Experiments and modeling of the torrefaction of white wood fuel pellets

The main purpose of this study was to find the optimal conditions for thermal treatment of white wood pellets. Other goals of this study were to compare torrefied and white pellets and to model the treatment process. Three types of pellets acquired from different manufacturing companies in the pellet market, representing distinct wood species, were torrefied at different temperatures of 160, 180, 200, and 220 °C, for 1, 2, and 3 h. After thermal treatment, the properties of the treated pellets were determined, including their mass loss, calorific value, ash content, and shear strength, and compared with those of the non-torrefied pellets. The calorific value increase was modeled based on the thermal degradation of hemicellulose and cellulose of the pellets and the correlation between the calorific value and mass loss. It was concluded that torrefied pellets have an increase in calorific value up to 22%, because of hemicelluloses degradation.