Novel Grain Model for Solid-Gas Reactions Involving Both Grain Overlapping and Sintering : Application to the Calcium Looping Process

A novel mathematical model based on the recently proposed Changing Grain Size Model (CGSM) was developed to take into account the grain size distribution, the sintering effect, and the grains overlapping phenomenon in the particle during the carbonation and calcination of pure limestone. The phenomenological model describes the diffusion, kinetics, and the change of microstructure over time. It considers the grain overlapping effect and uses population balance equations to evaluate the effect of the cycles on sintering, porosity, and surface area of the CO 2 transport material. The main novelties derived from this study are related to the verification of the high dependence of the overall conversion respect to the CO 2 partial pressure, and the prediction of the effect of the number of cycles in both calcination and carbonation processes. Approximately, an average conversion reduction of 1.35% and 5.83% per cycle was predicted for calcination and in carbonation, respectively