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By A. G. Cecutti

A brief overview of the known significant health effects of both Nickel and Cobalt will be presented. Some time will be given to the current research activities, especially for Nickel. Emphasis will be placed on some of the controversial issues associated with their health effects.

Jan 1, 1988

By Hui-Gai Li

The fine Ti oxide inclusions precipitated during solidification are favorable for intragranular ferrite nucleation. The oxygen content before solidification affects the composition and size of inclusions. The composition of precipitated inclusions in Mn-Ti alloyed steel was studied by means of thermodynamic calculation and experiment in this paper. The micro-segregation of Mn, Ti and O during solidification was considered in calculation and unidirectional solidification apparatus was employed in experiment to ensure that alloy elements diffused along solidification direction. The results showed that: inclusions are mainly Ti oxide when oxygen content is 10ppm; they are Ti oxide and Mn-Ti oxide when it is 20ppm; Mn-Ti oxide dominates when it is 30ppm. With the increase of oxygen content, the size of inclusions increases. The maximum oxides size is about 3µm from statistical results of experiment.

Jan 1, 2008

The direct removal of lead ions from D2EHPA-kerosene using metallic zinc as the reducing agent was evaluated. The electrochemical process, called galvanic stripping, is a potential alternative stripping technique when standard chemical methods are not adequate. Four parameters found to be important in the rate of lead removal were studied in a factorially designed experiment. The variable evaluated included D2EHPA concentration, temperature, zinc surface area and solution agitation. Temperature and surface area were found to be the most significant, while agitation and D2EHPA concentration had less influence on the reaction. An activation energy of 22.5 Kcal/mole was calculated indicating a chemically-controlled process. The reaction was also sensitive to the concentration of oxygen in the system. The zinc required was considerably in excess of stoichiometry, possibly due to the dissolution and redeposition of lead: In general, the results were encouraging and demonstrated that lead impurities could be removed from D2EHPA using cementation type reactions.

Jan 1, 1995

The cleaning of copper containing fayalite slag using a CuFe alloy was studied under an oxygen pressure ranging from 10-7 to 5 X 10-11 atm at 1200º c. The reduction of copper from fayalite slags by Cu-Fe alloys was found to be very effective. For example, at a P 02 of 10-7 atm, the copper content in the slag was reduced from 4.1 to 0.402 wt. percent after 90 min. of reaction time using a Cu- 5.27 wt. percent Fe alloy. The copper reduction rates were found to be independent of P02 in the gas phase when using Cu-Fe alloys which exhibit an iron activity of greater than 0.4. A mechanism for slag c1eaning is proposed based on the concept that the Cu-Fe alloy lowers the oxygen potential of the slag according to Eq.1 1, fol1owed by the reduction of cuprous oxide by wustite as shown in Eq.2. Here X represents element X in the alloy phase while (X) represents the element in the slag phase. The copper and iron transfer behaviour obtained in this study are explained by a ?Stepwise equilibrium model.

Jan 1, 1985

By S. Suda

Hydrogen storage materials have been investigated for more than 30 years, particularly on metal hydrides. These materials are, however, considered today impractical because of their poor hydrogen capacity measured by mass density and their poor surface properties and characteristics against impurities. Recent R&D activities have been located in new categories of materials such as complex hydrides and chemical hydrides. Among these materials, NaAlH4 (one of alanates), Li-based complex hydride, and NaBH4 (SBH: sodium borohydride) are 3 major candidates as hydrogen storage materials. In the presentation, SBH as a non-reversible on-site but recyclable off-site is described in view of its practical availability as the source of H- (protide) applied for a new type of fuel cell named Direct Borohydride Fuel Cell (DBFC) and H2 (hydrogen) for Proton Exchange Membrane Fuel Cell (PEMFC).

Jan 1, 2006

By Wei Yu, Tiejun Chun, Jian Pan, Deqing Zhu

In this paper, the technology of producing fluxed pellets by using hydrated lime as binder instead of bentonite was carried out. Green balls with 0.8% bentonite and others with 2% hydrated lime were obtained under the same conditions of 1.5% coke, 1.45 basicity and balling at 8.5% moisture for 13 min in disc pelletizer. The properties of two types green balls were as follows: drop numbers of 4.8 to 5.0 times/0.5m, compressive strength of 19.7 to 24.2 N/pellet and thermal shock temperature of 280 to 385?, respectively. Comparing with bentonite as binder, the compressive strength of fired pellets with hydrated lime is elevated by 13.8% and climbs up to 3113 N/pellet under the following conditions: preheating at 1050? for 10 min and firing at 1300? for 15 min. The hydrated lime also improves the metallurgical performance of fired pellets. The reduction index was enhanced from 68.6% to 70.6%, RDI+3.15 increased from 90.1% to 98.8% and reduction swelling index dropped from 22.4% to 7.4%, respectively. Therefore, hydrated lime can not only replace bentonite as binder to enhance the firing behaviors of green balls, but also effectively improve the metallurgical performance of fluxed pellets which can be used as high quality feed for blast furnace.

