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Room: Salon 6
Location: Clarion Plaza Hotel
Session Chairs: Hani Henein, Advanced Matls. and Proc. Lab, University of Alberta, 606 Chem-Min Eng. Bldg, Edmonton, AL T6G 2G6; Thomas Battle, DuPont White Pigments and Mineral Products, Edge Moor Plant, Edge Moor, DE 19809
2:00 pm
BENEFITS OF MEMBRANE SURFACE FILTRATION IN THE NON-FERROUS INDUSTRY: Christine E. Kafka, W L. Gore and Associates, Inc., 101 Lewisville Road, P.O. Box 1100, Elkton, MD 21922-1100
Stricter particulate emission regulations and the competitive requirements to produce metal as economically as possible are driving the non-ferrous processing industry to focus on cleaner and more efficient technologies. One area of interest is the air cleaning systems. Presently, there are many different air filtration technologies employed by the industry. Fabric filtration systems with expanded polytetrafluoroethylene (ePTFE) membrane filters are increasingly being chosen to provide optimum performance over conventional depth filtration. The selection of filtration technology greatly affects the performance of the baghouse and process. The ePTFE membrane surface filtration provides consistently higher airflow and longer filter life, while also providing the additional benefit of the lowest particulate emission of any fabric filtration media. Membrane filtration provides these benefits in concentrate drying, primary and secondary smelter and converter baghouses, with case histories around the world.
2:25 pm
PHYSICAL EXAMINATION AND HANDLING OF WET AND DRY C60: K. Lozano1, X. Sheng1, A. Gaspar-Rosas2, F. Chibante3, E. V. Barrera1, 1Rice University, Dept. Mechanical Engineering and Materials Science, P. O. Box 1892, Houston, TX 77251; 2Paar Physica USA, Houston, TX 77388-8909; 3Nanotechnologies of Texas, Houston, TX 77081
The structure-property relationships of C60 dissolved in decahydronaphtalene (decalin) and a petroleum solvent viscous standard (PSVS) were studied. This work was motivated mainly by the interest to improve fullerene dispersion in powder processing by wet methods. Measurements of solubility, density, viscosity and elasticity were conducted varying the concentration level of C60. A Decalin solution was mixed with Cu powder and the C60 dispersion and Cu grain-size growth were evaluated. Decalin can dissolve 1.9 mg/ml of C60 while the PSVS dissolves 0.15 mg/ml. The viscosity behavior shown by both solutions was Newtonian, with a small increase in viscosity as a function of fullerene concentration. The elastic portion of the solvents did not change with fullerene concentration. The samples prepared by wet methods showed less C60 agglomerates. This presentation will also emphasize the aspects of handling the fullerene powder in wet and dry methods. This work was supported by National Science Foundation DMR-9357505.
2:50 pm
ON THE IMPROVED FLOWABILITY OF COHESIVE POWDERS BY COATING WITH FINE PARTICLES: R. Mei1, J.F. Klausner2, H. Shang1, and E. Kallman2, 1Department of Aerospace Engineering, Mechanics, and Engineering Science 2Department of Mechanical Engineering, University of Florida, Gainesville, FL 32611
Poor flowability of cohesive powders is the source of frequent concern in powder handling in many industrial processes. Coating of fine particles on the surface of primary powder particles can be applied to improve powder flowability. In this paper, we examine quantitatively the effect of coating fine particles on the cohesion force between primary powder particles by extending the JKR theory to include the effect of coating particles on the force-displacement relationship. It is shown that the cohesion force between two primary powder particles in the presence of a fine coating particle is directly proportional to the size ratio of the coating particle to the primary powder particle resulting in a drastic reduction in the cohesion force. Through discrete element simulation of powder flows the improved flowability is demonstrated. The effect of coating on improving the flowability is also quantified by comparing the measured angles of repose at a static condition and the flow rates of the gravity driven flow through a funnel for powders with and without particle coating.
