The 10th Asian Symposium on Computational Heat Transfer and Fluid Flow ( ASCHT2025)

 The calcium looping (CaL) process holds significant potential for third-generation concentrated solar power (CSP) applications. As a critical component, the reaction rate of the calciner directly affects the system's overall power generation efficiency. Traditional CaL-CSP systems use solar calciner, but limitations such as low solar radiation absorption by CaCO₃/CaO and heat radiative losses reduce reaction rates. This study proposes an embedded tube calciner utilizing supercritical carbon dioxide (sCO₂) as the heat transfer fluid, which achieves an average reaction rate 2.25 times higher than that of conventional solar calciner. Numerical simulations based on this new calciner design are conducted to investigate the effects of various operating conditions and physical parameters on the conversion rate under non-uniform heat flux boundary conditions. The results show that the maximum conversion rate occurs with an initial porosity of 0.5, an sCO₂ inlet temperature of 900 °C, a thermal conductivity of 3 W/(m·K), and an sCO₂ inlet velocity of 15 m/s. Among these factors, the inlet temperature and velocity of sCO₂ have the greatest influence on the conversion rate, while thermal conductivity and initial porosity have secondary effects. Additionally, due to the lower temperature at the sCO₂ outlet, the temperature and conversion rate of calcium-based materials at the top of the calciner remain relatively low. This study provides valuable insights for optimizing calciner operation and design to enhance overall efficiency.
 

Thermochemical energy storage,CaCO3/CaO,Non-uniform heat flux,variable porosity,Calciner with sCO2 heated