Molecular Dynamics Study Of Sodium-catalyzed Coke Dissolution-loss Reaction Mechanism

Coke in a blast furnace can react with CO₂ in a dissolution loss reaction to produce the reducing gas CO,while making itself less strong.The alkali metals present in the blast furnace catalyze this reaction.Previous research on alkali metal-catalyzed coke dissolution loss has focused on describing the macroscopic kinetics of the reaction,the mechanism and microscopic nature of this reaction is rarely addressed at the molecular level.Taking Pingyao coke as a sample,the alkali reaction of sodium vapor adsorption on coke is carried out,and the subsequent coke dissolution loss reaction experiment is carried out by using the product.The process of sodium-catalyzed coke dissolution loss reaction is simulated by Reax FF based on molecular dynamics method.SEM and EDS results show that sodium vapor can effectively corrode the surface of the coke,leaving microscopic pores on the surface,and these parts corroded by sodium vapor become the gasification active sites.The results of XRD,XPS and Raman indicate that sodium inhibits the graphitization of the solid phase products in the coke dissolution loss reaction.Reax FF molecular dynamics simulations yield phenomena consistent with the experiment.Through a self-written C++program,the complete pathway of the CO generation and carbon structure reconstruction is obtained statistically from the simulation trajectories.Simulation results show that sodium atoms spontaneously adsorb on the defects of carbon layer formed by the dissolution loss reaction,which on the one hand prevents the merging and growth of the carbon layers and inhibits the formation of ordered carbon structures;on the other hand,it promotes the oxidation of the defective carbon layer structures to form more CO molecules.In addition,the results of density functional theory also confirm that the rate-controlling step of the dissolution loss reaction,the activation energy of carbon layer oxidation,is greatly reduced by sodium atom in the gas phase to increase the formation rate of CO molecule in the initial stage.The mechanism of coke dissolution loss reaction catalyzed by sodium is confirmed by a combination of traditional experiments and theoretical calculations,which provided a theoretical basis and new research ideas for people to study the influence of alkali metal elements in blast furnace on the physicochemical properties of coke.Figure 41;Table 6;Reference 70...