在煉鋼過程中，每噸鋼可產生100-150公斤的鹼性氧氣轉爐石副產物，造成了嚴重的環境污染和資源浪費。轉爐石含有大部分有價值之元素，其中含40–60 wt% CaO、10–20 wt% SiO2、10–30 wt% Fe、5–15 wt% MgO, 0–5 wt% P2O5以及其他微量成分。不幸的是，其內部游離石灰的比例甚高，亦隨老化而水化，導致膨脹等問題，不允許在道路建設或土木工程中使用，限制了其適用性。此外，轉爐石含有大量濃度的磷，對於回爐煉鋼的再利用帶來負面影響，磷會被還原並溶解在鐵水中。隨著程序反覆進行，磷會在鐵水中積累，最後造成鐵的延展性與抗腐蝕性降低，使得鐵回收成為現在的阻礙。因此，針對膨脹問題以及對含磷在內的有價元素進行回收，以實現有助於爐石中鐵或石灰部分的再利用和回收途徑。本研究提出實現轉爐石的「零廢棄」處理和增值之可能解決方案，針對轉爐石以固相轉移方式，實現鐵和磷的分別富集來進行回收，通過調整鹼度、添加劑、溫度、流量以及冷卻方式來進行優化，並經過溼式磁選，調整磁力大小、時間與次數達到最佳鐵磷回收率。研究使用XRF測定磁性渣與非磁性渣的成分組成，以及使用SQUID測定樣品磁力，並以XRD了解晶相分布與生成狀況。根據研究結果，最佳條件為9 wt% SiO2和5 wt% MgO，在1350 °C下，空氣流量1 L/min，緩慢冷卻，磁力85 mT，時間3分鐘，次數1次，即可達到鐵回收率62%，磷回收率85%，磁性渣中鐵含量為64%，足以回廠煉鋼。添加SiO2調整鹼度，可抑制鐵珠生成，控制鐵與磷的富集。另外，使用空氣及MgO可以避免鐵大量還原，促鐵型態產生轉變，生成新晶相Fe3O4及(Mg, Fe)2SiO4和(Fe, Mg)SiO3等物質，並再透過時間和多階段的磁選控制優化爐渣磁選程序，結果顯示，磁選3次並持續3分鐘更有利於鐵與磷的濃縮，其中磁性渣最高鐵含量接近70%，非磁性渣中磷提高為2.7%。研究結果為提高轉爐石的回收利用提供了實際可行的方法，透過適當的操作與添加劑的應用，不僅能減少磁性渣中的磷含量，同時也增加非磁性渣作為肥料的回收可能性，進一步實現更為環保和可持續的煉鋼生產。

In steelmaking, basic oxygen furnace slag (BOF slag) is one of inevitable by-products, typically ranging from 40–60 wt% of CaO, 10–20 wt% of SiO2, 10–30 wt% of Fe, 5–15 wt% of MgO, and 0–5 wt% of P2O5, along with trace components. However, its high free lime content, coupled with aging-induced expansion, makes it unsuitable for various applications, including road construction, and its high phosphorus concentration poses challenges for steel recycling. This study proposes a zero-waste treatment approach for recovery of BOF slags and maximize resource utilization. We focus on solid-phase transformation to enrich iron and phosphorus for separate recovery. Optimization process involves adjusting basicity, adding SiO2 and MgO, controlling temperature, and gas flow, and employing wet magnetic separation. XRF, SQUID and XRD are used to determine the elemental composition, magnetic strength, and crystal phases, respectively. Optimal conditions include the addition of 9 wt% of SiO2 and 5 wt% of MgO, maintaining 1350 °C with 1 L/min of airflow and cooling for 600 minutes, using an 85 mT of magnetic field, and repeating magnetic separation for 3 minutes. This outcome can achieve iron and phosphorus recovery rates of 62.2 and 85.3%, respectively. Adjusting basicity with SiO2 suppresses excessive iron bead formation. At the same time, air and MgO prevent excessive iron reduction, promoting the formation of new substances like Fe3O4 and (Mg, Fe)2SiO4 and (Fe, Mg)SiO3, enhancing iron recovery. The optimized process for slag magnetic separation includes three steps of magnetic separation. This method maximizes the concentration of Fe in the magnetic substances (reaching nearly 70% of TFe content) and the concentration of P2O5 in the non-magnetic substances (ca. 2.7%.) The study provides a practical route to increase the BOF slag recycling and reuse amounts, contributing to environmentally friendly and sustainable steelmaking production.

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