Carbonation kinetics of calcium-based solids at the centimeter scale for moving bed applications

Abstract

Countercurrent moving bed reactors were recently proposed to capture CO2 from dispersed sources using calcium materials. Due to disparities with Calcium Looping systems in particle size and solids residence times, additional investigations are required to identify reaction controlling steps and kinetic parameters. This study examines the carbonation reaction of centimeter-scale CaO and Ca(OH)2-derived-CaO pebbles under conditions relevant to moving bed applications. To this end, the impact of carbonation temperature (450–650 °C) and CO2 concentration in the inlet gas (2.5–7.5 %v) was evaluated in TGA, employing particle sizes from 0.26 to 1.65 cm. The obtained results were fitted to a shrinking core model where the rate-determining step is CO2 diffusion through the gas volume that occupies the pores of the solid CaCO3-rich layer formed during carbonation. The experimental findings can be predicted using the effective porosity of the materials as the sole fitting parameter.