| Converter steel slag is a kind of byproduct in steelmaking process with the characteristic of huge output but low utilization ratio, The recycling of slag in metallurgy field which cause the cumulation of phosphorous may aggravate the smelting process. The dephosphorization technology on the purpose of improving the internal utilization of slag didn’t take the recycling and efficient reuse of phosphorous resource into consideration. Therefore, the promotion of phosphorous enrichment in slag and the improvement of phosphorous content in phosphorous-rich phase as well as the recovery of high-grade phosphorous resource are of great significance to the promotion of energy conservation and emission reduction as well as the efficient and comprehensive utilization of metallurgical slag.The kinetics in the process of phosphorous enrichment in CaO-SiO2-FetO-P2O5slag is investigated based on the problems in the enrichment and recovery of phosphorous in slag as well as the transfer behavior of phosphorous in molten slag. Phosphorous distribution in molten slag and different position of2CaO-SiO2particles at different temperature as well as the enrichment mechanism of phosphorous is also introduced, In addition, the restrictive step and kinetics model of the phosphorous enrichment from slag to2CaO·SiO2particle was also discussed. The results are as follows:(1) The phosphorous in slag existed as2CaO·SiO2-3CaO·P2O5solid solution in2CaO·SiO2phase,2CaO·SiO2was the enrichment place of phosphorous in slag.(2) Phosphorous in slag diffused to the surface of a2CaO·SiO22particle through macroscopic diffusion, the solid solution reaction only occurred on the surface of2CaO·SiO2particles to form the phosphorous boundary layer.2CaO·SiO2-3CaO·P2O5solid solution product layer was formed surrounding the unreacted2CaO·SiO2particle. Then the phosphorous in slag diffused through the solid solution product layer to react with the unreacted2CaO·SiO2particle, and the product layer became thicker with time.(3) Solid solution reaction between phosphorous and2CaO·SiO2in slag was occurred at1350℃and1400℃,2CaO·SiO2particles with diameter less than50μm completely changed to particles with the composition of2CaO·SiO2-3CaO·P2O5solid solution after a certain time, but in the case of2CaO·SiO2particles with larger diameter, only the rim part of a particle can change to2CaO·SiO2-3CaO·P2O5solid solution.(4) The phosphorous content decreased from slag to the interface between slag and2CaO·SiO2particle, the same tendency occurred from the interface between slag and2CaO·SiO2particle to the reaction interface. So the process of phosphorous enrichment in CaO-SiO2-FetO-P2O5slag can be recognized with two control steps of external diffusion in slag and internal diffusion from2CaO·SiO2-3CaO·P2O5solid solution to reaction interface.(5) High temperature can improve the phosphorous enrichment from slag to2CaO·SiO2particle, the phosphorous content in CaO·SiO2-3CaO·P2O5solid solution obtained at1400℃was higher than obtained at1300℃.(6) The phosphorous apparent diffusion coefficient in CaO-SiO2-FetO-P2O5slag at1350℃and1400℃was2.70×10-14m2/s and2.98×10-14m2/s, respectively. And the phosphorous apparent diffusion activation energy was4.57×104J/mol. |
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