钠盐强化某低品位铁矿含碳球团还原机理

Reduction enhancement mechanisms of low iron grade ore-coal composite pellets by sodium salt

采用内配煤造球还原焙烧的方法对某高硅低品位铁矿进行处理,并加入钠盐强化还原,研究温度、时间和添加剂质量分数对还原的影响,并采用烟气分析仪研究含钠盐对还原过程的影响。计算CO体积分数对FeO还原和铁橄榄石(Fe_2SiO_4)生成反应的热力学影响,并采用SEM和XRD等分析还原球团的微观结构和成分。研究结果表明:还原中间产物FeO可与Si O2反应生成难以再还原的铁橄榄石(Fe_2SiO_4);提高还原反应体系中CO的体积分数可以促进FeO的还原和减少铁橄榄石(Fe_2SiO_4)的生成;钠盐能够有效地促进球团中碳的气化反应,提高球团内CO的体积分数,从而促进FeO的还原,减少Fe_2SiO_4的生成,进而改善还原效果;当内配煤质量分数(即C与Fe质量比m(C)/m(Fe))为0.4,钠盐质量分数为3%,焙烧时间为30 min以及焙烧温度为950℃时,还原效果最佳,还原球团的金属化率为56.74%,磨矿、磁选后精矿铁品位和铁回收率分别为74.16%和74.57%。

Method of reduction roasting with iron ore-coal composite pellets was adopted to deal with high silicon content-low iron grade ore,and sodium salt was used to enhance the reduction process.Effects of temperature,reduction time and mass fraction of sodium salt on reduction behavior were researched.Gas analysis was used to investigate effect of sodium salt on the reduction process.Effects of CO volume fraction on thermodynamic of reduction of FeO and formation of fayalite were analyzed,and SEM and XRD were applied to analyse microstructures and composition of reduced pellets.The results show that FeO may react with SiO2 and form fayalite which can hardly be reduced again.Increasing CO volume fraction can improve the reduction of FeO,and thus decrease the formation of fayalite.Reduction of iron oxide can be facilitated effectively by sodium salt,which can be attributed to the fact that sodium improves the gasification reaction of carbon and increases CO volume fraction,which promotes the reduction of FeO.Reduced pellets with metallization ratio of 56.74%can be obtained with ratio of m(C)/m(Fe)0.4,mass fraction of sodium salt 3%and reduces at 950℃for 30 min.TFe in the magnetic separation concentrate and iron recovery are 74.16%and 74.57%,respectively.