Thermodynamic Comparison between Conventional, Autothermal, and Sorption-Enhanced Bio-oil Steam Reforming

Abstract

This study presents a comprehensive thermodynamic analysis comparing three bio-oil steam reforming processes: traditional steam reforming, autothermal reforming, and sorption-enhanced steam reforming. Using Aspen Plus V12.1 software, simulations were performed to evaluate the hydrogen production, energy requirements, and influence of key process variables such as the temperature, pressure, or steam-to-carbon ratio. While traditional steam reforming is capable of achieving high hydrogen production, it requires substantial external energy input to drive forward the reaction, given the endothermic nature of the reactions. In comparison, autothermal reforming allows thermally neutral conditions by integrating endothermic steam reforming with exothermic partial oxidation reactions. Although the energy requirements significantly decrease, it also leads to lower hydrogen yields due to its consumption in the oxidation processes. In contrast, sorption-enhanced steam reforming improves hydrogen production compared to the other configurations ascribed to the in situ CO2 capture by using sorbents that shift the equilibrium toward hydrogen with purities over 98%, thus minimizing the need for additional gas separation processes apart from reducing the CO and CH4 formation. Additionally, the exothermic nature of the CO2 capture reactions contributes to reducing the energy requirements or even generates excess energy at certain conditions that can be used as a heat source. The bio-oil composition showed minor variations in hydrogen yields, making these findings applicable to different bio-oil compositions