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

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 P 2 O 5 content by carbothermal reduction after melting and modification are systematically analyzed. The results show that the reduction rates of P 2 O 5 and FeO decrease with the increase of P 2 O 5 content at 1450 °C and the basicity of 1.0. Meanwhile, the experimental results prove that the reduction of FeO precedes the reduction of P 2 O 5 .The phosphorus element in initial industrial slag mainly exists in the form of Ca 5 (PO 4 ) 2 SiO 4 and increases with the increase of P 2 O 5 content. With the progress of the carbothermal reduction reaction, the Ca 5 (PO 4 ) 2 SiO 4 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 Ca 2 Fe 2 O 5 and disappear after carbothermic reduction reaction. In the range of P 2 O 5 content of 4–8 wt.%, P 2 O 5 content has little effect on the thermodynamic trend of the formation of phosphorus-containing phase Ca 5 (PO 4 ) 2 SiO 4 , but it is not good for the thermodynamic trend of gasification dephosphorization reaction in the carbothermic reduction process. Therefore, the increase of P 2 O 5 content is not conducive to the occurrence of carbothermic reduction gasification dephosphorization reaction.