Comparison of desulfurization mechanism in liquid CaO-SiO2 and MnO-SiO2: An ab initio molecular dynamics simulation

•AIMD method is used to calculate structure and charge information of the liquid slag.•The stable state and environmental information of sulfur in liquid silicate is obtained.•The desulfurization mechanism of the two systems was elucidated based on charge analysis. [Display omitted] In present study, systematic investigations of the CaO-SiO2 and MnO-SiO2 slag were performed of the evolution of the structure, and the sulfur dissolution mechanism at a temperature of 2000 K using ab initio molecular dynamics simulations. The results show that the structure and charge of CaO-SiO2 and MnO-SiO2 are very different. Firstly, Si-O has a strong polar bond while Ca-O and Mn-O show ionicity, and Mn-O has weaker ionicity than Ca-O. A small amount of Mn-Mn clusters are found in liquid MnO-SiO2. Secondly, charge distribution depicts that there is less charge around Ca, while there are relatively more charges around Mn. Bader charge analysis indicates that Mn and O have a broad valence distribution in MnO-SiO2 compared with CaO-SiO2. Thirdly, Sulfur prefers to form stable bonds with Mn atoms (Mn-S-Mn), whereas Si-S bonds are unstable and cannot be found in S-doped MnO-SiO2 silicate. However, in the CaO-SiO2 system, the S atom does not undergo rapid bond transitions. The study of the desulfurization mechanism shows that the uneven distribution of charge in MnO-SiO2 system will affect the transformation of oxygen types, resulting in the decrease of bridged oxygen and the increase of non-bridged oxygen. However, there is no charge effect in CaO-SiO2 system, and the non-bridged oxygen will be consumed in the desulfurization process, resulting in the decrease of non-bridged oxygen and the increase of bridged oxygen. This mechanism well explains the experimental results from a more microscopic perspective, which is of great significance to the research on the removal mechanism of S in the metallurgical industry.