铁精粉单颗粒高温还原过程中的演化特征

Evolution Characteristics of Single Iron Concentrate Particle During the High-Temperature Reduction Process

采用高温热台显微镜原位研究了铁精粉单颗粒在高温及CO气氛下还原过程的演化特征。通过原位实验记录了铁精粉单颗粒的高温还原过程,并利用拉曼光谱仪验证了还原反应产物(单质铁)。结果表明,颗粒表面出现单质铁的时间受温度影响显著,受气体流量影响小。其中,当温度从1100℃升至1300℃时,单质铁的生成时间缩短约75%;当温度从1300℃升至1400℃时,单质铁的生成时间基本不变。当温度为1100~1350℃时,铁精粉颗粒在还原过程中表面会产生瘤状物,且瘤状物尺寸随着温度升高而增大。引入瘤状物长宽和的平均值为特征尺度l,当还原温度由1100℃升高至1350℃时,l由6μm增大至15μm。当还原温度高于1400℃时,铁精粉颗粒出现熔融态的产物分层现象:内层为还原铁,中层为熔融氧化亚铁被还原的树根状金属铁,外层为含有Al、Ca和Si等元素集聚的铁渣。

The evolution characteristics of the reduction process of single iron concentrate particles under high temperature and CO atmospheres were tested in-situ experiment with a high temperature stage microscope.The high-temperature reduction process of the single iron concentrate was recorded via in-situ experiment,and the reduced product(elemental iron)was verified by Raman spectrometer.The results showed that the initial formation time of elemental iron on the particle surface was mainly determined by temperature,and the influence of the gas flow rate was smaller.The initial formation time decreased by about 75%when the reduction temperature increased from 1100℃to 1300℃,but it hardly changed when the temperature increased from 1300℃to 1400℃.Nodular structures were found on the surface of iron concentrate particles during the reduction process between 1100℃and 1350℃,and their sizes increased with the rising reduction temperature.A characteristic number l,which was self-defined as the mean value of the length and width of the particles,increased from 6μm at 1100℃to 15μm at 1350℃.When the reduction temperature was above 1400℃,layered melting products were observed for the iron concentrate particle.The product on the core was reduced iron,the one on the second layer was the root-shaped metal iron with reduced molten ferrous oxide,and the other one on the outer layer was the iron slag containing Al,Ca,Si,and other elements.