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By M. Wu, A. Kharicha, J. Bohacek, A. Ludwig

"During the horizontal spin casting of rolls, vibrations and mould deformations seems to have a significant effect on the final quality of the product. Sources for vibrations can be found in the poor roundness and a static imbalance of the chill itself. The bending of the mould axis is also considered. Both, vibrations and axis bending, are used as an input for CFD simulations of the flow dynamics of the liquid metal inside the rotating cylinder. The aim is to study the feedback of the free surface behavior in terms of wave propagation and various wave shapes. Introduction The horizontal spin casting process (HSC) is a casting process that has several advantages over the traditional gravity casting processes. Centrifugally cast products have a high degree of metallurgical purity and homogeneous microstructure. A significant gain is observed for the rupture strength, the rupture strain, and the Young modulus. These properties naturally depend on the centrifugal force and thus, the best mechanical properties can be found at the largest distance from axis of rotation. However proper selection of the angular frequency has to be done in order to prevent the so-called ""metal rain"" i.e. metal droplets can fall down from the upper part of the cylinder due to a too weak centrifugal acceleration. In the same time excessive speeds can lead to the appearance of longitudinal cracks caused by the hoop stress in the initially solidified layer. From empirical knowledge other parameters have important influence on the casting products, it includes the pouring temperature, the pouring rate, the mould coating etc. Recently the presence of natural or forced vibrations have been identified as possible additional factors to be taken into account [1-2]."

Jan 1, 2012

By O. Chemezov, Yu Zaikov, A. Apisarov, A. Isakov

"Silicon deposits containing 99,9 wt.% of main component were obtained by SiO2 electrolysis from chloride-fluoride melts. The operating temperature was varied from 973 up to 1073 K. The conditions for obtaining crystalline fibrous micro- or nanodeposits were determined. The deposits were investigated by ESM methodIntroductionThere are large reserves of natural quartz of high purity in Russia. Processing of this raw material by electrolysis in molten salts produces silicon containing 99.9 weight percent of basic substance.[1]This method is less energy-consuming in comparison to existing methods for producing high purity silicon from gas phase.Another advantage of the electrolytic method for producing silicon from its oxide in molten salts is the possibility of production of high-purity silicon under air atmosphere. It dramatically reduces costs of the electrolytic cell construction, and the operating costs at electrolysis.On our opinion, the main advantage of the electrolytic production from SiO2 in molten salts is a unique opportunity to obtain micro-and nanostructures of silicon deposits. In particular, it is possible to obtain fibrous structures of silicon. The electrolytic method allows smoothly adjusting the thickness and length of silicon micro- and nano-wires by varying the cathode current density and temperature of the process."

Jan 1, 2012

By Dexter G. Mendoza

To analyze the behavior of minor elements in the copper smelting process, the phase relations and the activities of arsenic and antimony in the miscibility gap of Cu-Fe-S-X (X = As or Sb) system have been determined at 1473K by the quenching method and the double Knudsen cell- mass spectrometric method, respectively. The experiments have been conducted for the charges in the miscibility gap with different mass%Fe/mass%Cu ratios with varying arsenic or antimony content. The activity measurements indicate that the arsenic activities in both the metal and matte phases show extremely negative deviation from the ideal behavior. The Raoultian activity coefficients at infinite dilution in the metal and matte phases are found to be almost constant against the charges in the miscibility gap, and they are 4.3 x 10-3 and 5.5 x 10-2 for the metal and matte phases, respectively. Moreover, the activity measurements of antimony show an activity value larger than that of arsenic but it still deviates negatively from Raoult's law. The activity coefficients of antimony at infinite dilution are found to be 1.2 x and 2.2 x 10-1 for the metal and matte phases, respectively. The vapor pressures of the predominant As, AS2, AsS, Sb, Sb2, and SbS species in the gas phases of arsenic and antimony, respectively, equilibrated with the immiscible solutions have been calculated on the basis of the determined activity coefficients and they are very small at less than 1 Pa, even when their contents in the metal phase are increased up to 10 mass%.

