低品位红土镍矿与赤泥共还原焙烧全资源化过程中矿物转化规律及机理研究

Laterite ores are one of the refractory nickel resources, the nickel and iron of which can be effectively recovered by the process of direct reduction-magnetic separation. However, alkaline metal compounds usually must be added to enhance reduction of laterite ores, and secondary tailings generated were hard to be utilized. The red mud contains a large amount of alkaline components, and there is no effective way for large-scale utilization of red mud at present. The research results have demonstrated the feasibility of co-reduction of the low grade laterite ore and the red mud. The nickel and iron in laterite ores and iron in the red mud were recovered simultaneously through subsequent magnetic separation. Meanwhile, a secondary tailing suitable for preparing the building materials was obtained, realizing the resourcing of low grade laterite ore and the red mud. However, the factors influencing the co-reduction process and the mineral transformation laws during the co-reduction have not been investigated systematically. The objectives of this project are to investigate the effect factors and their mechanism on the co-reduction and magnetic separation. The effects including the types and ratio of low grade laterite ores and the red mud, the types and dosages of the reductants, and the reduction temperature and duration on the mineral transformation during the co-reduction are investigated. The migration and growth of the nickel and iron metal particles and the mineral transformation and interrelation of the non -metal element are revealed. The results obtained in this project will enrich the direct reduction theory of different ores, provide a basis for further improvement of the process, and are very important significance and practical value.

低品位红土镍矿是难回收的镍资源之一，通过还原焙烧-磁选工艺可以较有效的回收其中的镍和铁，但常需添加碱性金属化合物才能获得好的效果，产生的二次尾矿也难以利用。赤泥中含有大量碱性成分，且目前未找到有效的大规模利用途径。研究表明，将低品位红土镍矿与赤泥共还原焙烧，再经过磁选可以回收红土镍矿中镍、铁以及赤泥中铁，同时获得适于制备建材的二次尾矿，可以实现低品位红土镍矿和赤泥全资源化利用，但该过程的影响因素和影响规律，尤其是共还原焙烧过程矿物转化规律不清楚。本项目的目的就是研究低品位红土镍矿与赤泥共还原焙烧-磁选过程中的影响因素及机理，查明低品位红土镍矿与赤泥的种类与配比、还原剂的种类与用量、还原温度和时间对共还原效果的影响和矿物转化的规律和机理，揭示共还原焙烧过程中生成的镍、铁金属迁移和颗粒生长规律。研究结果可丰富不同矿石直接还原过程的理论，同时为工艺改进提供依据，有重要的学术意义和实用价值。

低品位红土镍矿用直接还原焙烧-磁选可得到镍品位较高的粉状镍铁，但会产生大量目前无法利用的酸性尾矿。赤泥是强碱性固体废弃物，目前的利用率只有4%左右，上述二者都亟需解决综合利用问题。把低品位红土镍矿和赤泥进行共还原焙烧-磨矿磁选，不仅能同时回收红土镍矿中的铁和镍及赤泥中的铁，也可以用红土镍矿的酸性中和赤泥的碱性，使共还原尾矿也能综合利用，实现低品位红土镍矿和赤泥全资源化利用。因此，研究低品位红土镍矿和赤泥共还原过程的影响因素及矿物转化规律有重要的意义。用褐铁矿型、过渡型和腐殖土型三种红土镍矿，拜耳法、烧结法及拜耳法赤泥经强磁选后的富集赤泥三种赤泥为原料，系统研究了红土镍矿和赤泥共还原过程的影响规律及机理。还原剂种类的研究结果表明，共还原产生粉状镍铁的品位和回收率与还原剂的固定碳含量有相关性，但不是决定性因素，还与还原剂的挥发分和灰分含量相关；提高焙烧温度粉状镍铁的品位和回收率也会升高。低品位红土镍矿和赤泥不同组合共还原的研究结果表明，红土镍矿类型对共还原-磁选效果起主要作用，而赤泥类型的影响相对较小。赤泥种类相同时，红土镍矿类型对共还原过程非金属矿物组成有明显影响，主要体现在辉石含量上。增加赤泥比例和升高焙烧温度可以有效地提高铁回收率并降低尾矿中铁含量，更有利于共还原尾矿的利用。共还原可以明显消除红土镍矿的强酸性和赤泥的强碱性。低品位红土镍矿和赤泥对共还原产物的可磨度有明显影响，赤泥比例增加，共还原产物的相对可磨度增加，温度升高，可磨度降低。共还原产品磨矿产品中金属铁单体铁颗粒数量最多，且其在粗粒级中明显富集。以直径4.8m，长70m的回转窑为主体焙烧设备，进行了共还原的工业试验，证明了低品位红土镍矿与赤泥共还原-磁选在工业上也是可行的。对共还原尾矿制备工业陶瓷也进行了初步研究，基本证明是可行的。研究结果为低品位红土镍矿和赤泥的全资源化利用提供了新途径。