Mathematical modeling of sulfide flash smelting process: Part I. Model development and verification with laboratory and
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I.
INTRODUCTION
I N the flash smelting process, fine particles of dry sulfide concentrate and flux are injected into the furnace with oxygen-enriched air, forming a particle-laden turbulent jet. The concentrate particles are quicl~ly heated to the temperature at which sulfide particles undergo ignition. As the particles travel down the reaction shaft within the turbulent flow, they exchange momentum, mass, and energy with the surrounding gas. Eventually, the molten particles settle to the furnace bottom and are divided into molten slag and matte layers. In spite of the increasing industrial stature of the process, the design of a flash smelting furnace remains largely an art. This is mainly due to the difficulty of understanding the complex interactions of the individual subprocesses taking place in a flash fumace. In order to enhance the systematic understanding of the overall process, a reliable mathematical model would be very helpful. Such a model can also be used to predict the behavior of the complex reacting particle-laden turbulent gas jets with a minimum amount of experimental work. It is only very recently that attention has been directed to the mathematical modeling of the flash smelting process. The previous studies on mathematical modeling of the flash smelting process have assumed the flame to be a one-dimensional (l-D) stream, tl,2~ a two-dimensional (2-D) free jet, t31 or a 2-D confined jet. t4] Themelis and co-workers ]1,2J developed a 1-D mathematical model to describe the transport phenomena occurring in the flash smelting process. They assumed that Y.B. HAHN, formerly Graduate Student, Department of Metallurgical Engineering, University of Utah, is Research Engineer with Lucky Metals Corporation, Seoul, Korea. H.Y. SOHN, Professor, is with the Department of Metallurgical Engineering, University of Utah, Salt Lake City, UT 84112-1183. Manuscript submitted December 13, 1988. METALLURGICAL TRANSACTIONS B
the reaction of sulfide droplets was controlled by the combination of mass transfer of oxygen to the surface, diffusion through the reacted layer, and interfacial chemical reaction. The effects of phase transformation and particle fragmentation on the rate of flash oxidation of sulfides were incorporated. They considered only 1-D axial flow of the gas and particles, neglecting the radial expansion of the jet as well as the radial dispersion of particles, t2j Due to the 1-D nature of the model, the radial dispersion of fluid properties, the contribution of turbulent diffusion to the gas-phase momentum, the turbulence effect on the flow field, the effect of particles on turbulence, and the dispersion of particles due to turbulent fluctuations could not be described. Fukunaka et al.[3] carried out a modeling study on the flash smelting of pyrite particles based on the previously studied behavior of a free gas jet with the aid of correlation equations. Their model was limited only to the fully developed downstream zone. The upstream region, in which particles are ignited and undergo thermal decompos
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