Development of Reduction model of Ore Powder in a Fluidized Bed (Fundamental Research on lronmaking by Smelting Reduction)

本研究的主要结果如下：1.提出了用热天平测定单个赤铁矿颗粒还原速率的方法，以确定用于流化床还原速率分析的速率参数。实验证明，所获得的速率参数可用于流化床还原速率分析.在还原孔隙率为10-20%的工业矿石的情况下，即使在直径为0.15mm的小颗粒中，颗粒中的扩散阻力也不能忽略。另一方面，对于孔隙率为30%的试剂级赤铁矿粉，还原速率受化学反应控制.测量了不同形状（球形、圆柱形和平板形）的大尺寸试样的压下速率，并从数据中获得了速率参数。速率参数随形状因子的变化而变化.建立了一个考虑流化床内颗粒粒度分布的还原模型。实验表明，该模型在床层中颗粒偏析严重的情况下是有效的.建立了一个考虑流化床还原过程中颗粒降解和带出导致颗粒直径减小的数学模型。发现由于颗粒的降解，还原速率明显加快.颗粒的降解是由还原和流化引起的。在700 ℃的流化床还原中，降解最为显著。

The main results of this research are as follows.1. The measurement method of reduction rate of single hematite particle by using thermo-balance was developed for the determination of rate parameters which can be used for the reduction rate analysis in a fluidized bed. It was confirmed in experiment that the obtained rate parameters can be used for the reduction rate analysis in a fluidized bed.2. The diffusion resistance in a particle was not able to be ignored in the case of reduction of commercial ores having the porosity of 10-20% even in the small particle of 0.15mm in diameter. On the other hand, in the case of reagent grade hematite powder having the porosity of 30%, reduction rate was controlled by chemical reaction.3. Reduction rate of the large size samples having various shape (sphere, cylinder, and plate) was measured and rate parameters were obtained from the data. The rate parameters varied with the value of shape factor.4. A reduction model considering the particle size distribution in a fluidized bed was developed. It was clarified in experiment that this model was effective in the case that particle segregation was significant in the bed.5. A mathematical model considering a decrease of particle diameter by degradation and carry-out of particles from the bed during the fluidized bed reduction was developed. It was found that the reduction rate became faster apparently because of the degradation of particles.6. Degradation of particles resulted from the reduction and the fluidization. Degradation was most significant in the fluidized bed reduction at 700ﾟC.