关键词: 高炉炼铁, 氧气高炉, 含铁炉料, 低温还原粉化

Abstract: The oxygen blast furnace process is an important low-carbon ironmaking process, and the reduction degradation performance of the ferrous burden significantly impacts the smelting process. In order to guide the selection of ferrous burden under the oxygen blast furnace process, the reduction degradation behaviors of sinter and pellet under the two reduction atmospheres of oxygen blast furnace and traditional blast furnace were studied. The results showed that under traditional blast furnace condition, the sinter degradation index (RDI+3.15) tended to decrease and then increase with increasing reduction temperature. This was due to the fact that as the reduction continued, the internal expansion stress generated by the transformation of Fe2O3 to Fe3O4 gradually increased, leading to an increase in degradation. The degradation index at 700℃ was close to the national standard test value. In the high-temperature range (900℃ to 1100℃), the Fe3O4 at the core of the sinter was rapidly reduced. As FeO and metallic iron gradually formed within the burden particles, and as they moved from the surface to the interior, the volume appeared to shrink and densification increased, thereby weakening the degradation. However, under the oxygen blast furnace condition with high reduction potential, the degradation index of sinter exhibited a decreasing trend from 500℃ to 900℃. Furthermore, the increased concentration of CO and H2 in the reducing gas under oxygen blast furnace condition enhanced the diffusion of the gas into the core of the burden. This led to a gradual shift of the reaction interface from the surface to the core, resulting in more Fe2O3 being reduced to Fe3O4. Consequently, the reduction expansion stress increased, which in turn lowered the degradation index of sinter under the oxygen blast furnace condition compared to that under the traditional blast furnace condition. However, as the reduction index increased and the content of FeO and metallic iron in the sinter rose, the degradation performance of the sinter under oxygen blast furnace conditions at 1100℃ improved, slightly surpassing the degradation index under traditional blast furnace conditions at the same temperature. In addition, the degradation indices for both sinter and pellet under oxygen blast furnace condition were lower than those under the traditional blast furnace condition. A comparison of the two types of burden showed that the degradation index for pellet was higher than that for sinter under both conditions, and RDI+3.15 of the pellet was above 90% for all pellets.

Key words: blast furnace ironmaking, oxygen blast furnace, ferrous burden, low-temperature reduction degradation