1997 TMS Annual Meeting: Monday Abstracts

INTERNATIONAL SYMPOSIUM ON PROCESSING AND HANDLING OF POWDERS AND DUSTS: Session I: Injection of Powders and Dusts

Session Chairs: Gordon Irons, Dept. Matls Sci. and Eng., McMaster University, 1280 Main St West, Hamilton, Ontario L8S 4L7; John Pusateri, Technical Center, Horsehead Resource Dev., 300 Frankfort Road, Monaca, PA 15061

8:30 am

AN OVERVIEW OF THE INJECTION OF POWDERS AND DUSTS INTO MOLTEN METALS: Gordon A. Irons, Department of Materials Science and Engineering, McMaster University, Hamilton, Ontario L8S 4L7 Canada

The science and technology of powder injection has evolved from its start in the desulphurization of iron over 20 years ago. The inherent advantages of powder injection are: rapid reaction rate, good mixing, the ability to handle fine materials, flexibility and low capital cost. The fundamental engineering science related to the fluid mechanics of injection, and the associated thermodynamics and kinetics of the processes will be reviewed. Due to the above advantages, this technology is finding application in the recycling of in-plant dusts and other secondary materials, and in the non-ferrous industry. Some of these developments will be highlighted.

9:15 am

IMPROVING NON-FERROUS METAL CONTROL THROUGH AUTOMATED POWDER INJECTION: R. J. Liguori, VanDeMark Metals and Alloys, Inc., One North Transit Road, Lockport, NY 14094; D.W. Hoyle, Hickman, Williams, and Company, Technicarb Division, 40 Port Avenue, P.O. Box 872, Monroe, MI 48161

This paper describes results obtained from a new and patented control process designed to automate powdered additions via subsurface injection into a molten metal furnace. The process automatically receives spectrometer data, compares it to targeted values and accordingly calculates, weighs and pneumatically feeds the additives into the metal furnace by subsurface powder injection. Current installation and trials indicate alloy savings and improved metal control. Results of injection with many different powders injected in industrial applications are discussed.

9:45 am

FLASH CONVERTING OF MK (CHALCOCITE) CONCENTRATE--AN OVERVIEW: G.J. Morgan, A.A. Shook, J.K. Brimacombe, and G.G. Richards; The Centre for Metallurgical Process Engineering, The University of British Columbia, Vancouver, BC Canada V6T 1Z4; New Technology Development, BHP Steel, Wollongong NSW, Australia 2526; Cominco Research, Trail, BC Canada V1R 4L8

Flash converting of MK concentrate (Cu2S) was considered as an option for the process flowsheet modifications at Inco's Copper Cliff operations. The flash converting of chalcocite was known to have problems, such as the generation of large amounts of dust, so a comprehensive research program was undertaken at the Centre for Metallurgical Process Engineering, University of British Columbia to examine the process. This paper is a compilation of the results of the project, some of which have been published elsewhere. The mechanism and kinetics of the combustion of individual particles of MK were determined, and dust generation criteria were established. The flash converting flame was mathematically simulated, and dust generation regions within the flame were identified. Pilot plant trials were conducted, confirming that the dust generation rate could be affected (reduced) by altering the burner configuration, and thus the flame characteristics.

10:15 am BREAK

10:30 am

DENSE PHASE PNEUMATIC INJECTION FOR FINE MATERIALS: Robert G. Goffin, Paul Wurth Ltd., 3310 South Service Road, Burlington, Ontario L7N 3M6, Canada

Pneumatic injection of various fine materials such as metallic concentrates, fluxes and fuels into pyrometallurgical vessels has become an important practice. Injection is an evolutionary step from pneumatic conveying - the receiving vessel is now a metallurgical process unit instead of a storage unit. Proper injection system design must integrate conveying, injection, metallurgical process and physical constraints, as well as the limitations of specific material characteristics. Dilute phase pneumatic conveying requires large quantities of conveying gas in order to move material. Load ratios in the order of 10:1 (weight of solid gas:weight of conveying gas) are typical. In order to eliminate the problems associated with dilute phase (including extreme pipeline and component abrasion, excess conveying gas, etc.) steady development has been made in the application of dense phase (load ratios substantially higher than 25:1) pneumatic conveying and injection technology. Load ratio selection is dependent upon many factors including specific material characteristics and system requirements. This paper will outline the advantages of dense phase pneumatic injection technology and will present successful and reliable pyrometallurgical applications.