Jan 1, 2002

By František Molnar, Zsolt Szentirmai, Juraj Schmiedl, Felix Sekula

"Hydrometallurgical nickel production in Sered Nickel Plant (Slovakia) that treated roasted Albanian ore left behind a considerable amount of the solid leaching residue. About 6 million tons of this fine-powder residue containing approximately 52 wt.% of iron in the form of oxides is to the present day stored in a stockpile. However, its iron content makes it a potentially interesting secondary raw material for iron production. This secondary raw material is not, unfortunately, suitable for direct treatment in iron and steelmaking processes.This paper presents results of the laboratory tests of pyrometallurgical method of processing of the leaching residue by its roasting and subsequent refining melting. The objective of the selective reducing agglomeration roasting was to reduce iron oxides and to simultaneously avoid reduction of chromium oxides and silica. Refining melting is carried out in an inert atmosphere. The products of melting are technically pure iron and slag.IntroductionThe leaching residue stockpiled on waste dump near already non-existing Nickel Plant Sered, Slovakia, is considered to be one of the most important environmental burdens in this country. The 40-years of an on-going effort focused on finding the methods for extracting metals and thus remove the waste dump have not been successful [1,4,5,6]. From the literature survey it is evident that past investigations have been following three main routes:1.Removal of chromium by mineral processing methods prior to its metallurgical treatment to achieve final chromium concentrations below 0.3 wt.%.2.Pelletization of solid leaching residue and its subsequent reduction in blast furnace and steelmaking plant and simultaneous removal of chromium.3.Pelletization of solid leaching residue followed by metallurgical processing of preliminary reduced semi-product in electric arc furnace (EAF) accompanied by partial reduction of chromium."

Jan 1, 2008

By D. J. Goodwill

BHP Copper operates a 3,400 tpd dry concentrate, single burner, Outokumpu flash smelting furnace (FSF) at their San Manuel copper smelter in Arizona. The very fine (-325 mesh), dry concentrate is fed to the burner from a 550 metric ton (nominal) capacity furnace feed bin via two drag chain feeders. During the 10-year history of the furnace, operations have been plagued by serious flooding problems. The fine concentrate sometimes becomes aerated during discharge from the bin and flows like a fluid at very high uncontrollable rates to the burner. This results in upset conditions at the concentrate burner leading to poor furnace metallurgy. This paper will examine the problems of uncontrolled feed from the furnace bin (i.e. flooding), and' instantaneously feeding a flash smelting burner. It will show that a drag chain is a poor choice of feeder when high rates are needed, and that drag chains always produce a funnel flow pattern in a bin. BHP's drag chains cause narrow diameter, high velocity flow channels within the stored material. Consequently, there is insufficient residence: time for the concentrate to fully de-aerate before discharge, hence flooding occurs. In addition to the flooding problem, drag chains create a pulsating flow to the concentrate burner due to the tendency for material to slough off in discrete chunks at the discharge end of the slow moving chain conveyor. During the scheduled FSF rebuild in May 1999, BHP intends to remove the drag chains, modify the bin to a mass flow design and to use STAMET® multi-disc feeders to accurately and instantaneously control the rate of discharge from the bins. Air slides will be used' to convey the concentrate to the burner.

Jan 1, 1999

By Andrzej Warczok

Liquid slags produced in smelting of copper concentrates contain copper in a dissolved form as well as mechanically entrained inclusions of copper matte. Coalescence and sedimentation of inclusions during slag cleaning plays a key role in copper recovery. Liquid matte inclusion in a molten slag presents a system of metallic conductor in an ionic solution. Constant electric field induces migration of the matte droplet along the current lines. Additional phenomena occur in a system under crossed electric and magnetic fields. Electromagnetic buoyancy force acting on the inclusion affects its settling rate. Electromagnetic buoyancy force of insulating and metal spheres has been measured in a liquid synthetic slag. It was found that depolarisation of the metal sphere, related to the electrode reactions occurring in the surface, plays an important role in the determination of the direction and magnitude of the electromagnetic force. On the basis of the existing theories and results of measurements a mathematical model describing the behaviour of metallic inclusions in the liquid slag under the influence of crossed electric and magnetic fields was developed. Simulation of behaviour of copper matte inclusions under crossed fields showed trajectory of motion in a liquid slag as a function of the slag properties and the inclusion size.

Jan 1, 2003

By A. Robles

The main goal of the present work is to propose a viable alternative for selective arsenic elimination from copper smelter flue dust without the need of a global leaching scheme for all the individual components of the flue dust. Using this alternative, the inherent copper recovery problems are avoided. Arsenic precipitation is also considered for regenerating the solution and completing the process cycle. The experimental results for arsenic extraction and precipitation are satisfactory. Concentration of NaOH used was relatively low. The main reason for succeeding in high arsenic extraction and low NaOH consumption is due to the previous water washing of the flue dust. Water washing dissolves much of the iron and copper that are present in certain percentage as sulphate.

Jan 1, 1999

By Patrick R. Taylor

Titanium nitride has been synthesized in a thermal plasma reactor from ilmenite ore concentrate using methane and ammonia as the reactive gases. The product has been characterized by x-ray diffraction and SEM. Results show that a high concentration of methane favors the formation of iron, titanium nitride and titanium carbonitride. The formation of titanium carbonitride can be minimized by controlling the concentration of methane. The formation of TiN proceeds by the progressive reduction of the oxides of titanium to titanium, which is converted to titanium nitride.

