Second law analysis of CuCl2 hydrolysis reaction in the Cu–Cl thermochemical cycle of hydrogen production

Abstract

This article presents an exergy study of the hydrolysis reaction in the copper-chlorine thermochemical cycle for hydrogen production. It examines the reactor performance through a detailed analysis of thermal and chemical irreversibilities in the two-phase gas-solid reacting flow. A thermodynamic analysis is developed based on the flow availability and availability transfer in the spray reaction process to determine the ireversibilities of the reaction at different operating conditions. The reactor operating temperature and steam to copper chloride molar ratio, along with changes in the reaction kinetics, are considered as the critical parameters which affect the exergy efficiency of the hydrolysis reactor. The entropy generation associated with adding extra steam into the reactor and changing the reaction temperature is evaluated to assess the effectiveness of the decomposition process and the lost availability from the hydrolysis reaction. The effects from the side reaction and unreacted CuCl2 in the simulation reveal the exergy loss and resulting value of the exergy efficiency of 2.8% compared to the stoichiometry condition with a relatively high exergy efficiency of more than 75%. Such a large difference indicates the importance of analyzing real reaction conditions to provide a more reliable insight in identifying the sources of exergy losses.