Study On Innovative Process And Mechanisms Of High-phosphouse-content Oolitic Hematite Ores Processed By Reduction Roasting-magnetic Separation

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.