Numerical investigation of CO2 valorization via the steam gasification of biomass for producing syngas with flexible H2 to CO ratio

This work presents a numerical investigation into CO2 valorization via the gasification of poplar wood. It is aimed at determining an optimum gasification condition for enhancing the production of syngas with a flexible H2 to CO molar ratio (H2/CO), which is essential in many petrochemical processes. The research is performed by simulation in ASPEN Plus, where steam and CO2 are fed as co-gasifying agents. The equilibrium concentrations of the product gas are obtained, and the H2/CO as well as the heating value of the resulting syngas are quantified. It is found that the inclusion of CO2 as a co-gasifying agent promotes CO evolution through the Boudouard reaction. However, it reduces H2 concentration, and consequently decreases the H2/CO. Furthermore, the effects of some process parameters have been studied in this work. It is observed that H2/CO reduces with a rise in temperature, increases with increasing CO2 to biomass ratio (CBR), and shows no significant change with pressure. Results further show that methanol synthesis from syngas can be achieved at temperatures close to 660 °C, while oxo-synthesis requires a higher temperature. A CBR of around 0.6 in the present work would be an optimum value for Fischer-Tropsch synthesis to achieve a H2/CO of 2:1, but the CBR should be lower for processes requiring a lower H2/CO like acetic acid formation and oxo-synthesis.