Thermal decomposition and kinetic modeling of torrefied Cryptomeria japonica in a CO2 environment

Abstract

ABSTRACTThermogravimetric analysis of raw (CJ-raw) and torrefied Cryptomeria japonica at 250°C (CJ-250) and 350°C (CJ-350) is performed in a pure CO2 environment on three heating rates of 10, 15 and 20°C/min. During pyrolysis, thermal decomposition occurred in three different stages: dehydration, hemicellulose-cellulose and lignin decomposition at 30.2–102.6°C, 222.6–422.1°C and 426–847.2°C, respectively. The simulated linear model fit quite well with the experimental data. A kinetic analysis of the raw and torrefied samples was also performed. In the main decomposition stage (the second stage), the activation energies of CJ-raw, CJ-250 and CJ-350 are 77, 114 and 50 kJ/mol, respectively. The highest activation energy (of CJ-250) is found to be due to the higher quantity of cellulose in the sample compared with other two samples. The activation energy of CJ-350 shows the lowest value because most volatiles in the hemicellulose–cellulose zone are expelled during the torrefaction process. A rising heating rate shifts the mass loss toward higher temperature, increasing the activation energy and the pre-exponential factor.