Research PaperStudy of the hydration behavior of zeolite-MgSO4 composites for long-term heat storage

- Hydration behavior of zeolite-MgSO4 composites was investigated for long-term heat storage.
- Effects of various operation conditions on the hydration performance were revealed.
- The hydration enhancement of composites depended on zeolite properties.
- The hydration ability of composites decreased when the air temperature was above 50 °C.
- The tested composite showed a good cycling stability.

Hydration behavior of composite adsorbents based on porous zeolite matrix and MgSO4 hydrates was investigated experimentally for long-term heat storage. The composites were prepared by the infiltration method, and different zeolites were tested. Water sorption of composites in a constant temperature & humidity chamber was carried out first, and then the hydration of composites in a macro-scale reactor was performed. Special efforts were devoted to reveal the effects of various reaction conditions including temperature, relative humidity (RH) and air flow rate on the hydration performance of composites. The results showed that the prepared zeolite-MgSO4 composites had larger hydration ability than pure zeolites, and zeolite 13X-MgSO4 showed the best performance. Both the saturation adsorption amount and the hydration rate could be effectively increased by increasing the RH or the air temperature. However, the hydration ability of composites decreased significantly when the air temperature was above 50 °C. The air temperature lift during the reactor heat discharge was found to increase with the flow rate or RH of fed moist air. Besides, the reactor filled with the zeolite-MgSO4 composites showed a high energy efficiency of 81.34% and a good cyclic stability.