Enriched hydrogen production over air and air-steam fluidized bed gasification in a bubbling fluidized bed reactor with CaO: Effects of biomass and bed material catalyst

Gasification is one of the methods of generating biopower or biofuels from biomass waste. In this study, a bench-scale fluidized bed reactor was used for biomass air and air-steam gasification. Gasification was performed under constant operating conditions (~780 °C, equivalence ratio = ~0.32) to investigate the effect of biomass (switchgrass, pine residues) and bed materials (sand, CaO+ sand, Al₂O₃, and CaO + Al₂O₃). All gasification products, such as synthesis gas (syngas), contaminant gases, tar, and biochar (solid) were comprehensively analyzed. The composition of biomass significantly impacted CO and H₂ yield from volatile combustible matter and fixed carbon. Further, the presence of CaO made the condition favorable for the water-gas shift (WGS) reaction combined with the CO₂ carbonation reaction, which increased H₂ concentration. Additional steam with CaO increased H₂ concentration closer to 50% (N₂ free condition) through the combination reactions of steam hydrocarbon reforming and WGS by producing 44 g_H2/kg_{dry biomass} and 143 g_CO/kg_{dry biomass}. The usage of steam reduced the overall yield of contaminant gases, whereas the usage of CaO or Al₂O₃ decreased the amount of gasification tar by approximately 5.8–6.5 g_tar/kg_{dry biomass}. This study can provide valuable experimental data for biomass waste to produce better quality syngas.