A Thermodynamic Model of Phosphate Capacity for CaO-SiO2-MgO-FeO-Fe2O3-MnO-Al2O3-P2O5 Slags Equilibrated with Molten Steel during a Top–Bottom Combined Blown Converter Steelmaking Process Based on the Ion and Molecule Coexistence Theory

Abstract

slags at the steelmaking endpoint during an 80-ton top-bottom combined blown converter steelmaking process has been developed based on the ion and molecule coexistence theory (IMCT). The phosphate capacity has a close relationship with the phosphate capacity index, whereas the logarithm of phosphate capacity is 12.724 greater than that of phosphate capacity index at 1873 K (1600°C). The developed phosphate capacity prediction model can be also used to predict the phosphate capacity index with reliable accuracy compared with the measured and the predicted phosphate capacity index of the slags by other models in literatures. The results from the IMCT phosphate capacity prediction model show that the comprehensive effects of iron oxides and basic components control the dephosphorization reaction with an optimal ratio of (pct FeO)/(pct Fe 2 O 3 ) as 0.62. The determined contribution ratio of Fe t O, CaO + Fe t O, MgO + Fe t O, and MnO + Fe t O to the phosphate capacity or phosphate capacity index of the slags is approximately 0.0 pct, 99.996 pct, 0.0 pct, and 0.0 pct, respectively. The generated 2CaOAEP 2 O 5 , 3CaOAEP 2 O 5 , and 4CaOAEP 2 O 5 as products of dephosphorization reactions accounts for 0.016 pct, 96.01 pct, and 3.97 pct of the phosphate capacity or phosphate capacity index of the slags, respectively.

Critical Evaluation of Prediction Models for Phosphorus Partition between CaO-based Slags and Iron-based Melts during Dephosphorization Processes

“…As thermodynamic models, the collected 16 models of k P or L P were established under the condition of the slag-metal equilibrium over various temperature ranges. Only several models among the collected 16 models of k P or L P , rather than the entire 16 models, had primarily been evaluated by Yang et al [81][82][83] based on the experimental data of L P for molten steel dephosphorization by the CaO-based slags. In this contribution, the collected 16 models of k P or L P from the literature [2,3,10,13,19,20,21,23,26,33,37,40,55,57,65,67,69,70,74] have critically been evaluated based on the measured [84] results of hot metal dephosphorization at a commercial-scale hot metal pretreatment station as well as the recently proposed dephosphorization mechanism [84] of hot metal by CaO slags.…”

“…Finally, a general method for developing the prediction model of k P or L P with ideal accuracy from the reported models has been suggested or provided through revising the collected models for the assigned slags equilibrated with molten steel or hot metals. In addition, the developed L P model [84] based on the ion and molecule coexistence theory (IMCT) [81][82][83][84][85][86][87][88][89][90][91][92][93][94] for slags, i.e., the IMCT-L P model, [84] for hot metal dephosphorization by CaObased slags has also been assessed through comparison with the predicted results by the revised models from the literature.…”

“…Thus, accurate conversion among various expressions of phosphorus concentration in slags is important. According to the atomic mass M P of P and molecular mass M P 2 O 5 of P 2 O 5 or M PO 3À 4 of PO 3À 4 , some formulas can be correlated to transfer various expressions of phosphorus content in slags as [39,42,58,62,63,71,78,82,83] ðpct…”

“…For instance, many researchers such as Schu¨rmann and Fischer, [55] Ide and Fruehan, [69] and Basu et al [75] briefly reviewed or critically evaluated the related literature on prediction models of L P between steelmaking slags and molten steel prior to 1991, 2000, and 2007, respectively. In addition, Yang et al [81][82][83] also tabulated and assessed some models of L P between steelmaking slags and molten steel. However, the detailed literature survey on prediction models of L P between various slags and molten steel or hot metal was not carried out by researchers.…”

Effects of CaO on Reduction of Copper Slag by Biomass Based on Ion and Molecule Coexistence Theory and Thermogravimetric Experiments

“…After the follow-up studies, IMCT has been successfully applied to the calculation of mass action concentrations, distribution of nonmetallic inclusions and oxidizing capability in different kinds of slag systems. [13][14][15][16] Copper slag, as a raw material of iron resource, is mainly in the form of fayalite (2FeO·SiO 2 ) and magnetite (Fe 3 O 4 ). In molten slag system, ferric iron and ferrous iron are in the components of FeO and Fe 2 O 3 .…”