Amine infused hydrogel-based CO2 gas storage technology for CO2 hydrate-based cold thermal energy storage

Abstract

Carbon dioxide (CO2) hydrate-based cold thermal energy storage (CTES) is a promising method for load shifting and demand management of cooling systems and for CO2 utilisation. A challenge of CO2 hydrate-based CTES is to find a compatible CO2 gas storage, the CO2 regeneration and absorption conditions of which can be coupled with the charging and discharging conditions of the CTES, respectively. Amine diethanolamine infused hydrogels (DEAIHs) can be an effective CO2 absorber as the gas–DEA surface contact area is greatly enlarged by infusing the solution into a hydrogel. However, the influencing factors of the CO2 absorption and regeneration performance of DEAIHs are unknown. This paper investigates the performance of DEAIHs and explores the possibility of applying them in cyclic CO2 gas storage for CTES. The effects of pressure, temperature, DEAIH sample mass and amine diethanolamine (DEA) mass fraction on CO2 absorption and absorption rate are investigated. It was found that a higher pressure prompted CO2 absorption while a temperature of 12℃ resulted in the highest CO2 absorption rate. The average CO2 absorption rates in the first 100 min were 0.250, 0.228, 0.155 and 0.033 mmol min–1 for 20-g DEAIH sample with 30-wt% DEA and 60-g DEAIH sample with 30, 47 and 89-wt% DEA, respectively. CO2 regeneration from DEAIH under zero and non-zero gauge pressures are studied. Under non-zero gauge pressures, a pressure rise followed by a pressure drop caused by CO2 re-absorption appeared in the CO2 regeneration from DEAIH. It was found for the first time that the system passed through a meta-equilibrium state before it reached an equilibrium pressure. Cyclic absorption and regeneration at 110℃ under zero gauge pressure showed that the CO2 absorption decreased dramatically after the third cycle due to the volatility of amine. Operating a coupled CO2 hydrate-based CTES and CO2 gas storage system demonstrated the possibility of DEAIH material for CO2 gas storage in CTES systems.