Fundamental Research On Softening And Shrinkage Behavior Of Wustite In Cohesive Zone Of Blast Furnace

Based on the background of blast furnace ironmaking,this paper studies the interaction between the reduction of nucleus and the slag formation in the soft-melt zone.The traditional softening-melting experiment focuses on the description of transient temperature changes,ignoring the change in the shape and thickness of the soft-melt tape and the softening and melting characteristics of the soft-melt tape as well as internal reactions and interactions under complex loading conditions.In this work,an innovative index shrinkage rate?SR?was proposed to directly evaluate the softening shrinkage behavior in the simulated cohesive zone.It helps to more intuitively describe the change law of the thickness of the cohesive zone,and provides a certain guiding significance for the stable and smooth operation of the blast furnace.As the temperature rises,this index is used to elucidate the effect of H₂ and CO and their mixed gases on the softening and shrinkage of FeO and multicomponent slag systems,and between the reduction and slag forming reactions involving wustite?FeO?transient interactions.The results are summarized as follows:?1?Effect of H₂,CO,and H₂+CO mixture gas on FeO.The slagging reaction caused by the thermal effect causes the material layer to shrink at a relatively low temperature.The shrinkage of the material layer is only affected by the temperature,FeO itself begins to soften,so the slag forming reaction dominates;at 900?.,the reducing gas CO,FeO is introduced.Reducing to metal iron,filling material layer pores,shrinkage intensified,so the reduction reaction dominated,slag reaction is weaker than the reduction reaction;With the temperature rises,to 1000?,enter the third stage,the reduction effect weakened,The SR value decreases,the thermal effect leads to shrinkage,and all slag formation reactions dominate;at the fourth stage,the temperature rises further and the shrinkage curve continues to rise.At this time,the temperature is called the driving force of softening and shrinkage,so the slag formation reaction caused by thermal effects.Dominated.?2?The results show that the thermally induced slagging reaction causes the packed bed to shrink at the lower temperature,and the SR increases by twice at most when the minerals with low melting temperature are generated by adding CaO or SiO2,whereas it reduces to 0.13%/K due to the formation of FeO·MgO solid solution.As soon as CO or H₂ is introduced,the reduction reaction takes over the driving force for the shrink between 900? to 1000?.After that,the dominating factors for the further shrinkage include slagging,reduction,or both,and vary with respect to the additions as well as the temperature.?3?The FeO-X-Y ternary mixture will form the complex phases,FeO-CaO-SiO₂mainly forms hedenbergite,FeO-CaO-Al₂O₃ mainly forms brownmillerite,FeO-SiO₂-MgO mainly forms olivine,and FeO-MgO-Al₂O₃ mainly forms ceylonite.Because of its lower melting point,CaFeSi₂O₆?hedenbergite?will drip with the dripping of metallic iron.CaFeAl₂O₄?brownmillerite?will dribble with the dripping of metallic iron although its melting point is higher.The MgFe?SiO₄??olivine?has a very high melting point and is not easily melted,thus hindering shrinkage of the packed bed and no dripping;Mg?Al,Fe?₂O₄?ceylonite?is a spinel phase with a high melting point,which prevents the packed bed from shrinkage and eventually does not drip.For the FeO-X-Y ternary mixture softening and melting curve,SR under the H₂ atmosphere condition generally falls behind CO atmosphere condition in the second stage.In the third stage,only SR of FeO-MgO-Al₂O₃ under the H₂ atmosphere is greater than the other.With the temperature further rises,in the fourth stage,the SR under the H₂atmosphere condition increases sharply.Although the SR under the CO atmosphere also increases,the increase is smaller than the H₂ atmosphere,and the SR under the H₂atmosphere is greater than that under the CO atmosphere.