【作者】 崔瑜；

【导师】 朱德庆； 潘建；

【作者基本信息】 中南大学 ， 钢铁冶金， 2011， 硕士

【摘要】 作为世界上镍消费量最大的国家,我国每年需要进口大量镍矿,其中绝大多数为红土镍矿,所生产的镍主要作为不锈钢原料。对有效利用低品位红土镍矿作为镍铁合金原料的研究在国内处于刚刚起步的阶段。在国家自然科学基金项目(低品位红土镍矿制备高镍精矿基础理论与工艺研究,50974135,2010年)以及国家发改委基金项目(高效利用低品位红土镍矿关键技术研究,NDRC-高新办2009-606,2009年)的资助下,本文针对印尼低品位褐铁矿型以及腐殖土型红土镍矿进行了选择性还原焙烧-湿式磁选制备高品位镍铁精矿新工艺及其机理研究。对红土镍矿工艺矿物学、镍钻赋存状态、选择性还原反应理论基础和热力学、还原过程各工艺参数的优化、还原过程铁镍钴行为以及选择性还原过程中添加剂作用机理等方面进行了系统的分析和阐述。印尼红土镍矿原矿工艺矿物学以及矿物晶体化学研究表明：LN矿样属于褐铁矿类型红土镍矿,镍含量为0.97%。含80%针铁矿和13%硅酸盐矿物,针铁矿物相含镍0.87%,硅酸盐矿物含镍1.19%。SN矿样属于腐殖土型红土镍矿,镍含量为1.42%。含30%针铁矿和65%硅酸盐矿物,针铁矿物相含镍1.59%,硅酸盐矿物含镍1.07%。在两种矿样中,镍在针铁矿晶格中取代铁,在硅酸盐矿物中取代镁。针铁矿与硅酸盐矿物微观结构表现多样化,矿物共生关系复杂,镍在含镍矿物中分布不均匀,与微观结构有关。钴主要赋存于钴土矿中,钴土矿与针铁矿紧密共生选择性还原理论研究表明：在热力学上对于氧化镍以及浮氏体的选择性还原存在可能,在还原焙烧过程中控制CO浓度约在10%到50%之间、还原温度约在435。C到720℃之间时,可以形成只还原氧化镍不还原浮氏体的选择性还原条件。然而由于在实际操作中以及工业应用上的困难,很难达到选择性还原效果。研究表明还原过程中铁橄榄石的形成以及硫的存在可以提高还原选择性以及促进镍铁晶粒的生长。通过优化选择性还原过程工艺参数,得到了褐铁矿型红土镍矿单矿选择性还原-湿式磁选富集镍的优化条件,即添加3.0%的还原剂、3.0%的硫酸钙、碱度为0.07的LN红土镍矿团块在1250℃的温度下还原焙烧60 min,将还原试样磨矿磁选分离。在该条件下可以获得高品位镍铁精矿,精矿含镍5.10%、含铁82.66%,镍回收率为98.79%,镍铁精矿产率为24.60%。配加SN矿样的LN红土镍矿选择性还原焙烧-湿式磁选富集镍的优化条件为,对添加40.0%SN矿样、5.0%还原剂、6.0%硫酸钙的LN红土镍矿团块进行选择性还原焙烧,还原条件为一段还原温度为900℃,还原时间为15min,二段还原温度为1100℃,还原时间为60 min,之后对还原团块进行磨矿磁选。可获得含镍6.01%、含铁69.69%高品位镍铁精矿,镍回收率为92.08%,镍铁精矿产率为21.45%。这两种镍铁精矿镍品位高,是电炉冶炼镍铁合金的理想炉料,可以为电炉生产节省大量能耗、显著降低渣量,为有效利用低品位红土镍矿资源,特别是为火法工艺利用褐铁矿型红土镍矿提供了一条有效途径。选择性还原反应动力学以及还原团块微观结构研究结果表明：添加剂显著提高了红土镍矿选择性还原反应速率。还原团块主要物相为γFe-Ni相、浮氏体、尖晶石等。镍被有效富集于γFe-Ni中,铁则大部分赋存于浮氏体、尖晶石中,实现了选择性还原。含硫添加剂的存在使得还原团块中γFe-Ni物相的平均粒径由5.8μm提高到16.1μm,粒径大于10μm的γFe-Ni颗粒比例由20%左右提高到45%左右。硫主要与铁形成硫化物固溶体,无硫化镍存在,这一结果与热力学相图一致；置换反应的生成可能导致镍、钻富集程度高的Fe-Ni-Co固溶体在铁硫化物物相中的析出。更多还原

【Abstract】 The rapid expansion of domestic stainless steel manufacture dramatically increased demand for nickel in recent years. Study on using low grade laterite ore to produce ferronickel is in the ascendant. With the funding of National Natural Science Foundation of China (Theoretic Study and Process Development on Manufacturing High Nickel Concentrate from Low Grade Laterite,50974135,2010) and National Development and Reform Commission (Key Technology for Highly Efficient Utilization of Low Grade Laterite, NDRC-Hitech Office 2009-606,2009), this paper has been focused on the mineralogical study of low grade laterite ore samples from Indonesia and selective reduction-magnetic separation process to manufacture high nickel grade concentrate from laterite. This work also conducted study on raw laterite mineralogy, mechanism of selective reduction, optimization of selective reduction parameters, and both nickel and sulphur behavior during reduction.The study of mineralogy and crystal chemistry of raw laterite ore sample found that:the limonitic sample consists of some 80%and 13% silicate minerals. Goethite and silicates are the Ni host phases which contain 0.87 % and 1.19 % Ni, respectively. The saprolitic sample consists of some 65% silicate minerals and 30% goethite. Silicates and goethite are the Ni host phases, which contain 1.07% and 1.59% Ni respectively. Cobalt was mostly found occurring in asbolane from both laterite ore samples.The thermodynamic study of nickel laterite selective reduction found that:from the thermodynamic viewpoint, under the conditions that the CO concentration between 10% to 50% and temperature between about 435℃to 720℃, the selective reduction of NiO over FeO could be achieved. From the industrial practice, however, this is too strict to be conducted. The addition of silica and sulphur was reported to be beneficial both to selectivity of the reduction and the growth of nickel metallic.The optimization of selective reduction-magnetic separation process found that:Concentrate assaying 5.1% nickel could be manufactured from single limonitic laterite ore sample with nickel recovery of 98.79%. The reduction was conducted under the conditions that 3.0% additive and 3.0% coal was added, blend basicity at 0.07 and the calcination was carried out at 1250℃for 60 min. When 40.0% SN laterite sample,5% reductant and 6.0% CaSO4 was added, the LN sample was calcinated at 900℃for 15min and then 1100℃for 60 min. Concentrate assaying 6.01% nickel was thus manufactured at a recovery of 92.08%.The Mineralogy and crystal chemistry study of reduced sample found that:main phase of reduced sample was y Fe-Ni, wustite, spinel et al.. Relatively high Ni was observed from y Fe-Ni, whereas Fe was mainly presented in wustite and spinel, the selective reduction was thus achieved. The present of sulphur contributed more formation of metallic phase with size over 10μm, the mean size of y Fe-Ni particles were increased from 5.8μm to 16.1μm after the additive was added. Iron monosulphide was observed as well as Fe-Ni-Co solid solution which with high nickel concentration, but no nickel sulphide, due to the replacement reaction between Fe and Ni/CoS. The thermodynamic theories and phase diagram successfully predicted the selective reduction and mechanism of sulphur behavior.更多还原