Biomass fast pyrolysis in a fluidized bed reactor under N2, CO2, CO, CH4 and H2 atmospheres

Biomass fast pyrolysis is one of the most promising technologies for biomass utilization. In order to increase its economic potential, pyrolysis gas is usually recycled to serve as carrier gas. In this study, biomass fast pyrolysis was carried out in a fluidized bed reactor using various main pyrolysis gas components, namely N2, CO2, CO, CH4 and H2, as carrier gases. The atmosphere effects on product yields and oil fraction compositions were investigated. Results show that CO atmosphere gave the lowest liquid yield (49.6%) compared to highest 58.7% obtained with CH4. CO and H2 atmospheres converted more oxygen into CO2 and H2O, respectively. GC/MS analysis of the liquid products shows that CO and CO2 atmospheres produced less methoxy-containing compounds and more monofunctional phenols. The higher heating value of the obtained bio-oil under N2 atmosphere is only 17.8 MJ/kg, while that under CO and H2 atmospheres increased to 23.7 and 24.4 MJ/kg, respectively.