Mathematical modeling of sulfide flash smelting process: Part III. Volatilization of minor elements
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INTRODUCTION
IN a flash-smelting process, as particles travel down the reaction shaft within the turbulent jet, they exchange momentum, mass, and energy with the surrounding gas. During this exchange, the elimination of minor elements to the gas phase also takes place. The behavior of arsenic, antimony, bismuth, and lead is of great importance during copper-smelting operations. These elements can adversely affect the mechanical properties of the product copper and are also a major concern as environmental pollutants. Basic studies on the behavior of these elements in the Noranda process 11'21and Pierce-Smith converting t3-61 have been reported in recent years. Several investigators analyzed the distribution of these elements in the settler region of the flash-smelting furnace, tT] Others reported a pilot-plant study on the behavior of some minor elements during flash smelting tSl and flash converting, t9,1~ Chaubal m] developed a model describing minor elements behavior during oxidation of chalcopyrite concentrate or copper mattes in a batch reactor. In this model, reaction kinetics and thermodynamics are combined. Chaubal et al. tlsj also predicted the behavior of minor elements in the flash smelting of copper concentrates and the flash converting of copper mattes. The objective of this study was to extend the comprehensive mathematical model developed by Hahn and Sohn t~4,~5~ to the prediction of minor element behavior inside the flash-furnace shaft during copper flash smelting incorporating the thermodynamic analysis of Chaubal. m~ In this new model, the minor element behavior is described in combination with turbulent transport phenomena, chemical reactions, and thermal radiation in a flash-furnace shaft. K.W. SEO, formerly Graduate Student, Department of Chemical Engineering, University of Utah, is Senior Research Scientist, Korea Institute of Science and Technology, Seoul 130-650, Korea. H.Y. SOHN, Professor, is with the Department of Metallurgical Engineering, University of Utah, Salt Lake City, UT 84112-1183. Manuscript submitted July 24, 1990. METALLURGICALTRANSACTIONSB
MODEL BASIS
The behavior of minor elements in a flash smelter can be described by considering the following: tt2,~3j (1) sulfur removal from the concentrate particles; (2) the variation of gas and particle temperatures in the reactor shaft; (3) the elimination of minor elements to the gas phase in the reactor shaft; and (4) the distribution of the minor elements between the molten phases in a particle. Hahn and Sohn t14,~51developed a mathematical model to describe major transport and reaction phenomena (not including minor element volatilization) taking place in a flash-furnace shaft, depicted in Figure 1. Using their overall mathematical model, the gas-phase concentrations of minor elements were calculated in this work with the PSI-CELL model that was previously applied to other species, such as oxygen and sulfur dioxide, t14,~5,~61However, the effects of minor elements on the momentum equation, particle number density, and pa
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