Recovery of valuable elements from molten modified phosphorous steel slag by carbothermic reduction

For the recovery of valuable elements(Fe,P,Mn) in phosphorus-containing converter slag and the utilization of disposed slag,the thermodynamic conditions and influence laws of carbothermal reduction and recovery of valuable elements from the phosphorous-containing steel slag after melting and reforming were systematically analyzed through the theoretical calculation,experiments in resistance furnace,induction furnace test and other research methods. The research results showed that,the reduction temperature was 1 723 K,the basicity was 1.0-2.0,and the low basicity was beneficial to the reduction of Fe₂O₃ and P₂O₅ and the recovery of Fe and P resources in the slag. When the basicity of slag was 1.0,the reduction rates of Fe₂O₃,P₂O₅ and MnO could reach 99.50%,84.47% and 3.26% respectively,and the recovery rates of Fe and P in slag were 99.50% and 68.69% respectively. When the basicity was 1.5,the reduction rates of Fe₂O₃ and P₂O₅ were 90.45% and 63.73% respectively,which were lower than that of when the basicity was 1.0. When the basicity was 2.0,the reduction rate of Fe₂O₃ in slag was 71.43%,slag and iron was not separated completely. At the condition of that basicity was 1.0,the temperature was 1 723 K,the recovery rate of Fe was over 99% and that of P in the slag was 47.18%,in induction furnace experiments on carbonthermal reduction of molten modified industrial slag. Through thermodynamic analysis,it was found that FeO and P₂O₅ were easier to be reduced by carbon than MnO. At the same time, FeO and P₂O₅ were reduced firstly,and MnO began to be reduced after 20 min in slag,the MnO content in slag decreased slightly during the whole reduction process. at the end of the reduction process. The content of FeO,P₂O₅ and MnO after carbonthermal reduction in slag were 0.07%,0.93% and 2.83% respectively. Using FactSage to compare the phase composition of modified slag before and after reduction,it could be seen that the iron-containing phase(Ca₃Fe₂Si₃O₁₂) in steel slag was effectively controlled,calcium phosphate content decreased obviously,and olivine content increased greatly,which improved the application range of steel slag. A reference for recycling and resource utilization of valuable elements in steel slag containing phosphorus is provided.