Oxidation of molten copper matte
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I.
INTRODUCTION
MANYattempts have been made to improve the operation of copper flash smelting and continuous copper smelting processes, such as the gas blowing of higher oxygen concentrations in the flash smelter,~ injection of concentrate with coal addition in continuous copper smelting, 2 high-pressure injection in the PS (Peirce Smith) converter, 3 etc. Though the thermodynamics of the copper smelting process have been investigated by many workers, 4-7 there have been very few studies on the kinetic aspects of the process. Knowledge of the kinetics should be important for the improvement of the processes under operation and also for the development of new processes. Ajersch and Toguri8 reported on the oxidation of molten copper and copper sulfide, and Asaki, Ajersch, and Toguri 9 studied the oxidation of molten iron sulfide. As a continuation of kinetic studies of copper smelting, the present work studied the oxidation of molten copper matte. The oxidation of molten copper matte is a main reaction in the converting process. It also takes place in the lower portion of the reaction shaft of Outokumpu type flash smelter, where the droplets of copper matte formed by the fusion of copper concentrate are oxidized during the descent. The extent of matte oxidation varies with the vertical and radial positions in the reaction shaft depending on the oxygen partial pressure. The path of oxidation of copper matte is qualitatively anticipated from the thermodynamic considerations. However, the residence time of the sulfide particles in the reaction shaft is extremely short and only fast reactions take place during the descent. Knowledge of to what extent the matte droplets are oxidized during the descent when enough high partial pressure of oxygen is available is important for the modeling study of flash smelting process. Then, the oxidation experiment was carded out by using a slender alumina sample tube so that the rate of gaseous Z. ASAKI, Associate Professor, Department of Metallurgy, S. ANDO, Graduate Student, Department of Metal Science and Technology, and Y. KONDO, Professor Emeritus, are with Kyoto University, Sakyo-ku, Kyoto 606 Japan. Manuscript submitted June 18, 1986. METALLURGICALTRANSACTIONS B
diffusion could be calculated, and the overall rate of oxidation was compared with the rate of gas diffusion. Under the condition of gas diffusion control, the equilibrium is almost reached at the gas/melt interface and the rate of chemical reaction is much higher than gas diffusion rate. By using this technique, the path of fast reaction of molten copper matte was followed.
II.
EXPERIMENTAL
A. Sample Preparation Copper matte was prepared by melting a mixture of weighed amounts of iron sulfide and copper sulfide in an alumina sample tube of 3 mm ID and 25 mm length in an Ar gas stream. The total amount of copper matte used in each experimental run was about 80 mg and the depth of the molten copper matte was about 2 mm. The iron sulfide was prepared by heating a mixture of iron powder of 99.99 pct purity and distille
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