The effect of ternary basicity (CaO/(Al₂O₃+SiO₂)) on selective reduction of limonitic nickel ore

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ABSTRACT

Basicity is an essential parameter in the pyrometallurgy of nickel laterite processing to determine the low melting point temperatures of phases. However, its effect on selective reduction of nickel laterite is less studied. In this study, we investigated the effect of ternary basicity (CaO/(Al₂O₃+ SiO₂)) in selective reduction process. Nickel laterite, sodium sulphate, and bituminous coal were mixed and pelletised into 10–15 mm diameter. The reduction process is carried out at a temperature of 1150°C for 60 minutes in a muffle furnace continued with the magnetic separation process. The ternary basicity values were modified with CaO addition varied from 0.1 to 1.0. Modifying basicity with CaO addition could destroy the silicate and magnesium oxide complex structure, thus releasing iron and nickel to form the metallic phase of ferronickel, which could increase the nickel grade in ferronickel. Nevertheless, excessive addition of CaO resulted in the formation of calcium silicate structures with high melting point temperatures, such as akermanite and merwinite, which could suppress the troilite and inhibit the agglomeration of ferronickel particles. The optimal ternary basicity is 0.1 (which was modified by CaO addition). It resulted in 6.08% and 88.83% of nickel grade and recovery, respectively.

KEYWORDS:

• Limonitic nickel ore
• selective reduction
• ternary basicity
• ferronickel

Acknowledgments

The authors would like to thank the Universitas Indonesia for the PUTI 2020 grant with Contract No. NKB-648/UN2.RST/HKP.05.00/2020 for funding this research and LIPI’s science services for research laboratories.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the Universitas Indonesia.