Modeling studies of fluid flow below flash-smelting burners including transient behavior
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INTRODUCTION
IN flash smelting, concentrate burners are used to mix dry sulfide flotation concentrates with flux, fuel, and preheated oxygen-enriched air. In the reaction shaft, the sulfides ignite at some distance from the burner and are oxidized to form slag and matte (or blister). The type of burner affects the ignition point, amount of recirculation in the shaft, the position of any dead zones, accretion formation, dust formation, magnetite formation, and indeed the entire furnace operation. The recirculating gases transport heat to the top of the shaft and promote ignition. The main purpose of the concentrate burner is to mix and distribute the particles in the hot gas. The three main types of burners (venturi, distributor, and jet-flow) achieve these goals in different ways. To promote mixing, the venturi burner makes very little use of the particles, but generates turbulence from the venturi shape. At higher oxygen enrichment (higher concentrate/gas ratios), the venturi burner cannot perform adequately, as there is insufficient turbulence generated. The distributor burner is better than the venturi burner, as it does not solely rely on the energy in the primary gas stream to promote mixing. In the disI.D. SĖUTALO, Project Metallurgist, is with WMC (Olympic Dam Corporation) Pty. Ltd., Roxby Downs, South Australia 5725, Australia. J.A. HARRIS, Senior Lecturer, is with the Mechanical Engineering Department, James Cook University of North Queensland, Townsville, Queensland 4811, Australia. F.R.A. JORGENSEN, Manager of NonFerrous Metal Processing, is with the Division of Minerals, Commonwealth Scientific and Industrial Research Organisation (CSIRO), Clayton South MDC, Victoria 3169, Australia. N.B. GRAY, Associate Professor and Deputy Director of the G.K. Williams Cooperative Research Centre for Extractive Metallurgy, is with the Department of Chemical Engineering, The University of Melbourne, Parkville, Victoria 3052, Australia. Manuscript submitted February 19, 1997. METALLURGICAL AND MATERIALS TRANSACTIONS B
tributor burner, mixing is also promoted by the high-pressure secondary gas stream and the distributor. The jet-flow burner with a dispersing cone in the throat forces the particles to mix with the gas. Both the distributor and jet-flow burners can perform adequately at higher oxygen enrichment. The features of burner design that control concentrate dispersion into the process gas are not fully understood. Water models of flash furnaces have been used to study the flow patterns in the reaction shaft using time-lapse and video streak photography. Smith[1] used a 1:20-scale water model of the Kalgoorlie Nickel Smelter (KNS) flash furnace, equipped with four burners, to study the flow patterns in the reaction shaft and settler. He investigated the effect of turning individual burners off, rotating the burner arrangement, and altering the height of the reaction shaft. Nguyen et al.[2] extended this work using time-lapse streak photography to determine point velocities in a 1:14-scale water model of the KN
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