Activity coefficients of NiO and CoO in CaO-Al2O3-SiO2 slag and their application to the recycling of Ni-Co-Fe-based end-of-life superalloys via remelting

Xin Lu; Takahiro Miki; Tetsuya Nagasaka

doi:10.1007/s12613-017-1375-8

Volume 24 Issue 1

Jan. 2017

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Article Navigation > International Journal of Minerals, Metallurgy and Materials > 2017 > 24(1): 25-36

Xin Lu, Takahiro Miki, and Tetsuya Nagasaka, Activity coefficients of NiO and CoO in CaO-Al₂O₃-SiO₂ slag and their application to the recycling of Ni-Co-Fe-based end-of-life superalloys via remelting, Int. J. Miner. Metall. Mater., 24(2017), No. 1, pp. 25-36. https://doi.org/10.1007/s12613-017-1375-8

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Xin Lu, Takahiro Miki, and Tetsuya Nagasaka, Activity coefficients of NiO and CoO in CaO-Al2O3-SiO2 slag and their application to the recycling of Ni-Co-Fe-based end-of-life superalloys via remelting, Int. J. Miner. Metall. Mater., 24(2017), No. 1, pp. 25-36. https://doi.org/10.1007/s12613-017-1375-8

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Research Article

Activity coefficients of NiO and CoO in CaO-Al₂O₃-SiO₂ slag and their application to the recycling of Ni-Co-Fe-based end-of-life superalloys via remelting

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Corresponding author:
Xin Lu E-mail: xin.lu.a5@tohoku.ac.jp
Received: 8 June 2016; Revised: 28 September 2016; Accepted: 29 September 2016

Abstract

Abstract

To design optimal pyrometallurgical processes for nickel and cobalt recycling, and more particularly for the end-of-life process of Ni-Co-Fe-based end-of-life (EoL) superalloys, knowledge of their activity coefficients in slags is essential. In this study, the activity coefficients of NiO and CoO in CaO-Al₂O₃-SiO₂ slag, a candidate slag used for the EoL superalloy remelting process, were measured using gas/slag/metal equilibrium experiments. These activity coefficients were then used to consider the recycling efficiency of nickel and cobalt by remelting EoL superalloys using CaO-Al₂O₃-SiO₂ slag. The activity coefficients of NiO and CoO in CaO-Al₂O₃-SiO₂ slag both show a positive deviation from Raoult's law, with values that vary from 1 to 5 depending on the change in basicity. The activity coefficients of NiO and CoO peak in the slag with a composition near B=(%CaO)/(%SiO₂)=1, where B is the basicity. We observed that controlling the slag composition at approximately B=1 effectively reduces the cobalt and nickel oxidation losses and promotes the oxidation removal of iron during the remelting process of EoL superalloys.
- recycling;
- nickel;
- cobalt;
- end-of-life;
- superalloys;
- activity coefficients;
- remelting;
- slag

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