Fluid dynamics and mass transfer in submerged gas-particle jets
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I.
INTRODUCTION
D E M A N D S for high productivity, higher quality, and lower production costs in steelmaking have led to the development of injection metallurgy, in which high speed submerged gas jets are used to refine liquid metals. 1 The high speed jets provide kinetic energy for stirring and a large gas-liquid surface area for chemical reactions. The flexibility of such processes can be increased by the use of the jet stream to carry reactive particles into the metal bath, for example, in the ladle desulfurization of hot metal or steel. 2 s A powder injection process involves a flowing system of at least three reacting phases. In most cases, the reaction between the liquid metal and the injected powder is of greatest interest, although for some purposes such as the removal of dissolved gases, the reaction between the metal and the carrier gas may also be important. While all injection processes have certain features in common, the designer or operator can, within limits, vary a number of injection parameters to optimize the rate of the reaction which is of greatest importance to a particular process. These parameters include: (1) the velocity of the gas jet, (2) the ratio of powder to gas within the jet, (3) the particle size or other physical characteristics of the injected powder, and (4) the location and orientation of the injection lance. Because the fluid dynamics of submerged gas-particle jets are very poorly understood, and no theoretical model is available to predict the effects of changing parameters on reaction rates in gas-particle jets, this optimization must be performed empirically on a case-by-case basis. In the present study, a water model gas-particle injection system has been used to investigate the effects of changing injection parameters on the fluid dynamics and gas-liquid reaction rates with the intention of developing a general model for reactions during gas-particle injection. Such a model is necessary if the reR. E SINGtt, formerly Graduate Student in the Department of Civil Engineering, Mechanics, and Metallurgy, University of Illinois at Chicago, is now Graduate Student in the Department of Materials Science and Engineering. M~.ssachusetts Institute of I;ecbnology, Cambridge, MA 02139. M. J. McNALLAN is Assistant Professor in the Department of Civil Engineering, Mechanics, and Metallurgy, University of Illinois at Chicago, Chicago, IL 60680. Manuscript submitted September 14, 1982. METALLURGICAL TRANSACTIONS B
suits of small scale laboratory experiments are to be used to predict behavior in industrial scale equipment.
II. FLOW REGIMES IN SUBMERGED (;AS I N J E C T I O N Submerged gas jets which do not contain entrained particles have been the subject of considerable study, both in water models and in liquid metal systems. Two regimes of jet behavior have been observed, one in which large, unstable bubbles are produced at the jet orifice which subsequently break up into a swarm of smaller bubbles, and one in which a steady cone of gas passes out of the orifice and breaks up conti
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