Research on the Carbothermic Reduction Kinetic of Oolitic Hematite with Graphite at 1 173~1 473 K
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摘要: 采用热重法研究了1 173~1 373 K下鲕状赤铁矿的石墨还原动力学。研究了温度对还原度和还原速率的影响，采用不同固相反应机理函数对反应过程进行拟合，分析了不同还原阶段反应限制性环节，并对还原样品进行了XRD、SEM和EDX表征分析。结果表明，随着温度增加，还原度和还原反应速率增加，随着还原度增加，还原反应速率先增加后降低；在1 173~1 273 K和1 273~1 373 K两个阶段，反应过程分别符合界面化学反应1-（1-α）1/3和杨德模型[1-（1-α）1/3]2，对应的表观活化能分别为60.657 kJ/mol和301.662 kJ/mol，反应的限制环节分别为界面化学反应和固态扩散；还原样品的物相组成和微观形貌分析结果与前述反应动力学机理分析结果相符合。Abstract: The carbothermic reduction kinetics of oolitic hematite with graphite was investigated at temperature of 1 173~1 373 K by using thermogravimetric method.The effects of temperature on reduction degree and reaction rate were studied.The reduction reactions were fitted to several solid-state reaction mechanisms.The reaction restrictive mechanisms at different stage were analyzed.The phase composition,morphology and elementary composition of reduced samples were characterized by using XRD,SEM and EDX techniques.The research results show that the reduction degree and reaction rate increase with the increased temperature,and the reaction rates firstly increase and then decrease with the increase of reduction degree.At 1 173~1 273 K and 1 273~1 373 K,the carbothermic reductions are well fit to the interface chemical reaction model of 1-(1-α)1/3 and the Jander model of [1-(1-α)1/3]2,respectively.The corresponding activation energies are 60.657 and 301.662 kJ/mol respectively.The measured phase composition and microstructure for reduced samples are well consistent with those of reaction kinetic mechanism analysis.
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