Structural and properties Evolution of Al2O3-SiO2 Refractories under Simulated Hydrogen-Based Shaft Furnace Condition
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.
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