Measurements of oxygen pressure in a copper flash smelting furnace by an EMF method
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I.
INTRODUCTION
IN recent years, the multi-phase equilibria in copper pyrometallurgy can be well understood qualitatively as well as be described quantitatively by the accumulation of thermodynamic data. Yazawa ~'2 has emphasized the availability of sulfur-oxygen chemical potential diagrams to copper smelting. Based on a thermodynamic principle that the equilibrium state corresponds to the one which minimizes the total Gibbs energy of the system, Goto 3'4 and Bj6rkman and Ericksson5 have calculated the equilibrium compositions of copper production processes. These theoretical investigations can give industrial engineers the equilibrium oxygen pressure, which is one of the most important parameters in the actual copper smelting processes because conventional copper production is based on oxidation of iron and sulfur in copper concentrates. However, the quantitative comparison of the theoretical oxygen pressure mentioned above with that measured in an actual furnace has not been reported hitherto. Since the pioneering study of Kiukkola and Wagner, 6 galvanic cells employing ZrO2 solid electrolytes have been extensively used as an analytical means of studying pyrometallurgical reactions by many investigators. Moreover, oxygen probes with ZrO2 solid electrolytes have been developed for monitoring oxygen content in liquid steel and are nowadays the necessities in steelmaking processes. In the copper production processes, however, the oxygen probes have been scarcely used, whereas oxygen pressure is an important factor as described above. The present work was carried out to study the variation of oxygen pressure in a copper flash smelting process. Oxygen pressures in the reaction shaft and in the settler, of which the flash smelting furnace is composed, were measured with the commercial oxygen probes. On the basis of the present measurements, the characteristics of the concentrate-burner on the combustion of copper concentrates in the reaction shaft and the redox reaction regulating the oxygen pressure which prevails in the slag phase of the settler zone are discussed. As for the measurements of oxygen pressures in the actual nonferrous smelting furnaces, a few investigators have NOBUMASA KEMORI, YUKIO SHIBATA, and MUTSUO TOMONO are Metallurgical Researcher, Superintendent at PyrometaUurgical Section, and General Manager, respectively, Toyo Smelter, Sumitomo Metal Mining Co. Ltd., Funaya, Saijo, Ehime, Japan. Manuscript submitted July 24, 1984. METALLURGICALTRANSACTIONS B
reported their results derived by emf measurements of galvanic cells. Floyd et al.7 investigated oxygen potential variations throughout a nickel flash smelting process. Kozuka8 studied the applicability of the commercial oxygen probes to the copper flash furnaces and the Mitsubishi process as well as to an Imperial Smelting furnace.
II.
EXPERIMENTAL
A. Principle The galvanic cell (I) used in this study is described schematically as Fe, FeO/ZrO2 + MgO/O in slag or matte.
(I)
When the ionic transference number for oxygen in the solid oxide electro
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