Study On Behaviors Of Red Mud Direct Reduction And Reduction Reinforcement

In recent years,with the rapid development of iron and steel industry of China,mineral resources of high grade ore and easy-smelting ore are declining and even exhausted.Therefore,it is of significance to intensify utilization of domestic complex iron ore resources.Red mud is the main waste of alumina industry and it is of great valuable for the comprehensive utilization.In this research,the iron,aluminum-silicon bearing red mud was obtained from Guangxi gibbsite which was leached Bayer process.Based on the investigation of mineralogy,it could be found that aluminum scatters into the iron minerals,which mostly existed in the shape of goethite.So it was difficult to separate iron and other gangue.In this research,it could be effective for the separation of iron and other rocky minerals by using the technology of direct reduction.By using advanced testing methods,such as optical microscope,SEM,XRD,the behaviors of Fe,Al,Si in the process of direct reduction were researched and the research could provide theory instruction for the separation of iron and aluminum.(1) Based on the coal-direct-reduction,it showed that with the rising of reduction temperature and reduction time,the separation of iron and other gangue became more and more easily.Concentrate with the grade of 72.07%and recovery of 79.34%could be obtained under the conditions of reduction temperature 1150℃,reduction time 180min,the content of granularity below 0.074mm 89.7%,magnetic intensity 8×10⁴ A/m.(2) The results of reaction behavior of red mud showed that,during the heating process,goethite,diasporas bauxite,gibbsite and kaolinite would firstly dehydrate and then turn into iron oxide,aluminum oxide and silicon oxide.The analytical results of reduction thermodynamics showed that FeO,Al₂O₃ and SiO₂ could easily react into hercynite (FeO·Al₂O₃) and ferrospinel(2FeO·SiO₂),which would counteract the further reduction of FeO.According to the researches of reduction products by optical microscope,SEM,XRD,it could be indicated that fine iron grains were enwrapped by the low-melting minerals such as hercynite(FeO·Al₂O₃) and ferrospinel(2FeO·SiO₂),which destrained the diffusion of reducing gaseous and caused that it was difficult for the magnetic separation of iron and other gangue.The effects of aluminum and silicon on the reduction behaviors of iron oxidize were researched and the results showed that aluminum oxidize,silicon oxidize and iron oxidize could mutual diffuse and take place solid phase reaction,which made effective on the iron reduction.(3) In this research,additives were used to reinforce red mud reduction.And the results indicated that CaF₂ and Na₂CO₃ could accelerate the reduction of red mud.Under the follow condition: reduction temperature 1150℃,reduction time 180min,the content of granularity below 0.074mm 89.7%,magnetic intensity 8×10⁴A/m,CaF₂ 5%,Na₂CO₃ 5%,Concentrate with the grade of 85.14%and recovery of 87.89%could be obtained.CaF₂ and Na₂CO₃ could limit the formation of hercynite(FeO·Al₂O₃) and ferrospinel(2FeO·SiO₂),which caused that the reaction of FeO to Fe was easier to proceed and iron grains were easier to grow into serial iron crystals.The interfaces between ferrous metal and other low-melting minerals were obvious and the magnetic separation got better.