Thermodynamic modeling of the combined CLG–CLHG system for syngas and hydrogen generation

Abstract

The combined CLG and CLHG is a novel technology for the co‐generation of syngas and H2‐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 H2‐riched gas. In this study, the Ce‐based oxygen carrier was selected as the candidate material based on the Gibbs free energy changes (ΔG) 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 H2 was higher than 95.0% under 850–1000°C. The optimal S/C in the SR was determined as 2–3 and the H2 fraction was higher than 70.0% under 850–1000°C. In the AR, all of the Ce oxides can be regenerated to CeO2 in the air flow of 0.5 kmol at 700°C. After one CLG–CLHG cycle, there was no carbon deposition on the surface of oxygen carrier. The redox mechanism of the Ce‐based oxygen carrier was defined as: CeO2↔CeO1.83↔CeO1.72↔Ce2O3. © 2017 American Institute of Chemical Engineers Environ Prog, 37: 1132–1139, 2018

Unlocking the potential of catalysts in thermochemical energy conversion processes

“…164 Oxygen carriers can bind and release oxygen in a reversible manner and the choice of oxygen carrier depends on factors such as the operating temperature and pressure, the composition of the biomass feedstock, and the desired product yields. Monometallic materials such as copper (Cu), 165,166 Fe, 167,168 cerium (Ce), 169 Ni, 170 manganese (Mn)-based 171 oxygen carriers have been widely reported to be used in biomass chemical looping gasification. These materials have been found to be effective in providing the necessary oxygen for the gasification process and promoting the desired reactions.…”