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By N. R. Green, N. J. Humphreys, D. McBride, T. N. Croft, M. Cross, D. M. Shevchenko

"Centrifugal casting offers a route to high quality products in difficult to cast high temperature low superheat alloys and thin section molds. Under centrifugal forces metal is forced into thin sections and can fill thicknesses of less than a millimeter. However, due to the high liquid metal velocities there is a high risk of surface turbulent flow and air entrainment within the liquid metal. The combination of interacting flow-thermal-solidification phenomena and associated defects is a challenging modeling task which the authors have previously described and validated. Capturing the metal-air interface, on what are inevitably complex three dimensional geometries, results in highly computationally expensive simulations and simulating a single cast can take weeks on a single processor. This contribution reports on modeling a complex centrifugal cast, gas entrainment, bubble transport and solidification, employing meshes of up to a million elements and investigates the scalability of the model on high performance clusters.Introduction The ultimate goal of any casting procedure is to produce a defect-free product. For difficult to cast alloys, such as Titanium, centrifugal casting has a number of advantage over conventional gravity methods [1]. In the casting of thin sections, such as turbine blades, the metal is forced into the thin sections under centrifugal forces. The centrifugal force can overcome the backpressure due to surface tension and the metal can fill mould sections with thicknesses substantially less than a millimeter. However, the materials used in these castings [2] tend to be highly reactive and requires low superheat. High liquid metal velocity gives rise to a high risk of free surface turbulent flow and of associated entrainment through free surface turbulence [3] and trapping of gas present in the flow [1]."

Jan 1, 2012

By Henry Hu, Alfred Yu

"A numerical model has been developed to simulate heat and mass transfer phenomena occurring during a novel magnesium reduction process-the vertical retort technology. The model was based on the control - volume finite difference approach. Simulations were run to determine the effect of various processing parameters on magnesium reduction cycle time. The model predicted temperature distributions, heating curves, recovery ratio of magnesium, and total process times. The predictions were used to optimize the magnesium reduction process including dimensions of the retort, geometries of the reactant compounds, and productivities. The results indicate that the implementation of the optimized processing parameters significantly decreases the reduction time, and consequently increases the production rate as well as lowers the energy consumption.IntroductionMagnesium consumption has been growing considerably in the past decade [1]. Of the total magnesium production, 30% is produced by the thermal reduction (Pidgeon) process, and it is anticipated to be still the main technology for producing magnesium in future [2]. One of the advantages of the Pidgeon process is that it is capable of producing high purity magnesium demanded by both the automotive and aerospace industries. However, the inefficiency of heat and mass transfer taking place in the horizontal Pidgeon reduction process results in low productivity, high energy consumption, labor-intensive operation, large floor space and high capital investment. This limits the production scale of a horizontal Pidgeon reduction process [3].Vertical reduction processTo overcome the shortcomings of the horizontal magnesium reduction process, a novel vertical magnesium reduction process [3] for large-scale production has been developed, in which heat and mass transfer in the retort is enhanced. The new process shortens reduction time, reduces energy consumption and increases productivity. The vertical reduction system is comprised of a vertically-placed retort, a heating furnace and a vacuum system. A section of the vertical retort is illustrated in Figure 1. Since the retort is set vertically, instead of horizontally, the entire procedure of loading the reactants material in the new process is different from the one for the horizontal reduction process."

Jan 1, 2001

By Richard L. Werner

The petrographic microscope as a tool in determining impurities and grain size of limestones, clays, sand and coal ash for possible use as raw materials is discussed. Its use in the determination of the mineral composition of various size fractions of the raw mix, after fine grinding in ball mills, and of the waste dust from the rotary kiln. A description is given of the typical clinker crystals; alite, belite, tricalcium aluminate and ferrite. The process problems indicated by various changes in the crystal characteristics are listed with possible solutions. Finally the microscope as used in relation to field problems with concrete such as air void volume, percent hydration of the cement, cement aggregate bonding and the determination of solid additives, is presented.

Jan 1, 1982

By P. Cowx

The carbothermic reduction of zinc oxide rich Electric Arc Furnace baghouse dust in the Tetronics transferred arc plasma furnace to produce a non-toxic slag and a metallic zinc product is described. In particular, the operation of the zinc splash condenser coupled to the plasma furnace is examined and the effect of process variables on zinc recovery is discussed.

