Gaseous production kinetics and solid structure analysis during isothermal conversion of biomass pellet under different atmospheres

Isothermal chemical conversion of biomass pellets under the atmospheres of Ar, CO2 and O2 were conducted in this study to explore the effects of atmosphere and temperature on the gaseous releasing process and kinetics, and the structure of the solid char/ash products. Results showed that the gas production was promoted while the solid yield was decreased with the raising temperature. The CO2 reaction with char during gasification process mainly happened after 800 degrees C that the CO formation lasted for a longer time than pyrolysis. The surface area of char under CO2 atmosphere was increased to 215.57 m2/g with the increased temperature to 800 degrees C, but it was sharply reduced to 5.10 m2/g when the temperature further raising to 900 degrees C due to the destroyed carbon skeleton. The CO2 formation was largely promoted with a low activation energy of 11.98 kJ/mol during O2 oxidation process. Compared with the crystal structure of solid residues obtained under Ar and CO2 atmospheres, O2 oxidation process resulted in more complex crystal peaks with the main compositions of SiO2, K2SO4, and CaO. This study should be helpful to further understand the thermal conversion of biomass in a complex reaction atmosphere.