Thermodynamic simulation analysis for carbothermal reduction of converter steel slag
To study the changes in phase types and contents of equilibrium products during the carbothermal reduc-tion of converter slag,based on the variables of reduction temperature,alkalinity,and carbon ratio(coke-to-slag ra-tio),FactSage 7.1 thermodynamic software was used for calculation and analysis.The study reveals under a certain coke-slag ratio,with the increase of reduction temperature,the residual C content in the equilibrium phase composi-tion shows decreasing trend,while the Fe3C and P2 gas content show increasing trend,indicating that the high tem-perature is favorable to the reduction of iron oxides and apatite,especially to the gasification of dephosphorization.With reduction temperature increasing,the contents of Fe3P/Fe2P in the equilibrium phase composition decrease,while the contents of Mn2P and P2(g)increase.This indicates that the reduction temperature has significant influ-ence on the stability sequence of phosphorus-containing phases,with the stability enhancement order as Fe3P→Fe2 P→Mn2 P→P2(g).High temperature favors the gasification and removal of phosphorus.Under constant coke-to-slag ratio and reduction temperature,the increase in the alkalinity of charge leads to elevation of Fe3C content in the equilibrium phase composition,indicating that higher alkalinity promotes the reduction of iron oxides.As the al-kalinity of the mixture increase,the silicate liquid phase content in the equilibrium phase composition shows decrea-sing trend,and the alkalinity of 1.8 generates the largest amount of liquid phase.The alkalinity of the mixture in the range of 1.8 to 2.2 is conducive to the generation of α-C2S and self-pulverization of the product,and the content of α-C2S is largest when the alkalinity is 2.0.Changes in the coke-to-slag ratio have minimal impact on the phase types and contents of equilibrium products during carbothermal reduction of converter slag.Thermodynamic calcula-tions indicates that the temperature range favorable for steel slag pulverization is 1 450-1 500 ℃,the alkalinity range is 1.8-2.2,and the coke-slag ratio range is 10:90-15∶85.This range of conditions facilitates the generation of α-C2S and the best pulverization of steel slag.
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