Thermodynamic analysis and performance optimization of refining slag containing lanthanum oxide
ZHAO Bo1, WU Wei1, YANG Feng2, ZENG Jiaqing1, HE Jianzhong2, LIANG Zhigang2
1. Metallurgical Technology Institute, Central Iron and Steel Research Institute Co., Ltd., Beijing 100081, China; 2. Bayan Obo National Key Laboratory of Rare Earth Resources Research and Comprehensive Utilization, Inner Mongolia Baotou Steel Union Co., Ltd., Baotou 014010, Nei Mongol, China
Abstract：Aiming at optimization for refining slag of rare earth steel containing La, effects of basicity, C/A ratio, MgO content, MnO content, FeO content and La2O3 content on La2O3 activity, oxygen transfer capacity and sulfur capacity were calculated by molecular-ion coexistence theory. The most suitable refining slag ratio was determined by orthogonal experiment method, and the performance of optimized refining slag was analyzed from the aspects of mineral phase structure and melting point. The results show that the activity of La2O3 increases with the increase of basicity, C/A, MnO content and La2O3 content. With the increase of FeO content, the activity of La2O3 decreases, while MgO content has little effect on the activity of La2O3. The content of FeO and MgO has a great influence on the oxygen transfer capacity, which will significantly increase the oxygen transfer capacity, while the increase of basicity, C/A and La2O3 content will reduce the oxygen transfer capacity. The increase of basicity and C/A will increase the sulfur capacity of slag, while the increase of MnO, MgO and FeO will reduce the sulfur capacity. When the slag basicity is 8, C/A = 1.8, w(FeO)=0.4%, w(La2O3)=12%, w(MgO)=3%, w(MnO)=0.6%, the activity of La2O3 is 0.003 1, the oxygen transfer capacity is 2.83×10-6, and the sulfur capacity is 0.635 4. The activity and sulfur capacity of La2O3 are relatively large, and the oxygen transfer capacity is relatively small, which is the optimal ratio of refining slag. The mineral phases of the optimized slag are mainly 3CaO·Al2O3, 2CaO·SiO2, MgO and La2O3, and the melting temperature is 1 338 ℃. Therefore, the slag can be well melted at the smelting temperature and meet the refining requirements, which provides the theoretical basis for rare earth steel smelting technology.
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2023, Vol. 33 
