Magnesium Reduction from Thanhhoa Dolomite by Ferrosilicon and Ferro-Silicocalcium as Reducing Agent

In this paper, a new reducing agent known as ferro-silicocalcium is being studied for its application in magnesium production through the Pidgeon process. Ferro-silicocalcium with main phase components CaSi2 and Si can reduce Mg from dolomite at a lower temperature than a traditional reducing agent. It thus improves the efficiency of magnesium production and solves the large energy consumption problem of the Pidgeon process. This paper presents thermodynamics calculations and experimental study on reducing magnesium from Thanhhoa dolomite with the new reducing agents known as ferro-silicocalcium and ferrosilicon as traditional reducing agents. From the thermodynamics calculations, CaSi2 in the ferro-silicocalcium can eliminate magnesium oxide at temperatures 1000°C lower than FeSi2 in ferrosilicon. This leads to a substantial decrease in the recovery temperature. When CaSi2 is decomposed, it releases silicon to improve the reduction process at temperatures greater than 1100°C. Experiments are performed to confirm the calculation results. The reduction process of dolomite by ferro-silicocalcium and ferrosilicon was analyzed by phases analysis of reduction slag through X-ray diffraction. The experimental results show that when using ferro-silicocalcium as a reducing agent, the recovering magnesium oxide efficiency reaches 91.3% over three hours with a recovering temperature of 1200°C. The efficiency is 7% higher than the traditional method using ferrosilicon under the same conditions. This proves that using ferro-silicocalcium as a reducing agent reduces the operating temperature of the reducing system and saves energy for the whole process. Therefore, ferro-silicocalium promises to be an effective alternative reducing agent in magnesium production.