Effect of torrefaction on biomass pyrolysis based on thermogravimetric analysis

The influence of torrefaction temperature on biomass pyrolysis was studied by thermogravimetric with precise temperature control to simulate the real experimental condition. The torrefaction and pyrolysis experiments of three components (cellulose, hemicellulose and lignin) of biomass were carried out in the thermogravimetric analyzer. The results show that the weight loss of hemicellulose was significant at T200 (the torrefaction of 200℃) and T250 (the torrefaction of 250℃). When the torrefaction temperature was increased to 300°C, 74.4 wt% of cellulose was lost in the heat holding stage, and 61.9 wt% of hemicellulose was lost, while the thermal degradation of lignin is slight. According to the results of pyrolysis experiments, the pyrolysis of hemicellulose was easier with the increase of torrefaction temperature. The T300 (the torrefaction of 300℃) had great effect on cellulose and the weight loss peak basically disappeared. Lignin showed a similar trend, but the maximum weight loss peak moved to high temperature with the increase of torrefaction temperature. Torrefaction can promote the production of H2 during cellulose pyrolysis, and the maximum impact was observed at T300. T200 inhibited the formation of H2, CH4, CO products from hemicellulose and lignin pyrolysis, while T250 and T300 promoted. Compared with the raw cellulose pyrolysis, the activation energy of the samples after torrefaction at T200 and T250 increased, but decreased to 152.19 KJ/mol at T300. With the increase of torrefaction temperature, the unstable side-chain structure of most hemicellulose and a fraction of lignin were decomposed at T200 and T250, resulting in a trend of activation energy initially increasing and then decreasing.