Using Magnesium Chloride to Volatilize Impurity Metals from Waste Magnesia–Chromium Refractories

Waste magnesia–chromium refractories from nonferrous smelting contain many valuable metals. High-grade metal concentrates can be obtained through gravity-flotation separation, but the tailings still contain a small amount of nonferrous metal, which prevents their direct regeneration. Thermodynamic analysis shows that magnesium chloride can be used as a chlorinating agent to volatilize the metal oxides. Under optimal processing conditions of nitrogen atmosphere, roasting temperature of 1100°C, magnesium chloride dosage of 9% and roasting time of 40 min, the contents of lead, bismuth, antimony and copper in roasting slag are 0.03%, 0.05%, 0.51% and 0.12%, respectively, and their volatilization rates are 99.22%, 97.60%, 80.73% and 88.51%. Comparing the microstructure of the roasting slag and the original refractory material, their chemical composition and crystal structure are basically the same. Therefore, volatile slag can be added as powder in the subsequent refractory regeneration.