Modelling of the calcination behaviour of a uniformly-distributed CuO/CaCO3 particle in Ca–Cu chemical looping

Abstract

Ca–Cu chemical looping (CaL-CLC), consisting of calcination (regeneration), carbonation, and oxidation stages, is a novel process with high potential for CO2 capture. Its implementation is largely dependent on the effective matching, transferring and utilisation of the heat generated by CuO reduction, for CaCO3 decomposition, where the former is an exothermic and the latter an endothermic reaction. To better understand the calcination behaviour during CaL-CLC cycles, we developed a mathematical model coupling chemical reactions, mass and heat transfer inside a spherical particle composed of a number of uniformly distributed CuO and CaCO3 grains. Using the model, we simulated the dynamics of CuO and CaCO3 conversion, the profiles of temperature and gas concentrations, and the changes in porosity and the grain size inside the particle with time. Furthermore, the influence of several key variables on calcination behaviour within the spherical particle was numerically analysed. Results show that it is better to have an ambient temperature in the range of 1198–1223K, a similar value of the initial particle temperature, and a small CaCO3 grain size to attain a good match between reactions of CuO and CaCO3, and to avoid the onset of local superheating within the particle.