Effect of the Torrefaction Temperature on the Structural Properties and Pyrolysis Behavior of Biomass

Yunwu Zheng, Lei Tao, Xiaoyin Yang, Yuanbo Huang, Can Liu, Jiyou Gu, Zhifeng Zheng

Abstract


To improve prospects for high-value utilization of biomass, torrefaction pretreatments were conducted at 210, 230, 250, 270, and 300 °C with a reaction time of 30 min. The pyrolysis of torrefied biomass was also performed on a fixed-bed reactor system at 450 °C. The effect of torrefaction temperature on the yield, energy yield, structure, physical-chemical characteristics, and production composition of bio-oil was studied. The torrefaction pretreatment improved the fuel characteristics of pyrolysis products. When the torrefaction temperature was increased, the -OH and C=O contents decreased, the C=C contents increased, the pyrolysis peak temperature decreased, the residual carbon contents noticeably increased, and the Ea value remained in the range of 69 to 129 kJmol-1. The pore volume increased and the crystallinity index decreased due to degradation and recrystallization. The solid yield of pyrolysis biomass decreased sharply in contrast to the liquid yield. When the torrefaction temperature increased, the bio-oil yield decreased from 36.82 wt.% to 20.13 wt.%. The phenol content in the bio-oil markedly increased; however, oxygen-containing compounds such as acids, sugars, and furans, significantly decreased, which indicated that torrefaction pretreatment efficiently improved the quality of the fuel.

Keywords


Torrefaction; Biomass; Pretreatment; Production properties; Pyrolysis

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