Abstract: Lime is one of the slag making materials in the steelmaking process. Its rapid and sufficient dissolution can accelerate the dephosphorization and desulfurization reaction rates. The dissolution process of lime in CaO-Al2O3-SiO2(-MgO) slag system at 1550℃ was studied using the single hot thermocouple technique (SHTT). The results showed that when lime dissolved in CaO-Al2O3-SiO2 slag without MgO, its apparent radius ratio gradually decreased with increasing dissolution time, and the dissolution rate remained relatively stable throughout the entire dissolution process, with the shortest dissolution time among all systems. When lime dissolved in CaO-Al2O3-SiO2 slag containing MgO, the dissolution time increased gradually with increasing MgO content. According to the change in dissolution rate, the dissolution process could be divided into three stages. In the first and third stages, the lime dissolved quickly. However, in the second stage, the formation of MgAl2O4 solid phase product layer hindered the dissolution of lime. The analysis of lime dissolution kinetics showed that in CaO-Al2O3-SiO2 slag without MgO, the dissolution was controlled by boundary layer diffusion as the limiting step. In contrast, in CaO-Al2O3-SiO2 slag with MgO, the dissolution limiting step varied with both dissolution time and MgO content. Specifically, for Slag 2 (3wt% MgO) and Slag 3 (6wt% MgO), the dissolution limiting step was controlled by interfacial chemical reactions in the early stage, but shifted to boundary layer diffusion control in the middle and late stages. For Slag 4 (9wt% MgO), the limiting step was interfacial chemical reaction only in the initial part of the first stage, with product layer diffusion becoming the controlling factor thereafter.

Key words: lime, dissolution, slag, single hot thermocouple technique

摘要： 本工作采用单丝热电偶技术，系统研究了1550℃下石灰在CaO-Al2O3-SiO2(-MgO)渣中的溶解行为。研究结果表明，在不含MgO的CaO-Al2O3-SiO2渣中溶解时，石灰的表观半径比随溶解时间的延长呈持续减小趋势，且在整个溶解过程中，溶解速率变化较小，完全溶解时间最短；而在含MgO的CaO-Al2O3-SiO2渣中溶解时，石灰的溶解时间随着MgO含量增加逐渐延长，其溶解过程可按溶解速率变化分为三个阶段：第一阶段与第三阶段溶解速率较快，第二阶段由于MgAl2O4固相产物层的形成对溶解产生阻碍，因此导致溶解速率减缓。动力学分析进一步揭示，石灰在不含MgO的CaO-Al2O3-SiO2渣中溶解时，其溶解限制性环节为边界层扩散，而在含MgO的CaO-Al2O3-SiO2渣中溶解时，其溶解限制性环节随溶解时间和MgO含量变化而变化。

关键词: 石灰, 溶解, 炉渣, 单丝热电偶技术