Research On Reduction Roasting-magnetic Separation Process Of High Phosphorus Oolitic Hematite For Iron Concentration And Phosphorus Removal

High-phosphorus oolitic hematite is one of the iron ore types that are considered difficult to be utilized in the world.It is widely distributed and its total reserves accounts for about 11%of China's iron ore resources.The main components besides hematite are gangue minerals such as hematite chlorite and quartz.The iron ore and gangue in the oolitic hematite are of extremely fine grain size and wrapped in each other,so there are obstacles in the selection and extraction of the mineral.The chemical and mineral composition of high phosphorus oolitic hematite were analyzed and the reduction roasting-magnetic separation process was adopted to study the effect of phosphorus removal and iron concentration in this paper.The iron grade of raw material is 46.75%,the phosphorus content is 0.92%,and the SiO₂ content is 10.69%.Factsage software was adopted for the thermodynamics calculation of raw material roasting and phosphate mineral conversion,the effect of roasting process?holding time,temperature?,particle size,alkalinity,type and amount of additives and magnetic field intensity on iron grade,iron recovery and phosphorus removal rate were studied respectively.The following conclusions are drawn from the study.?1?From the reduction temperature of fluorapatite in oolitic hematite is much lower than that of pure fluorapatite.In the reduction process of oolitic hematite,the higher the temperature is,the stronger the reducing atmosphere CO is,and the more stable the reduced metal iron is.And the appropriate roasting temperature was 1000?¹250?obtained form thermodynamic calculation.?2?The results showed that under the same process conditions without additives,the iron concentrate grade and phosphorus content were 68.73%and 0.52%respectively,the iron recovery rate and phosphorus removal rate were 71.63%and 43.48%.Through monography and SEM analysis,the iron particle was not effectively concentrated and wrapped with gangue mineral,which lead to the low removal rate of phosphorus.?3?The optimum process parameter obtained from experiment are as follows:in the reduction roasting process,the 140 mesh iron ore was calcinated at 1100?for 60 min,with pulverized Russia anthracite amount of 11%,alkalinity of 0.8,and compound additive of YM-2 is 12%;in the magnetic separation process,the reduction product was ground to-200 mesh with weak magnetic field intensity of 1000 Gs.The final iron concentrate with iron grade of 80.96%and phosphorus content of 0.094%was obtained from the optimum condition experiment,where the dephosphorization rate is 89.78%.After magnetic separation process,the particles of metallic iron,gangue and other minerals are enriched and separated respectively,which creates favorable dynamic and kinetic conditions for the reduction extraction of iron and removal phosphorus of oolitic hematite.?4?Compound additives is more effective than that of a single additive in concentrating iron and removing phosphorus.YM-2 additive can not only inhibit the reduction of fluoropatite,but also promote the aggregation of metal iron,so the effect of raising iron and removing phosphorus is significant.