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

Abstract

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 gH2/kgdry biomass and 143 gCO/kgdry 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 gtar/kgdry biomass. This study can provide valuable experimental data for biomass waste to produce better quality syngas.