Properties evaluation of DRI smelting slag for molten iron production: viscosity and sulfide capacity dependence on binary basicity
摘要
The properties of direct reduced iron (DRI) smelting slag are important in the DRI melting process for molten iron production to ensure the slag–iron separation and quality of molten iron. The influence of binary basicity on the viscosity and sulfide capacity of CaO–SiO2–MgO–Al2O3–FeO slag was investigated by the high-temperature experiments, structural analysis and thermodynamic calculation. The viscosity of the slag decreased rapidly with an increase in basicity from 0.4 to 0.8, and this trend became slow as the basicity further increased to 1.2. For the acidic slag with basicity of 0.4 and 0.6, the viscosity at 1500 °C was higher than 0.6 Pa s, which was harmful for the fluidity of slag melt. The slags with basicity of 0.8, 1.0 and 1.2 at 1500 °C showed the low viscosity of less than 0.6 Pa s. For the basic slag with basicity of 1.0 and 1.2, the rapid precipitation of melilite led to the abrupt increase behavior of the viscosity, and the acidic slag showed the gentle temperature–viscosity curves. The Raman analysis revealed that the conversion from Q3 to Q2, Q1 and Q0 mainly occurred with the basicity increasing from 0.4 to 0.8, and the conversion from Q2 to Q1 and Q0 was dominant with further increase in basicity to 1.2, decreasing the degree of polymerization. The sulfide capacity was improved with the increasing basicity due to the increase in O2– ions, and CaS could be formed dominantly for S2– stabilization in present slag. The sulfur partition ratio was derived from sulfide capacity, and the values of sulfur partition ratio at basicity of 0.4 and 0.6 were much smaller than those at basicity of 0.8, 1.0 and 1.2, indicating a weak desulfurization ability of the slag with a low basicity.