Bioenergy has been utilized for domestic purposes since pre-recorded history and it catches the highlight in the recent decades because it naturally benefits the world climate and energy security. Gasification is one of the key technologies to efficiently and economically convert biomass into syngas and further into biofuels. Despite these outstanding advantages, biomass gasification suffers from the formation of unfavorable byproduct tar and the consequential tar elimination. Moreover, the collected tar is toxic and thus requires storage and strict deposit method to avoid environmental pollution.

To understand the mechanisms of biomass gasification and tar production, simulations with Aspen Plus were conducted for both downdraft and updraft gasifiers, which are presented in the Paper I and II, respectively. The kinetic models are implanted with reaction kinetics to ensure their ability to approximate the tar production, which are superior to the widely used Gibbs Energy Minimization model for predicting syngas compositions. Paper III focuses on the investigation of the impact of tar recycling on syngas compositions under various operating conditions including different reactor scales (4", 8", 12"), different biomass feedstocks (pellets, picks, and flakes) and different equivalence ratios (0.15, 0.20, 0.25).