Study On The Carbothermal Reduction Of High Phosphorous Oolitic Hematite And Separation Of Metal With Calcium Oxide

Oolitic hematite is an important sedimentary iron ore in China,which mainly consists of hematite,siderite,oolitic chlorite and limonite.In the process of formation,hematite,limonite and gangue minerals are generally encapsulated by concentric annular layers from the center of oolitic particles,forming multi-layered structures.Meanwhile,the boundary between the iron mineral layer and the gangue layer is not obvious,the intercalated granularity is very fine and the composition is complex.Besides,iron mineral is symbiotic or inter wrapped with other gangue minerals to reduce difficultly.Due to that,the iron mineral has not been effectively used.With the depletion of high grade iron ore resources,people have to pay attention to the development and utilization of low grade iron ore.In this paper,a series of studies were performed on Hezhang oolitic hematite of Guizhou province.Hezhang oolitic hematite has a typical oolitic structure.The iron element(51.2 wt%)mainly exists in the form of iron oxide,partly in the form of ferrous oxide.Phosphorus element(0.69wt%)exists in the form of apatite,and the main phases of gangue mineral are mainly quartz,chlorite,etc.The effects of basicity,reduction temperature,particle size and carbon ratio on the weight loss rate,metallization rate and microstructure of the reduced oolitic hematite have been studied by optical microscope,SEM-EDS,XRD and chemical analysis.Meanwhile,metal separation was achieved by magnetic separation,so the effects of different reduction conditions on the phase composition,iron grade,iron recovery rate and dephosphorization rate of iron concentrate were also studied.The results show that increasing the temperature can reduce the nucleation barrier of iron particles,accelerate particle diffusion to promote the nucleation and growth of ironparticles.The agglomerate and grow of metal iron could easily come ture when the particle size of oolitic hematite was 160-200 mesh.And increasing of the carbon ratio can increase the contact area between the reducing agent and the reactants,promote the reduction of the oolitic hematite,and the aggregation is also more obvious.The reduction reaction is weak under natural basicity.With the increase of basicity,the accumulation and grown of iron particles was enhanced,and the contour of oolite was damaged seriously,as well as the impurity component in the oolite decreased.Adding additives could decrease the melting point of reactant,which could improve the kinetic condition of the reduction and gather and grown of metallic iron particles.When the content of borax was 6%,the results of the reduction of oolitic hematite was the best.With the increase of reduction temperature,basicity,carbon ratio and particle size,the recovery and dephosphating rate of iron have been improved.Iron grade only decreased with the increase of basicity,and increases under other conditions.when temperature was 1150 ?,carbon ratio was 1.0 and basicity was 1.0,the metallization rate was 90.30%,iron grade was 61.87%,iron recovery rate was 87.63% and dephosphorization rate was 62.91%.