Production of raw copper through continuous converting of copper-nickel sulphide materials

Abstract

The conventional technology of converting copper mattes in horizontal converters has its drawbacks and fails to conform with the current environmental norms and regulations applicable to metallurgical processes. Therefore, it should be replaced with an environmentally sustainable technology. This paper considers the results of a lab and pilot scale study that looked at converting nickel-bearing copper material into raw copper and running nickelbearing slag. It is demonstrated that the continuous converting process can be stable in both three-layer mode (i. e. slag – white matte – copper) and two-layer mode (i. e. slag – copper). With the help of scanning electron microscopy and electron microprobe analysis, it was established that most of copper, nickel and cobalt get wasted in a soluble form. Choice of fluxes produces a significant effect of the process performance. Fluxes were added to maintain the total concentration of SiO2 and CaO in the slag at 32%. At the same time, varying SiO2/CaO ratios were used depending on the operating mode — from pure Fe – Si slag to pure Fe – Ca slag. It is noted that a rising SiO2/CaO ratio leads to a higher recovery of nickel into slag. A pure Fe – Si slag mode is associated with foaming. The results of the lab study were verified through test heats carried out in a pilot Vanyukov furnace. The obtained raw copper has the following composition, wt %: 3.6–4.2 Ni; 0.6–1.2 S; 0.006–0.06 Fe; and it needs to be final converted for better refining.