Research On Reaction Swelling Properties Of Iron Oxides By Hydrogen

The reduction of pellets with higher swelling rate has effected the charging ratio,to explore the malignant swelling during the process of iron ore pellets reduction,this paper using first principles calculation software,calculated cell volume of the products during the reduction process of iron oxides,and compared volume change of reduction products;used the pure gas H₂ to reduce the reagent Fe₂O₃ specimens,and the equipment of PCY-G dilatometer with high temperature was used to test swelling online,by contrasting images of the appearance and microstructure of reduction products under the condition of different reduction temperature,reduction time and roasting temperature,explained the reason for the difference with the swelling of reduction reaction.The results showed that the difference of cell types and structure properties of iron oxide is great,under the condition of temperature 0k and cells packing closely,with the reduction of oxygen,the volume content from Fe₂O₃ to Fe₃O₄ decreases by 2.02%,volume from Fe₃O₄ to FeO decreases by 19.78%,volume from FeO into Fe decreases by 43.77%.With the increase of reduction temperature,the times that reduction reaction reached maximum swelling gradually shorten,the data of maximum swelling of reduction products tends to increase firstly and then decrease,specimens swell largest when the reduction temperature is 800?,the largest swelling value is up to 668um,and swelling rate is 3.06%;then swelling value decreases sharply with the temperature of 900?,a large number of iron phase generated early is the main cause of shrinkage during the swelling.As the reduction time going on,swelling curve of the rapidly rising stage represented massive formation of Fe₃O₄,when curve has slowed,it is speculated that the outer Fe₃O₄ is deoxidized to FeO firstly,swelling curve reaching peak represented formation stage of FeO,as well as Fe phase begins to generate;In the later reduction,the large generating of Fe phase causes volume shrink.With the increase of roasting temperature,under the same conditions of reduction temperature,the time reaching maximum swelling amount makes no difference,the data of maximum swelling of reduction products tends to decrease firstly and then increase,specimens swell least when the reduction temperature is 1200?,the least swelling value is up to 85um,and swelling rate is 0.4%;then swelling value increases sharply with the temperature of 1250?,it is the speculated that holes are the main cause of swelling defference of roasting products.