Corrosion mechanism of magnesia-chrome and alumina-chrome refractories in E-scrap smelting

Pyrometallurgical processes have been widely recognised as the preferred technology for E-scrap recycling, and E-scrap smelting is usually accompanied by the formation of high-Al2O3-content slag. However, this slag can cause problems, such as refractory wear and even accelerated failure. Therefore, the corrosion mechanism of magnesia-chrome and alumina-chrome refractories in contact with FeOx-SiO2-CaO-Al2O3 smelting slag was experimentally studied in the range of 1300-1400 degrees C, in air (p(O2) = 0.21 atm) and at p(O2) = 10 atm. The results showed that refractory-component dissolution and new phases formation were the major causes of refractory degradation. The dissolution of the refractory components increased along with both increasing temperature and decreasing Al2O3 concentration in the initial slag. When decreasing the p(O2), the dissolution of MgO and Al2O3 into the slag slowed down. New phases such as forsterite, anorthite, and spinel were detected at the interface between the slag and the bulk refractory. The formation of forsterite accelerated the refractory wear, whereas the newly formed (MgO,FeO)center dot(Cr2O3,Fe2O3,Al2O3) spinel phase acted as a protective layer against further corrosion. A lower Al2O3 concentration in the slag and a higher smelting temperature both densified the formed spinel layer. Additionally, a high oxygen partial pressure was beneficial to the formation of spinel in the magnesiachrome refractory corrosion experiments. However, a low oxygen partial pressure was favourable for the formation of spinel on the surface of the alumina-chrome refractory materials. This study provides useful information for designing refractory materials and optimizing the processing parameters of E-scrap smelting.

Automated summary

This study investigated the corrosion mechanism of magnesia-chrome and alumina-chrome refractories in contact with smelting slag, and found that refractory-component dissolution and new phases formation were major causes of refractory degradation. Lower Al2O3 concentration and higher smelting temperature led to denser spinel layer formation, while high oxygen partial pressure favored spinel formation in magnesia-chrome refractories. In contrast, low oxygen partial pressure promoted spinel formation in alumina-chrome refractories.