(Special session/Open call for public) Challenge to unexplored copper extraction technology -understanding smelting reaction, utilization of unused by-products, and so on-

[1K0506-12-04] [Student presentation:Doctoral course] Effect of FeS concentration on SO₂ formation at Cu₂S-FeS matte/magnetite interface investigated by in-situ observation

○Seung-Hwan Shin¹, Sakiko Kawanishi¹, Sohei Sukenaga¹, Junichi Takahashi², Hiroyuki Shibata¹ (1. Tohoku University, 2. SMM Co., LTD)

Chairman:Masahito UCHIKOSHI (Tohoku University)

Keywords:copper smelting, copper loss, magnetite, matte, in-situ observation

The stagnation of magnetite (Fe₃O₄) at the slag/matte (Cu₂S-FeS) interface can occur in the copper smelting process using a flash furnace. The magnetite inhibits the absorption of the suspended matte in the slag phase into the matte phase, which leads to copper loss. Therefore, the rapid removal of the magnetite by its dissolution into the matte can greatly contribute to reducing copper loss. However, the interfacial phenomena between magnetite and matte are complicated, and the effect of SO₂ gas formation at the interface on the reaction rate has never been studied. In addition, the behavior of SO₂ gas formation may depend on the matte composition, which varies by the grade of the copper ore. In this study, we aim to clarify the reaction behavior by direct observation at the high-temperature (1200℃) interface through the magnetite thin film by focusing on the slight transparency for the visible light of the magnetite. The reaction behavior of the matte/magnetite interface was investigated as a function of the FeS concentration in matte, and the dissolution rate of magnetite was also evaluated.

As a result, the formation of SO₂ bubbles was observed at the interface, and the gases stayed even though they were agglomerated. As the FeS content in the matte increased, the size of the gases at the interface decreased, and the dissolution rate of magnetite increased. We revealed that the formation and stagnation of SO₂ gas significantly lowered the reaction rate between magnetite and matte. It should be a harmful phenomenon to generate a large amount of copper loss.