Jan 1, 1990

By Gus Van Weert

This paper describes the results of autoclave testwork where ferric nitrate was hydrolysed in the presence of certain cations and anions and the resulting hematite analyzed for foreign constituents. For the cations Zn++, Ni++, Cu++, and AI+++, selectivity factors of over 107 were found. Magnesium gave 3.106. These factors are calculated as Me/Fe in solution over Me/Fe in the hematite; Me representing the metal in ion added. As-a result of the testwork at Delft University of Technology, BUDELCO (the Netherlands electrolytic zinc producer) ran a series of ferric nitrate hydrolysis tests in the presence of 10 additional trace elements. Impurity levels were prejudiced on Me2 EPHA extraction of iron from their zinc circuit, followed by HNO3 stripping. Good selectivity against base metals was confirmed, but trace elements forming anions (As. Sb) and sulphate were incorporated in the hematite. These BUDELCO results are also presented.

Jan 1, 1995

By T. T. Nguyen, D. R. Gunasegaram, D. Celentano

"Heat transfer rates at the casting-mold interface are believed to be substantially reduced by the formation of an interfacial gap during the course of solidification of aluminum alloys in permanent molds. In the current work, the effect of force-cooling a permanent composite mold on (i) the initiation and growth characteristics of the gap and (ii) interfacial heat transfer rates are studied. Interesting comparisons are made with the case where no cooling is employed. Casting and mold displacements are measured using L VDTs, and the mold is force-cooled by air jets.IntroductionIn a gravity casting situation where an aluminum alloy solidifies in a permanent mold, a gap initiates and grows between the shrinking casting and the expanding mold (1). It is widely believed that the formation of this gap, customarily referred to as an 'air gap', results in a substantial reduction in the heat transfer coefficient at the casting-mold interface (2), and hence is an important factor in solidification studies.The nature of the air gap formation process is thermo-mechanical. The rate of heat loss from the casting first determines the rate of solidification, which, in turn, decides when the gap initiates. The reason for this is the requirement for the solidified casting surface 'skin' to gain sufficient thickness, and hence strength, to be self-supporting. Once the gap initiates, the gap width controls the rate of heat loss from the casting, which, again, determines the rate at which the gap expands."

Jan 1, 1997

By Renato G. Bautista

"The development of processing methods for the preparation .of three electronic materials with rare-earth components is discussed. The resulting processing innovations are the results of a search for an economically competitive pilot scale or industrial production flowsheet without compromising the required properties of the final products. The three cases highlighted in this presentation are: 1) The preparation of high energy (Pr-Nd-Ce)FeB magnets for MRI application from a mixed-rare-earth oxide with a narrow range of composition directly prepared from the solvent extraction circuit of bastnaesite ore. 2) The kg production of the giant magnetocaloric effect Gds(SixGe1-x)4 magnetic refrigerant materials from commercial grade gadolinium metal (95 to 98 at. % pure) instead of high purity gadolinium metal (99.8 at. %); and 3). An industrial chemical synthesis flowsheet for the production of the superconductor precursor of YBa2Cu3O7.INTRODUCTIONIn the laboratory discovery stage, the synthesis of a new material is carried out using very high purity components, usually the highest purity available. As the new material is studied and characterized, the effectiveness of its desirable properties becomes better defined and understood. The evaluation of the effectiveness of the .property over the range of a given parameter and other interactions are further studied. Once it's potential application becomes clear, a practical and economical processing method need to be developed. The successful material processing flow sheet does not necessarily have to be a scale up of the laboratory procedure. At this stage, substitution of starting components and with lower purity materials is considered as the economics of the processing becomes a major issue. In addition, other approach to it's synthesis"

Jan 1, 2000

By Zhijing Zhang

Sodium borosilicate is the basic composition of coating materials, Vycor and Pyrex glasses. In the present study, viscosities of Na2O-Si02-B2O3 ternary melts were measured under various compositions and temperatures. Experiments were carried out using rotary viscometer and graphite components. Our experimental results were compared with those in literature. Based on present experimental results, the previous structure based viscosity model was modified. The predicted viscosity results are in excellent agreement with the present experimental data in the temperature range with molten state samples. The fitting ranges of the model cover the composition of XB2O3 from 0.1 to 0.6 combined with xSio2 / xNa2O = 0.5, 1,2 and 5 respectively.

