Continuous near-equilibrium operation and model validation of a pilot-scale thermochemical energy storage reactor using CaO/Ca(OH)₂

Thermochemical energy storage using the material system CaO/Ca(OH)₂ is regarded as one of the most promising technologies for application temperatures between 400 °C and 600 °C. There is still a lack of information concerning the transfer of laboratory results to industrially-relevant conditions. This study addresses this research gap and provides data for a continuously operated pilot-scale fluidized-bed storage reactor (257 mm diameter, up to 31 L fluidized bed volume, maximal 700 °C and 6 bar_g). The reactor is operated near the thermodynamic equilibrium at varying space times of the storage material (250 - 400 µm). The bed height is maintained at 390 mm during continuous operation. The results indicate good fluidization quality at steady-state operation for up to 9 h. Based on the results, a CSTR-type reactor model is proposed and validated, giving good results in predicting the fluidized bed's steady-state conversion and temperature. The model is based on material and fluidization properties, such as the fluidized beds porosity, that are measured in dependence of temperature and superficial gas velocity. The simulation results indicate that the heat transfer characteristics are crucial for adequate storage power.