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By Sung-Mo Jung

Experiments were carried out on a system with artificially prepared slags in a graphite crucible, in order to examine the possibility of recycling BOF slags produced in the steelmaking process. More than 80% of FeO and P2O5 was reduced within 20 minutes and the FeO reduction rate was greater than that of P2O5. P2O5 reduction began after more than 60% of FeO was reduced. Increasing slag basicity enhanced the reduction of FeO and P2O5. Temperature also improved slag reduction. The overall reduction rate was controlled by the chemical reaction at the slag/carbon interface. The reduction rates of FeO and P2O5 were second and first order with respect to their respective contents. Most of the reduced phosphorous is believed to vaporize in the form of P2 gas.

Jan 1, 2006

By A. F. Sidorov

A method of improving mineral recoveries from ores by modifying the physical and chemical properties of minerals using radioisotope radiation was tested. It was observed that irradiation modifies mineral cell sizes, changes the crystal structure of some minerals, reduces the sulfur content 1 to 1.5 % in sulfides, changes the zeta potential, alters the surface properties of mineral grains I and produces other changes. Preliminary tests indicate that accelerated electron treatment of ores in connection with mineral processing has a potential for improving mineral recoveries by flotation and by magnetic separations.

Jan 1, 1989

By R. Cheng

The kinetics of the solvent extraction of ythium from HCl solution with mono-2-ethyl hexyl phosphonic acid mono-2-ethyl hexyl ester (HEHEHP) have been studied using a rotating diffusion cell (RDC). The effects of rotation speed, pH, ymium and extractant concentrations and temperature on the rate of extraction were examined. The rate of extraction of ythium appears to be controlled by an interfacial reaction of metal ion and extractant. The concentration of the latter is determined mainly by diffusion through the membrane. The contributions of the rates of diffusion in the diffusion layer, diffusion in the membrane and chemical reaction at the interface to the overall rate have been calculated on the basis of a kinetic model.

Jan 1, 1992

By Erwin Flender, Preben N. Hansen, Peter R. Sahm

"Until now FDM-Techniques have been widely used for Modeling Solidification Processes in Castings. Often a rigid, regular type of enmeshment (cubes, , --) have been used. This has the advantage of low CPU-costs, but the disadvantage of a zig-zag presentation of the interface between the casting and the mold. The last point is the reason why FEM-Techniques, giving the possibility of a true presentation of the shape in the enmeshment, are increasingly used. The disadvantage is the high CPU-costs. In this paper, a technique is presented, which uses the FDM-Mesh with the zig-zag presentation of shape and ADI-Algorithms to calculate temperatures and gradients. The new idea is that the calculated parameters are not presented related to the mesh in which they are calculated, but displayed using the true shape of the casting. Such an advantage of both low CPU-costs and shape correct presentation of the calculated results are achieved. IntroductionThe main reason for using a regular type of enmeshment is that it gives the possibility, via ADI-Algorithms, of obtaining a very fast FDM-Technique. The technique presented by P.R. Sahm and P. N. Hansen (1984), and also used by E. Flender (1985), is numerically so stable that average time steps, at least 200 times larger than the limit given by the explicit FDM-Technique, can be applied. To obtain reasonably good results, average time steps in the range of 20 to 50 times the explicit limit seems to be applicable. It should be pointed out,however, that FDM-Techniques can be used on arbitrary nets, the disadvantages being the same as for the FEM-Techniques. This has, among others, been discussed by P.R. Sahm and P.N. Hansen (1984)."

Jan 1, 1986

By Ana E. Bohé, Georgina De Micco, Gastón G. Fouga

"In this work the reaction between several manganese oxides and chlorine is investigated in the range of temperatures between 650 and 950ºC. The reaction path for the chlorination of MnO is established, which involves recrystallization of high valence manganese oxides (Mn3O4 and Mn2O3) followed by its chlorination. For this reason, to understand the reaction of MnO, the chlorination of Mn3O4 and Mn2O3 has also been studied. The starting temperature for the reaction of these oxides is determined by non isothermal thermogravimetric measurements. The effect of temperature is analyzed, under our experimental conditions the rate of reaction is mass transfer controlled. The activation energy for the volatilization of manganese chloride is obtained which is in good agreement with volatilization enthalpy of MnCl2.IntroductionMany oxide ores which have manganese in their composition undergo chlorination processes during the extraction of refractory metals such as Ti, Hf and Nb. Although several works related with chlorination of manganese oxides were reported, there is no information about the kinetics or mechanism of the manganese oxide chlorination reactions. Okahara et al. studied the chlorination of manganese oxides and established that they react easily above 250ºC. Furthermore, they observed that chlorination of high order oxides is more difficult when there is not a reducing agent [1]. Ivashentsev studied the chlorination of manganese oxides using Cl2(g), CO(g) + Cl2(g) and COCl2(g). He established that the reaction of MnO started at 130ºC with formation of MnCl2(s), he also observed recrystallization of manganese sexquioxide [2]. Finally, the chlorination of manganese nodules from the ocean was studied by Murthy and Reddy [3] with the aim of obtaining valuable metals such as Mn, Co, Ni and Cu. They studied the influence of several parameters like temperature, carbon percentage, particle size and chlorine flow rate in the extraction process."

