| During the vanadium titano-magnetite smelting in the 2500m3 blast furnace of Chengsteel company,the problems that include the anomalous flows of slag-iron,difficulty in separation of slag and iron,great fluctuation of furnace condition,frequent channeling,hanging and slip,and high energy consumption existed.Therefore,the improvement for the quality of vanadium titano-magnetite sinter,the reasonable burden structure of blast furnace,and the feasibility of MgO injection were investigated.The results are as follows.The vanadium titano-magnetite in Chengde area is a medium-titanium ore with low iron,low silicon and high aluminum.The main mineral components are magnetite(93%),hematite(3%)and gangue(2%).In the magnetite,the uivospinel(2FeO·TiO2)content is about 22.4%,the w(TiO2)in uivospinel accounts for 82%?89%of total w(TiO2),and the MgO and Al2O3 mostly exist as minerals.The SiO2 exists in the form of gangue minerals such as titanopyroxene,plagioclase and titanium amphibole,which is not good for sintering.In addition,the vanadium titano-magnetite has some characteristics.Firstly,the granularity is well-distributed,the average particle size is 75.11?m and-200 mesh is about 60%.Secondly,its specific surface areas is small,the hydrophilicity,ballability,thermal stability and shock resistance all are poor.Thirdly,its melting point is 1425?,assimilation temperature is 1365?,liquidity fluidity index is 3 and binding phase strength is 2000N,therefore,the sitnering basic property is bad.During the sintering process of vanadium titano-magnetite,the vertical sintering velocity is slow,exhaust gas temperature and burning loss rate are low.In the vanadium titano-magnetite sinter,the total liquid phase is 20%?30%,which is less about 10%?15%than the conventional one,the perovskite content is 12%?20%,calcium ferrite just is 6%?8%,and the porosity rate is about 45%,as a result,the drum index is low and the RDI+3.15 just is 27.29%.The vanadium titano-magnetite is complementary to four common iron ore powders and two foreign ores.Therefore,reasonable mixing can meet the requirement for improving the quality of sinter.Testing and analyzing of the sintering reveal that the 20%Brazilian ore powder,30%Australian ore powder and 50%vanadium titano-magnetite should be selected as reasonable blending in Chengsteel company.With increasing of carbon content,the RDI+3.15 increases while RI decreases,and the TI is the highest when the carbon content is 4.2%.When the basicity is 2.1,the RDI+3.15 has a minimum and RI is relatively low.In addition,the TI significantly decreases with increasing of w(MgO).When the w(MgO)is 4%,RDI+3.15 has a maximum.However,the relationship between RI and w(MgO)is not obvious.Therefore,the optimum sintering process parameters include carbon content of 3.8%,basicity of 2.4,w(MgO)of 3.6%.When the vanadium titano-magnetite blends with ordinary ore,with increasing of vanadium titano-magnetite,the TI and RDI+3.15 both decrease while RI and ?T increase,the softening and melting properties become bad.With an increase in the content of carbon,the TI,RD/+3.15 and ?T increase while RI decreases.With increasing of the basicity,the TI and RI increase,and RDI+3.15 has a minimum when the basicity is 2.1.The TI has a maximum when the w(MgO)/w(Al2O3)is 1.05.The RDI+3.15 and RI both increase while ?T decreases with the increasing of w(MgO)/w(Al2O3).With increasing of w(SiO2)/w(TiO2),the TI and ?T increase while T10%and T40%decrease,the RDI+3.15 and RI of sinter are improved.In addition,the TI and RI both have maximum when the moisture of mixture ore is 8.11%.With the increasing of moisture,RDI+3.15 increases.The ?T has no change when the moisture is 7.3%?8.11%,and it has a maximum when the moisture is 8.72%.By comprehensively considering,2#scheme should be chosen,and the optimum sintering process parameters selected include carbon content of 3.81%,basicity of 2.3,w(MgO)/wAl2O3)of 1.05,w(SiO2)/w(TiO2)of 5.66%,moisture of 8.11%.The optimum FeO content of sinter could be 9.16%.It is proposed that the P is an important parameter to control the FeO content during sintering process.The FeO content of mixture ore can be controlled in 11.8%-12.59%by proportioning ore,as a result,the FeO content of sinter reaches the requirement of 9.16%.Moreover,when the FeO content of mixture ore is less than 11.8%,the FeO content of sinter will be 8%.After spraying CaCl2 into the sinter of Chengsteel company,the pressure difference in the lump zone decreases.The softening and melting testing indicates the S goes up significantly with increasing of basicity,MgO,TiO2,FeO and ?T.However,the effect of RI on S is not obvious.The sintering ore(2#),pellet(2-1#),pellet(2-2#)and lump ore(2)should be in a ratio of 67:20:7:6.The soft-melting zone will widen with the increasing of CRI.Moreover,the softening and melting properties of burden become bad when the CRI is more than 30%.And the S rises with the increasing of coke(<5mm).Therefore,it is necessary to increase the CSR of coke for the improvement of permeability in the low part of blast furnace.The w(MgO)of blast furnace slag in Chengde company is required about 12.2%.To date,the way of adding MgO in Chengsteel company will result in the deterioration of the primary slag properties and the permeability in cohesive zone.Therefore,the new technology of injecting MgO into the tuyere is put forward.The result reveals that,when the velocity of conveying medium is 5.9m/s,the mixture of pulverized coal and magnesite can be conveyed smoothly.Adding MgO into the pulverized coal will make the combustion more fully,consequently,the combustion rate of pulverized coal further increases.Because the MgO injected forms Mg2+,O2-in the slag,the distribution of Mg2+ will quickly reach equilibrium with the high temperature and the strong stirring of air flow,which completely meet the requirement of slagging and desulfurization.In addition,with the increasing of w(MgO),the heat income in hearth slight decreases while the heat expenditure increases,heat loss decreases from 5.55%to 5.32%,but the heat income of hearth still meet the smelting requirement of blast furnace. |
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