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Rubberwood biomass is widely available in the southern region of Thailand and it has high potential for biofuel applications. Applications of this biomass still have some limitations, however, such as low energy properties and high biological decomposition. Therefore, the aim of this study was to enhance the fuel properties of rubberwood biomass by a torrefaction process. Rubberwood sawdust (RWS) was torrefied at different temperatures (200, 250, and 300 °C) and for various times (20, 40, and 60 min) in a moving bed reactor. The product yield and characteristics of torrefied RWS were investigated. Results showed that the solid yield of torrefied RWS was in the range of 39.07–88.69%, depending on temperature and time. The fuel atomic ratios of torrefied RWS were better than of raw RWS. The energy content and energy density of torrefied RWS were clearly enhanced (19.78–27.17 MJ/kg and 4.94–6.59 GJ/m3). ICP-OES results revealed a variation of inorganic elements in torrefied RWS, which was consistent with the ash components given by XRF. Ash fusion temperature of raw RWS and torrefied RWS ashes was stable at 1458 °C. The slagging index of torrefied RWS was decreased, while its fouling index was elevated. [Display omitted] • Yield and properties of torrefied RWS were clearly influenced by temperature. • Fuel atomic ratios and energy properties of RWS were improved by torrefaction. • Fusion temperature of torrefied RWS ash was above 1458 °C. • Torrefaction increased fouling index of RWS but reduced its slagging index. [ABSTRACT FROM AUTHOR]

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. [Display omitted] [ABSTRACT FROM AUTHOR]