Generation Characteristics of Gas Products in Fluidized Bed Gasification of Wood Pellets Under Oxygen-Enriched Conditions and Their Effects on Methanol Synthesis

Methanol synthesis can utilize the product gas from biomass gasification and the hydrogen generated from water electrolysis. Biomass gasification, as an upstream process, affects the subsequent hydrogen supplement amount and has a direct relationship with the methanol yield. Fluidized bed oxygen-enriched gasification has a particular advantage for biomass and is expected to utilize the remaining oxygen from water electrolysis. In this study, the effects of operating parameters, including the equivalence ratio ER, temperature T, oxygen percentage OP in oxygen-enriched air, steam-to-wood pellets mass ratio S/W, and fluidization velocity ug, as well as the choice of bed materials, on the volume fractions of the gas products and the gas yield from the fluidized bed oxygen-enriched gasification of wood pellets were investigated. The effects of the generation characteristics of gas products on the hydrogen supplement amount and the methanol yield were also analyzed. The results showed that the volume fraction of H2 reached its peak values of 10.47% and 18.49% at an ER value of 0.28 and a ug value of 0.187 m/s, respectively. The methanol yield reached its peak value of 0.54 kg/kg at a ug value of 0.155 m/s. The volume fraction of H2 increased from 6.13% to 11.74% with an increasing temperature from 650 °C to 850 °C, increased from 5.72% to 10.77% with an increasing OP value from 21% to 35%, and increased from 12.39% to 19.06% with an increasing S/W value from 0.16 to 0.38. The methanol yield could be improved by increasing the ER value, T value, OP value, or S/W value. When the bed materials were changed from quartz sands to dolomite granules, the H2 volume fraction significantly increased and the hydrogen supplement amount required for methanol synthesis reduced.