Phosphate enrichment mechanism in CaO–SiO2–FeO–Fe2O3–P2O5 steelmaking slags with lower binary basicity

Abstract

The addition of silica to steelmaking slags to decrease the binary basicity can promote phosphate enrichment in quenched slag samples. In this study, we experimentally investigated phosphate enrichment behavior in CaO-SiO 2 -FeO-Fe 2 O 3 -P 2 O 5 slags with a P 2 O 5 content of 5.00% and the binary basicity B ranging from 1.0 to 2.0, where the (%Fe t O)/(%CaO) mass percentage ratio was maintained at 0.955. The experimental results are explained by the defined enrichment degree 2 3 C S C P R  of solid solution 2CaO·SiO 2 -3CaO·P 2 O 5 (C 2 S-C 3 P), where 2 3 C S C P R  is a component of the developed ion and molecule coexistence theory (IMCT)-N i model for calculating the mass action concentrations N i of structural units in the slags on the basis of the IMCT.The asymmetrically inverse V-shaped relation between phosphate enrichment and binary basicity B was observed to be correlated in the slags under applied two-stage cooling conditions. The maximum content of P 2 O 5 in the C 2 S-C 3 P solid solution reached approximately 30.0% when the binary basicity B was controlled at 1.3.

A Novel Process for Separation of Magnetite and Phosphorous Phases from a CaO–SiO₂–FeO–P₂O₅ Slag

“…The P 2 O 5 content in the phosphorus enriched phase was detected to be 34.1%, which is almost twice as high as previous studies. 17,18) Moreover, the dominant composition of the spinel phase was Fe 3 O 4 even through it was presented as Fe 2 O 3 in Table 3. Therefore, in the whole paper, Fe The products obtained in different stages were tested by XRF, the results were shown in Table 4.…”

“…However, solid solution 2CaO•SiO 2 -3CaO•P 2 O 5 (C 2 S-C 3 P) was the main phosphorus-enriched phase in steelmaking slag and the maximum content of P 2 O 5 in C 2 S-C 3 P was reported no more than 20%, particularly for the slag with basicity above 2.0. 17,18) Moreover, the abovementioned approaches primarily focused on extracting phosphorus from steelmaking slag, rather than simultaneously recycling iron and phosphorus as well as reusing tailings. Here, we present a successful method, based on the combination of magnetic separation and flotation methods, to selectively separate iron and phosphorus from CaO-SiO 2 -FeO-P 2 O 5 slag through atmospheric control and B 2 O 3 addition.…”

Ionic analysis of the effect of temperature on dephosphorization capacity of silicate slags

“…For the dephosphorization process, it is generally believed from a molecular point of view that CaO in the slag reacts with the dissolved [P] and [O] in liquid iron to form 3CaO•P 2 O 5 (C 3 P), which can form a solid solution (nC 2 S-C 3 P) with 2CaO•SiO 2 (C 2 S). The related investigations [28][29][30] corroborated that the phosphorus dissolved in the C 2 S solid phase is more stable in the form of C 3 P, which can be expressed as follows from the ionic point of view:…”

Influence of Temperature on Dephosphorization at Lower Basicity and Lower Temperature Based on Industrial Experiments and IMCT

“…In recent years, the ion molecule coexistence theory (IMCT) has been successfully applied to the thermodynamic calculation of dephosphorization process in converter. [22][23][24][25][26][27][28][29][30] Yang et al 23,24) established CaO-SiO 2 -MgO-MnO-FeO-Fe 2 O 3 -Al 2 O 3 -P 2 O 5 slag thermodynamic prediction models of phosphorus distribution ratio IMCT-L P and phosphorus capacity IMCT-C PO4 3−, respectively. The results showed that the IMCT thermodynamic model can not only accurately predict the phosphorus distribution ratio and phosphorus capacity of steelmaking slag, but also accurately predict the phosphorus distribution ratio and phosphorus capacity of each phosphorus containing component in slag, without introducing new fitting parameters.…”