Experimental and Numerical Modeling Studies on Production of Mg by Vacuum Silicothermic Reduction of CaO•MgO

The silicothermic reduction to magnesium is now intensively used in industry. In this article, an experimental and numerical modeling study on the reduction process in the single briquette and in an industrial retort was carried out. The experimental study was first conducted, and the experimental results indicated that both the thickness (from 17 similar to 19 to 3 similar to 4 mm) and heating temperature (from 1323 K to 1473 K [1050 A degrees C to 1200 A degrees C]) play significant roles in the reduction process in the single briquette. A kinetics analysis on the experimental data under the conditions of 3 to 4 mm briquette and different heating temperature indicated that the magnesium reduction reaction is controlled by the phase interface model before an extent and is controlled by the diffusion model after that. Then, the numerical model was developed according to the experimental data and used to predict the magnesium reduction performances in retort. The model results were validated in good agreement with the industrial data. The model prediction indicated that the magnesium reducing promotes inside layer by layer, and the reducing in the retort concentrates in one or two layers. It is concluded that the reduction process in retort is controlled by the heat transfer and reaction itself, the reaction heat needed for briquette is large, and the heat transfer becomes the main limiting factor.