铁尾矿再选粗精矿深度还原含铁硅酸盐矿物的生成与还原

摘要

Test methods including chemical analysis,X-ray diffraction, scanning electron microscope and X-ray energy spectrum analysis were used to study generation and reduction mechanism of silicate minerals containing iron in deep reduction of rough concentrate from Qidashan iron tailings. The results show that when the reduction temperature is lower than 720℃, some iron oxides react with gangue minerals in solid state which increases the iron mass fraction of silicate minerals containing iron from 20.66% to 27.56%. When the reduction temperature is between 770℃ and 930℃, numerous complicated silicate minerals containing rich iron are generated due to the occurrence of a large number of wustite and the addition of Na2CO3 which makes the iron content of silicate minerals containing iron increases from 28.03% to 53.18%. When reduction temperature is 930℃, a lot of hedenbergite and a small amount of fayalite and kirschsteinite are crystallized. Because of the effect of basic oxide (CaO), fayalite can not exist stably in large quantity and transform into hedenbergite and kirschsteinite with better reducibility. Under conditions of high temperature reduction, iron ions in hedenbergite and kirschsteinite get into complicated silicate phase and move to the surface where the reduction reaction occurs. Metallic iron gathers and forms crystal stock on the surface forming iron rim. When the reduction temperature is 1 300℃, the iron content of silicate minerals containing iron decreases to 9.13%.%采用化学分析、XRD分析、SEM及EDS能谱分析方法，对齐大山铁尾矿再选粗精矿深度还原含铁硅酸盐矿物的生成与还原机理进行研究。研究结果表明：低温还原时，部分铁氧化物与脉石矿物发生固相反应，使含铁硅酸盐矿物中的铁(简称硅铁)占全铁的质量分数由未还原时的20.66%增加到720℃时的27.56%；当还原温度为770~930℃时，由于浮氏体大量生成和 Na2CO3的加入，有大量低熔点富铁复杂硅酸盐矿物生成，使硅铁占全铁的质量分数由28.03%增加到53.18%；当升温到930℃时，大量钙铁辉石和少量铁橄榄石、钙铁橄榄石生成，由于CaO的碱性氧化物效应，铁橄榄石不能大量稳定存在而转化为还原性更好的钙铁辉石、钙铁橄榄石。在高温还原条件下，钙铁辉石及钙铁橄榄石中的铁离子进入复杂硅酸盐相中，并迁移到复杂硅酸盐相表面进行还原，还原得到的金属铁沿着复杂硅酸盐相表面聚集连晶，形成金属铁环边产物层；当升温到1300℃时，硅铁占全铁的质量分数可降至9.13%。