with change of the phase or structure, will be presented. A method of calculation analysis of influence of therrpophysical properties of materials entering the system of casting-mould-cores environment, and also of boundary conditions on the required simulation accuracy will be suggested. For the cast material, the influence of heat .conductivity, specific heat capacity, density and latent heat of phase transformation also has been analysed. For metallic or non-metallic moulding material"" the influence of the see main parameters has been analysed and, furthermore, their combination, influence of thermal conductivity, and of heat storage. The order of influence of all quoted parameters of a casting and moulding material was established. For example heat conductivity in the liquid state is on the last place. From the boundary conditions the -most important influence on the total solidification time and · on the mechanism of forming of temperature field has the ·boundary condition on the casting mould boundary, then follows the boundary condition on the level of a molten metal. The negligible influence has the boundary condition on the mould frame and on the bottom.IntroductionThe original and universal mathematical model of solidification, cooling and heating has been set up and checked, in order to be capable of analysing a one- to three-dimensional steady or unsteady temperature field of the casting-mould-environment system and, namely, of the system as a whole or its arbitrary parts, during any industrial technological process whose individual processes could be solidification, cooling, heating, refrigeration and others, in any sequence or singly. The model enables the simulation of traditional and also non-traditional technologies of casting in foundries, metallurgical plants, forging operations, heat treatment processes, etc. If solidification is not the matter, the metal part of the system need not be called the casting but a component, a block, a forging and the like."

Jan 1, 2000