2种氧分压下铁矿粉烧结高温熔体的流动行为

Flow behavior of high-temperature melt during iron ore sintering under two oxygen partial pressures

铁矿粉烧结高温熔体的流动行为,对烧结矿强度的改善有重要影响,而其受到烧结料层内氧分压的深刻影响。以7种铁矿粉为研究对象,在实验测定2种氧分压下高温熔体流动行为的基础上,通过FactSage热力学计算、XRD矿相分析法及矿相数点法探究其影响机制。结果表明,当高温保持段的氧分压从0.1 kPa升高至21.0 kPa,高温下生成液相比例升高,熔体黏度降低,从而使得高温熔体流动行为指数增大。高温熔体中包含高温液相和少量未熔固相。高温液相的存在形式为CaO-Fe_(2)O_(3)系和CaO-Fe_(2)O_(3)-SiO_(2)系,前者的黏度远低于后者,在液相总量中的占比高于后者。较高氧分压和脉石成分含量促使CaO-Fe_(2)O_(3)-SiO_(2)系液相生成。冷却后的黏结相主要包括赤铁矿、磁铁矿、铁酸钙和硅酸盐等矿物。当氧分压升高时,黏结相中生成的难熔磁铁矿向赤铁矿转化,低熔点的铁酸钙系矿物含量升高,从而促进了高温熔体流动。

The flow behavior of high-temperature melt during the iron ore sintering has an important influence on the improvement of the sinter strength.The flow behavior of high-temperature melt is deeply affected by the oxygen partial pressure in the sintering bed.Taking seven kinds of iron ore powders as the research object,the flow behavior of high-temperature melt under two kinds of oxygen partial pressures was determined.The influence mechanism was explored through the thermodynamic calculation of FactSage,the mineral phase analysis of XRD and counting point method.The results show that when the oxygen partial pressure increases from 0.1 kPa to 21.0 kPa,the proportion of liquid phase increases,and the viscosity of melt decreases,which increases the flow behavior index of high-temperature melt.High-temperature melt contains high-temperature liquid phase and a small amount of un-melted solid phase.The existence forms of high-temperature liquid phase are CaO-Fe_(2)O_(3) system and CaO-Fe_(2)O_(3)-SiO_(2) system.The viscosity of the former is much lower than that of the latter,and the proportion of CaO-Fe_(2)O_(3) system in the total liquid phase is higher than that of the latter.Higher oxygen partial pressure and higher gangue content promote the formation of CaO-Fe_(2)O_(3)-SiO_(2) system liquid phase.After cooling,the bonding phases mainly include hematite,magnetite,calcium ferrite and silicate.With increasing of the oxygen partial pressure,insoluble magnetite is transformed into hematite,and the content of low-melting-point calcium ferrite minerals increases,which promotes the flow of high-temperature melt.