CaF_2对褐铁矿型红土镍矿真空焙烧及碳热还原的影响

Effect of CaF2on the Phase Transformation and Vacuum Carbothermal Reduction of Limonitic Laterite Ore

以CaF_2为添加剂,探究了褐铁矿型红土镍矿在真空条件下焙烧对产物物相及碳热还原的影响。通过XRD、SEM、EDS和化学分析等手段,对焙烧后产物的物相以及还原后富镍铁剩余物中物相的种类进行分析。真空焙烧结果表明:在10～50 Pa的真空条件下焙烧,物料的形态(即焙烧温度)对焙烧结果影响较大,在未熔化的物相中Ni和Fe的最大富集程度分别仅有1.84%和53.10%,而在物料熔化后聚集的NiFe_2O_4、Fe_2O_3中,Ni、Fe的最大富集程度分别达到67.35%和75.16%。热力学分析和还原结果表明:CaF_2在反应过程中会与原料中的Fe、Ni反应形成FeF_2、FeF_3、NiF_2等低熔点共熔体促进物料熔化,加速反应物的传质与传热,有效促进Ni、Fe的团聚,另外,添加CaF_2对真空碳热还原褐铁矿型红土镍矿剩余物的物相没有明显影响;褐铁矿型红土镍矿最佳的还原条件为还原温度1 450℃、CaF_2添加量5%,还原后Ni、Fe的回收率分别达到99.05%和88.23%。

The effects of CaF2 on the phase of product from vacuum carbothermal reduction of limonitic laterite ore at vacuum conditions were studied. XRD, SEM/EDS and chemical analysis methods were used to analysis the phases of roasting product and the Fe-Ni rich residue. The roasting results indicated that there were significant influence on the roasting results under pressures ranging from 10 to 50 Pa whether the raw materials melted(roasting temperature), the content of Ni and Fe in the unmelted phase only reached 1.84% and 53.10%, respectively;nonetheless, on the melted materials, the content of Ni in the NiFe2O4 reached 67.35% and the content of Fe in the Fe2O3 reached 75.16%. The thermodynamic analysis and reduction results indicated that CaF2 reacted with Fe and Ni in the raw materials to form FeF2, FeF3, NiF2 and other low melting point eutectic to promote material melting and accelerate the mass transfer and heat transfer of the reactants, and effectively promote the agglomeration of Ni and Fe, in addition, the presence of CaF2 had no significant effect on the phase of roasting product duringthe vacuum carbothermal reduction of limonite;the optimum reduction conditions of limonite type laterite nickel ore were 1 450 ℃ and 5% dosage of CaF2. The recovery rates of Ni and Fe after reduction were 99.05% and 88.23%, respectively.