Studies On Solution Reaction Characteristics And Microstructure Of Coke In Hydrogen-rich Atmosphere

For the requirement of"doul carbon"strategy,hydrogen rich blast furnace smelting is an important way to achieve green and low-carbon development.Especially in the situation of shortage of high-quality coking coal resources,the development of low carbon coke raw materials used in hydrogen rich blast furnace has become a common key technology in the industry.Because the high reactivity coke can reduce the temperature of the hot reserve area of the blast furnace,and improve the working efficiency of the blast furnace body,and then improve the utilization rate of carbon,reduce the coke-iron ratio in the blast furnace,so it has been widely concerned by scholars globally.In view of adding H₂into a hydrogen-rich blast furnace will produce water vapor in the high temperature reduction zone of the blast furnace,which will affect the dissolution loss reaction of coke in the blast furnace.Therefore,it is of great practical significance to study the dissolution loss characteristics of coke in hydrogen rich blast furnace.In this thesis the influence of calcium addition on the dissolution loss of coke was studied by adding CaO into coking coal to produce highly reactive coke.The multi-functional high-temperature thermal reaction device was used to study the dissolution loss reaction characteristics and microstructure evolution rule of coke with different reactivity in hydrogen-rich atmosphere.The research work showed strong innovation.The main research contents and results are as follows:（1）At a reaction temperature of 1100℃,the effects of Ca addition on the thermal properties and microstrength of coke were explored,and the microstructure of coke before and after Ca addition was analyzed.With the increase of Ca addition,the reactivity of coke increases,and the strength after reaction decreases,but the microstrength and structural strength of coke are less affected;After Ca addition the（002）diffraction peak intensity and the number of crystal stacked layers（N）are reduced,and the addition of Ca can significantly improve the reactivity of coke.（2）In order to simulate the reaction behavior of coke in blast furnace,the influence of different heating rate and Ca addition amount on the non-isothermal solution loss reaction behavior of coke and the solution loss reaction kinetics were investigated.With the increase of heating rate,the maximum reaction rate increases gradually.The initial reaction temperature and maximum reaction rate of the solution loss reaction between coke and CO₂decreased with the increase of Ca addition.The activation energy decreased from 140.71 kJ·mol^-1to 124.30 kJ·mol^-1and decreased by 13.08kJ·mol^-1when the Ca content was 0.6%.In addition,the kinetic model of the solution loss reaction between coke and CO₂with CaO is consistent with the non-reactive core-shrinking model,but the reaction mechanism function changes f（α）=3（1-α）^2/3to f（α）=2（1-α）^1/2.（3）The influence of H₂O content change and reaction temperature on the dissolution loss rate of coke and reaction rate was analyzed.The results show that with the increase of H₂O content,the reactivity of coke increases,and the strength of coke after reaction decreases;with the increase of reaction temperature,the dissolution loss rate of coke increases;in the CO₂-H₂O mixed atmosphere,coke dissolution reaction produces synergistic effect,and the synergistic effect of high-reactivity coke is more obvious than that of conventional coke;the increase of reaction temperature and H₂O volume fraction promotes the dissolution reaction of coke,the effective diffusion coefficient D_eand the interface reaction rate constant k₊gradually increase,and the interface of high-reactivity coke The reaction control zone is larger than that of conventional coke.（4）Using XRD,Raman,MIP and SEM to analyze the evolution behavior of coke microstructure in the dissolution reaction process of highly reactive coke and CO₂-H₂O mixed atmosphere.XRD analysis shows that the increase of H₂O content in the reaction atmosphere promotes the ordering of coke microcrystalline structure and intensifies the degree of graphitization of carbon structure;Raman spectrum analysis shows that the addition of Ca in highly reactive coke increases The degree of defect and disorder increases the reactivity of coke,promotes the occurrence of dissolution reaction,and then consumes more amorphous carbon structures,so that more amorphous carbon structures are converted into ordered microcrystalline structures;at the same time,pressure Mercury and SEM showed that adding H₂O to CO₂gas can diffuse into the coke to promote the formation of small pores.This effect is more obvious on highly reactive coke.