褐铁矿微波还原焙烧-磁选单因素实验研究

针对褐铁矿铁品位难提高的问题, 采用“微波还原焙烧-磁选”工艺, 将褐铁矿还原成磁铁矿, 弱磁选后获得高品位磁铁精矿。采用SEM和XRD检测方法, 研究了褐铁矿微波焙烧过程中的矿相演变规律, 同时采用单因素实验方法, 重点考察了保温时间、焙烧温度、配碳量以及磁选电流和磨矿细度对焙烧矿磁选结果的影响。结果表明:随着温度升高, 褐铁矿逐渐还原为磁铁矿, 加热到570~650 ℃时, 生成大量磁铁矿, 750 ℃下焙烧矿烧结严重, 并产生大量弱磁性的硅酸亚铁, 不利于后续磁选。单因素实验结果及分析表明, 褐铁矿微波还原焙烧-磁选最佳工艺条件为:保温时间7.5 min, 焙烧温度650 ℃, 配碳量1.40%, 磁选电流0.6 A, 磨矿细度-0.044 mm。最终获得的铁精矿品位、回收率及产率分别为61.33%、75.11%和40.17%, 达到了炼铁生产入炉要求。

Single-factor Test for Reduction Roasting-Magnetic Separation of Limonite by Microwave Heating

In view of the difficulty in upgrading iron grade of limonite, the technique of reduction roasting-magnetic separation by microwave heating was proposed to make limonite firstly reduced into magnetite, which was subjected to low-intensity magnetic separation, resulting in the high-grade magnetite concentrate. The mineral phase variation during the process of reduction roasting of limonite by microwave heating was investigated by SEM and XRD analysis. And the effects of heat holding time, roasting temperature, carbon content, magnetic current and grinding fineness on the results of magnetic separation were investigated through single-factor test. Results showed that limonite was gradually reduced into magnetite with the rising temperature, and a large amount of magnetite were produced at the temperature ranges of 570~650 ℃. However, serious sintering of roasted ore would be occurred at 750 ℃, resulting in the generation of ferrous silicate with weak magnetism, being unfavorable for the following magnetic separation. The single-factor test results showed that    the process of reduction roasting-magnetic separation of limonite by microwave heating, with the optimum condition including heat holding time of 7.5 min, at the temperature of 650 ℃, carbon content of 1.40%, magnetic current of 0.6 A, and grinding fineness at -0.044 mm, can result in the final iron concentrate grading 61.33%Fe at the recovery of 75.11%, with the yield of 40.17%, which can meet the feed requirement for ironmaking production.