As a main charging burden of blast furnace(BF)ironmaking process,pellets play an important role in ironmaking process.However,compared with sinters,there are some inevitable disadvantages for traditional acid pellets,...As a main charging burden of blast furnace(BF)ironmaking process,pellets play an important role in ironmaking process.However,compared with sinters,there are some inevitable disadvantages for traditional acid pellets,e.g.,reduction swell,low melting temperature.Therefore,the fluxed-pellets have been applied in BF,especially MgO-fluxed pellets.In the present study,the effects of category and content of MgO bearing additive on the compressive strength(CS),reduction swelling index(RSI),reduction disintegration index(RDI)and melting-dripping properties of the pellets were investigated.Minerals composition,pore distribution and microstructure of MgO-flux pellets were studied by X-ray powder diffraction(XRD),mercury intrusion method and scanning electron microscopy(SEM),respectively.The results show that the light burned magnesite(LBM)is more suitable MgO bearing additive for fluxed-pellets.With increasing LBM content from 0 to 2.0%,the CS decreases from 3066 to 2689 N,RSI decreases from 16.43%to 9.97%and RDI decreases from 19.2%to 12.99%.The most appropriate MgO bearing additive content in the fluxed-pellets is 2.0%according to principal component analysis(PCA).展开更多
As a main charging form of BF （blast furnace）, pellets play an important role in blast furnace process. However, comparing with sinters, pellets have many disadvantages, such as reduction swelling, low softening and...As a main charging form of BF （blast furnace）, pellets play an important role in blast furnace process. However, comparing with sinters, pellets have many disadvantages, such as reduction swelling, low softening and melting temperature and so on. Therefore, the flux pellets have been applied in blast furnace widely, especially MgO containing pellets. The light burned magnesite is applied as MgO containing additive in pellet production. The char- acters of light burned magnesite are explored. Meanwhile, the effects of it on low-temperature metallurgical proper-ties are investigated such as low-temperature reduction degradation index （RDI）, compressive strength （CS） and the reduction swelling index （RSI）. The light burned magnesite calcined at 850 ℃ manifests better grindability, larger specific surface area, and higher hydration activity. It is found that the addition of light burned magnesite can im- prove low-temperature metallurgical properties （RDI, RSI） of the pellets. With the increase of light burned magne-site in pellets, the RSI and RDI decrease gradually; when the proportion of light burned magnesite does not exceed 2.0% in pellets, the CS decreases slightly, but it still surnasses 2689 N. which can still meet the demand of BF.展开更多
MgO-containing flux may have a series of effects on the quality of sinter and performances of the blast furnace.Thus,the fundamental mechanism of the effects of MgO on the sinter strength was investigated.Both the che...MgO-containing flux may have a series of effects on the quality of sinter and performances of the blast furnace.Thus,the fundamental mechanism of the effects of MgO on the sinter strength was investigated.Both the chemical reagent and industrial flux were used for preparing the specimens.The experimental results show that the sinter strength decreases with MgO addition.There are three reasons for it.The first reason is diffusion rate.Almost all of the CaO may react with Fe2O3 and generate CaO Fe2O3,but most of MgO cannot react with Fe2O3,and it still remains in the state of original minerals.The diffusion rate of MgO in iron oxide is only 17.51μm/min in 30 min.The second reason is the fluidity and ability to generate liquid phase.In the case of Fe2O3 mixed with CaO,there is some liquid phase formed above 1200℃,while in the case of Fe2O3 mixed with MgO,even at 1200 and 1220℃,there is still no liquid phase.The third reason is self-strength.In the case of industrial flux,the compression strength of the specimens made of Fe2O3 and limestone is 0.52 and 0.71 kN at 1150 and 1180℃,respectively,while that of the specimens made of Fe2O3 and magnesite is 0.48 and 0.56 kN,respectively.Therefore,the fundamental mechanism of the effects of MgO additive on sinter strength can be better understood based on the diffusion rate of MgO in iron oxides,the fluidity of liquid phase,and the self-strength of bonding phase.展开更多