Jan 1, 1998

By Volker Uhlenwinkel

The design of a free fall atomizer as well as the process parameters affect the particle mass flux distribution in the spray cone. The mass flux distribution is important in spray forming because of its influence on the deposit shape and enthalpy input into the deposit. In this article the effect of different process parameters on the mass flux distribution is shown. Furthermore, different melts were atomized with the same atomizer. An empirical correlation will be introduced to predict the mass flux in the spray cone. This correlation will be compared with experimental results.

Jan 1, 1999

By Rikiya Kamezawa, Rudiono, Manabu Takeuchi

"Schottky type solar cells based on phthalocyanine (Pc) thin films were fabricated, and their photovoltaic performance was investigated in various ambient atmospheres. Most of cells prepared in this study showed a good rectification and photovoltaic effects in the visible wavelength region. The introduction ofN02 gas into the measuring chamber was confirmed to increase the current both in dark and under light illumination. However, chemical reaction between the Al electrode and N02 formed some oxide and deteriorated the Schottky barrier, resulting in an increase in cell resistivity. SF 6 gas also showed similar effects on the cell performance.IntroductionPhthalocyanine is one of the typical organic semiconductors, which shows high photoconductive sensitivity in the visible to infrared region. Today, several kinds of metal phthalocyanines are used in electrophotographic photoreceptors. In addition, application of phthalocyanines to solar cells have also been trying by many workers [1, 2]. Many efforts have been made for improving performance of phthalocyanine solar cells by modification of device structure [3, 4], doping by dye or pigment [5, 6] and incorporation of metal clusters [7]. It is known that electrical conductivity in phthalocyanine is increased by adsorption ofNO2 [8, 9]. We tried to improve photovoltaic performance ofphthalocyanine solar cell by adsorption ofNO2. This paper describes the influence of N02 adsorption on the photovoltaic behavior of phthalocyanine solar cells."

Jan 1, 2000

By C. T. Yavuz

Higher environmental standards have made the removal of arsenic from water an important problem for environmental engineering. Iron oxide is a particularly interesting sorbent to consider for this application. Its magnetic properties allow relatively routine dispersal and recovery of the adsorbent into and from groundwater or industrial processing facilities; in addition, iron oxide has strong and specific interactions with both As(III) and As(V). Finally, this material can be produced with nanoscale dimensions which enhance both its capacity and removal. The objective of this study was to evaluate the potential arsenic adsorption by nanoscale iron oxides, specifically magnetite (Fe3O4) nanoparticles. We focused on the effect of magnetite particle size on the adsorption and desorption behavior of As(III) and As(V). The results show that the nanoparticle size has a dramatic effect on the adsorption and desorption of arsenic. As particle size is decreased from 300 nm to 12 nm the adsorption capacities for both As(III) and As(V) increase nearly 1000 times. Interestingly, this increase is more than expected from simple considerations of surface area and suggest that nanoscale iron oxide materials sorb arsenic through different means than bulk systems. The desorption process however, exhibits some hysteresis with the effect becoming more pronounced with small nanoparticles. This hysteresis most likely results from a higher arsenic affinity for magnetite nanoparticles. This work suggests that magnetite nanocrystals and magnetic separations offer a promising method for arsenic removal.

Jan 1, 2006

By E. Morrice

Solubility of yttrium oxide (Y203) in fluoride melts was experimentally measured in the temperature range of 998 to 1273 K and, YF3 composition in LiF.YF3 melts varying from 20 to 50 mole pct using a graphite crucible in an argon atmosphere. Solubility of oxide in the melt was found to increase with increasing temperature and YF3 composition in the melt. An expression for in XY2O3 as a function of temperature for several melts was deduced. The calculated activity coefficients of Y2O3 in the melts exhibited a negative deviation from Raoult's law.

Jan 1, 1989

By Anjali Talekar

Low temperature heat capacities of pentaerythritol [PE: C(CH2OH)4], pentaglycerine [PG: (CH3)C(CH2OH)3], and 2-amino-2-methyl-1,3-propanediol [AMPL: (NH2)(CH3)C(CH2OH)2]have been determined by adiabatic calorimetry from 3 K to 300 K. To the best of our knowledge, this is the first reported heat capacity measurement below 280 K for PE and AMPL. The Debye temperatures for these organic crystals have also been determined and compared with other alcohol derivatives of neopentane.

Jan 1, 2006

By C. A. Summers

The U.S. Bureau of Mines applied process mineralogy to investigate a lead and zinc deposit located near Story Creek, Colville Mining District, Alaska. Mineralization is hosted by the Kayak Shale in veins, veinlets, and breccia. Sphalerite and galena, with supergene anglesite, occur in symmetrical quartz veins and between breccia clasts. The study sample analyzed 2.11 percent Pb, 5.37 percent Zn, 0.014 percent Cu, and 1.2 oz/ton Ag. Analyses of crushed products showed that 33 percent of the sample weight, and more than 50 percent of the Pb and 65 percent of the Zn, are in the minus 850 um fraction. Liberated grains of sphalerite and galena were found in crushed products finer than 300 um. Beneficiation tests indicate the material is amenable to processing by traditional gravity and flotation techniques.

