LLC Giproniсkel Institute (Saint Petersburg, Russia)
U. V. Abramova, Senior Researcher of the Refining Technology Sector of Finished Products Laboratory, abramovauv@nornik.ru
V. А. Grigorieva, Senior Researcher of the Refining Technology Sector of Finished Products Laboratory
М. B. Greiver, Head of the Refining Technology Sector of Finished Products Laboratory
I. V. Klimenko, Senior Researcher of the Refining Technology Sector of Finished Products Laboratory
О. S. Danilova, Researcher of the Laboratory of Pyrometallurgy
JSC Kola MMC (Monchegorsk, Russia)
I. S. Platonov, Head of the Hydrometallurgical Division of the Nickel Electrolysis Shop No. 2
The transition of Nickel Electrolysis Shop No. 2 at JSC Kola MMC to a process based on chloride leaching of nickel powder followed by nickel electro winning required optimization of several process stages, including the cementation purification of nickel solutions from copper. One of the major operational challenges of the copper cementation stage is the periodic deterioration of pulp filtration following the separation of cement copper. Analysis of precipitate accumulated on filter elements revealed a high content of silicon and aluminum containing compounds, suggesting their influence on filtration performance. This study investigates the behavior of silicon and aluminum compounds in concentrated chloride-sulfate nickel solutions over a wide acidity range. Experiments with model solutions demonstrated that increasing pH from 0 to 2.5 promotes the precipitation of SiO2 and Al2O3 into the solid phase, resulting in reduced filtration rates. Investigations using industrial copper cementation solutions showed that maintaining elevated acidity during the cementation process is impractical, as it decreases the degree of copper removal, increases the risk of hydrogen evolution, and adversely affects pulp filtration. It was established that filtration performance can be significantly improved by acidifying the suspended pulp only after completion of cementation and immediately before filtration. Based on the obtained results, acidification of the pulp with sulfuric acid in holding tanks prior to filtration to a free acid concentration of 4–10 g/dm3 (corresponding to a pH range of –0.1 to 0.1) is recommended. This approach enhances filtration rates without compromising copper cementation efficiency.
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