著眼於鋼鐵產業最前段的煉鐵製程部分，期望用最少的成本以及對環境最友善的方法來得到生產量最多的金屬鐵，發展至今已有許多有別於高爐的煉鐵製程，其中高料層煉鐵製程為相當具有開發潛力的技術。
比起傳統之煉鐵製程原料，用於高料層煉鐵製程的複合球團，由於其內部氧化鐵與還原劑顆粒之間的接觸更緊密，所以可知球團原料彼此間的狀態，巨觀如原料種類、球團大小、密度等；微觀如粒徑大小、分布情形、碳原子與氧原子間距離等，都會影響碳熱還原反應速率。又對高料層煉鐵製程而言，爐頂之熱輻射若能傳的更深，不但可增加底層球團還原度而提升整體產率，且同時達到提高能源使用效率的效果。而不崩塌甚至縮小的球團便能幫助達成此目的。
本研究改變球團原料的初始狀態，參數包括Fe2O3粒徑、混合球磨和C/O三種，藉由觀察單顆球團於碳熱還原過程中之還原速率與體積變化，解析造成差異之原因與機制。實驗結果顯示，不同原料初始狀態影響還原速率的原因皆不同。Fe2O3粒徑對還原速率造成的影響主要在氧化鐵還原反應開始至Fe3O4還原成FeO的溫度區間，原因為原料間還互相保有初始的接觸狀態。混合球磨的處理可使原料分布均勻，使氧化鐵的還原更有效率，造成整體還原速率的提升。對越大的C/O而言，雖然還原速率越快，但同時也降低還原效率，於還原最終導致還原劑的浪費。而針對球團於還原過程中的體積變化，可發現溫度與原料本身的燒結性質才是影響還原過程中體積變化率的關鍵因素，當初始原料粒徑小、比表面積大、分布均勻，以及環境溫度達到物質燒結溫度時，對體積收縮有較大的影響與貢獻。

By using composite pellets as material for tall bed new iron-making process, the initial state of it has great impact on reduction behavior, including reduction rate and accompanying volume change, and both are crucial to productivity.
In this study, variation during reduction process resulting from different initial state of raw material is examine by gas analyzer. In the meanwhile, volume change of pellets is recorded through an in-situ digital camera. Interrupted experiment is aimed to analyze microstructure and element composition of pellets using SEM.
Results show that, for initial state of different particle sizes, the amount of reaction contact area was the main reason that affected reduction rate. Once the reduction temperature exceeded 1100 oC, iron oxides particles then sintered, causing variation in reduction rate leveled off. As to the parameter, period of mixed milling, when iron oxides and reductants were evenly distributed, reduction reaction became more efficient, thus promoting the overall reduction rate. Additional, when initial state of C/O ratio was increased, reduction rate also became faster but following a decreasing of reduction efficiency, which results in reductants waste at the end of the process. On the other hand, the volume change during reduction reaction was observed to have strong relation with temperature and sintering property of raw material itself.

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