Copper removal from carbon-saturated molten iron with Al2S3-FeS flux

Copper removal from carbon-saturated molten iron to Al2S3-FeS flux was experimentally investigated in the temperature range from 1473 to 1573 K. The maximum copper distribution ratio between the Al2S3-FeS flux and the ferrous alloy was about 28 at the composition where the molar ratio of Al to Fe in the flux was around 2. The distribution ratio was no less than 25 as long as the copper content of the flux was less than 10 mass pct. The sulfur content in the ferrous alloy in equilibrium with the Al2S3-FeS flux was higher than that obtained by using Na2S-FeS flux, and it was concluded that the high copper distribution ratio of the Al2S3-FeS flux was brought about by the high activity coefficient of FeS in the flux. In experiments for recovering copper from the flux, copper in Al2S3-FeS-Cu2S flux was reduced by metallic aluminum at 1473 K. The FeS in the flux was primarily reduced and, after that, the copper was recovered in the form of Cu-Al-Fe alloy. The residual copper content in the flux could be decreased to less than 1 mass pct when the aluminum content in the alloy was higher than 40 mass pct. A process for copper removal from molten iron is proposed, which uses successive contacts between the Al2S3-FeS flux and molten iron at several stages with counterflow operation. It is suggested that 1 mass pct Cu in molten iron can be reduced to approximately 0.1 mass pct Cu using 100 kg flux/ton iron; the amount of aluminum required for the iterative use of the flux is about 10 kg/ton iron. By the recycling use of this Al2S3-FeS flux, it is suggested that copper removal from molten iron using the sulfide flux can be more effective.