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Session Chairpersons: KNona Liddle, Washington State University; V. Ramachandran, ASARCO, Inc., 3422 S. 700 W., Salt Lake City, UT 84119-4191
THERMAL PLASMA ENHANCED CHEMICAL VAPOR INFILTRATION: Patrick R. Taylor, Banqiu Wu, Edgar E. Vidal, University of Idaho, Department of Metallurgical & Mining Engineering, Moscow, ID 83844-3024
A novel method for chemical vapor infiltration, using thermal plasma technology, has been developed. The use of a thermal plasma source may allow much greater infiltration rates than conventional CVI. Precursors that are fed into the flame region of the plasma are vaporized and forced to flow through a porous preform, at a controlled temperature, where condensation or chemical reactions occur. Exploratory experiments, using silica and methane as precursors and graphite felt for the preform, have been performed. The change in the pressure drop across the preform, as infiltration occurred, is compensated by the use of a vacuum pump on the discharge of the reactor. The product was characterized using SEM and x-ray diffraction. A uniform infiltration rate of SiC was observed along the width of the preform.
SOME KINETIC ASPECTS OF THE GASEOUS CHLORINATION OF TITANIUM-BEARING RAW MATERIALS: C.A. Silva, D.H. Gameiro, V.A. Leao, I.A. Silva, C.S. Paulo, Escola de Minas da UFOP, Departamento de Metalurgia, Praca Tiradentes 20, 35400-000, Ouro Preto, MG, Brazil
The kinetics of chlorination of titanium-bearing raw materials has been investigated. For comparison purposes pellets of controlled macro-porosity, made of analytical grade TiO2 and anatase concentrate (Brazil), have been exposed to different combinations of gas composition - co, CO2, Cl2 , gas flowrate and temperature. A thermogravimetric technique and an adapted grain model have been used in order to assess the influence of the several experimental parameters upon the chlorination behavior.
KINETICS OF OXYCHLORINATION OF CHROMIUM (III) OXIDE: I. Gaballah, N. Kanari, Mineral Processing and Environmental Engineering, Lem, CNRS URA 235, Ensg, Inpl, BP 40, 54501 Vandeuvre, France
The oxychlorination kinetics of pure Cr2O3 with C12+O2 is studied by ThermoGravimetric Analysis (TGA) in non and isothermal conditions up to 1000C. The final reaction product is CrO2Cl2. The reaction Of Cr2O3 with Cl2+O2 chlorination gas mixtures starts at about 500C. The apparent activation energy of the oxychlorination reaction of Cr2O3, as well as the apparent reaction orders with respect to the reactive gases are determined. The reaction rate is maximum for a Cl2/ O2 molar ratio equal to 4.
CHLORINATION: A POTENTIAL APPROACH FOR THE BENEFICATION OF CHROMITE: N. Kanari, I. Gaballah, Mineral Processing and Environmental Engineering, lem, cnrs ura 235, ensg, inpl, bp 40, 54501 Vandeuvre, France
One of the criteria to define the market value of chromite concentrate is its chromium to iron ratio. Changing this ratio for a definite chromite is impossible by physical processing. This study investigates the possibility of increasing this ratio through the carbochlorination of chromite concentrate by Cl2+CO between 500 to 900C. The evolution of the reaction products' characteristics is determined by SEM, XRD and chemical analysis. The carbochlorination of a chromite concentrate at 600C leads to the selective partial elimination of iron allowing a higher Cr/Fe ratio of the treated concentrate. A flow-sheet for the benefication of chromite is suggested.
10:20 am BREAK
ARSENIC VOLATILIZATION FROM ENARGITE CONCENTRATE: R. Padilla, Y. Fan, M. Sanchez, and I Wilkomirsky, Department of Metallurgical Engineering, University of Concepcion, Casilla 53-C, Concepcion, Chile
A thermogravimetric study has been conducted to follow the decomposition and volatilization of arsenic from enargite concentrate in nitrogen and slightly oxidizing atmospheres, Temperature has a large effect on the rate of volatilization of arsenic. Fractional volatilization of arsenic as high as 95% were reached in less than 30 min. at 650°C in nitrogen atmosphere, while in slightly oxidizing atmosphere the same volatilization could be achieved in less than 20 min. It was found that As volatilizes as sulfide in nitrogen atmosphere and as a mixture of sulfide and oxide in atmospheres containing 1% oxygen.
