Comparison of Experimental Results with Thermodynamic Equilibrium Simulations of Supercritical Water Gasification of Concentrated Ethanol Solutions with Focus on Water Splitting

Supercritical water gasification (SCWG) is a process in which biomass reacts with supercritical water to produce H2 and CH4-rich gas. The water-to-biomass ratio is a crucial variable in SCWG that affects the energy efficiency of the process. Despite the clear concept, systematic studies on water consumption during the formation of gaseous products are lacking. This study aims to determine the water consumption in SCWG of organic feedstock. Ethanol was used as an organic model compound since mass balances of complex biomasses like lignocelluloses are often incomplete due to the formation of solid deposits. The ethanol concentration ranged from 1.2 to 72 wt %, and complete gasification was achieved in all cases. Water consumption decreased with an increase in ethanol concentration due to enhanced methanation reactions with increasing organics. Stoichiometric calculations and ASPEN HYSYS simulations confirmed the experimental results, showing equilibrium gas compositions in the reaction system.