Jan 1, 2008

By Bo Jiang, Lianyun Liu, Hongmin Zhu, Kai Huang

"Watermelon peel is selected as a novel adsorbent to remove Pb(II) from aqueous solution. A simple saponification process is proposed to modify the peel and the adsorbent is characterized by SEM and FTIR. The effects of pH, contact time, initial concentration of Pb(ll), biosorbent dosage and temperature on adsorption of Pb(II) are investigated. Different models are used to fit experimental data. These models indicate that the adsorption process follows the Langmuir model and pseudo-second-order model. The maximum adsorption capacity obtained from Langmuir model is 1.05mol kg-1 for the prepared sorbent. Equilibrium time is attained in 5-10 min for the studied concentrations. The watermelon peel can be used as an effective and low-cost biosorbent for removal of Pb(ll) from aqueous solution.IntroductionRecently, removal of heavy metal ions from industrial effluents by biosorption has become a very attractive topic, since the more serious pollution issues caused by heavy metals emerge frequently, and more strict requirements for its control are called upon by society [1,2]. In this case, most conventional purification technologies are not suitable due to poor cost-effectiveness [3]. For example, chemical precipitation by alkaline reagents usually can not decrease the metal ion concentration below the permissive levels, and also it will produce a large amount of sludge containing toxic metals. Membrane separation techniques can realize deep purification of wastewater easily, although its operating cost is usually high. Thus, considering the high effectiveness, low cost and free-sludge operation, bisorption has become a promising technique in water treatment [4]. The most important thing for this technology is the synthesis of a suitable biosorbent, whose adsorption properties will determine the removal efficiency and economic cost for the whole process. Watermelon is one of the most popular fruits for mankind for its delicious flavor. Usually, the watermelon is consumed mainly for its edible pulp, and its peel is discarded or only used as feed for livestock. Considering the pectin contained in the watermelon peel, just like that in orange wastes in the reported literatures [3], the idea of using it as the raw material to prepare the biosorbents for heavy metal ions removal from the aqueous solution was evaluated in this study."

Jan 1, 2012

By Hector M. Henao

To provide thermodynamic data for converting nickel matte to liquid nickel at high temperature, an experimental study was conducted on the phase equilibrium between the Ni-S alloy and the FeOX-SiO2, FeOx-CaO, and CaO-A12O3 base slag in a magnesia crucible and the CaO-Al2O3-MgO slag in an alumina crucible. All experiments were carried out at 1773 K under controlled pso2 of 0.1 atm and po2 in a range between 5x10- and 10-5 atm by using CO-CO2-SO2 gas mixtures. The dissolution of nickel in the slag was found to be minimum for the CaO-Al203¬-MgO slag with a molar ratio of NCaO/NA1203=1.7. The solubility of nickel in this slag at p02 of 6x10 atm (just before the precipitation of solid NiO) was 4 mass%. This result suggests that a CaO-A12O3 base slag could be used in converting Ni-S melt to nickel while minimizing nickel losses to the slag.

Jan 1, 2002

By C. Sui

A common objective in many Cu/Zn concentrators is to reduce the loss of Zn to the Cu-concentrate. One suspected source of the problem is accidental activation of sphalerite by heavy metal ions such as lead. One method of quantifying surface metal ion concentration is extraction with ethylene-diamine-tetra-acetate (EDTA). This was used to survey Cu-rougher flotation at three Cu/Zn concentrators: Les Mines Selbaie, Falconbridge's Kidd Creek division, and Hudson Bay Mining and Smelting Although all have less than 0.2% galena in the ore, Pb ions proved an abundant extractable metal. From a laboratory study a model of surface coverage of lead species generated by an ore was combined with an estimate of surface concentration of lead required to activate sphalerite to explore the possibility of accidental activation. Ores with Pb-grade as low as 0.1% can produce sufficient Pb to be a potential problem.

