普通含铬铁水脱磷用CaO-BaCO3-Fe2O3-Cr2O3基低氟或无氟渣系的熔体性质及氧化脱磷作用机理研究

The large scale use of low grade and inferior iron ore such as laterite nickel mine leads to the increase of chromium content in hot metal of blast furnace. It is difficult to dephosphorization of converter due to the increase of chromium content in hot metal of blast furnace. This project will carry out the research on the melt properties of CaO-BaCO3-Fe2O3-Cr2O3-based low fluorine or fluorine-free slag system and oxidation dephoshporization of common chromium containing hot metal by the above slag system which is formed by partly or completely replacing CaF2 with rare earth tailings. With the help of scanning electron microscope, Raman spectrograph, X-ray diffractometer, OPA-100 and other testing tools, melt characteristics, microstructure and crystallization behavior of low fluorine or fluorine-free slag system for dephosphorization of chromium containing hot metal will be studied, and the distribution behavior of phosphorus and chromium between low-fluorine or non-fluorine dephosphorization slag system and common chromium containing hot metal will also be studied. Dephosphorization behavior of CaO-BaCO3-Fe2O3-Cr2O3-based low fluorine or fluorine-free slag system will be studied. The relationship between composition, microstructure and melting properties of low fluorine or fluorine-free slag system for dephosphorization of common chromium containing hot metal will by analyzed. The existing form, phase composition and forming process of spinel in common chromium containing hot metal dephosphorization slag will be discussed. The migration behavior of chromium in common chromium containing hot metal between slag and melt will be dissected. The mechanism of dephosphorization of common chromium containing hot metal by CaO-based low fluorine or fluorine-free slag system and the effect of rare earth tailings on dephosphorization will be revealed.

基于红土镍矿等低品位劣质铁矿石大规模使用导致高炉铁水铬含量升高使转炉脱磷困难的问题，本项目拟开展稀土尾矿部分或全部替代CaF2形成的CaO-BaCO3-Fe2O3-Cr2O3基低氟或无氟渣系熔体性质及渣系用于普通含铬铁水氧化脱磷的研究，借助于扫描电子显微镜、拉曼光谱仪、X射线衍射仪、金属原位分析仪等检测工具，研究普通含铬铁水脱磷用低氟或无氟渣系的熔体特征、微观结构与析晶行为，磷和铬在低氟或无氟脱磷渣系与普通含铬铁水间的分配行为，CaO-BaCO3-Fe2O3-Cr2O3基低氟或无氟渣系脱磷行为，分析普通含铬铁水脱磷用低氟或无氟渣系组成、结构与熔化性质之间相互关系，探讨普通含铬铁水脱磷渣中尖晶石的存在形式、物相组成以及形成过程，剖析普通含铬铁水中的铬在渣-金间的迁移行为，揭示CaO-BaCO3-Fe2O3-Cr2O3基低氟或无氟渣系用于普通含铬铁水脱磷的作用机理及稀土尾矿在脱磷过程中的作用。

普通含铬铁水转炉吹炼过程脱磷相对困难。为了对转炉吹炼普通含铬铁水冶炼普通碳钢提供必需基础理论支持，本课题借鉴国内外研究成果，提出了以稀土尾矿部分或全部替代CaF2形成CaO-BaCO3-Fe2O3-Cr2O3基渣系脱磷的思路，系统研究了CaO-BaCO3-Fe2O3-Cr2O3基渣系组成对其熔点、粘度、渣中CaO和Fe2O3活度及渣系脱磷效果的影响，深入剖析了普通含铬铁水脱磷相对困难的影响因素，分析了稀土尾矿在普通含铬铁水氧化脱磷过程中的作用，为指导普通含铬铁水氧化脱磷提供了理论基础。研究结果表明：普通含铬铁水中铬的氧化产物使脱磷渣系熔点升高，粘度增大，导致渣系脱磷动力学条件变差，一定范围内控制CaO-BaCO3-Fe2O3-Cr2O3基渣系的w(CaO)/w(Fe2O3)、w(BaCO3)和w(稀土尾矿)可以使渣系熔点降低，流动性改善。Factsage热力学计算结果分析表明，稀土尾矿的添加可使CaO-BaCO3-Fe2O3-Cr2O3基渣系中组元CaO的活度降低，组元Fe2O3活度增大，使脱磷渣系的氧化能力增强；稀土尾矿中稀土氧化物及CaF2的带入，使CaO-BaCO3-Fe2O3-Cr2O3基渣系熔点和粘度在一定程度上可以控制在较低水平，以改善CaO-BaCO3-Fe2O3-Cr2O3基渣系脱磷动力学条件。热态实验显示，用CaO-Fe2O3-Cr2O3-稀土尾矿渣系对w[Cr]=0.25%左右的铁水脱磷，w(CaO)/w(Fe2O3)=1.0，w(Cr2O3)=3.3%，w(稀土尾矿)=15%时，渣系脱磷率较高；而w(CaO)/w(Fe2O3)=0.9，w(BaCO3)=13%，w(稀土尾矿)=13.5%，w(CaF2)=8%时，CaO-Fe2O3-BaCO3-CaF2-稀土尾矿渣系的脱磷效果较好。用CaO-Fe2O3-BaCO3-CaF2-Cr2O3-稀土尾矿渣系脱磷时，w(CaO)/w(Fe2O3)=1.0，w(BaCO3)=15%，w(CaF2)=8%，w(Cr2O3)=3%，w(稀土尾矿)=18%时，渣系的脱磷率较高；而w(CaO)/w(Fe2O3)=0.65，w(BaCO3)=20%，w(稀土尾矿)=20%，w(Cr2O3)=3.5%时，CaO-Fe2O3-BaCO3-4.5%CaF2-Cr2O3-5%MgO-稀土尾矿渣系的脱磷效果相对较好。