11:00 am

COAL PARTICLE INJECTION AND DEVOLATILISATION UNDER RAPID HEATING CONDITIONS: J. Beeson, V. Sahajwalla, G. Belton, School of Materials Science and Engineering, University of New South Wales, Sydney, Australia; BHP Research, Newcastle Laboratories, Newcastle, Australia

New developments in the metallurgical industry, such as iron bath smelting processes and pulverised coal injection into blast furnaces involve coal injection and devolatilisation under rapid heating conditions. These new technologies employ coal particle heating rates around 104°C/sec. Under these conditions the volatile matter released cannot be established from standard analysis and this can have a significant effect on the process. For example the volatile matter released, which is in excess of that from standard analysis, may lead to excess gas in the top space of a bath smelter. When the efficiency of the reactor relies on a fine balance of post combustion reactions, the increase in release of volatile matter may lead to a decrease in the efficiency of the reactor. In pulverised coal injection to blast furnaces, the amount of volatiles released, and the time taken for this release, influences the combustion behaviour of the coal and char. In this study, the injection and devolatilisation of three size fractions of various coals into a drop tube furnace was investigated. The surface mean diameters of each size fraction were 92µm, 121µm, and 172µm. Four coal types were investigated, sub-bituminous, bituminous, semi-anthracite and an anthracite. These were injected at temperatures of 1000°C, 1200°C, and 1400°C. The ash content and volatile matter remaining in each of the chars was determined in order to calculate the volatile yield using the ash tracer method and the rate of volatiles release. An apparent activation energy for the release of volatiles was calculated. The results show a strong dependence of the activation energy for volatile release on coal crystallite size, as determined by X-ray diffraction. Hence the crystallite size could be an important characteristic of coals that is significant for coal selection for the new technologies in the metallurgical industry.

11:30 am

PREDICTION AND MEASUREMENT OF THE TIME-AVERAGED VELOCITIES OF INERT PARTICLES SUSPENDED IN GAS-STIRRED LIQUID BATHS: H. Pham, D.E. Langberg, M. Nilmani, G.K. Williams Cooperative Research Centre for Extractive Metallurgy, University of Melbourne, Parkville, Victoria 3052 Australia

The Digital Particle Image Velocimetry (DPIV) technique was used to measure the instantaneous velocity distribution of polyvinyl chloride particles suspended in an upright cylindrical water bath (0.218 m diameter) agitated by injection of air through a top-submerged centric lance. The time-averaged particle velocity and kinetic energy distributions were obtained from the instantaneous velocity data. The effects of gas flowrate (3.3 10-5 - 5 10-5 Nm3/s), liquid depth (0.164-0.196 m), fractional lance submergence (60-90%), and particle diameter (50-80 µm) were investigated. The magnitudes of the particle velocities and kinetic energies increased with increasing gas injection rate, and increasing lance submergence. Variation of the liquid depth had minimal influence on the particle behaviour under the conditions studied. Steady state liquid phase flowfield simulations using a commercial Computational Fluid Dynamics package were combined with a dynamic force balance on individual suspended particles to predict the time-averaged particle velocities. Satisfactory agreement was found between the predicted and measured particle velocities, outside the bubble plume region. The particle velocities were integrated with time to predict the trajectories and residence times of particles introduced into the flowfield at different positions. Particles introduced near the plume region were predicted to have much shorter residence times than particles released near the primary recirculation vortex.