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

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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.