Original Article

Study on the recovery of phosphorus and iron from molten modified high-phosphorus industrial slag by carbothermal reduction

Metallurgical Technology Research Institute, Central Iron and Steel Research Institute, Beijing 100081, China

e-mail: ^* linlu_luke@sina.com

Received: 16 September 2022
Accepted: 23 March 2023

Abstract

To effectively recycle phosphorus and iron resources in high-phosphorus industrial slag during molten modification process, the thermodynamic conditions and influence laws of recovery of valuable elements from converter slag with different P₂O₅ content by carbothermal reduction after melting and modification are systematically analyzed. The results show that the reduction rates of P₂O₅ and FeO decrease with the increase of P₂O₅ content at 1450 °C and the basicity of 1.0. Meanwhile, the experimental results prove that the reduction of FeO precedes the reduction of P₂O₅.The phosphorus element in initial industrial slag mainly exists in the form of Ca₅(PO₄)₂SiO₄ and increases with the increase of P₂O₅ content. With the progress of the carbothermal reduction reaction, the Ca₅(PO₄)₂SiO₄ content in experimental slags after reduction decrease significantly. The iron element in initial industrial slag mainly exists in the form of FeO, (MgO)_0.239 (FeO)_0.761 and Ca₂Fe₂O₅ and disappear after carbothermic reduction reaction. In the range of P₂O₅ content of 4–8 wt.%, P₂O₅ content has little effect on the thermodynamic trend of the formation of phosphorus-containing phase Ca₅(PO₄)₂SiO₄, but it is not good for the thermodynamic trend of gasification dephosphorization reaction in the carbothermic reduction process. Therefore, the increase of P₂O₅ content is not conducive to the occurrence of carbothermic reduction gasification dephosphorization reaction.