甘油超临界水气化制氢过程参数和动力学研究

Study on Operational Parameters and Kinetics of Hydrogen Production by Glycerol Supercritical Water Gasification

  • 摘要: 为研究甘油超临界水气化制氢过程及转化动力学,采用正交试验和单因素试验,在连续式反应器中,分析不同工艺参数对甘油超临界水气化气体产物分布和气化转化效率的影响,对气体产物进行气相色谱分析。利用集总动力学研究方法,优化甘油超临界水气化转化动力学模型,增加CO2甲烷化反应路径,探讨甘油超临界水气化过程中动力学参数和气相产物生成及消耗路径。结果表明:甘油超临界水气化制氢的最佳工况为温度600 ℃、甘油浓度0.015 mol/L、压力27 MPa和停留时间18 s,此时H2产量为2.411 mol/mol,气化效率为76.49 %。单因素试验结果可知,较高反应温度和压力、较低原料浓度和适当延长停留时间有利于提高H2产量和甘油气化效率。反应速率常数随着温度的升高而增加,甘油热解路径Ⅱ和中间体蒸汽重整路径Ⅰ的活化能分别高于甘油热解路径Ⅰ和中间体蒸汽重整路径Ⅱ。H2主要通过甘油热解和水气变换反应生成,CO2主要通过甘油热Ⅰ和水气变换反应生成,CO2甲烷化是H2和CO2消耗的主要路径。中间体热解是CO和CH4的主要生成路径,CO的主要消耗路径是水气变换反应。

     

    Abstract: In order to explore the conversion kinetics and the change rules of gas yield and gasification efficiency under different process operational parameters, the experimental studies on the gasification of glycerol in supercritical water were carried out, based on the continuous flow reactor. And the orthogonal test and single factor test methods were used for the experimental studies. The gas products were analyzed by a gas chromatography. At the same time, based on the above experimental data, the lumped kinetic research method was carried out. To optimize the kinetic model of glycerol supercritical water gasification, the CO2 methanation reaction path was added. Then some important kinetic parameters were obtained, and hydrogen generation and consumption paths in glycerol supercritical water gasification process were further discussed. The results showed that the optimal conditions for hydrogen production of glycerol supercritical water gasification were as follows: reaction temperature 600 ℃, glycerol concentration 0.015 mol/L, reaction pressure 27 MPa and residence time 18 s. Under this reaction conditions, the hydrogen production was 2.411 mol/mol, and the gasification efficiency was 76.49 %. Besides, the results of single factor experiments showed that higher reaction temperature, lower feedstock concentration, appropriately extended residence time and higher reaction pressure were beneficial to increase H2 yield and glycerol gasification efficiency. In addition, based on the modified kinetic model of glycerol gasification, it can be found that the activation energy of glycerol pyrolysis path Ⅱ and intermediate steam reforming path Ⅰ were higher than that of glycerol pyrolysis path Ⅰ and intermediate steam reforming path Ⅱ, respectively. And the reaction rate constant increased with the increasing temperature. H2 was mainly generated through glycerol pyrolysis and water-gas shift reaction, CO2 was mainly generated through glycerol pyrolysis Ⅰ and water-gas shift reaction, and CO2 methanation reaction was the main path of H2 and CO2 consumption. Intermediate pyrolysis is the main pathway for the production of CO and CH4, and the main pathway for the consumption of CO is the water-gas conversion reaction. The experimental study and kinetic analysis above provided the basic data and theoretical basis for fully revealing the mechanism of hydrogen production by glycerol supercritical water gasification.

     

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