某高品位磁铁精矿球团预热—煤基直接还原研究

Study on Pellet Preheating and Direct Coal Reduction of High Grade Magnetite Concentrate

为了了解高品位铁精矿球团的预热及煤基直接还原特性,以某高品位磁铁精矿为原料,对添加有机添加剂的球团进行了预热及直接还原工艺条件研究,并对确定条件下的DRI球团进行了性能表征。结果表明:①预热球团的抗压强度随预热时间的延长和预热温度的升高而增大,要获得抗压强度为1 000 N/个的预热球团,1 100℃下需预热14 min。②1 100℃预热14 min的抗压强度为1 000 N/个的预热球团在C、Fe质量比为1.5,温度为1 100℃,时间120 min的条件下进行还原,可获得铁品位为94.12%、金属化率为98.64%的DRI球团。③DRI球团中仅呈现金属铁的衍射峰,中心金属铁互连紧密,金属键桥发育充分,铁晶粒粗大,球团边缘更明显,该有害元素含量极低的特极DRI是冶炼特殊钢、制备粉末冶金铁粉及高纯铁的优质原料。④预热球团具有足够的抗压强度不仅是回转窑安全运行的重要保证,而且对直接还原速率有明显影响,适宜采用1 100℃预热14 min抗压强度为1 000 N/个左右的预热球团。

In order to understand the preheating and coal-based direct reduction characteristics of high-grade iron concentrate pellets,the preheating and direct reduction process conditions of pellets with organic additives were studied using a high-grade magnetite concentrate as raw material,and the performance of DRI pellets under the determined conditions was characterized. The results show that:①The compressive strength of preheated pellets increases with the prolongation of preheating time and the increase of preheating temperature. To obtain preheated pellets with compressive strength of 1 000 N/P,it takes 14 min to preheat at 1 100 ℃.②DRI pellets with iron grade of 94.12% and metallization rate of 98.64% can be obtained by reduction of preheated pellets with compressive strength of 1 000 N/P at 1 100 ℃ for 14 min,mass ratio of C to Fe of 1.5,temperature of 1 100 ℃ and time of 120 min.③DRI pellets only show the diffraction peaks of ferrous metal,the central metal iron is closely interconnected,the metal bond bridges are well developed,the iron grains are coarse,and the edges of the pellets are more obvious. The extremely low content of harmful elements in DRI pellets is a high quality raw material for smelting special steel,preparing powder metallurgical iron powder and high purity iron.④The sufficient compressive strength of preheated pellets is not only an important guarantee for the safe operation of rotary kiln,but also has a significant impact on the direct reduction rate. It is suitable to preheat pellets with compressive strength of about 1 000 N/P at 1 100 ℃ for 14 min.