CO2 Free FeMn/Mn Production Through Molten Oxide Electrolysis

Abstract

Molten Oxide Electrolysis (MOE) is a new CO2-free technology that could alleviate the environmental impact of ferroalloy production. In this work the objectives were to perform (i) experimental lab scale studies of MOE for Mn from MnO using synthetic raw materials and a commercial Ni–Cr–Fe alloy as oxygen-evolving anode, and (ii) theoretical mass and energy balances for different cases of Mn ore purification for a hypothetical industrial MOE FeMn process. Low carbon Mn metal was recovered at lab scale, and the feasibility of MOE manganese production proven. While the Ni–Fe–Cr anode performed satisfactory during the electrolysis, some dissolution of Ni, Fe and Cr was detected. Theoretical energy and mass balance calculations gave a total energy consumption of 6.5–7.6 MWh/tonne Mn depending on the purification scenario. The results showed that the purified ore greatly improves the process. Non-purified ore requires large amounts of flux and more hydrogen in the pre-reduction step, both aspects increasing the need for energy. Non-purified ore also generates large amounts of spent electrolyte. Despite the above, it is an open question whether the benefits of purifications would outweigh the costs.KeywordsManganeseMolten oxide electrolysis (MOE)Sustainability