With the depletion of high-grade iron ore, it is necessary to develop low-quality high-phosphorus iron ore through economical and sustainable solutions. In this study, we presented simultaneous enrichment of iron (Fe) and phosphorus (P) to recover P from high-phosphorus iron ore and clarified the migration of P from the original apatite to reduced iron during the direct reduction process. To capture the migration route, gas-based reduction at a relatively slow rate was conducted on two typical iron ores samples (low-grade and high-grade) at different temperatures and times. Results indicate that there are concentration gradients for P and Fe of reaction products in the low-grade iron ore at 1400 °C. The P content continuously increased in the sequence from metallic iron (Fe), wustite (FeO), and fayalite (FeSiO), to apatite (Ca(PO)F). Conversely, the content of Fe gradually decreased. During this process, P dissolved from apatite entered and formed P-bearing fayalite. For the high-grade iron ore, P-bearing fayalite with a metastable structure disappeared as the reduction progressed, and P was released and then reduced to a gaseous state, finally absorbed by metallic iron. Furthermore, when metallic iron was not formed in the initial 60 min at 1300 °C, the P migrated from the apatite to the fayalite and gas phase. As the reduction time increased from 60 min to 240 min, the formed metallic iron provided a site for gasified P, which inhibited the volatilization of P and contributed to Fe and P enrichment.

中文翻译：

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高磷铁矿石气基还原过程中铁、磷的迁移行为


随着高品位铁矿石的枯竭，有必要通过经济、可持续的解决方案来开发低品质的高磷铁矿石。在这项研究中，我们提出了同时富集铁（Fe）和磷（P）以从高磷铁矿石中回收P，并阐明了P在直接还原过程中从原始磷灰石迁移到还原铁的过程。为了捕获迁移路线，在不同温度和时间下对两种典型铁矿石样品（低品位和高品位）进行了相对较慢的气体还原。结果表明，1400°C 低品位铁矿石中反应产物中的 P 和 Fe 存在浓度梯度。 P含量按金属铁(Fe)、方铁矿(FeO)、铁橄榄石(FeSiO)、磷灰石(Ca(PO)F)的顺序连续增加。相反，Fe的含量逐渐减少。在此过程中，磷灰石中溶解的P进入并形成含磷铁橄榄石。对于高品位铁矿石，亚稳态结构的含磷铁橄榄石随着还原的进行而消失，磷被释放出来，然后还原成气态，最后被金属铁吸收。此外，当在 1300°C 的最初 60 分钟内没有形成金属铁时，P 从磷灰石迁移到铁橄榄石和气相。随着还原时间从60 min增加到240 min，形成的金属铁为气化P提供了场所，抑制了P的挥发，有助于Fe和P的富集。