Gasification of biomass using oxygen-enriched air as gasification agent: a simulation study

A steady-state Aspen Plus model was established to numerically study biomass (ramie residues) gasification using air as gasification agent. This study proposed a comprehensive model which used the thermodynamic equilibrium and chemical kinetics to accurately simulate the char combustion and char/volatiles gasification, respectively, to search for optimal gasifier operating conditions. The proposed model correctly predicted the products yield, gasifier performance and the composition of the produced syngas, and therefore the higher heating value (HHV). The effects of air temperature and oxygen content in gasification agent on the gasification characteristics were discussed. The gas yield slightly increased with the increase of air temperature, while char conversion efficiency (CCE) firstly increased and then declined attributing to the slight increase of tar cracking with the increase of air temperature. The results also indicate that higher oxygen ratio (OR) leads to higher H 2 production and lower tar yield. Compared to the maximum H 2 content (11.17 vol%) and the syngas HHV (6.22 MJ/Nm 3 ) at OR = 31.4%, they are respectively reduced to about 35.45% and 21.7% when OR drops to 21%. The present model opens the possibility of predicting the gasification characteristics using different gasification agents and feedstocks based on their chemical compositions.