Jan 1, 1998

By Kuiting Wang, Jinshan Liu, Ninglei Sun, Aiguo Dong, Yeda Lu

"Eliminating the environmental threat caused by waste effluent containing magnesium sulfate derived from the process of nickel laterite sulfuric acid leaching and subsequent nickel precipitation is always a focus in the metallurgy field. A new flowsheet whose procedures include vaporization, crystallization, two stages precipitation of magnesium, causticizing treatment of filtrate and ammonia recycle was investigated. Both the details of the flowsheet and its application are described in this article. It is confirmed to be an effective and economical method to prevent the pollution by the waste effluent, simultaneity, a series of magnesium products recovered during the process own good economic returns.IntroductionSulfuric acid leaching is the conventional procedure of extraction valuable metals from ores in hydrometallurgy field. During the process of nickel laterite sulfuric acid leaching, several metals, including Ni, Co, Al Mn, Fe, Mg etc., migrate into the leachate in the form of soluble metal sulfate. After subsequent procedure of purification, precipitation of Ni and Co and neutralization, an enormous stream of waste effluent which contains a concentration of approx. 15-40g/L Mg is exhausted. Such solution containing magnesium sulfate is toxic, which causes diarrhea for both human and animals. On the other hand, large amount of sulfate acid was consumed during the process of leaching by the compound of Mg, which increases cost of a hydro nickel plant.In arid areas, the waste effluent mentioned above is treated via evaporate pond owning large acreage, which needs not only the appropriate meteorologic condition, but occupies much land. In coastal areas, it is directly discharged to the sea, which probably deteriorates ecological system of offshore strip. The most widespread method to treat with the waste effluent is neutralization by lime cream, the residues of which containing magnesium hydroxide and gypsum are transported to residues pool. Neutralization is a simple process, but it never recycles the Mg and sulfate anion into new application, meanwhile, the residues are potential threat to the environment."

Jan 1, 2012

By P. Blazy

A hydrometallurgical procedure for the recovery of metal from ore, particularly of copper from sulphide materials is described. In the course of this procedure, the raw material is first of all submitted to the action of an appropriate reducing system and then treated with a ferric salt solution which brings about the selective solubilisation of the elements to be recovered with respect to those constituting the pyritic phase. This procedure is investigated using two ore samples proceeding from massive sulphide deposits, presenting different chemical and mine- ralogical characteristics. The results of this investigation are compared with those obtained by a classical process employing a ferric salt solution. It appears that one solubilisation of copper takes place under particularly advantageous conditions when our procedure is used. The principal parameters affecting leaching of zinc, lead and copper are examined. The selectivity of this treatment is evaluated by following the change during the treatment in the pyritic phase.

Jan 1, 1976

By Gabriel A. Torma

This paper provides infonnation on selected technologies available for remediation of metal contaminated soils and industrial effluent solutions. Because some of the industrial sites are contaminated with organics (solvents, gasolines and oils), an effort has been made to introduce the most frequently used cost-effective cleanup methods, such as "bioventing" and "composting." The microorganisms involved in these processes are capable of degrading organic soil contaminants to environmentally harmless compounds: water and carbon dioxide. Heavy metals and radionuclides contaminated mining and industrial sites can be remediated by using adapted heap and dump leaching technologies, which can be chemical in nature or bio-assisted. The importance of volume reduction by physical separation is discussed. A special attention is devoted to the remediation of soils by leaching (soil washing) to remove heavy metal contaminants, such as chromium, lead, nickel and cadmium. Furthermore, the applicability of biosorption technology in the remediation of heavy metals and radionuclides contaminated industrial waste waters and acidic mining effluent solutions was indicated.

Jan 1, 1996

By G. H. Khoe

Although some hydrometallurgical process liquors contain significant amounts of ferrous and arsenate ions, no reliable thermochemical data for the aqueous complexes and the solubility of the ferrous arsenate precipitate are available. The complexation of iron(11) with arsenate has been investigated using the potentiomemc titration method. The results indicated that virtually no complexation of iron(@ with arsenate has been observed. This is in contrast to the significant complexing reported for iron(1n) with arsenate. The solubility product of the precipitate was calculated using the concentrations of appropriate arsenate species pertaining to the observed precipitation pH's. The fit of the observed precipitation points on the solubility curve of the computed stability diagram was used to assess the appropriateness of the equilibrium model.

