氧化铁石墨固相还原非等温反应动力学

Non-isotherm kinetics of iron oxide reduction by graphite

准确测试固固反应,如铁矿炭还原反应的动力学在科学研究和实际应用中均具有重要意义。利用热重程序升温的方法研究了氧化铁石墨还原的固固反应特性,在惰性气氛下分别考察了研磨与浸渍混合后焙烧制得的Fe2O3/C样品的失重曲线,采用Flynn-Wall-Ozawa公式和Coats-Redfern公式相结合的方法分别求算了两种混合样品的固固反应动力学参数,研究发现氧化铁在炭表面的聚集形态与其活化能变化规律直接相关,且浸渍焙烧法所得样品的活化能符合强吸热反应活化能变化规律。结合固体原位XRD表征与气体产物在线分析手段,发现在初始阶段Fe2O3即可与C直接反应生成Fe3O4和CO2。该反应的活化能约为530kJ.mol-1,反应机理为二级化学反应模型。

The accurate measurement of solid-solid reaction kinetics, such as reduction of iron oxide by carbon, is of great significance in scientific research and practical applications. In this paper solid-solid reaction characteristics between iron oxide and graphite was studied using thermogravimeter （TG） measurement for both samples prepared respectively by directly mixing and grinding graphite and Fe2O3 as well as by impregnating Fe2O3 on the graphite. Their reaction kinetic parameters were calculated using the Flynn-Wall-Ozawa and Coats-Redfern equations. The variation trends of activation energy are related with the aggregation morphology of Fe2O3 on the surface of carbon. The reduction kinetics for impregnated sample is of the characteristics of strong endothermic reaction. Combining the results of XRD characterization and online gas determination, in the initial stage of Fe2 O3 reduction the products are Fe3 O4 and CO2, reaction follows second order reaction mechanism and activation energy is about 530 kJ . mol- 1.