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针对气固直接还原工艺中存在着气体利用率低和还原供热不足等问题,利用恒温热重分析(TG)法,研究了氢/碳比率对白云鄂博铁精矿还原速度的影响。结果表明,在还原试验开始后40 min内,还原速率随wH2/wCO比增加而增大,使得Fe2O3→Fe3O4反应时间缩短。基于气相内扩散和界面反应的球团还原速度方程均能较好地处理本研究的数据,得到了反应速度常数与wH2/wCO的关系为:k界面=-0.1975+0.3 575wH2/wCO,k扩散=0.171 01+0.269 7wH2/wCO。根据Arrhenius方程计算出界面反应和气相内扩散活化能分别为26 k J/mol和44 k J/mol,因此本研究条件下限制性环节为气体内扩散控制。
In order to solve the problems of low gas utilization and insufficient heating in reduction of gas-solid direct reduction process, the effect of hydrogen / carbon ratio on the reduction rate of Baiyunebo iron ore concentrate was studied by means of thermogravimetry (TG). The results show that the reduction rate increases with the increase of wH2 / wCO ratio within 40 min after the start of the reduction test, resulting in a shorter reaction time of Fe2O3 → Fe3O4. The reduction rate equation of pellets based on intra-gas diffusion and interfacial reaction can well deal with the data of this study. The relationship between the reaction rate constant and wH2 / wCO is as follows: k interface = -0.1975 + 0.3 575wH2 / wCO, diffusion = 0.171 01 + 0.269 7wH2 / wCO. According to the Arrhenius equation, the activation energy of interfacial reaction and diffusion in the gas phase are 26 kJ / mol and 44 kJ / mol, respectively. Therefore, the limiting part in this study is the gas diffusion control.