Phase equilibrium and minor element distribution between FeO _x -SiO₂-MgO-based slag and Cu₂S-FeS matte at 1573 K under high partial pressures of SO₂

Abstract

As part of a fundamental study of copper smelting processes using oxygen or oxygen-enriched air as a blowing gas, phase equilibrium and distribution of minor elements between copper matte and SiO₂-saturated FeO _x -SiO₂-MgO-based slag containing 5 to 10 wt pct MgO have been investigated at 1573 K under the SO₂ partial pressures of 10.1, 50.7, and 101.3 kPa. The copper and sulfur solubilities in the slag were found to be independent of $p_{SO_2 }$ when the matte grade was specified, and this behavior was ascribed to the constancy of $\left( {{{p_{O_2 } } \mathord{\left/ {\vphantom {{p_{O_2 } } {p_{S_2 } }}} \right. \kern-\nulldelimiterspace} {p_{S_2 } }}} \right)$ against $p_{SO_2 }$ at a given matte grade. When the distribution ratio of a minor element (X) between the slag and matte phases was defined as L ^s/m_x =(wt pct X in slag)/{wt pct X in matter}, L ^s/m_x for arsenic, antimony, and bismuth at a given matte grade increased with increasing $p_{SO_2 }$. On the other hand, the distribution ratio of silver at a given matte grade was almost constant against $p_{SO_2 }$.