Jan 1, 1999

By Kazuyuki Kakegawa

The sintering characteristics and the change in the compositional distribution in the PbTiO3 PbZrO3-Pb(Mgl/3Nb2/3)O3 system during the sintering process by spark plasma sintering (SPS) method were examined. They were compared with those by a normal sintering method. The densification by the normal sintering was slow even at high temperatures, When SPS method was employed, much lower temperature and shorter period resulted in sintered bodies having almost the theoretical density. As expected in normal sintering, the compositional distribution decreased as the sintered density increased. On the contrary, the change in the compositional distribution by SPS was much smaller than that in the normal sintering. This sintering characteristic of SPS suggested a possibility of fabrication of sintered material having a desired compositional distribution.-

Jan 1, 2003

By P. S. Seryogin

R & D works supported by industrial-scale tests, which were carried out by joint efforts of the OAO Gipronickel Institute and MMC ?Kola? engineers, have accomplished with the production of 90?95% metallized nickel powder in tube furnaces (NPTF), with its ?active fraction? (AF) to be further used for decopperization of nickel electrolyte by cementation. Consistently positive results obtained in the course of the lab and industrial experiments have allowed the Severonickel Combine management to effectively replace all activated nickel powder (ANP), which was then employed for cementation, with the AF, having activity over 80%, and eventually shut down the entire operation of gaseous reduction. Ever since the developed technology has been implemented, its annual economic effect exceeds 2 ml. dollars.

Jan 1, 2006

By Gerson de Araújo Filho

This paper shows the use of tires as fuel to be employed into blast furnaces. The tires can substitute coal or even charcoal in the blast furnaces tuyeres. The injection into tuyeres, besides the contribution for energy generation, can also produce gas for iron oxide reduction. The tires, as powder to be injected into blast furnaces, contributes for an environmental use of this waste, which helps to obtain a high value product as well. So, the advantage of using such material is that it is waste and has lower cost for preparation. The obtained results showed that the tires have good combustibility. This one was obtained in a model that simulates the same conditions occurring in the blast furnaces tuyeres; these used raw materiais include tires and mixtures of tires with coal or even with charcoal.

Jan 1, 2006

By John O. Marsden

The past fifteen years have seen a number of important developments in copper hydrometallurgy, including the commercial application of biological heap leaching of secondary (chalcocite-dominant) copper ores, the commercial demonstration of chalcopyrite concentrate leaching technology using pressure leaching and biological processes, and the application of novel configurations of solution extraction circuits. Significant emphasis is now being placed on the development of effective stockpile leaching practices for primary ores (chalcopyrite and bornite-dominant mineralization). Some of these developments have been highly successful, and will pave the way for further development and commercialization. Others have been less successful. These developments are reviewed in the context of the metal price cycle and trends for the future are identified.

Jan 1, 2006

By Motoyasu Sato

Highly pure pig irons were produced in a multimode microwave reactor from powdered iron ores with carbon as a reducing agent in the nitrogen atmosphere. The grains in compacted powder absorb microwave energy selectively. Microwave-matter interaction creates thermal non-equilibrium state microscopically and enhances chemical reactions and the phase mixing at the grain boundaries very rapidly. The visible light spectroscopic techniques was used to monitor the progress of the reactions. Up to 650°C, the heated powders radiate the continuous spectrum of blackbody emission. The small non-equilibrium hot spots rise, move and finally burst in to brighter light emitting from all over the surface at 650°C. CN molecules and Fe (I) atoms were identified in the recorded spectrum. These bursts are similar to the ?ignition propagation? normally observed in chemical reactions. The line spectra originated from CO molecules have not been detected yet. The solid-solid reaction could be expected between the iron oxides and carbon to produce CO2 directly. A loss in the sample weight was accelerated during the excess-emission. These are the clear evidence that microwaves cause thermally non-equilibrium state and accelerate reduction process. The reduction of iron ore is completed at 1380°C and relatively very pure pig iron was produced. It should be noted that the impurity level of Mg, S, Si, P and Ti is only 5-10% of what is found in the pig irons produced by modern conventional blast furnaces in the steel industries. The necessary amount of carbon needed was 1/2 compared to conventional blast furnace to produce the unit weight of steel, if we applied renewable energy or nuclear power for the microwave excitations.

