Study On The Surface Morphology And The Growth Of Iron Crystal In The Fluidized Reduction Process

Because of the good reduction kinetics condition,directly using the mineral powder and not depending on coke,the fluidization of ironmaking process has been attracted much attention.However,the powder bonding leads to the defluidization behavior in the fluidization of ironmaking process,which has been the key to hinder its further development.This paper focuses on three aspects: the surface of iron ore crystal,the bonding mechanism and inhibition method.In this paper,through using the density functional theory?DFT?and transition state principle,the energy and band change of model that is doped Mg²⁺,Ca²⁺ or carbon-black adheresion is gotten through molecular dynamics software.X ray diffraction,scanning electron microscope and energy spectrum analysis are used to analyze samples gotten on the different reduction conditions?different reduction temperature,reducing atmosphere,adding alkaline oxide and carbon-black adheresion?,the variation law of surface morphology on iron ore powder is gotten.Through this research,the following conclusions are drown:1 Through molecular dynamics simulation,the dissolution energy of Ca²⁺is bigger than Mg²⁺,which showed that Ca²⁺is harder than Mg²⁺to dissolve in Fe_xO crystal;the energy barrier for doped ions Mg²⁺ migrating to the vacancy is the least,then Ca²⁺,and Fe²+ is bigger than Ca²⁺ and Mg²⁺;through forming magnesium iron complex or calcium iron composite,iron whiskers can be inhibited,and the inhibitory effect of Mg²⁺ is better.After carbon-black adheresion treatment,the difference of the adsorption energy of CO on C-FeO all planes is little,and through the density of states and energy band analysis,the adsorption and Covalent bond of C-O are stable,so the crystal orientation of iron formation is inhibited.At the same time the Fe-C bond is formed,which can hinder the further reduction.2 With carbon pretreated and adding alkaline oxides.After adding MgO and CaO,the phenomenon that alkaline oxide can form a composite compound with iron oxide in the reduction process is found through XRD;through scanning electron microscopy and energy spectrum analysis,the phenomenon that the length of iron whisker length becomes shorter,the diameter becomes thick,the composite compound will be formed around the iron whisker head to hinder iron whisker active substances is found.After carbon-black adheresion treatment.the phenomenon that the length of ironwhisker length becomes shorter,the diameter becomes thick is found,and the existence of Fe-C is found through XRD,which can be used to hinder the active material of iron whiskers.3 Through comparing the SEM-EDS results of samples in different temperature reduction,the whisker of powder is short at 600?,and through XRD and EDS,the surface of powder is covered by Fe3_C;the morphology of the whisker becomes longer and thinner at 700?;the morphology of the whisker becomes shorter and thick at 800 and 900?.The reasons is analyzed: carbon deposition behavior occurred easily at600?,carbon will react with iron oxide to product Fe3 C,which will hinder the further reduction of powder,and the chemical reaction rate is slow at the low temperature,so the samples are not bonded into blocks;at 700? the chemical reaction rate is low,Fe generated can spread quickly to become slender;compare 800?,900? and 700?,with the increase of temperature,the chemical reaction rate becomes faster,and the effect of temperature on the diffusion of Fe is little,so the morphology of the whiske becomes shorter and thick.4 Through comparing the SEM-EDS and XRD results of samples in different atmospheres reduction,except 50%CO+50%N₂,the samples at other atmospheres can be completely reduced to metal Fe.Compare 80%CO+20%N₂ with 50%CO+50%N₂samples,with the decrease of the concentration of reducing atmosphere?CO?,the morphology of the whiske becomes shorter and thick.80%H₂+20%N₂ and50%H₂+50%N₂ samples,the morphology of the whiske becomes shorter and thick,and there are nodular iron.Compared CO with mixed gas,it is found that the morphology of the whiske at mixed gas is shorter and thicker.