碱金属对铁氧化物气-固还原行为的影响

Effect of Alkali Metal on Gas-Solid Reduction of Iron Oxide

利用热重分析的方法研究了Fe2O3在竖式电阻炉内被CO/CO2混合气体还原,Na2O对其还原行为的影响,共设计了4个成分,分别为纯Fe2O3、Fe2O3-1%Na2O、Fe2O3-3%Na2O和Fe2O3-5%Na2O。在还原过程中由于还原失氧引起的试验小饼失重量被实时记录下来,根据这些数据可以计算出还原反应速率以及化学反应的速率常数,以此来判断Na2O对Fe2O3还原性的影响。同时利用扫描电镜观察了还原后试样的微观形貌变化。研究发现:Na2O的存在将阻碍Fe2O3的还原。通过对还原后小饼的显微形貌观察,结合FeO-Na2O二元相图,发现这种负面影响主要是由于在还原过程中产生液相引起的。另外,还检测了还原前后试验小饼的孔隙率和体积变化。检测结果确认:还原后含Na2O的试验小饼的孔隙率和体积都有所下降。分析认为这种现象同样归因于还原过程中液相的产生。

Fe2O3 and Fe2O3 doped with Na2O from 1.0 to 5.0 mass percent compacts were isothermally reduced at various temperatures from 1 073 to 1 273 K with CO/CO2 mixed gas in a vertical resistance furnace.To determine the effect of Na2O on the reduction of Fe2O3 compacts,mass loss due to oxygen removal was continuously recorded from which the reduction rate and rate constant was obtained.The morphology change was also observed by SEM.The results show that Na2O retards the reduction of Fe2O3 compacts.Morphological examination of reduced compacts and the binary phase diagram of FeO-Na2O show liquid phase formation during the reduction,which decreases the rate of reduction.Porosity and volumetric expansion of reduced compacts were investigated,which shows that the volume and porosity of reduced Fe2O3-Na2O compacts are both decreased with higher Na2O content due to the existence of liquid phase.