Dissolution of solid magnetite in Fe-S-O melt
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I.
INTRODUCTION
DISSOLUTION of solid magnetite in matte is important in the pyrometallurgical processing of copper concentrate. In the flash smelting process, for example, copper concentrate is partly oxidized in the vertical shaft of the furnace, and a considerable amount of magnetite is formed. The dissolution rate of the formed solid magnetite is a key to successful operation of the process. Formation and dissolution of magnetite in reverberatory furnace and converter were studied by Schuhmann ~ using available thermodynamic data, and the behavior of magnetite in the operation of reverberatory furnace was discussed by several investigators. 2,3.4 Very few kinetic studies have been reported, however, on the dissolution of solid magnetite. Kaiura and Toguri 5 measured the dissolution rate of magnetite pellet immersed in the melts of iron sulfide and mixed copper-iron sulfide and reported the following results of basic importance: the dissolution rate decreased with increasing oxygen concentration in the Fe-S-O melt and with increasing Cu2S content in the FeS-Cu2S melt. The overall rate of dissolution was determined by natural convective mass transfer. The thickness of boundary layer of natural convection varies with the position on the pellet surface, causing a difficulty in the kinetic analysis. It is known, on the other hand, that when a cylinder is rotated in liquid, turbulent flow is developed in the liquid above the Reynolds number of about 100, and the concentration profile of diffusing species in the boundary layer is the same over the entire surface of cylinder in the vertical direction. 6'7'8The effect of natural convection on mass transfer is negligible under this condition. 7 It is intended in the present work to measure the dissolution rate of rotating magnetite rod immersed in a sulfide melt. Copper matte is regarded as a quaternary Cu-Fe-S-O melt, and the ternary Fe-S-O melt is a basic system of the most importance. This ternary melt was chosen, and Z. ASAKI, Associate Professor, and Y. KONDO, Professor, both with the Department of Metallurgy, and M. SHIIKI, formerly Graduate Student, and H. DOI, Graduate Student, are with Kyoto University, Kyoto 606, Japan. H. KUSUNO, formerly Graduate Student, is with Shunan Works, Nisshin Steel Company, Shin-Nanyo 747, Japan. H. KATO, formerly Graduate Student, is with Manufacturing Engineering Research Center, Komatsu Ltd.. Hirakata 573, Japan. Manuscript submitted May 21, 1985.
METALLURGICALTRANSACTIONSB
the dissolution rate of magnetite was measured in the present work. H.
EXPERIMENTAL
A. Sample Preparation Magnetite rod used in this study was prepared by sintering magnetite powder of 99.9 pct purity and about 0 . 3 / z m in mean particle diameter. An amount of 50 g of magnetite powder was mixed with 30 ml of deionized water, and the paste was molded to a rod by using a glass tube of 8 mm ID. The magnetite rod was dried for 2 hours at room temperature. Then it was heated at 370 K for 2 hours and at 1573 K for 6 hours in Nz gas stream. The sintered magnetite
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