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 (similar to 780 degrees C, equivalence ratio = similar to 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 H-2 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 H-2 concentration. Additional steam with CaO increased H-2 concentration closer to 50% (N-2 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.