Determination of Kinetic and Diffusion Parameters Needed to Predict the Behavior of CaO-Based CO2 Sorbent and Sorbent-Catalyst Materials

For about 10 years, this research group has developed and utilized a particle grain model (PGM), to simulate CO2-capture carried out by CaO-based porous particles. Chemical kinetics and diffusion parameters were either taken from literature studies or fixed by fitting experimental sorption data. As recently observed, this procedure was not fully satisfactory and revealed systematic, minor discrepancies between PGM numerical results and experimental data when predicting sorbents behavior during the initial chemically controlled regime of carbonation. This work deals with the experimental determination of kinetic and diffusion parameters, utilized in the PGM, by means of straightforward thermogravimetric analysis (TGA) tests on small samples of materials to be evaluated for CO2 sorption and sorption-enhanced processes. To validate this procedure, the carbonation of two Ni–CaO–mayenite combined sorbent-catalyst materials (CSCMs) was studied in TGA. The experimental data so obtained were used to infer carbonation kinetic parameters tailored for each CSCM, which resulted to be compatible with investigated phenomena and previously proposed values, and allowed faithful PGM predictions at different operating temperatures. These parameters were then implemented in an axial dispersion plug flow reactor model for sorption enhanced steam methane reforming (SESMR): its predictions resulted in good agreement with experimental data from SESMR tests performed in packed beds.