Migration of sulfur in raw materials of blast furnace ironmaking
The emissions of SO2 in the steel industry account for 13.9%of the total industrial emissions in the coun-try,and the blast furnace ironmaking process is a crucial stage in sulfur emissions during steel production.With increasing environmental regulations,reducing the content of sulfides in blast furnace gas has become particularly important.In order to elucidate the evolution mechanism of sulfides in blast furnace raw materials during the smelt-ing process,chemical analysis and X-ray Photoelectron Spectroscopy(XPS)to characterize the forms and content of sulfur in the actual raw materials used in Baosteel's blast furnace were employed.Subsequently,the blast furnace sul-fur load was calculated.Furthermore,a thermodynamic calculation method was used to study the distribution mecha-nism of sulfur in the slag-iron-gas three-phase system in different zones of the blast furnace.The results indicate that the primary source of sulfur in blast furnace raw materials is coke,accounting for 72.3%of the total sulfur input,fol-lowed by pulverized coal at 19.7%,while the combined sulfur content in iron-bearing materials(sinter,pellets,and lump ore)is less than 10%.Sulfur in coke and pulverized coal primarily exists in the forms of organic sulfur such as sulfoxides,sulfones,thiophenes,and inorganic sulfur such as sulfides and sulfate sulfur.Additionally,the sulfur content in coke is higher than that in pulverized coal.The sulfur in the lump zone blast furnace gas mainly originates from the pyrolysis of inorganic sulfur in the raw materials,gaseous H2S and COS generated from the reaction between the burden and the reducing atmosphere,and the remaining COS after the absorption of gaseous sulfides produced in the lower region of the cohesive zone.Additionally,the COS content in blast furnace gas is typically higher than that of H2S.In the cohesive zone of the blast furnace,the raw materials are conducive to sulfur absorp-tion,and sulfur primarily exists in the newly formed primary slag.In the hearth region,sulfur mainly exist in the slag,followed by molten iron,and lastly in the gas phase.With increasing temperature,the desulfurization capacity of slag improves,leading to more sulfur transferring from molten iron to slag.
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