台灣的轉爐煉鋼製程中一年約產生160萬噸轉爐石，為了多元資源化，需要有合適的廠內資源化方法。轉爐石中含有CaO、FeO和SiO2等成份，可作為一貫作業煉鋼製程中燒結廠之添加料，但其中含有P2O5。若直接使用，將會發生回收後鐵水磷含量過高的問題，因此對轉爐石進行脫磷是必要的。再者，磷為重要的戰略物資，在農業與工業方面有廣泛的應用，而台灣為天然資源匱乏的國家，磷的來源依賴進口，若可藉由轉爐石脫磷製程中回收並萃取其中的磷元素，成為磷元素的新來源，將使轉爐石回收之經濟效益最大化，解決轉爐石去化的問題。
為了使整體氧化還原反應在液相中有比固相良好的反應效率，因此將轉爐石加熱至熔融為再利用過程中的重點。然而從相圖中之成分評估，原始轉爐石之熔點通常都在1700℃以上，若是直接加熱至熔融，將不利於能源的消耗，因此藉由改質降低轉爐石之熔融溫度將是加快脫磷反應與節能之方向。
本研究之上半部分遂以不同比例SiO2對爐石進行改質，得到不同鹽基度(B2)之改質轉爐石後，再進行B2對軟熔溫度改變之影響。結果顯示使用SiO2對轉爐石改質時，改質前後的軟熔溫度皆遠低於由三元相圖預估之熔點，並小於1500℃。而改質為B2=1.2時，可將流動溫度降至1300 ℃，為研究樣品中能兼顧低熔點與較少添加劑者。
本研究之下半部分則是利用不同B2的改質轉爐石與石墨混合，在高溫進行碳熱還原實驗，並透過後續之SEM/EDS分析與ICP分析分別獲得鐵相脫磷率、磁選後之感磁相磷分配率、氣相磷分配率，以評估反應溫度、B2、(C/Ored)mol等參數對於脫磷率之影響。從反應溫度分析，不論任何B2值轉爐石中之氧化鐵在1050~1100℃皆開始大量還原，然而氧化磷被還原的溫度會隨著B2增加而提升。從B2分析，B2在2以下可間接計算磷藉由氣體逸散，B2=1.5能藉由ICP分析得到最高約90%之脫磷率，B2=1.2樣品則是能以磁選分離之手法得到最接近EDS分析之鐵相脫磷率，且其感磁相之成分為鐵、磷以外雜質最少者，具有成為添加料之潛力。從C/O分析可知只要提升至C/O=2就能顯著提升感磁相脫磷率。
最後以B2=1.2樣品為例模擬實際製程之物質流，在內含之所有磷中，經碳熱還原反應後約有23%磷藉由氣相逸散。然而蒐集磷氣之方式仍需進一步研究。

There are CaO, FeOn, and SiO2 included in basic oxygen furnace (BOF) slag, which can be applied to the additives of sintering process. However, if BOF slag is recycled in this way without phosphorus elimination, there will be excess phosphorus in the molten iron after blast furnace process. On the other hand, BOF slag can be a promising resource of phosphorus if phosphorus is separated from BOF slag appropriately.
In order to increase the reaction speed of carbothermic reduction, the process should be in the liquid phase instead of solid phase. However, melting unmodified BOF slag is an energy-consuming way to get a liquid reaction, so modifying BOF slag to decrease the melting temperature is the appropriate way to increase the reaction speed and decrease the energy-consumption.
In this study, we investigated the softening and melting behavior of BOF slag at first. SiO2 is added to modify the basicity (wt%CaO/wt%SiO2 ,B2) of BOF slag, and monitored the softening and melting temperatures of each samples. The results show whether the slag was modified or not, the flow temperatures of all samples are lower than 1500 ℃. Also, the B2=1.2 modified slag has the flow temperature that is lower than 1300 ℃.
Then, different modified slags were mixed with graphite and conducted carbothermic reduction. Samples after experiments were analyzed by titration of iron element, SEM/EDS and ICP to get the metallization ratio of iron, phosphorus distribution ratio of iron phase, gaseous phase, and magnetic phase to discuss the effect of reaction temperature, B2, and C/O ratio. In the view of reaction temperature, FeO in all samples can be mostly reduced at 1000-1200 ℃, however the reduced temperature of P2O5 is increased with increasing basicity. In the view of B2, the phosphorus distribution in gaseous phase can be calculated if the B2 of modified slag is lower than 2. If the B2 of the slag is 1.2, the phosphorus distribution of magnetic phase is the nearest to that of ideal iron phase among all samples, also, the magnetic phase has the least impurities among all samples. In the view of C/O ratio, the phosphorus distribution of magnetic phase is increased with increasing C/O ratio.

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