3:15 pm
POROSITY CALCULATION OF PARTICLE MIXTURES: Z.P. Zou1, A. B. Yu1, P. Zulli2 , School of Materials Science and Engineering, University of New South Wales, Sydney, NSW 2052, Australia; 2BHP Research - Newcastle Laboratories, P. O. Box 188, NSW 2287, Australia
A packing of particles is an assemblage of particles and is widely encountered in many industries. Porosity or packing density is known to be the simplest and most accessible parameter in characterising particle packing. It is very useful to develop a method for predicting the porosity and related packing properties of particulate mixtures for property and/or process control. Particle characteristics affect porosity mainly via three factors: (dimensionless) particle size distribution, particle shape and absolute particle size, giving various packing systems from the simple (coarse) spherical particle packing to the complicated system involving fine and non-spherical powders. Consequently, the modelling of the relationship between porosity and particle characteristics may be carried out by considering these three factors. This paper presents a mathematical model developed on the basis of some simple and physically sound concepts in this direction, with examples provided to confirm its applicability.
3:40 pm
A STUDY OF THE MECHANISMS OF POWDER ENTRAPMENT IN PACKED PARTICLES: D. Pinson1, A.B. Yu1, P. Zulli2, M. J. McCarthy2. 1School of Materials Science and Engineering, University of New South Wales, Sydney, NSW 2052, Australia; 2BHP Research - Newcastle Laboratories, P.O. Box 188, NSW 2287, Australia
Gas-powder-liquid multiphase-phase flow in packed beds can be found in many industrial applications. One typical example is the flow in the lower part of a modern ironmaking blast furnace with high pulverised coal injection, which includes an upward flow of gas and (unburnt) coal and downward flow of liquid iron and slag in a coke bed. Understanding the mechanisms governing the powder entrapment in packed particles is an important step toward the modelling of such a flow system. This paper presents a study of the mechanisms through a model experiment in which the form and volume of deposits, i.e. the entrapped powder, can be visualised. It is found that the contact point between particles plays an important role in capture of powder, and the presence of a liquid may significantly increase the powder entrapment and lead to a dramatic increase in gas pressure drop. The effects of variables relevant to the blast furnace process, such as liquid properties, gas, powder and liquid flowrates, and the size ratio between (flowing) powder and (packed) particle have been studied, and correlations have been formulated for modelling purposes.
4:05 pm
RECENT DEVELOPMENTS IN THE TECHNIQUE FOR CHARACTERIZING THE SHAPE, SIZE, AND TEXTURE OF METAL POWDER GRAINS: B.H. Kaye1 , L.C. Paquette2, 1Professor of Physics, 2Research Associate, Department of Physics, Laurentian University, Sudbury, Ontario, P3E 2C6
Computer image analysis continues to develop rapidly and the falling costs and increasing power of personal computers make it possible to characterize the shape, angularities and, for rough texture powder grains, the fractal dimensions. New data on the characterization of various types of metal grains will be presented. Assessment of the size distribution of powders using diffractometers and time of flight spectrometers is making it possible to characterize the shape and size of metal powder grains in real time. Again, new data demonstrating the utility of this type of information for the powder metallurgist will be presented. Some of the newer size characterization equipment uses small quantities of powder samples and new procedures for taking representative samples from free fall tumbler mixers will be reviewed and sampling data presented.
4:30 pm
CHARACTERIZING THE FLOW OF METAL POWDERS USING THE CONCEPTS OF FRACTAL GEOMETRY AND CHAOS THEORY TO INTERPRET THE AVALANCHING BEHAVIOR OF A POWDER DEPENDENT ON POWDER GRAIN CHARACTERISTICS:B. H. Kaye1, L.C. Paquette2, 1Professor of Physics, 2Research Associate, Department of Physics, Laurentian University, Sudbury, Ontario, P3E 2C6
The avalanching behavior of a portion of powder in a slowly rotating disc can be related to the flow behavior of powder in processing equipment. To interpret the observed avalanching behavior a new data processing procedure has been developed which permits instant visual recognition of shifts in the flow behavior. This can be caused by changes in powder grain structure; additives (such as glidants) and changes in ambient properties (such as humidity). Data on these four metal powders of different size, shape and texture will be presented.
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