Thermodynamic modeling and analysis of hydrogen production process by biomass gasification in supercritical water

Hydrogen production by biomass gasification in supercritical water is a promising technology for utilizing high moisture content biomass. The thermodynamic models, which include chemical equilibrium, gas-liquid equilibrium, exergy and energy analysis, were established for designing and optimizing the biomass gasification process. Using the thermodynamic models, equilibrium gas yields in the reactor, gas composition in separator, and exergy and energy efficiency of gasification system were predicted. The theoretical maximum hydrogen yield and the rules of the main parametric effects on supercritical water gasification for hydrogen production were obtained by chemical equilibrium analysis. The optimal operation condition of separator considering hydrogen purity and hydrogen recovery rate was analyzed and predicted. The temperature of about 25°C and the pressure of 10-15 MPa was perfect for the separator operated under high pressure. By performing energy and exergy analysis, enhancing the heat transfer efficiency will improve the energy and exergy efficiency of the system effectively. A complete thermodynamic tool for the biomass supercritical water gasification process development and design, which is also applicable to other biomass conversion processes, was provided. This is an abstract of a paper presented at the 231st ACS National Meeting (Atlanta, GA 3/26-30/2006).