Influence of Oxygen/Steam Addition on the Quality of Producer Gas during Direct (Air) Gasification of Residual Forest Biomass

Abstract

Biomass gasification is a relevant option to produce a gaseous fuel, it faces, however, several barriers regarding its quality for energetic applications. Therefore, in this study, air-steam and O2-enriched air mixtures were used as gasification agents during the gasification of residual biomass from eucalyptus to improve the producer gas quality. The steam addition promoted an increase in CO2 and H2 concentrations, whilst decreasing the CO and CH4 concentrations. The steam addition had no evident impact on the lower heating value of the dry producer gas and a positive effect on gas yield and the H2:CO molar ratio, attaining the later values up to 1.6 molH2∙mol−1CO. The increase in O2 concentration in the gasification agent (φ) promoted an increase in all combustible species and CO2 concentrations. The lower heating value of the dry producer gas underwent an increase of 57%, reaching a value of 7.5 MJ∙Nm−3dry gas, when the φ increased from 20 to 40 %vol.O2, dry GA. The gas yield had a significant decrease (33%) with φ increase. This work showed that the addition of steam or O2 during air gasification of residual biomass improved producer gas quality, overcoming some of the barriers found in conventional air gasification technology.