Experimental Study On Fine Grinding Of MgO Flux And Reduction Mechanism Of SFC

In recent years,great changes have taken place in the raw materials of iron making in China’s steel companies.With the increase of foreign ore consumption,and the content of Al2O3 in slag remains high,resulting in difficulties in smelting.In order to cope with the negative effect of high Al2O3 slag,the main measures of steel companies are to add MgO flux in sintering production,which can ensure the demand of blast furnace slag for MgO,However,the increase of MgO content in the sinter also brings a lot of negative effects.Therefore,in order to give full play to the positive energy of MgO and avoid its side effects,it is necessary to ensure that the MgO added into the sinter is fully mineralized,that is,to give full play to the positive energy effect of MgO on the premise of less MgO.Based on this,this paper studies the effect of MgO flux finely grinding and to enhance the mineralization effect of MgO in the sintering process,and investigates the influence law and mechanism of the fine grinding ratio of MgO flux on the strength of sinter and sinter after low temperature reduction.Then,under the premise of certain MgO content,the sintering cup experiment is carried out with different proportions of the fine grinding MgO flux,the effect of the fine grinding MgO on sintering production was verified.The positive effect of MgO on RDI of sinter was brought into full play to solve the technical problem of steel companies to produce sinter with low MgO and good RDI performance.On this basis,the reduction test of SFC(a simplified SFCA without Al2O3)was carried out,and the equilibrium products and reduction mechanism under different reduction potentials were determined.It enriches and perfects the theory of calcium ferrite,and provides an important theoretical basis for the future research on the mechanism of MgO effect on the reduction performance of SFCA.The main conclusions of this paper are as follows.(1)The results show that with the increase of MgO flux fine grinding ratio from 0%to 100%,the strength of composite calcium ferrite increases in different proportions.The proportion of fine grinding of MgO flux increases from 0%to 100%;the strength of Fe2O3-MgO binary system increases from 2820N to 3750N,and the strength after reduction increases from 1250N to 3030N.The results show that the strength of Fe2O3-MgO-CaO ternary system increases from 2320N to 3523N,the reduced strength increases from 2010N to 3130N,the strength of Fe2O3-MgO-CaO-SiO2 increases from 1189N to 2656N,and the reduced strength increases from 1990N to 3025N,In addition,in the low temperature reduction process,the reduction of Fe2O3 to Fe3O4 and the lattice transformation produced in the process are inhibited,so as to improve the strength of sinter after low temperature reduction.(2)With the increase of MgO flux fine grinding ratio,sintering process parameters and sinter low temperature reduction pulverization index are improved.When the ratio of MgO flux increases from 0%to 50%,the vertical sintering speed of sinter increases from 25.66 mm·min-1 to 31.1mm·min-1,the utilization coefficient increases from 2.52t·m-2·h-1 to 2.94t·m-2·h-1.the drum index increases from 74.93%to 76.13%.RDI-3.15 decreases from 16.25%to 11.78%.When the fine grinding ratio of MgO flux is more than 50%,the effect on sintering process parameters and sinter quality becomes slower.Based on this,it is suggested that 50%flux containing MgO should be modified in actual sintering production.(3)Through the reduction experiments of SFC in different reducing atmospheres,the equilibrium products of 20%,40%,60%,80%and 90%CO were confirmed,a)When CO=20%and 40%,most of Fe2O3 in SFC was reduced to FeO,and the equilibrium phases were FeO,CaO·Fe2O3 and CaO·SiO2.b)When CO=60%,CaO·Fe2O3 was reduced to FeO and 2CaO·Fe2O3,The equilibrium phases are FeO,2CaO·Fe2O3 and CaO·SiO2.c)When CO=80%and 90%,FeO is reduced to Fe,and 2CaO·Fe2O3 is reduced to FeO and CaO,and the equilibrium phases are Fe,Cao and CaO·SiO2.Based on this,the reduction path of SFC is plotted,as shown in Fig.4.21.To sum up,this paper studies the mineralization effect of fine grinding modification on MgO flux and the reduction mechanism of SFC.That is to say,the influence law and mechanism of fine grinding and modification ratio of MgO flux on sinter strength and the low-temperature reduction pulverization are mastered,and the reduction mechanism and reduction path of SFC are clarified.It provides an important theoretical basis for improving sintering process index and sinter metallurgical properties,reducing energy consumption and CO2 emission in blast furnace smelting process.