添加剂对低镍高铁红土镍矿选择性还原的影响

Research on the effect of additive on selective reduction of the laterite ores with low nickel and high iron content

采用还原焙烧-磁选法处理低镍高铁型红土镍矿,研究了添加剂(Na2SO4,Na2CO3,CaCO3和CaSO4)对镍、铁矿物选择性还原的影响规律,并通过X射线衍射(XRD)、扫描电镜-能谱分析等方法,分析了添加剂作用下焙烧矿中矿物成分、相变转化、微观结构特征及元素赋存状态.结果表明:添加剂Na2CO3,CaCO3及CaSO4作用下选择性还原效果较差,而Na2SO4作用效果明显,在Na2SO4用量10%,烟煤用量2%,1 250℃焙烧50min条件下,获得镍铁产品中镍的品位为9.52%,镍回收率88.40%,镍铁回收率之差达60.50%,实现了镍铁矿物的选择性还原,其原因是Na2SO4作用下弱还原气氛抑制了浮氏体还原成金属铁,降低了铁的回收率,同时Na2SO4分解出的S降低了镍铁颗粒的表面能和熔点,而且焙烧矿呈熔融状态,促进了镍铁颗粒长大,有利于镍铁颗粒与脉石矿物充分分离.

A nickel laterite ore with low nickel and high iron content was processed by the coal- based direct reduction method. The selective reduction effect of laterite was studied with adding several additives such as Na2 SO4, Na2 CO3, CaCO3 and CaSO4 respectively in the roast- ing process. The composition of the roasting ore and the phase transition occurred in the roast- ing process were analyzed by X-ray diffraction （XRD） with addition of different additives. Mo- reover, the microstructures and elements of the roasting ore are investigated by the scanning e- lectron microscopy and energy spectrum analysis with addition of the Na2 SO4. The experimen- tal results show that Na2 CO3, CaCO3 and CaSO4 have no obvious effect on the selective reduc- tion of laterite ore, while Naz SO4 has a significant effect. The ferronickel product has a high Ni grade of 9.52% with the nickel recovery of 88.40%, while the difference of the nickel and total iron recovery is 60.50% at 1 250 ~C for 50 min with The reason was that wustite couldn＇t be reduced to addition of 10% Na2SO4 and 2% bitumite. metallic iron under the weak reduction at-mosphere, which reduced the recovery of iron. In addition, the structure wreckage of silicate made the roasted products melted, and sulfur could reduce the surface tension of metallic parti- cle, which enhanced the size of the metallic particle. And the metallic particle with high nickel content could be separated with gangue completely by the grinding-magnetic separation process,