氧化球团微波加热煤基直接还原过程微观机制

Microscopic mechanism of oxidized pellets during coal-based direct reduction by microwave heating

为了解决常规加热煤基直接还原的反应时间长、还原温度高、产品质量差等问题,基于微波加热特性结合直接还原理论提出了采用微波加热进行氧化球团煤基直接还原的新工艺。通过采用扫描电镜、能谱分析仪和显微硬度计等检测手段对常规加热和微波加热煤基直接还原过程进行了深入研究,探究氧化球团微波加热煤基直接还原过程微观机制。研究结果表明,微波加热不仅改变了球团矿的微观结构和能量分配,而且在某种程度上表现出微波加热的"非热效应",常规加热时,在还原温度1050℃下还原150min,球团金属化率仅为89.38%;氧化球团煤基直接还原过程采用微波加热,从室温上升到1050℃后再等温14min,球团金属化率达到92.67%。

In order to solve the problems of conventional heating coal-based direct reduction process,such as long reduction time,high reduction temperature and poor product quality,a new coal-based direct reduction process of oxidized pellets,in which microwave was used as heating source,was proposed based on microwave heating characteristics and direct reduction theories.Scanning electron microscopy,energy dispersive spectroscopy,Vickers microhardness tester were employed for the conventional heating and microwave heating coal-based direct reduction processes,respectively,to study the microscopic mechanism of oxidized pellets during microwave heating coal-based direct reduction process.Results showed that microwave heating process not only changed the micro-structure and energy distribution of pellets,but also introduced non-thermal effect to some extent.Under the conventional heating condition,the pellet metallization rate was only 89.38% when the reduction time and reduction temperature was 150 min and 1050℃,respectively.However,a metallization rate of 92.67% was obtained after the oxidized pellets coal based direct reduction by microwave heating from room temperature to 1050℃ and then keeping 14 min.