Improvement of fuel characteristics for forest by-products applied surface torrefaction process

Abstract

Due to the continuous use of fossil fuels, global warming is accelerating; thus, the need for alternative energy sources has emerged. In this study, forest by-products (tree branches) were crushed into wood chips and pelletized to improve their fuel characteristics and energy yield through surface torrefaction; additionally, optimal process conditions for surface torrefaction were suggested. However, as determining optimal process conditions for surface torrefaction is laborious and time-consuming considering the energy yield, a mass reduction model was developed to effectively predict and ensure mass reduction applied as a variable in the energy yield. The rate constant was used to derive the mass reduction. The temperature, activation energy, and frequency factor applied as variables in the rate constant were derived through the finite element method and thermogravimetric analysis. The errors between the experimental and simulated energy yields of Populus euramericana and Pinus rigida wood chips were 0.04–0.85%p and 0.13–4.3%p, respectively, and of P. euramericana and P. rigida pellets were 0.18–1.15%p and 0.42–1.74%p, respectively. In this study, the improvement of fuel characteristics by species and type of forest by-products using the surface torrefaction process was confirmed, and the optimal process conditions were efficiently presented through a mass reduction model.