Integrated operation and efficiency analysis of CaCO3/CaO in a fixed-bed reactor for thermochemical energy storage

Abstract

Calcium-based thermochemical energy storage (TCES) has attracted much attention in solar energy utilization and storage. However, the investigations of the CaCO3/CaO system are incomplete and poorly integrated at the reactor scale. In this work, a fixed-bed reactor for calcium looping (CaL) is used to conduct the integrated operation of energy storage and release. The decomposition conversion of CaCO3 in N2 at 850 °C for 8 h is 63.8% and the carbonation conversion of the corresponding decomposition product is 67.2% in CO2 at 750 °C for 4 h. The lower reactor filling increases overall thermal energy storage efficiency but decreases released energy. Furthermore, a simulation model is built to study the key operation parameters that greatly affect reactor performances. According to the orthonormal design, the high calcination temperature and porosity of 0.6–0.7 are key factors to improve both high thermal energy storage efficiency and released energy. The carbonation temperature and thermal conductivity are less important factors than decomposition temperature and porosity, which can be adjusted flexibly to meet the needs of heat utilization and cost reduction. This work provides valuable guidance for optimizing reactor operation and modifying materials to achieve high overall efficiency and released energy in fixed-bed reactors.