Joule-heating vacuum carbothermal reduction process for efficient and cleaner production of magnesium

The vacuum carbothermal reduction (VCTR) method is emerging as a promising and profitable technology for the preparation of metal magnesium (Mg). However, the conventional VCTR method is energy-intensive and time-consuming due to the separation of the operating steps and sluggish reaction kinetics. Here, we developed a one-step Joule heating vacuum carbothermal reduction (OJHVCTR) method for the preparation of metal Mg directly from dolomite. The experimental parameters including vacuum conditions, C/MgO molar ratio, power density and reaction times are optimized. And a MgO reduction rate of 90.7 % can be achieved within 3.2 min at a C/MgO molar ratio of 3:1 and a power density of 0.46 W mm⁻³ in 10 Pa. Contrast experiment and molecular dynamics (MD) simulations demonstrate that the rapid reaction can be ascribed to the enhancement of C atoms diffusion due to the electric field in the OJHVCTR method. Importantly, life-cycle assessment proves that compared to the Pidgeon method and the conventional VCTR method, the novel method can reduce energy consumption by 58 % and 6 % as well as GHG emissions by 58 % and 77 %, respectively. These results suggest that the new method can provide an efficient and cleaner alternative for metal Mg production, which is of great significance for structuring a carbon-neutral society with a sustainable and environmentally friendly energy system.