Examining new parting compounds to improve copper anode quality

Abstract

At the final stage of the anode copper production process adopted by the Copper Plant of MMC Norilsk Nickel’s Polar Division, anode copper is poured in the moulds, the melt and the moulds are cooled down by process water spraying, the anodes are pushed out of the moulds and moved into accumulator bathes for final cooling with running water. The same anode copper is used to make moulds by casting, which ensures a waste-free production circuit and saves the need to use moulds made of other materials in the Norilsk Industrial Area. Parting compounds are used to prevent penetration of anodes. They are refractory powders proportionally blended with process water or alcohol that are poured, sprayed or brushed over the working surface of the mould and let to dry. Two drawbacks can be pointed out with regard to the parting compounds that are used by the Copper Plant. These drawbacks were observed during the casting process. A thinner layer of anode copper is formed with each casting cycle leading to penetration, surface defects or surface warping. Such anodes are rejected. Besides, as a result of being constantly in contact with the melt, the mould surface start to crack as it wears out. During casting and cooling, particles separate from the parting compound and transfer to the surface of the copper anode. Cool anodes are moved to the Copper Electrowinning Section to be placed in the electrolysis bathes, where the parting compound particles, insoluble in sulphuric acid solutions, form an electrolytic slime. The insoluble particles contain oxides of silicon, aluminium, magnesium, calcium, etc. These impurities make slime harder to process in the Metallurgical Shop affecting the quality of the final product – i.e. platinum group metal concentrate. This research aims to identify possibilities to improve the surface quality of anodes and reduce penetration so that less components of the parting compound reached the Copper Electrowinning Section or the Metallurgical Shop. In the course of this research, the optimum size distribution of the parting compound was identified; the conditions are described in which the parting compound is used at the Copper Plant; laboratory and pilot tests were conducted with an experimental parting compound that is not normally used by the Copper Plant in the copper anode production circuit.