Magnesium production by a coupled electric and thermal field

Abstract

A novel method was used to prepare metallic magnesium through a coupled electro-thermal field at 10 Pa pressure by using calcined dolomite and ferrosilicon as raw materials. This approach effectively reduced the reaction device temperature typically needed to extract magnesium through conventional methods. Three independent variables, i.e., reaction time, direct current (DC) electric field intensity (correspond device temperature), and current density were investigated in terms of the extent of reduction (reduction ratio) of magnesium oxide (MgO). The results illustrate that the reduction ratio of MgO increased significantly by extending reaction time, reducing DC electric field intensity (correspond to increasing device temperature), and increasing current density. For decreasing the furnace device temperatures, higher intensities of DC electric fields were needed. When applying a DC electric field intensity of 950 V/cm, the reduction ratio of up to 88.35% was obtained under current density of 1.18 A/cm2 for 150 min at 700 °C of device temperature. The X-ray diffraction and electronic probe micro-analyzer analyses showed that the purity of metallic magnesium obtained through the proposed method was 98.54 wt%. It was found that the magnesium reduction mechanism of the coupled field method could be explained by the Joule heating effect.