Comprehensive effect of Al2O3 content and binary basicity on the enrichment mechanism of phosphates in quenched steelmaking slags

Abstract

A comprehensive effect of Al2O3 content and binary basicity B on the enrichment behavior of phosphates in rapidly quenched CaO-SiO2-FeO-P2O5-Fe2O3-Al2O3 steelmaking slags was investigated through thermodynamic calculations and experimental determination. It is found that the determined mass percentage of P2O5 in the phosphate-enriched phase nC2S-C3P depends on the forming of free C2S in the steelmaking slags and increasing the SiO2 content can result in an obviously decreasing tendency of formed C2S. Adding Al2O3 as a dilute agent for decreasing the viscosity and melting point of the steelmaking slags can be easily bonded with free C2S to form a gehlenite(C2AS) solid solution. Thus,adding Al2O3 in the steelmaking slags can decrease the amount of free C2S in the steelmaking slags,which affects phosphate enrichment. In order to obtain a greater phosphate enrichment in the steelmaking slags,a coupling relationship between the binary basicity B and the mass percentage of Al2O3 in the initial steelmaking slags should be kept as(% Al2O3)=-27.70 + 21.62 B under the conditions of(Al2O3) 〈20.0% and the binary basicity B〉1.3.

Keywords

• steelmaking slags
• alumina
• basicity
• phosphates
• enrichment