Jan 1, 2011

By Wenbo Luo, Jilai Xue, Tiepeng Li, Jun Zhu

Sodium silicate solutions for producing silica have been ultrasound treated to enhance the precipitation process in laboratory scale. Higher precipitation rate was found with ultrasound treated solutions than those without ultrasound. The obtained SiO2 powder products were characterized using XRD, SEM, BET and laser particle size analyzer. The particle size distribution and the specific surface area of the powder products varied with the power input level and the processing time of the ultrasonic treatment. The results indicate that the efficiency of the precipitation process can be improved optimally when the ultrasound is conducted into the solutions before the nucleation stage.

Jan 1, 2015

By Pengfu Tan

In order to understand and control the formation of dioxins and furans in iron ore sinter plants and to possibly avoid expensive end-of-pipe removal stages, thermodynamic calculations on the stability of PCDD/Fs have been combined with sinter process modeling by means of kinetic simulations and computational fluid dynamics. Three thermodynamic databases of PCDD/Fs, derived using the Group Additivity approach and two computational molecular modeling methods, MNDO and PM3, respectively, combined with the SGTE database have been used to model the PCDDIF formation and the PCDD/F isomer distributions in iron ore sintering. The results show very similar conditions for the PCDD/F formation using the different databases. Concerning the isomer distributions of toxic PCDD/Fs, the calculated data derived from the MNDO method showed optimum agreement with measured values from industrial furnaces. The thermodynamic calculations also proved that the isomer distributions found in combustion processes are equilibrium values, while the concentration ratio of PCDDs and PCDFs in the wind boxes does not represent an equilibrium state. A CFD model of iron ore sintering was developed including the kinetics of 15 relevant chemical reactions with the aim of describing the temperature fields and the gas flow patterns in the sintering bed. On the basis of these information and experimental observations reported in the literature possible pathways for the PCDD/F formation in sinter plants have been identified: PCDD/Fs are formed in the critical temperature region of 250 to 450°C below the combustion zone, are then carried downwards with the gas and condensed close to the bottom of the sinter bed. Transported to the discharge end with the solid mixture, they are again released into the gas phase when the flame front approaches the bottom. PCDD/Fs are also formed in the last wind boxes when the hot off-gases cool down and reach the critical temperature range. Consequently, methods to reduce the dioxin formation reactions are proposed including inhibitor addition to the sinter feed and off-gas quenching.

Jan 1, 2003

By Hong Ouyang

A unified computational model has been developed for the Bridgman growth processes of B-NiAI and CdTe crystals. To handle the geometrical and physical complexities, a two-level approach has been developed. At the gtobatlevel, conjugate heat transfer, phase change dynamics, and variable material properties along with the realistic geometries and thermal boundary conditions are accounted for inside the entire crystal growth system. Refined calculations are then made within the ampoule, with the boundary conditions supplied by the global simulations. This model can optimize the use of computational source, help understand solidification behaviors, and improve designs of crystal growth system.

Jan 1, 1996

By I. A. H. Schneiderl

Eichhornia crassipes approaches being a scourge in many parts of the world, .choking waterways and hindering transport upon them. At the same time it is known to readily abstract heavy metal ions from water and, thus, aids in the removal of heavy metals found in such waters. This paper considers the possibility of using specific parts of the plant as an inexpensive adsorbent for the removal of heavy metals from contaminated chemical and mining industry waste waters. In particular the root of the plant was found to be an excellent accumulator of 'heavy metal ions including uranium from solution. It is. also suggested that dried roots of the plant ?might be placed in simple bags and used in a very low cost metal ion removal system.

