Study On The Desulfurization Ability And A_（Al2O3） Of CaO-SiO₂-MgO-Al₂O₃ Quaternary Slag System

The use of high-aluminum iron ore causes the Al2O3 content in the blast furnace slag to be high,resulting in an increase in the viscosity of the slag,a decrease in fluidity,and a decrease in desulfurization ability.The activity of components involved in desulfurization reaction is an important factor affecting the desulfurization process,but there are relatively few studies on the activity of components of blast furnace slag.Therefore,the activity prediction model of CaOSiO2-MgO-Al2O3 quaternary slag system is established,and the effects of R,w(MgO)/w(Al2O3)and Al2O3 content on the activity of components are explored.It is of great significance to further study the desulfurization ability of CaO-SiO2-MgO-Al2O3 quaternary slag system.Relevant research and achievements are as follows.(1)According to the ion-molecule coexistence theory,combined with MgO-SiO2,CaOSiO2,CaO-Al2O3,MgO-Al2O3,CaO-MgO-SiO2,CaO-Al2O3-SiO2 phase diagrams and related thermodynamic data,Establishing a CaO-SiO2-MgO-Al2O3 quaternary slag activity prediction model,and the relationship between components is reduced to non-homogeneous linear equations set,then solved it by programming in MATLAB with the using of the fsolve function.(2)At 1873K,Al2O3-CaF2 was used as the reference slag,CO was used as the shielding gas,and Sn was used as the metal solvent.The equilibrium time was 24h,and the activity of Al2O3 in the quaternary slag CaO-SiO2-MgO-Al2O3 was measured.(3)Comparing the measured value of the experiment with the predicted value of the model,the predicted values are basically consistent with the measured values of the model,then the predicted value of the CaO-SiO2-MgO-Al2O3 quaternary slag system model is determined,and the results are analyzed.The results show that when w(Al2O3)=15%and w(MgO)/w(Al2O3)=0.355 as R increases,the activity of a in slag decreases accordingly.When R=1.05 and w(Al2O3)=15%,as w(MgO)/w(Al2O3)increases,the activity of a(Al2O3)in slag decreases accordingly.When R=1.2 and w(Al2O3)=15%,as w(MgO)/w(Al2O3)increases,the activity of a(Al2O3)in slag decreases accordingly,but it is smaller than it is in R=1.05 and w(Al2O3)=15%with the same w(MgO)/w(Al2O3).When R=1.05 and w(MgO)/w(Al2O3)=0.35,the activity of a(Al2O3)in slag increases with the increase of Al2O3 content.When R=1.2 and w(MgO)/w(Al2O3)=0.355 the activity of a(Al2O3)in slag increases with the increase of Al2O3 content,and it is less than it is in R=1.05,w(MgO)/w(Al2O3)=0.35.(4)The desulfurization experiment of CaO-SiO2-MgO-Al2O3 quaternary slag system shows that when w(Al2O3)=15%and w(MgO)/w(Al2O3)=0.45,with the increases of R,the activity of a(Al2O3)in slag decreases continupusly,Ls increases,CaO SiO2 activity decreases,2CaO·SiO2 activity increases,CaO·Al2O3 activity keeps unchanged,and desulfurization capacity of slag increases.When w(Al2O3)=15%and R=1.25,with the increase of w(MgO)/w(Al2O3),the activity of N’(Al2O3)decreases,Ls increases,the activity of CaSiO3 decreases,The activity of Ca2SiO4 remained basically unchanged.,the activity of MgO·Al2O3 and CaO·MgO·2SiO2 gradually increases and the desulfurization capacity of slag increases.When w(MgO)/w(Al2O3)=0.45 and R=1.15,the desulfurization capacity of slag decreases with the increase of the content of Al2O3 in slag,and the corresponding Ls of slag decreases slightly.The activity of CaSiO3 and Ca2SiO4 decreases and that of MgO·Al2O3 and CaO·Al2O3 increases continuously.While Calcium oxide and magnesium oxide are both basic oxides.The desulfurization contribution of calcium oxide is about 99%,and that of magnesium oxide is about 1%.Calcium oxide is the main desulfurizer.