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

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.