Sponsored by: Jt. EPD/MDMD Synthesis, Control, and Analysis in Materials Processing Committee, EPD Process Fundamentals, Aqueous Processing, Copper, Nickel-Cobalt, Pyrometallurgy, Lead, Zinc, Tin Committees, MSD Thermodynamic & Phase Equilibria Committee
Program Organizers: R. G. Reddy, Department of Chemical and Metallurgical Engineering, University of Nevada, Reno NV 89557; S. Viswanathan, Oak Ridge National Lab., Oak Ridge, TN 37831-6083; J. C. Malas, Wright-Patterson AFB, OH 45433-6533
Monday, PM Room: A16-17
February 5, 1996 Location: Anaheim Convention Center
Session Chairpersons: D.G.C. Robertson, Department of Metallurgical Engineering, University of Missouri-Rolla, Rolla, MO 65401; S. Seetharaman, Division of Theoretical Metallurgy, Royal Institute of Technology, Stockholm, Sweden
2:00 pm
THE BOUNDARY LAYER AND SOLID-GAS REACTIONS:
Fathi Habashi, Department of Mining and Metallurgy, Laval University, Quebec City, Canada G1K 7P4
Solid-gas reactions of metallurgical importance can be classified into three groups: 1) physical processes, e.g., drying and sublimation, 2) chemical processes, which may be an addition or a thermal decomposition reaction, and 3) electrochemical processes, which may be addition, oxidation-reduction, or displacement reactions. Examples are given and the role of the boundary layer is emphasized.
2:25 pm
CONVERSION OF ILMENITE TO TiC AND Fe USING A NON-TRANSFERRED ARC THERMAL PLASMA REACTOR: Patrick R. Taylor, Ilaria Accorsi-Lamb, Department of Metallurgical and Mining Engineering, College of Mines, University of Idaho, Moscow, ID 83843. Milton Manrique, Department of Materials Science, Simon Bolivar University, Caracas, Venezuela
Ilmenite concentrate and methane were fed into a non-transferred thermal plasma reactor to produce ultrafine powders of TiC and Fe. Free energy minimization plots were used to predict the feasibility of the reaction. An estimate of the optimum molar ratio between the ilmenite concentrate and methane was made and used in the experiments. Argon-hydrogen mixtures were used as plasma gases. Power input, carrier gas flow rate, and feeding rate were the variables studied on the behavoir of the system. A mathematical model to describe the distribution pattern in the hot zone of the reactor was formulated. The product has been characterized by x-ray diffraction and atomic absorption. It was found that minor amounts of Ti2O3, Fe2C, and free C are also present in the product. Finally, the possibility of directly uniaxial pressing and sintering to produce a Fe-TiC based cermet is discussed.
2:50 pm
A THERMODYNAMIC AND KINETIC ANALYSIS OF THE CARBOTHERMIC REDUCTION OF KALGOORLIE PENTLANDITE CONCENTRATE IN THE PRESENCE OF LIME: Jillian Spindura, Animesh Jha, Department of Materials Technology, Brunel University, Kingston Lane, Uxbridge UB8 3PH, England
This work investigates the carbothermic reduction of the complex sulphide mineral, pentlandite, in the presence of lime. The effects of change in temperature and the use of different carbon sources are studied and the role of these variables on the reducibility of pentlandite mineral is discussed. The microstructures of the heat-treated pellets are examined using X-ray diffraction and scanning electron microscopy techniques. The latter analytical method also allows any variation in the morphology and composition of the metallic phases formed, with temperature, to be considered. The kinetics of the reduction process is studied and the magnitude of the overall activation energy is determined from the plots of percentage reduction versus time.
3:15 pm BREAK
3:25 pm
THERMAL DECOMPOSITION OF ZIRCON IN A NON-TRANSFERRED ARC THERMAL PLASMA FLOW REACTOR: Milton Manrique, Judith C. Gomez, Department of Materials Science, Simon Bolivar University, Caracas, Venezuela; Patrick R. Taylor, Department of Metallurgical and Mining Engineering, College of Mines, University of Idaho, Moscow, ID 83843
The thermal decomposition of zircon concentrates in a non-transferred arc thermal plasma flow reactor was investigated. The plasma torch was operated using argon-helium and argon-nitrogen mixtures as plasma gases. The effect of power, feed rate and zircon particle size was studied. Products were characterized by XRD, SEM, TEM and chemical analytical techniques. The average size of the ceramic product is in the submicron range. Free energy minimization plots were used to predict the behavior of the system under different operating conditions. A kinetic model to describe the different stages of the thermal decomposition process is proposed. The results of this investigation showed a significant segregation process where zirconia-rich product is collected in the reactor while silica-rich product is collected in the filter. TEM analysis indicated that silica vapor is condensed on the surface of the zirconia particles.
3:50 pm
REDUCTION PROCESS OF IRON ORES IN A TWO-STAGE FLUIDIZED BED SYSTEM: Yoon-Bong Hahn, Yeon-Ho Im, Jae-Sung Lee, Department of Chemical Engineering and Technology, Chonbuk National University, Duckjin-Dong 1Ga, Chonju 561-756, Korea
A mathematical model has been developed to analyze and predict the prereduction and final reduction process of iron ore particles in a two-stage fluidized bed system. This model includes the degradation phenomena of iron ore particles sized 1-5 mm to elucidate its effect on reduction degree. Although the degradation of particles is dependent on the kind of iron ores, it was found that 80 to 90% of overall degradation occurs in the prereduction stage mainly due to thermal stress at reaction temperature. The degradation of particles in the final stage is not much, but is mainly due to interparticle collision and abrasion. In spite of different kinds of ore, the reduction degree showed similar results. It was found that to obtain a targeted reduction degree, it is important to control the residence time of particles in reactor R1 in which particles larger than 0.5 mm are fluidized. Optimum range of residence time was 15-20 minutes in the prereduction stage; 30-35 minutes in the final reduction stage.
4:15 pm
LIME ENHANCED REDUCTION OF MOLYBDENITE WITH CARBON: R. Padilla, M.C. Ruiz, Department of Metallurgical Engineering, University of Concepción, Concepción, Chile; H.Y. Sohn, Department of Metallurgical Engineering, University of Utah, Salt Lake City, UT 84112-1183
A thermodynamic analysis of the MoS2-C-CaO system has been carried out in
order to understand the reduction of molybdenite with carbon in the presence of
lime. Reduction experiments have also been carried out with various mixtures of
MoS2:C:CaO in the temperature range of 900-1200[[ring]]C. It was found that the
reduction of MoS2 in this system proceeds through the formation of intermediate
oxidized molybdenum species MoO2 and CaO*MoO3, which subsequently undergo
reduction by CO. In this respect the experimental findings are in agreement
with the thermodynamic analysis. For mixtures of MoS2:C:CaO = 1:2:2 at a
temperature of 1200[[ring]]C, complete conversion of MoS2 can be obtained in
less than 20 min; the corresponding product species were metallic Mo, Mo2C, and
CaS.
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