钠盐对高铝褐铁矿还原焙烧铝铁分离的影响

Effects of sodium-salt on Al-Fe separation by reduction roasting for high-aluminum content limonite

研究钠盐对高铝褐铁矿还原焙烧过程中铝铁分离的影响。结果表明:高铝褐铁矿经还原后,铁的金属化率为87.13%,焙烧产物经磨矿磁选后,金属铁粉中铁品位和Al2O3含量分别为68.07%(质量分数)和7.94%,铁的回收率仅为19.77%;添加硫酸钠14%(质量分数)、辅助添加剂BS2.5%(质量分数)后还原高铝褐铁矿,铁的金属化率可达95.69%,焙烧产物经磨矿磁选后,金属铁粉中铁品位升高到91.3%,Al2O3含量降低为1.27%,铁的回收率达到93.64%。XRD、EDX及微观结构研究表明:未添加钠盐时,高铝褐铁矿中铁氧化物易被还原为无磁性的γ-Fe,且铁与铝、硅结合紧密,磁选分离难度大;添加的钠盐能与Al2O3和SiO2反应生成铝硅酸钠,破坏矿石结构,有利于改善高铝褐铁矿的还原效果,但在碳酸钠作用下铁晶粒较小且易与脉石矿物结合,而在硫酸钠作用下金属铁颗粒长大,与脉石矿物解离性能好,有利于铝铁分离。

The effects of different sodium salts on Al-Fe separation in limonite were studied during reduction roasting process.The results show that when the ore is reduced directly,the metallization rate of iron in roasted ore is 87.13%,and the total iron grade and Al2O3 content of metallic iron concentrate is 68.07%and 7.94%,respectively,but the iron recovery rate is only 19.77%when the roasted products are treated by magnetic-separation.The metallization rate of Fe in the roasted ore is up to 95.69%when reducing with addition of 14%（mass fraction） Na2SO4 and 2.5%BS.The total iron grade of metallic iron product increases to 91.3%,and the Al2O3 content decreases to 1.27%,the iron recovery rate reaches 93.64%when the roasted products are treated by magnetic-separation.The XRD,EDX and microstructure results indicate that,when limonite is reduced without sodium salts,the iron oxides are reduced to nonmagneticγ-Fe,and most of the iron granules combine with aluminum and silicon gangues closely,which results in difficulties during magnetic separation.The sodium salts react with gangues bearing Al2O3 and SiO2 and form sodium aluminosilicates,thus,the structure of the ore is destroyed,and the reduction effect is greatly enhanced.However,the sizes of metallic iron grains obtained during the reduction with addition of sodium carbonate are relatively small and combined with gangue tightly. When reduced with sodium sulplate,the metallic iron grains grow and can be easily liberated from gangue.Therefore,Al-Fe separation is more effective after adding sodium sulphate.