Effect Of Barun Concentrate Ratio On Reduction Expansion Of Iron Ore Pellets

Bayan obo west ore,also called Barun ore,is a composite ore.It is composed of iron,tombarthite,niobium and other minerals.The fine ore has small particle size,high grade and low price,so it is suitable for the production of pellets.However,its composition is complex,and the contents of K,Na,F,CaO and Mg O are high.The K,Na and F will seriously worsen the expansion rate of pellets.This paper uses the Qunei mine and the Barun mine as raw materials for iron,and changes the proportion of Barun mine.Using oxidation and calcination to prepare pellets.The CO is used as reduction gas.The study is about the effects of different proportions of Barun mine on the expansion properties of iron ore pellets during step-by-step reduction.Specific research results are as were studied with CO as reduction gas.The results are follows:The raw pellets with different proportions of Barun mine were oxidized and roasted,and then the compressive strength of the finished pellets was tested.It was found that the compressive strength of the finished pellets firstly increased and then decreased with the increase of the proportion of Barun mine.When the proportion of Barun mine was 40%,the compressive strength reached the maximum of 4602.2 N/P.In the reduction stage of Fe₂O₃?Fe₃O₄,the ratio of Barun mine increases from 0%to100%,and the volume expansion rates of pellets are 10.53%,1.35%,6.20%,11.28%,19.07%,23.06%,respectively.Compared with the pellets with the ratio of 20%and 40%of Barun mine,the reduction expansion rate of the pellets with 100%of Qunei mine is higher.For the ore in the 100%zone,the porosity of the finished ball is large,and the ability to resist the expansion stress caused by the crystal transformation is poor,resulting in a high expansion rate.With the addition of Barun mine,CaO+Mg O and K₂O+Na₂O content in slag phase increased,melting point of slag phase continued to decrease,and the pores of pellets firstly decreased and then increased.This will result in a continuous increase in the reduction expansion rate of pellets.In the Fe₃O₄?FeO reduction stage,the ratio of Barun mine increases from 0%to100%,and the volume expansion rate of pellets increases from 3.63%to 20.06%.The reason is that part of CaO,FeO and SiO₂can combine to form calcium iron olivine and Fe₂SiO₄in the reduction process,which has poor reductivity,resulting in the difference of internal and external reduction rate and resulting in uneven expansion of pellets.With the increase of the proportion of Barun mine,the CaO content in pellets gradually increases,and the production of calcium-iron olivine in the reduction process also gradually increases,.Then the volume expansion rate gradually increases.In the FeO?Fereduction stage,when the ratio of Barun mine increases from 0%to100%,the volume expansion rates of pellets increase from-5.77%to 24.39%.In other words,with the increase of the proportion of Barun mine,the volume expansion rate of pellets gradually increases.The reason is that,with the increase of the proportion of Barun mine,the contents of K,Na and Cain the pellets gradually increase,which will cause lattice defects in the pellets,resulting in faster growth rate of iron whiskers and accelerate expansion of the pellets volume.