Study On Technology Of Preparing Iron Ore Concentrate And Phosphorus Rich Slag From High Phosphorus Oolitic Hematite

The high phosphorus oolitic hematite is a typical refractory ore and it is difficult to separate Fe from P in the ore when using conventional beneficiation process. In order to achieve effective separation of Fe and P in high phosphorus oolitic hematite, an ore from Hunan province was systematically investigated. Besides the ore’s physical and chemical properties and mineralogical characteristics, the reduction thermodynamics of raw ore and the thermodynamic behavior and conditions of iron oxide and phosphorus oxide in sodium salt roasting were studied, as the results of which, beneficiation indexes of high phosphorus oolitic hematite in magnetic roasting/separation and a new enhancement technology with additive were developed. Theories of thermodynamics and kinetic, the identification of optical microscopy, XRD and microscopic image analysis are used to reveal the separation mechanism of Fe and P in high phosphorus oolitic hematite.(1) Iron grade of raw material is51.28%, the content of P, SiO2and Al2O3are1.30%,8.53%and6.96%respectively. The iron mineral is mainly hematite, which disseminates in the gangue with irregular granular, forming concentric rings with oolitic structure. Phosphorus in iron ore is in the form of apatite, irregular disseminating in the gangue or the oolitic hematite and forming spherulitic aggregates. It is difficult to separate Fe and P effectively using traditional beneficiation as the result of complex structure of Fe, P and gangue in high phosphorus oolitic hematite.(2) After the study of the effects of magnetic roasting/separation, direct reduction and additives on the high phosphorus oolitic iron ore, the optimum conditions were obtained that roasting temperature of1000℃, the carbon content of6%, additive dosage of10%, reduction time of60min, grinding fineness of-200mesh, and the magnetic field strength of0.1T, under which a iron concentrate was get with its iron grade of93.26%, phosphorus content of0.15%, and iron recovery of92.79%. It is a comprehensive utilization of high phosphorus oolitic hematite for Al, Si and P also can be recovered in the tailing by acid leaching, in which slag the phosphorus content can be24%or more. (3) Na2CO3significantly promote the recovery of Al2O3in the acid leaching of tailing, and the leaching rate of A12O3increased from69.75%to93.29%as the Na2CO3dosage was from0%to15%. The leaching rate of SiO2increased to90.37%(4) Thermodynamic studies have shown that apatite can reduced to gaseous phosphorus when carbon was added in the raw material. The reaction was effected by the temperature and gas phosphorus partial pressure. When gas phosphorus partial pressure was0.01%, the initial reaction temperature was about1100K. Part of the material occurred solid phase reaction and formed fayalite and FeO·Al2O3at a low temperature in the reduction roasting. Those products in solid phase reaction continue to reduce to Fe when the temperature was beyond1190K. Sodium is proved to promote the reduction of iron in thermodynamics, for example, Na2CO3can react with SiO2in the temperature below1190K to replace FeO out.