Thermodynamic assessment of the fixed-bed downdraft gasification process of fallen leaves pelletized with glycerol as binder

In this work, the effect of airflow rate and glycerol content of pelletized fallen leaves (FL) on a fixed bed gasification process is studied. FLs were collected in the main campus of the University of Antioquia (Medellin, Colombia). Levels of airflow rate tested were 0.075, 0.150, and 0.225 kg/s/m²; and the glycerol content of pellets evaluated were 0 and 5%wt. When the airflow rate increased, flame front velocity increased up to 51.3%. This behavior was attributed to high temperatures in the reaction front, which were favored by the decrease of fuel-air equivalence ratio leading to high biomass consumption in the gasification process. Regarding the glycerol content of the pellets, production of gaseous species was favored with this compound, where an increase of CH₄ by 25% and H₂ by 20% was observed with regard to the raw pellets. The high concentration of the gaseous fuel species leads to an increase of cold gas efficiency (CGE) as well as chemical exergy efficiency (CEE) by ∼13%. Whereas, the irreversibilities (I) of the thermochemical process decreased by 10% when pellets with glycerol content were gasified.