Luo Guanwen, Peng Zhiwei, Gao Kangle, Fan Wanlong, Tian Ran, Yi Lingyun, Rao Mingjun
School of Minerals Processing and Bioengineering, Central South University, Changsha 410083, China.
Materials (Basel). 2024 Sep 3;17(17):4362. doi: 10.3390/ma17174362.
To utilize the sensible heat of hot roasted iron ore pellets with no CO emission in the production of metallized pellets for direct steelmaking, the pellets were reduced in H during their cooling process with variable cooling rates. When the cooling rate decreased from 5.2 °C/min to 2.0 °C/min, the total iron content, reduction degree, and iron metallization degree of the pellets increased continuously from 74.0 wt%, 52%, and 31.1% to 84.9 wt%, 93.4%, and 89.2%, respectively. However, the compressive strength of the pellets increased initially from 2100 N/p to 2436 N/p and then decreased considerably to 841 N/p. As the cooling rate decreased, more FeO was reduced to Fe with diminishing FeO and FeSiO. The porosity of the pellets increased from 23.9% to 54.3%, with higher distribution uniformity of pores. The morphology of metallic iron particles also transited from a layered form to a spherical form and lastly to a porous reticular form. Meanwhile, the metallic iron particles in the pellets grew evidently with more uniform distributions. When the cooling rate was 3.7 °C/min, the resulting metallized pellets had the reduction degree of 74.2%, iron metallization degree of 66.9%, and the highest compressive strength of 2436 N/p, in association with the spherical morphology and relatively large size of metallic iron particles.
为了在直接炼钢用金属化球团的生产中利用热焙烧铁矿石球团的显热且无一氧化碳排放，在冷却过程中以可变冷却速率用氢气对球团进行还原。当冷却速率从5.2℃/min降至2.0℃/min时，球团的总铁含量、还原度和铁金属化度分别从74.0 wt%、52%和31.1%持续增加到84.9 wt%、93.4%和89.2%。然而，球团的抗压强度最初从2100 N/p增加到2436 N/p，然后大幅下降至841 N/p。随着冷却速率降低，更多的FeO被还原为Fe，同时FeO和FeSiO减少。球团的孔隙率从23.9%增加到54.3%，孔隙分布均匀性更高。金属铁颗粒的形态也从层状转变为球状，最后转变为多孔网状。同时，球团中的金属铁颗粒明显长大，分布更加均匀。当冷却速率为3.7℃/min时，所得金属化球团的还原度为74.2%，铁金属化度为66.9%，抗压强度最高可达2436 N/p，且金属铁颗粒呈球状形态且尺寸相对较大。
