Study On In-situ Catalytic Gasification Reactivity Of Sodium-rich Liquefaction Residue And Synergistic Eeffect Of Sodium And Iron

The sodium-rich coal has the characteristics of low mineral content and high reactivity,and is considered as a suitable raw material for direct coal liquefaction technology.After the direct coal liquefaction process,the inherent sodium in the sodium-rich coal is enriched in the coal direct liquefaction residue,and the iron-based catalyst added during the direct liquefaction also remains in the liquefaction residue.In order to make better use of the direct liquefaction residue of sodium-rich coal and provide theoretical guidance for its clean and effective use,the catalytic effect and structural change of intrinsic sodium on the gasification reactivity of the direct liquefaction residue of sodium-rich coal were studied in detail in this work.On the basis of previous research,the synergistic effect of sodium and iron was studied by adding iron-based catalyst,revealing the ability of multi-component to fix sodium at high temperature and the microscopic mechanism of action.First,the sodium-rich liquefaction residue was pretreated to obtain raw coal liquefaction residue,demineralized coal liquefaction residue,and impregnated coal liquefaction residue.The TG-MS was used to determine the gasification reactivity and gas release law of three kinds of liquefaction residues at 900 ^oC,1000 ^oC and 1100 ^oC.The experiment results showed that the intrinsic sodium had obvious catalytic effect on the gasification of raw coal direct liquefaction residue.The kinetic analysis showed that the level of linear correlation coefficient obtained by homogeneous model and shrinking core model was closely related to gasification temperature and residue type.The reaction activation energy was calculated according to the model,indicating that the intrinsic sodium could reduce the activation energy required for the gasification of coal direct liquefaction slag and improve the gasification efficiency.Then the gasification residues and gasification coke of raw coal liquefaction residues at different gasification stages of three kinds of liquefaction residues under the same reaction conditions were obtained by being carried out in a fixed-bed reactor.The structure evolution and sodium catalytic behavior of raw coal liquefaction residue during CO₂ gasification were studied in detail through SEM,XRD and N₂ physical adsorption.The results showed that the sodium expanded the pore structure of coal direct liquefaction residue during gasification,However,XRD analysis did not find obvious sodium crystalline compounds,due to that most sodium substances volatilized at high temperature,The Raman intensity increased with the gasification process.In addition,the release rate of sodium species is closely related to the gasification time.Finally,the iron-based catalyst was loaded on the raw coal liquefaction residue by impregnation method,and its gasification reactivity and reaction kinetics were studied by TG.The results showed that adding a small amount of Fe could produce synergy with the inherent sodium in the sodium-rich liquefaction residue and further accelerate the reaction.Compared with the separate gasification of sodium-rich liquefaction residue,the gasification activation energy was reduced after adding iron-based catalyst,and there was a synergistic effect between sodium and iron.The gasification coke was also obtained in a fixed-bed reactor under the same reaction conditions.The interaction of sodium and iron during the gasification process was studied through FTIR,XRD and other characterization methods.The results showed that the participation of Fe prevented the reaction between Na and Si,Al from forming insoluble substances without catalytic activity,which better guaranteed the catalytic activity of Na.