Thermal and kinetic analyzing of pyrolysis and combustion of self-heating biomass particles

Abstract

As a renewable fuel, the application of biomass fuel gets more and more attention. Fire and explosion are the main safety problems in the biomass fuel storage process. The characteristic parameters and kinetic analysis of pyrolysis and combustion are significant to guide the safe storage of biomass fuel. In this work, the thermogravimetric analysis (TGA) was used to obtain the pyrolysis and combustion characteristics of corn straw powder, poplar wood chip and rice husk in nitrogen and air, respectively. The Thermogravimetry-Differential Thermogravimetric (TG-DTG) profile shows that the pyrolysis process of these biomass includes three stages of drying, pyrolysis and carbonization, while the combustion process includes three stages of drying, devolatilization and coke combustion. The main reaction stage of biomass pyrolysis and combustion are roughly between 170∼400 °C and 180∼530 °C, respectively. With the increase of the heating rate, TG and DTG profiles shifts to the high temperature side. Furthermore, the kinetic analysis was performed by using Kissinger-Akahira-Sunose (KAS), Flynn-Wall-Ozawa (FWO), Friedman, and Coats-Redfern (CR) methods, based on the thermogravimetric experimental data. The activation energy of biomass pyrolysis is shown to be between 70∼100 kJ/mol. For the activation energy of biomass combustion, the calculated value from isoconversional methods is between 140∼180 kJ/mol. The calculated value from CR method is between 80∼150 kJ/mol, and the activation energy of the coke combustion stage is greater than that of the devolatilization stage. Finally, the auto-ignition experiment of biomass particles was designed and conducted, indicating that the corn straw powder is more prone to spontaneous combustion, followed by rice husk and poplar wood chip, which corresponds to the results of activation energy. And the fire hazard of the biomass particles was analyzed according to the characteristic parameters. This work provides fundamental data to promote the development of storage techniques and facilitate the safe production of biomass particles.