Modeling Woody Biomass Torrefaction Process

Torrefaction is a thermal pretreatment process which usually takes place at temperatures between 200–300°C. Torrefied biomass has been proven in numerous studies to have superior combustion properties compared to raw biomass. The objective of this study is to develop a model to estimate solid energy yield, elemental compositions and enthalpy of solid and volatile yield. Formation enthalpy of raw and torrefied biomass is calculated using the correlations developed for elemental compositions and HHV of torrefied biomass. Solid yield is determined by anhydrous weight loss model for torrefied wood. Specific heat correlations for raw biomass and char are used to calculate the sensible heat required for torrefaction process. Sensible heat and formation enthalpy give the total enthalpy for raw and torrefied biomass. During torrefaction, a mixture of volatile compositions is released. Experimental mass fractions of the volatiles components are taken from published literature, which allowed us to determine the enthalpy of formation and specific heat of the volatiles. Finally, the model results associated with the torrefaction process are compared with experimental data.