Phosphorus Migration Behavior In Pre-reduction Sintering Process Of Bayan Obo Iron Concentrate

China's high-phosphorus iron ore resources are abundant,but the high phosphorus content not only increases the dephosphorization load and cost of steelmaking,but also seriously restricts the recycling of steel slag resources,making it impossible to fully utilize.The traditional dephosphorization method has not been able to achieve large-scale industrial application,and dephosphorization technology has always been a problem that plagues domestic and foreign scientific research workers.Based on the occurrence of phosphorus in the Bayan Obo mine in the early stage and the effect of pre-reduction and sintering process of Bayan Obo mine on dephosphorization,Pre-reduction and sintering gasification dephosphorization process around iron concentrate,In-depth study of the migration behavior of phosphorus in the pre-reduction sintering process and the temperature and pressure distribution of each zone of the sintered layer,Provides data support for pre-reduction sintering dephosphorization.In order to optimize the process parameters of pre-reduction and sintering gasification dephosphorization of iron concentrate,this paper combines Fact Sage thermodynamic calculation with vacuum tube furnace experiment.On the basis of determining the appropriate dephosphorization agent type and its addition amount,the effects of parameters such as carbon content and reduction temperature on dephosphorization were optimized.The optimum process parameters for pre-reduction and sintering dephosphorization are 20%carbon content,3% SiO₂ addition,1% Na₂CO₃ addition,31% dephosphorization rate at 1050?,and 96% metallization rate.The reduction mechanism was studied by thermodynamic software,X-ray diffraction?XRD?and scanning electron microscopy?SEM-EDS?.The results show that the temperature required for carbothermal reduction and dephosphorization is higher,and the gasification and dephosphorization rate is lower.The pure reagent SiO₂ is added to reduce the reduction temperature of the phosphorus-containing minerals,and the pure reagent Na₂CO₃ is added to react with the gangue components around the phosphorus-containing minerals to open the gangue minerals to encapsulate the phosphorus-containing minerals,and the gasification dephosphorization rate is significantly increased;The reduction is an endothermic reaction,and the temperature rises and the reduction reaction proceeds sufficiently.However,if the temperature is too high,the irregular movement between the molecules is severe,the viscosity of the reduced material decreases,the kinetic conditions of the phosphorus-containing gas entering the metal iron are improved,and the gasification dephosphorization rate is lowered;with the increase of the carbon content,the reduction of the phosphorus-containing mineral is The iron oxide is not completely reduced before it is completely reduced,and the gasification dephosphorization rate is increased.However,if the carbon content is too high,the reduced phosphorus gas easily enters the metal iron to form Fe_XP,resulting in a decrease in the gasification and dephosphorization rate.After the phosphorus-containing mineral is reduced,part of the phosphorus enters the iron phase in the form of elemental phosphorus,forming a stable iron-phosphorus compound,resulting in a decrease in the gasification and dephosphorization rate.In this paper,the migration of phosphorus during pre-reduction and sintering is analyzed in a time-sequential order.The results show that the reduction time increases from 20min to 60min,the dephosphorization rate of iron concentrate increases from 13% to 31%,and the dephosphorization rate of ore is increased from 25%to 32%.The metallization rate of iron concentrate increased from 92%to 96%.The ore metallization rate increased from 85% to 96%.As the reduction time increases,the phosphorus-containing minerals are fully reduced,and the phosphorus-containing gas enters the iron phase to form FexP.The results of quantitative analysis of electron probe showed that the C content increased from 3.654% to 5.368% and the P content increased from 0.063% to 0.487% as the reduction time increased from 10min to 50min.C and P have the same surface distribution in the iron phase,and the reduced P easily replaces C in Fe₃C into the iron phase.In order to find out the effect of carbon content on the temperature and pressure distribution of each zone of the sinter layer,the micro-sintering cup experiment showed that the carbon content increased from 5%to 20%,and the sintering time was shortened from 37min to 30min.It rose from 1215? to 1342?.The heat transfer rate of the material layer is increased,and the heat storage effect is obvious.The time-temperature characteristics of the sintering process play an important role in the formation and composition of minerals.The carbonation increases,the chemical reaction changes from solid phase reaction to solid-liquid three-phase reaction,the mineral adhesion is enhanced,the sandwich raw material is reduced,and the sintering reaction is severe.The liquid phase increases the permeability of the material layer.During the sintering process,the temperature rise trend and the maximum temperature of the layer increase with the increase of the carbon content,and the gas flow rate and gas permeability change,so different temperature curves are exhibited from the top to the bottom of the layer.Through the actual temperature measurement of the material layer,the gasification of phosphorus in the sintering process is mainly concentrated in the combustion zone?700?-the highest temperature?,the sinter zone?the highest temperature-surface temperature?,the maximum can be achieved in the sintering cup experiment The dephosphorization rate was 15%.