Evolution of Size and Chemical Composition of Copper Concentrate Particles Oxidized Under Simulated Flash Smelting Condi
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SINCE its commercial implementation in the past century,[1] the flash smelting process of copper concentrates has been the subject of continued research. This is because a number of phenomena occurring in the reaction shaft of the process are yet not well understood.[2] The elucidation of the fundamental aspects governing the behavior of the flash smelting reactor may help optimize its operation in terms of energy requirements, the quality of the molten products obtained, and MANUEL PE´REZ-TELLO, VI´CTOR R. PARRA-SA´NCHEZ, VI´CTOR M. SA´NCHEZ-CORRALES, and AGUSTI´N GO´MEZA´LVAREZ are with the Department of Chemical Engineering and Metallurgy, University of Sonora, Blvd. Luis Encinas & Rosales, Hermosillo 83000, Mexico. Contact e-mail: [email protected] FRANCISCO BROWN-BOJO´RQUEZ is with the Department of Polymers and Materials, University of Sonora. ROBERTO A. PARRA-FIGUEROA, EDUARDO R. BALLADARES-VARELA, and EUGENIA A. ARANEDA-HERNA´NDEZ are with the Department of Metallurgical Engineering, University of Concepcio´n, Concepcio´n 4070386, Chile. Manuscript submitted September 7, 2017. Article published online January 31, 2018. METALLURGICAL AND MATERIALS TRANSACTIONS B
its potential impact on the environment, among other issues. Over the last decades, extensive experimentation has been conducted on the flash smelting[3–17] and flash converting[18–21] processes by means of stagnant- and laminar-flow reactors. As a result, the reaction path originally proposed by Kim and Themelis[10] and further modified by Jokilaakso et al.[11] and Yli-Pentila et al.[20] has been widely accepted as a descriptive model which explains most of the experimental observations made under controlled laboratory conditions. The model is shown schematically in Figure 1 and is discussed in detail in the literature,[11,20,21] thus only a brief description is provided here. Upon entering the reactor, the initial particles are first heated up by the gas phase by interphase heat transfer and the reactor walls by radiation. The oxidation starts at the particle surface, forming a porous shell of oxides surrounding the unreacted core of sulfides. Because the oxidation reactions are highly exothermic, particle temperature increases rapidly until eventually the melting point of the sulfides is reached. Under such conditions, the sulfur dioxide gas produced by the oxidation accumulates within the molten core and increases the internal pressure in the particle. The gas then pushes the oxide
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shell out causing particle bloating. When the internal pressure overcomes the resistance of the oxide shell, the particle undergoes fragmentation at an extent which depends on the local conditions in the reactor. An alternative path is possible when the heating rate of the initial particle is so high that it becomes fully molten before any significant oxidation occurred in the particle. In such a case, the initial droplet may disintegrate violently, possibly due to pyritic decompositions that release gas. This produces many small droplets which f
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