Fundamental Research On Direct Reduction Of Iron Concentrate With Biomass

The direct reduction iron is an indispensable raw material in the short process of steelmaking using the electric furnace.It can significantly promote the low-carbon,green and sustainable development of iron and steel industry.In this paper,the biomass,a common and renewable material,was used as the reducing agent for the direct reduction of iron concentrate.Moreover,the gas escape was strictly limited by using the sealed gas plug,enhancing the coupling pyrolysis effect between the iron concentrate and biomass.The main conclusions are as follows:The thermodynamic conditions of biomass pyrolysis and reduction of iron concentrate were identified.Results showed that the oxidation reaction of biomass occurred at 200℃～500℃and promoted the temperature of the material layer.The pyrolysis products below 642℃were prone to the methanation reaction and generated methane（CH₄）which triggered the reduction reaction.However,the reduction reaction at 642℃～818℃was mainly induced by carbon monoxide（CO）.Above the temperature of818℃,the reduction ability of hydrogen（H₂）was stronger than CO and the water gas reaction of biomass carbon contributed to the rapid reduction.The reduction conditions of biomass in iron concentrate were optimized.When the external water content was 10%,the ratio of carbon and iron（C/Fe）（mol）was 0.6 with the reduction temperature of 1040℃,the reduction time of 40 min,and the metallization rate of sponge iron being96.87%.The behavior and mechanism of the low temperature rapid reduction of iron concentrate with biomass were revealed.In the reduction process with the increased temperature,the sealed gas plug restricted the gas escape,resulting in an increased air pressure greater than 16 k Pa in the early stage of reduction.The high molecular carbon hydroxide compounds with the active functional group X[R]_nK structure were produced by the biomass pyrolysis and adsorbed and condensed on the surface of iron concentrate,leading to a coupled pyrolysis process and significantly delaying the volatilization of biomass.The chemically absorbed biomass carbon and tar played significant roles in the induction and the catalytic reduction with the whisker width being 4～10μm at a low temperature.