Experimental investigation of tar formation and producer gas composition in biomass steam gasification in a 100 kW dual fluidised bed gasifier

From this study, it is found that there was a positive correlation between tar contents in the devolatilization product gas and those in the final producer gas from gasification. In the devolatilization stage, radiata pine biomass yielded more phenols, while corn stover generated more toluene. Based on the results of this study, tar formation mechanism was proposed which is verified by the observation that more naphthalene was present in the producer gas from gasification of radiata pine while gasification of corn stover produced more biphenyl. The experimental results also show that at gasification temperature of 700 °C, the producer gas yield was the highest for corn stover followed by rice husk and then radiata pine wood. However, for gasification at 800 °C, the trend was reversed with radiata pine having the highest yield followed by risk husk and the corn stover. At both 700 and 800 °C, the radiata pine biomass produced a producer gas with higher contents of H2 and CH4 while the producer gas from rice husk had a higher content of CO and that from corn stover had a higher content of CO2, C2H4 and C2H6. These differences are closely related to the chemical composition of the biomass which was also analysed in this study. Radiata pine had a higher content of lignin (31.96 wt%), rice husk had a higher content of hemicellulose (25.30 wt%) while corn stover was rich in cellulose (69.85 wt%).