Thermochemical heat storage is a promising technology for improving thermal energy efficiency. To investigate the durability of the CaO/Ca(OH) 2 reaction and develop a reactivation method, repetitive charging/discharging operation of a packed bed reactor with a thick packed bed was conducted, and variations in the discharging behavior, final conversion, and reactant activity were investigated. Owing to the formation of a deactivated sintered reactant block, the discharging time halved and the final conversion ratio decreased by the 53rd discharging operation. To enhance durability, a reactivation method using high-pressure vapor was implemented during the 54th discharging operation. Following reactivation, the final conversion increased 15%, and the discharging time tripled when compared with the discharging operation before reactivation, confirming the success of this simple reactivation method.

We report the development of technology that may contribute to a reduction in greenhouse gas emissions and improve the energy efficiency of the CO 2 capture process. Lithium ortho-silicate is a suitable solid sorbent for capturing CO 2 . This reversible chemical reaction is also applicable to chemical heat storage. The absorption reaction characteristics of lithium ortho-silicate were studied by a thermogravimetric method and a volumetric method that demonstrated the influence of heat and mass transfer limitations in a packed bed designed to be as small as possible. We developed a method for measuring the absorption reaction characteristics in the experiments. In the experiments, a constant conversion fraction of 60% was observed. The reaction system was stable to repetition. The CO 2 absorption rate depends on the CO 2 pressure and reactor temperature. The absorption rate was determined at several reactor temperatures when the conversion fraction was 0.3. In this study, the maximum absorption rate was obtained at 670˚C. It was demonstrated that lithium ortho-silicate is suitable for use in a chemical heat storage system.