Investigation On The Fluidity Of SFCA Bonding Phase And Its Effect On The Strength Of Sinter

In sintering process,Fe2O3 and CaO can genenrate liquid.The fluidity of liquid is one of important indexes for sintering strength.In order to improve the quality of sinter and blast furnace performances,the effects of composition of calcium ferrite bonding phase(SFCA)on the fluidity are experimental investigated combined with phase diagrams analysis.Then,sinter pot test and pilot trial are carried out in an ironmaking plant of China.The main findings in this thesis could be summarized as follows:1.Flouidity of SFCA bonding phaseBased on phase diagrams,we analyzed different systems and different components of binding phase which includes Fe2O3-CaO-SiO2?Fe2O3-CaO-Al2O3?Fe2O3-CaO-MgO.We found that the fluidity index of liquid phase is proportional to the mount of liquid at a certain temperature,and the relationship between the liquid phase and the melting point is inversely proportional.The results showed that:a)When the content of SiO2 is 5%,the peak value of fluidity index is 14.5 and the content of CaO in the calcium ferrite bonded phase is 25?30%;When the content of SiO2 is 10%,the crest value of fluidity index is 20.8 and the content of CaO in the calcium ferrite bonded phase is 25%;b)When CaO/SiO2 = 2,the maximum value of fluidity index is 13.2 and the content of CaO in the calcium ferrite bonded phase is 23.3%;c)When the content of Al2O3 is 2%,the peak value of fluidity index is 5.5 and the content of CaO in the calcium ferrite bonded phase is 20?22%;When the content of Al2O3 is 5%,the crest value of fluidity index is 5.8 and the content of CaO in the calcium ferrite bonded phaseis 21?23%.d)When the content of MgO is 2%,the peak value of fluidity index is 5.8 and the content of CaO in the calcium ferrite bonded phase is 20?22%;When the content of MgO is 5%,the peak value of fluidity index is 4.8 and the content of CaO in the calcium ferrite bonded phase is 21?23%;2.Sinter pot testA series of sinter pot tests are carried out to investigate the effects of MgO content in sintering materials on the strength of sinter.The experimental results showed that:a)We made the content of MgO increased from 0.9%to 2.0%.When we add dolomite into the raw material as flux,the utilization coefficient of sinter pot decreased from 2.063 t/m2·h to 1.772 t/m2·h and the tumbler index of sinter reduced from 68.47%to 68.47%.When we add magnesite stone into the raw material as flux the utilization coefficient of sinter pot decreased from 2.063 t/m2·h to 1.693 t/m2 h and the tumbler index of sinter reduced from 68.47%to 66.53%.b)We made the content of MgO increased from 0.9%to 2.0%.When we add dolomite into the raw material as flux,the RDI+3.15 of sinter increased from 61.41%to 68.12%.When we add magnesite stone into the raw material as flux the RDI+3.15 of sinter increased from 61.41%to 68.53%.The RDI+3.15 of sinter can be improved 3-4%after we fine grinding the flux of MgO.That is to say the RDI+3.15 of sinter when the content of MgO is 1.6%is the same than that when the content of MgO is 2.0%.What's more,flux was distributed more uniform and the segregation was decreased in the sinter after fine grinding.Then the sinter strength was improved.3.Pilot trialA pilot trial is carried out in an ironmaking plant of China.In the pilot trial,magnesium flux is reduced in blast furnace(BF)burden.a)The result shows that the slag in NO.4 and NO.5 blast furnace was changed obviously.The lowest content of MgO in slag is about 7.0%and the maximum of Al2O3 content is more than 16%.NO.4 and NO.5 blast furnace ran stability and these two BF technical and economic indexes were obviously improved.The utilization coefficient of NO.5 BF increased from 2.225 t/m.·d to 2.275 t/m3·d and PCR was raised 4 kg/t.The utilization coefficient of NO.4 BF increased from 2.309t/m3·d to 2.405t/m3 ·d and PCR was raised 6.6 kg/t.b)The industrial test results that 1)The sinter:MgO in sinter reduced from 1.79%to 1.67%but the drum strength was increased from 78.30%to 81.56%.And the RDI+3.15 of sinter also increased from 65.21%to 68.05%.2)slag:MgO in slag reduced from 7.95%to 7.34%and MgO/Al2O3 reduced from 0.51 to 0.47.3)The blast furnace:Coke rate reduced from 363.39 kg/tHM to 357.82 kg/tHM and coal ratio was increased from131.78 kg/tHM to 136.40 kg/tHM and fuel ratio was reduced from 495.23 kg/tHM to 494.18 kg/tHM.