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

为了分析氧化铁与氧化锌、氧化锌与CO-CO_2混合气体的还原速率，首先在973~1173K温度范围内对纯赤铁矿球团和纯氧化锌球团进行了还原实验，分别用基于未反应核模型和收缩模型的混合控制动力学对实验数据进行了分析。然后，基于双界面模型，考虑了氧化锌和氧化锌的活度，用混合控制动力学方法分析了氧化铁和氧化锌混合还原和氧化锌还原的实验数据。研究结果如下：1.对于赤铁矿球团，利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。对于氧化锌球团矿，利用反应速率常数计算的还原曲线较好地再现了实验数据。研究发现，在实验条件下，总反应速率受化学反应控制。对于氧化铁和氧化锌的混合物以及氧化锌和氧化锌，用速率参数和氧化锌和氧化亚铁的活度计算的还原曲线与实验数据吻合较好，但在1173K、92.0%CO的实验条件下，氧化锌的还原曲线与计算的还原曲线相比有延迟。根据实验结果和基于双界面模型的计算，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，如973K左右。

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.