Thermodynamic calculation and analysis results show that in ordinary- pressure the reaction temperature (T) of carbon-thermal reduction for MgO is 1 854 °C

it is difficult under hot metal pre-treatment condition to realize situ desulfurization by generating magnesium from magnesite-based desulfurizer. As carbon-thermal reduction occurs at 1 250 ~ 1 300 ℃， the vapour pressure of magnesium must be less than 0. 994 kPa

moreover at 1 350 〜1 400℃

the vapour pressure of magnesium should be less than 1. 004 kPa. In thermodynamics adding aluminum powder and Fe2O3 as thermite is available to carry out the carbon-thermal reduction and accelerate the magnesium vapor generation.