| Converter slag is a byproduct in steelmaking process,and its resource utilization has been paid much attention.As the content of TFe in converter slag is nearly 30%,the recovery of iron is beneficial to the utilization of the secondary resources with high additional value,energy-saving,and emission-reduction.Based on the principle of bath smelting reduction,aluminum ash can be used as reducing agent,which not only can deeply reuse the converter steel slag,but also can automatically adjust the melting temperature and viscosity of the slag.With the addition of aluminum ash,the kinetics condition of reduction can be improved,and the polymerization and the separation of slag and gold also can be promoted.In the process of reducing converter slag by aluminum ash,the viscosity characteristics of the CaO-SiO2-Al2O3-MgO-FeO slag system directly affect the kinetic conditions of the reduction process,and further affect the yield of iron.Therefore,the viscosity characteristic of the present slag system is an important index in regard to the effect of aluminum ash reduction converter slag.In the present study,the rule of viscosity evolution was explained by the microscopic structure.Meanwhile,a new viscosity model of the CaO-SiO2-Al2O3-MgO-FeO system and its subsystems were established by the activation energy of unit structure.Main conclusions were listed as follows.(1)FeO played a role of depolymerization in the melt as a network modifier.With the FeO content decreasing from 25%to 0%,Q2+Q3 increased and Q0+Q1 decreased in the silicate structure,and the polymerization degree of the silicate units steadily strengthened,which could increase viscosity of the present system slag.(2)Al2O3 served as a network former in the present slag.When the A/(A+F)ratio increased 0.17 to 0.5,the melt structure was based on the silicate structure and Al3+acted as a substitution for Si4+ to strengthen the silicate network structure.With the A/(A+F)ratio increasing to 1,the melt structure was converted from silicate structure to aluminate structure and the polymerization of aluminate units became increased.Meanwhile,the polymerization of silicate units also increased due to the decrease of the FeO content,which could significantly increase viscosity of the present slag.(3)When the temperature was 1873 K and the basicity and MgO content remained unchanged,the Al2O3 content was below 15%and the FeO content was reduced from 25%to 15%,the simple silicate structure in the system will gradually transform into a complex silicate structure,resulting in the viscosity rising from 0.065 Pa·s to 0.091 Pa·s.When Al2O3 content increased from 15%to 30%,FeO content was lower than 15%,the total volume of aluminate structure increased gradually,FeO content gradually decreased,and the polymerization degree of the system increased significantly,resulting in viscosity increasing from 0.114 Pa-sto 0.194 Pa-s.(4)A viscosity model of CaO-SiO2-Al2O3-MgO-FeO slag system containing silicate structure was established.The experimental values of the system were in good agreements with the predicted values,and the average prediction error was 9.49%.Compared with the Urbain model,the Riboud model and NPL model,prediction effect had been greatly improved.The model was applicable not only to the quinary slag system,but also to the prediction of other subsystems containing silicate.The average prediction error of CaO-SiO2-Al2O3-FeO and CaO-SiO2-Al2O3-MgO were 13.6%and 8.9%.The system of CaO-SiO2-Al2O3,CaO-SiO2,SiO2-Al2O3 and SiO2-MgO slag had obtained a good forecast effect.However,for the CaO-SiO2-Al2O3 and SiO2-Al2O3-MgO systems with Al2O3 content higher than 40%,the prediction effect was not satisfactory,and the average prediction error of the model was 19.4%which exceed the 15%prediction error line. |
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