Study On Thermodynamics Of FeO_x Deoxidization, Fe Recycled From Steel Slag And Properties Of Residue

The steel slag contains4~35%FeO_x, approximately about3~10%of Fe. The emission ofsteel slag is over100million tons every year in china, and a great number of Fe is dischargedas steel slag wastage without recycled. At the same time, because of the high levels of FeO_x,especially RO phase, leads to low cementitious activity of steel slag, confine the reasonableresource utilization of steel slag. This paper proposes that utilizing the characteristics ofsteelworks’ waste materials of coal gangue and low-quality fly ash which contain thedeoxidization component and the ability to adjust chemical composition of steel slag. Andusing them as adjustments in simulative on-line reconstruction process, deoxidize FeO_xandrecycle Fe from steel slag at high temperature, form “simulated slag” to improve cementitiousactivity of residue. This study is of great significance to achieve high value-added utilizationof steel slag.This paper study the process of deoxidizing the FeO_xof Thermodynamics in hightemperatures, analysis the process, sequence and results of deoxidizing of FeO_xcombiningwith online slagging process, and confirm the added amount of deoxidizing component. Onthis basis, choosing three different steel slag, respectively is hot stuffy technology processedhigh alkalinity and high alumina steel slag, high alkalinity and low aluminum steel slag, anddrum technology processed high alkalinity and low aluminum steel slag. Then addingdifferent kinds of deoxidizing component, experiment the deoxidization of FeO_xat hightemperatures in the laboratory, study on results of reduction of iron from steel slag andproperties of residue in the condition of sufficient deoxidizing component. Finally, using thesteelworks’ waste materials of low-quality fly ash and coal gangue, for suitable onlineprocessing, studied the composition and structure of the steel slag, the types of adjustingmaterials (chemical composition) and dosage effect on deoxidization of reconstruction.The results showed that:(1) The deoxidization reaction of FeO_xby C is more likely tohappen during the onl-ine processing of molten steel slag, and the deoxidization reaction ofthree kinds of iron oxide can be conducted simultaneously. The FeO_xdeoxidized reaction byC is more likely to occur during the on-line slagging of molten steel slag, and the deoxidizedreactions of three kinds of FeO_xare simultaneous. Only when deoxidizing component is sufficient, the FeO_xin the steel slag can all be deoxidized to Fe, which can eliminate thenegative influence of the RO to cementitious activity.(2) Under the condition ofdeoxidization component sufficiently, the Fe recovery rate of three kinds of steel slag (M, Sand B) can reach90%, the grade of coarse iron can reach75~87%. After the water quenched,the residue were formed to "simulated slag" structure that include vitreous mainly, and28dactivity index is20%greater than the original steel slag respectively.(3) When the content ofdeoxidization components in the adjusting material can deoxidize the FeO_xof steel slagexactly in the condition of being melted, the recovery rate of Fe is the highest. When the lowaluminum steel slag as S and B steel slag are reconstructed, their chemical composition aresimilar to slag. And when the high aluminum steel slag as M steel slag is reconstructed, itschemical composition is similar to high alumina cement. After the reconstruction, thecementitious activity of low aluminum steel slag is higher.(4) Combining the on-line processof reconstruction and considering the recovery rate of Fe and cementitious activity of residue,the added amount of low-quality fly ash used as deoxidization and reconstruction componentof M steel slag should be20%, and iron reduction rate can reach82.0%, the28d cementitiousactivity index of residue is84.0%; the added amount of coal gangue of S steel slag should be25.7%, and iron reduction rate can reach96.0%, the28d cementitious activity index ofresidue is84.4%; the added amount of coal gangue of B steel slag should be30%, and ironreduction rate can reach92.8%, the28d cementitious activity index of residue is87.5%.The results laid a theoretical foundation for deoxidization of FeO_xin steel slag, provide atheoretical basis and technical support forFe recoveryed from steel slag while improvingcementitious activity of residue, promote high value-added utilization of steel slag effectively.