The rate of antimony elimination from molten copper by the use of Na 2 CO 3 slag
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10/31/03
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The Rate of Antimony Elimination from Molten Copper by the Use of Na2CO3 Slag MITSURU TANAHASHI, ZHIJIAN SU, KUNIHIKO TAKEDA, HONG YONG SOHN, and CHIKABUMI YAMAUCHI The rate of Sb elimination from molten copper by the use of Na2CO3 slag was measured at 1523 K. The results obtained under the present experimental conditions show that Sb in molten copper is eliminated in a tri-valent or a penta-valent form, depending on the oxygen concentration at the slag-metal interface, and its elimination rate increases with increasing initial oxygen concentration in molten copper. The overall elimination rate of Sb is affected by the stirring condition of the molten copper, which indicates a rate control by mass transfer in that phase. The mass-transfer coefficients of Sb and oxygen in molten copper at 1523 K without external stirring were determined, respectively, to be km,Sb 4.0 (0.9) 105 m # s1 and km,O 1.3 (0.3) 104 m # s1 based on the mass balances of Sb and oxygen in the molten copper and slag phases and the equilibrium relation of the Sb elimination reaction at the slag-metal interface.
I. INTRODUCTION As a result of the high consumption of copper, the availability of high grade copper concentrates has greatly decreased in recent years. A direct consequence of this decrease is the increasing demand for the use of complex raw materials that contain large amounts of impurities such as Sb and As that are harmful to the electrical and mechanical properties of copper. These elements have a strong tendency to cathodically deposit with copper in the electrolytic refining process. Current smelting and converting processes are not capable of removing these impurities to sufficiently low levels. In view of this, the application of Na2CO3 slag to the elimination of impurities from molten copper as an alternative method has been investigated. In previous thermodynamic studies, the distribution ratios of various impurities between the Na2CO3 slag and molten copper, LX {defined as (mass pct of X in slag)/[mass pct of X in molten copper], X: an impurity element}, have been measured experimentally.[1,2,3] In particular, Yamauchi and co-workers established a principle for obtaining LX by calculation. By the application of this calculation method, LX values of the impurities X Sb,[4–9] As,[8,10] Sn,[11] Te,[12] Se,[12] Fe,[13,14] Si,[15] P,[15] Zn,[16] Ni,[16] and S[17] were successfully evaluated and reported as func-
MITSURU TANAHASHI, Assistant Professor, and KUNIHIKO TAKEDA, Professor, are with the Department of Materials Science and Engineering, Graduate School of Engineering, Nagoya University, Nagoya, Aichi 464-8603, Japan. Contact e-mail: [email protected] ZHIJIAN SU, formerly Research Associate, Department of Materials Science and Engineering, Graduate School of Engineering, Nagoya University, is Lecturer, Department of Thermal Engineering, School of Materials and Metallurgy, Northeastern University, Shenyang 110006, People’s Republic of China. HONG YONG SOHN, Professor, is w
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