Reduction Rates for the Mixture of Iron Oxide and Zinc Oxide, and ZnFe_2O_4 with CO-CO_2 Gas Mixtures

为了分析氧化铁和氧化锌的混合物以及ZnFe_2O_4与CO-CO_2混合气体的还原速率，首先在973 ~ 1173 K的温度范围内，在纯赤铁矿球团和纯氧化锌球团中进行了还原实验。每次还原的实验数据分别基于未反应核模型和收缩模型进行混合控制动力学分析。基于双界面模型，考虑ZnO和FeO活性的混合控制动力学分析了氧化铁和氧化锌混合物和ZnFe_2O_4的混合控制动力学数据。研究结果总结如下：1。对于赤铁矿球团，用反应速率常数和有效扩散系数计算的还原曲线与实验数据吻合较好。对于氧化锌球团，采用反应速率常数计算的还原曲线较好地再现了实验数据。并发现在实验条件下，总速率受化学反应控制。对于氧化铁和氧化锌的混合物，以及ZnFe_2O_4，除氧化锌在1173 K， 92.0%CO条件下的还原曲线存在延迟外，用氧化锌和FeO的速率参数和活度计算得到的还原曲线与实验数据吻合较好。实验结果和基于双界面模型的计算表明，铁还原蒸馏过程第一还原阶段的最适宜条件是较低的温度，约为973 K。

In order to analyze the reduction rates for the mixture of iron oxide and zinc oxide, and ZnFe_2O_4 with CO-CO_2 gas mixtures, first of all reduction experiments were carried out in pure hematite pellet and pure zinc oxide pellet in the temperature range from 973 to 1173 K. Experimental data for each reduction were analyzed in terms of the mixed-control kinetics based on the unreacted core model and the shrinking model, respectively. Then experimental data for both the reductions of the mixture of iron oxide and zinc oxide, and ZnFe_2O_4 were analyzed in terms of the mixed control kinetics based on the two-interface model, in which activities of ZnO and FeO were taken into account. The results are summarized as follows :1. For hematite pellets the calculated reduction curves by using the reaction rate constant and the effective diffusivity are in satisfactory agreement with the experimental data.2. For zinc oxide pellets the calculated reduction curves by using the reaction rate constant finely reproduced the experimental data. And it was found that the overall rate is controlled by chemical reaction under the experimental conditions.3. For both the mixture of iron oxide and zinc oxide, and ZnFe_2O_4 the calculated reduction curves by using the rate parameters and activities of ZnO and FeO are in satisfactory agreement with the experimental data, except the reduction curve of zinc oxide on the experimental condition of 1173 K, 92.0%CO on which the experimental data of zinc oxide exhibited delay as compared with the calculated reduction curves.4. It was found from experimental results and calculations based on the two-interface model that the most suitable condition for the first reduction stage of the iron-reduction distillation process was the rather low temperature such as about 973 K.