Thermodynamic Modeling of the Combined CLG-CLHG System for Syngas and Hydrogen Generation

The combined CLG and CLHG is a novel technology for the co-generation of syngas and H-2-riched gas. In CLG process, the reduction of oxygen carrier with biomass can produce syngas. In CLHG process, the oxidation of oxygen carrier with steam can produce H-2-riched gas. In this study, the Ce-based oxygen carrier was selected as the candidate material based on the Gibbs free energy changes (DG) of the splitting water reactions. The redox mechanism of the Ce-based oxygen carrier was discussed and thermodynamic analysis of syngas and hydrogen generation was performed by Gibbs free energy minimization method. The optimal O/C in the GR was determined as 0.6-0.8 and the total dry concentration of CO and H-2 was higher than 95.0% under 850-1000 degrees C. The optimal S/C in the SR was determined as 2-3 and the H-2 fraction was higher than 70.0% under 850-1000 degrees C. In the AR, all of the Ce oxides can be regenerated to CeO2 in the air flow of 0.5 kmol at 700 degrees C. After one CLG-CLHG cycle, there was no carbon deposition on the surface of oxygen carrier. The redox mechanism of the Cebased oxygen carrier was defined as: CeO2 <-> CeO1.83 <-> CeO1.72 <-> Ce2O3. (C) 2017 American Institute of Chemical Engineers