Effect of Torrefaction Process Parameters on Biomass Feedstock Upgrading

Biomass is a primary source of renewable carbon that can be utilized as a feedstock for biofuels or biochemicals production in order to achieve energy independence of energy importing countries. The low bulk density, high moisture content, degradation during the storage, and low energy density of raw lignocellulosic biomass are all significant challenges in supplying agricultural residues as a cellulosic feedstock. Torrefaction is a thermochemical process conducted in the temperature range between 200°C, and 300°C under an inert atmosphere which is currently being considered as a biomass pretreatment. Competitiveness and quality of biofuels and biochemicals may be significantly increased by incorporating torrefaction early in the production chain while further optimization of the process might enable its autothermal operation. In this study, torrefaction process parameters were investigated in order to improve biomass energy density, and reduce its moisture content. The biomass of choice (corn stover) at three levels of moisture content (30%, 45%, 50%) was torrefied at three different temperatures (200°C, 250°C, 300°C), and reaction times (10min, 20min, 30min). Solid, gaseous, and liquid products were analyzed and the mass/energy balance of the reaction was quantified. Overall increase in energy density, and decrease in mass and energy yield was observed as process temperature increased. Initial biomass moisture content affected energy density, mass, and energy yield especially at low process temperature, and high moisture feedstock.