Syngas Production from Biomass in a Fixed Bed Gasifier using Aspen PlusTM: Modelling and Simulation

The production of biofuels from biomass offers an alternative to supply the limited reserves of petroleum. Currently, biomass is utilized in various thermochemical processes, with gasification being a notable example. Gasification produces synthesis gas, a mixture mainly composed of CO, H2, and CO2. This gas is utilized to generate energy, various chemical products, and biofuels such as bioethanol. Using mathematical models and their computational simulation can help to evaluate the feasibility of this technology regarding operational conditions. This work aims to simulate a fixed-bed gasifier (FB) using elemental and proximate analysis, considering steady state, and employing the Aspen Plus™ simulator. The model accounts for several processes relevant to converting biomass into synthesis gas, including drying, pyrolysis, oxidation, reduction of CO2, H2O, and H2 with char, and tar cracking. The gasifier model is based on yields and chemical kinetics, using data from studies on char produced from sugarcane bagasse. Fourteen reactions were considered to represent the gasification process. The effects of the equivalence ratio (ER), steam injection, and air preheating on the composition of synthesis gas were examined. It was observed that the gasification temperature increases nearly linearly with the air temperature and that increasing the ER reduces the amount of CH4. Low ER lead to higher CO levels compared to CO2. For ER values of 0.29-0.38, CO2 dominates the composition, with only slight changes in H2, unlike the other gases (CO, CO2, and CH4). High H2 levels are observed when the SB ratio for the LF reactor is varied; as this ratio increases, H2 and CO2 concentrations also rise, while CO levels decrease (SB values = 1.75).