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In this work is studied the effect of biomass packing factor (PF) and oxygen enriched air as gasifying agent (GA) on fixed bed biomass gasification. Oxygen concentrations in GA are 21, 24 and 29% vol. The biomass used as fuel is Jacaranda Copaia wood with three defined particle forms: square prism, cylindrical and chips. Flame front velocity and biomass consumption rate increase with oxygen concentration in the GA. These results are due to smaller amount of nitrogen involved in the process, which leads to decrease thermal energy losses by nitrogen heating. Moreover, lower convective cooling effect of gas over solid phase and lower radiation attenuation in the solid are reached with less nitrogen concentration in GA. The efficiency slightly increases when PF increases, this is due to less radiation penetration from the oxidation zone to drying and pyrolysis stages, thereby biomass consumption rate decreases. [ABSTRACT FROM AUTHOR]

Biochar (BC) is a solid byproduct of gasification and could be valorized looking for contributing to the feasibility of gasification projects. In this study, the effect of airflow during fixed-bed gasification of pelletized fallen leaves to BC was evaluated at 0.075 and 0.150 kg/s/m2. The influence of glycerol in the leaf feedstock was also studied, and the gasification products were characterized. BC formation under gasification conditions was simulated using a two-dimensional (2D) unsteady computational fluid dynamics (CFD) model. When airflow was increased, convective heat transfer from the gas to the solid phase increased by 250%, and absorption of radiative heat transfer in the solid phase increased by 59%. This was ascribed to the increase in the process temperature, which also promoted the release of volatile matter. The H:C and O:C ratios in the feedstocks were reduced by 80% and 92%, respectively. The surface areas and pore volumes of the samples increased by up to 50%. The BC with the largest surface area (68.63 m2/g) also had the highest total organic carbon content (21.3%) and the highest water retention capacity (408.13%). The pH of the BCs obtained in the study ranged from 8.7 to 10, making them suitable for acid soils. • Gasification's cold gas efficiency of fallen leaves pellets (FLP) is up to 60%. • Convective and radiative heat transfer affect physicochemical properties of biochar. • If glycerol increases, biochar (BC) density decreases and BC temperature increases. • FLP's BC as a byproduct of fixed-bed gasification is suitable for acid soils. • FLP's BC is not suitable as a solid fuel due to its high ash content (∼58 wt%). [ABSTRACT FROM AUTHOR]