Distribution of impurities in magnesium via silicothermic processes

The desire for light weight materials, particularly in the automotive field, is fuelling greater magnesium production. The Pidgeon Process is currently the most widely used process for the production of magnesium. This batch process involves reduction of dolomite by ferro-silicon, carried out at temperatures between 1100 to1200 degrees Celsius under vacuum in a retort, producing magnesium vapour which is then cooled and collected as a condensate. The Magnetherm process is also a vacuum batch process based on similar chemistry but operates at higher temperatures with magnesia dissolved in a slag. Various operational issues relating to the batch and vacuum nature of the process have limited its development. The development of magnesium production in atmospheric pressure is currently underway by Mintek. Higher temperatures will improve the kinetics of the silicothermic reduction and increase the productivity, but will also promote greater impurities into the vapour.