Syngas, tar and char behavior in chemical looping gasification of sawdust pellet in fluidized bed

Due to the advantages of high energy density and convenient transportation, the use of pelletized biomass as fuel for power supply has gained interest over recent years. Chemical looping gasification (CLG) integrates the process of gasification and hot gas conditioning, with the objective to obtain syngas with a low tar amount. The work presents some experimental results using sawdust pellet with high-volatile and low-ash content as fuel, and a natural manganese-iron ore as oxygen carrier for CLG in a bubbling fluidized bed. Without the addition of external steam, the syngas, tar, and char collected at different temperatures (750-950 degrees C) and oxygen carrier to biomass ratios (0.2-1.2) were investigated to determine the gasification performance of sawdust pellet. Three-phase product distributions during CLG process were identified under different operating parameters. The increase of reaction temperature enhances the gas production, with decreasing amount of liquid and solid. Also, it has significant influence on the main gases (CO, CO2, H-2 and CH4) distributions in the syngas. Meanwhile, more Polycyclic-Aromatic Hydrocarbons (PAHs) are cracked to Mono-Aromatic Hydrocarbons (MAHs) and further decomposition into syngas, which is confirmed by further Gas Chromatography-Mass Spectrometer (GC-MS) analyses. The Mn/Fe-based oxygen carrier also exhibits a beneficial effect on catalytic cracking of PAHs into MAHs. As for the remaining char, a higher temperature is more sensitive to produce the char with more porous structure and brittle texture.