转炉多元非均相炉渣中含磷固溶体稳定存在的控制机理研究

For improving the dephosphorization ability of converter slag, according to the 2CaO•SiO2 solid and liquid phase coexistence in slag, a new technology of heterogeneous slag dephosphorization which promoting the formation of 2CaO•SiO2-3CaO•P2O5 was developed by worldwide scholars. At present, related researches focus on the formation process of phosphorus-containing solid solution. However, the solid solution easily dissolved in slag after formation under complex smelting conditions. The condition of stable existence and correlation mechanism for phosphorus-containing solid solution are not clear, which hinders the development of the technology of heterogeneous slag dephosphorization. Therefore, the equilibrium phase relation of multi component slag under different conditions will be firstly studied by thermodynamic software and experiment in this proposal. The change regulation of 2CaO•SiO2-3CaO•P2O5 primary crystal zone will be revealed to provide thermodynamic basis for analyzing the mechanism of stable exiting for phosphorus-containing solid solution. Then, the kinetic equation of formation for phosphorus-containing solid solution under complex conditions will be established, and the hardening rule of formation process will be also determined. Moreover, the dissolution mechanism of the phosphorus-containing solid solution will be studied to investigate the inner relationship and mechanism of action between the factors and dissolution process. Finally, a method which inhibits the dissolution of the solid solution will be probed out. This project will not only enrich scientific theoretical foundation and practical value for the heterogeneous slag dephosphorization process, but also bring higher academic value and scientific significance to promote converter dephosphorization.

为了提高转炉渣的脱磷能力，近年来国内外学者提出了利用2CaO•SiO2固相与液相共存的特点，以促进2CaO•SiO2-3CaO•P2O5固溶体生成的非均相渣脱磷新技术。目前相关研究多集中在含磷固溶体的生成过程等方面，然而在复杂的冶炼条件下，该含磷固溶体在生成后易重新溶解于液相渣中，其稳定存在的条件和相关作用机制尚不明确，从而阻碍了非均相渣脱磷技术的发展。为此，本项目拟首先利用热力学软件及高温实验研究转炉多元渣系在不同条件下的相平衡关系，揭示2CaO•SiO2-3CaO•P2O5初晶区范围的变化规律，为分析含磷固溶体的稳定存在机制提供热力学依据；之后建立复杂条件下含磷固溶体稳定生成的动力学方程，明确过程的强化规律。最后研究含磷固溶体的溶解机理，查明各因素与其溶解过程的内在联系及作用机制，并探索出抑制其溶解的方法。项目的开展可丰富非均相炉渣脱磷的相关理论，具有较高的学术意义和实际应用价值。

针对目前转炉非均相渣脱磷技术中未考虑MgO及MnO对2CaO·SiO2-3CaO·P2O5固溶体生成的影响、含磷固溶体生成后稳定存在的控制机制尚不明确等问题，本项目首先利用热力学软件及高温相平衡实验研究了CaO-SiO2-FeO-P2O5-MgO(MnO)多元渣系的相平衡关系，明确了相图中含磷固溶体区域的变化规律；之后又建立了多元渣系中含磷固溶体稳定生成的动力学方程，掌握了各动力学参数的影响机制；最后研究了各因素对含磷固溶体溶解行为的影响规律，并建立了其溶解速率的动力学方程。项目顺利完成了拟定的研究计划，并取得以下研究结果：. (1) 在CaO-SiO2-FeO-P2O5-MgO体系中，当提高MgO含量时，液相区在高FeO方向有扩大的趋势，含a-Ca2SiO4-Ca3(PO4)2的析晶区则向低FeO和高CaO方向收缩； 在CaO-SiO2-FeO-P2O5-MnO体系中，MnO含量的提高对液相区的影响不明显，但L+Slag+a-Ca2SiO4-Ca3(PO4)2和L+Slag+a-Ca2SiO4-Ca3(PO4)2+a-Ca2SiO4的析晶区逐渐缩小。. (2) 磷在渣中的传质和在2CaO·SiO2-3CaO·P2O5固溶体层中的扩散是CaO-SiO2-FeO-P2O5-MgO(MnO)渣系中2CaO·SiO2-3CaO·P2O5固溶体生成过程的限制性环节。1400℃下，磷在CaO-SiO2-FeO-P2O5-MgO(4mass%)渣中传质系数为3.88×10-6m/s，在固溶体中的扩散系数为2.04×10-11m/s2；磷在CaO-SiO2-FeO-P2O5-MnO(4mass%)渣中传质系数为4.48×10-6m/s，在固溶体中的扩散系数为1.51×10-11m/s2。. (3) 随着反应时间的延长，2CaO·SiO2-3CaO·P2O5固溶体的直径逐渐较小；降低温度、提高碱度及MgO含量均可抑制2CaO·SiO2-3CaO·P2O5固溶体的溶解；而在熔渣中添加MnO则对2CaO·SiO2-3CaO·P2O5固溶体溶解的影响不明显。含磷固溶体的溶解反应及在渣中的扩散均为2CaO·SiO2-3CaO·P2O5溶解过程的限制性环节，并建立了其溶解速率的动力学方程。