Torrefaction can serve as thermal pretreatment prior to fast
pyrolysis for improving the quality of bio-oil. Heating value and
pH of bio-oil increased with elevated torrefaction severity, whereas
the yield of bio-oil decreased significantly. The decrease of bio-oil
yield was attributed to the crosslinking and charring of corncobs
during torrefaction. The factors affecting crosslinking and charring
of biomass include torrefaction temperature, residence time and
heating rate. Hence, in order to limit crosslinking and charring, torrefaction
using microwave reactor in low temperature or torrefaction
using heat carrier (e.g. silica sand) for high heating rate and
short residence time is preferred in next study.