Results of the study on effect of quartzite feed to the second stage of copper-nickel converter matte converting

Expected growth of cobalt consumption and increase of the metal price promotes a pressing need to consider possibility to enhance recovery of cobalt from copper-nickel feed containing high amount of this metal in pyrometallurgical process chain at the Nadezhda Metallurgical Plant named after B. I. Kolesnikov (NMP) of PJSC “MMC “Norilsk Nickel” Polar Branch. Pyrometallurgical processing of copper-nickel sulphide ores and concentrates at NMP comprises three stages: smelting of the incoming feed in flash smelting furnaces (FSF) to produce high-grade matte and slag, FSF slag and recycled slag treatment in slag cleaning electric furnaces (EF) to produce waste slag and low-grade matte, and converting high-grade FSF and low-grade EF mattes to produce converter matte and converter slag which is recycled to EF. Currently, total pyrometallurgical chain cobalt recovery does not exceed 55 % rel. of the incoming feed, i.e. 45 % rel. of cobalt are permanently lost with waste EF slag. At the same time, studies reveal that more than 30 % rel. of the total cobalt amount are circulated between EF and converter. Thus, decrease of cobalt concentration in the recycled materials will result in increase in cobalt recovery at NMP, and at Nornickel Polar Branch as a whole. This paper presents the results of laboratory tests and pilot studies on increasing cobalt recovery rates during converting using quartz flux (quartzite) at the final stage of converting and finishing ready-to-tap converter matte by removing iron oxides dissolved in sulfide phase. Treatment of almost ready-to-tap converter matte with quartz flux instead of using blast oxygen (for additional oxidation of iron) leads to preservation of cobalt in converter matte