【作者】 谢朝明；

【导师】 李光辉； 张元波；

【作者基本信息】 中南大学 ， 钢铁冶金， 2010， 硕士

【摘要】 鲕状赤铁矿是一种典型的难处理铁矿资源,据统计我国约有30-50亿吨储量,占我国红铁矿储量的30%。这种铁矿石含磷高(0.4-1.8%)、铁品位较低(35-50%),铁矿石中的磷主要赋存于胶磷矿中,并与富含氧化铁的鲕绿泥石混杂在一起,形成同心层状相间的鲕粒结构,矿石中氧化铁晶粒粒度细微,且与脉石嵌布关系复杂,难解离。若不改变铁和磷的赋存状态,破坏矿石特有的鲕粒结构,铁就无法精选富集,磷也无法有效去除。目前,该资源尚未得到有效开发利用,尚属于“呆滞”矿产资源。本文以湖南某地鲕状赤铁矿为对象,系统研究了其物化性能以及工艺矿物学特征,针对其复杂的嵌布关系,研究了高磷鲕状赤铁矿还原焙烧的热力学,开发出高磷鲕状赤铁矿还原焙烧-磁选分离的新工艺及添加剂强化还原分选新技术,并结合光学显微鉴定、XRD和显微图像分析揭示了高磷鲕状赤铁矿铁磷分离的机制。(1)查明了鲕状赤铁矿的工艺矿物学特征：赤铁矿呈环带状集合体与脉石矿物的紧密嵌布,铁矿石中的磷主要以胶磷矿的形式出现,胶磷矿在鲕状赤铁矿中主要产出形式是球粒状集合体。铁与磷等脉石成分的复杂嵌布关系导致物理分选铁和磷十分困难。(2)通过高磷鲕状赤铁矿还原焙烧-磁选工艺研究,确定适宜的还原焙烧温度为1050℃,还原焙烧时间为120min,还原产品磨矿细度-0.074mm含量为97.1%,磁场强度为0.1T。此工艺条件下,铁金属化率86.7%,磷挥发率24.3%,精矿铁品位85.1%,铁回收率69.7%,精矿磷品位0.972%,磷脱除率51.4%；加入添加剂可有效强化鲕状赤铁矿的还原分选,在适宜的还原磨选条件下,添加了7.5%硫酸钠和1.5%辅助添加剂BS,铁金属化率达95.8%,磷挥发率25.1%,精矿铁品位92.7%,铁回收率92.5%,精矿磷品位0.086%,磷脱除率96.1%。(3)热力学研究表明,磷灰石在有碳存在的情况下可还原生成气态的单质磷挥发出去,反应受温度和气体磷分压的影响。在气体磷分压为0.01%的时候,反应起始温度约为1100K。高磷鲕状赤铁矿还原焙烧过程中,部分物料在较低温度下先发生固相反应,生成物主要有铁橄榄石、FeO·Al2O3；T>1190K时,上述固相反应产物在还原过程中可被还原Fe。添加钠盐后,碳酸钠和硫酸钠与SiO2均可在低于1190K时发生反应,竞争置换出FeO,使其还原阻碍减少。热力学上证明钠盐添加剂可促进金属铁的还原。(4)结合XRD结果和还原焙烧产物的微观结构分析可知,无添加剂时铁晶粒细小且受界面阻力无法有效聚集；添加钠盐后,随着还原反应的进行,在局部能形成液相,为铁离子的扩散提供条件；而添加复合添加剂后,降低铁晶粒的表面张力,使得细小的铁晶粒聚集长大连成片状,完全破坏了鲕状结构,并与脉石有了明显的界限,有利于后续磨矿、磁选分离出金属铁粉。本研究针对国内量大难处理的鲕状赤铁矿,用廉价煤做还原剂,通过添加剂强化还原分选,由高磷鲕状赤铁矿制备高品位直接还原金属铁粉。随着进口铁矿石价格日益剧增,从长远来看,新工艺是未来鲕状赤铁矿开发利用的有效途径。更多还原

【Abstract】 Oolitic Hematite is a typical refractory iron ore resource. There are approximately 3 to 5 billion tons of reserves in China. Typical characteristics of these oolitic hematite ores include a low total iron grade (35 to 50%) and a high phosphorus content (0.4 to 1.8%). Phosphorus mainly occurs as collophanite and is associated with chamosite that contains iron oxide, and a special concentric and layered oolite texture usually formed. It is very difficult to be processed because of the complex relationship between hematite and gangues in the ring. An innovative process of reduction roasting oolitic hematite ore in the presence of selected additives followed by magnetic separation was developed as an alternative method for utilizing the oolitic hematite resources.Oolitic hematite mainly exists in the form of spherulitic aggregate. Most of the spherulite is fragmentary between calcite and oolite. Phosphorus mainly occurs in a form of collophanite.Proper conditions were as fallows, roasting temperature of 1050℃, roasting time of 120min, grinding fineness of-0.074mm accounting for 97.1%, magnetic separation intensity of 0.1T. At optimum conditions, When processed in the absence of additives, metallization of iron was 86.7%, phosphorus volatilization was 24.3%, the iron concentrate contained 85.1% iron and 0.972% phosphorus; the iron recovery and dephosphorization was only 69.7% and 51.4%, respectively. However an metallic iron product that contains 92.7% iron and only 0.086% phosphorus, metallization of iron of 86.7%, phosphorus volatilization of 24.3% could be obtained when processed oolitic hematite by reduction roasting-magnetic separation with addition of 7.5% Na2SO4 and 1.5% BS. The iron recovery and dephosphorization was 92.5% and 96.1%, respectively.When iron oxide is reduced by carbon, the solid reaction occurs at low temperature resulting in the formation of FeO·SiO2 and FeO·Al2O3, which are reduced to metallic iron when temperature exceeds 1190K. is found to at lower temperature than 1190K when sodium sulfate or sodium carbonate was added during the reduction.The results of X-ray diffraction(XRD) and Microstructure analyzes of the reducing roasting product have proved that the were fine and can not aggregation and growth without additive. After addition sodium salt, it can form the liquid phase partially, provides the condition for iron ion to diffusion along with the reducing roasting. And when added the compound chemical additive, the tiny metal iron crystal would aggregation and growth then become the laminated shape, and destroyed the oolitic texture completely, is advantageous separates the metal powdered iron in the magnetic separation.In view of the domestic the quantity and refractory Oolitic hematite, This research produce the high grade metal by direct reduction by adding suitable additive and used inexpensive coal. Along with the import iron ore price sharp increase, it will be the effective way to exploitation and utilization the oolitic hematite in the future.更多还原