Jan 1, 1995

By Vladimir Panjkovic, Ostrovski. Oieg, Campbell Cripps Clark, John Truelove

"Effects of properties of raw materials and blast on the performance of an iron bath reactor have been examined by a mathematical model. The model consists of three modules: 1) chemical reactions in the gas phase and heat transfer from gas to droplets ejected from the bath; 2) heat losses from the vessel and radiative heat transfer from the freeboard to the bath; and 3) heat and mass balances for the bath. The following parameters of the process are calculated: coal, ore, flux and oxygen consumption, post-combustion ratio and heat-transfer efficiency, temperature and composition of the off-gas, and slag and metal chemistry.IntroductionOne of the anticipated advantages of smelting reduction over conventional ironmaking is the use of lower-grade raw materials. In this work, the effect of-properties of raw materials on the performance of an iron-bath reactor is examined with a numerical model. The model is also used to assess the effect of properties of the blast (flowrate, temperature and oxygen enrichment) and ejected droplets (generation rate, size and ratio of total weights of slag and iron droplets) on the key parameters of the process. In the process coal, oxygen, ore (which may be partly prereduced) and fluxes for specified slag composition are charged to the bath. Slag and iron droplets are ejected from the bath into the gas phase, where they are heated before returning to the bath. Iron droplets undergo decarburisation and reoxidation with CO2 and H2O. Dust is also generated from the bath, and oxygen or preheated air for post combustion is injected from the top of the vessel.The model consists of three modules: 1) reactions in the gas phase and heat transfer from gas to droplets ejected from the bath; 2) heat losses from the vessel and radiative heat transfer from the freeboard to the bath; and 3) heat and mass balances for the bath. The structure of the model and the data exchange between the modules are shown in Fig. 1. The following parameters of the process are calculated: coal, ore, flux and oxygen consumption, postcombustion ratio (PCR), heat transfer efficiency (HTE), off-gas temperature and composition, slag and metal chemistry, and rates of decarburisation and reoxidation of the iron droplets."

Jan 1, 1996

By Lei Wang, Jianjun Wang, Lingen Luo, Zhengbang Li

Dearsenication in molten steel was studied by adding Ca-Fe Alloy-based arsenic removal agent. In order to improve the utilization rate of Calcium Iron Alloy and improve arsenic removal ratio, [O] is less than 0.0005% and [S] is less than 0.0035%, Al is added into the molten steel. In the processes of adding CaO-Al2O3 based alkalinity slag for arsenic removing in molten steel (initial arsenic content is 0.0080%), arsenic removal ratio reaches 50% when Ca-Fe Alloy addition amount is 18%. During the arsenic removal experiment, adding Rare Earth promotes the arsenic removal reaction and makes the arsenic removal more effectively.

Jan 1, 2015

By Qian Xu, Xionggang Lu, Xingli Zou, Zhongfu Zhou, Shuhua Geng, Hongwei Cheng

Herein we report an electrochemical route from oxides (SiO2, TiO2)/sulfide (MoS2)/carbon mixture precursors to Mo-Si-Ti-C composites in molten salt. The electrochemical process was carried out in molten CaCl2 at 800 °C with a potential of 3.1 V, and a graphite-based anode was used in the electroreduction process. The reaction mechanism and the influences of the stoichiometry of the initial mixture precursor on the morphology and phase composition of the final products were investigated. It has been found that Mo5Si3/MoSi2/Mo3Si/Mo, Mo5Si3/MoSi2/Mo2C/SiC, and Mo5Si3/Mo2C/Ti3SiC2/TiC/Mo composites can be electrosynthesized directly from their oxides/sulfide/carbon mixture. The preliminary experimental results suggest that the electroreduction process can be used for the controllable electrolytic production of alloys/carbide-containing composites from oxides/sulfides/carbon precursors.

Jan 1, 2016

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 J. Brent Hiskey, Rebecca Grace Copp

The solvent extraction of yttrium and neodymium from copper pregnant leach solutions (PLS) using Primene JM-T, a primary aliphatic amine, has been studied. Effect of contact time, pH, sulfate concentration, and extractant concentration were investigated using synthetic and actual PLS systems. Standard experimental conditions were 5 minute contact time, pH ~2.5, and 10 % v/v Primene JM-T concentration. Distribution isotherms were constructed for the pure systems and for actual copper leach solutions. Synthetic solutions contained 100 ppm Y and ~75 ppm Nd. Samples of PLS contained 2 - 10 ppm Nd and 14 - 30 ppm Y. Results showed that complete extraction of both yttrium and neodymium occurred within five minutes and at pH values greater than 1. It was also found that sulfate concentration does not inhibit extraction at any concentration. Additionally, the distribution isotherms created show that extraction for these metals can operationally take place in one stage.

