Study On Metallurgical Properties Of The B.F.slag Containing Alkali Metals

In order to reduce harmful effect of alkali metals on blast furnace and ensure direct motion of blast furnace smelting, according to the practiced component of the BF slag of Guang Steel, chemistry reagent is used to configure the slag. Potassium and sodium capacity, sulphide capacity and viscosity and melting temperature of slag containing alkali metals were studied by numbers.The potassium capacity of the BF slag was studied at 1450℃using gas-slag equilibrium techniques; the slag was equilibrated with a mixture gas of K-CO-CO2 -Ar to provide the partial pressure of oxygen and potassium. Under condition of experiment, it is shown that at fixed MgO and Al2O3 contents, increasing (%CaO)/(%SiO2) ratio from 0.76 to 1.26 decreases the potassium capacity; At a constant (%CaO)/(%SiO2) ratio and constant Al2O3 content, increasing MgO content from 6% to 16% of the slag results in an increase of the potassium capacity; The rising Al2O3 content from 9% to 17% of the slag at fixed (%CaO)/(%SiO2) ratio and MgO content, significantly increases the potassium capacity; At a constant [(%CaO)+(%MgO)]/(%SiO2) ratio and Al2O3 content, increasing MgO content and decreasing CaO content can increase the potassium capacity apparently . The sulphide capacity of the BF slag containing alkali metals was studied at 1500℃using gas-slag equilibrium techniques; the slag was equilibrated with a mixture gas of SO2-CO-CO2-N2 to provide the partial pressure of oxygen and sulphur. Under condition of experiment, study results reveal: at fixed MgO, Al2O3 and (K2O+Na2O) contents, the sulphide capacity increases with increasing (%CaO)/(%SiO2) ratio from 0.86 to 1.26; At a constant (%CaO)/(%SiO2) ratio and constant Al2O3, (K2O+Na2O) contents, the sulphide capacity increases first and decreases afterwards with increasing MgO content from 5% to 18% of the slag; The rising Al2O3 content from 12% to 18% at fixed (%CaO)/(%SiO2) ratio and MgO, (K2O+Na2O) contents, the sulphide capacity increases first and decreases then, the sulphide capacity is the max when Al2O3 content is about 13%; At constant Al2O3 and MgO contents, when (%CaO)/(%SiO2) ratio is 0.86,0.96,1.06 and 1.16, the sulphide capacity increases with increasing (K2O+Na2O) content.The viscosity and melting temperature of slag containing alkali metals were studied using RTW experimental equipment. The study results reveal: at a constant (%CaO)/(%SiO₂) ratio and constant Al₂O₃, (K₂O+Na₂O) contents,ηand T_s of slag containing alkali metals are lower than common slag's, the effect of MgO content onηand T_s of slag containing alkali metals is the same to common slag.ηdecreases and T_s increases first and decreases then with rising MgO content from 8% to 18%, T_s is the least when MgO content is about 12%; At a constant (%CaO)/(%SiO₂) ratio and constant MgO, (K2O+Na₂O) contents,ηand T_s of the slag increases with the rising Al₂O₃ content from 12% to 18%, the flowing property gets worse; At constant MgO, Al₂O₃ and (K2O+Na₂O) contents,ηand T_s of slag are affected greatly by variation of basicity,ηand T_s decreases first and increase then with rising (%CaO)/(%SiO₂), T_s is the least when (%CaO)/(%SiO₂) is about 0.96,ηis the least when (%CaO)/(%SiO₂) is about 1.16; At constant Al₂O₃ and MgO contents, when (%CaO)/(%SiO₂) ratio is 0.96,1.06 and 1.16,ηand T_s of acidic slag are affected greatly by (K2O+Na₂O) content, the T_s of the slag decreases with increasing (K2O+Na₂O) content, the effect gets weaken when basicity increases, when (%CaO)/(%SiO₂)>1.06, the T_s of the slag increases with increasing (K2O+Na₂O) content,ηhas little variation. Therefore alkali metals oxide have different function mechanism on T_s in acidic and basic slag。Removing alkali metals capacity, desulfuration capacity and the flowing property of slag synthetically were thought over, the proper component of Guang Steel slag containing alkali metals should be: (%CaO)/(%SiO₂) ratio remains at 1.0, MgO content remains at 12%, Al₂O₃ content remains at 15%.