Jan 1, 1991

By Walter Curlook

An improved process of hydrometallurgical treatment of laterite ores of the limonitic type for the recovery of nickel and cobalt using sulphuric acid has been developed and patented [I]. The major improvement is brought about by recycling a significant portion of the "mother liquor" emanating from the pressure leaching reaction back to the feed preparation stage thereby substituting for all or at least a major proportion of the fresh water that must be added. The amount of process effluent waters is correspondingly reduced. Concomitantly with the major savings in fresh water requirements, a degree of reduction in new sulphuric acid requirements is effected, along with a savings in limestone and lime required for subsequent neutralizations. Keywords: Acid pressure leaching; Nickel laterites

Jan 1, 2004

By C. E. Hunt

Since the turn of the century, copper-nickel sulphide ores have been processed at the Sudbury, Ontario operations of INCO Limited, currently the largest integrated mining, milling, smelting and refining complex in the free world. Through the years operational, ecomomic, social and legislative changes have dictated the need for research and development directed at mitigating the impact of existing operations on the surrounding natural environment and also the reclamation of areas affected by earlier mining activities. Approximately one hundred years of mining history and the current annual processing of some 12 million tons of ore presents significant challenges with respect to waste disposal, liquid effluent treatment and land reclamation, particularly in light of rapidly evolving environmental regulations' and controls within the Province of Ontario.

Jan 1, 1992

By R. Kramer

During foundry sand reclamation process development, molds formed from reclaimed chromite sand showed a rapid decline in tensile strength during thermal cycling tests. Because this characteristic could limit reuse of chromite sand in the. foundry, the sand was examined in detail Scanning electron microscopy, x-ray mapping, magnetic susceptibility, and x-ray diffraction were utilized to evaluate processed chromite sand. It was found that process variables such as binder composition, reclamation temperature, and processing method had a significant effect on the chromite sand particle surface. X-ray diffraction indicated a crystallographic change in the processed sands. Magnetic susceptibility also increased after processing. Diffusion of iron to the particle surface and increased surface roughness were identified as potential causes of the decreased tensile strength in the molds.

Jan 1, 1991

By J. P. Downey, T. Salisbury, M. Berlin, E. Rosenberg, G. Pinson, R. Christianson, K. Gleason, W. Gleason, S. Davis

"The Center for Advanced Mineral and Metallurgical Processing is developing membrane production technology based on autocatalytic reduction of palladium from solution onto a unique, porous substrate. Surface membranes and catalytic structures are critically important to applications that range from hydrogen purification membranes to petroleum refining. Autocatalytic reduction processes represent a cost effective method of producing stable surface layered structures that have good working lives. These attributes are particularly important in the production of palladium alloy purification membranes used in hydrogen production. Although considerable research has investigated the interaction of hydrogen and palladium alloys, the mechanisms in play while the membranes form are not well understood. Preliminary research has identified three distinct deposition mechanisms and it appears that substantial control over the resulting membrane is possible.IntroductionPalladium-based membranes separate hydrogen from other gases because hydrogen is uniquely soluble in and readily passes through bulk palladium. As currently produced, palladium-based membranes are expensive and have short service lives. These circumstances are due in part to the lack of a complete understanding of palladium or palladium alloy deposition. The Center for Advanced Mineral and Metallurgical Processes (CAMP), in collaboration with the Metallurgical and Materials Engineering Department at Montana Tech and the Chemistry Department at the University of Montana, is engaged in the development of new methods and materials for hydrogen purification membrane production.In membrane production, the palladium requirement depends on substrate surface properties such as surface chemistry, porosity, and roughness. Thin, defect-free membranes have been successfully produced on substrates of porous glass, alumina, and stainless steel. However, the differences in the thermal expansion coefficients of palladium membranes and porous glass or alumina substrates cause problems at operating temperatures. The use of stainless steel substrates is advantageous because stainless steels have thermal expansion coefficients similar to that of palladium and they are stable at the required operating temperatures (Wicke, E., Brodowsky, H. and Ziichner, H. ). Stainless steel is also readily available and relatively inexpensive."

