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

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.