Kinetic study on the reaction of solid silica with molten matte
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I.
INTRODUCTION
IN copper smelting,
it is generally believed that the molten matte quickly reaches equilibrium with the slag, and many equilibrium thermodynamic models have been developed to estimate the composition of slag and matte in the smelting process, successfully providing a global picture of the processes, m2~ In addition, many attempts have been made to increase the production in flash smelting and continuous smelting processes. At higher production rates, the rates of magnetite dissolution into the molten matte and of the slag formation by the reaction of solid silica with molten matte become important factors in the successful operation of smelting and converting processes. The behavior of magnetite in copper smelting has been discussed by several investigators, I3-6~ and kinetic studies on magnetite dissolution in the molten matte have been reported by Kaiura and Toguri I71 and Asaki et al. t81 The physical chemistry of copper smelting slag has also undergone intensive investigation by many researchers, including copper loss in the slag and distribution of minor elements between matte or metal and slag, and these results were reviewed extensively by Mackey. [91 However, no research work has been reported on the kinetic aspect of slag formation. This might be due to the difficulty in the measurement of the rate of slag formation. The following two mechanisms may be responsible for slag formation: first, the direct reaction of solid silica with molten matte and, second, the dissolution of solid silica in slag followed by a reaction between the slag and matte. In the present work, the rate of slag formation by direct reaction of solid silica with molten matte was measured from the decrease in the diameter of a SiO2 rod rotated in molten matte. This technique was also used in the measurement of the dissolution rate of Z. ASAKI, Professor, T. OISHI, Associate Professor, and Y. KONDO, Professor Emeritus, are with the Department of Metallurgy, Kyoto University, Kyoto 606, Japan. Y. CHIBA, formerly Graduate Student, is with Itami Works, Sumitomo Electric Industries, Ltd., Itami 664, Japan. Manuscript submitted December 12, 1988. METALLURGICAL TRANSACTIONS B
solid magnetite previously, i81
II.
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EXPERIMENTAL
A. Sample Preparation A transparent quartz glass rod 5.5 m m in diameter and 30 m m in length was used in the present work. This quartz glass rod was quickly crystallized to form tridymite and quartz when it was immersed in the molten matte, as will be discussed in Section I I I - A . The molten mattes used were of a ternary Fe-S-O system and of a quaternary Cu-Fe-S-O system and were prepared from a powder of FeS, Fe304, and Fe of 99.9 pct purity and Cu2S powder of 99.5 pct purity. Weighed amounts of these powders were mixed and fused in an alumina crucible at 1493 K in an Ar gas stream. B. Apparatus and Procedure The experimental apparatus is described elsewhere, t81 A quartz tube of 4 6 - m m ID and 940-mm length was used for the reaction tube, and it was heated in
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