Torrefaction of fibrous empty fruit bunch under mild pressurization technique

Abstract

The use of inert gases such as nitrogen continuously during torrefaction causes a burden in terms of operational cost. Therefore, a novel concept of mild pressurization has been introduced to eliminate the dependence on the inlet gas completely. In the present study, the torrefaction of fibrous empty fruit bunch (EFB) was performed for various temperatures of 250 °C–300 °C and residence times of 30–90 min. The pressure exerted by the load during torrefaction was 0.0230 MPa. The results show that torrefaction temperature is a dominant parameter in affecting physical and physicochemical properties as well as thermal stability of the torrefied EFB rather than residence time. An increase in temperature causes an improvement in gross calorific value, hydrophobicity, atomic H/C and O/C ratios as well as thermal stability. Besides, it was found that the EFB experiences a significant change after torrefaction at temperature of 300 °C in terms of surface, microstructure, crystallographic structure and functional groups. This is mainly due to the significant decomposition of the main biomass constituents especially hemicellulose and cellulose. Overall, it can be concluded that the best performance was obtained at torrefaction temperature of 300 °C and residence time of 90 min.