Study on coupling characteristics of thermal-fluid-chemical multi-physics field in CaCO3/CaO thermochemical exothermic reactor

Thermochemical heat storage has advantages such as high energy storage density, low energy loss, and long storage durations, making it highly promising for development. The CaCO3/CaO system is used as an energy storage material due to its high energy storage density, high reaction temperature, low cost, easy availability, and safety. Although some studies have addressed the stability and absorbability of energy storage materials, there is still a lack of research on the numerical simulation of the multi-physics field coupling in the CaCO3/CaO system. Therefore, this study investigates the thermal-fluid-chemical coupling characteristics of the CaCO3/CaO thermochemical exothermic reactor. An exothermic reactor model is established to accurately describe the CaO carbonatation process. The variation patterns of temperature and conversion rate during the carbonatation process are studied, as well as the influence of thermal conductivity, temperature, and total carbon dioxide pressure on the carbonatation process of the reactor. Furthermore, a reactor model with cooling channels is developed, and the variations in temperature and reaction field inside the reactor are examined. The results show that considering the flow of carbon dioxide has a significant impact on the reactor performance, with a 16.23 % difference in reaction rate compared to not considering the flow. Considering carbon dioxide flow is more in line with the actual situation. Therefore, the influence of carbon dioxide flow should be taken into account in the simulation. Increasing the thermal conductivity of the reaction bed from 1.33 W/m.K to 4 W/m.K improves the carbonation reaction rate by 60.26 %. Increasing the total carbon dioxide pressure from 1 bar to 3 bar enhances the carbonation reaction rate by 59.36 %. Conversely, raising the initial temperature of the reactor inhibits the carbonation reaction. Compared to the reactor without the optimized structure, the reactor with cooling channels exhibits a 34.94 % increase in reaction rate.