机械活化条件下超细铁矿粉一氧化碳还原特性及机理

Reduction characteristics and mechanism of ultrafine iron ore powder by CO under mechanical activation

采用热重法研究了不同机械活化程度的超细铁矿粉一氧化碳还原特性,并对其还原反应机理进行了分析和讨论。研究结果表明,机械活化有利于一氧化碳还原铁矿粉,机械活化时间越长,反应特征温度越低,活化480 min的铁矿粉的反应峰值温度比未活化的矿粉低217 K。机械活化时间越长,反应活化能越低,但反应机理未发生变化,界面反应一直是限制性环节,活化480 min后的铁矿粉的反应活化能比未活化时低31.23 kJ/mol。机械活化对于一氧化碳的还原铁矿粉的逐级反应进程有明显影响,对于未活化的铁矿粉而言,逐级反应层次不分明,而对于活化后铁矿粉的逐级反应层次分明,而且活化时间越长,层次越分明。

Low carbon, green, and high-efficiency ironmaking is an essential direction for developing ironmaking technology. Low-temperature reduction of ultra-fine iron ore powder can reduce reaction temperature and carbon dioxide emission, which has broad development prospects. The carbon monoxide reduction characteristics of ultrafine iron ore powder with different degrees of mechanical activation were studied by thermogravimetry. The reduction reaction mechanism was analyzed and discussed by KAS(Kissinger Akahira Sunose) method, kinetic model-fitting method,and activation energy judgment method. The results showed that mechanical activation is conducive to the reduction of iron ore powder with carbon monoxide. When the mechanical activation time was longer, the reaction characteristic temperature was lower. Before 120 min of mechanical activation time, the effect of mechanical activation time on reduction characteristic temperature was greater than that after 120 min. The reaction starts temperature of the sample powder with an activation time of 480 min was 523 K, which was 87 K lower than that of the non-activated sample powder. And the peak temperature of the reaction rate was 1108 K, which was 217 K lower than that of non-activated sample powder. When the mechanical activation time was longer, the reaction activation energy was lower,but the reaction mechanism had not changed, and the interfacial reaction had always been a restrictive step. The activation energy of iron ore powder after activation for 480 min was 31.23 kJ/mol lower than that without activation. With the increase in mechanical activation time, the reason why the activation energy of the reaction decreased was that the mechanical activation reduced the particle size of iron ore powder and the average particle size of iron ore powder, which was more conducive to the diffusion of carbon monoxide gas. Mechanical activation significantly impacted the step-by-step reaction process of carbon monoxide reduction in iron ore powder. For the unactivated iron ore powder, the step-by-step reaction level was not clear, but for the activated iron ore powder, the step-by-step reaction level was clear.