Jan 1, 2012

By Christina V. White

An experimental study was undertaken to investigate the feasibility of utilizing vapor transport for the treatment of heavy metal contaminated smelter soils. The focus of this project was to develop process chemistries that would make incineration a viable process for the treatment these soils. The experimentation concentrated on the elimination of arsenic, cadmium, and lead, and was performed in a laboramry scale rotary kiln setup. Three soil samples from non¬ferrous smelter sites, which contained various concentrations of contaminants, were utilized in the experimentation. Three chemistries were investigated for the volatilization of the heavy metals: Chloridizing volatilization, ferric chloride vapor complex formation, and the use of oxygen potential control. The samples were analyzed for residual heavy metals so that the extractions could be determined. However, the ultimate test was the leachability of the residual arsenic, cadmium, and lead, as determined by the TCLP test. The results firmly establish that incineration is a feasible process for the treatment of metal contaminated soils. It was found that no one process chemistry is suitable for all different soil samples. A two-step process consisting of a reducing step followed by a hydro-chlorination step was required to make Soil Sample-B pass the TCLP tests for all three heavy metals. Soil Sample-A passed the TCLP tests for arsenic, cadmium, and lead using a hydro-chlorination process at a minimum temperature of 700°C. In addition to passing the TCLP mm for Soil Sample-A and Soil Sample-B, 70 to 80 percent removal of the impurities was accomplished. This demonstrates that the leachability of the impurities was decreased primarily due to the removal of a large fraction of the contaminants, Soil Sample-C possessed very high levels of cadmium and lead and only moderate extractions of the impurities were generated from this soil. The arsenic TCLP test was passed at 500'C using a process gas containing ferric chloride and at temperatures of 700°C and above using chlorination of hydro-chlorination.

Jan 1, 1996

By Kandipati Sreenivasarao

A promising method for removing heavy metal ions from dilute effluents is ion- or precipitate- flotation, in which a suitable collector is added to form hydrophobic metal-collector complexes or compounds that can be collected as foams. We have successfully removed Cu(II), Cd(II), and Pb(ll) from dilute solutions using sodium dodecylsulfate and ethanol as collector and frother respectively. However the process would not be economically viable unless the collector could be recycled, and the heavy metals recovered in a concentrated, preferably marketable, form from the foams. We investigated four different methods to decompose heavy metal-dodecylsulfate complexes, namely precipitation of hydroxides, precipitation of sulfides, chemical stripping, and electrolysis. We compare the performance of these methods. In each case the observed behavior is related to known thermodynamic data, and potential applications are discussed.

Jan 1, 1995

By H. Hirayama, T. Okura, O. Kato

"Saganoseki Smelter & Refinery, one of the largest copper smelters in the world, has the annual capacity of 300,000 metric tons in copper content with two flash furnaces, six Pierce-Smith type converters, two anode furnaces, four acid plants, three tank houses and perfect pollution control system.Coping with the many severe conditions surrounding the copper industry in the last decade, Saganoseki Smelter has kept performing the stable operation, while enhancing the smelting capacity and developing new technologies such as the hydrometallurgical treating of converter dust recovered at electric precipitators. Especially in the operation of flash furnaces, which are of Nippon Mining's conversion type using hot air in a temperature of l,000ºC some technological improvements and complete operation control factors have approved the concentrate feed rate to reach to 2,200 tons a day for a flash furnace.Reported in this paper are the production control design for copper smelting process, and the operation control scheme of the flash furnace following the brief review of the characteristic of Saganoseki Smelter's process and some improvements. Copper Smelting ProcessDescriptions of major unit operations and general specifications of the copper smelting facilities are summarized in Table 1, and the present flowsheet of the copper smelting is described in Figure 1 (1,2).Outputs and raw materials treated in the last five years are shown in Table 2, in which concentrate includes powder copper scrap which amounts to 3 to 4% of concentrate.A full operation was performed for a period of one month, for both one flash furnace operation and for two flash furnace operation. With one furnace operation, 19,200 tons of copper were produced. With the two furnace operation, 84,000 tons of concentrates were charged and 33,500 tons of anode (net 28,600 tons of copper) were produced.The actual production level, however, has been kept at 80 to 90% of the full capacity because of low copper price, tight market of copper concentrate or fall of net demand in Japan."

Jan 1, 1989

By Shoji Taniguchi, Lifeng Zhang, Kaike Cai

"In the present paper, based on the two-phase (Eulerian-Eulerian) model, the 3D fluid flows in gas-stirred systems, i.e., air-stirred water vessel and argon-stirred liquid steel ladle, are simulated. In the Eulerian-Eulerian two-phase model, gas and liquid are considered to be two different continuous fields. The phases are assumed to share space in proportion to their volume fractions. The exchange between the phases is represented by source terms in conversation equations. Turbulence simulated by the k- e model is assumed to be the property of the liquid phase. The following effects of mathematical treatments and operational factors on the fluid flow are discussed, such as interphase drag force, turbulent model, the size of bubble, and gas injection mode.Some interesting results are derived. Except the interphase drag force, the interphase lift force should be taken into accounted in order to exactly simulate the fluid flow in gas-stirred systems. Suitable turbulent model and drag coefficient have effect on the mathematical simulation. Injecting small bubbles can realize a well mixing flow condition. The distance between the two gas-injection nozzles has effect on the fluid flow."

Jan 1, 2000