镍沉降渣深度还原过程中的相变特征

Phase transformation of nickel slag in settlement furnaces during deep reduction

通过化学成分、光学显微镜、X射线衍射、扫描电镜能谱分析等测试手段,分析了镍沉降渣矿物成分和嵌布特点和沉降渣深度还原过程中物相的转变特征,结果表明,渣的物相由铁镁橄榄石和玻璃质组成.渣中主要有用成分铜镍铁硫化物嵌布粒度微细,分布无规律,回收困难.经深度还原,沉降渣逐渐转变为镁黄长石、含镍金属铁、辉石、钙霞石、钠闪石、石英等新的矿物成分,加热至1300℃,还原产物物相组成稳定,镁黄长石和含镍金属铁相对含量最高.还原时间也是影响还原效果重要因素,含镍金属铁相对含量随还原时间的增加而增长,120 min时相对含量最高.热力学分析表明,镍沉降渣深度还原过程中主要发生的反应为铁镁橄榄石与氧化钙作用生成镁黄长石和Fe O,Fe O被C和CO还原为金属铁.金属硫化物与Ca O和C通过氧化还原作用,生成的金属铜和镍溶于金属铁中,产生的Ca S与硅酸盐一起析出.

In this study,the mineral composition and embedded features of the nickel slag as well as its phase transformation in a settlement furnace during deep reduction were investigated through chemical composition analysis,X-ray diffraction,optical microscopy,scanning electron microscopy,and energy dispersive spectrometry. The results show that the phase composition of slag includes hortonolite and glass. The Cu-Ni-Fe sulfide mineral is distributed in the silicate irregularly,and the sulfide material is too small to reclaim. The nickel slag transforms into akermanite,ferronickel,augite,cancrinite,riebeckite,and quartz by deep reduction. The process is characterized by constant mineral components of reduzate,and the contents of akermanite and ferronickel are the most when heated to 1300 ℃. The reduction time is also an important factor during the process,and the contents of ferronickel increase over time,maximizing at 120 min. The thermodynamic analysis shows that the main reaction performed during the reduction is that olivine and calcium oxide transform into akermanite and FeO,and then the FeO is reduced to iron by C and CO. The metal sulfides,calcium oxide,and C are transformed into copper and nickel and then dissolved in the iron,and the Ca S then crystallized out with the silicate minerals.