Jan 1, 1991

By J. A. Sanhueza

The environmental regulations and terms issued by the Chilean Government for all copper concentrate smelters have been a very important reason for permitting project developments that drastically decrease the sulfur emissions due to the pirometallurgycal copper process. A remarkable case of the Hernan Videla Lira Copper smelter, located on the Copiapó Valley and very near some housing-sets of a city of high development, are described. Results of this project's implementation of the control and reduction of off gas emissions, the control and monitoring system, the community conflicts, and the strategy to comply with the demands established by the state environmental institutions, are presented.

Jan 1, 1999

By Takeshi Yoshikawa

For the development of low-cost silicon refining process for solar cells, the present authors have been studying the low temperature refining technique, ?solidification refining of Si with Si-Al melts at 1173 ? 1273K?. In the present work, we have investigated the B removal in that refining, utilizing the segregation effect and also the effect of Ti addition to the melt. Segregation ratio of B between solid Si and Si-Al melt was measured by the temperature gradient zone melting technique and it indicated the B removal fraction would be as much as 90%. Titanium addition to the melt was found to produce the TiB2 precipitation with soluble B in that melt and bring the effective B removal of refined Si to its content of 1ppma.

Jan 1, 2006

By Richard LeSar

Sustainability requires more from engineering than the development of technology. Engineering must also take into account the effects of that technology on the integrated social, economic, and environmental processes that constitute our society. Schumacher introduced the powerful concept of an appropriate technology, by which he meant a technology that is appropriate to the environmental, educational, cultural, and economic situation for which it is intended. While the principles of appropriate technology have been most commonly applied in the developing world, they are equally valid in the developed world as well. In this paper we will review appropriate technology and discuss its role in helping to define a way to think about this broad view of sustainable engineering. We will end by presenting one strategy for introducing the concepts and applications of appropriate technology in an engineering curriculum.

Jan 1, 2010

By Jens Kristen Laursen

In 1999, Molymex S.A. de C.V. (Molymex), Mexico. (a company wholly owned by Molibdenos y Metales S.A. (Molymet), Chile) decided to install the Haldor Topsrae Wet gas Sulphuric Aicd (WSA) process for cleaning of the 4-5% SO2 off-gas from their molybdenum sulphide master in Cumpas, Mexico to produce sulphuric acid. The decision to install a WSA plant was based on the successful operation of a WSA plant at Molymet's molybdenum sulphide roaster in Santiago, Chile since 1993. This paper describes the process layout of the Cumpas plant, the operating experience of the Santiago plant, and the, differences in. process design between the two plants. It will furthermore summarise the applications of the WSA process for other roasting plants and smelters within the non-ferrous. metals industry producing metals such as copper, lead, and molybdenum.

Jan 1, 2002

By Ronald J. Roman

The shrinking core model for coarse particle leaching has been generally accepted as describing the leaching of a copper oxide or sulfide ore. However, when a mixed oxide/sulfide ore-is leached this model can not be used in its simple form because at least two and possibly three separate leaching processes are occurring simultaneously (dissolution of oxide copper minerals, secondary copper minerals and primarily copper minerals). It has been impossible to isolate their individual leaching curves from the recovery/time curve generated by the column leach test. This paper describes a tests program carried out at the Groupo Mexico, Mexicana de Cobre's La Caridad operation in which the individual recovery/time curves for the leaching of copper oxide mineral, secondary copper mineral and primary copper minerals were developed from standard column leach tests. Once the individual recovery/time curves were developed scale-up of the column leach test results to the commercial heap leaching operation is possible by using the shrinking core model.

Jan 1, 1999

By Yong Xian, Zhaohui Sun, Honggang Zhong, Qijie Zhai, Jie Sun

Vacuum refining is admitted as an effective means to remove impurities in the process of alloy smelting. In this paper, Orthogonal and single factor experiments were carried out to investigate effects of multiple factors, such as superheat degree of the melt, degassing time and vacuum degree, on the vacuum refining process. The results showed that the best removal rate of oxygen and nitrogen is up to 82.71% and 61.3%, respectively, due to high vacuum degassing efficiency. It is found that the superheat degree is minimal impact on the deoxidization rate, in addition, nitrogen removal is controlled by the degassing time. The inclusions exist in the AlV55 alloy are mainly composed of oxides and vanadium-nitrogen compounds.

Jan 1, 2015