Physicochemical changes and energy properties of torrefied rubberwood biomass produced by different scale moving bed reactors

This study aimed to investigate the physicochemical changes and energy properties of torrefied rubberwood sawdust (RWS) produced in various sizes of moving bed reactors for further pelletization. The results indicate that the torrefaction of RWS with a small-scale reactor at higher temperatures led to a stronger degree of torrefaction (DT) based on various indicators. Torrefaction at 250 °C for 60 min provided appropriately torrefied RWS with solid yield, energy yield, energy content, and energy density of 70.23%, 81.20%, 22.20 MJ/kg, and 5.40 GJ/m3, respectively. The RWS with higher DT was coal-black instead of brown, as indicated by its L*, a* and b* color coordinates. The changes in color and DT were also consistent with the improvements in fuel ratio, atomic ratios, lignin content and functional groups (FTIR). SEM imaging and BET adsorption also confirmed the surface changes from raw RWS to torrefied RWS. At the same nominal conditions, torrefaction of RWS with a larger scale reactor gave a small difference in solid yield and in properties of the torrefied RWS. In addition, the production and energy costs are the key concerns in a large-scale operation. These results support pursuing further applications, like the pelletization of torrefied RWS.