Simulation of High Temperature Air – Steam Biomass Gasification in a Downdraft Gasifier Using ASPEN PLUS

A comprehensive process model is developed for high temperature air – steam biomass gasification in a downdraft gasifier using the ASPEN PLUS simulator. The simulation results are compared with the experimental data obtained through pilot scale downdraft gasifier. In this study, the model is used to investigate the effects of gasifying agent preheating, equivalence ratio (ER), and steam/biomass (S/B) on producer gas composition, high heating value (HHV), and cold gas efficiency (CGE). Results indicate that H2 and CO contents have increased when gasifying agent preheating is used, while gasifying agent preheating has no effect with H2 and CO at high ER. At high level of S/B, the concentrations of H2 and CO are related with water-gas shift reaction in significant. HHV and CGE depend on the concentrations of H2 and CO in producer gas, which can increase by preheated gasifying agent. However, gasifying agent preheating should apply with waste heat from the process because there is no additional cost of energy price.