残留CO2对石灰在转炉初渣中溶解的影响

 在转炉炼钢过程中,石灰快速溶解对转炉高效脱磷具有十分重要的意义,石灰溶解过程中熔渣/石灰界面处形成的2CaO·SiO₂产物层被认为是阻碍石灰溶解的关键因素。制备了具有两种不同CO₂含量的部分煅烧石灰石,采用浸泡法研究了部分煅烧石灰石在转炉初渣中的溶解行为,并与纯石灰、石灰石的溶解行为进行比较。结果表明,石灰石溶解时在液态熔渣中CaO的传质系数为石灰的2.1倍,残留CO₂质量分数为10%的部分煅烧石灰石的传质系数高达石灰石的6.7倍。在CO₂质量分数为0～43.5%时,石灰的溶解速率先增大后减小。石灰溶解过程中形成的2CaO·SiO₂层严重阻碍了FeO_x的扩散,从而减缓了石灰的溶解。与石灰不同,石灰石分解产生的CO₂能够破坏2CaO·SiO₂层并破坏自身结构,有利于熔渣的渗透,这也适用于残留CO₂的部分煅烧石灰石。制备纯石灰的过程中为了确保石灰芯部完全煅烧,因此极易导致石灰外表面发生过烧,而制备部分煅烧石灰石能在一定程度上解决表面过烧的问题。此外,与石灰石相比,部分煅烧石灰石由于表面是石灰外壳,溶解初期其表面附近的炉渣温降相对更低,能够避免溶解初期出现停滞阶段。在转炉富余热量有限的情况下,部分煅烧石灰石的石灰替换比高于石灰石,这取决于部分煅烧石灰石中的CO₂残留量。

Effect of residual CO2 on dissolution of lime in converter slag

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 FeO_x, 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.