JSC “Kola Mining and Metallurgical Company”, Monchegorsk, Russia:

P. V. Smirnov, Chief Specialist of Hydrometallurgical Department of Scientific-Research Part of Control and Analytic Center, e-mail: SmirnovPV@kolagmk.ru
N. V. Titov, Head of Hydrometallurgical Department of Nickel Electrolysis Shop

For the first time, the project of nickel electrolysis shop of “Severonickel” Combine foresaw the realization of one-stage purification of basic electrolyte from cobalt. Results of researches and testings have shown rather high efficiency of organization of cobalt purification process in two stages. The first stage supposed to carry out the cobalt sedimentation to concentration of 40–60 mg/dm³. Herewith, practically total amount of chlorine is spent on cobalt oxidizing, and obtained sediment is easily processed on concentrate process stage with minimal costs of sulphuric acid. The second stage supposed to carry out the deep sedimentation of cobalt with not more than 15 mg/dm³ of residue concentration in solution. The unloading pulp of candle filters was supposed to be directed in the head of the process. Together with the decreasing of sediment residue, the content of Ni³⁺ in this residue decreases. Residue does not make any influence on the content of obtained primary cobalt cake. The scheme was realized and has been operated in nickel electrolysis shop-1 for more than a year. Nowadays, this technology is realized in united nickel electrolysis shop. Operating scheme of cobalt purification is completed by two pachucas and candle filters’ unloading pulp tank of the second stage of purification of electrolyte from cobalt. There is organized the delivery of chlorine and carbonate to the second stage. The dosed pulp is delivered from unloading tank to collector of copper-purification filtrate. There is expected that decreasing of consumptions of chlorine, calcined soda and sulphuric acid are going to be 3.4, 7.9 and 5.0 thousand tones, respectively. These consumptions should provide the decreasing of chloride, sodium and sulphate content in waste waters of shop by 3.4, 3.4 and 4.9 thousand tones per year, respectively. In comparison with the functioning scheme, increased co-sedimentation of lead in cobalt cake is very important in the periods of operating of conversion with a number of series of electrolyte nickel of N-1u (Н-1у) grade (content of lead is not more than 0.0003%).