Jan 1, 2016

By Roy J. M. van Lier

In industrial aqueous solutions, germanium generally occurs in trace amounts amid high concentrations of other metals, such as zinc, copper and iron. Separation of germanium from these metals as well as its isolation from gallium and indium pose a real challenge to the hydrometallurgist. After a brief discussion of the aqueous chemistry of germanium, this paper reviews the flowsheet of the Apex Mine in Utah. The Apex property was the only mine in the world to be operated primarily for production of gallium and germanium, but apparently closed due to great operating difficulties. Several process variants proposed for the treatment of the Apex ore, including bioleaching methods, are addressed. Following a more general description of the behavior of germanium in hydrometallurgical zinc processing streams, available technology for its recovery from aqueous solutions is summarized. Precipitation, solvent extraction, ion exchange, electrowinning, ion flotation and liquid-membrane separation are all outlined in terms of the aqueous chemistry of germanium. Finally, the production of high purity germanium dioxide and metal is briefly discussed

Jan 1, 1995

By Ximena Diaz

Mercury is one of the most undesirable contaminants in gold bearing ores. During cyanidation mercury cyanide compounds accompany gold in all the extraction and recovery processes. Of course mercury in the carbon eluates creates environmental problems in subsequent refining steps. One possible process alternative for the separation of gold from mercury in such concentrated alkaline cyanide solutions is the selective solvent extraction of gold by undiluted Dibutyl Butyl Phosphonate (DBBP). In order to describe the behavior of mercury during extraction by DBBP, the results from a preliminary research program are presented. In this study, temperature and cyanide concentration have been found to be the most significant variables which influence the separation of gold from mercury by solvent extraction using DBBP. It was found, using plant eluate from a carbon strip, that excellent separation of gold from mercury can be obtained at 60' C with 98% gold recovery and complete mercury rejection in a single stage of extraction. The influence of pH is also discussed in terms of the extraction chemistry. These results complement previous research which described the DBBP solvation extraction of an aurocyanide ion pair. In addition, these results extend our understanding of the alkyl phosphorous ester extraction systems by illustrating that neutral ionic species such as Hg(cN)02sq, can be extracted at low cyanide concentrations, a phenomenon which had not been observed previously for other cyanoanions.

Jan 1, 1993

By Mark H. Hashiguchi

Examination of tensile bar surfaces shortly after destructive testing was conducted to search for clues that would aid in optimization of mechanical properties, especially tensile strength, yield strength and elongation to fracture. Cu-Ni-Si-Cr alloy bars in the as-cast, forged, rolled and extruded conditions were examined. Low ductility bars (<4% Elongation) showed dramatically different features than the fracture surfaces of high strength - high ductility bars (7 to 10% Elongation). Analysis of the fracture surfaces at 15X to 2000X and use of Energy-Dispersive X-Ray Spectroscopy (EDS) identified Ni-Si and Ni-Si-Cr precipitates of varying sizes and morphologies. Thermo-mechanical processing techniques to control the size and distribution of these precipitates show promise in improving the properties and performance of this alloy system and appear to correlate with improvements in the fracture surface morphology.

Jan 1, 2008

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 Marisa Di Sabatino, Michael Phan Knudson, Mari Juel, Eivind Øvrelid

"A p-type Czochralski silicon ingot doped with boron was characterized for resistivity, minority carrier lifetime, interstitial oxygen, and metallic impurities. Analyses show a peak in resistivity and a dip in lifetime both occur 5 cm from the top of the ingot crown. This peak in resistivity deviates from the expected trend based on Scheil's equation for boron distribution. High concentration of interstitial oxygen in this area suggests that other oxygen-related defects, such as thermal donors and precipitates, may also be present here, and the observed peak in resistivity and dip in lifetime could be attributed to such defects. The low lifetime of 15-30 µs at minority carrier density of 7.5 x 1014 cm-3 is likely due to copper contamination.IntroductionSolar energy resources vastly exceed all other alternative energy resources, ensuring that solar power must play a crucial role in the evolving energy market. The economic viability of solar power in competition with other energy resources depends upon finding efficient, cost-effective, reliable, and controlled methods for solar cell production. In this regard, minimizing waste (such as material with unsuitable electrical properties that hinder solar cell performance) is a vital component of making solar cell manufacturing cost-effective. Impurities affect electrical properties of solar cell silicon in different ways (i.e. [1, 2, 3, 4, 5, 6]). In this work we focus on the role of oxygen and metallic impurities. Understanding oxygen impurities in silicon is critical to solar cell development because oxygen has been attributed with influencing critical electrical properties including resistivity and minority carrier lifetime and thereby potentially hindering solar cell performance or rendering material unsuitable for solar cells.[1, 2] Furthermore, oxygen is a common impurity in the standard type of solar cell silicon, Czochralski (CZ) silicon, due to diffusion of oxygen from the silica crucible into the melt during crystallization. [7] This study investigates the effects oxygen impurities have on the electrical properties of p-type CZ silicon."

Jan 1, 2013