Jan 1, 2006

By Jan Petter Maehlen

Solid H-absorbing materials are in focus of ongoing R&D to offer viable solutions for the hydrogen storage and supply systems aimed on use of hydrogen as energy carrier for automotive transportation. Low operating pressures, combined with high gravimetric and volumetric efficiencies, together with fast kinetics of hydrogen release at ambient temperatures (providing conditions for a low energy loss due to decomposition), are the most important features of the ?ideal? H storage material. Hydrides of the light elements are the only possible candidates to build systems with an overall efficiency similar to those accommodating liquid or compressed (700 bar) hydrogen. One promising material from this point of view is aluminium trihydride, alane AlH3 with a gravimetric storage capacity of 10 wt.% H. This work was focused on studies of the crystal structure and thermal decomposition of alane by application of powder synchrotron X-Ray diffraction.

Jan 1, 2006

By Susumu Imashuku

A pseudoternary phase diagram of the BaO?ZrO2?ScO1.5 system is established and the conductivities of the scandium-doped barium zirconate are measured in wet conditions. According to the phase diagram, the molar fraction of scandia in the barium zirconate phase that equilibrates with the cubic zirconia (ZrO2) and scandia (Sc2O3) phase is 0.03. On the composition line, where the molar fraction of barium oxide (BaO) is 0.50, the solubility of scandia into barium zirconate is 0.27 as a molar fraction of scandia. At around 500 °C, the conductivities of scandium-doped barium zirconate are estimated to be almost same as that of yttrium-doped barium zirconateThe activation energies for bulk proton conduction in scandium-doped barium zirconate (0.57 eV for BaZr0.90Sc0.10O3-d) are higher than that of yttrium-doped barium zirconate (0.44 eV for BaZr0.90Y0.10O3-d). In addition, the bulk conductivity of scandium-doped barium zirconate in this study is 10 times higher than the reported conductivities in the temperature range of 75 °C to 300 °C.

Jan 1, 2006

By Coida D. S. Renata, Gerald Okwuchi Onyedika, Moura E. B. Esperidiana, Graca Valenzuela-Diaz, Martin Chidozie Ogwuegbu, Francisco R. Valenzuela-Diaz, Amauche Cyprian Achusim-Udenko

This work aims to incorporate Mgbee clay, vegetal fibre (Costus afer) in recycled low density polyethylene (rLDPE). The incorporation of clay and vegetal fibre in rLDPE was carried out using a twin screw extruder machine and the nanocomposites were obtained. The nano composites were characterized by the Young’s modules test, tensile tests, bending test, XRD, SEM, DSC, and TG and other properties evaluated. The results of morphological and thermal properties showed a good interaction between the clay, and rLDPE as compared to neat rLDPE.

Mar 1, 2017

By C. Zografidis, K. Karalis, E. Devlin, S. Tabouris

"The main parameters affecting energy and electrode consumption in smelting reduction of Greek nickeliferous laterites in submerged arc electric furnaces (E/F) were investigated. Within this framework, the operational data of E/Fs, such as energy consumption indicators, electrode consumption indicators and chemical characteristics of Fe-Ni and slag, were correlated with the physicochemical characteristics of the calcine, produced by roasting reduction of laterite in rotary kilns (R/Ks), such as reduction degree, temperature, chemical composition and granulometry. The results obtained provide a significant input for further research on the modelling of the roasting reduction – smelting reduction process, which is a critical tool for energy optimization.IntroductionThe two main steps of pyrometallurgical treatment of greek nickeliferous laterites for ferronickel production include: i) drying, pre-heating and controlled pre–reduction of laterite ores with solid fuel reducing agents and fuel oil in rotary kilns (R/Ks) for the production of a calcine, and ii) smelting reduction of the calcine in open-bath submerged-arc electric furnaces (E/Fs) for the production of Fe-Ni alloy with 12-16% Ni [1].The energy absorbed from the endothermic reductive reactions of iron, nickel and cobalt oxides (Fe2O3, FeO, NiO and CoO) of the calcine with the remaining carbon in the E/Fs, corresponds to about 16% of the total energy output in the smelting reduction step [1]. This is indicative of the significance of the calcine’s reduction degree for the electric energy requirements in the E/Fs. Moreover, the chemical characteristics and the granulometry of the calcine constitute critical parameters for the energy requirements as well as the smooth operation of the E/Fs."

