Numerical simulation of fluidized bed reactor for calcium looping energy release process in thermochemical storage: Influence of key conditions

The thermochemical energy storage technology applied to concentrating solar power is expected to realize the large-scale deployment of solar power. Reactor design is recognized as a key challenge. In this study, the calcium looping energy release process in a bubbling fluidized bed reactor was numerically simulated using an Eulerian-Eulerian Two-fluid Model. The effects of immersed tubes, particle size, CO2 concentration, and flow velocity on the multi-physical coupling characteristics during the carbonation process were explored. The result indicated that the presence of immersed tubes improves flow characteristics and effectively controls the bed temperature. Particle size had no significant effect on the carbonation process during the kinetically controlled stage. Increasing CO2 concentration significantly enhanced the conversion rate; however, it could lead to a reduction in particle renewal frequency, thereby deteriorating the heat transfer coefficient (HTC). The study on flow velocity indicated that a balance should be struck between bed stability and reaction conversion rate, with the model identifying 0.48 m/s to 0.74 m/s as the suitable operating gas velocity. Additionally, the study compared two methods for calculating HTC and analyzed the energy utilization efficiency during the carbonation process, providing recommendations for industrial applications.