Supercritical Water Gasification of Ethanol as Biomass Model Compound in Tandem with Steam Reforming: Kinetic Modeling of the Reforming Step and Techno-Economic Analysis of the Integrated Concept

The integration of “biomass gasification with supercritical water ”, “steam reforming of hydrocarbons”, and “water–gas shift reaction” is a promising process concept for the conversion of moist biomass to “green hydrogen”. This process concept was investigated in this work, considering ethanol as a biomass model compound. The gasification of ethanol with supercritical water can be accurately simulated, allowing a very good prediction of the gaseous product that will undergo steam reforming. A multidisciplinary study is presented, in which a comprehensive kinetic model for steam reforming of the gasification product gas was developed and validated with experimental data and then employed in a simulation of the whole process chain. Finally, a techno-economic and sensitivity analysis was applied. In the kinetic model, the high steam content overshadowed the influence of other substances in the sites balance on the catalyst surface, except for methane. After investigating the effect of ethanol concentration and feed flow rate, and considering the technical constraints imposed by the high organic matter content and the availability of actual waste biomass, the optimal values of the ethanol concentration and feed flow rate were 50 t h$^{–1}$ and 15 wt % ethanol, reaching a hydrogen break-even price of 6.8 $ kgH$_2$$^{–1}$. ... mehrThe sensitivity analysis identified the ethanol price as the primary cost driver. Exploring waste biomass feedstocks, such as sewage sludge, demonstrated potential break-even prices as low as 0–1.8 $ kgH$_2$$^{–1}$, which can compete with conventional technologies.