基于CaO-SiO2-Al2O3-FetO-MgO高铝无氟渣系的中高磷铁水转炉脱磷作用机理研究

In recent years, some evidence has suggested that the development and utilization of low grade complex iron ores represented by high phosphorus iron ores have attracted more and more attention of metallurgists. LD smelting technology is an effective way to utilize the high phosphorus iron ores in our country. This project takes the dephosphorization process of medium and high phosphorus hot metal as the research target, carries out the thermodynamic and dynamic research on dephosphorization of high-aluminum CaF2-free slag system. During the experiment period, we use the instrument and detection means of scanning electron microscope, electron probe micro-analyzer, XRD, original position analyzer for metal, thermogravimetry and differential thermal analysis and so on. Effects of slag system components on phosphorus distribution ratio, P2O5 activity coefficient, phosphate capacity, dephosphorization rate, and so on, are analyzed. We also analysis the formation process of phosphorus concentrating phase and effect of slag system components on the formation process of phosphorus-concentrating phase. Existing form of Al2O3 in the dephosphorization slag and effect of Al2O3 on the formation process of phosphorus concentrating phase are analyzed. On the basis, dephosphorization thermodynamics model and reaction kinetics model based on double-film theory are established. By means of the established model, we will analysis the restrictive step of dephosphorization, the optimum conditions of thermodynamics and dynamics about dephosphorization of high-aluminum CaF2-free slag system used by medium and high phosphorus hot metal. Research results will reveal the dephosphorization mechanism of high-aluminum CaF2-free slag system and effect mechanism of Al2O3 on slag system dephosphorization result. This will provide a series of theoretical datas for guiding the smelting of low phosphorus steel or ultra-low phosphorus steel used medium and high phosphorus hot metal in converter, increase the scale of high phosphorus iron ores used in our iron and steel enterprises.

以储量丰富的高磷铁矿为代表的低品位复杂铁矿资源的开发利用逐渐受到关注。转炉冶炼可能是解决高磷铁矿石资源利用的有效方法。申请书以中高磷铁水脱磷过程为对象，开展高铝无氟渣系脱磷的热力学和动力学研究，利用扫描电镜、电子探针、XRD、原位分析仪、热重差热分析仪等工具和手段，分析渣系各组分对磷在渣金间分配比、P2O5活度系数、磷容量、脱磷率等的影响，研究脱磷渣中含磷富集相的形成过程及渣系各组分对其生成的影响，确定Al2O3在脱磷渣中的存在形式及其对含磷富集相形成的影响。在此基础上，建立脱磷的热力学模型和基于双膜理论的反应动力学模型；借助建立的模型，分析脱磷的限制性环节，探讨中高磷铁水用高铝无氟渣系脱磷的最佳热力学动力学条件；揭示中高磷铁水用高铝无氟渣系脱磷的机理及Al2O3对渣系脱磷效果的影响机理，为转炉采用中高磷铁水冶炼低磷或超低磷钢积累一些列理论数据，努力提高高磷铁矿在我国钢铁企业中的使用规模。

CaO-SiO2-Al2O3-Fe2O3-(MgO)渣系熔点随其碱度增大而升高，随w(Al2O3)增大先降低后略有增大，随w(Fe2O3)增大而降低；渣系粘度随其碱度和w(Fe2O3)增大而降低，随w(Al2O3)增大而增大；CaO的活度随渣系碱度增大而增大，随w(Fe2O3)、w(Al2O3)增大而减小；Fe2O3的活度随渣系碱度增大而减小，随w(Fe2O3)、w(Al2O3)增大而增大。. 对中磷铁水脱磷，脱磷率随CaO-Fe2O3-Al2O3渣系中w(CaO)/w(Al2O3)增大先升高后略有降低，随w(CaO)/w(Fe2O3)增大而降低；CaO-SiO2-Fe2O3-Al2O3渣系脱磷，相对最优组成为38.11%CaO-10.89%SiO2-6%Al2O3-45%Fe2O3。对高磷铁水脱磷，w(CaO)/w(Fe2O3)=0.45、w(Al2O3)≤6%的CaO-Fe2O3-Al2O3渣系脱磷率大于90%；CaO-SiO2-Al2O3-Fe2O3渣系脱磷率随其碱度、w(Al2O3)的增大先升高后略有降低，随着w(Fe2O3)增大而升高；CaO-SiO2-Al2O3-Fe2O3-MgO渣系脱磷率随碱度、w(Fe2O3)的增大先升高后略有降低，随w(Al2O3)增大而降低，用Li2O、CeO2、La2O3、CaF2等量替代Al2O3时，Li2O的脱磷效果最好。. 石灰溶解速度随CaO-Al2O3-Fe2O3-SiO2-MgO-MnO-P2O5渣系碱度增大而降低，渣系中w(Fe2O3)增大可促进石灰溶解；渣中添加少量的Al2O3有助于石灰溶解，反之则会抑制石灰溶解。CaO-Al2O3-Fe2O3-SiO2-MgO渣系对镁碳砖侵蚀深度和侵蚀面积随其碱度、w(Fe2O3)增大而增大，随w(Al2O3)增大先增大后略有降低。. 磷在脱磷反应过程中会生成C3P，C3P以扩散和析出形式与熔渣中的2CaO•SiO2结合生成C2S-C3P固溶体，C2S-C3P固溶体相是磷在脱磷后熔渣中的主要富集相。随着脱磷渣中w(Al2O3)增多，脱磷后熔渣中先期析出的低磷nC2S-C3P固溶体与脱磷渣中的Al2O3不断反应生成高磷n′C2S-C3P固溶体(n′＜n)和铝酸钙，使得渣系脱磷能力提高，但过量使用Al2O3会降低渣系的脱磷能力。