OXIDATION OF COPPER MATTE PARTICLES IN SIMULATED FLASH CONVERTING CONDITIONS: Kirsi M. Rijhilahti, Ari Jokilaakso, Department of Materials Science and Rock Engineering, Helsinki University of Technology, FIN-02150 Espoo, Finland; Hong Yong Sohn, Manuel Perez-Tello, Department of Metallurgical Engineering, University of Utah, Salt Lake City, UT 84112
The oxidation characteristics of solid copper matte particles under simulated Kennecott-Outokumpu Flash Converting conditions are presented. This project is concerned with the determination of the effects of operating variables on the reaction of the particles. Experiments were carried out in a large laboratory-scale flash furnace with 72 wt% Cu matte by varying initial particle size, temperature, oxygen partial pressure, oxygen to matte mass-ratio and residence time. Chemical analysis and optical and scanning electron microscopy were used to study the oxidation, morphology and mineralogy. Fractional conversion and sulfur removal, in general, slightly decreased with initial particle size while higher oxygen to matte mass-ratio mainly resulted in higher fractional conversion and more efficient sulfur removal. The fractional conversion values represented the overall extent of oxidation more closely than degree of sulfur removal.
MICROSCOPICAL STUDY OF ROASTED NICKEL CONCENTRATES PRODUCED IN SIMULATED FLASH SMELTING CONDITIONS: Satu Stromberg, Ari Jokilaakso, Satu Jyrkonen, Department of Materials Science and Rock Engineering, Helsinki University of Technology, Espoo, Finland and Tilna Jokinen, Outokumpu Research Oy, Pori, Finland
Four different nickel concentrates were oxidized in a laboratory scale Laminar flow furnace in simulated flash smelting conditions. The major nickel- and iron-bearing minerals in the concentrates were pentlandite, violarite, gersdorffite, and pyrite and pyrrhotite, respectively. Thermal decomposition, ignition and oxidation behavior of nickel and iron sulfides were examined by using optical and scanning electron microscopy. General reactivity of the concentrates was monitored with sulfur removal which was most effective in violarite-based concentrate. Penlandite-concentrates needed higher experimental temperatures for complete desulfurisation and gersdorffite-based concentrate contained 5 - 10 % of the original sulfur even at the most oxidizing conditions studied (11000C, 50 vol-% O2). The reactivity of the iron minerals were found to depend on the other minerals present in the concentrate. In this paper, observed reaction products and mineralogical changes are presented and preliminary conclusions of possible reaction mechanisms of nickel-bearing minerals are discussed.
THERMODYNAMIC MODELING OF Co-Cu-Fe-Ni-S MATTES AND APPLICATIONS IN THE SIMULATION OF SMELTING PROCESSES: F. Kongoli, A.D. Pelton, Centre de Recherche en Calcul Thermochimique, Ecole Polytechnique de Montreal, P.O. Box 6079, Station Downtown, Montreal (Quebec) H3C 3A7
The Modified quasichemical model has been applied to Co-Cu-Fe-Ni-S mattes. A small set of model parameters was obtained from optimization of experimental data for the binary Co-S, Cu-S, Fe-S and Ni-S systems. The thermodynamic properties of the ternary, quaternary and quinary systems are then predicted a priori by the model with no additional adjustable parameters. Agreement with all available data for ternary and quaternary mattes is within experimental error limits. The parameters are stored as a database of the F*A*C*T thermodynamic computer system and can be used along with other F*A*C*T databases for alloy, slag, speiss and gas phases, and with Gibbs energy minimization software, to simulate equilibria during smelting processes.
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