(278d) A Novel Process for Continuous Magnesium Metal Production By Carbothermal Reduction of Magnesium Oxide

A novel process for continuous magnesium metal production by carbothermal reduction was designed and fabricated for testing as an efficient alternative to current silicothermic reduction methods. A complete ore-to-ingot process was demonstrated on a small pilot scale (up to 150 g/hr). Magnesium vapor was continuous generated using a fix bed gasification process at 1550°C and 1 – 10 kPa in which precursor carbon and magnesia pellets were nearly completely gasified (95 wt%). The rate of magnesium production was inferred from the axial velocity of the bed and the concentration of by-product carbon monoxide in the effluent. Continuous condensation of magnesium vapor was achieved by passing product gases over a moving bed of stainless steel particles (3mm) which absorbed the latent heat of magnesium condensation and the sensible heat of the gas stream. Condensed magnesium and stainless steel particles were removed by gravity and carbon monoxide was removed by pumping. To separate magnesium and steel a vacuum distillation was performed after which product magnesium was collected, melted, and cast into an ingot. Reactor yield based on the product carbon monoxide signal was 70-80% while total ore-to-ingot yield was only 29%. Magnesium oxidation in air prior to vacuum distillation was the likely cause of the discrepancy.