Thermal Pretreatment of Lignocellulosic Biomass

Torrefaction is a process to convert diverse lignocellulosic biomass feedstocks into an energy dense homogeneous solid, a pretreatment for subsequent. thermochemical conversion. Loblolly pine was treated by wet torrefaction (hot compressed water. 200-260 degrees C) and dry torrefaction (nitrogen, 250-300 degrees C), with mass yield of solid product ranging between 57 and 89%, and energy densification to 108-136% of the original feedstock. The solid product has been characterized, including proximate analysis, fiber analysis, ultimate analysis, and equilibrium moisture. In both dry and wet torrefaction, increasing temperature results in decreased mass yield and increased energy densification, and result,,; in a solid with increased carbon content, decreased oxygen content., and decreased volatiles. The biomass is tram formed into a,fuel similar to a low-rank coal. Generally, the wet torrefaction process produces a solid with greater energy density than dry torrefaction, with the same mass yield. The fiber analysis indicates that hemicellulose is quickly removed during wet torrefaction, and the solid product contains substantial quantities of aqueous soluble compounds. The equilibrium moisture content of solids produced by both processes is somewhat decreased from that of the biomass feedstock, indicating a hydrophobic solid suitable for storage and transportation. (C) 2009 American Institute of Chemical Engineers Environ Prog, 28: 435-440, 2009