Study On Vanadium-Titanium Magnetite Carbon Composite Hot Briquette As A New Type Burden Of Blast Furnace

As a special mineral resource rich in Fe,V,Ti and other important metal elements,vanadium-titanium magnetite(hereinafter abbreviated as VTM)is widely distributed in Sichuan Panzhihua,Hebei Chengde and Anhui Maanshan region.In recent 60 years,with the deepening of the research about VTM,the technology of smelting VTM in BF has made great progress.While,owing to the VTM own characteristics lean,fine,scattered and complex,it's tranditional agglomeration process(sintering and pelletizing)is difficult,and the core technical indicators of BF are poor,such as low BF availability,high coke ratio etc.So,it is necessary to exploit a new type material of VTM for BF ironmaking.As a new type raw material for ironmaking,carbon composite iron hot briquette(hereinafter abbreviated as CCB)shows great reducing performance and high strength,and it has become hot spot of research as one of innovative technologies for ironmaking.Based on all above,this paper put forward the preparation of vanadium-titanium magnetite carbon composite hot briquette(hereinafter abbreviated as VTM-CCB).During its preparation,the influence of hot-pressing temperature,carbon ratio,VTM size and coal size to the compressive strength of VTM-CCB were explored.After that,the reasonable heat treating conditions including heat treating temperature and heat treating time were investigated.Further,the metallurgical properties of VTM-CCB including low-temperature reduction disintegration property,reduction swelling property and reduction property were detected.Based on all above,the effects of charging ratio of VTM-CCB on melting-dripping property of comprehensive burden,the content of V,Cr in dropped iron and the recovery of V,Cr were studied,and finally the reasonable scope of VTM-CCB charging ratio was determined.Several conclusions were obtained as follows:(1)During the hot-pressing process of VTM-CCB,when in low temperature zone(100?300?),hot-pressing temperature was the most significant factor,and then,respectively,coal size,VTM size and carbon ratio,and the best level of the four factors were hot-pressing temperature 300?,coal size-200 mesh,VTM size-200 mesh and carbon ratio 1.6.When in high temperature zone(300?500?),VTM size was the most significant factor,and then,respectively,hot-pressing temperature coal size and carbon ratio,and the best level of the four factors were hot-pressing temperature 450? coal size-150 mesh,VTM size-150 mesh and carbon ratio 1.8.Finally,considering the actual situation,the parameters of the prepararation of VTM-CCB were hot-pressing temperature 200 ?,carbon ratio 1.6,coal size-200 mesh,VTM size-200 mesh.The compressive strength of VTM-CCB pressed under the finally parameters was 1071N/per.(2)The best heat treating parameters of VTM-CCB are treating temperature 650?,treating time 5h.After the heat treating,the compressive strength of VTM-CCB was up to 2620N/per,and its weight loss ratio was up to 7.76%.(3)VTM-CCB had great metallurgical properties.The index of low-temperature reduction disintegration(RDI+3.15)was over 99%and index of reduction swelling(RSI)is-2.16%.And its reducibility was much better than oxide pellet.In all,VTM-CCB metallurgical properties was better than tanditional burden of BF,and it was in line with the quality requirements of blast furnace iron-making burdens.(4)The melting-dripping experiment results show,with the charging ratio of VTM-CCB increased,the softening temperature range widened from 146.1 ? to 266.1 ?,the melting temperature range narrowed first and then widened,and when the charging ratio was 20%,the melting temperature range became narrowest(129.1 ?).With the charging ratio of VTM-CCB increased,the permeability improved obviously,the dripping ratio increased first then decreased,and it get maximal value(72.4%)when VTM-CCB charging ratio was 10%.With VTM-CCB charging ratio increased,both V,Cr in the initial iron and the recovery rate of V,Cr tended to increasing then decreasing,and the content of V,Cr respectively reached the maximum 0.101%and 0.137%when the charging ratio was 25%,also the recovery of V,Cr respectively reached the maximum 14.55%and 28.16%when the charging ratio was 25%.Above all,the most reasonable range of VTM-CCB charging ratio in comprehensive burden should be controlled within 10%?25%,and the best charging ratio was 20%.