Exergy analysis on the process for three reactors chemical looping hydrogen generation

Three reactors chemical looping (TRCL) is a promising hydrogen production process without needing H-2 purification and capturing CO2 directly. Based on the deficient research on the energy conversion mechanism in TRCL and the role of external heat sources in the TRCL process, this paper studied the thermodynamic characteristics of energy conversion in methane-TRCL and syngas-TRCL and water-gas shift (WGS) systems, and established the mathematical model of the related parameters through the concept of energy grade. Meanwhile, in this system the energy grade effects of input heat, heat quantity, hydrogen concentration in syngas and steam quantity on the thermodynamic performance are studied. The results show that the TRCL system of methane and syngas has the highest exergy efficiency with 89% and 88.3% respectively, while the energy grade of external input heat is 0.694. Under mentioned above, methane-TRCL is suitable for the case where the heat input value is greater than 310.52 kJ/mol, and the syngas-TRCL system is more efficient than WGS system with 4.8%. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.