Softening-melting properties of blast furnace charge with pre-dehydrated lump iron ore
PANG Zhuo-gang1, DING Wang2, YU Yuan-hao1, WANG Guang1, CHEN Yan-biao1, ZUO Hai-bin1
1. State Key Laboratory of Advanced Metallurgy, University of Science and Technology Beijing, Beijing 100083, China; 2. Ironmaking Plant, Hunan Valin Xiangtan Iron and Steel Co., Ltd., Xiangtan 411101, Hunan, China
Abstract：The addition of natural lump iron ore to blast furnace is of great significance to reduce carbon emissions in ironmaking process. Pre-dehydrate treatment was applied to C4 ore to improve the deterioration of gas permeability and softening-melting performance of furnace charge caused by the decrepitation of Australian C4 ore. The decrepitation and melting-dropping performance of natural and pre-dehydrated C4 ore were investigated, and the effect of pre-dehydrated C4 ore ratio (12%-24%) on the softening-melting performance of ferrous burden was also studied. The results showed that with the temperature increased from 600 ℃ to 900 ℃, the decrepitation index of natural C4 ore rapidly increased from 8.05% to 22.5%, while that of pre-dehydrated C4 ore only increased from 3.38% to 7.11%. The initial softening temperature (t10) and dripping temperature (td) of sintering ores were higher, but the melting zone was narrowest. And the sintering ores have better comprehensive dropping performance, followed by pellet ore and C4 ores. Compared with natural C4 ore, the initial softening temperature of pre-dehydrated C4 ore was increased by 82 ℃, and the melting initial temperature (ts) increased by 47 ℃. But the softening zone (t40-t10) and melting zone (td-ts) reduced by 26 ℃ and 50 ℃, respectively. Although the cohesive zone moved to the high temperature zone, the maximum differential pressure (ΔPm) of natural C4 ore and pre-dehydrated C4 ore and permeability index (S) were both high. Thus, the excessive addition of C4 ore was not conducive to smooth blast furnace operation. Compared with the burden structure of 76% sintering ore and 24% pellet ore, the softening zone of burden structure with C4 ore was narrower, while the melting zone was wider, and ΔPm and S values increased significantly. When the proportion of pre-dehydrated C4 ore in burden structure increased from 12% to 18%, the softening zone and melting zone narrowed and the cohesive zone shifted to the high temperature zone, which is due to the decrease of the slag mass percent and the easier occurrence of carburization. However, when the proportion of pre-dehydrated C4 ores exceeded 18%, the strength of the ferrous burden dramatically reduced, which led to the decrease in the initial softening temperature and initial melting temperature, and the maximum differential pressure of furnace increased. Based on the current raw material conditions, the suitable addition ratio of pre-dehydrated C4 ore is 18%. Using this burden structure to smelt 1 t hot metal in the blast furnace could reduce 53.82 kg CO2 emissions.
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2023, Vol. 58 
