Effect Of Alkalinity On Strength And Reduction Swelling Properties Of Bayan Obo Iron Concentrate Briquetting

Due to the presence of harmful elements such as potassium,sodium and fluorine in the Bayan Obo area of Baotou,the pellets are abnormally expanded or even malignant under the reducing atmosphere of the blast furnace,which seriously affects the production of the blast furnace.The using of the Baiyun Obo iron ore in the blast furnace has being affected.That has restricted the development of Baotou Iron and Steel Enterprises.Therefore,in order to improve the reduction and expansion properties of pellets,this paper adjusts the alkalinity of pellets by adding pure reagent CaO,and studies which are the most suitable alkalinity and the effect of CaO on the reduction and expansion of the pellets of Bayan Obo concentrate.The mechanism provides a theoretical basis for improving the reduction and expansion properties of pellets produced from Bayan Obo mine.In order to explore the effect of alkalinity on the reduction and expansion properties of the compacted ore,this paper chooses to add pure reagent CaO to adjust the alkalinity to six test points of 0.2,0.4,0.6,0.8,1.0,and 1.2,using different high temperature hot and heavy atmosphere furnaces.The alkalinity of the agglomerated ore was calcined at 1280°C,and the change law of the phase structure of different alkalizes ore gangue was analyzed by ZEISS metallographic microscope.The comprehensive strength of the pressed ore was tested and the alkalinity against comprehensive strength was investigated.Influence the law.Studies have shown that as the alkalinity increases with the increase of CaO content,the comprehensive strength of the compacted ore first increases and then decreases.The increasing of the liquid phase causes the porosity to decrease and the pressure of the compaction to increase,but the excessive liquid phase will Destroying the overall structure of hematite,the strength of the slag phase is lower than that of hematite,and the strength of the compaction is gradually reduced.The calcined sample was reduced at 900°C by using a reduction furnace.The volume of the sample before and after the original test was tested by water immersion method,and the reduction expansion index was calculated.The changing law of the reduction expansion ratio of the sub-mine with the alkalinity was examined..Studies have shown that the pressure group has the highest reduction expansion rate when the alkalinity is 0.8,and the expansion value exceeds69.85%,which is a malignant expansion.It is observed by scanning electron microscopy that the alkalinity of the pressure agglomerate increases to 0.8.A large number of elongated iron whiskers are generated,causing malignant expansion of the compacted ore.Due to the increase of CaO content,the amount of Ca²⁺dissolved in the FeO lattice is maximized,the FeO lattice will be distorted,the channel of ion diffusion will be increased,and the growth of iron whiskers could be accelerated.As the alkalinity increases further,the iron whiskers gradually will decrease or even disappear in the future.