红土镍矿选择性还原焙烧过程中的相变转化

针对传统选矿方法难以回收低品位红七镍矿中有价金属镍的问题,采用选择性还原焙烧法研究了不同焙烧温度以及不同焙烧时间条件下红土镍矿(Ni品化为1.49%)中发生的微观结构变化以及相变转化.通过X射线衍射、扫描电镜及X射线能谱分析等测试手段分析表明,在不同焙烧温度及不同时间条件下经选择性还原后的红土镍矿中,镍氧化物逐渐被还原成镍铁合金相,铁氧化物主要转变成浮氏体相,硅酸盐主要以橄榄石形式存在.最后通过还原焙烧磁选试验证实,还原剂为烟煤,添加剂为NCS,两者用量分别为原矿质量的2%和7%,在1200℃条件下焙烧50min,磁选分离得到镍铁产品中镍品位为9.78%,镍的回收率为92.06%,镍铁回收率差为62.51%,实现了红土镍矿中镍铁的选择性还原.

Phase transformation of nickel laterite ores in the selective reduction roasting process

Since it is difficult to extract nickel from laterite ores with low nickel grade by traditional beneficiating methods, the microstructure and phase transformation of a nickel laterite ore with the nickel grade of 1.49% were investigated by using a selective reduction roasting method at different roasting temperatures and time. X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS) results show that after selective reduction roasting at different roasting temperatures and time, nickel-ferrous minerals in the nickel laterite ore are reduced to ferronickel gradually, while ferrous minerals are mainly transformed to wustite. Silicate nfinerals exist in the formation of olivine in the roasted ore. Reduction roasting and magnetic separation experiments illustrate that when the nickel laterite ore with the addition of 7% NCS as the additive and 2% soft coal as the reductant roasts for 50 min at 1200℃, the ferronickel product obtained from magnetic separation has the nickel grade of 9.78% with the nickel recovery of 92.06%, and the recovery difference of nickel and iron is 62.51%. The experimental result indicates that nickel-ferrous and ferrous minerals were reduced selectively.