First Principle-based Rate Equation Theory for the Calcination Kinetics of CaCO₃ in Calcium Looping

Abstract

In this study, a first principle-based rate equation theory was developed to calculate CaCO 3 calcination kinetics in calcium looping. In density functional theory calculations for the reaction pathways of CaCO 3 , both the CaCO 3 decomposition surface reaction and structural transformation were calculated to satisfy the thermodynamic consistency. The reaction rate constant of CaCO 3 decomposition was obtained from the transition state theory (TST), which was based on the density functional theory (DFT) results and the partition function from the statistical mechanics. The surface reactions are described by a mean-field microkinetic rate equation. The nucleation of metastable CaO* to CaO crystals was considered, and a nucleation model was incorporated into the microkinetic rate equation to calculate the nucleation rate of metastable CaO* at the interface. The developed model underwent validation by employing a diverse range of experimental data at different temperatures, CO 2 partial pressures, residence times, and particle sizes.