The ironmaking processes that directly use iron ore fines as raw material are under development and receiving more and more attention. In a flash reduction process, both the thermal decomposition reaction and the reduction reaction of ore fines are extremely fast and cause loss of oxygen from iron oxides. However, it is difficult to distinguish between the thermal decomposition and reduction during the conversion from hematite to magnetite. In this work, the thermal decomposition behavior of hematite ore fines with different particle sizes is investigated by using a thermogravimetric analyzer (TGA). The kinetic parameters are calculated based on the Coats–Redfern method and then verified by the Satava–Sestak method. The F2 model is identified as the most probable mechanism function under the present experimental conditions. The average values of activation energy and the pre-exponential factor are 1256 kJ mol −1 and 1.94 × 10 41 s −1 , respectively. The internal morphology of the fine hematite particle with partial decomposition is observed to further investigate the reaction mechanism. Moreover, the relative contribution of the two kinds of chemical reactions (thermal decomposition and gaseous reduction) to the overall conversion process from hematite to magnetite is investigated by kinetic calculations based on the obtained reaction rate equations.

中文翻译：

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赤铁矿细粉高温热分解行为动力学研究

直接以铁矿粉为原料的炼铁工艺正在开发中并受到越来越多的关注。在闪速还原过程中，矿粉的热分解反应和还原反应都非常快，会导致氧化铁中的氧气流失。然而，很难区分赤铁矿向磁铁矿转化过程中的热分解和还原。在这项工作中，使用热重分析仪 (TGA) 研究了不同粒度的赤铁矿细粉的热分解行为。动力学参数基于 Coats-Redfern 方法计算，然后通过 Satava-Sestak 方法验证。F2 模型被认为是目前实验条件下最可能的机制函数。活化能和指前因子的平均值分别为1256 kJ mol -1 和1.94 × 10 41 s -1 。观察部分分解的赤铁矿细颗粒的内部形貌以进一步研究反应机理。此外，基于获得的反应速率方程，通过动力学计算研究了两种化学反应（热分解和气体还原）对从赤铁矿到磁铁矿的整个转化过程的相对贡献。