CAJ | 학술논문

采用热重法实验研究了773~1273 K氧化亚铁的等温氢还原动力学，发现873 K温度以上，反应动力学曲线有明显转折，说明反应机理发生了变化.在973~1073 K的温度范围，出现了反常的温度效应，即反应速率随温度升高而减小.为讨论产物结构对反应动力学的影响，分别对不同温度的反应产物，以及一定温度不同还原状态(不同反应时间)的产物进行形貌观察.结果显示，随着反应温度升高，还原产物表面的孔洞增多，枝状特征显著增加，而973 K和1023 K时表面的烧结现象明显.一定温度下，随着反应进行，表面的孔洞增多，并逐渐出现烧结.973 K和1023 K温度条件下反应产物大体保留原来的大颗粒外形，而1173 K时还原2 min开始，就大量出现枝状产物，并逐渐烧结.结合产物形貌变化和反应动力学曲线，反应前期为界面化学反应控速，随着反应进行，还原的金属铁发生烧结现象，致密的结构阻碍了产物气体向外扩散，反应控速环节转变为产物气体的外扩散，还原速率也随之降低.
채용열중법실험연구료773~1273 K양화아철적등온경환원동역학，발현873 K온도이상，반응동역학곡선유명현전절，설명반응궤리발생료변화.재973~1073 K적온도범위，출현료반상적온도효응，즉반응속솔수온도승고이감소.위토론산물결구대반응동역학적영향，분별대불동온도적반응산물，이급일정온도불동환원상태(불동반응시간)적산물진행형모관찰.결과현시，수착반응온도승고，환원산물표면적공동증다，지상특정현저증가，이973 K화1023 K시표면적소결현상명현.일정온도하，수착반응진행，표면적공동증다，병축점출현소결.973 K화1023 K온도조건하반응산물대체보류원래적대과립외형，이1173 K시환원2 min개시，취대량출현지상산물，병축점소결.결합산물형모변화화반응동역학곡선，반응전기위계면화학반응공속，수착반응진행，환원적금속철발생소결현상，치밀적결구조애료산물기체향외확산，반응공속배절전변위산물기체적외확산，환원속솔야수지강저.
The isothermal hydrogen reduction kinetics of FeO powder at 773 ~1273 K was investigated by thermogravimetry. Above 873 K, there was a turning point in the kinetic curve, which indicated that the reduction mechanism changed. An unusual temperature effect that the reduction rate decreased with increasing temperature was observed from 973 K to 1073 K. To discuss the effect of product structure on the reduction rate of iron oxide, the morphology of samples reduced at different temperatures and for different reaction time was observed by scanning electron microscopy. It was shown that holes on the sample surface increased gradual-ly, the dendritic characteristic appeared with increasing temperature, and the sintered phenomenon was obvious at 973 K and 1023 K. At a certain temperature, holes on the sample surface increased and the sintered phenomenon appeared gradually with prolonging reac-tion time. At 973 K and 1023 K, the sample kept fairly the original shape, but at 1173 K, just reacted for 2 min, a large number of dendritic products appeared and sintered gradually. Combining the morphology and kinetic curves, it can be summarized that interfa-cial chemical reaction is the rate-limiting step in the initial stage of hydrogen reduction. But as the reaction proceeds, the reduced iron sinters and the compact structure of the reduced product hinders the outward diffusion of produced gas. The rate-limiting step changes to the outward diffusion of produced gas, which leads to the decrease of the reduction rate of iron oxide by hydrogen.