Pyrolysis of Phragmites hirsuta study on pyrolysis characteristics, kinetic and thermodynamic analyses

This study is dedicated to the pyrolysis behavior and kinetic characteristics of bioenergy potential Phragmites hirsuta (root, stem and leave) by thermogravimetric analyzer using five different heating rates (10, 20, 30, 40, 50°C/min). The pyrolysis of three parts can be divided into dehydration, volatilization and carbonization, which the main decomposition temperature was 280°C to 350°C with weight losses of 60%. Kinetics thermodynamic characteristics were carried out using three model-free iso-conversional methods, including Flynn-Wall-Ozawa, DAEM and Friedman methods, in which the activation energy of root, stem and leaf were 130 to 177, 128 to 159 and 124 to 157 kJ/mol, respectively. The activation energy in the root higher than stem and leaf indicated higher reactivity of the pyrolysis. The reaction mechanisms of root, stem and leaf fit well with different Avarami-Erofeev reaction models. The pyrolysis of different parts can be separately resolved into three pyrolysis peaks, which represent the pyrolysis of hemicellulose, cellulose and lignin, respectively. The corresponding temperature of hemicellulose pyrolysis peak is leaf < stem < root. This research will provide theoretical basis for high-value utilization of biomass and new ideas for selective pyrolysis of biomass.