Kola MMC, Monchegorsk, Russia:

V. V. Volkov, Superintendent of the Chemical and Metallurgical Shop, e-mail: VolkovVV@kolagmk.ru
S. V. Shcherbakov, Principal Metallurgist at the Engineering Office, e-mail: scherbakovsv@kolagmk.ru

Gipronikel Institute LLC, Saint Petersburg, Russia:
I. N. Khomyakova, Senior Researcher at the Hydrometallurgical Laboratory
V. E. Zhukova, Category II Engineer at the Hydrometallurgical Laboratory

An upgrade of the nickel refining circuit realized in 2019 by Kola MMC when the plant adopted an electrowinning process for extracting nickel from sulphate-chloride solutions resulting from chlorine dissolution of tube furnace nickel powder, led to a considerable decrease in the amount of nickel sludge generated. The latter is treated at the Chemical and Metallurgical Shop by liquid phase sulphation in the presence of sulphuric acid. Other materials containing precious metals are now used in the sulphation process. For example, the concentrate obtained as a result of flotation of the tube furnace nickel powder chlorine dissolution residue. The main purpose of sulphation is to obtain selective concentrates of platinum group metals. The products include platinum-palladium concentrate and a concentrate of concomitant metals that contains at least 20 % of rhodium. The qualitative and quantitative characteristics of the concentrates define the process to be applied, as well as the recovery of base metals during further refining. A change in the feedstock supplied to the Chemical and Metallurgical Shop affected the distribution of rhodium between the target concentrates leading to a greater loss of concomitant metals in the refining process. The high demand for platinum group metals at the global market, the drawbacks of the current process, as well as the new type of feedstock supplied created a need for the process parameters to be studied and adjusted. The paper examines the process flowsheet and looks at ways to raise the selectivity of the final products by means of liquid phase sulphation in the presence of sulphuric acid.
Contributors to this paper include M. A. Lastochkina, who oversees the precious metals section at the Hydrometallurgical Laboratory of Gipronikel Institute.

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