焙烧温度对氧化球团性质及其气基直接还原过程的影响

考查焙烧温度对氧化球团抗压强度、孔隙率、Fe3O4含量及显微结构等性质的影响,研究不同焙烧温度下球团的还原行为,计算其还原过程动力学并确定还原过程的限制性环节。研究结果表明:随着焙烧温度的升高,氧化球团抗压强度增大,晶粒间互联及渣相增多,球团内Fe3O4含量及孔隙率则明显降低;在1 200℃焙烧时球团还原最快,其次为1 150℃和1 250℃,最慢的是于1 100℃焙烧球团;在1 100,1 150和1 200℃焙烧球团还原过程受界面化学反应控制,而1 250℃焙烧球团在还原过程前期受界面化学反应控制,后期受内扩散控制。

Effects of roast temperature on properties of oxide pellets and its gas-based direct reduction

Effects of roast temperature on the properties of oxide pellets,such as compressive strength,porosity,Fe3O4 content and microstructure,were studied.And the effects of roast temperature on the gas-based direct reduction course were also researched.The results show that compressive strength of the pellets increases with the increase of roast temperature,however,the porosity and Fe3O4 content decrease obviously.The reduction rate of pellets roasted at 1 200 ℃ is faster,than that roasted at 1 150 ℃ and 1 250 ℃,and the reduction rate of pellets roasted at 1 100 ℃ is the slowest of all samples.From the kinetics analysis,the whole reduction processes of pellets roasted at 1 100,1 150 and 1 200 ℃ are controlled by interfacial chemical reaction mechanism.But for the pellets roasted at 1 250 ℃,the prophase and anaphase are determined by interfacial chemical reaction mechanism and gaseous diffusion mechanism,respectively.