Numerical investigation of a process model integrating gasification and tar removal

The corrosion and damage of equipment caused by tar condensation seriously hinder the further development of biomass gasification technology. Therefore, a process model integrating gasification and tar removal was established using Aspen Plus based on chemical reaction kinetics and oil-based gas washer (OLGA) tar removal technology. In this paper, phenol was selected as the light tar representative, and pyrene was selected as the heavy tar representative. The effect of gasification conditions on syngas production and tar content was determined, and the rectifying towers in the tar removal process were optimized and analysed. Sensitivity analysis of the gasification process showed that the steam in the gasifier was beneficial to increase the H2 composition but reduced the higher heating value (HHV) of the combustible syngas. The introduction of air reduced the content of combustible syngas and the HHV in the gasifier. More importantly, the tar content in syngas could be reduced by increasing the gasification temperature, steam-to-feedstock ratio (SFR) and equivalence ratio (ER). On the other hand, the optimization results of the tar removal process showed that the proposed tar removal process model was effective for the removal of light tar and heavy tar. The process model can realize the recycling of solvents, and the loss rates of solvent 1 and solvent 2 were 4.27% and 0.68%, respectively. In addition, light tar can be recovered in the process of tar removal; its recovery rate was 96.42%, and the water outflow rate with tar was only 8.77%.