Institute of Metallurgy of Ural Department of Russian Academy of Sciences, Yekaterinburg, Russia

E. N. Selivanov, Director

N. I. Selmenskikh, Researcher, e-mail: selm8@mail.ru

“Uralelektromed” JSC, Verkhnyaya Pyshma, Russia

A. I. Popov, Head of the Laboratory of Research Center
A. B. Lebed, Head of the Research Center

Composition of non-metallic inclusions in blister copper in the process of fire refining has been evaluated by optical microscopy and X-ray spectrum microanalysis. Based on data of refining interface (slag/metal) impurities distribution their oxidation sequence has been determined under conditions of “Uralelektromed” JSC. Virgin samples have been selected in the process of copper oxidation, their oxygen content made up 0.47–0.64%. Two oxide inclusions types have been detected — Cu₂O and PbO – Sb₂O₅ – As₂O₅ as well as selenide-tellurides Cu_хSeTeS in the form of copper-suspended particles. Major impurities portion are Cu₂O particles the size of which increases in the process of oxidation from 0.5–4 nm to 10–40 nm. At the same time inclusions containing lead, arsenic, antimony, selenium, tellurium impurities decrease in size from 1–5 to 1–3 nm. In oxide particles PbO – Sb₂O₅ – As₂O₅ lead content reaches 55.3%, antimony 24.8–35.2%, nickel 0.4–1%, arsenic 2.7–9.3% and sulfur 1.1–4.1%. It is assumed that impurities oxidation occurs due to copperdiluted oxygen. Copper selenium-telluride contains, % (mas.): 12.6–18.3 Se, 5.6–11.1 Te, 1.2–4.5 Pb, 0.9–1.5 Sb, 1.0–9.2 S. Based on composition and size of non-metallic inclusions oxides rise rate has been evaluated (υ.) by Stokes and Rybchinsky-Adamar equations. Calculations demonstrated that rise rate of inclusions with the size 2–40 nm changes for Cu₂O from 1.3·10^–6 to 520·10^–6 m/s, and rate of inclusions (υ) Cu₂O – PbO — Sb₂O₅ – As₂O₅ is three times less. Low values of copper oxide particles rise rate are conditioned by high oxide density. Thus for rise of 4 nm PbO – Sb₂O₅ – As₂O₅ particles from 0.5 m high copper melt two days are needed. Since stirring occurs in the process of oxidation, the rate of convection flows is on the level of 0.5 m/s, transition of oxide phases on the melt surface is practically impossible. Refining process intensification is possible by melt stirring and filtration as well as fusible slag forming.

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