| The resources of vanadium-titanium magnetite concentrates(VTC) in China are rich which rank third in exploitation of national iron ore, and mainly located in Pan-Xi region. Pan Steel mainly used VTC as sintering raw material. In order to make fully use of its own iron resources, lower production costs and improve economic benefits of Vanadium products, Pan Steel intends to improve VTC amount in sintering material. However, increase of VTC proportion is disadvantage for sinter. Therefore, it’s necessary to study the properties of VTC sintering, find out the effect of VTC proportion on sinter performance, and obtain strengthening methods of VTC sintering on that basis.Study on VTC suitable parameters and sintering properties shows that, with the increase of VTC from0%to55%, the suitable granulation moistures increase from8.50%to8.25%and coke proportions reduce from5.0%to4.0%, the sintering velocity reduce from23.05mm/min to18.21mm/min, specific productivity decrease from1.55t/(m2·h) to1.21t/(m2·h), yield reduce from73.18%to69.04%, tumbler index lessen from62.93%to56.80%. Reduction degree of sinter decrease, melting and dripting zone widen lead that slag and iron is hard to separate. In a word, sinter qualities and metallurgical properties become worse.The VTC granulation and mineralization properties are studied which proclaimsthe mechanisms of VTC affecting sintering:The results of VTC granulation properties show that, VTC has coarse particles, smooth surface and flat shape, which results in its bad granulation properties. With increasing VTC proportion, average particles of mixture decrease from4.89mm to2.60mm, thin size-fraction below lmm increase from0.05%to6.00%, roughness of granulation ball increase, and form factor of particles become smaller, permeability decrease from1.43J.P.U to1.22J.P.U, which lead sintering velocity lower.The results of VTC mineralization show that, calcium ferrite generate maximum at1300℃in VTC sintering, with temp. rising, perovskite increase and calcium ferrite lessen. So VTC sinter suitable temp. range is fairly narrow, and the optimal temperature is about1300℃. TiO2, MgO and Al2O3in VTC can improve melting point, lead that liquid phase formations of mixture become harder with the increase of VTC.The results of mineral composition and microstructure show that, with the increase of VTC, the content of perovskite gradually increase, calcium ferrite decrease, the amount of dendrites and scattered bone structure of hematite increase, and the shape of calcium ferrite from the needle-like gradually develop into the column-like and granulous-like. Liquid phase is hard to form, fragile perovskite increase, and needle-like calcium ferrite which has highly intensity lessen, these lead that tumbler index and yield reduce with the increase of VTC.The results of strengthening methods for VTC sintering show that, wet grinding and high-pressure roll press precondition VTC can reduce particle size, increase surface activity. The average particle and form factor of particles are improved which leads to a better permeability. Compare with untreated material, permeability increase from1.22J.P.U to1.47J.P.U, sintering velocity improve from18.22mm/min to21.15mm/min when used twice of high-pressure roll press precondition. Rise burntlime amount or use higher content of CaO can gradually reduce content of below3mm particle, improve average particle and permeability. Compare with burntlime No.1, permeability increase from1.22J.P.U to1.40J.P.U, sintering velocity improve from18.22mm/min to21.44mm/min with use of burntlime NO.4. Addition complex binder can reduce content of below3mm particle, improve average particle and permeability. Compare with no binder, permeability increase from1.22J.P.U to1.41J.P.U, sintering velocity improve from18.22mm/min to20.94mm/min. pregranulation can insure normal iron ore generating fairly calcium ferrite, get suitable microstrure. Compare with untreated material, tumbler index improve from56.80%to59.54%when basicity of VTC pregranulation part was2.03. Substitute limonite with lower melting point for Australia ore with higher melting point can facilitate the generation of liquid phase. Tumbler index improve from56.80%to59.51%when Australia ore was totally replaced by FMG ore. |
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