| With the continuous improvement of the industrial level,people's requirements for the quality of steel are also increasing.How to produce ultra-pure steel in batch,stable,and high-efficiency becomes one of the major technical problems faced in current steel smelting processes.In order to meet the requirements of continuous casting on the purity of molten steel,the harmful elements in molten steel must be removed to the extent required by steel grades.The removal of phosphorus in steel has always been the focus of metallurgical research.Previous experiments have demonstrated that phosphorus is present as2CaO惹iO2-3CaO感2O5 solid solution in converter slag,and that phosphorus is stable in2CaO惹iO2-3CaO感2O5.In order to improve the enrichment of phosphorus in the solid solution by changing the components of slag,the first study focuses on the CaO-SiO2-FeO-MgO-MnO-P2O5 slags system which represents the major components ofdephosphorizationslaginBOF.Phosphorusdistributionbetween2CaO惹iO2-3CaO感2O5 Solid Solution and Liquid Slag were analyzed by FactSage.The activity of slag component is one of the main factors affecting the thermodynamic properties of slag.And secondly.The effects of slag content?basicity,FeO content,P2O5content?on the slag component activities and the phosphorus distribution between slag and liquid iron were studied based on ion and molecular coexisted theory.Based on the calculation results,the possibility of enrichment of phosphate solid solution and the degree of enrichment are defined and the influence of slag composition on it is analyzed.The phosphorus partition ratio?LP?between slag and metal is an important parameter to characterize the dephosphorization capacity of slag at present.The feasibility of calculating the phosphorus partition ratio between slag and gold by the theoretical model of ion molecular coexistence was verified and the variation trend of slag composition to phosphorus distribution ratio between slag and gold was calculated by model.This results can provide a thermodynamic theoretical basis for improving the converter slag system to improve the dephosphorization efficiency in BOF.In this thesis work and the resulting conclusions are as follows.The CaO-SiO2-FeO-MgO-MnO-P2O5 slags component were calculated by FactSage,and then discussed the effects of slag content on phosphorus distribution and activity coefficient between 2CaO惹iO2-3CaO感2O5 Solid Solution and Liquid Slag.The results show that,when the basicity increased from 1.3 to 1.9,When the FeO content is increased from 20%to 32%,the phosphorus partition ratio between solid solution phase and the liquid slag phase decreases from 9.07 to 2.86,The content of dicalcium silicate and tricalcium phosphate decreased with the increase of FeO content,and the content of dicalcium silicate decreased greatly.With the increase of FeO content,the activity coefficient of P2O5 in solid solution phase increased gradually.When the P2O5 content increased from 2%to 10%,the phosphorus partition ratio gradually decreased with LP?l-ss?;as the phosphorus content in the slag increased,the content of dicalcium silicate decreased gradually,and the content of tricalcium phosphate gradually increased,The activity coefficient of P2O5 in the solid solution phase increases with the increase of phosphorus content in the slag.The activity of the components of the dephosphorization slag system CaO-SiO2-FeO-P2O5-MnO-MgO is calculated by the ion and molecular coexisted theory and the regular iron solution model.The effects of slag content?basicity,FeO content,P2O5 content?on slag component activity was discussed.The calculated results show that the activity of FeO,SiO2 and P2O5 decreases gradually and the CaO activity increases with the increase of slag binary basicity.The activity of 2CaO惹iO2 and3CaO感2O5 in the complex component increased first and then decreased,and reached the maximum value when the basicity was about 1.9.NC2S-C3P first increases and then decreases.When the slag basicity is about 1.6,the maximum value is reached,while RC2S-C3P gradually increases,and reaches a maximum when the slag basicity is 2.2,and then remains basically unchanged.When the content of FeO was increased from20%to 32%,the activity of CaO and P2O5 decreased,and 2CaO惹iO2 and 3CaO感2O5decreased with the increase of FeO content.Both NC2S-C3P and RC2S-C3P decrease with increasing FeO content.As the content of P2O5 in the slag increases,the activity of FeO and P2O5 in the simple component increases gradually and the activity of CaO decreases.The activity of 2CaO惹iO2 in the complex component gradually decreases,and 3CaO感2O5 has the opposite effect with the activity of P2O5 increased gradually.The calculation results of the two kinds of models on the activity of simple components NC2S-C3P gradually increases with increasing P2O5 content and RC2S-C3P decreases gradually.The phosphorus distribution ratio between the CaO-SiO2-FeO-P2O5-MnO-MgO slag system and liquid iron was calculated by Healy model?Suito1 model?Suito2model?Suito3 model?Zhang model?the ion and molecular coexisted theory and the regular iron solution model.The calculation results are compared with the phosphorus distribution ratio between the slag and gold in the actual plant data.The effects of slag content?basicity,FeO content,P2O5 content?on phosphorus distribution ratio calculated by the ion and molecular coexisted theory was discussed.The calculation results show that the accuracy of phosphorus partition ratio between slag and metal calculated by coexistence model is higher than other models.The contribution of tricalcium phosphate to the phosphorus partition ratio of slag gold is much greater than the contribution of other phosphorus compounds to the phosphorus partition ratio.Under the calculation conditions of this paper,with the increase of basicity of slag,the phosphorus partition ratio between slag and metal increases gradually;With the increase of FeO content,the phosphorus partition ratio of slag gold increased first and then decreased.When the FeO content was about 38%,the maximum value was obtained.With the increase of P2O5content in slag,the phosphorus partition ratio decreased. |
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