Jan 1, 2012

By Defeng Zhou, N. Trubaki, Jian Meng, Fanzhi Menga, Xiaojuan Liu, Yanjie Xia

"The microstructure and the electric conductivity of (Ce0.9Nd0.1)1 xMxO2 d (M=Mo, W) solid solutions were investigated. It has been found that their conductivity containing the grain (s gi ), the grain boundary (s gb) and the total conductivity (s t ) at 300°C- 700°C can be ranked as: (Ce 0. 9Nd 0. 1 ) 0.99 W 0.01 02- d (s gi = 0.065 S.cm·1, (s gb = 0.265 S.cm·1, s t = 0.039 S.cm-1) > (Ce0.9Nd0.1)0.99Mo0.01O2- d (s gi = 0.053 S.cm·1, s gb = 0.142 S.cm·1, s t = 0.029 S.cm-1) > Ce0.9Nd0.1 s 2- d (s gi 0.045 S.cm-1, s gb = 0.091 S.cm-1, s t = 0.018 S.cm-1) measured at 700°C. The highest conductivity is obtained in (Ceo.9Ndo.1)0.99W0.01O2 d. These results indicate that (Ceo.9Nd0.1)0.99W0.01O2- d is the most promising electrolyte materials of intermediate-temperature solid oxide fuel cells among (Ce0.9Nd0.1)1-xMxO2- d. IntroductionRare-earth (e.g. La3+, Nd3+, Gd3+ and Sm3l doped ceria-based ceramic materials have been acknowledged to be attractive electrolytes for solid oxide fuel cells operating below 600°C due to their high ionic conductivity [1, 2]. In order to improve ionic conductivity of these electrolytes further, in recent reports [3-6], some aids such as Mo03 [3] etc. in a limited amount can be used which causes extremely high conductivity. For example, Zhou et al. found that with MoO3 doping, the grain boundary conductivity of Nd3+ doped CeO2- d increased notably especially at lower temperatures due to the effect of severely undersized do pants [3]. It is well known that the size of W6+ (rw6+ = 0.60 Å) is close to Mo6+ (rMo6+ = 0.62A) because of lanthanide shrinkage. Thus, rare-earth doped ceria e.g. Nd3+ doped CeO2g with WO3 in a limited amount will be probably good and even better electrolytes. However, much less information is available about these materials. Therefore, in our paper, (Ce0.9Nd0.1)0.99 1-xMxO2- d (M=Mo, W) solid solutions have been prepared and characterized. Much higher conductive electrolytes are found in the series of (Ce0.9Nd0.1)0.99 M0.01O02- d particularly (Ce0.9Nd0.1)0.99W0.01O2- d"

Jan 1, 2012

By Hee Dong Jang

Crystalline metal oxide nanoparticles such as lithium cobalt oxide (LiCoO2) and indium tin oxide (ITO) were synthesized from sprayed droplets of aqueous precursor solution by flame spray pyrolysis. Complete thermal decomposition of the aerosol precursors was obtained at high flame temperature. Molar concentrations of the precursor solution, and the flow rate of combustion gas such as hydrogen, oxygen and air were varied to control particle size, size distribution and crystal structure. The crystalline nanoparticles synthesized were nearly spherical, and their average primary particle diameters ranged from 11 to 35 nm for LiCoO2 and from 8 to 15 nm for ITO.

Jan 1, 2006

By David R. Sadedin

The highly negative Gibbs free energies of hydrogen atom reactions suggest that refractory oxides such as titanium dioxide should be easily reduced by hydrogen atoms. These reactions appear to be most favourable at low temperatures; oxides should be reducible even at room temperature. Since hydrogen atoms are produced in plasmas containing hydrogen a number of investigators have used hydrogen plasmas of various sorts to test these possibilities for reducing refractory oxides, in particular TiO2. None of these attempts has succeeded, a small degree of reduction being achieved in only a thin layer near the surface. A deeper consideration shows that several factors complicate the reactions expected on the basis of the negative Gibbs free energy. One factor is that the back reaction by water molecules produces molecular hydrogen, not hydrogen atoms, and the metal atoms that have been reduced may be immediately re-oxidised. In plasmas there are complications due to diffusion, thermal and charge boundary layers and charged particle reactions. Interpreting the results of hydrogen atom reactions is difficult. Hydrogen is not detectable by electron dispersive spectroscopy and amorphous products are not determinable by x-ray diffraction. Another consideration is economics. The cost of producing hydrogen atoms has a large bearing on the metals for which hydrogen atom reduction may be competitive. In this paper these factors are discussed, some necessary basic studies are highlighted and the general principles of a laboratory reactor are given, together with the results of tests using ZnFe2O4, ZnO and TiO2 as test oxides.

Jan 1, 2006