Deep Iron-Phosphorus Separation in Hydrogen Reduction-Melting of High-phosphorus Oolitic Hematite
摘要
High-phosphorus oolitic hematite is difficult to utilize effectively due to its extremely high-phosphorus content. To achieve the goal of green and sustainable development, a deep iron-phosphorus separation process for oolitic hematite has been developed. By adding CaCO3 and CaF2 to prepare high-basicity pellets (R = 3) and applying a hydrogen reduction-melting separation process, the phosphorus removal rate in the obtained metal product can exceed 99 pct. The results indicate that, during the roasting process of high-basicity pellets at 1130 °C, CaO reacted with hematite as well as quartz and chlorite gangue minerals to form complex calcium ferrite phases, while the addition of CaF2 further promoted the formation of cuspidine phases. This inhibits the formation of difficult-to-reduce phases such as fayalite, thereby improving the reduction efficiency of the pellets. Moreover, the addition of CaF2 induces the formation of the liquid phase during the roasting process, disrupting the oolitic structure and further enhancing the reduction efficiency of the pellets. Apatite is not reduced during hydrogen reduction at 1000 °C. As metallic iron and gangue aggregate and grow, apatite incorporates into the gangue phase, forming a slag phase. The high-basicity pellets with an appropriate amount of CaF2 exhibit excellent dephosphorization performance during melting at 1600 °C. This improvement is attributed to the enhancement of thermodynamic and kinetic conditions. A low-phosphorus metal product with a phosphorus content of 0.0047 wt pct was obtained by melting hydrogen reduced high-basicity pellets containing 5 wt pct CaF2. This has achieved the goal of deep iron-phosphorus separation.