Effect Of Iron Ore Powder On Pyrolysis Polycondensation Process Of Iron Coke And Its Structure And Properties

With the rapid development of steel manufacture,the shortage of high quality coking coal,the serious emission of greenhouse gas and pollution gas,and the limit of blast furnace production efficiency are becoming more and more serious.Iron coke,a kind of high reactive coke which can reduce the coke ratio of blast furnace and further improve the efficiency of blast furnace is put forward,the quality of iron coke directly affects the stability of blast furnace.Coking process parameters will have a certain impact on the performance of iron coke,however,the current research mainly focuses on the analysis of macro factors and the effect of iron minerals on the pyrolysis behavior of coke is not deeply studied.Because the pyrolysis process of coking coal plays a decisive role in the quality of coke,thus,the influence of the content and type of iron ore powder on the carbonization process of gas coal was studied in this paper by means of the differential thermogravimetric analyzer,high temperature microscope and other characterization methods such as XRD and SEM.The changes of structure and properties of iron coke were clarified.The following conclusions were obtained:First of all,the order of interaction effect from strong to weak is NF、EX、GW.The fitting results of kinetic model show that the QM pyrolysis process is mainly controlled by chemical reaction in the early stage and mainly by controlled diffusion in the later stage,Compared with the pyrolysis mechanism of pulverized QM alone,the reaction mechanism of mixed sample changed obviously after adding iron ore powder.The second stage and fourth stage of pulverized coal changed from chemical reaction control to diffusion control,and the average apparent activation energy of pyrolysis was30-35kJ/mol after the addition of iron ore powder.It is smaller than the average apparent activation energy of 46.81kJ/mol when the coal is pyrolyzed alone,and there is a kinetic compensation effect between the activation energy and the preexponential factor.Secondly,the high temperature hot table test shows that with the increase of carbonation temperature,the volume of iron coke increases first and then decreases.The shrinkage degree is 10%>20%>30%.The shrinkage degree of the three kinds of iron coke samples is similar to that of QM when the proportion of mineral powder is 10%.However,the shrinkage degree of iron coke decreased obviously when the proportion of ore powder was 20%and 30%.The order of shrinkage is QM>GW>NF>EX.The results of XRD and SEM show that the change of iron ore powder in the carbonization process of iron coke is similar,the iron minerals in iron coke are mainly Fe₂O₃ when the temperature is 400℃,and then change into Fe₃O₄ at 800℃,when the temperature is1100℃,the iron minerals in iron coke are Fe.Finally,the structure and properties of iron coke are studied from several angles.The results show that the porosity of EX iron coke is less and the matrix is tight.The GW and NF iron coke matrix is loose and the matrix particles are easy to fall off.The results of XRD study show that the graphitization degree of iron coke gradually decreased with the increase of the proportion of the mineral.When the ratio of iron ore powder was the same,the graphitization degree of EX iron coke is higher and the graphitization degree of GW iron coke and NF iron coke is similar and lower than that of EX iron coke.The results of compressive strength and drum strength show that the order of compressive strength of iron coke is QM>EX>GW>NF,the order of drum strength of iron coke is QM>EX>NF>GW when the ratio of iron ore powder is the same,and with the increase of the ratio of iron ore powder,the strength sequence remained the same.Except for GW-10%iron coke,the initial reaction temperature of other iron coke decreased when compared to QM coke.Same addition ratio,when adding different iron ore powder,the order of the starting temperature of gasification reaction of iron coke is about GW>EX>NF.