转炉钢渣碳热还原的热力学模拟分析

Thermodynamic simulation analysis for carbothermal reduction of converter steel slag

为研究转炉钢渣碳热还原平衡产物的物相种类和含量随还原温度、碱度及配碳量(即焦渣比)的变化规律,使用FactSage7.1热力学软件计算并进行分析。研究表明,在焦渣比一定的情况下,随着还原温度的升高,平衡物相组成中残C含量呈现下降趋势,Fe_(3)C和P_(2)气体含量则呈现升高趋势,表明高温有利于铁氧化物和磷灰石的还原,特别是有利于气化脱磷;随着还原温度的升高,平衡物相组成中Fe_(3)P/Fe_(2)P含量减少,Mn_(2)P和P_(2)(g)含量增多,表明还原温度对含磷物相的稳定顺序有较大影响,温度升高其稳定性增强的顺序为Fe_(3)P→Fe_(2)P→Mn_(2)P→P_(2)(g),高温有利于气化脱磷。在焦渣比和还原温度一定时,随着混合料碱度的升高,平衡物相组成中Fe_(3)C含量均呈现升高趋势,表明提高碱度有利于铁氧化物的还原;随着混合料碱度的升高,平衡物相组成中硅酸盐液相含量呈现降低趋势,碱度为1.8时所生成的液相量最多;混合料碱度在1.8到2.2之间时,有利于α-C_(2)S的生成及产物的自粉化,碱度为2.0时α-C_(2)S含量最多。焦渣比的变化对转炉钢渣碳热还原平衡产物的物相种类和含量影响不大。热力学计算表明,利于钢渣微粉化的温度范围为1450~1500℃,碱度范围为1.8~2.2,焦渣比范围为10∶90~15∶85,该条件范围利于α-C_(2)S的生成且钢渣粉化效果最好。

To study the changes in phase types and contents of equilibrium products during the carbothermal reduction of converter slag,based on the variables of reduction temperature,alkalinity,and carbon ratio(coke-to-slag ratio),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 composition shows decreasing trend,while the Fe_(3)C and P_(2)gas content show increasing trend,indicating that the high temperature is favorable to the reduction of iron oxides and apatite,especially to the gasification of dephosphorization.With reduction temperature increasing,the contents of Fe_(3)P/Fe_(2)P in the equilibrium phase composition decrease,while the contents of Mn_(2)P and P_(2)(g)increase.This indicates that the reduction temperature has significant influence on the stability sequence of phosphorus-containing phases,with the stability enhancement order as Fe_(3)P→Fe_(2)P→Mn_(2)P→P_(2)(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 Fe_(3)C content in the equilibrium phase composition,indicating that higher alkalinity promotes the reduction of iron oxides.As the alkalinity of the mixture increase,the silicate liquid phase content in the equilibrium phase composition shows decreasing 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 ofα-C_(2)S and self-pulverization of the product,and the content ofα-C_(2)S 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 calculations indicates that the temperature range favorable for steel slag pulverization is 1450-1500℃,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 ofα-C_(2)S and the best pulverization of steel slag.