Experimental study of magnesium extraction from calcium carbide precipitator dust by silicothermal method

Abstract

Calcium carbide precipitator dust is a kind of solid waste containing high calcium oxide and magnesium oxide produced in the process of calcium carbide production. The extraction of magnesium from dust by vacuum silicothermic reduction with ferrosilicon as a reducing agent was studied. The effects of heating temperature, holding time, addition of ferrosilicon and calcium-to-magnesium ratio on the volatilization rate of magnesium in dust were studied. The results indicate that when ferrosilicon is used at an Mg:Si molar ratio of 2:1.05, and calcium oxide to magnesium oxide in the dust at a CaO:MgO molar ratio of 1.2:1, heating the compressed mixture to 1300 °C for 3 h can achieve a magnesium volatilization rate of 91.65%. When the CaO/MgO ratio was less than 1, 2CaO · MgO · 2SiO2 and 3CaO · MgO · 2SiO2 containing MgO were formed, resulting in a decrease in the volatilization rate of MgO.