基金Projects(51874080,51604069)supported by the National Natural Science Foundation of ChinaProject(N162504004)supported by the Fundamental Research Funds for the Central Universities,China
文摘As a main charging burden of blast furnace(BF)ironmaking process,pellets play an important role in ironmaking process.However,compared with sinters,there are some inevitable disadvantages for traditional acid pellets,e.g.,reduction swell,low melting temperature.Therefore,the fluxed-pellets have been applied in BF,especially MgO-fluxed pellets.In the present study,the effects of category and content of MgO bearing additive on the compressive strength(CS),reduction swelling index(RSI),reduction disintegration index(RDI)and melting-dripping properties of the pellets were investigated.Minerals composition,pore distribution and microstructure of MgO-flux pellets were studied by X-ray powder diffraction(XRD),mercury intrusion method and scanning electron microscopy(SEM),respectively.The results show that the light burned magnesite(LBM)is more suitable MgO bearing additive for fluxed-pellets.With increasing LBM content from 0 to 2.0%,the CS decreases from 3066 to 2689 N,RSI decreases from 16.43%to 9.97%and RDI decreases from 19.2%to 12.99%.The most appropriate MgO bearing additive content in the fluxed-pellets is 2.0%according to principal component analysis(PCA).
基金Item Sponsored by National Natural Science Foundation of China ( 51074206 , 51074040 )
文摘As a main charging form of BF （blast furnace）, pellets play an important role in blast furnace process. However, comparing with sinters, pellets have many disadvantages, such as reduction swelling, low softening and melting temperature and so on. Therefore, the flux pellets have been applied in blast furnace widely, especially MgO containing pellets. The light burned magnesite is applied as MgO containing additive in pellet production. The char- acters of light burned magnesite are explored. Meanwhile, the effects of it on low-temperature metallurgical proper-ties are investigated such as low-temperature reduction degradation index （RDI）, compressive strength （CS） and the reduction swelling index （RSI）. The light burned magnesite calcined at 850 ℃ manifests better grindability, larger specific surface area, and higher hydration activity. It is found that the addition of light burned magnesite can im- prove low-temperature metallurgical properties （RDI, RSI） of the pellets. With the increase of light burned magne-site in pellets, the RSI and RDI decrease gradually; when the proportion of light burned magnesite does not exceed 2.0% in pellets, the CS decreases slightly, but it still surnasses 2689 N. which can still meet the demand of BF.
基金The authors wish to acknowledge the contributions of associates and colleagues at Northeastern University of China and Meishan Steel of China.Also,the financial supports of the National Natural Science Foundation of China(NSFC 51874080,51774071,and 51604069)are appreciated very much.
文摘MgO-containing flux may have a series of effects on the quality of sinter and performances of the blast furnace.Thus,the fundamental mechanism of the effects of MgO on the sinter strength was investigated.Both the chemical reagent and industrial flux were used for preparing the specimens.The experimental results show that the sinter strength decreases with MgO addition.There are three reasons for it.The first reason is diffusion rate.Almost all of the CaO may react with Fe2O3 and generate CaO Fe2O3,but most of MgO cannot react with Fe2O3,and it still remains in the state of original minerals.The diffusion rate of MgO in iron oxide is only 17.51μm/min in 30 min.The second reason is the fluidity and ability to generate liquid phase.In the case of Fe2O3 mixed with CaO,there is some liquid phase formed above 1200℃,while in the case of Fe2O3 mixed with MgO,even at 1200 and 1220℃,there is still no liquid phase.The third reason is self-strength.In the case of industrial flux,the compression strength of the specimens made of Fe2O3 and limestone is 0.52 and 0.71 kN at 1150 and 1180℃,respectively,while that of the specimens made of Fe2O3 and magnesite is 0.48 and 0.56 kN,respectively.Therefore,the fundamental mechanism of the effects of MgO additive on sinter strength can be better understood based on the diffusion rate of MgO in iron oxides,the fluidity of liquid phase,and the self-strength of bonding phase.
