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HEAVY NON-FERROUS METALS
ArticleName Oxide inclusions in copper during its fire refining process
ArticleAuthor Selivanov E. N., Popov A. I., Selmenskikh N. I., Lebed A. B.
ArticleAuthorData

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

Abstract

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 CuхSeTeS 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.

keywords Blister copper, refining, oxidation, impurities, oxide inclusions, lead, antimony, arsenic, selenium, oxygen, nickel, sulfur
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