An experimental study to investigate the effect of torrefaction temperature and time on pyrolysis of centimeter-scale pine wood particles

The aim of this study is to investigate the effect of torrefaction on pyrolysis of centimeter-scale pine wood particles at 520 °C. The experiments were conducted in a vertical tube furnace and the yields and compositions of bio-oil were measured. We found that torrefaction at 225 °C and 250 °C for 15, 25 and 35 min had little effect on the pyrolysis products. However, when wood was torrefied at 275 °C and 300 °C, significant char formation and transformation occurred. During the pyrolysis processes, lower weight loss rate and higher char fraction were observed for wood torrefied at 275 °C and 300 °C, but the center temperature profiles were not affected. Conversion time for pyrolysis was also not affected by the torrefaction conditions. Pyrolysis yields of liquid, gas and char were calculated and found to be affected by the torrefaction conditions. GC/MS analysis of bio-oil obtained from torrefied wood shows that the acid content decreases with increasing torrefaction intensity, implying improvement of bio-oil quality. Further, phenol content increases and guaiacols content decreases with the increase of torrefaction intensity. On the other hand, no novel species were detected and the overall effect of torrefaction was less remarkable than anticipated for the temperatures tested.