MMC Norilsk Nickel’s Polar Division, Norilsk, Russia:

L. V. Krupnov, Deputy Head of the Science and Technology Directorate – Chief Metallurgist, Candidate of Technical Sciences, e-mail: krupnovlv@nornik.ru
P. V. Malakhov, Principal Specialist in Pyrometallurgical Technology, e-mail: MalakhovPV@nornik.ru

Gipronikel Institute LLC, Saint Petersburg, Russia:
S. S. Ozerov, Lead Researcher at the Pyrometallurgy Laboratory, e-mail: OzerovSS@nornik.ru
R. A. Pakhomov, Senior Researcher at the Pyrometallurgy Laboratory, Candidate of Technical Sciences, e-mail: PakhomovRA@nornik.ru

Present in copper-nickel sulphide ores together with copper and nickel, cobalt is one of the key heavy non-ferrous metals dealt with by Nornickel. Cobalt is contained in iron and nickel minerals, such as pentlandite, pyrrhotite and pyrite. Certain samples may contain up to 2.5 wt. % of cobalt, with the average concentrations being 0.2 to 1.2 wt. %. This paper examines pyrometallurgical processing of sulphide ores that contain cobalt. Pyrometallurgical processes are preceded with flotation processes, when about 14% of the entire recovered amount of cobalt is wasted with tailings (process losses). The method of flotation is used for ore processing and for separating the product into copper and copper-nickel concentrates. Most of cobalt (77%) is supplied to Nadezhda Metallurgical Plant, where copper-nickel concentrates and other nickel-containing products are processed into converter matte. About 9% of all cobalt recovered from the ores goes to the Copper Smelter, where some of the metal ends up in dump slags after the pyrometallurgical process. About 40% of cobalt is removed from the copper production circuit and is supplied to Nadezhda Metallurgical Plant. The current recovery of cobalt in the pyrometallurgical circuit of Nadezhda Metallurgical Plant does not exceed 55% of the incoming material. This paper gives an overview of approaches and methods that could be useful for slag depletion or for minimizing the share of cobalt that goes into dump slags. This would help raise the end-to-end recovery of cobalt in the pyrometallurgical circuit. Having analyzed the relevant world literature, the authors were able to identify the most innovative ways to increase the cobalt depletion performance, which include processing of converter slags in a separate pyrometallurgical unit; use of innovative depletion agents made with sulphides, carbon-containing reductants or ferroalloys; substituting the slag-forming agents used in the converter process in order to minimize the amount of cobalt that goes into converter slags and eventually into dump slags.

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