The Evolution Of Carbon Structure And Gasification Reactivity During Petroleum Coke Gasification/Catalytic Gasification

With the increasing demand for light oil in industrial production,as a by-product of petroleum processing,the production of petroleum coke also increases.How to use petroleum coke cleanly and efficiently has become an urgent problem to be solved.Gasification technology can effectively solve the emission of harmful gases such as sulfur dioxide in the process of petroleum coke utilization,and produce the hydrogen required by petrochemical enterprises.It is considered to be a clean and efficient method to treat petroleum coke.However,the dense structure,underdeveloped pore structure,low ash,and volatile content of the petroleum coke,resulting in low gasification activity,which greatly increases the difficulty of gasification utilization.Alkali metal salt catalyst（K₂CO₃）has good catalytic activity and can be used as a catalyst for petroleum coke,coal,and other carbon materials.Therefore,using alkali metal salt catalysts to improve the gasification reactivity of petroleum coke has important practical significance.Study on the correlation of the structure and reactivity of petroleum coke,especially the gasification reactivity after the addition of catalyst,is the key to the development of gasification technology suitable for petroleum coke,while limited research focues on this.In this paper,the thermogravimetric analyzer was used to study the CO₂ non-isothermal gasification/catalytic gasification reaction characteristics of Zhenhai petroleum coke,Chambroad petroleum coke,and Shengli petroleum coke.The residual coke with different carbon conversion was prepared by a fixed-bed tube furnace,and the evolution of coke structure during gasification reaction was studied.The main research contents include:（1）Non-isothermal CO₂ gasification characteristics of Zhenhai petroleum coke（ZH）,Chambroad petroleum coke（CB）,and Shengli petroleum coke（SL）were studied by the thermogravimetric analyzer.The structure of three petroleum cokes was analyzed by BET,XRD,and Raman,and the correlation between petroleum coke structure and the gasification reactivity was discussed.The results show that the gasification reactivity of three petroleum cokes can be described by the specific gasification rate,and the order of gasification activity is SL>CB>ZH.The analysis of petroleum coke structure showed that the gasification reactivity of petroleum coke correlated well with the order degree of carbon structure and the CO₂ chemisorption,but had a poor correlation with the specific surface area.The amount of CO₂ chemisorption and the ordering degree of carbon structure of petroleum coke can effectively reflect the difficulty of adsorption with reaction gas and chemical bond breaking in the gasification of petroleum coke,so it can be used as an effective parameter to evaluate the gasification reactivity.The activation energies of SL,CB,and ZH are 216 k J/mol,245 k J/mol,and 280 k J/mol,respectively.（2）The non-isothermal catalytic gasification characteristics of petroleum coke were studied by the thermogravimetric analyzer,and the gasification residual coke with different carbon conversion was prepared by a tube furnace.The coke structure was analyzed by BET,XRD,and Raman to explore the influence of coke structure on the gasification reactivity.The results show that the addition of K₂CO₃ catalyst can significantly improve the gasification reactivity of petroleum coke.With the addition of the catalyst blending ratio,the catalytic gasification reactivity of petroleum coke increases continuously.When the catalyst loading was greater than 5 mmol K,the catalyst would be saturated,and the gasification reactivity of petroleum coke was limited when continue to increase catalyst loading,but no inhibition of gasification reaction occurred.It is also found that the addition of catalyst is also an important factor affecting the reactivity of petroleum coke gasification.Compared with the dry mixing method,the impregnation method can greatly improve the gasification activity of petroleum coke,indicating that the contact distance between the catalyst and petroleum coke is also an important factor affecting the catalytic gasification of petroleum coke.Due to the etching effect of K₂CO₃,the structure of petroleum coke was destroyed,and the graphitization degree of carbon during gasification reaction was increased.It was found that the change of petroleum coke structure during the reaction process was not the key factor affecting the reactivity of petroleum coke non-isothermal gasification.（3）Thermogravimetric analyzer was used to study the catalytic gasification reaction characteristics of Zhenhai petroleum coke during the isothermal gasification,and the gasification residual coke with different carbon conversion was prepared by a tube furnace.The coke structure of residual coke was analyzed by BET,XRD,and Raman,and the evolution law of petroleum coke structure and reactivity at the constant temperature stage was explored.The change of coke structure during the isothermal gasification/catalytic gasification,such as the decrease of L_c and the increase of specific surface area,has little effect on the gasification reactivity of residual coke.At the same time,it is also found that the specific surface area of residual coke increases first and then decreases in the isothermal gasification,which may be the reason why the rate increases first and then decreases in the isothermal gasification.