Hydrogen production from supercritical water gasification of biomass and thermodynamic modeling

In this study, suitable reaction parameters were investigated for hydrogen production by supercritical water gasification (SCWG) of fruit pulp, which is a by-product of a fruit juice factory. For that purpose, the effects of reaction parameters such as temperature (400-600°C), time (0-180 min), biomass:water ratio (2.5-10.0%), catalyst ratio (0-70%) and type (KOH, K2CO3 ve Ru/C) on the yields of gas, liquid and solid products as well as their compositions were determined. Furthermore, a thermodynamic model was proposed for SCWG and the numerical results were validated with the experimental data for varying temperature and biomass ratio. Gasification efficiency and H2 amount in the gas mixture increased with temperature and decreased considerably with increasing biomass ratio. H2 amount was determined as 32.1 mol/kg biomass at 600°C, 30 min. reaction time, 2.5% biomass ratio and 10% KOH while it was 29.4 mol/kg biomass at 600°C, 60 min. reaction time, 2.5% biomass ratio and 20% K2CO3 and it was found to be 54.8 mol/kg biomass at 600°C, 30 min., reaction time, 2.5% biomass ratio and 30% Ru/C. Maximum gas product yield (150.8%), carbon gasification efficiency (88.1%) and hydrogen gasification efficiency (213.5%) were reached in the case of Ru/C. According to the thermodynamic model, the main gas compounds found in equilibrium condition was determined as H2, CO2, CH4 and CO. The numerical results of the model reasonably agree with the experimental data. Keywords: Biomass, fruit pulp, gasification, supercritical water, hydrogen