Abstract: Currently, research on hydrogen-based shaft furnaces mainly focuses on the reduction thermodynamics and kinetic processes and furnace structure design, while research on refractories is rare. Based on the strong reducing environment of H₂/CO mixed gas, this study simulated the service conditions of atmospheric pressure hydrogen-based shaft furnaces, and researched the performance changes and instability mechanisms of typical Al₂O₃-SiO₂ refractories after reduction treatment. The results show that under the condition of V(H₂) ∶V(CO)=5 ∶2, the heat treatment temperature rises from 450 ℃ to 950 ℃, and the reduction ability of mixed gas to Al₂O₃-SiO₂ refractories is gradually enhanced. Under current conditions, the two key factors leading to the instability of Al₂O₃-SiO₂ refractories are the Fe₂O₃ content and the phosphate binder. 1) When the Fe₂O₃ content in Al₂O₃-SiO₂ refractories is high, it is easily reduced to elemental iron in the H₂/CO atmosphere. At the same time, this situation will lead to a certain degree of volume change and significant decrease in mechanical properties of Al₂O₃-SiO₂ refractories. 2) Phosphate-bonded Al₂O₃-SiO₂ refractories materials also face phosphate volatilization, leading to an increase of apparent porosity and a decrease in structural stability. However, it is found that when the Fe₂O₃ content in the phosphate-bonded alumina-mullite brick is lower and accompanied by a certain amount of TiO₂, the refractories exhibits good resistance to H₂/CO gas reduction. By comparing the mechanical properties of Al₂O₃-SiO₂ refractories in CO atmosphere and H₂/CO atmosphere, it is found that the heat treatment condition which holding 3 h at 850 ℃ in the atmosphere of V(H₂) ∶V(CO)=5 ∶2 has a stronger reducing ability than the heat treatment condition which holding 100 h at 500 ℃ in CO atmosphere.

Key words: hydrogen-based shaft furnace, H₂/CO atmosphere, Al₂O₃-SiO₂ refractory, Fe₂O₃, phosphate, CO atmosphere