Investigation On Effective Beneficiation Of Microfine Low-grade Hematite

With the quick development of Chinese steel industry, the demond for iron ores has been much stronger than recently. According to the domestic and international research about the status quo of fine iron ores, this paper summarized up the current processing technology of fine iron ores. Based on the research of mineralogy and characteristics of the raw ore, embedment relationship of minerals were introduced and analyzed. For the special composition, fine granularity and other characteristics of such ores, several traditional beneficiation methods, such as magnetic separation, flotation and the combined technology were attempted. According to the research, a new processing route, flotation-direct reduction-magnetic separation was finally adopted in this paper. Detailed studies were also carried out through experiment.Detailed studies were carried out based on the mineralogy of two iron ores with the aid of several modern microcosmic testing methods, such as XRD, SEM, and optical microscopes analysis. Quartz is the main gangue mineral in both iron ores. For Jiangkou ore, fine-grained hematite (mostly in the range of 3-5μm) is the major iron mineral which is uniformly distribute in the gangues with dot form. There is also a little iron minerals intermix with gangues as the dip-dye form. For Hainan tailings, the main iron mineral is specularite with the form of shred and needle. Crystal granularity is generally in the range of 5-50μm. Minor minerals include magnetite, limonite, pyrite and so on. Most of iron minerals also intermix with gangues and embed with other minerals. In short, from the mineralogy of these two iron ores, both of iron ores are difficult to beneficiate.High intensity magnetic separation, magnetic roasting-magnetic separation, magnetic separation-flotation (including flotation, and reverse-flotation, anion, cation, etc.) and other beneficiation methods were adopted to get the elemental concentrate. The results indicate that, we can get the preliminary concentration by flotation. With the closed stage-grinding route, the granularity below 0.074mm≥95%, the dosage of sodium hydroxide, starch and laurylamine are 200g /t, 1400g /t, and 200g /t, respectively. A concentrate with a grade of 33.70% TFe and the recovery of 49.87% was yielded. For Hainan tailings, a concentrate with a grade of 39.96% TFe and the recovery of 74.97% was also yielded under the same experimental parameters. It was shown that the flotation had little effect on beneficiation of Jiangkou ores, while had obvious impact on the enrichment of HANNAN tailing.Conglomerations with above 90% recovery were yielded under 950℃and 1000℃for the two concentrates after pre-beneficiation with coal based direct reduction process. After two phases grinding-magnetic separation, iron concentrate with grade of 65 % and 90% TFe, recovery of 75% TFe and low impurities was also obtained, which could be directly used as burden of electrical furnace.According the theory, under the high temperature, low-grade iron ore with high content of silicon dioxide easily reacts with metal oxide to generate low melting point metal oxide compound-2FeO·SiO₂, whose melting point is very low. Therefore, low melting point compounds such as 2FeO·SiO₂ will generate, intenerate and melt, forming great amount of fluid, which will enwrap the surface of the conglomeration, affecting diffusion of reduction gas into the conglomeration.The utilization technology of the poor, fine, miscellaneous and complex iron ore resources in China was studied in this paper with the aim of providing an innovative method to develop and utilize these resources, making a great positive impact on the reducing degree of dependence on foreign iron ore resources.