Mechanistic study of the calcination process in magnesium production: Application of the Darcy-Clausius coupling model for improving environmental efficiency.

In the process of industrialization, it is found that the calcination process is an important factor affecting the reduction rate, which determines the energy consumption and carbon emission of the reaction process. In this study, the micro-nano physical model of the factors affecting the reduction rate of calcined precursors was constructed by coloring the SEM results of pellets before and after calcination with Gaussian height expression and combining Clausius and Gibbs equations. The influence of the formation degree of the internal pores of the pellets on the reduction rate was analyzed by controlling the calcination time of the precursor. It is concluded that when the calcination time of the precursor is 25min, the pore channel generated by carbonate decomposition has the highest flow rate of 6.338 × 10^-3 m/s, which is beneficial to the escape of magnesium vapor inside the pellet and improves the reduction rate (from 85 % to 92.34 %). The optimized process further reduces the energy consumption (0.22-0.25tce) and carbon emissions (0.8-0.95t) of the RVCMS process. The Darcy-Clausius coupling model is suitable for the calculation of the reduction rate of the pyrometallurgical process and the phase change diffusion reaction process, and predicts that the calcination conditions increase the thermal reduction rate. In addition, the increase of reduction rate will reduce the difficulty of secondary utilization of metallurgical slag, which is beneficial to the utilization and treatment of slag phase, and is of great significance to promote the field of green primary magnesium smelting.