Experiments and modeling of the torrefaction of white wood fuel pellets

Abstract

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.

Some Properties of Briquettes and Pellets Obtained from the Biomass of Energetic Willow (Salix viminalis L.) in Comparison with Those from Oak (Quercus robur)

“…In order to be able to have a discussion on the properties of the analyzed briquettes and pellets, the average values from the paper were centralized together with those of other authors and standards [34,50,56] in Table 3. In addition to these data, other data were taken and analyzed from the research studies of other authors [7,27,35,[41][42][43]57,[70][71][72]. The unit density of energetic willow briquettes (766 kg/m 3 ) was 12.5% lower than that of oak; this difference is due to the 68.7% increased density of oak wood compared to that of energetic willow biomass.…”

“…This modeling starts from the premise that all lignocellulosic materials have a different calorific value of the chemical constituents, respectively, of 24.4 MJ/kg for lignin, 18.6 MJ/kg for cellulose, 16.1 MJ/kg for hemicelluloses, 34.5 MJ/kg for extractives, and 0.2 MJ/kg for ash [60][61][62][63][64][65][66][67][68][69]. The influence of the torrefaction process is also considered [35,[69][70][71], along with other original research-specific correlations. If the different participation percentage of the chemical components for each wood species is taken into account, the following calculation relationship (Equation ( 18)) is obtained:…”