ABSTRACT Iron ore fines was isothermally and non-isothermally reduced with CO and the total mass loss was continuously recorded. The different phases developed during the reduction process were identified by X-ray diffraction analysis. The structural changes accompanying the reduction reactions were microscopically examined. During the isothermal reduction tests, temperature has a significant effect on the reduction reaction. At a given temperature, the highest rate was obtained at initial stages whereas the minimum rate was observed at the later stages due to the formation of dense iron layer. The activation energy values (Ea) at the early stages was 39.23kJ mol-1 revealed that the reduction is most likely controlled by a combined effect of gaseous diffusion and interfacial chemical reaction mechanism. At later stages, the Ea values were 54.19 kJ mol-1 indicated that the interfacial chemical reaction is the rate controlling mechanism. Testing of the mathematical formulations derived from the gas-solid reaction model confirmed these controlling mechanisms. The non-isothermal reduction experiments were carried out using different heating rates which showed a considerable effect on the degree of reduction. The reduction conversion continuously increased with rise in temperature. The reduction mechanism was predicted from model free and model fitting. The activation energy values were ranging from 135-40 kJ.mol-1 indicating that gas diffusion is the rate controlling step.

中文翻译：

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一氧化碳气氛中赤铁矿等温与非等温还原的对比研究

摘要铁矿石细粉用 CO 等温和非等温还原，并连续记录总质量损失。通过 X 射线衍射分析确定了还原过程中形成的不同相。显微镜检查伴随还原反应的结构变化。在等温还原试验中，温度对还原反应有显着影响。在给定温度下，由于形成致密的铁层，在初始阶段获得了最高速率，而在后期阶段观察到了最小速率。早期的活化能值 (Ea) 为 39.23kJ mol-1，表明还原很可能受气体扩散和界面化学反应机制的综合影响。在后期阶段，Ea 值为 54。19 kJ mol-1 表明界面化学反应是速率控制机制。对源自气固反应模型的数学公式的测试证实了这些控制机制。使用不同的加热速率进行非等温还原实验，这表明对还原程度有相当大的影响。随着温度的升高，还原转化率不断提高。通过模型自由和模型拟合来预测减少机制。活化能值范围为 135-40 kJ.mol-1，表明气体扩散是速率控制步骤。使用不同的加热速率进行非等温还原实验，这表明对还原程度有相当大的影响。随着温度的升高，还原转化率不断提高。通过模型自由和模型拟合来预测减少机制。活化能值范围为 135-40 kJ.mol-1，表明气体扩散是速率控制步骤。使用不同的加热速率进行非等温还原实验，这表明对还原程度有相当大的影响。随着温度的升高，还原转化率不断提高。通过模型自由和模型拟合来预测减少机制。活化能值范围为 135-40 kJ.mol-1，表明气体扩散是速率控制步骤。