The Electrolytic Production of Magnesium from MgO

Abstract

There is only one primary producer of magnesium (Mg) metal in the U.S. utilizing an electrolytic process with feed from the Great Salt Lake. While electrolytic extraction of Mg from anhydrous MgCl₂ is 1.3× more energy efficient than the ferrosilicon reduction of dolomite, this Pidgeon process consumes over 2.3× the energy and produces 5× the CO₂ of the electrolytic MgCl₂ process. However, direct electrolytic reduction of MgO provides an opportunity to produce Mg at 20% less cost than the Pigeon process, conserve energy, and reduce CO₂ emissions. It has been demonstrated Mg can be electrolytically produced just above its melting point utilizing a composite anode of MgO+C as well as in a vapor state at approximately 1200 °C when MgO is dissolved in a select all fluoride fused salt. The high temperature processing is being bench pilot scale demonstrated to confirm the lower energy requirement and cost savings for full commercial scale demonstration.