双层结构对提高含碳球团强度的影响

Effect of double layer structure on the strength of iron ore pellets containing carbon

为了提高含碳球团强度,提出了内层为含碳球团,外层为精矿粉的双层结构复合含碳球团新工艺。研究了不同外层厚度球团的强度和金属化率,分析了球团强度形成的机理。研究结果表明:外层厚度适中的复合含碳球团强度能得到有效提高。该复合球团生球落下强度为普通含碳球团的2倍,400℃预热球抗压强度可达147.6N/个。900℃后,随着温度的增加,球团抗压强度提高,1 150℃恒温还原30min后抗压强度为2 080N/个。且研究发现复合含碳球团能有效提高碳素利用率,C/O物质的量之比nC/nO为2∶3的复合球团还原后金属化率可达93.90%,其中外层金属化率为92.46%。通过显微结构分析,发现球团还原后外层生成了致密的金属铁外壳,这种外壳的独特力学性能是球团强度提高的主要原因。

In order to improve the strength of iron ore pellets containing carbon（IOPC）, proposed a new double lay- er structure which wraps a iron ore layer outside the IOPC. The strength and metallization rate of different thick- ness outer layer were tested. And the formation mechanism of strength was analyzed. The results show that the strength o{ moderate outer layer of composite carbon-containing pellets can be improved effectively. The drop strength of this new pellet is 2 times larger than that of ordinary IOPC. The compressive strength with 400 ＊C pre- heat is 147.6 N per pellet. The compressive strength decreases with increasing temperature while the temperature is above 900 ℃. After 1 150 ℃ constant temperature reduction for 30 min, the compressive strength can reach 2080 N. And it was found that the new pellet can effectively improve the utilization rate of C, the metallization rate of pellet （nc/no =2 ： 3） after reduction is 93.90%, and the metallization rate of outer layer is 92.46%. By micro- structure analysis, it was found that the outer layer of pellets generated dense metallic iron shell after reduction. This special mechanical property of the shell is the main reason for the increased strength.