(Invited) Magnesium Production By MgO Reduction in Molten CaF2-MgF2 Salt with Reactive Liquid Metal Cathode and Consumable Carbon Anode or Nonconsumable Zirconia Solid Oxide Membrane

Abstract

A process for magnesium production is proposed beginning with MgO electrolysis in molten MgF2-CaF2 salt with a reactive liquid metal cathode, followed by efficient multiple effect distillation to separate the magnesium from the cathode. Experiments with a liquid tin cathode and carbon anode show over 90% current efficiency; with a yttria-stabilized zirconia (YSZ) solid oxide membrane (SOM) between the bath and anode, current efficiency is above 80%. A detailed mass balance estimates the amount of MgF2 and tin required to maintain steady bath and cathode chemistry with CaO and other impurities in the MgO feedstock. A detailed energy balance describes the relationship between applied potential and cell thermal balance over a range of process temperatures, including minimum energy losses through cell leads. Emissions analysis shows a range of greenhouse emissions depending on the raw material type, MgO separation and calcination method, anode type (carbon or YSZ SOM), and electrical energy source.