Interface Characteristics And Wetting Behavior Of Iron-Slag-Carbon System In Blast Furnace

With the continuous advancement of the national carbon neutral strategy,the blast furnace ironmaking process is facing great challenges in low-carbon development.With the increasing pressure of low-carbon development and the continuous consumption of high-quality raw materials and fuel resources,the internal environment of blast furnaces is in a stage of constant change.Maintaining good air and liquid permeability is the key to efficient production and operation of blast furnaces.However,the requirements of raw materials,fuels and low-carbon development have brought unprecedented challenges to the realization of low-carbon and efficient operation of blast furnaces.Therefore,it is urgent to deeply understand the key factors affecting the gas and liquid permeability inside the blast furnace,and to clarify the influence of slag-ironcarbon multiphase interaction behavior and interfacial wetting characteristics on the gas and liquid permeability of blast furnaces.This paper reveals the interaction mechanism of iron-carbon,slag-carbon and slag-iron-carbon multiphase synergistic interface from the microscopic scale,and improves the interaction behavior theory of slag-iron-carbon inside the blast furnace.The law of non-reactive wetting evolution of molten iron on graphite surface was studied by molecular dynamics simulation.The results show that the hydrophilicity of molten iron on the graphite basal crystal orientation surface is obviously better than that on the graphite prism crystal orientation surface.The basal crystal orientation surface of graphite has a stronger interaction with iron,which can promote the melting of molten iron at a temperature below the melting point of 1600K.The increase of temperature can improve the hydrophilicity between molten iron and graphite.The degree of wrinkling of graphite also affects the wettability of molten iron on graphite.The smaller the degree of wrinkle,the closer to the perfect graphite structure,and the better the wettability.Through microscopic analysis,it is found that the change of the number of contact atoms at the interface does not directly affect the change of wettability,and the change of local structure in the iron phase is the direct cause of affecting the wettability of the interface.The dissolution and wetting behavior of molten iron on graphite surface was studied by reactive molecular dynamics simulation.The dissolution and wetting process was deeply analyzed from the aspects of microstructure of molten iron,carbon structure destruction mechanism and carbon atom migration mechanism.The reactive wetting behavior of molten iron on graphite surfaces with different crystal orientations is obviously different,and the dissolution behaviors all occur along with the wetting reaction moment.However,the wettability of the graphite prism plane crystal orientation interface to molten iron is better than that of the graphite basal crystal orientation surface.The key link in the wet iron-graphite reaction wetting process is the exfoliation and dissolution process of carbon atoms.The exfoliation methods of carbon atoms in the graphite basal crystal orientation model can be divided into three types:dissociation of carbon atoms at graphite defects,exfoliation of chain-like unstable carbon structures,and orderly dissociation of carbon atoms at the iron-graphite interface.However,in the graphite prism plane crystal orientation model,the carbon stripping method is simpler,and more is the orderly dissociation of carbon atoms from the graphite carbon ring structure through interface contact.Through microstructure analysis,it is found that,affected by the graphite structure,the iron atoms at the interface will present a chain-like and graphite-like six-membered ring structure.Adjusting the interface contact structure between iron and carbonaceous materials is an effective way to improve wettability.The influence of basicity,MgO/Al2O3 ratio and FeO content changes on the wetting behavior of slag on the surface of carbonaceous materials was explored by experimental methods.The results show that the slag without iron oxide does not react chemically with the graphite substrate,and the wetting process is only non-reactive wetting.The increase of basicity and MgO/Al2O3 ratio in the slag will improve the surface tension of the slag on the graphite surface.The FeOcontaining slag will undergo a reduction reaction with the substrate,and the generated Fe will stay at the interface.By improving the properties of the slaggraphite interface,the effect of improving wettability can be achieved.At the same time,it is found that although the slag will show hydrophobicity on the surface of graphite and coke,the wettability of coke to slag is better than that of graphite.The main reason is that coke contains more ash which is similar to the composition of slag,and the migration of aluminosilicate leads to a good interaction between them.There are more pores in coke,and the slag can diffuse into the surface voids of coke within a certain range of surface tension,thereby achieving the effect of improving wettability.The first-principles molecular dynamics method was used to explore the microscopic interaction mechanism between slag and graphite-carbon interface.For the first time,the behavior of slag-carbon interaction was explored from the atomic and electronic scales.Results have shown that different atoms in slag have different effects in the slag-carbon interaction process.In the graphite prism surface model,the atoms in the slag that mainly interact with graphite are Si,Al,and O atoms.Under the action of multiple active sites on the graphite prism surface,three tetrahedral structures of SiO3C,AlO3C and AlO2C2 will be formed at the interface,thereby improving the interface interaction of slag-graphite.In the graphite plane crystal orientation model,there is only a weak van der Waals interaction between the slag and graphite,and the interaction strength between the two is low.The increase of basicity can obviously increase the interaction energy between slag and graphite prism surface,and reduce its interaction energy with graphite plane.For the first time,the multiphase synergistic wetting mechanism of slagliquid iron on the surface of graphite substrate was explored experimentally.Combining molecular dynamics and meta-dynamic methods,the influence of microscopic properties was deeply explored.It was found that the wetting process of slag-iron-graphite multiphase synergistic reaction is a process accompanied by multiple influencing factors.The wettability of molten iron is mainly affected by its own initial carbon content,while slag is affected by the initial carbon content of molten iron and its own content.The initial carbon content of molten iron will not only affect the iron-carbon wetting mechanism by affecting the carburizing reaction process of molten iron,but also affect the mechanism modification process of the slag-carbon interface by affecting the reaction of FeO in the slag,thereby affecting the slag-iron-carbon Synergistic reaction wetting process.Meta-dynamic results found that the ability of dissolved carbon to reduce molten iron oxides is significantly stronger than that of solid graphitic carbon,proving that the behavior of carbon between iron and slag is the key factor for the synergistic wetting of slag-iron-carbon.On the basis of previous studies,this paper studied the synergistic wetting behavior of slag-iron-carbon multiphase.The interfacial interaction mechanism of molten iron-graphite,slag-graphite and slag-iron-carbon multiphase synergistic wetting has been studied in depth.The evolution mechanism of the micro structure of the slag-iron-carbon interface was revealed from the atomic scale,and the mechanism affecting the interface wetting behavior was comprehensively characterized.It provides a theoretical basis for the reasonable control of air and liquid permeability inside the blast furnace.