(634c) Effects of Steam and Oxygen On Syngas Composition Derived From Biomass Gasification

Experiments are conducted on a pilot-scale, pressurized bubbling fluidized bed biomass gasifier to investigate effects of oxygen and steam on syngas composition. The oxygen content in the enriched air varies from 21, 45, to 80 vol% on dry basis, corresponding to 21, 30, and 40 vol% on wet basis.  The bed temperature is maintained at 800 °C for all tests. Three different biomass feedstock with nitrogen contents varying from 0.5 to 1.4 wt% are used for study. Syngas composition is measured using a combination of micro gas chromatograph, a modified IEA Tar Protocol, and Karl Fischer Titration. Results indicate that oxygen-enriched air and steam gasification favors the production of combustible gas components including hydrogen, carbon monoxide, methane, and lighter hydrocarbons. When 40% oxygen is used, hydrogen and carbon monoxide can increase by up to 70% and 34%, respectively, for particular feedstock. Overall, it is found that oxygen and steam gasification is most effective for feedstock with low nitrogen and moisture contents. Results also show that ammonia and NOx concentrations in syngas increase as oxygen enrichment increases. The lower heating value of syngas can increase by as much as 43% for the feedstock studied. When the oxygen level increases from 21% to 40%, the H₂/CO ratio also increases to a moderate level.