Study Of Gangue Composition On Expansion Performance Of CO Reduced Iron Oxide

Reducing expansibility of iron ore pellets is the main factor affecting their extensive application in blast furnace ironmaking.Pellets in such as CaO and MgO style,SiO₂,Al₂O₃,gangue is one of the important factors affecting the reduction swelling,as proved the influence of the gangue of iron oxide reduction process step by step,adopt the method of on-line analysis,this paper studies the Fe₂O₃ layering sample by CO reduction of different stage,CaO,MgO style and SiO₂ on its expansion ratio,in order to determine the appropriate proportion of gangue in the pellet production to provide data support and theoretical guidance,at the same time for rich oxidation pellets in the reduction in our country inflation theory provides a new research idea.The specific conclusions are as follows:After roasting at 1250?for 30 minutes,all the Fe₃O₄ in the sample raw materials were converted into Fe₂O₃,and the hematite with better crystal contact was obtained.After oxidized roasting,there was no obvious difference in macroscopic morphology between the layup samples of MgO,CaO and SiO₂ pure reagents with a ratio of 2%.In terms of micro morphology,the sample with 2%MgO was added to generate relatively regular and smooth holes with a certain amount of liquid around it.There were a few liquid phase and large holes in the sample with 2%CaO.There were a few slag phases and dense and irregular pores in the sample with 2%SiO₂ added.For the Fe₂O₃ layer-bar with 0%,1%,2%and 3%MgO pure reagent respectively,with the increase of MgO ratio,Fe₂O₃?Fe₃O₄ reduction stage,due to the formation of magnesia-containing magnetite during oxidizing baking,the lattice structure of magnetite is stabilized,the linear expansion rate of sample drops from 2.99%to2.41%;In Fe₃O₄?FeO reduction stage,Mg²⁺replaces Fe²⁺of FeO in the reduction process to form a solid solution,which can stabilize the Floss lattice and increase the linear expansion rate of the sample from-0.62%to 0.05%.In the FeO?Fe reduction stage,because the magnesium containing phase has been transformed into MgO independent of the iron phase to form a liquid phase,the formation of Fe is hindered,the contraction of the original sample is inhibited,and the linear expansion rate of the sample increases from-2.23%to-1.46%.To match into 0%,1%,2%,3%respectively CaO reagent Fe₂O₃ layering,with the increase of the ratio of CaO,Fe₂O₃ and Fe₃O₄ reduction stage,because of the addition of CaO in oxidizing roasting can form acid calcium and iron,acid calcium and iron for the low melting point compound promotes the increasing of the liquid phase,even hinder the hematite crystal,the specimen linear expansion rate fell to2.99%from 2.06%.In Fe₃O₄?FeO stage,because Ca²⁺in CaO will replace Fe²⁺or fill Fe²⁺vacancy in FeO,the radius of Ca²⁺is greater than the radius of Fe²⁺,so the lattice constant and cell volume increase,and the linear expansion rate of the sample increases from-0.62%to 0.20%.At the FeO?Fe stage,the addition of CaO increased the reduction velocity difference in all directions of the crystals during the reduction process,resulting in crystal cracking and expansion,and the linear expansion rate of the sample increased from-2.23%to-1.02%.For the Fe₂O₃ layer-bar with 0%,2%,4%and 6%SiO₂ pure reagent respectively,with the increase of SiO₂ ratio,in the reduction stage of Fe₂O₃?Fe₃O₄,the resistance stress of hematite to crystal transformation was enhanced due to the slag phase generated during oxidizing baking,and the linear expansion rate of the sample decreased from 2.99%to 2.22%.In the Fe₃O₄?FeO reduction stage,the slag phase continued to hinder the transformation from hematite to Fusite,and the linear expansion rate of the sample increased from 0.62%to 0.09%.In the FeO?Fe stage,the linear expansion rate of the sample decreased from-2.23%to-3.24%because the slag phase bonding could effectively inhibit expansion.