Effect of CaO on the ionic microstructure and properties in dephosphorization slag by molecular dynamics simulation

Abstract

The microstructure of dephosphorization slag determines its macroscopic properties. Dephosphorization process affects the dissolution of P2O5 in the slag and changes the dephosphorization conditions. In this paper, molecular dynamics simulation was used to study the effect of composition on the microstructure and macroscopic properties of CaO-P2O5 binary system, which have a significance effect on the dissolution mechanism of P2O5 in slag in the steelmaking field. The microstructure of the melt was described by radial distribution function, cluster proportion, bond angle distribution and so on. The diffusion coefficient, viscosity, thermal conductivity and surface tension were calculated to describe the macroscopic properties of the molten slags. The results show that the P-O bond length changes from 1.45 to 1.55 as the content of CaO increases from 50 % to 70 %. The planar [PO3]- anions gradually transform into tetrahedral [PO4]3- anions with increasing XCaO, and finally the [PO4]3- clusters occupy the majority. Ca exists as free cation and plays the role of charge complement in molten CaO-P2O5 melt. The order of diffusion ability of elements is O2– > Ca2+ > P5+ as XCaO increases from 50 % to 70 %. The viscosity of the system tends to decrease. The dilution of P-O clusters is enhanced with the increase of XCaO. The thermal conductivity and surface tension shows an upward trend.