七宝山铁尾矿还原焙烧—弱磁选回收铁试验

江西七宝山铁尾矿成分复杂,铁品位达38.74%,主要铁矿物为针铁矿。为了高效回收其中的铁,采用还原焙烧—弱磁选工艺进行了试验研究。结果表明:提高煤粉添加量、延长焙烧时间、提高焙烧温度均有利于提高还原焙烧产物中铁的金属化率和金属铁粉的指标;在煤粉添加量为15%,还原焙烧温度为1 250℃,还原焙烧时间为60min,焙烧产物磨至-325目占58.80%,弱磁选磁场强度为88 kA/m情况下,可获得铁品位为88.80%、铁回收率为92.28%的金属铁粉。还原焙烧产物的微观分析表明:在还原焙烧初期,焙烧产物中生成了大量微细粒铁颗粒,随着还原焙烧时间的延长,细小的铁颗粒不断兼并、集聚,60 min后铁颗粒不再明显集聚、长大;随着还原温度的提高,焙烧产物中的铁颗粒显著长大,在1 250℃情况下,铁颗粒长至100μm左右;长大的铁颗粒中包裹细小脉石颗粒是造成金属铁粉铁品位难以进一步大幅度提高的主要原因。

Iron Recovery from Qibaoshan Iron Ore Tailing by Reduction Roasting-Magnetic Separation Process

The mineral composition of Qibaoshan iron ore tailing with Fe grade of 38.74% is complicated,and the main iron mineral is goethite.The experiments were conducted for efficient utilization of iron in tailings,by adopting the process of reduction roasting-low intensity magnetic separation.The results showed that the metallization ratio and the grade of iron powder increased with the increasing of reduction temperature,reduction time and the addition of coal powder.The iron concentrate with total iron content of 88.80% at a recovery rate of 92.28% was obtained under conditions of the reduction temperature at 1 250 ℃,reduction time for 60 min,the addition of coal 15%,the grinding fineness of -325 mesh 58.80% and the magnetic field intensity 88 kA/m.The microscopic structure analysis of roasting product showed that with the reaction time extending,the fine iron particle,which is formed in initial period of the reduction reaction,would grow constantly.When reduction time was more than 60 min,the growth of iron particle was not obvious.With the enhancing of reduction temperature,the growth of iron particle was more obvious.The particle size of iron particle reached 100 μm when the reduction temperature was 1 250 ℃.The fine gangue,wrapped in the iron particle,was a main obstacle for the large increasing of iron concentrate grade.