Effect of residual CO2 on dissolution of lime in converter slag
TIAN Yu-feng1, LI Guang-qiang1,2,3, XIAO Yong-li4, LIU Yu1,2
1. State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology, Wuhan 430081, Hubei, China; 2. Key Laboratory for Ferrous Metallurgy and Resources Utilization of Ministry of Education, Wuhan University of Science and Technology, Wuhan 430081, Hubei, China; 3. Hubei Provincial Key Laboratory for New Processes of Ironmaking and Steelmaking, Wuhan University of Science and Technology, Wuhan 430081, China; 4. Central Research Institute, China Baowu Group, Shanghai 201900, China
Abstract：In the process of converter steelmaking, the rapid dissolution of lime is of great significance for efficient dephosphorization of converter. The calcium silicate product layer formed at the slag/lime interface in the process of lime dissolution is considered to be the key factor hindering lime dissolution. Two kinds of partially calcined limestone with different CO2 content were prepared. The dissolution behavior of partially calcined limestone in the primary slag of converter was studied by immersion method, and compared with that of pure lime and limestone. The results show that the mass transfer coefficient of CaO in the liquid slag during the dissolution of limestone is 2.1 times that of lime, and the mass transfer coefficient of partially calcined limestone with 10% residual CO2 is as high as 6.7 times that of limestone. When the mass fraction of CO2 is in the range of 0-43.5%, the dissolution rate of lime firstly increases and then decreases. The 2CaO·SiO2 layer formed in the process of lime dissolution seriously hinders the diffusion of FeOx, so it slows down the dissolution rate of lime. Significantly different from lime, CO2 produced by limestone decomposition can destroy the 2CaO·SiO2 layer and internal structure, which is conducive to the penetration of slag. This is also applicable to partially calcined limestone with residual CO2. In the process of preparing pure lime, in order to ensure the complete calcination of the lime core, it is very easy to cause over-burning on the outer surface of lime, and the preparation of partially calcined limestone can solve the problem of over-burning on the surface. Furthermore, compared with limestone, the temperature drop of slag near the surface of partially calcined limestone is relatively lower because the surface is lime shell, which can avoid the stagnation stage at the initial stage of dissolution. When the surplus heat of converter is limited, the lime replacement ratio of partially calcined limestone is higher than that of limestone, which depends on the CO2 residue in partially calcined limestone.
田雨丰, 李光强, 肖永力, 刘昱. 残留CO2对石灰在转炉初渣中溶解的影响[J]. 钢铁, 2022, 57(10): 84-90.
TIAN Yu-feng, LI Guang-qiang, XIAO Yong-li, LIU Yu. Effect of residual CO2 on dissolution of lime in converter slag[J]. Iron and Steel, 2022, 57(10): 84-90.
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2022, Vol. 57 
