硅热法炼镁增产提质的原理探索与应用

In the process of primary magnesium production by silicothermic reduction, a cooling zone with large gradient always exists near the retort outlet due to the setup of a necessary cooling system between the retort and crystallizer. However, few studies pay attention to influences of the temperature field near the retort outlet on the reaction rate, which can be reflected by the mass ratio of pellet and magnesium, a key parameter concerned by the primary magnesium industry. Here, by designing and building up an experimental retort that can mimic the actual production conditions and allows accurate temperature measurement at specific positions, we found that, the temperature near the retort outlet is low enough to lead to a significant reduction of reaction rate thus a higher mass ratio of pellet and magnesium. In order to suppress such a large temperature drop and raise the temperature, we designed a device to prevent heat loss near the retort outlet. With the usage of such device, the temperature near the retort outlet significantly increases compared to the control groups. As a result, the mass ratio of pellet and magnesium decreases from 6.3 to 5.95. Moreover, the purity level of the produced crude magnesium improves from less than Mg9980 (GB/T 3499—2011) to Mg9995A, which is attributed to the gradient condensation of impurities on this device. The industrial application of our design and its principle are expected to simultaneously improve the production and quality of primary magnesium made by silicothermic reduction, which can further benefit the entire magnesium industry.