Study On Catalytic Pyrolysis Of Coal Under Mixed Atmosphere

In view of the characteristics of rich coal and lack of oil in China,it is one of the main ways to improve the conversion rate and tar yield by using a variety of coal pyrolysis techniques.Coal pyrolysis technology is the most economical and efficient technology to produce liquid fuel.And also,it accords with the development requirement of"rich coal and low oil and less gas"structure.The improvement of more gas and tar quality is the focus of research at present.Therefore,the effects of N₂ atmosphere and mixed atmosphere on coal pyrolysis in fixed bed were studied in this paper.On this basis,the catalyst was added in order to improve the yield of tar and to increase the reliability of coal catalytic pyrolysis process.In this paper,Tangshan bituminous coal was used in the experiment.And that,based on the study of the final temperature,reaction pressure and pyrolysis gas velocity on coal pyrolysis in N₂ atmosphere,further studies on the pyrolysis behavior of coal in mixed atmosphere were conducted.In addition,four iron-based catalysts?FeCl₃?Fe₂O₃-Cl?Fe₂O₃/SiO₂?Fe₂O₃/?-Al₂O₃?were prepared by impregnation method and precipitation method.The components of pyrolysis gas phase products were analyzed online by gas chromatography,and the yields of tar and water were calculated by Karl Fischer micrometer.Finally,the coal coke weighing in the reaction tube was collected to calculate the pyrolysis weight loss rate.Through the analysis of the coal pyrolysis products in fixed bed,we can get the following main conclusions:?1?The weight loss rate of coal pyrolysis in mixed gas atmosphere was higher than that in N₂ atmosphere.The weight loss rate increased with the increase of pressure,and it reached the maximum value of 43%at 800?and 3MPa.?2?In the process of coal pyrolysis,the effects of each gas in the mixture on pyrolysis are different.In the early stage of pyrolysis,the methylation reaction is dominant,the hydrogenation reaction is suppressed,and the yield of C2-C4 hydrocarbon gas phase products produced by pyrolysis is increased.In the later stage of pyrolysis,the hydrogenation reaction is the main,and the yield of CH₄ is reduced.?3?The yield of pyrolysis tar in mixed gas atmosphere is significantly higher than that in N₂ atmosphere.The maximum yield of pyrolysis tar in mixed gas atmosphere was reached at 3MPa 600?,which was 1.93%higher than that in N₂atmosphere.?4?The weight loss,yield of tar and water were increased with the addition of catalyst.At the reaction condition of 3MPa and600?,the yield of tar:FeCl₃>Fe₂O₃-Cl>Fe₂O₃/SiO₂>Fe₂O₃/?-Al₂O₃>no catalyst,water yield:Fe₂O₃/SiO₂>Fe₂O₃-Cl>FeCl₃>Fe₂O₃/?-Al₂O₃>no catalyst,weight loss rate:FeCl₃>Fe₂O₃-Cl>Fe₂O₃/?-Al₂O₃>Fe₂O₃/SiO₂>no catalyst.