Phosphate rocks mainly contain Ca₃(PO₄)₂, SiO_2, and MgO. The vacuum carbothermal reduction of Ca₃(PO₄)₂ with different MgO contents was investigated to determine the maximum volatilization rate of P₂ and the transformation of phases in a SiO₂–C–Ca₃(PO₄)₂–MgO-based system. The application of reduced slag in the dephosphorization of a converter was discussed. The carbon excess coefficient (CEC), reduction temperature, and equilibrium phase were calculated using FactSage 8.1. The quinoline phosphomolybdate weight method, scanning electron microscopy-energy dispersive X-ray spectroscopy, and X-ray diffraction were used to characterize the volatilization rate of P₂, phases, and micromorphology of the reduced slag. The volatilization rate of P₂ first increased and then decreased, with the highest volatilization rate of 93.77% obtained at n(MgO/CaO) = 0.50. The reduced slag phase changed from CaSiO₃ to 2CaO·SiO₂·MgO·SiO₂, CaO·SiO₂·MgO·SiO_2, and 3CaO·P₂O₅·2CaO·SiO₂ solid solutions with increasing MgO content. The diffusion of graphite was hindered by an excessive MgO solid phase when n(MgO/CaO) > 0.50, resulting in the reaction of unreacted Ca₃(PO₄)₂ with 2CaO·SiO₂·MgO·SiO₂ to form 2CaO·SiO₂·3CaO·P₂O₅ (C₂S–C₃P₂) during the holding process, thus reducing the reduction rate of Ca₃(PO₄)₂. Reduced slag with a small amount of phosphorus can be used in converter smelting to achieve low-temperature dephosphorization.

Graphical Abstract

中文翻译：

---

SiO2-C-Ca3(PO4)2-MgO基体系中MgO对Ca3(PO4)2真空碳热还原机理的影响

磷矿主要含有Ca ₃ (PO ₄ ) ₂、SiO ₂和MgO。_{研究了不同MgO含量的Ca 3} (PO ₄ ) ₂的真空碳热还原反应，以确定P ₂的最大挥发速率和SiO ₂ –C–Ca ₃ (PO ₄ ) ₂中的物相转变。–基于MgO的系统。讨论了还原渣在转炉脱磷中的应用。使用FactSage 8.1计算碳过剩系数(CEC)、还原温度和平衡相。采用磷钼酸喹啉重量法、扫描电镜-能谱仪和X射线衍射仪对还原渣中P ₂的挥发率、物相及微观形貌进行表征。_{P 2}的挥发率先上升后下降，n (MgO/CaO)=0.50时挥发率最高，达到93.77%。还原渣相由CaSiO ₃转变为2CaO·SiO ₂ ·MgO·SiO ₂、CaO·SiO_{随着MgO含量的增加，出现2} ·MgO·SiO ₂、3CaO·P ₂ O ₅ ·2CaO·SiO ₂固溶体。当n (MgO/CaO) > 0.50时，过量的MgO固相阻碍了石墨的扩散，导致未反应的Ca ₃ (PO ₄ ) ₂与2CaO·SiO ₂ ·MgO·SiO ₂反应生成2CaO·SiO ₂ ·3CaO·P ₂ O ₅ (C ₂ S–C ₃ P _{2 )在保温过程中，从而降低了Ca 3} (PO ₄ )的还原率₂ . 含少量磷的还原渣用于转炉冶炼可实现低温脱磷。

图形概要